Sexual selection accounts for the geographic reversal of sexual size dimorphism in the dung fly, sepsis punctum (Diptera: Sepsidae).

PubMed

Puniamoorthy, Nalini; Schäfer, Martin A; Blanckenhorn, Wolf U

2012-07-01

Sexual size dimorphism (SSD) varies widely across and within species. The differential equilibrium model of SSD explains dimorphism as the evolutionary outcome of consistent differences in natural and sexual selection between the sexes. Here, we comprehensively examine a unique cross-continental reversal in SSD in the dung fly, Sepsis punctum. Using common garden laboratory experiments, we establish that SSD is male-biased in Europe and female-biased in North America. When estimating sexual (pairing success) and fecundity selection (clutch size of female partner) on males under three operational sex ratios (OSRs), we find that the intensity of sexual selection is significantly stronger in European versus North American populations, increasing with male body size and OSR in the former only. Fecundity selection on female body size also increases strongly with egg number and weakly with egg volume, however, equally on both continents. Finally, viability selection on body size in terms of intrinsic (physiological) adult life span in the laboratory is overall nil and does not vary significantly across all seven populations. Although it is impossible to prove causality, our results confirm the differential equilibrium model of SSD in that differences in sexual selection intensity account for the reversal in SSD in European versus North American populations, presumably mediating the ongoing speciation process in S. punctum. © 2012 The Author(s).

Eye movements in pedophiles: automatic and controlled attentional processes while viewing prepubescent stimuli.

PubMed

Fromberger, Peter; Jordan, Kirsten; Steinkrauss, Henrike; von Herder, Jakob; Stolpmann, Georg; Kröner-Herwig, Birgit; Müller, Jürgen Leo

2013-05-01

Recent theories in sexuality highlight the importance of automatic and controlled attentional processes in viewing sexually relevant stimuli. The model of Spiering and Everaerd (2007) assumes that sexually relevant features of a stimulus are preattentively selected and automatically induce focal attention to these sexually relevant aspects. Whether this assumption proves true for pedophiles is unknown. It is aim of this study to test this assumption empirically for people suffering from pedophilic interests. Twenty-two pedophiles, 8 nonpedophilic forensic controls, and 52 healthy controls simultaneously viewed the picture of a child and the picture of an adult while eye movements were measured. Entry time was assessed as a measure of automatic attentional processes and relative fixation time in order to assess controlled attentional processes. Pedophiles demonstrated significantly shorter entry time to child stimuli than to adult stimuli. The opposite was the case for nonpedophiles, as they showed longer relative fixation time for adult stimuli, and, against all expectations, pedophiles also demonstrated longer relative fixation time for adult stimuli. The results confirmed the hypothesis that pedophiles automatically selected sexually relevant stimuli (children). Contrary to all expectations, this automatic selection did not trigger the focal attention to these sexually relevant pictures. Furthermore, pedophiles were first and longest attracted by faces and pubic regions of children; nonpedophiles were first and longest attracted by faces and breasts of adults. The results demonstrated, for the first time, that the face and pubic region are the most attracting regions in children for pedophiles. © 2013 American Psychological Association

On the unfitness of natural selection to explain sexual reproduction, and the difficulties that remain.

PubMed

van Rossum, Joris

2006-01-01

In its essence, the explanatory potential of the theory of natural selection is based on the iterative process of random production and variation, and subsequent non-random, directive selection. It is shown that within this explanatory framework, there is no place for the explanation of sexual reproduction. Thus in Darwinistic literature, sexual reproduction - one of nature's most salient characteristics - is often either assumed or ignored, but not explained. This fundamental and challenging gap within a complete naturalistic understanding of living beings calls for the need of a cybernetic account for sexual reproduction, meaning an understanding of the dynamic and creative potential of living beings to continuously and autonomously produce new organisms with unique and specific constellations.

Sexual segregation in North American elk: the role of density dependence

PubMed Central

Stewart, Kelley M; Walsh, Danielle R; Kie, John G; Dick, Brian L; Bowyer, R Terry

2015-01-01

We investigated how density-dependent processes and subsequent variation in nutritional condition of individuals influenced both timing and duration of sexual segregation and selection of resources. During 1999–2001, we experimentally created two population densities of North American elk (Cervus elaphus), a high-density population at 20 elk/km2, and a low-density population at 4 elk/km2 to test hypotheses relative to timing and duration of sexual segregation and variation in selection of resources. We used multi-response permutation procedures to investigate patterns of sexual segregation, and resource selection functions to document differences in selection of resources by individuals in high- and low-density populations during sexual segregation and aggregation. The duration of sexual segregation was 2 months longer in the high-density population and likely was influenced by individuals in poorer nutritional condition, which corresponded with later conception and parturition, than at low density. Males and females in the high-density population overlapped in selection of resources to a greater extent than in the low-density population, probably resulting from density-dependent effects of increased intraspecific competition and lower availability of resources. PMID:25691992

Sexual selection and physical attractiveness : Implications for mating dynamics.

PubMed

Gangestad, S W

1993-09-01

Sexual selection processes have received much attention in recent years, attention reflected in interest in human mate preferences. Among these mate preferences are preferences for physical attractiveness. Preferences in and of themselves, however, do not fully explain the nature of the relationships that individuals attain. A tacit negotiation process underlies relationship formation and maintenance. The notion that preferences for physical attractiveness evolved under parasite-driven "good genes" sexual selection leads to predictions about the nature of trade-offs that individuals make between mates' physical attractiveness and investment potential. These predictions and relevant data are explored, with a primary emphasis on women's preferences for men's qualities. In addition, further implications of trade-offs are examined, most notably (a) the impact of environmental variations on the nature of mating and (b) some effects of trade-offs on infidelity and male attempts to control women.

The handicap process favors exaggerated, rather than reduced, sexual ornaments.

PubMed

Tazzyman, Samuel J; Iwasa, Yoh; Pomiankowski, Andrew

2014-09-01

Why are traits that function as secondary sexual ornaments generally exaggerated in size compared to the naturally selected optimum, and not reduced? Because they deviate from the naturally selected optimum, traits that are reduced in size will handicap their bearer, and could thus provide an honest signal of quality to a potential mate. Thus if secondary sexual ornaments evolve via the handicap process, current theory suggests that reduced ornamentation should be as frequent as exaggerated ornamentation, but this is not the case. To try to explain this discrepancy, we analyze a simple model of the handicap process. Our analysis shows that asymmetries in costs of preference or ornament with regard to exaggeration and reduction cannot fully explain the imbalance. Rather, the bias toward exaggeration can be best explained if either the signaling efficacy or the condition dependence of a trait increases with size. Under these circumstances, evolution always leads to more extreme exaggeration than reduction: although the two should occur just as frequently, exaggerated secondary sexual ornaments are likely to be further removed from the naturally selected optimum than reduced ornaments. © 2014 The Authors. Evolution published by Wiley Periodicals, Inc. on behalf of The Society for the Study of Evolution.

Sexual orientation data collection and progress toward Healthy People 2010.

PubMed

Sell, R L; Becker, J B

2001-06-01

Without scientifically obtained data and published reports, it is difficult to raise awareness and acquire adequate resources to address the health concerns of lesbian, gay, and bisexual Americans. The Department of Health and Human Services must recognize gaps in its information systems regarding sexual orientation data and take immediate steps to monitor and eliminate health disparities as delineated in Healthy People 2010. A paper supported by funding from the Office of the Assistant Secretary for Planning and Evaluation explores these concerns and suggests that the department (1) create work groups to examine the collection of sexual orientation data; (2) create a set of guiding principles to govern the process of selecting standard definitions and measures; (3) recognize that racial/ethnic, immigrant-status, age, socioeconomic, and geographic differences must be taken into account when standard measures of sexual orientation are selected; (4) select a minimum set of standard sexual orientation measures; and (5) develop a long-range strategic plan for the collection of sexual orientation data.

Sexual orientation data collection and progress toward Healthy People 2010.

PubMed Central

Sell, R L; Becker, J B

2001-01-01

Without scientifically obtained data and published reports, it is difficult to raise awareness and acquire adequate resources to address the health concerns of lesbian, gay, and bisexual Americans. The Department of Health and Human Services must recognize gaps in its information systems regarding sexual orientation data and take immediate steps to monitor and eliminate health disparities as delineated in Healthy People 2010. A paper supported by funding from the Office of the Assistant Secretary for Planning and Evaluation explores these concerns and suggests that the department (1) create work groups to examine the collection of sexual orientation data; (2) create a set of guiding principles to govern the process of selecting standard definitions and measures; (3) recognize that racial/ethnic, immigrant-status, age, socioeconomic, and geographic differences must be taken into account when standard measures of sexual orientation are selected; (4) select a minimum set of standard sexual orientation measures; and (5) develop a long-range strategic plan for the collection of sexual orientation data. PMID:11392926

Synergistic selection between ecological niche and mate preference primes diversification.

PubMed

Boughman, Janette W; Svanbäck, Richard

2017-01-01

The ecological niche and mate preferences have independently been shown to be important for the process of speciation. Here, we articulate a novel mechanism by which ecological niche use and mate preference can be linked to promote speciation. The degree to which individual niches are narrow and clustered affects the strength of divergent natural selection and population splitting. Similarly, the degree to which individual mate preferences are narrow and clustered affects the strength of divergent sexual selection and assortative mating between diverging forms. This novel perspective is inspired by the literature on ecological niches; it also explores mate preferences and how they may contribute to speciation. Unlike much comparative work, we do not search for evolutionary patterns using proxies for adaptation and sexual selection, but rather we elucidate how ideas from niche theory relate to mate preference, and how this relationship can foster speciation. Recognizing that individual and population niches are conceptually and ecologically linked to individual and population mate preference functions will significantly increase our understanding of rapid evolutionary diversification in nature. It has potential to help solve the difficult challenge of testing the role of sexual selection in the speciation process. We also identify ecological factors that are likely to affect individual niche and individual mate preference in synergistic ways and as a consequence to promote speciation. The ecological niche an individual occupies can directly affect its mate preference. Clusters of individuals with narrow, differentiated niches are likely to have narrow, differentiated mate preference functions. Our approach integrates ecological and sexual selection research to further our understanding of diversification processes. Such integration may be necessary for progress because these processes seem inextricably linked in the natural world. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

The association between testosterone, sexual arousal, and selective attention for erotic stimuli in men.

PubMed

Alexander, G M; Sherwin, B B

1991-09-01

Twenty-six, eugonadal men between the ages of 18 and 27 participated in this investigation of the relationship between sexual arousal, testosterone (T) levels, and the processing of sexual information. At each of the two test sessions, subjects gave a blood sample, listened to an erotic or neutral priming audiotape, and completed a dichotic listening task designed to assess selective attention for sexual stimuli. Subjective levels of sexual arousal to the audiotape and sexual attitudes and sexual experience were assessed by self-report measures. Contrary to our hypothesis, there was no relationship between levels of free T and the strength of the selective attention bias for sexual stimuli. However, men who were more distracted by the sexual material in the task reported higher levels of sexual arousal to erotic imagery than men who were less distracted by the sexual material in the task (P less than 0.01). Moreover, men who were more sexually aroused by the erotic audiotape made significantly less shadowing errors in the erotic prime condition then they did during the neutral prime condition (P less than 0.05). There was a negative association between T and shadowing errors in the erotic prime condition (P less than 0.05). These results suggest that lower thresholds for sexual arousal are associated with a greater bias to attend to sexual information and that T may have effects on cognitive-motivational aspects of sexual behavior by enhancing attention to relevant stimuli.

Aesthetic evolution by mate choice: Darwin's really dangerous idea.

PubMed

Prum, Richard O

2012-08-19

Darwin proposed an explicitly aesthetic theory of sexual selection in which he described mate preferences as a 'taste for the beautiful', an 'aesthetic capacity', etc. These statements were not merely colourful Victorian mannerisms, but explicit expressions of Darwin's hypothesis that mate preferences can evolve for arbitrarily attractive traits that do not provide any additional benefits to mate choice. In his critique of Darwin, A. R. Wallace proposed an entirely modern mechanism of mate preference evolution through the correlation of display traits with male vigour or viability, but he called this mechanism natural selection. Wallace's honest advertisement proposal was stridently anti-Darwinian and anti-aesthetic. Most modern sexual selection research relies on essentially the same Neo-Wallacean theory renamed as sexual selection. I define the process of aesthetic evolution as the evolution of a communication signal through sensory/cognitive evaluation, which is most elaborated through coevolution of the signal and its evaluation. Sensory evaluation includes the possibility that display traits do not encode information that is being assessed, but are merely preferred. A genuinely Darwinian, aesthetic theory of sexual selection requires the incorporation of the Lande-Kirkpatrick null model into sexual selection research, but also encompasses the possibility of sensory bias, good genes and direct benefits mechanisms.

Mate choice theory and the mode of selection in sexual populations.

PubMed

Carson, Hampton L

2003-05-27

Indirect new data imply that mate and/or gamete choice are major selective forces driving genetic change in sexual populations. The system dictates nonrandom mating, an evolutionary process requiring both revised genetic theory and new data on heritability of characters underlying Darwinian fitness. Successfully reproducing individuals represent rare selections from among vigorous, competing survivors of preadult natural selection. Nonrandom mating has correlated demographic effects: reduced effective population size, inbreeding, low gene flow, and emphasis on deme structure. Characters involved in choice behavior at reproduction appear based on quantitative trait loci. This variability serves selection for fitness within the population, having only an incidental relationship to the origin of genetically based reproductive isolation between populations. The claim that extensive hybridization experiments with Drosophila indicate that selection favors a gradual progression of "isolating mechanisms" is flawed, because intra-group random mating is assumed. Over deep time, local sexual populations are strong, independent genetic systems that use rich fields of variable polygenic components of fitness. The sexual reproduction system thus particularizes, in small subspecific populations, the genetic basis of the grand adaptive sweep of selective evolutionary change, much as Darwin proposed.

Sexually antagonistic selection on genetic variation underlying both male and female same-sex sexual behavior.

PubMed

Berger, David; You, Tao; Minano, Maravillas R; Grieshop, Karl; Lind, Martin I; Arnqvist, Göran; Maklakov, Alexei A

2016-05-13

Intralocus sexual conflict, arising from selection for different alleles at the same locus in males and females, imposes a constraint on sex-specific adaptation. Intralocus sexual conflict can be alleviated by the evolution of sex-limited genetic architectures and phenotypic expression, but pleiotropic constraints may hinder this process. Here, we explored putative intralocus sexual conflict and genetic (co)variance in a poorly understood behavior with near male-limited expression. Same-sex sexual behaviors (SSBs) generally do not conform to classic evolutionary models of adaptation but are common in male animals and have been hypothesized to result from perception errors and selection for high male mating rates. However, perspectives incorporating sex-specific selection on genes shared by males and females to explain the expression and evolution of SSBs have largely been neglected. We performed two parallel sex-limited artificial selection experiments on SSB in male and female seed beetles, followed by sex-specific assays of locomotor activity and male sex recognition (two traits hypothesized to be functionally related to SSB) and adult reproductive success (allowing us to assess fitness consequences of genetic variance in SSB and its correlated components). Our experiments reveal both shared and sex-limited genetic variance for SSB. Strikingly, genetically correlated responses in locomotor activity and male sex-recognition were associated with sexually antagonistic fitness effects, but these effects differed qualitatively between male and female selection lines, implicating intralocus sexual conflict at both male- and female-specific genetic components underlying SSB. Our study provides experimental support for the hypothesis that widespread pleiotropy generates pervasive intralocus sexual conflict governing the expression of SSBs, suggesting that SSB in one sex can occur due to the expression of genes that carry benefits in the other sex.

Sex-linked genomic variation and its relationship to avian plumage dichromatism and sexual selection.

PubMed

Huang, Huateng; Rabosky, Daniel L

2015-09-16

Sexual dichromatism is the tendency for sexes to differ in color pattern and represents a striking form of within-species morphological variation. Conspicuous intersexual differences in avian plumage are generally thought to result from Darwinian sexual selection, to the extent that dichromatism is often treated as a surrogate for the intensity of sexual selection in phylogenetic comparative studies. Intense sexual selection is predicted to leave a footprint on genetic evolution by reducing the relative genetic diversity on sex chromosome to that on the autosomes. In this study, we test the association between plumage dichromatism and sex-linked genetic diversity using eight species pairs with contrasting levels of dichromatism. We estimated Z-linked and autosomal genetic diversity for these non-model avian species using restriction-site associated (RAD) loci that covered ~3 % of the genome. We find that monochromatic birds consistently have reduced sex-linked genomic variation relative to phylogenetically-paired dichromatic species and this pattern is robust to mutational biases. Our results are consistent with several interpretations. If present-day sexual selection is stronger in dichromatic birds, our results suggest that its impact on sex-linked genomic variation is offset by other processes that lead to proportionately lower Z-linked variation in monochromatic species. We discuss possible factors that may contribute to this discrepancy between phenotypes and genomic variation. Conversely, it is possible that present-day sexual selection -- as measured by the variance in male reproductive success -- is stronger in the set of monochromatic taxa we have examined, potentially reflecting the importance of song, behavior and other non-plumage associated traits as targets of sexual selection. This counterintuitive finding suggests that the relationship between genomic variation and sexual selection is complex and highlights the need for a more comprehensive survey of genomic variation in avian taxa that vary markedly in social and genetic mating systems.

Female mating preferences determine system-level evolution in a gene network model.

PubMed

Fierst, Janna L

2013-06-01

Environmental patterns of directional, stabilizing and fluctuating selection can influence the evolution of system-level properties like evolvability and mutational robustness. Intersexual selection produces strong phenotypic selection and these dynamics may also affect the response to mutation and the potential for future adaptation. In order to to assess the influence of mating preferences on these evolutionary properties, I modeled a male trait and female preference determined by separate gene regulatory networks. I studied three sexual selection scenarios: sexual conflict, a Gaussian model of the Fisher process described in Lande (in Proc Natl Acad Sci 78(6):3721-3725, 1981) and a good genes model in which the male trait signalled his mutational condition. I measured the effects these mating preferences had on the potential for traits and preferences to evolve towards new states, and mutational robustness of both the phenotype and the individual's overall viability. All types of sexual selection increased male phenotypic robustness relative to a randomly mating population. The Fisher model also reduced male evolvability and mutational robustness for viability. Under good genes sexual selection, males evolved an increased mutational robustness for viability. Females choosing their mates is a scenario that is sufficient to create selective forces that impact genetic evolution and shape the evolutionary response to mutation and environmental selection. These dynamics will inevitably develop in any population where sexual selection is operating, and affect the potential for future adaptation.

Family feuds: social competition and sexual conflict in complex societies.

PubMed

Rubenstein, Dustin R

2012-08-19

Darwin was initially puzzled by the processes that led to ornamentation in males-what he termed sexual selection-and those that led to extreme cooperation and altruism in complex animal societies-what was later termed kin selection. Here, I explore the relationships between sexual and kin selection theory by examining how social competition for reproductive opportunities-particularly in females-and sexual conflict over mating partners are inherent and critical parts of complex altruistic societies. I argue that (i) patterns of reproductive sharing within complex societies can drive levels of social competition and reproductive conflict not only in males but also in females living in social groups, and ultimately the evolution of female traits such as ornaments and armaments; (ii) mating conflict over female choice of sexual partners can influence kin structure within groups and drive the evolution of complex societies; and (iii) patterns of reproductive sharing and conflict among females may also drive the evolution of complex societies by influencing kin structure within groups. Ultimately, complex societies exhibiting altruistic behaviour appear to have only arisen in taxa where social competition over reproductive opportunities and sexual conflict over mating partners were low. Once such societies evolved, there were important selective feedbacks on traits used to regulate and mediate intra-sexual competition over reproductive opportunities, particularly in females.

Neutral and selection-driven decay of sexual traits in asexual stick insects

PubMed Central

Schwander, Tanja; Crespi, Bernard J.; Gries, Regine; Gries, Gerhard

2013-01-01

Environmental shifts and lifestyle changes may result in formerly adaptive traits becoming non-functional or maladaptive. The subsequent decay of such traits highlights the importance of natural selection for adaptations, yet its causes have rarely been investigated. To study the fate of formerly adaptive traits after lifestyle changes, we evaluated sexual traits in five independently derived asexual lineages, including traits that are specific to males and therefore not exposed to selection. At least four of the asexual lineages retained the capacity to produce males that display normal courtship behaviours and are able to fertilize eggs of females from related sexual species. The maintenance of male traits may stem from pleiotropy, or from these traits only regressing via drift, which may require millions of years to generate phenotypic effects. By contrast, we found parallel decay of sexual traits in females. Asexual females produced altered airborne and contact signals, had modified sperm storage organs, and lost the ability to fertilize their eggs, impeding reversals to sexual reproduction. Female sexual traits were decayed even in recently derived asexuals, suggesting that trait changes following the evolution of asexuality, when they occur, proceed rapidly and are driven by selective processes rather than drift. PMID:23782880

Eggspot number and sexual selection in the cichlid fish Astatotilapia burtoni.

PubMed

Henning, Frederico; Meyer, Axel

2012-01-01

Sexual selection on male coloration is one of the main mechanisms proposed to explain the explosive speciation rates in East African cichlid fish. True eggspots are color patterns characteristic of the most species-rich lineage of cichlids, the Haplochromini, and have been suggested to be causally related to the speciation processes. Eggspots are thought to have originated by sensory exploitation and subsequently gained several roles in sexual advertisement. However, for most of these functions the evidence is equivocal. In addition, the genetic architecture of this trait still is largely unknown. We conducted bidirectional selective breeding experiments for eggspot numbers in the model cichlid, Astatotilapia burtoni. After two generations, low lines responded significantly, whereas the high lines did not. Body size was both phenotypically and genotypically correlated with eggspot number and showed correlated response to selection. Males with higher numbers of eggspots were found to sire larger offspring. Despite the potential to act as honest indicators of fitness, the behavioral experiments showed no evidence of a role in either intra- or inter-sexual selection. Visual-based female preference was instead explained by courtship intensity. The evolution of this trait has been interpreted in light of adaptive theories of sexual selection, however the present and published results suggest the influence of non-adaptive factors such as sensory exploitation, environmental constraints and sexual antagonism.

Neural pathways in processing of sexual arousal: a dynamic causal modeling study.

PubMed

Seok, J-W; Park, M-S; Sohn, J-H

2016-09-01

Three decades of research have investigated brain processing of visual sexual stimuli with neuroimaging methods. These researchers have found that sexual arousal stimuli elicit activity in a broad neural network of cortical and subcortical brain areas that are known to be associated with cognitive, emotional, motivational and physiological components. However, it is not completely understood how these neural systems integrate and modulated incoming information. Therefore, we identify cerebral areas whose activations were correlated with sexual arousal using event-related functional magnetic resonance imaging and used the dynamic causal modeling method for searching the effective connectivity about the sexual arousal processing network. Thirteen heterosexual males were scanned while they passively viewed alternating short trials of erotic and neutral pictures on a monitor. We created a subset of seven models based on our results and previous studies and selected a dominant connectivity model. Consequently, we suggest a dynamic causal model of the brain processes mediating the cognitive, emotional, motivational and physiological factors of human male sexual arousal. These findings are significant implications for the neuropsychology of male sexuality.

Genetic correlations and sex-specific adaptation in changing environments.

PubMed

Connallon, Tim; Hall, Matthew D

2016-10-01

Females and males have conflicting evolutionary interests. Selection favors the evolution of different phenotypes within each sex, yet divergence between the sexes is constrained by the shared genetic basis of female and male traits. Current theory predicts that such "sexual antagonism" should be common: manifesting rapidly during the process of adaptation, and slow in its resolution. However, these predictions apply in temporally stable environments. Environmental change has been shown empirically to realign the direction of selection acting on shared traits and thereby alleviate signals of sexually antagonistic selection. Yet there remains no theory for how common sexual antagonism should be in changing environments. Here, we analyze models of sex-specific evolutionary divergence under directional and cyclic environmental change, and consider the impact of genetic correlations on long-run patterns of sex-specific adaptation. We find that environmental change often aligns directional selection between the sexes, even when they have divergent phenotypic optima. Nevertheless, some forms of environmental change generate persistent sexually antagonistic selection that is difficult to resolve. Our results reinforce recent empirical observations that changing environmental conditions alleviate conflict between males and females. They also generate new predictions regarding the scope for sexually antagonistic selection and its resolution in changing environments. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

Aesthetic evolution by mate choice: Darwin's really dangerous idea

PubMed Central

Prum, Richard O.

2012-01-01

Darwin proposed an explicitly aesthetic theory of sexual selection in which he described mate preferences as a ‘taste for the beautiful’, an ‘aesthetic capacity’, etc. These statements were not merely colourful Victorian mannerisms, but explicit expressions of Darwin's hypothesis that mate preferences can evolve for arbitrarily attractive traits that do not provide any additional benefits to mate choice. In his critique of Darwin, A. R. Wallace proposed an entirely modern mechanism of mate preference evolution through the correlation of display traits with male vigour or viability, but he called this mechanism natural selection. Wallace's honest advertisement proposal was stridently anti-Darwinian and anti-aesthetic. Most modern sexual selection research relies on essentially the same Neo-Wallacean theory renamed as sexual selection. I define the process of aesthetic evolution as the evolution of a communication signal through sensory/cognitive evaluation, which is most elaborated through coevolution of the signal and its evaluation. Sensory evaluation includes the possibility that display traits do not encode information that is being assessed, but are merely preferred. A genuinely Darwinian, aesthetic theory of sexual selection requires the incorporation of the Lande–Kirkpatrick null model into sexual selection research, but also encompasses the possibility of sensory bias, good genes and direct benefits mechanisms. PMID:22777014

Runaway sexual selection leads to good genes.

PubMed

Chandler, Christopher H; Ofria, Charles; Dworkin, Ian

2013-01-01

Mate choice and sexual displays are widespread in nature, but their evolutionary benefits remain controversial. Theory predicts these traits can be favored by runaway sexual selection, in which preference and display reinforce one another due to genetic correlation; or by good genes benefits, in which mate choice is advantageous because extreme displays indicate a well-adapted genotype. However, these hypotheses are not mutually exclusive, and the adaptive benefits underlying mate choice can themselves evolve. In particular, examining how and why sexual displays become indicators of good genes is challenging in natural systems. Here, we use experimental evolution in "digital organisms" to demonstrate the origins of condition-dependent indicator displays following their spread due to a runaway process. Surprisingly, handicap-like costs are not necessary for displays to become indicators of male viability. Instead, a pleiotropic genetic architecture underlies both displays and viability. Runaway sexual selection and good genes benefits should thus be viewed as interacting mechanisms that reinforce one another. © 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.

Fluctuating environments, sexual selection and the evolution of flexible mate choice in birds.

PubMed

Botero, Carlos A; Rubenstein, Dustin R

2012-01-01

Environmentally-induced fluctuation in the form and strength of natural selection can drive the evolution of morphology, physiology, and behavior. Here we test the idea that fluctuating climatic conditions may also influence the process of sexual selection by inducing unexpected reversals in the relative quality or sexual attractiveness of potential breeding partners. Although this phenomenon, known as 'ecological cross-over', has been documented in a variety of species, it remains unclear the extent to which it has driven the evolution of major interspecific differences in reproductive behavior. We show that after controlling for potentially influential life history and demographic variables, there are significant positive associations between the variability and predictability of annual climatic cycles and the prevalence of infidelity and divorce within populations of a taxonomically diverse array of socially monogamous birds. Our results are consistent with the hypothesis that environmental factors have shaped the evolution of reproductive flexibility and suggest that in the absence of severe time constraints, secondary mate choice behaviors can help prevent, correct, or minimize the negative consequences of ecological cross-overs. Our findings also illustrate how a basic evolutionary process like sexual selection is susceptible to the increasing variability and unpredictability of climatic conditions that is resulting from climate change.

Genome-wide association study (GWAS) for growth rate and age at sexual maturation in Atlantic salmon (Salmo salar).

PubMed

Gutierrez, Alejandro P; Yáñez, José M; Fukui, Steve; Swift, Bruce; Davidson, William S

2015-01-01

Early sexual maturation is considered a serious drawback for Atlantic salmon aquaculture as it retards growth, increases production times and affects flesh quality. Although both growth and sexual maturation are thought to be complex processes controlled by several genetic and environmental factors, selection for these traits has been continuously accomplished since the beginning of Atlantic salmon selective breeding programs. In this genome-wide association study (GWAS) we used a 6.5K single-nucleotide polymorphism (SNP) array to genotype ∼ 480 individuals from the Cermaq Canada broodstock program and search for SNPs associated with growth and age at sexual maturation. Using a mixed model approach we identified markers showing a significant association with growth, grilsing (early sexual maturation) and late sexual maturation. The most significant associations were found for grilsing, with markers located in Ssa10, Ssa02, Ssa13, Ssa25 and Ssa12, and for late maturation with markers located in Ssa28, Ssa01 and Ssa21. A lower level of association was detected with growth on Ssa13. Candidate genes, which were linked to these genetic markers, were identified and some of them show a direct relationship with developmental processes, especially for those in association with sexual maturation. However, the relatively low power to detect genetic markers associated with growth (days to 5 kg) in this GWAS indicates the need to use a higher density SNP array in order to overcome the low levels of linkage disequilibrium observed in Atlantic salmon before the information can be incorporated into a selective breeding program.

Male-male competition, female mate choice and their interaction: determining total sexual selection.

PubMed

Hunt, John; Breuker, Casper J; Sadowski, Jennifer A; Moore, Allen J

2009-01-01

Empirical studies of sexual selection typically focus on one of the two mechanisms of sexual selection without integrating these into a description of total sexual selection, or study total sexual selection without quantifying the contributions of all of the mechanisms of sexual selection. However, this can provide an incomplete or misleading view of how sexually selected traits evolve if the mechanisms of sexual selection are opposing or differ in form. Here, we take a two-fold approach to advocate a direction for future studies of sexual selection. We first show how a quantitative partitioning and examination of sexual selection mechanisms can inform by identifying illustrative studies that describe both male-male competition and female mate choice acting on the same trait. In our sample, the most common trait where this occurred was body size, and selection was typically linear. We found that male-male competition and female mate choice can be reinforcing or opposing, although the former is most common in the literature. The mechanisms of sexual selection can occur simultaneously or sequentially, and we found they were more likely to be opposing when the mechanisms operated sequentially. The degree and timing that these mechanisms interact have important implications for the operation of sexual selection and needs to be considered in designing studies. Our examples highlight where empirical data are needed. We especially lack standardized measures of the form and strength of selection imposed by each mechanism of sexual selection and how they combine to determine total sexual selection. Secondly, using quantitative genetic principles, we outline how the selection imposed by individual mechanisms can be measured and combined to estimate the total strength and form of sexual selection. We discuss the evolutionary consequences of combining the mechanisms of sexual selection and interpreting total sexual selection. We suggest how this approach may result in empirical progress in the field of sexual selection.

Quantifying male attractiveness.

PubMed Central

McNamara, John M; Houston, Alasdair I; Marques Dos Santos, Miguel; Kokko, Hanna; Brooks, Rob

2003-01-01

Genetic models of sexual selection are concerned with a dynamic process in which female preference and male trait values coevolve. We present a rigorous method for characterizing evolutionary endpoints of this process in phenotypic terms. In our phenotypic characterization the mate-choice strategy of female population members determines how attractive females should find each male, and a population is evolutionarily stable if population members are actually behaving in this way. This provides a justification of phenotypic explanations of sexual selection and the insights into sexual selection that they provide. Furthermore, the phenotypic approach also has enormous advantages over a genetic approach when computing evolutionarily stable mate-choice strategies, especially when strategies are allowed to be complex time-dependent preference rules. For simplicity and clarity our analysis deals with haploid mate-choice genetics and a male trait that is inherited phenotypically, for example by vertical cultural transmission. The method is, however, easily extendible to other cases. An example illustrates that the sexy son phenomenon can occur when there is phenotypic inheritance of the male trait. PMID:14561306

EVOLUTION OF DIVERGENT FEMALE MATING PREFERENCE IN RESPONSE TO EXPERIMENTAL SEXUAL SELECTION

PubMed Central

Debelle, Allan; Ritchie, Michael G; Snook, Rhonda R

2014-01-01

Sexual selection is predicted to drive the coevolution of mating signals and preferences (mating traits) within populations, and could play a role in speciation if sexual isolation arises due to mating trait divergence between populations. However, few studies have demonstrated that differences in mating traits between populations result from sexual selection alone. Experimental evolution is a promising approach to directly examine the action of sexual selection on mating trait divergence among populations. We manipulated the opportunity for sexual selection (low vs. high) in populations of Drosophila pseudoobscura. Previous studies on these experimental populations have shown that sexual selection manipulation resulted in the divergence between sexual selection treatments of several courtship song parameters, including interpulse interval (IPI) which markedly influences male mating success. Here, we measure female preference for IPI using a playback design to test for preference divergence between the sexual selection treatments after 130 generations of experimental sexual selection. The results suggest that female preference has coevolved with male signal, in opposite directions between the sexual selection treatments, providing direct evidence of the ability of sexual selection to drive the divergent coevolution of mating traits between populations. We discuss the implications in the context sexual selection and speciation. PMID:24931497

How sexual selection can drive the evolution of costly sperm ornamentation

NASA Astrophysics Data System (ADS)

Lüpold, Stefan; Manier, Mollie K.; Puniamoorthy, Nalini; Schoff, Christopher; Starmer, William T.; Luepold, Shannon H. Buckley; Belote, John M.; Pitnick, Scott

2016-05-01

Post-copulatory sexual selection (PSS), fuelled by female promiscuity, is credited with the rapid evolution of sperm quality traits across diverse taxa. Yet, our understanding of the adaptive significance of sperm ornaments and the cryptic female preferences driving their evolution is extremely limited. Here we review the evolutionary allometry of exaggerated sexual traits (for example, antlers, horns, tail feathers, mandibles and dewlaps), show that the giant sperm of some Drosophila species are possibly the most extreme ornaments in all of nature and demonstrate how their existence challenges theories explaining the intensity of sexual selection, mating-system evolution and the fundamental nature of sex differences. We also combine quantitative genetic analyses of interacting sex-specific traits in D. melanogaster with comparative analyses of the condition dependence of male and female reproductive potential across species with varying ornament size to reveal complex dynamics that may underlie sperm-length evolution. Our results suggest that producing few gigantic sperm evolved by (1) Fisherian runaway selection mediated by genetic correlations between sperm length, the female preference for long sperm and female mating frequency, and (2) longer sperm increasing the indirect benefits to females. Our results also suggest that the developmental integration of sperm quality and quantity renders post-copulatory sexual selection on ejaculates unlikely to treat male-male competition and female choice as discrete processes.

Sexual dimorphism in bite performance drives morphological variation in chameleons.

PubMed

da Silva, Jessica M; Herrel, Anthony; Measey, G John; Tolley, Krystal A

2014-01-01

Phenotypic performance in different environments is central to understanding the evolutionary and ecological processes that drive adaptive divergence and, ultimately, speciation. Because habitat structure can affect an animal's foraging behaviour, anti-predator defences, and communication behaviour, it can influence both natural and sexual selection pressures. These selective pressures, in turn, act upon morphological traits to maximize an animal's performance. For performance traits involved in both social and ecological activities, such as bite force, natural and sexual selection often interact in complex ways, providing an opportunity to understand the adaptive significance of morphological variation with respect to habitat. Dwarf chameleons within the Bradypodion melanocephalum-Bradypodion thamnobates species complex have multiple phenotypic forms, each with a specific head morphology that could reflect its use of either open- or closed-canopy habitats. To determine whether these morphological differences represent adaptations to their habitats, we tested for differences in both absolute and relative bite performance. Only absolute differences were found between forms, with the closed-canopy forms biting harder than their open-canopy counterparts. In contrast, sexual dimorphism was found for both absolute and relative bite force, but the relative differences were limited to the closed-canopy forms. These results indicate that both natural and sexual selection are acting within both habitat types, but to varying degrees. Sexual selection seems to be the predominant force within the closed-canopy habitats, which are more protected from aerial predators, enabling chameleons to invest more in ornamentation for communication. In contrast, natural selection is likely to be the predominant force in the open-canopy habitats, inhibiting the development of conspicuous secondary sexual characteristics and, ultimately, enforcing their overall diminutive body size and constraining performance.

Sexual Dimorphism in Bite Performance Drives Morphological Variation in Chameleons

PubMed Central

da Silva, Jessica M.; Herrel, Anthony; Measey, G. John; Tolley, Krystal A.

2014-01-01

Phenotypic performance in different environments is central to understanding the evolutionary and ecological processes that drive adaptive divergence and, ultimately, speciation. Because habitat structure can affect an animal’s foraging behaviour, anti-predator defences, and communication behaviour, it can influence both natural and sexual selection pressures. These selective pressures, in turn, act upon morphological traits to maximize an animal’s performance. For performance traits involved in both social and ecological activities, such as bite force, natural and sexual selection often interact in complex ways, providing an opportunity to understand the adaptive significance of morphological variation with respect to habitat. Dwarf chameleons within the Bradypodion melanocephalum-Bradypodion thamnobates species complex have multiple phenotypic forms, each with a specific head morphology that could reflect its use of either open- or closed-canopy habitats. To determine whether these morphological differences represent adaptations to their habitats, we tested for differences in both absolute and relative bite performance. Only absolute differences were found between forms, with the closed-canopy forms biting harder than their open-canopy counterparts. In contrast, sexual dimorphism was found for both absolute and relative bite force, but the relative differences were limited to the closed-canopy forms. These results indicate that both natural and sexual selection are acting within both habitat types, but to varying degrees. Sexual selection seems to be the predominant force within the closed-canopy habitats, which are more protected from aerial predators, enabling chameleons to invest more in ornamentation for communication. In contrast, natural selection is likely to be the predominant force in the open-canopy habitats, inhibiting the development of conspicuous secondary sexual characteristics and, ultimately, enforcing their overall diminutive body size and constraining performance. PMID:24475183

The effects of alcohol intoxication on young adult women's identification of risk for sexual assault: A systematic review.

PubMed

Melkonian, Alexander J; Ham, Lindsay S

2018-03-01

Alcohol-related sexual assault among young adult women continues to present a public health concern. Social information-processing theory provides an organizing framework for understanding how alcohol intoxication can impair the processing of sexual assault risk cues and behavioral responding in sexual assault scenarios. The aim of the present article was to systematically review the extant research on the effects of alcohol intoxication on sexual assault risk information processing among young adult women. We selected relevant research through a systematic search of scientific databases, using key words related to young adult women, alcohol intoxication, and risk recognition, resulting in 14 independent research samples meeting all criteria. Studies used a variety of methods and dependent measures, precluding quantitative analysis of results. Thirteen of the 14 studies identified report at least partial support for intoxication impairing the attention to cues, interpretation of social information, or intended behavioral response in a hypothetical sexual assault scenario. Given some mixed findings, further research is warranted to identify contextual and individual differences related to risk detection and intended responding and to fully test other aspects of social information processing. Results have implications for improving alcohol-related sexual assault prevention programs by addressing the impact of alcohol intoxication on processing sexual assault risk information. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Family feuds: social competition and sexual conflict in complex societies

PubMed Central

Rubenstein, Dustin R.

2012-01-01

Darwin was initially puzzled by the processes that led to ornamentation in males—what he termed sexual selection—and those that led to extreme cooperation and altruism in complex animal societies—what was later termed kin selection. Here, I explore the relationships between sexual and kin selection theory by examining how social competition for reproductive opportunities—particularly in females—and sexual conflict over mating partners are inherent and critical parts of complex altruistic societies. I argue that (i) patterns of reproductive sharing within complex societies can drive levels of social competition and reproductive conflict not only in males but also in females living in social groups, and ultimately the evolution of female traits such as ornaments and armaments; (ii) mating conflict over female choice of sexual partners can influence kin structure within groups and drive the evolution of complex societies; and (iii) patterns of reproductive sharing and conflict among females may also drive the evolution of complex societies by influencing kin structure within groups. Ultimately, complex societies exhibiting altruistic behaviour appear to have only arisen in taxa where social competition over reproductive opportunities and sexual conflict over mating partners were low. Once such societies evolved, there were important selective feedbacks on traits used to regulate and mediate intra-sexual competition over reproductive opportunities, particularly in females. PMID:22777018

Correlation between investment in sexual traits and valve sexual dimorphism in Cyprideis species (Ostracoda)

PubMed Central

Hunt, Gene; Lockwood, Rowan; Swaddle, John P.; Horne, David J.

2017-01-01

Assessing the long-term macroevolutionary consequences of sexual selection has been hampered by the difficulty of studying this process in the fossil record. Cytheroid ostracodes offer an excellent system to explore sexual selection in the fossil record because their readily fossilized carapaces are sexually dimorphic. Specifically, males are relatively more elongate than females in this superfamily. This sexual shape difference is thought to arise so that males carapaces can accommodate their very large copulatory apparatus, which can account for up to one-third of body volume. Here we test this widely held explanation for sexual dimorphism in cytheroid ostracodes by correlating investment in male genitalia, a trait in which sexual selection is seen as the main evolutionary driver, with sexual dimorphism of carapace in the genus Cyprideis. We analyzed specimens collected in the field (C. salebrosa, USA; C. torosa, UK) and from collections of the National Museum of Natural History, Washington, DC (C. mexicana). We digitized valve outlines in lateral view to obtain measures of size (valve area) and shape (elongation, measured as length to height ratio), and obtained several dimensions from two components of the hemipenis: the muscular basal capsule, which functions as a sperm pump, and the section that includes the intromittent organ (terminal extension). In addition to the assessment of this primary sexual trait, we also quantified two dimensions of the male secondary sexual trait—where the transformed right walking leg functions as a clasping organ during mating. We also measured linear dimensions from four limbs as indicators of overall (soft-part) body size, and assessed allometry of the soft anatomy. We observed significant correlations in males between valve size, but not elongation, and distinct structural parts of the hemipenis, even after accounting for their shared correlation with overall body size. We also found weak but significant positive correlation between valve elongation and the degree of sexual dimorphism of the walking leg, but only in C. torosa. The correlation between the hemipenis parts, especially basal capsule size and male valve size dimorphism suggests that sexual selection on sperm size, quantity, and/or efficiency of transfer may drive sexual size dimorphism in these species, although we cannot exclude other aspects of sexual and natural selection. PMID:28678866

Evolution of divergent female mating preference in response to experimental sexual selection.

PubMed

Debelle, Allan; Ritchie, Michael G; Snook, Rhonda R

2014-09-01

Sexual selection is predicted to drive the coevolution of mating signals and preferences (mating traits) within populations, and could play a role in speciation if sexual isolation arises due to mating trait divergence between populations. However, few studies have demonstrated that differences in mating traits between populations result from sexual selection alone. Experimental evolution is a promising approach to directly examine the action of sexual selection on mating trait divergence among populations. We manipulated the opportunity for sexual selection (low vs. high) in populations of Drosophila pseudoobscura. Previous studies on these experimental populations have shown that sexual selection manipulation resulted in the divergence between sexual selection treatments of several courtship song parameters, including interpulse interval (IPI) which markedly influences male mating success. Here, we measure female preference for IPI using a playback design to test for preference divergence between the sexual selection treatments after 130 generations of experimental sexual selection. The results suggest that female preference has coevolved with male signal, in opposite directions between the sexual selection treatments, providing direct evidence of the ability of sexual selection to drive the divergent coevolution of mating traits between populations. We discuss the implications in the context sexual selection and speciation. © 2014 The Authors. Evolution published by Wiley Periodicals, Inc. on behalf of The Society for the Study of Evolution.

The sexual cascade and the rise of pre-ejaculatory (Darwinian) sexual selection, sex roles, and sexual conflict.

PubMed

Parker, Geoff A

2014-08-21

After brief historic overviews of sexual selection and sexual conflict, I argue that pre-ejaculatory sexual selection (the form of sexual selection discussed by Darwin) arose at a late stage in an inevitable succession of transitions flowing from the early evolution of syngamy to the evolution of copulation and sex roles. If certain conditions were met, this "sexual cascade" progressed inevitably, if not, sexual strategy remained fixed at a given stage. Prolonged evolutionary history of intense sperm competition/selection under external fertilization preceded the rise of advanced mobility, which generated pre-ejaculatory sexual selection, followed on land by internal fertilization and reduced sperm competition in the form of postcopulatory sexual selection. I develop a prospective model of the early evolution of mobility, which, as Darwin realized, was the catalyst for pre-ejaculatory sexual selection. Stages in the cascade should be regarded as consequential rather than separate phenomena and, as such, invalidate much current opposition to Darwin-Bateman sex roles. Potential for sexual conflict occurs throughout, greatly increasing later in the cascade, reaching its peak under precopulatory sexual selection when sex roles become highly differentiated. Copyright © 2014 Cold Spring Harbor Laboratory Press; all rights reserved.

The Sexual Cascade and the Rise of Pre-Ejaculatory (Darwinian) Sexual Selection, Sex Roles, and Sexual Conflict

PubMed Central

Parker, Geoff A.

2014-01-01

After brief historic overviews of sexual selection and sexual conflict, I argue that pre-ejaculatory sexual selection (the form of sexual selection discussed by Darwin) arose at a late stage in an inevitable succession of transitions flowing from the early evolution of syngamy to the evolution of copulation and sex roles. If certain conditions were met, this “sexual cascade” progressed inevitably, if not, sexual strategy remained fixed at a given stage. Prolonged evolutionary history of intense sperm competition/selection under external fertilization preceded the rise of advanced mobility, which generated pre-ejaculatory sexual selection, followed on land by internal fertilization and reduced sperm competition in the form of postcopulatory sexual selection. I develop a prospective model of the early evolution of mobility, which, as Darwin realized, was the catalyst for pre-ejaculatory sexual selection. Stages in the cascade should be regarded as consequential rather than separate phenomena and, as such, invalidate much current opposition to Darwin–Bateman sex roles. Potential for sexual conflict occurs throughout, greatly increasing later in the cascade, reaching its peak under precopulatory sexual selection when sex roles become highly differentiated. PMID:25147177

Contributions of natural and sexual selection to the evolution of premating reproductive isolation: a research agenda.

PubMed

Safran, Rebecca J; Scordato, Elizabeth S C; Symes, Laurel B; Rodríguez, Rafael L; Mendelson, Tamra C

2013-11-01

Speciation by divergent natural selection is well supported. However, the role of sexual selection in speciation is less well understood due to disagreement about whether sexual selection is a mechanism of evolution separate from natural selection, as well as confusion about various models and tests of sexual selection. Here, we outline how sexual selection and natural selection are different mechanisms of evolutionary change, and suggest that this distinction is critical when analyzing the role of sexual selection in speciation. Furthermore, we clarify models of sexual selection with respect to their interaction with ecology and natural selection. In doing so, we outline a research agenda for testing hypotheses about the relative significance of divergent sexual and natural selection in the evolution of reproductive isolation. Copyright © 2013 Elsevier Ltd. All rights reserved.

The effect of sexual selection on adaptation and extinction under increasing temperatures.

PubMed

Parrett, Jonathan M; Knell, Robert J

2018-04-25

Strong sexual selection has been reported to both enhance and hinder the adaptive capacity and persistence of populations when exposed to novel environments. Consequently, how sexual selection influences population adaption and persistence under stress remains widely debated. Here, we present two empirical investigations of the fitness consequences of sexual selection on populations of the Indian meal moth, Plodia interpunctella, exposed to stable or gradually increasing temperatures. When faced with increasing temperatures, strong sexual selection was associated with both increased fecundity and offspring survival compared with populations experiencing weak sexual selection, suggesting sexual selection acts to drive adaptive evolution by favouring beneficial alleles. Strong sexual selection did not, however, delay extinction when the temperature became excessively high. By manipulating individuals' mating opportunities during fitness assays, we were able to assess the effect of multiple mating independently from the effect of population-level sexual selection, and found that polyandry has a positive effect on both fecundity and offspring survival under increasing temperatures in those populations evolving with weak sexual selection. Within stable temperatures, there were some benefits from strong sexual selection but these were not consistent across the entire experiment, possibly reflecting changing costs and benefits of sexual selection under stabilizing and directional selection. These results indicate that sexual selection can provide a buffer against climate change and increase adaptation rates within a continuously changing environment. These positive effects of sexual selection may, however, be too small to protect populations and delay extinction when environmental changes are relatively rapid. © 2018 The Author(s).

Signal trait sexual dimorphism and mutual sexual selection in Drosophila serrata.

PubMed

Chenoweth, Stephen F; Blows, Mark W

2003-10-01

The evolution of sexual dimorphism may occur when natural and sexual selection result in different optimum trait values for males and females. Perhaps the most prominent examples of sexual dimorphism occur in sexually selected traits, for which males usually display exaggerated trait levels, while females may show reduced expression of the trait. In some species, females also exhibit secondary sexual traits that may either be a consequence of a correlated response to sexual selection on males or direct sexual selection for female secondary sexual traits. In this experiment, we simultaneously measure the intersex genetic correlations and the relative strength of sexual selection on males and females for a set of cuticular hydrocarbons in Drosophila serrata. There was significant directional sexual selection on both male and female cuticular hydrocarbons: the strength of sexual selection did not differ among the sexes but males and females preferred different cuticular hydrocarbons. In contrast with many previous studies of sexual dimorphism, intersex genetic correlations were low. The evolution of sexual dimorphism in D. serrata appears to have been achieved by sex-limited expression of traits controlled by genes on the X chromosome and is likely to be in its final stages.

Female song is widespread and ancestral in songbirds.

PubMed

Odom, Karan J; Hall, Michelle L; Riebel, Katharina; Omland, Kevin E; Langmore, Naomi E

2014-03-04

Bird song has historically been considered an almost exclusively male trait, an observation fundamental to the formulation of Darwin's theory of sexual selection. Like other male ornaments, song is used by male songbirds to attract females and compete with rivals. Thus, bird song has become a textbook example of the power of sexual selection to lead to extreme neurological and behavioural sex differences. Here we present an extensive survey and ancestral state reconstruction of female song across songbirds showing that female song is present in 71% of surveyed species including 32 families, and that females sang in the common ancestor of modern songbirds. Our results reverse classical assumptions about the evolution of song and sex differences in birds. The challenge now is to identify whether sexual selection alone or broader processes, such as social or natural selection, best explain the evolution of elaborate traits in both sexes.

Darwin and sexual selection: One hundred years of misunderstanding.

PubMed

Veuille, Michel

2010-02-01

Darwin's book on the Descent of Man and Selection in Relation to Sex (1871) is often viewed as the continuation of The Origin of Species published 12 years earlier (1859), both because of the implicit parallelism between natural selection and sexual selection, and because Darwin himself presents the book as developing a subject (man) which he intentionally omitted in the Origin. But the Descent can also be viewed as the continuation of his book on Variation published three years earlier (1868). Firstly because Darwin's hypothesis of pangenesis links the selection process to the origin of variation through use and disuse, an idea underlying his speculations on the origin of moral sense in humans. Second because like the action of the horticulturist on his domestic crops, sexual selection exerted by one sex on the other sex can develop fancy traits that are not easily accounted for by their utility to the selected organism itself, such as artistic taste, pride, courage, and the morphological differences between human populations. These traits are difficult to reconcile with pangenesis. They add up to other contradictions of the book possibly resulting from Darwin's erroneous inference about the mechanism of inheritance, like those on the determination of sex-ratio, or the confusion between individual adaptation and the advantage to the species. These inconsistencies inaugurate a weakening of the Darwinian message, which will last 50 years after his death. They contributed to the neglect of sexual selection for a century. Darwin however maintained a logical distinction between evolutionary mechanisms and hereditary mechanisms, and an epistemological distinction between evolutionary theory and Pangenesis hypothesis. In the modern context of Mendelian genetics, Darwin's sexual selection retrospectively appears as luminous an idea in its pure principle as natural selection, even though the mechanisms governing the evolution of sexual choice in animals remain largely unresolved. 2009 Académie des sciences. Published by Elsevier SAS. All rights reserved.

The Psychosexual Profile of Sexual Assistants: An Internet-Based Explorative Study

PubMed Central

Limoncin, Erika; Galli, Debora; Ciocca, Giacomo; Gravina, Giovanni Luca; Carosa, Eleonora; Mollaioli, Daniele; Lenzi, Andrea; Jannini, Emmanuele A.

2014-01-01

Introduction Sexual assistance may have some aspects that resemble prostitution and others that might lead one to think of sexual assistants as similar to a group of subjects whose sexual object is disability (devotees). In this study, we investigate whether a rigorous selection and training process on the part of specialised organisations may reduce the risk of training subjects with an atypical sexual interest and behaviours resembling prostitution. Materials and Methods The study population consisted of 152 subjects defining themselves as sexual assistants. Subjects were initially contacted on websites specifically dedicated to sexual assistants and prostitutes. One hundred and twenty subjects were selected, by propensity score analysis, and studied by means of a modified version of a semi-structured questionnaire previously developed to investigate a population of subjects attracted by disability. Results The study group was composed of 80 trained and 40 untrained sexual assistants, with mean ages of 41.5 (SD +/−12.58) and 44.5 (SD +/−11.62), respectively. A significant number of untrained subjects affirmed that their motivation in carrying out sexual assistance was of a remunerative nature, while this number was lower among the trained assistants (p = 0.001). Nearly all untrained subjects claimed to do one or more of the following activities during sexual assistance: sexual intercourse, oral sex, and masturbation. Among the trained subjects, however, only 47.5% claimed to do one or more of these activities, which means that there is a significant gap between trained and untrained assistants (p<0.0001). The existence of an atypical sexual interest was more evident between untrained rather than between trained subjects (p<0.0001). Conclusions Sexual assistance represents a way through which people affected by disabilities may attain the right to explore their sexuality in a safe setting. This can be guaranteed only if sexual assistants are trained and carefully selected by specialised organisations. PMID:24919176

The complex interplay of sex allocation and sexual selection.

PubMed

Booksmythe, Isobel; Schwanz, Lisa E; Kokko, Hanna

2013-03-01

It is well recognized that sex allocation strategies can be influenced by sexual selection, when females adjust offspring sex ratios in response to their mates' attractiveness. Yet the reciprocal influence of strategic sex allocation on processes of sexual selection has only recently been revealed. Recent theoretical work demonstrates that sex allocation weakens selection for female preferences, leading to the decline of male traits. However, these results have been derived assuming that females have perfect knowledge of mate attractiveness and precise control over cost-free allocation. Relaxing these assumptions highlights the importance of another feedback: that adaptive sex allocation must become difficult to maintain as traits and preferences decline. When sex allocation strategies erode not only traits and preferences but also their own selective advantage, predictions can no longer be expressed as a simple linear correlation between ornament exaggeration and adaptive sex allocation. Instead, strongest sex ratio biases may be found at intermediate trait levels. © 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.

Homage to Bateman: sex roles predict sex differences in sexual selection.

PubMed

Fritzsche, Karoline; Arnqvis, Göran

2013-07-01

Classic sex role theory predicts that sexual selection should be stronger in males in taxa showing conventional sex roles and stronger in females in role reversed mating systems. To test this very central prediction and to assess the utility of different measures of sexual selection, we estimated sexual selection in both sexes in four seed beetle species with divergent sex roles using a novel experimental design. We found that sexual selection was sizeable in females and the strength of sexual selection was similar in females and males in role-reversed species. Sexual selection was overall significantly stronger in males than in females and residual selection formed a substantial component of net selection in both sexes. Furthermore, sexual selection in females was stronger in role-reversed species compared to species with conventional sex roles. Variance-based measures of sexual selection (the Bateman gradient and selection opportunities) were better predictors of sexual dimorphism in reproductive behavior and morphology across species compared to trait-based measures (selection differentials). Our results highlight the importance of using assays that incorporate components of fitness manifested after mating. We suggest that the Bateman gradient is generally the most informative measure of the strength of sexual selection in comparisons across sexes and/or species. © 2013 The Author(s). Evolution © 2013 The Society for the Study of Evolution.

Sexual selection drives evolution and rapid turnover of male gene expression.

PubMed

Harrison, Peter W; Wright, Alison E; Zimmer, Fabian; Dean, Rebecca; Montgomery, Stephen H; Pointer, Marie A; Mank, Judith E

2015-04-07

The profound and pervasive differences in gene expression observed between males and females, and the unique evolutionary properties of these genes in many species, have led to the widespread assumption that they are the product of sexual selection and sexual conflict. However, we still lack a clear understanding of the connection between sexual selection and transcriptional dimorphism, often termed sex-biased gene expression. Moreover, the relative contribution of sexual selection vs. drift in shaping broad patterns of expression, divergence, and polymorphism remains unknown. To assess the role of sexual selection in shaping these patterns, we assembled transcriptomes from an avian clade representing the full range of sexual dimorphism and sexual selection. We use these species to test the links between sexual selection and sex-biased gene expression evolution in a comparative framework. Through ancestral reconstruction of sex bias, we demonstrate a rapid turnover of sex bias across this clade driven by sexual selection and show it to be primarily the result of expression changes in males. We use phylogenetically controlled comparative methods to demonstrate that phenotypic measures of sexual selection predict the proportion of male-biased but not female-biased gene expression. Although male-biased genes show elevated rates of coding sequence evolution, consistent with previous reports in a range of taxa, there is no association between sexual selection and rates of coding sequence evolution, suggesting that expression changes may be more important than coding sequence in sexual selection. Taken together, our results highlight the power of sexual selection to act on gene expression differences and shape genome evolution.

Fitness consequences of sex-specific selection.

PubMed

Connallon, Tim; Cox, Robert M; Calsbeek, Ryan

2010-06-01

Theory suggests that sex-specific selection can facilitate adaptation in sexually reproducing populations. However, sexual conflict theory and recent experiments indicate that sex-specific selection is potentially costly due to sexual antagonism: alleles harmful to one sex can accumulate within a population because they are favored in the other sex. Whether sex-specific selection provides a net fitness benefit or cost depends, in part, on the relative frequency and strength of sexually concordant versus sexually antagonistic selection throughout a species' genome. Here, we model the net fitness consequences of sex-specific selection while explicitly considering both sexually concordant and sexually antagonistic selection. The model shows that, even when sexual antagonism is rare, the fitness costs that it imposes will generally overwhelm fitness benefits of sexually concordant selection. Furthermore, the cost of sexual antagonism is, at best, only partially resolved by the evolution of sex-limited gene expression. To evaluate the key parameters of the model, we analyze an extensive dataset of sex-specific selection gradients from wild populations, along with data from the experimental evolution literature. The model and data imply that sex-specific selection may likely impose a net cost on sexually reproducing species, although additional research will be required to confirm this conclusion.

Ecology, sexual selection and speciation.

PubMed

Maan, Martine E; Seehausen, Ole

2011-06-01

The spectacular diversity in sexually selected traits among animal taxa has inspired the hypothesis that divergent sexual selection can drive speciation. Unfortunately, speciation biologists often consider sexual selection in isolation from natural selection, even though sexually selected traits evolve in an ecological context: both preferences and traits are often subject to natural selection. Conversely, while behavioural ecologists may address ecological effects on sexual communication, they rarely measure the consequences for population divergence. Herein, we review the empirical literature addressing the mechanisms by which natural selection and sexual selection can interact during speciation. We find that convincing evidence for any of these scenarios is thin. However, the available data strongly support various diversifying effects that emerge from interactions between sexual selection and environmental heterogeneity. We suggest that evaluating the evolutionary consequences of these effects requires a better integration of behavioural, ecological and evolutionary research. © 2011 Blackwell Publishing Ltd/CNRS.

Post-copulatory sexual selection and sexual conflict in the evolution of male pregnancy.

PubMed

Paczolt, Kimberly A; Jones, Adam G

2010-03-18

Male pregnancy in seahorses, pipefishes and sea dragons (family Syngnathidae) represents a striking reproductive adaptation that has shaped the evolution of behaviour and morphology in this group of fishes. In many syngnathid species, males brood their offspring in a specialized pouch, which presumably evolved to facilitate male parental care. However, an unexplored possibility is that brood pouch evolution was partly shaped by parent-offspring or sexual conflict, processes that would result in trade-offs between current and future pregnancies. Here we report a controlled breeding experiment using the sexually dimorphic Gulf pipefish, Syngnathus scovelli, to test for post-copulatory sexual selection within broods and for trade-offs between successive male pregnancies as functions of female attractiveness. Offspring survivorship within a pregnancy was affected by the size of a male's mate, the number of eggs transferred and the male's sexual responsiveness. Significantly, we also found that embryo survivorship in a current pregnancy was negatively related to survivorship in the prior pregnancy, clearly demonstrating fitness trade-offs between broods. Overall, our data indicate that post-copulatory sexual selection and sexual conflict occur in Gulf pipefishes. The conflict seems to be mediated by a strategy of cryptic choice in which males increase rates of offspring abortion in pregnancies from unattractive mothers to retain resources for future reproductive opportunities. Hence, the male brood pouch of syngnathid fishes, which nurtures offspring, also seems to have an important role as an arbiter of conflict between the sexes.

Polyandry as a mediator of sexual selection before and after mating

PubMed Central

Kvarnemo, Charlotta; Simmons, Leigh W.

2013-01-01

The Darwin–Bateman paradigm recognizes competition among males for access to multiple mates as the main driver of sexual selection. Increasingly, however, females are also being found to benefit from multiple mating so that polyandry can generate competition among females for access to multiple males, and impose sexual selection on female traits that influence their mating success. Polyandry can reduce a male's ability to monopolize females, and thus weaken male focused sexual selection. Perhaps the most important effect of polyandry on males arises because of sperm competition and cryptic female choice. Polyandry favours increased male ejaculate expenditure that can affect sexual selection on males by reducing their potential reproductive rate. Moreover, sexual selection after mating can ameliorate or exaggerate sexual selection before mating. Currently, estimates of sexual selection intensity rely heavily on measures of male mating success, but polyandry now raises serious questions over the validity of such approaches. Future work must take into account both pre- and post-copulatory episodes of selection. A change in focus from the products of sexual selection expected in males, to less obvious traits in females, such as sensory perception, is likely to reveal a greater role of sexual selection in female evolution. PMID:23339234

Polyandry as a mediator of sexual selection before and after mating.

PubMed

Kvarnemo, Charlotta; Simmons, Leigh W

2013-03-05

The Darwin-Bateman paradigm recognizes competition among males for access to multiple mates as the main driver of sexual selection. Increasingly, however, females are also being found to benefit from multiple mating so that polyandry can generate competition among females for access to multiple males, and impose sexual selection on female traits that influence their mating success. Polyandry can reduce a male's ability to monopolize females, and thus weaken male focused sexual selection. Perhaps the most important effect of polyandry on males arises because of sperm competition and cryptic female choice. Polyandry favours increased male ejaculate expenditure that can affect sexual selection on males by reducing their potential reproductive rate. Moreover, sexual selection after mating can ameliorate or exaggerate sexual selection before mating. Currently, estimates of sexual selection intensity rely heavily on measures of male mating success, but polyandry now raises serious questions over the validity of such approaches. Future work must take into account both pre- and post-copulatory episodes of selection. A change in focus from the products of sexual selection expected in males, to less obvious traits in females, such as sensory perception, is likely to reveal a greater role of sexual selection in female evolution.

Constrained evolution of the sex comb in Drosophila simulans.

PubMed

Maraqa, M S; Griffin, R; Sharma, M D; Wilson, A J; Hunt, J; Hosken, D J; House, C M

2017-02-01

Male fitness is dependent on sexual traits that influence mate acquisition (precopulatory sexual selection) and paternity (post-copulatory sexual selection), and although many studies have documented the form of selection in one or the other of these arenas, fewer have done it for both. Nonetheless, it appears that the dominant form of sexual selection is directional, although theoretically, populations should converge on peaks in the fitness surface, where selection is stabilizing. Many factors, however, can prevent populations from reaching adaptive peaks. Genetic constraints can be important if they prevent the development of highest fitness phenotypes, as can the direction of selection if it reverses across episodes of selection. In this study, we examine the evidence that these processes influence the evolution of the multivariate sex comb morphology of male Drosophila simulans. To do this, we conduct a quantitative genetic study together with a multivariate selection analysis to infer how the genetic architecture and selection interact. We find abundant genetic variance and covariance in elements of the sex comb. However, there was little evidence for directional selection in either arena. Significant nonlinear selection was detected prior to copulation when males were mated to nonvirgin females, and post-copulation during sperm offence (again with males mated to nonvirgins). Thus, contrary to our predictions, the evolution of the D. simulans sex comb is limited neither by genetic constraints nor by antagonistic selection between pre- and post-copulatory arenas, but nonlinear selection on the multivariate phenotype may prevent sex combs from evolving to reach some fitness maximizing optima. © 2016 The Authors. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

Experimental evolution of a sexually selected display in yeast

PubMed Central

Rogers, David W.; Greig, Duncan

2008-01-01

The fundamental principle underlying sexual selection theory is that an allele conferring an advantage in the competition for mates will spread through a population. Remarkably, this has never been demonstrated empirically. We have developed an experimental system using yeast for testing genetic models of sexual selection. Yeast signal to potential partners by producing an attractive pheromone; stronger signallers are preferred as mates. We tested the effect of high and low levels of sexual selection on the evolution of a gene determining the strength of this signal. Under high sexual selection, an allele encoding a stronger signal was able to invade a population of weak signallers, and we observed a corresponding increase in the amount of pheromone produced. By contrast, the strong signalling allele failed to invade under low sexual selection. Our results demonstrate, for the first time, the spread of a sexually selected allele through a population, confirming the central assumption of sexual selection theory. Our yeast system is a powerful tool for investigating the genetics of sexual selection. PMID:18842545

c-fos is induced in the hippocampus during consolidation of sexual imprinting in the zebra finch (Taeniopygia guttata).

PubMed

Sadananda, Monika; Bischof, Hans-Joachim

2004-01-01

c-fos was used to mark regions of enhanced neuronal activity during sexual imprinting, an early learning process by which information about the prospective sexual partner is acquired and consolidated. In the present study, we demonstrate that the hippocampus, already known for its specialized spatial memory capacities in navigating pigeons and in food-storing birds, depicts a selective differential c-fos induction in a situation shown to lead to sexual imprinting, that is, exposing previously isolated male birds to a female for 1 h. c-fos induction is lateralized, the left hippocampus showing more c-fos activity than the right. Our results would indicate a role for the hippocampus in the consolidation process of imprinting, probably in the transfer of information to the other telencephalic areas that show alterations in synaptic connectivity as a result of consolidation of sexual imprinting.

On cultural transformations of sexuality and gender in recent decades

PubMed Central

Sigusch, Volkmar

2004-01-01

Western cultures have witnessed a tremendous cultural and social transformation of sexuality in the years since the sexual revolution. Apart from a few public debates and scandals, the process has moved along gradually and quietly. Yet its real and symbolic effects are probably much more consequential than those generated by the sexual revolution of the sixties. Sigusch refers to the broad-based recoding and reassessment of the sexual sphere during the eighties and nineties as the "neosexual revolution". The neosexual revolution is dismantling the old patterns of sexuality and reassembling them anew. In the process, dimensions, intimate relationships, preferences and sexual fragments emerge, many of which had submerged, were unnamed or simply did not exist before. In general, sexuality has lost much of its symbolic meaning as a cultural phenomenon. Sexuality is no longer the great metaphor for pleasure and happiness, nor is it so greatly overestimated as it was during the sexual revolution. It is now widely taken for granted, much like egotism or motility. Whereas sex was once mystified in a positive sense - as ecstasy and transgression, it has now taken on a negative mystification characterized by abuse, violence and deadly infection. While the old sexuality was based primarily upon sexual instinct, orgasm and the heterosexual couple, neosexualities revolve predominantly around gender difference, thrills, self-gratification and prosthetic substitution. From the vast number of interrelated processes from which neosexualities emerge, three empirically observable phenomena have been selected for discussion here: the dissociation of the sexual sphere, the dispersion of sexual fragments and the diversification of intimate relationships. The outcome of the neosexual revolution may be described as "lean sexuality" and "self-sex". PMID:19675690

On cultural transformations of sexuality and gender in recent decades.

PubMed

Sigusch, Volkmar

2004-10-20

Western cultures have witnessed a tremendous cultural and social transformation of sexuality in the years since the sexual revolution. Apart from a few public debates and scandals, the process has moved along gradually and quietly. Yet its real and symbolic effects are probably much more consequential than those generated by the sexual revolution of the sixties. Sigusch refers to the broad-based recoding and reassessment of the sexual sphere during the eighties and nineties as the "neosexual revolution". The neosexual revolution is dismantling the old patterns of sexuality and reassembling them anew. In the process, dimensions, intimate relationships, preferences and sexual fragments emerge, many of which had submerged, were unnamed or simply did not exist before. In general, sexuality has lost much of its symbolic meaning as a cultural phenomenon. Sexuality is no longer the great metaphor for pleasure and happiness, nor is it so greatly overestimated as it was during the sexual revolution. It is now widely taken for granted, much like egotism or motility. Whereas sex was once mystified in a positive sense - as ecstasy and transgression, it has now taken on a negative mystification characterized by abuse, violence and deadly infection. While the old sexuality was based primarily upon sexual instinct, orgasm and the heterosexual couple, neosexualities revolve predominantly around gender difference, thrills, self-gratification and prosthetic substitution. From the vast number of interrelated processes from which neosexualities emerge, three empirically observable phenomena have been selected for discussion here: the dissociation of the sexual sphere, the dispersion of sexual fragments and the diversification of intimate relationships. The outcome of the neosexual revolution may be described as "lean sexuality" and "self-sex".

Adolescent Sexual Decision-Making: An Integrative Review.

PubMed

Hulton, Linda J.

2001-10-03

PURPOSE: The purpose of this integrative review was to summarize the present literature to identify factors associated with adolescent sexual decision-making. Thirty-eight salient research studies were selected as a basis of this review from the databases of Medline, CINAHL, and Psychinfo using the Cooper methodology. CONCLUSIONS: Two categories of decision-making were identified: 1) The research on factors related to the decisions that adolescents make to become sexually active or to abstain from sexual activity; 2) The research on factors related to contraceptive decision-making. The most consistent findings were that the factors of gender differences, cognitive development, perception of benefits, parental influences, social influences, and sexual knowledge were important variables in the decision-making processes of adolescents. IMPLICATIONS: Practice implications for nursing suggest that clinicians should assess adolescent sexual decision-making in greater detail and address the social and psychological context in which sexual experiences occur. Nurses must be aware of the differences between adolescent and adult decision-making processes and incorporate knowledge of growth and development into intervention strategies. Moreover, to the degree that adolescent sexual decision-making proves to be less than rational, interventions designed to improve competent sexual decision-making are needed.

Concurrent natural and sexual selection in wild male sockeye salmon, Oncorhynchus nerka.

PubMed

Hamon, Troy R; Foote, Chris J

2005-05-01

Concurrent natural and sexual selection have been inferred from laboratory and comparative studies in a number of taxa, but are rarely measured in natural populations. Because the interaction of these two general categories of selection may be complex when they occur simultaneously, empirical evidence from natural populations would help us to understand this interaction and probably give us greater insight into each separate episode as well. In male sockeye salmon, sexual selection for larger body size has been indicated in both deep and shallow water habitats. However, in shallow habitats male sockeye are generally smaller and less deep-bodied than in deep habitats, a difference that has been ascribed to natural selection. We measured concurrent natural and sexual selection in two years on breeding male sockeye salmon with respect to body size, body shape, and time of arrival to the breeding grounds. Natural selection was variable in effect and sexual selection was variable in intensity in these two years. The patterns of selection also appear to be interdependent; areas where predation on spawning adults is not intense have yielded different patterns of sexual selection than those measured here. It appears that some of the body shape differences in sockeye salmon associated with different spawning habitats, which were previously attributed to selective mortality, may be a result of different patterns of sexual selection in the different habitats. Total selection resulting from the combination of both natural and sexual selection was less intense than either natural or sexual selection in most cases. Measurement of concurrent selection episodes in nature may help us to understand whether the pattern of differential sexual selection is common, and whether observed patterns of habitat-related differentiation may be due to differences in sexual selection.

Intrasexual competition in females: evidence for sexual selection?

PubMed

Rosvall, Kimberly A

2011-11-01

In spite of recent interest in sexual selection in females, debate exists over whether traits that influence female-female competition are sexually selected. This review uses female-female aggressive behavior as a model behavioral trait for understanding the evolutionary mechanisms promoting intrasexual competition, focusing especially on sexual selection. I employ a broad definition of sexual selection, whereby traits that influence competition for mates are sexually selected, whereas those that directly influence fecundity or offspring survival are naturally selected. Drawing examples from across animal taxa, including humans, I examine 4 predictions about female intrasexual competition based on the abundance of resources, the availability of males, and the direct or indirect benefits those males provide. These patterns reveal a key sex difference in sexual selection: Although females may compete for the number of mates, they appear to compete more so for access to high-quality mates that provide direct and indirect (genetic) benefits. As is the case in males, intrasexual selection in females also includes competition for essential resources required for access to mates. If mate quality affects the magnitude of mating success, then restricting sexual selection to competition for quantity of mates may ignore important components of fitness in females and underestimate the role of sexual selection in shaping female phenotype. In the future, understanding sex differences in sexual selection will require further exploration of the extent of mutual intrasexual competition and the incorporation of quality of mating success into the study of sexual selection in both sexes.

Intrasexual competition in females: evidence for sexual selection?

PubMed Central

2011-01-01

In spite of recent interest in sexual selection in females, debate exists over whether traits that influence female–female competition are sexually selected. This review uses female–female aggressive behavior as a model behavioral trait for understanding the evolutionary mechanisms promoting intrasexual competition, focusing especially on sexual selection. I employ a broad definition of sexual selection, whereby traits that influence competition for mates are sexually selected, whereas those that directly influence fecundity or offspring survival are naturally selected. Drawing examples from across animal taxa, including humans, I examine 4 predictions about female intrasexual competition based on the abundance of resources, the availability of males, and the direct or indirect benefits those males provide. These patterns reveal a key sex difference in sexual selection: Although females may compete for the number of mates, they appear to compete more so for access to high-quality mates that provide direct and indirect (genetic) benefits. As is the case in males, intrasexual selection in females also includes competition for essential resources required for access to mates. If mate quality affects the magnitude of mating success, then restricting sexual selection to competition for quantity of mates may ignore important components of fitness in females and underestimate the role of sexual selection in shaping female phenotype. In the future, understanding sex differences in sexual selection will require further exploration of the extent of mutual intrasexual competition and the incorporation of quality of mating success into the study of sexual selection in both sexes. PMID:22479137

Sex differences, sexual selection, and ageing: an experimental evolution approach.

PubMed

Maklakov, Alexei A; Bonduriansky, Russell; Brooks, Robert C

2009-10-01

Life-history (LH) theory predicts that selection will optimize the trade-off between reproduction and somatic maintenance. Reproductive ageing and finite life span are direct consequences of such optimization. Sexual selection and conflict profoundly affect the reproductive strategies of the sexes and thus can play an important role in the evolution of life span and ageing. In theory, sexual selection can favor the evolution of either faster or slower ageing, but the evidence is equivocal. We used a novel selection experiment to investigate the potential of sexual selection to influence the adaptive evolution of age-specific LH traits. We selected replicate populations of the seed beetle Callosobruchus maculatus for age at reproduction ("Young" and "Old") either with or without sexual selection. We found that LH selection resulted in the evolution of age-specific reproduction and mortality but these changes were largely unaffected by sexual selection. Sexual selection depressed net reproductive performance and failed to promote adaptation. Nonetheless, the evolution of several traits differed between males and females. These data challenge the importance of current sexual selection in promoting rapid adaptation to environmental change but support the hypothesis that sex differences in LH-a historical signature of sexual selection-are key in shaping trait responses to novel selection.

Sexually Transmitted Infections and Unintended Pregnancy: A Longitudinal Analysis of Risk Transmission through Friends and Attitudes

ERIC Educational Resources Information Center

Henry, David B.; Deptula, Daneen P.; Schoeny, Michael E.

2012-01-01

Data from 1,087 adolescent participants in three waves of the National Longitudinal Study of Adolescent Health were used to examine the effects of peer selection and socialization processes in adolescence on later reports of sexually transmitted infections (STI) and unintended pregnancies. Friends' attitudes and behavior were assessed with…

Sexually selected females in the monogamous Western Australian seahorse.

PubMed

Kvarnemo, Charlotta; Moore, Glenn I; Jones, Adam G

2007-02-22

Studies of sexual selection in monogamous species have hitherto focused on sexual selection among males. Here, we provide empirical documentation that sexual selection can also act strongly on females in a natural population with a monogamous mating system. In our field-based genetic study of the monogamous Western Australian seahorse, Hippocampus subelongatus, sexual selection differentials and gradients show that females are under stronger sexual selection than males: mated females are larger than unmated ones, whereas mated and unmated males do not differ in size. In addition, the opportunity for sexual selection (variance in mating success divided by its mean squared) for females is almost three times that for males. These results, which seem to be generated by a combination of a male preference for larger females and a female-biased adult sex ratio, indicate that substantial sexual selection on females is a potentially important but under-appreciated evolutionary phenomenon in monogamous species.

Sexually selected females in the monogamous Western Australian seahorse

PubMed Central

Kvarnemo, Charlotta; Moore, Glenn I; Jones, Adam G

2006-01-01

Studies of sexual selection in monogamous species have hitherto focused on sexual selection among males. Here, we provide empirical documentation that sexual selection can also act strongly on females in a natural population with a monogamous mating system. In our field-based genetic study of the monogamous Western Australian seahorse, Hippocampus subelongatus, sexual selection differentials and gradients show that females are under stronger sexual selection than males: mated females are larger than unmated ones, whereas mated and unmated males do not differ in size. In addition, the opportunity for sexual selection (variance in mating success divided by its mean squared) for females is almost three times that for males. These results, which seem to be generated by a combination of a male preference for larger females and a female-biased adult sex ratio, indicate that substantial sexual selection on females is a potentially important but under-appreciated evolutionary phenomenon in monogamous species. PMID:17476772

Sexual selection is a form of social selection.

PubMed

Lyon, Bruce E; Montgomerie, Robert

2012-08-19

Social selection influences the evolution of weapons, ornaments and behaviour in both males and females. Thus, social interactions in both sexual and non-sexual contexts can have a powerful influence on the evolution of traits that would otherwise appear to be detrimental to survival. Although clearly outlined by West-Eberhard in the early 1980s, the idea that social selection is a comprehensive framework for the study of ornaments and weapons has largely been ignored. In West-Eberhard's view, sexual selection is a form of social selection-a concept supported by several lines of evidence. Darwin's distinction between natural and sexual selection has been useful, but recent confusion about the limits of sexual selection suggests that some traits are not easily categorized as naturally or sexually selected. Because social selection theory has much to offer the current debates about both sexual selection and reproductive competition in females, it is sometimes viewed, narrowly, to be most useful when considering female roles. However, social selection theory encompasses much more than female reproductive competition. Our goal here was to provide that broader perspective.

[Social transformation of sexuality in the past decades. An overview].

PubMed

Sigusch, V

2000-03-01

The societies of the Western world have witnessed a tremendous cultural and social transformation of sexuality during the eighties and nineties, a process Sigusch refers to as "the neosexual revolution". Up to now, this transformation and reassessment of sexuality has proceeded rather slowly and quietly. Yet both its real and its symbolic effects may indeed be more consequential that those brought about in the course of the rapid, noisy sexual revolution of the sixties and seventies. The neosexual revolution is dismantling the old patterns of sexuality and reassembling them anew. In the process, dimensions, intimate relationships, preferences and sexual fragments emerge, many of which had submerged, were unnamed or simply did not exist before. In general, sexuality has lost much of its symbolic meaning as a cultural phenomenon. Sexuality is no longer the great metaphor for pleasure and happiness, nor is it so greatly overestimated as it was during the sexual revolution. It is now widely taken for granted, much like egotism or motility. Whereas sex was once mystified in a positive sense--as ecstasy and transgression, it has now taken on a negative mystification characterized by abuse, violence and deadly infection. While the old sexuality was based primarily upon sexual instinct, orgasm and the heterosexual couple, neosexualities revolve predominantly around gender difference, thrills, self-gratification and prosthetic substitution. From the vast number of interrelated processes from which neosexualities emerge, three phenomena have been selected for discussion here: the dissociation of the sexual sphere, the dispersion of sexual fragments and the diversification of sexual relationships. The outcome of the neosexual revolution could be described as self-disciplined and self-optimized "self-sex".

The neosexual revolution.

PubMed

Sigusch, V

1998-08-01

The affluent societies of the Western world have witnessed a tremendous cultural and social transformation of sexuality during the 1980s and 1990s, a process I refer to as the neosexual revolution. Up to now, this recoding and reassessment of sexuality has proceeded rather slowly and quietly. Yet both its real and its symbolic effects may indeed be more consequential than those brought about in the course of the rapid, noisy sexual revolution of the 1960s and 1970s. The neosexual revolution is dismantling the old patterns of sexuality and reassembling them anew. In the process, dimensions, intimate relationships, preferences, and sexual fragments emerge, many of which had been submerged, were unnamed, or simply did not exist before. In general, sexuality has lost much of its symbolic meaning as a cultural phenomenon. Sexuality is no longer the great metaphor for pleasure and happiness, nor is it so greatly overestimated as it was during the sexual revolution. It is now widely taken for granted, much like egotism or motility. Whereas sex was once mystified in a positive sense--as ecstasy and transgression, it has now taken on a negative mystification characterized by abuse, violence, and deadly infection. While the old sexuality was based primarily upon sexual instinct, orgasm, and the heterosexual couple, neosexualities revolve predominantly around gender difference, thrills, self-gratification, and prosthetic substitution. From the vast number of interrelated processes from which neosexualities emerge, three empirically observable phenomena have been selected for discussion here: the dissociation of the sexual sphere, the dispersion of sexual fragments, and the diversification of intimate relationships. These processes go hand in hand with the commercialization and banalization of sexuality. They are looked upon as being controlled individually through the mechanisms of a fundamentally egotistical consensus morality. In conformity with the general principles at work in society, the outcome of the neosexual revolution could be described as self-disciplined and self-optimized lean sexuality.

Antagonistic responses to natural and sexual selection and the sex-specific evolution of cuticular hydrocarbons in Drosophila simulans.

PubMed

Sharma, Manmohan D; Hunt, John; Hosken, David J

2012-03-01

Natural and sexual selection are classically thought to oppose one another, and although there is evidence for this, direct experimental demonstrations of this antagonism are largely lacking. Here, we assessed the effects of sexual and natural selection on the evolution of cuticular hydrocarbons (CHCs), a character subject to both modes of selection, in Drosophila simulans. Natural selection and sexual selection were manipulated in a fully factorial design, and after 27 generations of experimental evolution, the responses of male and female CHCs were assessed. The effects of natural and sexual selection differed greatly across the sexes. The responses of female CHCs were generally small, but CHCs evolved predominantly in the direction of natural selection. For males, profiles evolved via sexual and natural selection, as well as through the interaction between the two, with some male CHC components only evolving in the direction of natural selection when sexual selection was relaxed. These results indicate sex-specific responses to selection, and that sexual and natural selection act antagonistically for at least some combinations of CHCs. © 2011 The Author(s). Evolution© 2011 The Society for the Study of Evolution.

An integrative view of sexual selection in Tribolium flour beetles.

PubMed

Fedina, Tatyana Y; Lewis, Sara M

2008-05-01

Sexual selection is a major force driving the evolution of diverse reproductive traits. This evolutionary process is based on individual reproductive advantages that arise either through intrasexual competition or through intersexual choice and conflict. While classical studies of sexual selection focused mainly on differences in male mating success, more recent work has focused on the differences in paternity share that may arise through sperm competition or cryptic female choice whenever females mate with multiple males. Thus, an integrative view of sexual selection needs to encompass processes that occur not only before copulation (pre-mating), but also during copulation (peri-mating), as well as after copulation (post-mating), all of which can generate differences in reproductive success. By encompassing mechanisms of sexual selection across all of these sequential reproductive stages this review takes an integrative approach to sexual selection in Tribolium flour beetles (Coleoptera: Tenebrionidae), a particularly well-studied and economically important model organism. Tribolium flour beetles colonize patchily distributed grain stores, and juvenile and adult stages share the same food resources. Adults are highly promiscuous and female reproduction is distributed across an adult lifespan lasting approximately 1 year. While Tribolium males produce an aggregation pheromone that attracts both sexes, there appears to be little pre-mating discrimination among potential mates by either sex. However, recent work has revealed several peri-mating and post-mating mechanisms that determine how offspring paternity is apportioned among a female's mates. During mating, Tribolium females reject spermatophore transfer and limit sperm numbers transferred by males with low phenotypic quality. Although there is some conflicting evidence, male copulatory leg-rubbing appears to be associated with overcoming female resistance to insemination and does not influence a male's subsequent paternity share. Evidence suggests that Tribolium beetles have several possible post-mating mechanisms that they may use to bias paternity. Male sperm precedence has been extensively studied in Tribolium spp. and the related Tenebrio molitor, and several factors influencing male paternity share among a female's progeny have been identified. These include oviposition time, inter-mating interval, male strain/genotype, the mating regimen of a male's mother, male starvation, and tapeworm infection. Females exert muscular control over sperm storage, although there is no evidence to date that females use this to differentiate among mates. Females could also influence offspring paternity by re-mating with additional males, and T. castaneum females more readily accept spermatophores when they are re-mating with more attractive males. Additional work is needed to examine the possible roles played by both male and female accessory gland products in determining male paternity share. Sexual selection during pre-mating episodes may be reinforced or counteracted by peri- and post-copulatory selection, and antagonistic coevolution between the sexes may be played out across reproductive stages. In Tribolium, males' olfactory attractiveness is positively correlated with both insemination success and paternity share, suggesting consistent selection across different reproductive stages. Similar studies across sequential reproductive stages are needed in other taxa to provide a more integrative view of sexual selection.

A novel method of comparing mating success and survival reveals similar sexual and viability selection for mobility traits in female tree crickets.

PubMed

Ercit, K; Gwynne, D T

2016-06-01

The relationship between sexual and viability selection in females is necessarily different than that in males, as investment in sexual traits potentially comes at the expense of both fecundity and survival. Accordingly, females do not usually invest in sexually selected traits. However, direct benefits obtained from mating, such as nuptial gifts, may encourage competition among females and subsidize investment into sexually selected traits. We compared sexual and viability selection on female tree crickets Oecanthus nigricornis, a species where females mate frequently to obtain nuptial gifts and sexual selection on females is likely. If male choice determines female mating success in this species, we expect sexual selection for fecundity traits, as males of many species prefer more fecund females. Alternatively, intrasexual scramble or combat competition on females may select for larger jumping legs or wider heads (respectively). We estimated mating success in wild caught crickets using microsatellite analysis of stored sperm and estimated relative viability by comparing surviving female O. nigricornis to those captured by a common wasp predator. In support of the scramble competition hypothesis, we found sexual selection for females with larger hind legs and narrower heads. We also found stabilizing viability selection for intermediate head width and hind leg size. As predicted, traits under viability and sexual selection were very similar, and the direction of that selection was not opposing. However, because the shape of sexual and viability selection differs, these episodes of selection may favour slightly different trait sizes. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

Need fulfillment in the sexual relationships of HIV-infected men who have sex with men.

PubMed

Craft, Shonda M; Smith, Sarah A; Serovich, Julianne M; Bautista, Dianne T

2005-06-01

This article explores the associations among sexual need fulfillment, partner selection, and risky sexual behavior, using a functional/motivational perspective. The authors suggest that sexual needs influence partner selection (e.g., steady versus nonsteady), and engaging in UAI is influenced by sexual needs and partner selection. A sample of 108 HIV-positive gay men completed measures of sexual frequency, sexual risk-taking behaviors, and sexual need fulfillment. Results indicated support for both objectives. These men were more likely to choose a steady partner when they possessed greater relationship needs, whereas while men with higher substitution and pleasure needs were more likely to select nonsteady partners. In addition, only men who reported greater substitution needs were more likely to engage in UAI. The results suggest that certain sexual needs influence partner selection, but that sexual needs also influence what activities occur in the encounter.

Parallel evolution of sexual isolation in sticklebacks.

PubMed

Boughman, Janette Wenrick; Rundle, Howard D; Schluter, Dolph

2005-02-01

Mechanisms of speciation are not well understood, despite decades of study. Recent work has focused on how natural and sexual selection cause sexual isolation. Here, we investigate the roles of divergent natural and sexual selection in the evolution of sexual isolation between sympatric species of threespine sticklebacks. We test the importance of morphological and behavioral traits in conferring sexual isolation and examine to what extent these traits have diverged in parallel between multiple, independently evolved species pairs. We use the patterns of evolution in ecological and mating traits to infer the likely nature of selection on sexual isolation. Strong parallel evolution implicates ecologically based divergent natural and/or sexual selection, whereas arbitrary directionality implicates nonecological sexual selection or drift. In multiple pairs we find that sexual isolation arises in the same way: assortative mating on body size and asymmetric isolation due to male nuptial color. Body size and color have diverged in a strongly parallel manner, similar to ecological traits. The data implicate ecologically based divergent natural and sexual selection as engines of speciation in this group.

Rapid adaptation to a novel host in a seed beetle (Callosobruchus maculatus): the role of sexual selection.

PubMed

Fricke, Claudia; Arnqvist, Göran

2007-02-01

Rapid diversification is common among herbivorous insects and is often the result of host shifts, leading to the exploitation of novel food sources. This, in turn, is associated with adaptive evolution of female oviposition behavior and larval feeding biology. Although natural selection is the typical driver of such adaptation, the role of sexual selection is less clear. In theory, sexual selection can either accelerate or impede adaptation. To assess the independent effects of natural and sexual selection on the rate of adaptation, we performed a laboratory natural selection experiment in a herbivorous bruchid beetle (Callosobruchus maculatus). We established replicated selection lines where we varied natural (food type) and sexual (mating system) selection in a 2 x 2 orthogonal design, and propagated our lines for 35 generations. In half of the lines, we induced a host shift whereas the other half was kept on the ancestral host. We experimentally enforced monogamy in half of the lines, whereas the other half remained polygamous. The beetles rapidly adapted to the novel host, which primarily involved increased host acceptance by females and an accelerated rate of larval development. We also found that our mating system treatment affected the rate of adaptation, but that this effect was contingent upon food type. As beetles adapted to the novel host, sexual selection reinforced natural selection whereas populations residing close to their adaptive peak (i.e., those using their ancestral host) exhibited higher fitness in the absence of sexual selection. We discuss our findings in light of current sexual selection theory and suggest that the net evolutionary effect of reproductive competition may critically depend on natural selection. Sexual selection may commonly accelerate adaptation under directional natural selection whereas sexual selection, and the associated load brought by sexual conflict, may tend to depress population fitness under stabilizing natural selection.

The maintenance of phenotypic divergence through sexual selection: An experimental study in barn swallows Hirundo rustica.

PubMed

Safran, Rebecca J; Vortman, Yoni; Jenkins, Brittany R; Hubbard, Joanna K; Wilkins, Matthew R; Bradley, Rachel J; Lotem, Arnon

2016-09-01

Previous studies have shown that sexual signals can rapidly diverge among closely related species. However, we lack experimental studies to demonstrate that differences in trait-associated reproductive performance maintain sexual trait differences between closely related populations, in support for a role of sexual selection in speciation. Populations of Northern Hemisphere distributed barn swallows Hirundo rustica are closely related, yet differ in two plumage-based traits: ventral color and length of the outermost tail feathers (streamers). Here we provide experimental evidence that manipulations of these traits result in different reproductive consequences in two subspecies of barn swallow: (H. r. erythrogaster in North America and H. r. transitiva in the East Mediterranean). Experimental results in Colorado, USA, demonstrate that males with (1) darkened ventral coloration and (2) shortened streamers gained paternity between two successive reproductive bouts. In contrast, exaggeration of both traits improved reproductive performance within H. r. transitiva in Israel: males with a combination treatment of darkened ventral coloration and elongated streamers gained paternity between two successive reproductive bouts. Collectively, these experimental results fill an important gap in our understanding for how divergent sexual selection maintains phenotype differentiation in closely related populations, an important aspect of the speciation process. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

Sexual selection and the evolution of secondary sexual traits: sex comb evolution in Drosophila.

PubMed

Snook, Rhonda R; Gidaszewski, Nelly A; Chapman, Tracey; Simmons, Leigh W

2013-04-01

Sexual selection can drive rapid evolutionary change in reproductive behaviour, morphology and physiology. This often leads to the evolution of sexual dimorphism, and continued exaggerated expression of dimorphic sexual characteristics, although a variety of other alternative selection scenarios exist. Here, we examined the evolutionary significance of a rapidly evolving, sexually dimorphic trait, sex comb tooth number, in two Drosophila species. The presence of the sex comb in both D. melanogaster and D. pseudoobscura is known to be positively related to mating success, although little is yet known about the sexually selected benefits of sex comb structure. In this study, we used experimental evolution to test the idea that enhancing or eliminating sexual selection would lead to variation in sex comb tooth number. However, the results showed no effect of either enforced monogamy or elevated promiscuity on this trait. We discuss several hypotheses to explain the lack of divergence, focussing on sexually antagonistic coevolution, stabilizing selection via species recognition and nonlinear selection. We discuss how these are important, but relatively ignored, alternatives in understanding the evolution of rapidly evolving sexually dimorphic traits. © 2013 The Authors. Journal of Evolutionary Biology © 2013 European Society For Evolutionary Biology.

Understanding the link between sexual selection, sexual conflict and aging using crickets as a model.

PubMed

Archer, C Ruth; Hunt, John

2015-11-01

Aging evolved because the strength of natural selection declines over the lifetime of most organisms. Weak natural selection late in life allows the accumulation of deleterious mutations and may favor alleles that have positive effects on fitness early in life, but costly pleiotropic effects expressed later on. While this decline in natural selection is central to longstanding evolutionary explanations for aging, a role for sexual selection and sexual conflict in the evolution of lifespan and aging has only been identified recently. Testing how sexual selection and sexual conflict affect lifespan and aging is challenging as it requires quantifying male age-dependent reproductive success. This is difficult in the invertebrate model organisms traditionally used in aging research. Research using crickets (Orthoptera: Gryllidae), where reproductive investment can be easily measured in both sexes, has offered exciting and novel insights into how sexual selection and sexual conflict affect the evolution of aging, both in the laboratory and in the wild. Here we discuss how sexual selection and sexual conflict can be integrated alongside evolutionary and mechanistic theories of aging using crickets as a model. We then highlight the potential for research using crickets to further advance our understanding of lifespan and aging. Copyright © 2015 Elsevier Inc. All rights reserved.

Male Mating Success: Preference or Prowess? Investigating Sexual Selection in the Laboratory Using "Drosophila melanogaster"

ERIC Educational Resources Information Center

Coleman, Seth; Jensen, Jeffrey

2007-01-01

Sexual selection is the primary force affecting the evolution of the elaborate sexual displays common in animals, yet sexual selection experiments are largely absent from introductory biology laboratories. Here we describe the rationale, methodology, and results of several experiments using "Drosophila melanogaster" to demonstrate sexual selection…

The Relationship between Sexual Selection and Sexual Conflict

PubMed Central

Kokko, Hanna; Jennions, Michael D.

2014-01-01

Evolutionary conflicts of interest arise whenever genetically different individuals interact and their routes to fitness maximization differ. Sexual selection favors traits that increase an individual’s competitiveness to acquire mates and fertilizations. Sexual conflict occurs if an individual of sex A’s relative fitness would increase if it had a “tool” that could alter what an individual of sex B does (including the parental genes transferred), at a cost to B’s fitness. This definition clarifies several issues: Conflict is very common and, although it extends outside traits under sexual selection, sexual selection is a ready source of sexual conflict. Sexual conflict and sexual selection should not be presented as alternative explanations for trait evolution. Conflict is closely linked to the concept of a lag load, which is context-dependent and sex-specific. This makes it possible to ask if one sex can “win.” We expect higher population fitness if females win. PMID:25038050

A Macroevolutionary Perspective on Multiple Sexual Traits in the Phasianidae (Galliformes)

PubMed Central

Kimball, Rebecca T.; Mary, Colette M. St.; Braun, Edward L.

2011-01-01

Traits involved in sexual signaling are ubiquitous among animals. Although a single trait appears sufficient to convey information, many sexually dimorphic species exhibit multiple sexual signals, which may be costly to signalers and receivers. Given that one signal may be enough, there are many microevolutionary hypotheses to explain the evolution of multiple signals. Here we extend these hypotheses to a macroevolutionary scale and compare those predictions to the patterns of gains and losses of sexual dimorphism in pheasants and partridges. Among nine dimorphic characters, including six intersexual signals and three indicators of competitive ability, all exhibited both gains and losses of dimorphism within the group. Although theories of intersexual selection emphasize gain and elaboration, those six characters exhibited greater rates of loss than gain; in contrast, the competitive traits showed a slight bias towards gains. The available models, when examined in a macroevolutionary framework, did not yield unique predictions, making it difficult to distinguish among them. Even with this limitation, when the predictions of these alternative models were compared with the heterogeneous patterns of evolution of dimorphism in phasianids, it is clear that many different selective processes have been involved in the evolution of sexual signals in this group. PMID:21716735

Adapting the Get Yourself Tested Campaign to Reach Black and Latino Sexual-Minority Youth.

PubMed

Garbers, Samantha; Friedman, Allison; Martinez, Omar; Scheinmann, Roberta; Bermudez, Dayana; Silva, Manel; Silverman, Jen; Chiasson, Mary Ann

2016-09-01

Culturally appropriate efforts are needed to increase sexually transmitted disease (STD) testing and care among Black and Latino sexual-minority youth, who are at high risk for STDs. Get Yourself Tested, a national testing campaign, has demonstrated success among youth, but it has yet to be assessed for relevance or impact among this population. This effort included (1) formative and materials-testing research through focus groups; (2) adaptation of existing Get Yourself Tested campaign materials to be more inclusive of Black and Latino sexual-minority youth; (3) a 3-month campaign in four venues of New York City, promoting STD testing at events and through mobile testing and online and social media platforms; (4) process evaluation of outreach activities; and (5) an outcome evaluation of testing at select campaign venues, using a preexperimental design. During the 3-month campaign period, the number of STD tests conducted at select campaign venues increased from a comparable 3-month baseline period. Although testing uptake through mobile vans remained low in absolute numbers, the van drew a high-prevalence sample, with positivity rates of 26.9% for chlamydia and 11.5% for gonorrhea. This article documents the process and lessons learned from adapting and implementing a local campaign for Black and Latino sexual-minority youth. © 2016 Society for Public Health Education.

Are sexual media exposure, parental restrictions on media use and co-viewing TV and DVDs with parents and friends associated with teenagers' early sexual behaviour?☆

PubMed Central

Parkes, Alison; Wight, Daniel; Hunt, Kate; Henderson, Marion; Sargent, James

2013-01-01

Sexual content in teenagers' media diets is known to predict early sexual behaviour. Research on sexual content has not allowed for the social context of media use, which may affect selection and processing of content. This study investigated whether sexual media content and/or contextual factors (co-viewing, parental media restrictions) were associated with early sexual behaviour using 2251 14–15 year-olds from Scotland, UK. A third (n = 733) reported sexual intercourse. In multivariable analysis the likelihood of intercourse was lower with parental restriction of sexual media and same-sex peer co-viewing; but higher with mixed-sex peer co-viewing. Parental co-viewing, other parental restrictions on media and sexual film content exposure were not associated with intercourse. Findings suggest the context of media use may influence early sexual behaviour. Specific parental restrictions on sexual media may offer more protection against early sex than other restrictions or parental co-viewing. Further research is required to establish causal mechanisms. PMID:24215959

Are sexual media exposure, parental restrictions on media use and co-viewing TV and DVDs with parents and friends associated with teenagers' early sexual behaviour?

PubMed

Parkes, Alison; Wight, Daniel; Hunt, Kate; Henderson, Marion; Sargent, James

2013-12-01

Sexual content in teenagers' media diets is known to predict early sexual behaviour. Research on sexual content has not allowed for the social context of media use, which may affect selection and processing of content. This study investigated whether sexual media content and/or contextual factors (co-viewing, parental media restrictions) were associated with early sexual behaviour using 2251 14-15 year-olds from Scotland, UK. A third (n = 733) reported sexual intercourse. In multivariable analysis the likelihood of intercourse was lower with parental restriction of sexual media and same-sex peer co-viewing; but higher with mixed-sex peer co-viewing. Parental co-viewing, other parental restrictions on media and sexual film content exposure were not associated with intercourse. Findings suggest the context of media use may influence early sexual behaviour. Specific parental restrictions on sexual media may offer more protection against early sex than other restrictions or parental co-viewing. Further research is required to establish causal mechanisms. Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.

The role of ecology in speciation by sexual selection: a systematic empirical review.

PubMed

Scordato, Elizabeth S C; Symes, Laurel B; Mendelson, Tamra C; Safran, Rebecca J

2014-01-01

Theoretical and empirical research indicates that sexual selection interacts with the ecological context in which mate choice occurs, suggesting that sexual and natural selection act together during the evolution of premating reproductive isolation. However, the relative importance of natural and sexual selection to speciation remains poorly understood. Here, we applied a recent conceptual framework for examining interactions between mate choice divergence and ecological context to a review of the empirical literature on speciation by sexual selection. This framework defines two types of interactions between mate choice and ecology: internal interactions, wherein natural and sexual selection jointly influence divergence in sexual signal traits and preferences, and external interactions, wherein sexual selection alone acts on traits and preferences but ecological context shapes the transmission efficacy of sexual signals. The objectives of this synthesis were 3-fold: to summarize the traits, ecological factors, taxa, and geographic contexts involved in studies of mate choice divergence; to analyze patterns of association between these variables; and to identify the most common types of interactions between mate choice and ecological factors. Our analysis revealed that certain traits are consistently associated with certain ecological factors. Moreover, among studies that examined a divergent sexually selected trait and an ecological factor, internal interactions were more common than external interactions. Trait-preference associations may thus frequently be subject to both sexual and natural selection in cases of divergent mate choice. Our results highlight the importance of interactions between sexual selection and ecology in mate choice divergence and suggest areas for future research. © The American Genetic Association. 2014. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Sexual selection protects against extinction.

PubMed

Lumley, Alyson J; Michalczyk, Łukasz; Kitson, James J N; Spurgin, Lewis G; Morrison, Catriona A; Godwin, Joanne L; Dickinson, Matthew E; Martin, Oliver Y; Emerson, Brent C; Chapman, Tracey; Gage, Matthew J G

2015-06-25

Reproduction through sex carries substantial costs, mainly because only half of sexual adults produce offspring. It has been theorized that these costs could be countered if sex allows sexual selection to clear the universal fitness constraint of mutation load. Under sexual selection, competition between (usually) males and mate choice by (usually) females create important intraspecific filters for reproductive success, so that only a subset of males gains paternity. If reproductive success under sexual selection is dependent on individual condition, which is contingent to mutation load, then sexually selected filtering through 'genic capture' could offset the costs of sex because it provides genetic benefits to populations. Here we test this theory experimentally by comparing whether populations with histories of strong versus weak sexual selection purge mutation load and resist extinction differently. After evolving replicate populations of the flour beetle Tribolium castaneum for 6 to 7 years under conditions that differed solely in the strengths of sexual selection, we revealed mutation load using inbreeding. Lineages from populations that had previously experienced strong sexual selection were resilient to extinction and maintained fitness under inbreeding, with some families continuing to survive after 20 generations of sib × sib mating. By contrast, lineages derived from populations that experienced weak or non-existent sexual selection showed rapid fitness declines under inbreeding, and all were extinct after generation 10. Multiple mutations across the genome with individually small effects can be difficult to clear, yet sum to a significant fitness load; our findings reveal that sexual selection reduces this load, improving population viability in the face of genetic stress.

Sexual imprinting on ecologically divergent traits leads to sexual isolation in sticklebacks

PubMed Central

Kozak, Genevieve M.; Head, Megan L.; Boughman, Janette W.

2011-01-01

During sexual imprinting, offspring learn parental phenotypes and then select mates who are similar to their parents. Imprinting has been thought to contribute to the process of speciation in only a few rare cases; this is despite imprinting's potential to generate assortative mating and solve the problem of recombination in ecological speciation. If offspring imprint on parental traits under divergent selection, these traits will then be involved in both adaptation and mate preference. Such ‘magic traits’ easily generate sexual isolation and facilitate speciation. In this study, we show that imprinting occurs in two ecologically divergent stickleback species (benthics and limnetics: Gasterosteus spp.). Cross-fostered females preferred mates of their foster father's species. Furthermore, imprinting is essential for sexual isolation between species; isolation was reduced when females were raised without fathers. Daughters imprinted on father odour and colour during a critical period early in development. These traits have diverged between the species owing to differences in ecology. Therefore, we provide the first evidence that imprinting links ecological adaptation to sexual isolation between species. Our results suggest that imprinting may facilitate the evolution of sexual isolation during ecological speciation, may be especially important in cases of rapid diversification, and thus play an integral role in the generation of biodiversity. PMID:21270044

Sexual imprinting on ecologically divergent traits leads to sexual isolation in sticklebacks.

PubMed

Kozak, Genevieve M; Head, Megan L; Boughman, Janette W

2011-09-07

During sexual imprinting, offspring learn parental phenotypes and then select mates who are similar to their parents. Imprinting has been thought to contribute to the process of speciation in only a few rare cases; this is despite imprinting's potential to generate assortative mating and solve the problem of recombination in ecological speciation. If offspring imprint on parental traits under divergent selection, these traits will then be involved in both adaptation and mate preference. Such 'magic traits' easily generate sexual isolation and facilitate speciation. In this study, we show that imprinting occurs in two ecologically divergent stickleback species (benthics and limnetics: Gasterosteus spp.). Cross-fostered females preferred mates of their foster father's species. Furthermore, imprinting is essential for sexual isolation between species; isolation was reduced when females were raised without fathers. Daughters imprinted on father odour and colour during a critical period early in development. These traits have diverged between the species owing to differences in ecology. Therefore, we provide the first evidence that imprinting links ecological adaptation to sexual isolation between species. Our results suggest that imprinting may facilitate the evolution of sexual isolation during ecological speciation, may be especially important in cases of rapid diversification, and thus play an integral role in the generation of biodiversity.

Agricultural management affects evolutionary processes in a migratory songbird

USGS Publications Warehouse

Perlut, N.G.; Freeman-Gallant, C. R.; Strong, A.M.; Donovan, T.M.; Kilpatrick, C.W.; Zalik, N.J.

2008-01-01

Hay harvests have detrimental ecological effects on breeding songbirds, as harvesting results in nest failure. Importantly, whether harvesting also affects evolutionary processes is not known. We explored how hay harvest affected social and genetic mating patterns, and thus, the overall opportunity for sexual selection and evolutionary processes for a ground-nesting songbird, the Savannah sparrow (Passerculus sandwichensis). On an unharvested field, 55% of females were in polygynous associations, and social polygyny was associated with greater rates of extra-pair paternity (EPP). In this treatment, synchrony explained variation in EPP rates, as broods by more synchronous females had more EPP than broods by asynchronous females. In contrast, on a harvested field, simultaneous nest failure caused by haying dramatically decreased the overall incidence of EPP by increasing the occurrence of social monogamy and, apparently, the ability of polygynous males to maintain paternity in their own nests. Despite increased social and genetic monogamy, these haying-mediated changes in mating systems resulted in greater than twofold increase in the opportunity for sexual selection. This effect arose, in part, from a 30% increase in the variance associated with within-pair fertilization success, relative to the unharvested field. This effect was caused by a notable increase (+110%) in variance associated with the quality of social mates following simultaneous nest failure. Because up to 40% of regional habitat is harvested by early June, these data may demonstrate a strong population-level effect on mating systems, sexual selection, and consequently, evolutionary processes. ?? 2008 The Authors.

Local population density and group composition influence the signal-preference relationship in Enchenopa treehoppers (Hemiptera: Membracidae).

PubMed

Fowler-Finn, K D; Cruz, D C; Rodríguez, R L

2017-01-01

Many animals exhibit social plasticity - changes in phenotype or behaviour in response to experience with conspecifics that change how evolutionary processes like sexual selection play out. Here, we asked whether social plasticity arising from variation in local population density in male advertisement signals and female mate preferences influences the form of sexual selection. We manipulated local density and determined whether this changed how the distribution of male signals overlapped with female preferences - the signal preference relationship. We specifically look at the shape of female mate preference functions, which, when compared to signal distributions, provide hypotheses about the form of sexual selection. We used Enchenopa binotata treehoppers, a group of plant-feeding insects that exhibit natural variation in local densities across individual host plants, populations, species and years. We measured male signal frequency and female preference functions across the density treatments. We found that male signals varied across local social groups, but not according to local density. By contrast, female preferences varied with local density - favouring higher signal frequencies in denser environments. Thus, local density changes the signal-preference relationship and, consequently, the expected form of sexual selection. We found no influence of sex ratio on the signal-preference relationship. Our findings suggest that plasticity arising from variation in local group density and composition can alter the form of sexual selection with potentially important consequences both for the maintenance of variation and for speciation. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

Phenology of Scramble Polygyny in a Wild Population of Chrysolemid Beetles: The Opportunity for and the Strength of Sexual Selection

PubMed Central

Baena, Martha Lucía; Macías-Ordóñez, Rogelio

2012-01-01

Recent debate has highlighted the importance of estimating both the strength of sexual selection on phenotypic traits, and the opportunity for sexual selection. We describe seasonal fluctuations in mating dynamics of Leptinotarsa undecimlineata (Coleoptera: Chrysomelidae). We compared several estimates of the opportunity for, and the strength of, sexual selection and male precopulatory competition over the reproductive season. First, using a null model, we suggest that the ratio between observed values of the opportunity for sexual selections and their expected value under random mating results in unbiased estimates of the actual nonrandom mating behavior of the population. Second, we found that estimates for the whole reproductive season often misrepresent the actual value at any given time period. Third, mating differentials on male size and mobility, frequency of male fighting and three estimates of the opportunity for sexual selection provide contrasting but complementary information. More intense sexual selection associated to male mobility, but not to male size, was observed in periods with high opportunity for sexual selection and high frequency of male fights. Fourth, based on parameters of spatial and temporal aggregation of female receptivity, we describe the mating system of L. undecimlineata as a scramble mating polygyny in which the opportunity for sexual selection varies widely throughout the season, but the strength of sexual selection on male size remains fairly weak, while male mobility inversely covaries with mating success. We suggest that different estimates for the opportunity for, and intensity of, sexual selection should be applied in order to discriminate how different behavioral and demographic factors shape the reproductive dynamic of populations. PMID:22761675

Sexual harassment induces a temporary fitness cost but does not constrain the acquisition of environmental information in fruit flies.

PubMed

Teseo, Serafino; Veerus, Liisa; Moreno, Céline; Mery, Frédéric

2016-01-01

Across animals, sexual harassment induces fitness costs for females and males. However, little is known about the cognitive costs involved, i.e. whether it constrains learning processes, which could ultimately affect an individual's fitness. Here we evaluate the acquisition of environmental information in groups of fruit flies challenged with various levels of male sexual harassment. We show that, although high sexual harassment induces a temporary fitness cost for females, all fly groups of both sexes exhibit similar levels of learning. This suggests that, in fruit flies, the fitness benefits of acquiring environmental information are not affected by the fitness costs of sexual harassment, and that selection may favour cognition even in unfavourable social contexts. Our study provides novel insights into the relationship between sexual conflicts and cognition and the evolution of female counterstrategies against male sexual harassment. © 2016 The Author(s).

"I Don't Shag Dirty Girls": Marginalized Masculinities and the Use of Partner Selection as a Sexual Health Risk Reduction Strategy in Heterosexual Young Men.

PubMed

Limmer, Mark

2016-03-01

Understanding and addressing the sexual risk taking of young men remains a key research, policy, and practice concern in attempts to improve the emotional and physical sexual health of young men and their sexual partners. This article explores one of the ways in which young men attempt to mitigate sexual risk through the assigning of labels to particular young women and using these as a basis for their decisions in relation to sexual activity, contraception, and condom use. The article uses the lens of hegemonic masculinities theory to increase understanding of the role played by the construction and performance of marginalized masculinities and how these in turn are influenced by social exclusionary processes. The article draws on focus group and interview data from 46 young men aged 15 to 17 years living in the northwest of England, purposively selected on the basis of the prevailing policy definitions of social inclusion and exclusion. The article describes a form of marginalized masculinity pertaining to socially excluded young men, which as a result of limited access to other tenets of hegemonic masculinity, is disproportionately reliant on sexual expertise and voracity alongside overt demonstrations of their superiority over women. It is in this context that young women are assigned the labels of "dirty" or "clean" on the basis of a selection of arbitrary judgments relating to dress, demeanor, area of residence, and perceived sexual activities. The motivations of the young men, the impact on young women, and the policy and practice implications are all discussed. © The Author(s) 2014.

The evolution of sexual size dimorphism in the house finch. II. Population divergence in relation to local selection.

PubMed

Badyaev, A V; Hill, G E; Stoehr, A M; Nolan, P M; McGraw, K J

2000-12-01

Recent colonization of ecologically distinct areas in North America by the house finch (Carpodacus mexicanus) was accompanied by strong population divergence in sexual size dimorphism. Here we examined whether this divergence was produced by population differences in local selection pressures acting on each sex. In a long-term study of recently established populations in Alabama, Michigan, and Montana, we examined three selection episodes for each sex: selection for pairing success, overwinter survival, and within-season fecundity. Populations varied in intensity of these selection episodes, the contribution of each episode to the net selection, and in the targets of selection. Direction and intensity of selection strongly differed between sexes, and different selection episodes often favored opposite changes in morphological traits. In each population, current net selection for sexual dimorphism was highly concordant with observed sexual dimorphism--in each population, selection for dimorphism was the strongest on the most dimorphic traits. Strong directional selection on sexually dimorphic traits, and similar intensities of selection in both sexes, suggest that in each of the recently established populations, both males and females are far from their local fitness optimum, and that sexual dimorphism has arisen from adaptive responses in both sexes. Population differences in patterns of selection on dimorphism, combined with both low levels of ontogenetic integration in heritable sexually dimorphic traits and sexual dimorphism in growth patterns, may account for the close correspondence between dimorphism in selection and observed dimorphism in morphology across house finch populations.

Natural selection stops the evolution of male attractiveness

PubMed Central

Hine, Emma; McGuigan, Katrina; Blows, Mark W.

2011-01-01

Sexual selection in natural populations acts on highly heritable traits and tends to be relatively strong, implicating sexual selection as a causal agent in many phenotypic radiations. Sexual selection appears to be ineffectual in promoting phenotypic divergence among contemporary natural populations, however, and there is little evidence from artificial selection experiments that sexual fitness can evolve. Here, we demonstrate that a multivariate male trait preferred by Drosophila serrata females can respond to selection and results in the maintenance of male mating success. The response to selection was associated with a gene of major effect increasing in frequency from 12 to 35% in seven generations. No further response to selection, or increase in frequency of the major gene, was observed between generations 7 and 11, indicating an evolutionary limit had been reached. Genetic analyses excluded both depletion of genetic variation and overdominance as causes of the evolutionary limit. Relaxing artificial selection resulted in the loss of 52% of the selection response after a further five generations, demonstrating that the response under artificial sexual selection was opposed by antagonistic natural selection. We conclude that male D. serrata sexually selected traits, and attractiveness to D. serrata females conferred by these traits, were held at an evolutionary limit by the lack of genetic variation that would allow an increase in sexual fitness while simultaneously maintaining nonsexual fitness. Our results suggest that sexual selection is unlikely to cause divergence among natural populations without a concomitant change in natural selection, a conclusion consistent with observational evidence from natural populations. PMID:21321197

Quantifying Variability of Avian Colours: Are Signalling Traits More Variable?

PubMed Central

Delhey, Kaspar; Peters, Anne

2008-01-01

Background Increased variability in sexually selected ornaments, a key assumption of evolutionary theory, is thought to be maintained through condition-dependence. Condition-dependent handicap models of sexual selection predict that (a) sexually selected traits show amplified variability compared to equivalent non-sexually selected traits, and since males are usually the sexually selected sex, that (b) males are more variable than females, and (c) sexually dimorphic traits more variable than monomorphic ones. So far these predictions have only been tested for metric traits. Surprisingly, they have not been examined for bright coloration, one of the most prominent sexual traits. This omission stems from computational difficulties: different types of colours are quantified on different scales precluding the use of coefficients of variation. Methodology/Principal Findings Based on physiological models of avian colour vision we develop an index to quantify the degree of discriminable colour variation as it can be perceived by conspecifics. A comparison of variability in ornamental and non-ornamental colours in six bird species confirmed (a) that those coloured patches that are sexually selected or act as indicators of quality show increased chromatic variability. However, we found no support for (b) that males generally show higher levels of variability than females, or (c) that sexual dichromatism per se is associated with increased variability. Conclusions/Significance We show that it is currently possible to realistically estimate variability of animal colours as perceived by them, something difficult to achieve with other traits. Increased variability of known sexually-selected/quality-indicating colours in the studied species, provides support to the predictions borne from sexual selection theory but the lack of increased overall variability in males or dimorphic colours in general indicates that sexual differences might not always be shaped by similar selective forces. PMID:18301766

Sexual networks: measuring sexual selection in structured, polyandrous populations.

PubMed

McDonald, Grant C; James, Richard; Krause, Jens; Pizzari, Tommaso

2013-03-05

Sexual selection is traditionally measured at the population level, assuming that populations lack structure. However, increasing evidence undermines this approach, indicating that intrasexual competition in natural populations often displays complex patterns of spatial and temporal structure. This complexity is due in part to the degree and mechanisms of polyandry within a population, which can influence the intensity and scale of both pre- and post-copulatory sexual competition. Attempts to measure selection at the local and global scale have been made through multi-level selection approaches. However, definitions of local scale are often based on physical proximity, providing a rather coarse measure of local competition, particularly in polyandrous populations where the local scale of pre- and post-copulatory competition may differ drastically from each other. These limitations can be solved by social network analysis, which allows us to define a unique sexual environment for each member of a population: 'local scale' competition, therefore, becomes an emergent property of a sexual network. Here, we first propose a novel quantitative approach to measure pre- and post-copulatory sexual selection, which integrates multi-level selection with information on local scale competition derived as an emergent property of networks of sexual interactions. We then use simple simulations to illustrate the ways in which polyandry can impact estimates of sexual selection. We show that for intermediate levels of polyandry, the proposed network-based approach provides substantially more accurate measures of sexual selection than the more traditional population-level approach. We argue that the increasing availability of fine-grained behavioural datasets provides exciting new opportunities to develop network approaches to study sexual selection in complex societies.

Sexual selection in hermaphrodites, sperm and broadcast spawners, plants and fungi

PubMed Central

Ortiz-Barrientos, Daniel

2016-01-01

Darwin was the first to recognize that sexual selection is a strong evolutionary force. Exaggerated traits allow same-sex individuals to compete over access to mates and provide a mechanism by which mates are selected. It is relatively easy to appreciate how inter- and intrasexual selection work in organisms with the sensory capabilities to perceive physical or behavioural traits that signal mate quality or mate compatibility, and to assess the relative quality of competitors. It is therefore not surprising that most studies of sexual selection have focused on animals with separate sexes and obvious adaptations that function in the context of reproductive competition. Yet, many sexual organisms are both male and female at the same time, often lack sexual dimorphism and never come into direct contact at mating. How does sexual selection act in such species, and what can we learn from them? Here, we address these questions by exploring the potential for sexual selection in simultaneous hermaphrodites, sperm- and broadcast spawners, plants and fungi. Our review reveals a range of mechanisms of sexual selection, operating primarily after gametes have been released, which are common in many of these groups and also quite possibly in more familiar (internally fertilizing and sexually dimorphic) organisms. This article is part of the themed issue ‘Weird sex: the underappreciated diversity of sexual reproduction’. PMID:27619704

Sexual selection in hermaphrodites, sperm and broadcast spawners, plants and fungi.

PubMed

Beekman, Madeleine; Nieuwenhuis, Bart; Ortiz-Barrientos, Daniel; Evans, Jonathan P

2016-10-19

Darwin was the first to recognize that sexual selection is a strong evolutionary force. Exaggerated traits allow same-sex individuals to compete over access to mates and provide a mechanism by which mates are selected. It is relatively easy to appreciate how inter- and intrasexual selection work in organisms with the sensory capabilities to perceive physical or behavioural traits that signal mate quality or mate compatibility, and to assess the relative quality of competitors. It is therefore not surprising that most studies of sexual selection have focused on animals with separate sexes and obvious adaptations that function in the context of reproductive competition. Yet, many sexual organisms are both male and female at the same time, often lack sexual dimorphism and never come into direct contact at mating. How does sexual selection act in such species, and what can we learn from them? Here, we address these questions by exploring the potential for sexual selection in simultaneous hermaphrodites, sperm- and broadcast spawners, plants and fungi. Our review reveals a range of mechanisms of sexual selection, operating primarily after gametes have been released, which are common in many of these groups and also quite possibly in more familiar (internally fertilizing and sexually dimorphic) organisms.This article is part of the themed issue 'Weird sex: the underappreciated diversity of sexual reproduction'. © 2016 The Author(s).

Ecological constraint and the evolution of sexual dichromatism in darters.

PubMed

Bossu, Christen M; Near, Thomas J

2015-05-01

It is not known how environmental pressures and sexual selection interact to influence the evolution of extravagant male traits. Sexual and natural selection are often viewed as antagonistic forces shaping the evolution of visual signals, where conspicuousness is favored by sexual selection and crypsis is favored by natural selection. Although typically investigated independently, the interaction between natural and sexual selection remains poorly understood. Here, we investigate whether sexual dichromatism evolves stochastically, independent from, or in concert with habitat use in darters, a species-rich lineage of North American freshwater fish. We find the evolution of sexual dichromatism is coupled to habitat use in darter species. Comparative analyses reveal that mid-water darter lineages exhibit a narrow distribution of dichromatism trait space surrounding a low optimum, suggesting a constraint imposed on the evolution of dichromatism, potentially through predator-mediated selection. Alternatively, the transition to benthic habitats coincides with greater variability in the levels of dichromatism that surround a higher optimum, likely due to relaxation of the predator-mediated selection and heterogeneous microhabitat dependent selection regimes. These results suggest a complex interaction of sexual selection with potentially two mechanisms of natural selection, predation and sensory drive, that influence the evolution of diverse male nuptial coloration in darters. © 2015 The Author(s).

Sexual selection and allometry: a critical reappraisal of the evidence and ideas.

PubMed

Bonduriansky, Russell

2007-04-01

One of the most pervasive ideas in the sexual selection literature is the belief that sexually selected traits almost universally exhibit positive static allometries (i.e., within a sample of conspecific adults, larger individuals have disproportionally larger traits). In this review, I show that this idea is contradicted by empirical evidence and theory. Although positive allometry is a typical attribute of some sexual traits in certain groups, the preponderance of positively allometric sexual traits in the empirical literature apparently results from a sampling bias reflecting a fascination with unusually exaggerated (bizarre) traits. I review empirical examples from a broad range of taxa illustrating the diversity of allometric patterns exhibited by signal, weapon, clasping and genital traits, as well as nonsexual traits. This evidence suggests that positive allometry may be the exception rather than the rule in sexual traits, that directional sexual selection does not necessarily lead to the evolution of positive allometry and, conversely, that positive allometry is not necessarily a consequence of sexual selection, and that many sexual traits exhibit sex differences in allometric intercept rather than slope. Such diversity in the allometries of secondary sexual traits is to be expected, given that optimal allometry should reflect resource allocation trade-offs, and patterns of sexual and viability selection on both trait size and body size. An unbiased empirical assessment of the relation between sexual selection and allometry is an essential step towards an understanding of this diversity.

The genetic basis of traits regulating sperm competition and polyandry: can selection favour the evolution of good- and sexy-sperm?

PubMed

Evans, Jonathan P; Simmons, Leigh W

2008-09-01

The good-sperm and sexy-sperm (GS-SS) hypotheses predict that female multiple mating (polyandry) can fuel sexual selection for heritable male traits that promote success in sperm competition. A major prediction generated by these models, therefore, is that polyandry will benefit females indirectly via their sons' enhanced fertilization success. Furthermore, like classic 'good genes' and 'sexy son' models for the evolution of female preferences, GS-SS processes predict a genetic correlation between genes for female mating frequency (analogous to the female preference) and those for traits influencing fertilization success (the sexually selected traits). We examine the premise for these predictions by exploring the genetic basis of traits thought to influence fertilization success and female mating frequency. We also highlight recent debates that stress the possible genetic constraints to evolution of traits influencing fertilization success via GS-SS processes, including sex-linked inheritance, nonadditive effects, interacting parental genotypes, and trade-offs between integrated ejaculate components. Despite these possible constraints, the available data suggest that male traits involved in sperm competition typically exhibit substantial additive genetic variance and rapid evolutionary responses to selection. Nevertheless, the limited data on the genetic variation in female mating frequency implicate strong genetic maternal effects, including X-linkage, which is inconsistent with GS-SS processes. Although the relative paucity of studies on the genetic basis of polyandry does not allow us to draw firm conclusions about the evolutionary origins of this trait, the emerging pattern of sex linkage in genes for polyandry is more consistent with an evolutionary history of antagonistic selection over mating frequency. We advocate further development of GS-SS theory to take account of the complex evolutionary dynamics imposed by sexual conflict over mating frequency.

Using theories of sexual selection and sexual conflict to improve our understanding of plant ecology and evolution

PubMed Central

Lankinen, Åsa; Karlsson Green, Kristina

2015-01-01

Today it is accepted that the theories of sexual selection and sexual conflict are general and can be applied to both animals and plants. However, potentially due to a controversial history, plant studies investigating sexual selection and sexual conflict are relatively rare. Moreover, these theories and concepts are seldom implemented in research fields investigating related aspects of plant ecology and evolution. Even though these theories are complex, and can be difficult to study, we suggest that several fields in plant biology would benefit from incorporating and testing the impact of selection pressures generated by sexual selection and sexual conflict. Here we give examples of three fields where we believe such incorporation would be particularly fruitful, including (i) mechanisms of pollen–pistil interactions, (ii) mating-system evolution in hermaphrodites and (iii) plant immune responses to pests and pathogens. PMID:25613227

Sensory exploitation and sexual conflict

PubMed Central

Arnqvist, Göran

2006-01-01

Much of the literature on male–female coevolution concerns the processes by which male traits and female preferences for these can coevolve and be maintained by selection. There has been less explicit focus on the origin of male traits and female preferences. Here, I argue that it is important to distinguish origin from subsequent coevolution and that insights into the origin can help us appreciate the relative roles of various coevolutionary processes for the evolution of diversity in sexual dimorphism. I delineate four distinct scenarios for the origin of male traits and female preferences that build on past contributions, two of which are based on pre-existing variation in quality indicators among males and two on exploitation of pre-existing sensory biases among females. Recent empirical research, and theoretical models, suggest that origin by sensory exploitation has been widespread. I argue that this points to a key, but perhaps transient, role for sexually antagonistic coevolution (SAC) in the subsequent evolutionary elaboration of sexual traits, because (i) sensory exploitation is often likely to be initially costly for individuals of the exploited sex and (ii) the subsequent evolution of resistance to sensory exploitation should often be associated with costs due to selective constraints. A review of a few case studies is used to illustrate these points. Empirical data directly relevant to the costs of being sensory exploited and the costs of evolving resistance is largely lacking, and I stress that such data would help determining the general importance of sexual conflict and SAC for the evolution of sexual dimorphism. PMID:16612895

Darwin's forgotten idea: the social essence of sexual selection.

PubMed

West-Eberhard, Mary Jane

2014-10-01

Darwinian sexual selection can now be seen in the broader context of social selection, or social competition for resources (under sexual selection, mates or fertilization success). The social-interaction aspects of sexually selected traits give them special evolutionary properties of interest for neurobiological studies of stimulus-response systems because they can account for highly complex systems with little information content other than stimulatory effectiveness per se. But these special properties have a long history of being forgotten when other factors dominate the analysis of male-female interactions, such as the mistaken belief that differential responsiveness to signals produced by competing rivals ("female choice") requires an esthetic sense; that species recognition explains all species-specific sexual signals; and, more recently, that successful signals must reflect good survival genes; or that male-female conflict involves female resistance rather than stimulus evaluation. A "conflict paradox" results when male-female conflict is seen as driven by natural selection, whose costs should often move the hypothesized "sexually antagonistic co-evolution" of sensory-response systems toward the powerful domain of sexually synergistic co-evolution under sexual selection. Special properties of sexual selection apply to other forms of social competition as well, showing the wisdom of Darwin's setting it apart from natural selection as an explanation of many otherwise puzzling and extreme traits. Copyright © 2014. Published by Elsevier Ltd.

The relationship between sexual selection and sexual conflict.

PubMed

Kokko, Hanna; Jennions, Michael D

2014-07-18

Evolutionary conflicts of interest arise whenever genetically different individuals interact and their routes to fitness maximization differ. Sexual selection favors traits that increase an individual's competitiveness to acquire mates and fertilizations. Sexual conflict occurs if an individual of sex A's relative fitness would increase if it had a "tool" that could alter what an individual of sex B does (including the parental genes transferred), at a cost to B's fitness. This definition clarifies several issues: Conflict is very common and, although it extends outside traits under sexual selection, sexual selection is a ready source of sexual conflict. Sexual conflict and sexual selection should not be presented as alternative explanations for trait evolution. Conflict is closely linked to the concept of a lag load, which is context-dependent and sex-specific. This makes it possible to ask if one sex can "win." We expect higher population fitness if females win. Copyright © 2014 Cold Spring Harbor Laboratory Press; all rights reserved.

Sexual selection and the adaptive evolution of PKDREJ protein in primates and rodents

PubMed Central

Vicens, Alberto; Gómez Montoto, Laura; Couso-Ferrer, Francisco; Sutton, Keith A.; Roldan, Eduardo R.S.

2015-01-01

PKDREJ is a testis-specific protein thought to be located on the sperm surface. Functional studies in the mouse revealed that loss of PKDREJ has effects on sperm transport and the ability to undergo an induced acrosome reaction. Thus, PKDREJ has been considered a potential target of post-copulatory sexual selection in the form of sperm competition. Proteins involved in reproductive processes often show accelerated evolution. In many cases, this rapid divergence is promoted by positive selection which may be driven, at least in part, by post-copulatory sexual selection. We analysed the evolution of the PKDREJ protein in primates and rodents and assessed whether PKDREJ divergence is associated with testes mass relative to body mass, which is a reliable proxy of sperm competition levels. Evidence of an association between the evolutionary rate of the PKDREJ gene and testes mass relative to body mass was not found in primates. Among rodents, evidence of positive selection was detected in the Pkdrej gene in the family Cricetidae but not in Muridae. We then assessed whether Pkdrej divergence is associated with episodes of sperm competition in these families. We detected a positive significant correlation between the evolutionary rates of Pkdrej and testes mass relative to body mass in cricetids. These findings constitute the first evidence of post-copulatory sexual selection influencing the evolution of a protein that participates in the mechanisms regulating sperm transport and the acrosome reaction, strongly suggesting that positive selection may act on these fertilization steps, leading to advantages in situations of sperm competition. PMID:25304980

A lateralized functional auditory network is involved in anuran sexual selection.

PubMed

Xue, Fei; Fang, Guangzhan; Yue, Xizi; Zhao, Ermi; Brauth, Steven E; Tang, Yezhong

2016-12-01

Right ear advantage (REA) exists in many land vertebrates in which the right ear and left hemisphere preferentially process conspecific acoustic stimuli such as those related to sexual selection. Although ecological and neural mechanisms for sexual selection have been widely studied, the brain networks involved are still poorly understood. In this study we used multi-channel electroencephalographic data in combination with Granger causal connectivity analysis to demonstrate, for the first time, that auditory neural network interconnecting the left and right midbrain and forebrain function asymmetrically in the Emei music frog (Babina daunchina), an anuran species which exhibits REA. The results showed the network was lateralized. Ascending connections between the mesencephalon and telencephalon were stronger in the left side while descending ones were stronger in the right, which matched with the REA in this species and implied that inhibition from the forebrainmay induce REA partly. Connections from the telencephalon to ipsilateral mesencephalon in response to white noise were the highest in the non-reproductive stage while those to advertisement calls were the highest in reproductive stage, implying the attention resources and living strategy shift when entered the reproductive season. Finally, these connection changes were sexually dimorphic, revealing sex differences in reproductive roles.

Postmating sexual selection: allopatric evolution of sperm competition mechanisms and genital morphology in calopterygid damselflies (Insecta: Odonata).

PubMed

Cordero Rivera, A; Andrés, J A; Córdoba-Aguilar, A; Utzeri, C

2004-02-01

Postmating sexual selection theory predicts that in allopatry reproductive traits diverge rapidly and that the resulting differentiation in these traits may lead to restrictions to gene flow between populations and, eventually, reproductive isolation. In this paper we explore the potential for this premise in a group of damselflies of the family Calopterygidae, in which postmating sexual mechanisms are especially well understood. Particularly, we tested if in allopatric populations the sperm competition mechanisms and genitalic traits involved in these mechanisms have indeed diverged as sexual selection theory predicts. We did so in two different steps. First, we compared the sperm competition mechanisms of two allopatric populations of Calopteryx haemorrhoidalis (one Italian population studied here and one Spanish population previously studied). Our results indicate that in both populations males are able to displace spermathecal sperm, but the mechanism used for sperm removal between both populations is strikingly different. In the Spanish population males seem to empty the spermathecae by stimulating females, whereas in the Italian population males physically remove sperm from the spermathecae. Both populations also exhibit differences in genital morphometry that explain the use of different mechanisms: the male lateral processes are narrower than the spermathecal ducts in the Italian population, which is the reverse in the Spanish population. The estimated degree of phenotypic differentiation between these populations based on the genitalic traits involved in sperm removal was much greater than the differentiation based on a set of other seven morphological variables, suggesting that strong directional postmating sexual selection is indeed the main evolutionary force behind the reproductive differentiation between the studied populations. In a second step, we examined if a similar pattern in genital morphometry emerge in allopatric populations of this and other three species of the same family (Calopteryx splendens, C. virgo and Hetaerina cruentata). Our results suggest that there is geographic variation in the sperm competition mechanisms in all four studied species. Furthermore, genitalic morphology was significantly divergent between populations within species even when different populations were using the same copulatory mechanism. These results can be explained by probable local coadaptation processes that have given rise to an ability or inability to reach and displace spermathecal sperm in different populations. This set of results provides the first direct evidence of intraspecific evolution of genitalic traits shaped by postmating sexual selection.

Sexual dichromatism in frogs: natural selection, sexual selection and unexpected diversity.

PubMed

Bell, Rayna C; Zamudio, Kelly R

2012-12-07

Sexual dichromatism, a form of sexual dimorphism in which males and females differ in colour, is widespread in animals but has been predominantly studied in birds, fishes and butterflies. Moreover, although there are several proposed evolutionary mechanisms for sexual dichromatism in vertebrates, few studies have examined this phenomenon outside the context of sexual selection. Here, we describe unexpectedly high diversity of sexual dichromatism in frogs and create a comparative framework to guide future analyses of the evolution of these sexual colour differences. We review what is known about evolution of colour dimorphism in frogs, highlight alternative mechanisms that may contribute to the evolution of sexual colour differences, and compare them to mechanisms active in other major groups of vertebrates. In frogs, sexual dichromatism can be dynamic (temporary colour change in males) or ontogenetic (permanent colour change in males or females). The degree and the duration of sexual colour differences vary greatly across lineages, and we do not detect phylogenetic signal in the distribution of this trait, therefore frogs provide an opportunity to investigate the roles of natural and sexual selection across multiple independent derivations of sexual dichromatism.

Promiscuity drives sexual selection in a socially monogamous bird.

PubMed

Webster, Michael S; Tarvin, Keith A; Tuttle, Elaina M; Pruett-Jones, Stephen

2007-09-01

Many socially monogamous species paradoxically show signs of strong sexual selection, suggesting cryptic sources of sexual competition among males. Darwin argued that sexual selection could operate in monogamous systems if breeding sex ratios are biased or if some males attract highly fecund females. Alternatively, sexual selection might result from promiscuous copulations outside the pair bond, although several recent studies have cast doubt on this possibility, in particular by showing that variance in apparent male reproductive success (number of social young) differs little from variance in actual male reproductive success (number of young sired). Our results from a long-term study of the socially monogamous splendid fairy-wren (Malurus splendens) demonstrate that such comparisons are misleading and do not adequately assess the effects of extra-pair paternity (EPP). By partitioning the opportunity for selection and calculating Bateman gradients, we show that EPP has a strong effect on male annual and lifetime fitness, whereas other proposed mechanisms of sexual selection do not. Thus, EPP drives sexual selection in this, and possibly other, socially monogamous species.

Sexual selection gradients change over time in a simultaneous hermaphrodite

PubMed Central

Hoffer, Jeroen NA; Mariën, Janine; Ellers, Jacintha; Koene, Joris M

2017-01-01

Sexual selection is generally predicted to act more strongly on males than on females. The Darwin-Bateman paradigm predicts that this should also hold for hermaphrodites. However, measuring this strength of selection is less straightforward when both sexual functions are performed throughout the organism’s lifetime. Besides, quantifications of sexual selection are usually done during a short time window, while many animals store sperm and are long-lived. To explore whether the chosen time frame affects estimated measures of sexual selection, we recorded mating success and reproductive success over time, using a simultaneous hermaphrodite. Our results show that male sexual selection gradients are consistently positive. However, an individual’s female mating success seems to negatively affect its own male reproductive success, an effect that only becomes visible several weeks into the experiment, highlighting that the time frame is crucial for the quantification and interpretation of sexual selection measures, an insight that applies to any iteroparous mating system. DOI: http://dx.doi.org/10.7554/eLife.25139.001 PMID:28613158

Mate choice and sexual selection: What have we learned since Darwin?

PubMed Central

Jones, Adam G.; Ratterman, Nicholas L.

2009-01-01

Charles Darwin laid the foundation for all modern work on sexual selection in his seminal book The Descent of Man, and Selection in Relation to Sex. In this work, Darwin fleshed out the mechanism of sexual selection, a hypothesis that he had proposed in The Origin of Species. He went well beyond a simple description of the phenomenon by providing extensive evidence and considering the far-reaching implications of the idea. Here we consider the contributions of Darwin to sexual selection with a particular eye on how far we have progressed in the last 150 years. We focus on 2 key questions in sexual selection. First, why does mate choice evolve at all? And second, what factors determine the strength of mate choice (or intensity of sexual selection) in each sex? Darwin provided partial answers to these questions, and the progress that has been made on both of these topics since his time should be seen as one of the great triumphs of modern evolutionary biology. However, a review of the literature shows that key aspects of sexual selection are still plagued by confusion and disagreement. Many of these areas are complex and will require new theory and empirical data for complete resolution. Overall, Darwin's contributions are still surprisingly relevant to the modern study of sexual selection, so students of evolutionary biology would be well advised to revisit his works. Although we have made significant progress in some areas of sexual selection research, we still have much to accomplish. PMID:19528643

Mate choice and sexual selection: what have we learned since Darwin?

PubMed

Jones, Adam G; Ratterman, Nicholas L

2009-06-16

Charles Darwin laid the foundation for all modern work on sexual selection in his seminal book The Descent of Man, and Selection in Relation to Sex. In this work, Darwin fleshed out the mechanism of sexual selection, a hypothesis that he had proposed in The Origin of Species. He went well beyond a simple description of the phenomenon by providing extensive evidence and considering the far-reaching implications of the idea. Here we consider the contributions of Darwin to sexual selection with a particular eye on how far we have progressed in the last 150 years. We focus on 2 key questions in sexual selection. First, why does mate choice evolve at all? And second, what factors determine the strength of mate choice (or intensity of sexual selection) in each sex? Darwin provided partial answers to these questions, and the progress that has been made on both of these topics since his time should be seen as one of the great triumphs of modern evolutionary biology. However, a review of the literature shows that key aspects of sexual selection are still plagued by confusion and disagreement. Many of these areas are complex and will require new theory and empirical data for complete resolution. Overall, Darwin's contributions are still surprisingly relevant to the modern study of sexual selection, so students of evolutionary biology would be well advised to revisit his works. Although we have made significant progress in some areas of sexual selection research, we still have much to accomplish.

Implications of sex-specific selection for the genetic basis of disease.

PubMed

Morrow, Edward H; Connallon, Tim

2013-12-01

Mutation and selection are thought to shape the underlying genetic basis of many common human diseases. However, both processes depend on the context in which they occur, such as environment, genetic background, or sex. Sex has widely known effects on phenotypic expression of genotype, but an analysis of how it influences the evolutionary dynamics of disease-causing variants has not yet been explored. We develop a simple population genetic model of disease susceptibility and evaluate it using a biologically plausible empirically based distribution of fitness effects among contributing mutations. The model predicts that alleles under sex-differential selection, including sexually antagonistic alleles, will disproportionately contribute to genetic variation for disease predisposition, thereby generating substantial sexual dimorphism in the genetic architecture of complex (polygenic) diseases. This is because such alleles evolve into higher population frequencies for a given effect size, relative to alleles experiencing equally strong purifying selection in both sexes. Our results provide a theoretical justification for expecting a sexually dimorphic genetic basis for variation in complex traits such as disease. Moreover, they suggest that such dimorphism is interesting - not merely something to control for - because it reflects the action of natural selection in molding the evolution of common disease phenotypes.

Selective influence of the menstrual cycle on perception of stimuli with reproductive significance: an event-related potential study.

PubMed

Krug, R; Plihal, W; Fehm, H L; Born, J

2000-01-01

In this study, we examined changes in the event-related potential (ERP) to stimuli with and without reproductive significance occurring during the menstrual cycle. Eleven spontaneously cycling women were tested during three menstrual phases (menses, ovulatory phase, luteal phase) differing in plasma concentrations of gonadal hormones. ERPs were recorded while subjects were presented with slides showing pictures from four different stimulus categories (sexual stimuli, babies, people occupied with body care, ordinary people). Slides were presented randomly in the context of two tasks, requiring either affective processing (i.e., to judge the emotional content of a slide as positive, neutral, or negative) or structural processing (i.e., to estimate the number of parallel thin lines inserted in each picture). Menstrual phase primarily affected a late positive component (LPC) peaking 550-600 ms poststimulus. The effects were as follows: (i) During the ovulatory phase, amplitude of the LPC to sexual stimuli was larger than that evoked by the other stimulus categories. (ii) This relationship was not apparent during the other menstrual phases or (iii) during the ovulatory phase when the task required structural processing. The ovulatory increase in LPC positivity to sexual stimuli suggests a greater valence of these stimuli during a phase of increased sexual desire. The data indicate a specific effect of the menstrual cycle on the processing of sexual stimuli that increases with deeper emotional processing.

Exploring gene-culture interactions: insights from handedness, sexual selection and niche-construction case studies.

PubMed

Laland, Kevin N

2008-11-12

Genes and culture represent two streams of inheritance that for millions of years have flowed down the generations and interacted. Genetic propensities, expressed throughout development, influence what cultural organisms learn. Culturally transmitted information, expressed in behaviour and artefacts, spreads through populations, modifying selection acting back on populations. Drawing on three case studies, I will illustrate how this gene-culture coevolution has played a critical role in human evolution. These studies explore (i) the evolution of handedness, (ii) sexual selection with a culturally transmitted mating preference, and (iii) cultural niche construction and human evolution. These analyses shed light on how genes and culture shape each other, and on the significance of feedback mechanisms between biological and cultural processes.

Interactions among mechanisms of sexual selection on male body size and head shape in a sexually dimorphic fly.

PubMed

Bonduriansky, Russell; Rowe, Locke

2003-09-01

Darwin envisaged male-male and male-female interactions as mutually supporting mechanisms of sexual selection, in which the best armed males were also the most attractive to females. Although this belief continues to predominate today, it has been challenged by sexual conflict theory, which suggests that divergence in the interests of males and females may result in conflicting sexual selection. This raises the empirical question of how multiple mechanisms of sexual selection interact to shape targeted traits. We investigated sexual selection on male morphology in the sexually dimorphic fly Prochyliza xanthostoma, using indices of male performance in male-male and male-female interactions in laboratory arenas to calculate gradients of direct, linear selection on male body size and an index of head elongation. In male-male combat, the first interaction with a new opponent selected for large body size but reduced head elongation, whereas multiple interactions with the same opponent favored large body size only. In male-female interactions, females preferred males with relatively elongated heads, but male performance of the precopulatory leap favored large body size and, possibly, reduced head elongation. In addition, the amount of sperm transferred (much of which is ingested by females) was an increasing function of both body size and head elongation. Thus, whereas both male-male and male-female interactions favored large male body size, male head shape appeared to be subject to conflicting sexual selection. We argue that conflicting sexual selection may be a common result of divergence in the interests of the sexes.

Does dorsolateral prefrontal cortex (DLPFC) activation return to baseline when sexual stimuli cease? The role of DLPFC in visual sexual stimulation.

PubMed

Leon-Carrion, Jose; Martín-Rodríguez, Juan Francisco; Damas-López, Jesús; Pourrezai, Kambiz; Izzetoglu, Kurtulus; Barroso Y Martin, Juan Manuel; Dominguez-Morales, M Rosario

2007-04-06

A fundamental question in human sexuality regards the neural substrate underlying sexually-arousing representations. Lesion and neuroimaging studies suggest that dorsolateral pre-frontal cortex (DLPFC) plays an important role in regulating the processing of visual sexual stimulation. The aim of this Functional Near-Infrared Spectroscopy (fNIRS) study was to explore DLPFC structures involved in the processing of erotic and non-sexual films. fNIRS was used to image the evoked-cerebral blood oxygenation (CBO) response in 15 male and 15 female subjects. Our hypothesis is that a sexual stimulus would produce DLPFC activation during the period of direct stimulus perception ("on" period), and that this activation would continue after stimulus cessation ("off" period). A new paradigm was used to measure the relative oxygenated hemoglobin (oxyHb) concentrations in DLPFC while subjects viewed the two selected stimuli (Roman orgy and a non-sexual film clip), and also immediately following stimulus cessation. Viewing of the non-sexual stimulus produced no overshoot in DLPFC, whereas exposure to the erotic stimulus produced rapidly ascendant overshoot, which became even more pronounced following stimulus cessation. We also report on gender differences in the timing and intensity of DLPFC activation in response to a sexually explicit visual stimulus. We found evidence indicating that men experience greater and more rapid sexual arousal when exposed to erotic stimuli than do women. Our results point out that self-regulation of DLPFC activation is modulated by subjective arousal and that cognitive appraisal of the sexual stimulus (valence) plays a secondary role in this regulation.

Diversifying Selection Between Pure-Breed and Free-Breeding Dogs Inferred from Genome-Wide SNP Analysis.

PubMed

Pilot, Małgorzata; Malewski, Tadeusz; Moura, Andre E; Grzybowski, Tomasz; Oleński, Kamil; Kamiński, Stanisław; Fadel, Fernanda Ruiz; Alagaili, Abdulaziz N; Mohammed, Osama B; Bogdanowicz, Wiesław

2016-08-09

Domesticated species are often composed of distinct populations differing in the character and strength of artificial and natural selection pressures, providing a valuable model to study adaptation. In contrast to pure-breed dogs that constitute artificially maintained inbred lines, free-ranging dogs are typically free-breeding, i.e., unrestrained in mate choice. Many traits in free-breeding dogs (FBDs) may be under similar natural and sexual selection conditions to wild canids, while relaxation of sexual selection is expected in pure-breed dogs. We used a Bayesian approach with strict false-positive control criteria to identify FST-outlier SNPs between FBDs and either European or East Asian breeds, based on 167,989 autosomal SNPs. By identifying outlier SNPs located within coding genes, we found four candidate genes under diversifying selection shared by these two comparisons. Three of them are associated with the Hedgehog (HH) signaling pathway regulating vertebrate morphogenesis. A comparison between FBDs and East Asian breeds also revealed diversifying selection on the BBS6 gene, which was earlier shown to cause snout shortening and dental crowding via disrupted HH signaling. Our results suggest that relaxation of natural and sexual selection in pure-breed dogs as opposed to FBDs could have led to mild changes in regulation of the HH signaling pathway. HH inhibits adhesion and the migration of neural crest cells from the neural tube, and minor deficits of these cells during embryonic development have been proposed as the underlying cause of "domestication syndrome." This suggests that the process of breed formation involved the same genetic and developmental pathways as the process of domestication. Copyright © 2016 Pilot et al.

Diversifying Selection Between Pure-Breed and Free-Breeding Dogs Inferred from Genome-Wide SNP Analysis

PubMed Central

Pilot, Małgorzata; Malewski, Tadeusz; Moura, Andre E.; Grzybowski, Tomasz; Oleński, Kamil; Kamiński, Stanisław; Fadel, Fernanda Ruiz; Alagaili, Abdulaziz N.; Mohammed, Osama B.; Bogdanowicz, Wiesław

2016-01-01

Domesticated species are often composed of distinct populations differing in the character and strength of artificial and natural selection pressures, providing a valuable model to study adaptation. In contrast to pure-breed dogs that constitute artificially maintained inbred lines, free-ranging dogs are typically free-breeding, i.e., unrestrained in mate choice. Many traits in free-breeding dogs (FBDs) may be under similar natural and sexual selection conditions to wild canids, while relaxation of sexual selection is expected in pure-breed dogs. We used a Bayesian approach with strict false-positive control criteria to identify FST-outlier SNPs between FBDs and either European or East Asian breeds, based on 167,989 autosomal SNPs. By identifying outlier SNPs located within coding genes, we found four candidate genes under diversifying selection shared by these two comparisons. Three of them are associated with the Hedgehog (HH) signaling pathway regulating vertebrate morphogenesis. A comparison between FBDs and East Asian breeds also revealed diversifying selection on the BBS6 gene, which was earlier shown to cause snout shortening and dental crowding via disrupted HH signaling. Our results suggest that relaxation of natural and sexual selection in pure-breed dogs as opposed to FBDs could have led to mild changes in regulation of the HH signaling pathway. HH inhibits adhesion and the migration of neural crest cells from the neural tube, and minor deficits of these cells during embryonic development have been proposed as the underlying cause of “domestication syndrome.” This suggests that the process of breed formation involved the same genetic and developmental pathways as the process of domestication. PMID:27233669

Post-copulatory sexual selection and female fitness in Scathophaga stercoraria.

PubMed

Martin, Oliver Y; Hosken, David J; Ward, Paul I

2004-02-22

Whether sexual selection increases or decreases female fitness is determined by the occurrence and relative importance of sexual-conflict processes and the ability of females to choose high-quality males. Experimentally enforced polyandry and monogamy have previously been shown to cause rapid evolution in the yellow dung fly Scathophaga stercoraria. Flies from polyandrous lines invested more in reproductive tissue, and this investment influenced paternity in sperm competition, but came at a cost to immune function. While some fitness consequences of enforced polyandry or monogamy have been examined when flies mate multiply, the consequences for female fitness when singly copulated remain unexplored. Under a good-genes scenario females from polyandrous lines should be of higher general quality and should outperform females from monogamous lines even with a single copulation. Under sexual conflict, costly adaptations will afford no advantages when females are allowed to mate only once. We investigate the lifetime reproductive success and longevity of females evolving under enforced monogamy or polyandry when mating once with males from these selection regimes. Females from polyandrous lines were found to have lower fitness than their monogamous counterparts when mating once. They died earlier and produced significantly fewer eggs and offspring. These results suggest that sexual conflict probably drove evolution under enforced polyandry as female fitness did not increase overall as expected with purely good-genes effects.

Quantitative genetic insights into the coevolutionary dynamics of male and female genitalia

PubMed Central

Evans, Jonathan P.; van Lieshout, Emile; Gasparini, Clelia

2013-01-01

The spectacular variability that typically characterizes male genital traits has largely been attributed to the role of sexual selection. Among the evolutionary mechanisms proposed to account for this diversity, two processes in particular have generated considerable interest. On the one hand, females may exploit postcopulatory mechanisms of selection to favour males with preferred genital traits (cryptic female choice; CFC), while on the other hand females may evolve structures or behaviours that mitigate the direct costs imposed by male genitalia (sexual conflict; SC). A critical but rarely explored assumption underlying both processes is that male and female reproductive traits coevolve, either via the classic Fisherian model of preference-trait coevolution (CFC) or through sexually antagonistic selection (SC). Here, we provide evidence for this prediction in the guppy (Poecilia reticulata), a polyandrous livebearing fish in which males transfer sperm internally to females via consensual and forced matings. Our results from a paternal half-sibling breeding design reveal substantial levels of additive genetic variation underlying male genital size and morphology—two traits known to predict mating success during non-consensual matings. Our subsequent finding that physically interacting female genital traits exhibit corresponding levels of genetic (co)variation reveals the potential intersexual coevolutionary dynamics of male and female genitalia, thereby fulfilling a fundamental assumption underlying CFC and SC theory. PMID:23720546

Protozoan Parasite Toxoplasma gondii Manipulates Mate Choice in Rats by Enhancing Attractiveness of Males

PubMed Central

Dutta, Deborah; Soh, Linda Jing Ting; Sapolsky, Robert Morris; Vyas, Ajai

2011-01-01

Females in various species typically avoid males infected with parasites, while parasite-free males advertise their status through conspicuous phenotypic traits. This process selects for heritable resistance and reduces direct exposure of the female to parasites. Coevolving parasites are likely to attempt to circumvent this obstacle. In this paper, we demonstrate a case of parasitic manipulation of host mate choice. We report that Toxoplasma gondii, a sexually transmitted infection of brown rats, enhances sexual attractiveness of infected males. Thus under some evolutionary niches, parasites can indeed manipulate host sexual signaling to their own advantage. PMID:22073295

Sexual safety and sexual security among young Black women who have sex with women and men.

PubMed

Alexander, Kamila Anise; Fannin, Ehriel F

2014-01-01

To examine sexuality narratives of Black women who have sex with women and men and explore factors that influence their sexual safety and sexual security. Secondary qualitative content analysis. We recruited young self-identified Black women from beauty salons and community-based organizations. Our sample included a subset of five sexually active, Black women age 19 to 25 who reported engaging in sexual relationships with women and men. Participants were selected from a larger parent study that included sexuality narratives from 25 women. We analyzed interview transcripts in which participants described sexual relationships. We used constant comparative techniques and conventional content analysis methodology. We uncovered three themes illustrating influences on sexual safety and sexual security: institutional expectations, emotional connectedness, and sexual behaviors. From this analysis, we derive valuable insights into decision-making processes within sexual relationships from the perspectives of young Black women who have sex with women and men. Clinicians and investigators can use these findings to inform programs designed to improve the sexual health of this often invisible group of women. Nurses are uniquely positioned to support young women as they navigate societal institutions and emotional experiences that inform future sexual decisions and behaviors. © 2014 AWHONN, the Association of Women's Health, Obstetric and Neonatal Nurses.

The Earliest Case of Extreme Sexual Display with Exaggerated Male Organs by Two Middle Jurassic Mecopterans

PubMed Central

Wang, Qi; Shih, Chungkun; Ren, Dong

2013-01-01

Background Many extant male animals exhibit exaggerated body parts for display, defense or offence in sexual selection, such as male birds of paradise showing off colorful and elegant feathers and male moose and reindeers bearing large structured antlers. For insects, male rhinoceros and stag beetles have huge horn-like structure for fighting and competition and some male Leptopanorpa scorpionflies have very long abdominal terminal segments for sexual display and competition. Fossil records of insects having exaggerated body parts for sexual display are fairly rare. One example is two male holcorpids with elongate abdominal segments from sixth (A6) to eighth (A8) and enlarged male genitalia from Eocene, suggesting evolution of these characters occurred fairly late. Principal Findings We document two mecopterans with exaggerated male body parts from the late Middle Jurassic Jiulongshan Formation in northeastern China. Both have extremely extended abdominal segments from A6 to A8 and enlarged genitalia, which might have been used for sexual display and, to less extent, for fighting with other males in the competition for mates. Although Fortiholcorpa paradoxa gen. et sp. nov. and Miriholcorpa forcipata gen. et sp. nov. seem to have affinities with Holcorpidae, we deem both as Family Incertae sedis mainly due to significant differences in branching pattern of Media (M) veins and relative length of A8 for F. paradoxa, and indiscernible preservation of 5-branched M veins in hind wing for M. forcipata. Conclusions/Significance These two new taxa have extended the records of exaggerated male body parts of mecopterans for sexual display and/or selection from the Early Eocene to the late Middle Jurassic. The similar character present in some Leptopanorpa of Panorpidae suggests that the sexual display and/or sexual selection due to extremely elongated male abdominal and sexual organs outweigh the negative impact of bulky body and poor mobility in the evolutionary process. PMID:23977031

Do extra-group fertilizations increase the potential for sexual selection in male mammals?

PubMed

Isvaran, Kavita; Sankaran, Sumithra

2017-10-01

Fertilizations by males outside the social breeding group (extra-group paternity, EGP) are widespread in birds and mammals. EGP is generally proposed to increase male reproductive skew and thereby increase the potential for sexual selection, but the generality of this relationship is unclear. We extracted data from 27 mammals in seven orders and used phylogenetic comparative methods to investigate the influence of EGP and social mating system on measures of inequality in male fertilization success, which are indices of the potential for sexual selection. We find that EGP and social mating system can predict the potential for sexual selection in mammalian populations, but only when considered jointly and not individually. EGP appears to increase the potential for sexual selection but only when the degree of social polygyny is relatively low. When social polygyny is high, EGP appears to result in a more uniform distribution of reproduction and a decrease in the potential for sexual selection. A possible explanation to be investigated is that the phenotype of extra-group fathers differs systematically across social mating systems. Our findings have implications for the use of EGP and social mating system as indices of sexual selection in comparative analyses of trait evolution under sexual selection. © 2017 The Author(s).

Genetic versus census estimators of the opportunity for sexual selection in the wild.

PubMed

Dunn, Stacey J; Waits, Lisette P; Byers, John A

2012-04-01

Abstract The existence of a direct link between intensity of sexual selection and mating-system type is widely accepted. However, the quantification of sexual selection has proven problematic. Several measures of sexual selection have been proposed, including the operational sex ratio (OSR), the breeding sex ratio (BSR), and the opportunity for sexual selection (I(mates)). For a wild population of pronghorn (Antilocapra americana), we calculated OSR and BSR. We estimated I(mates) from census data on the spatial and temporal distribution of receptive females in rut and from a multigenerational genetic pedigree. OSR and BSR indicated weak sexual selection on males, but census and pedigree I(mates) suggested stronger sexual selection on males than on females. OSR and BSR correlated with census but not pedigree estimates of I(mates), and census I(mates) did not correlate with pedigree estimates. This suggests that the behavioral mating system, as deduced from the spatial and temporal distribution of females, does not predict the genetic mating system of pronghorn. The differences we observed between estimators were primarily due to female mate sampling and choice and to the sex ratio. For most species, behavioral data are not perfectly accurate and therefore will be an insufficient alternative to using multigenerational pedigrees to quantify sexual selection.

The Roles of Sexual and Viability Selection in the Evolution of Incomplete Reproductive Isolation: From Allopatry to Sympatry.

PubMed

Cotto, Olivier; Servedio, Maria R

2017-11-01

In recent years, theoretical models have introduced the concept that ongoing hybridization between "good" species can occur because incomplete reproductive isolation can be a selected optimum. They furthermore show that positive frequency-dependent sexual selection, which is naturally generated by some of the underlying processes that lead to assortative mating, plays a key role in the evolution of incomplete reproductive isolation. This occurs, however, through different mechanisms in sympatric versus allopatric scenarios. We investigate the evolution of incomplete reproductive isolation by sexual selection in scenarios ranging from sympatry to allopatry, to examine how these mechanisms interact. We consider an ecological scenario in which there are two habitats used during foraging and individuals can breed either within a habitat or in a common mating pool. We find that when trait divergence is maintained, sexual selection drives the evolution of choosiness in opposite ways in the common mating pool versus within each habitat. Specifically, strong choosiness is favored in the common mating pool, whereas intermediate choosiness is favored within habitat; the interaction of these forces determines whether intermediate reproductive isolation ultimately evolves in the system. We further find cases where the evolution of stronger choosiness occurs but leads to the loss of divergence. Overall, our study shows that contrasting forces on the evolution of reproductive isolation can occur in different mating areas, and we propose a new avenue for understanding the diversity in levels of reproductive isolation within and across species.

Sexual selection and mate choice.

PubMed

Andersson, Malte; Simmons, Leigh W

2006-06-01

The past two decades have seen extensive growth of sexual selection research. Theoretical and empirical work has clarified many components of pre- and postcopulatory sexual selection, such as aggressive competition, mate choice, sperm utilization and sexual conflict. Genetic mechanisms of mate choice evolution have been less amenable to empirical testing, but molecular genetic analyses can now be used for incisive experimentation. Here, we highlight some of the currently debated areas in pre- and postcopulatory sexual selection. We identify where new techniques can help estimate the relative roles of the various selection mechanisms that might work together in the evolution of mating preferences and attractive traits, and in sperm-egg interactions.

Sexual and natural selection in the evolution of extended phenotypes: the use of green nesting material in starlings.

PubMed

Rubalcaba, J G; Polo, V; Maia, R; Rubenstein, D R; Veiga, J P

2016-08-01

Although sexual selection is typically considered the predominant force driving the evolution of ritualized sexual behaviours, natural selection may also play an important and often underappreciated role. The use of green aromatic plants among nesting birds has been interpreted as a component of extended phenotype that evolved either via natural selection due to potential sanitary functions or via sexual selection as a signal of male attractiveness. Here, we compared both hypotheses using comparative methods in starlings, a group where this behaviour is widespread. We found that the use of green plants was positively related to male-biased size dimorphism and that it was most likely to occur among cavity-nesting species. These results suggest that this behaviour is likely favoured by sexual selection, but also related to its sanitary use in response to higher parasite loads in cavities. We speculate that the use of green plants in starlings may be facilitated by cavity nesting and was subsequently co-opted as a sexual signal by males. Our results represent an example of how an extended phenotypic component of males becomes sexually selected by females. Thus, both natural selection and sexual selection are necessary to fully understand the evolution of ritualized behaviours involved in courtship. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

Lack of phonotactic preferences of female frogs and its consequences for signal evolution.

PubMed

Velásquez, Nelson A; Valdés, Jose Luis; Vásquez, Rodrigo A; Penna, Mario

2015-09-01

Sexual selection is one of the main evolutionary forces that drive signal evolution. In previous studies, we have found out that males of Pleurodema thaul, a frog with an extensive latitudinal distribution in Chile, emits advertisement calls that show remarkable variation among populations. In addition, this variation is related to intense inter-male acoustic competition (intra-sexual selection) occurring within each population. However, the extent to which female preferences contribute to the signal divergence observed is unclear. To study the responsiveness of females in each population, we stimulated females with synthetic calls designed with the acoustic structure of their own population and subsequently responsive females were subjected to a two-choice experiment, where they were stimulated with synthetic calls of their own population versus a call of a foreign population. Females do not show phonotactic preferences for calls of their own or foreign populations as measured with both linear and circular variables. The lack of phonotactic preferences suggests an absence of participation of inter-sexual selection processes in the divergence of the acoustic signals of P. thaul, highlighting the importance of intra-sexual selection for the evolution of these signals. These results concur with studies in other vertebrates emphasizing the relevance of interactions among males for the evolution of acoustic communication systems. Copyright © 2015. Published by Elsevier B.V.

Predator experience overrides learned aversion to heterospecifics in stickleback species pairs

PubMed Central

Kozak, Genevieve M.; Boughman, Janette W.

2015-01-01

Predation risk can alter female mating decisions because the costs of mate searching and selecting attractive mates increase when predators are present. In response to predators, females have been found to plastically adjust mate preference within species, but little is known about how predators alter sexual isolation and hybridization among species. We tested the effects of predator exposure on sexual isolation between benthic and limnetic threespine sticklebacks (Gasterosteus spp.). Female discrimination against heterospecific mates was measured before and after females experienced a simulated attack by a trout predator or a control exposure to a harmless object. In the absence of predators, females showed increased aversion to heterospecifics over time. We found that predator exposure made females less discriminating and precluded this learned aversion to heterospecifics. Benthic and limnetic males differ in coloration, and predator exposure also affected sexual isolation by weakening female preferences for colourful males. Predator effects on sexual selection were also tested but predators had few effects on female choosiness among conspecific mates. Our results suggest that predation risk may disrupt the cognitive processes associated with mate choice and lead to fluctuations in the strength of sexual isolation between species. PMID:25808887

Endocrine regulation and sexual differentiation of avian copulatory sexually selected characters.

PubMed

Brennan, Patricia L R; Adkins-Regan, Elizabeth

2014-10-01

Reproductive specializations in birds have provided intriguing model systems to better understand the role of endocrine mechanisms that regulate phenotype expression and the action of sexual selection. A comparative approach can elucidate how endocrine systems associated with control of sexual differentiation, sexual maturation, and reproductive physiology and behavior have diversified. Here we compare the copulatory sexually selected traits of two members of the galloanseriform superfamily: quail and ducks. Japanese quail have a non-intromittent penis, and they have evolved a unique foam gland that is known to be involved in post-copulatory sexual selection. In contrast, ducks have maintained a large intromittent penis that has evolved via copulatory male-male competition and has been elaborated in a sexually antagonistic race due to sexual conflict with females over mating. These adaptations function in concert with sex-specific and, in part, species-specific behaviors. Although the approaches to study these traits have been different, exploring the differences in neuroendocrine regulation of sexual behavior, development and seasonality of the foam gland and the penis side by side, allow us to suggest some areas where future research would be productive to better understand the evolution of novelty in sexually selected traits. Copyright © 2014 Elsevier Ltd. All rights reserved.

Gender and sexual vulnerability of young women in Africa: experiences of young girls in secondary schools in Uganda.

PubMed

Muhanguzi, Florence Kyoheirwe

2011-06-01

Sexuality is part and parcel of students' experiences of schooling manifested in personal friendships, relations and social interaction. These encounters constitute sites within which sexual identities are developed, practiced and actively produced through processes of negotiation. Drawing on qualitative research conducted in 14 selected secondary schools in Central and Western Uganda, the study illuminates gendered sexual vulnerability within patterns of social interaction and young girls gendered experiences and negotiation of their sexuality. The study reveals that through social and discursive practices, students construct complex gendered relations of domination and subordination that position boys and girls differently, often creating gender inequalities and sexual vulnerability for those gendered as girls. Girls' vulnerability is characterised by confusing and traumatic experiences fraught with double standards and silences. Typical of these experiences are complex tensions and contradictions surrounding constructions of sexuality that are predicated upon unequal power and gender relations characterised by homophobia, misogyny, control of female sexuality and sexual abuse and exploitation, all which work against girls' expression of sexuality. Gender sensitive sexuality education is identified as a valuable site of intervention to address such vulnerabilities and promote gender equality and equity in society.

Validation of Bateman's principles: a genetic study of sexual selection and mating patterns in the rough-skinned newt.

PubMed Central

Jones, Adam G; Arguello, J Roman; Arnold, Stevan J

2002-01-01

Few studies have influenced thought on the nature of sexual selection to the extent of the classic paper of A. J. Bateman on mating patterns in Drosophila. However, interpretation of his study remains controversial, and a lack of modern empirical evidence prevents a consensus with respect to the perceived utility of Bateman's principles in the study of sexual selection. Here, we use a genetic study of natural mating patterns in the rough-skinned newt, Taricha granulosa, to investigate the concordance between Bateman's principles and the intensity of sexual selection. We found that males experienced strong sexual selection on tail height and body size, while sexual selection was undetectable in females. This direct quantification of sexual selection agreed perfectly with inferences that are based on Bateman's principles. Specifically, males (in comparison with females) exhibited greater standardized variances in reproductive and mating success, as well as a stronger relationship between mating success and reproductive success. Overall, our results illustrate that Bateman's principles provide the only quantitative measures of the mating system with explicit connections to formal selection theory and should be the central focus of studies of mating patterns in natural populations. PMID:12573067

Sexual selection accelerates signal evolution during speciation in birds.

PubMed

Seddon, Nathalie; Botero, Carlos A; Tobias, Joseph A; Dunn, Peter O; Macgregor, Hannah E A; Rubenstein, Dustin R; Uy, J Albert C; Weir, Jason T; Whittingham, Linda A; Safran, Rebecca J

2013-09-07

Sexual selection is proposed to be an important driver of diversification in animal systems, yet previous tests of this hypothesis have produced mixed results and the mechanisms involved remain unclear. Here, we use a novel phylogenetic approach to assess the influence of sexual selection on patterns of evolutionary change during 84 recent speciation events across 23 passerine bird families. We show that elevated levels of sexual selection are associated with more rapid phenotypic divergence between related lineages, and that this effect is restricted to male plumage traits proposed to function in mate choice and species recognition. Conversely, we found no evidence that sexual selection promoted divergence in female plumage traits, or in male traits related to foraging and locomotion. These results provide strong evidence that female choice and male-male competition are dominant mechanisms driving divergence during speciation in birds, potentially linking sexual selection to the accelerated evolution of pre-mating reproductive isolation.

Timing as a sexually selected trait: the right mate at the right moment.

PubMed

Hau, Michaela; Dominoni, Davide; Casagrande, Stefania; Buck, C Loren; Wagner, Gabriela; Hazlerigg, David; Greives, Timothy; Hut, Roelof A

2017-11-19

Sexual selection favours the expression of traits in one sex that attract members of the opposite sex for mating. The nature of sexually selected traits such as vocalization, colour and ornamentation, their fitness benefits as well as their costs have received ample attention in field and laboratory studies. However, sexually selected traits may not always be expressed: coloration and ornaments often follow a seasonal pattern and behaviours may be displayed only at specific times of the day. Despite the widely recognized differences in the daily and seasonal timing of traits and their consequences for reproductive success, the actions of sexual selection on the temporal organization of traits has received only scant attention. Drawing on selected examples from bird and mammal studies, here we summarize the current evidence for the daily and seasonal timing of traits. We highlight that molecular advances in chronobiology have opened exciting new opportunities for identifying the genetic targets that sexual selection may act on to shape the timing of trait expression. Furthermore, known genetic links between daily and seasonal timing mechanisms lead to the hypothesis that selection on one timescale may simultaneously also affect the other. We emphasize that studies on the timing of sexual displays of both males and females from wild populations will be invaluable for understanding the nature of sexual selection and its potential to act on differences within and between the sexes in timing. Molecular approaches will be important for pinpointing genetic components of biological rhythms that are targeted by sexual selection, and to clarify whether these represent core or peripheral components of endogenous clocks. Finally, we call for a renewed integration of the fields of evolution, behavioural ecology and chronobiology to tackle the exciting question of how sexual selection contributes to the evolution of biological clocks.This article is part of the themed issue 'Wild clocks: integrating chronobiology and ecology to understand timekeeping in free-living animals'. © 2017 The Author(s).

Sexual selection and the adaptive evolution of PKDREJ protein in primates and rodents.

PubMed

Vicens, Alberto; Gómez Montoto, Laura; Couso-Ferrer, Francisco; Sutton, Keith A; Roldan, Eduardo R S

2015-02-01

PKDREJ is a testis-specific protein thought to be located on the sperm surface. Functional studies in the mouse revealed that loss of PKDREJ has effects on sperm transport and the ability to undergo an induced acrosome reaction. Thus, PKDREJ has been considered a potential target of post-copulatory sexual selection in the form of sperm competition. Proteins involved in reproductive processes often show accelerated evolution. In many cases, this rapid divergence is promoted by positive selection which may be driven, at least in part, by post-copulatory sexual selection. We analysed the evolution of the PKDREJ protein in primates and rodents and assessed whether PKDREJ divergence is associated with testes mass relative to body mass, which is a reliable proxy of sperm competition levels. Evidence of an association between the evolutionary rate of the PKDREJ gene and testes mass relative to body mass was not found in primates. Among rodents, evidence of positive selection was detected in the Pkdrej gene in the family Cricetidae but not in Muridae. We then assessed whether Pkdrej divergence is associated with episodes of sperm competition in these families. We detected a positive significant correlation between the evolutionary rates of Pkdrej and testes mass relative to body mass in cricetids. These findings constitute the first evidence of post-copulatory sexual selection influencing the evolution of a protein that participates in the mechanisms regulating sperm transport and the acrosome reaction, strongly suggesting that positive selection may act on these fertilization steps, leading to advantages in situations of sperm competition. © The Author 2014. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Sexual selection and the opportunity cost of free mate choice.

PubMed

Apostolou, Menelaos

2016-06-01

The model of sexual selection under parental choice has been proposed to account for the control that parents exercise over their children's mating decisions. The present paper attempts to formalize and advance this model with the purpose of providing a better understanding of how parental choice mandates the course of sexual selection. In particular, in the proposed formulation, free mate choice involves an opportunity cost which motivates parents to place their children's mate choices under their control. When they succeed in doing so, they become a significant sexual selection force, as traits that appeal to parents in an in-law are selected and increase in frequency in the population. The degree of parental control over mating, and thus the strength of sexual selection under parental choice, is positively predicted by the size of the opportunity cost of free mate choice. The primary factors that affect the level of opportunity cost vary between society types, affecting the strength of parental choice as a sexual selection force.

Rapid adaptation to mammalian sociality via sexually selected traits

PubMed Central

2013-01-01

Background Laboratory studies show that the components of sexual selection (e.g., mate choice and intrasexual competition) can profoundly affect the development and fitness of offspring. Less is known, however, about the total effects of sexual selection on offspring in normal social conditions. Complex social networks, such as dominance hierarchies, regulate the opportunity for mating success, and are often missing from laboratory studies. Social selection is an extended view of sexual selection that incorporates competition during sexual and nonsexual interactions, and predicts complex evolutionary dynamics. Whether social selection improves or constrains offspring fitness is controversial. Results To identify fitness consequences of social selection, wild-derived mice that had bred under laboratory conditions for eight generations were re-introduced to naturalistic competition in enclosures for three consecutive generations (promiscuous line). In parallel, a control lineage bred in cages under random mate assignment (monogamous line). A direct competition experiment using second-generation animals revealed that promiscuous line males had greater reproductive success than monogamous line males (particularly during extra-territorial matings), in spite of higher mortality and equivalent success in social dominance and sperm competition. There were no major female fitness effects (though promiscuous line females had fewer litters than monogamous line females). This result suggested that selection primarily acted upon a sexually attractive male phenotype in the promiscuous line, a hypothesis we confirmed in female odor and mating preference trials. Conclusions We present novel evidence for the strength of sexual selection under normal social conditions, and show rapid male adaptation driven largely by sexual trait expression, with tradeoffs in survivorship and female fecundity. Re-introducing wild-derived mice to competition quickly uncovers sexually selected phenotypes otherwise lost in normal colony breeding. PMID:23577674

Sexual selection expedites the evolution of pesticide resistance.

PubMed

Jacomb, Frances; Marsh, Jason; Holman, Luke

2016-12-01

The evolution of insecticide resistance by crop pests and disease vectors causes serious problems for agriculture and health. Sexual selection can accelerate or hinder adaptation to abiotic challenges in a variety of ways, but the effect of sexual selection on resistance evolution is little studied. Here, we examine this question using experimental evolution in the pest insect Tribolium castaneum. The experimental removal of sexual selection slowed the evolution of resistance in populations treated with pyrethroid pesticide, and also reduced the rate at which resistance was lost from pesticide-free populations. These results suggest that selection arising from variance in mating and fertilization success can augment natural selection on pesticide resistance, meaning that sexual selection should be considered when designing strategies to limit the evolution of pesticide resistance. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

Adaptations to sexual selection and sexual conflict: insights from experimental evolution and artificial selection.

PubMed

Edward, Dominic A; Fricke, Claudia; Chapman, Tracey

2010-08-27

Artificial selection and experimental evolution document natural selection under controlled conditions. Collectively, these techniques are continuing to provide fresh and important insights into the genetic basis of evolutionary change, and are now being employed to investigate mating behaviour. Here, we focus on how selection techniques can reveal the genetic basis of post-mating adaptations to sexual selection and sexual conflict. Alteration of the operational sex ratio of adult Drosophila over just a few tens of generations can lead to altered ejaculate allocation patterns and the evolution of resistance in females to the costly effects of elevated mating rates. We provide new data to show how male responses to the presence of rivals can evolve. For several traits, the way in which males responded to rivals was opposite in lines selected for male-biased, as opposed to female-biased, adult sex ratio. This shows that the manipulation of the relative intensity of intra- and inter-sexual selection can lead to replicable and repeatable effects on mating systems, and reveals the potential for significant contemporary evolutionary change. Such studies, with important safeguards, have potential utility for understanding sexual selection and sexual conflict across many taxa. We discuss how artificial selection studies combined with genomics will continue to deepen our knowledge of the evolutionary principles first laid down by Darwin 150 years ago.

Sexual selection predicts species richness across the animal kingdom.

PubMed

Janicke, Tim; Ritchie, Michael G; Morrow, Edward H; Marie-Orleach, Lucas

2018-05-16

Our improving knowledge of the animal tree of life consistently demonstrates that some taxa diversify more rapidly than others, but what contributes to this variation remains poorly understood. An influential hypothesis proposes that selection arising from competition for mating partners plays a key role in promoting speciation. However, empirical evidence showing a link between proxies of this sexual selection and species richness is equivocal. Here, we collected standardized metrics of sexual selection for a broad range of animal taxa, and found that taxonomic families characterized by stronger sexual selection on males show relatively higher species richness. Thus, our data support the hypothesis that sexual selection elevates species richness. This could occur either by promoting speciation and/or by protecting species against extinction. © 2018 The Author(s).

Sexual selection on spontaneous mutations strengthens the between-sex genetic correlation for fitness.

PubMed

Allen, Scott L; McGuigan, Katrina; Connallon, Tim; Blows, Mark W; Chenoweth, Stephen F

2017-10-01

A proposed benefit to sexual selection is that it promotes purging of deleterious mutations from populations. For this benefit to be realized, sexual selection, which is usually stronger on males, must purge mutations deleterious to both sexes. Here, we experimentally test the hypothesis that sexual selection on males purges deleterious mutations that affect both male and female fitness. We measured male and female fitness in two panels of spontaneous mutation-accumulation lines of the fly, Drosophila serrata, each established from a common ancestor. One panel of mutation accumulation lines limited both natural and sexual selection (LS lines), whereas the other panel limited natural selection, but allowed sexual selection to operate (SS lines). Although mutation accumulation caused a significant reduction in male and female fitness in both the LS and SS lines, sexual selection had no detectable effect on the extent of the fitness reduction. Similarly, despite evidence of mutational variance for fitness in males and females of both treatments, sexual selection had no significant impact on the amount of mutational genetic variance for fitness. However, sexual selection did reshape the between-sex correlation for fitness: significantly strengthening it in the SS lines. After 25 generations, the between-sex correlation for fitness was positive but considerably less than one in the LS lines, suggesting that, although most mutations had sexually concordant fitness effects, sex-limited, and/or sex-biased mutations contributed substantially to the mutational variance. In the SS lines this correlation was strong and could not be distinguished from unity. Individual-based simulations that mimick the experimental setup reveal two conditions that may drive our results: (1) a modest-to-large fraction of mutations have sex-limited (or highly sex-biased) fitness effects, and (2) the average fitness effect of sex-limited mutations is larger than the average fitness effect of mutations that affect both sexes similarly. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

Darwinian sex roles confirmed across the animal kingdom

PubMed Central

Janicke, Tim; Häderer, Ines K.; Lajeunesse, Marc J.; Anthes, Nils

2016-01-01

Since Darwin’s conception of sexual selection theory, scientists have struggled to identify the evolutionary forces underlying the pervasive differences between male and female behavior, morphology, and physiology. The Darwin-Bateman paradigm predicts that anisogamy imposes stronger sexual selection on males, which, in turn, drives the evolution of conventional sex roles in terms of female-biased parental care and male-biased sexual dimorphism. Although this paradigm forms the cornerstone of modern sexual selection theory, it still remains untested across the animal tree of life. This lack of evidence has promoted the rise of alternative hypotheses arguing that sex differences are entirely driven by environmental factors or chance. We demonstrate that, across the animal kingdom, sexual selection, as captured by standard Bateman metrics, is indeed stronger in males than in females and that it is evolutionarily tied to sex biases in parental care and sexual dimorphism. Our findings provide the first comprehensive evidence that Darwin’s concept of conventional sex roles is accurate and refute recent criticism of sexual selection theory. PMID:26933680

Darwinian sex roles confirmed across the animal kingdom.

PubMed

Janicke, Tim; Häderer, Ines K; Lajeunesse, Marc J; Anthes, Nils

2016-02-01

Since Darwin's conception of sexual selection theory, scientists have struggled to identify the evolutionary forces underlying the pervasive differences between male and female behavior, morphology, and physiology. The Darwin-Bateman paradigm predicts that anisogamy imposes stronger sexual selection on males, which, in turn, drives the evolution of conventional sex roles in terms of female-biased parental care and male-biased sexual dimorphism. Although this paradigm forms the cornerstone of modern sexual selection theory, it still remains untested across the animal tree of life. This lack of evidence has promoted the rise of alternative hypotheses arguing that sex differences are entirely driven by environmental factors or chance. We demonstrate that, across the animal kingdom, sexual selection, as captured by standard Bateman metrics, is indeed stronger in males than in females and that it is evolutionarily tied to sex biases in parental care and sexual dimorphism. Our findings provide the first comprehensive evidence that Darwin's concept of conventional sex roles is accurate and refute recent criticism of sexual selection theory.

Legal Consciousness and Responses to Sexual Harassment*

PubMed Central

Blackstone, Amy; Uggen, Christopher; McLaughlin, Heather

2009-01-01

Studies of legal mobilization often focus on people who have perceived some wrong, but rarely consider the process that selects them into the pool of potential “mobilizers.” Similarly, studies of victimization or targeting rarely go on to consider what people do about the wrong, or why some targets come forward and others remain silent. We here integrate sociolegal, feminist, and criminological theories in a conceptual model that treats experiencing sexual harassment and mobilizing in response to it as interrelated processes. We then link these two processes by modeling them as jointly determined outcomes and examine their connections using interviews with a subset of our survey respondents. Our results suggest that targets of harassment are selected, in part, because they are least likely to tell others about the experience. Strategies that workers employ to cope with and confront harassment are also discussed. We find that traditional formal/informal dichotomies of mobilization responses may not fully account for the range of ways individuals respond to harassment, and we propose a preliminary typology of responses. PMID:20300446

Testing for a genetic response to sexual selection in a wild Drosophila population.

PubMed

Gosden, T P; Thomson, J R; Blows, M W; Schaul, A; Chenoweth, S F

2016-06-01

In accordance with the consensus that sexual selection is responsible for the rapid evolution of display traits on macroevolutionary scales, microevolutionary studies suggest sexual selection is a widespread and often strong form of directional selection in nature. However, empirical evidence for the contemporary evolution of sexually selected traits via sexual rather than natural selection remains weak. In this study, we used a novel application of quantitative genetic breeding designs to test for a genetic response to sexual selection on eight chemical display traits from a field population of the fly, Drosophila serrata. Using our quantitative genetic approach, we were able to detect a genetically based difference in means between groups of males descended from fathers who had either successfully sired offspring or were randomly collected from the same wild population for one of these display traits, the diene (Z,Z)-5,9-C27 : 2 . Our experimental results, in combination with previous laboratory studies on this system, suggest that both natural and sexual selection may be influencing the evolutionary trajectories of these traits in nature, limiting the capacity for a contemporary evolutionary response. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

Sexual selection on female ornaments in the sex-role-reversed Gulf pipefish (Syngnathus scovelli).

PubMed

Flanagan, S P; Johnson, J B; Rose, E; Jones, A G

2014-11-01

Understanding how selection acts on traits individually and in combination is an important step in deciphering the mechanisms driving evolutionary change, but for most species, and especially those in which sexual selection acts more strongly on females than on males, we have no estimates of selection coefficients pertaining to the multivariate sexually selected phenotype. Here, we use a laboratory-based mesocosm experiment to quantify pre- and post-mating selection on female secondary sexual traits in the Gulf pipefish (Syngnathus scovelli), a sexually dimorphic, sex-role-reversed species in which ornamented females compete for access to choosy males. We calculate selection differentials and gradients on female traits, including ornament area, ornament number and body size for three episodes of selection related to female reproductive success (number of mates, number of eggs transferred and number of surviving embryos). Selection is strong on both ornament area and ornament size, and the majority of selection occurs during the premating episode of selection. Interestingly, selection on female body size, which has been detected in previous studies of Gulf pipefish, appears to be indirect, as evidenced by a multivariate analysis of selection gradients. Our results show that sexual selection favours either many bands or larger bands in female Gulf pipefish. © 2014 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

An Exploratory Study of Selected Sexual Knowledge and Attitudes of Indiana Adults

ERIC Educational Resources Information Center

Clark, Christina A.; Baldwin, Kathleen L.; Tanner, Amanda E.

2007-01-01

Although there are numerous ways to obtain accurate information about sexuality, research suggests that many American adults do not have accurate sexuality and sexual health knowledge. This research investigated selected sexual knowledge and attitudes of adults in Indiana. A representative sample of men (n = 158) and women (n = 340) aged 18 to 89…

Demographic drivers of age-dependent sexual selection.

PubMed

Martin, A M; Festa-Bianchet, M; Coltman, D W; Pelletier, F

2016-07-01

Sexual selection has a critical role in evolution, and it is fundamental to identify what ecological factors drive its variation. Disentangling the ecological correlates of sexual selection over the long term, however, is challenging and has rarely been done in nature. We sought to assess how demographic changes influenced the intensity, direction and form of sexual selection and whether selective pressures varied with age. We tested whether breeder sex ratio, number of competitors and age structure influenced selection differentials on horn length of wild bighorn rams (Ovis canadensis) of different age classes on Ram Mountain, Alberta. We used 21 years of data including a detailed pedigree, demographic parameters and repeated morphological measurements. Sexual selection on horn length of males of all ages was directional and positive. Selection intensity increased with the number of competitors, reflecting male-male encounter rate during the rut, but was independent of breeder sex ratio or age structure. This result can also be linked to changes in population size because the number of competitors was highly correlated to total number of sheep. This demographic effect likely arises from age-dependent mating tactics. Males aged 2-4 years are weakly competitive and experienced stronger sexual selection as they accounted for a greater proportion of all males. Selection experienced by mature males appeared independent of demography. Our study provides a rare description of the demographic determinants of sexual selection in nature. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

Sexual selection and the rodent baculum: an intraspecific study in the house mouse (Mus musculus domesticus).

PubMed

Ramm, Steven A; Khoo, Lin; Stockley, Paula

2010-01-01

The rapid divergence of genitalia is a pervasive trend in animal evolution, thought to be due to the action of sexual selection. To test predictions from the sexual selection hypothesis, we here report data on the allometry, variation, plasticity and condition dependence of baculum morphology in the house mouse (Mus musculus domesticus). We find that that baculum size: (a) exhibits no consistent pattern of allometric scaling (baculum size being in most cases unrelated to body size), (b) exhibits low to moderate levels of phenotypic variation, (c) does not exhibit phenotypic plasticity in response to differences in perceived levels of sexual competition and (d) exhibits limited evidence of condition dependence. These patterns provide only limited evidence in support of the sexual selection hypothesis, and no consistent support for any particular sexual selection mechanism; however, more direct measures of how genital morphology influences male fertilization success are required.

Ornament Complexity Is Correlated with Sexual Selection: (A Comment on Raia et al., "Cope's Rule and the Universal Scaling Law of Ornament Complexity").

PubMed

Holman, Luke; Bro-Jørgensen, Jakob

2016-08-01

Raia et al. propose that the evolution of the shape and complexity of animal ornaments (e.g., deer antlers) can be explained by interspecific variation in body size and is not influenced by sexual selection. They claim to show that ornament complexity is related to body size by an 0.25-power law and argue that this finding precludes a role for sexual selection in the evolution of ornament complexity. However, their study does not test alternative hypotheses and mismeasures antler shape allometry by omitting much of the published data. We show that an index of sexual selection (sexual size dimorphism) is positively correlated with size-corrected antler complexity and that the allometric slope of complexity is substantially greater than 0.25, contra Raia et al. We conclude that sexual selection and physical constraints both affect the evolution of antler shape.

Quantitative genetics and sex-specific selection on sexually dimorphic traits in bighorn sheep

PubMed Central

Poissant, Jocelyn; Wilson, Alastair J; Festa-Bianchet, Marco; Hogg, John T; Coltman, David W

2008-01-01

Sexual conflict at loci influencing traits shared between the sexes occurs when sex-specific selection pressures are antagonistic relative to the genetic correlation between the sexes. To assess whether there is sexual conflict over shared traits, we estimated heritability and intersexual genetic correlations for highly sexually dimorphic traits (horn volume and body mass) in a wild population of bighorn sheep (Ovis canadensis) and quantified sex-specific selection using estimates of longevity and lifetime reproductive success. Body mass and horn volume showed significant additive genetic variance in both sexes, and intersexual genetic correlations were 0.24±0.28 for horn volume and 0.63±0.30 for body mass. For horn volume, selection coefficients did not significantly differ from zero in either sex. For body weight, selection coefficients were positive in females but did not differ from zero in males. The absence of detectable sexually antagonistic selection suggests that currently there are no sexual conflicts at loci influencing horn volume and body mass. PMID:18211870

Sexual selection modulates genetic conflicts and patterns of genomic imprinting

PubMed Central

Faria, Gonçalo S.; Varela, Susana A. M.; Gardner, Andy

2017-01-01

Recent years have seen a surge of interest in linking the theories of kin selection and sexual selection. In particular, there is a growing appreciation that kin selection, arising through demographic factors such as sex‐biased dispersal, may modulate sexual conflicts, including in the context of male–female arms races characterized by coevolutionary cycles. However, evolutionary conflicts of interest need not only occur between individuals, but may also occur within individuals, and sex‐specific demography is known to foment such intragenomic conflict in relation to social behavior. Whether and how this logic holds in the context of sexual conflict—and, in particular, in relation to coevolutionary cycles—remains obscure. We develop a kin‐selection model to investigate the interests of different genes involved in sexual and intragenomic conflict, and we show that consideration of these conflicting interests yields novel predictions concerning parent‐of‐origin specific patterns of gene expression and the detrimental effects of different classes of mutation and epimutation at loci underpinning sexually selected phenotypes. PMID:27991659

Sexual minorities and selection of a primary care physician in a midwestern U.S. city.

PubMed

Labig, Chalmer E; Peterson, Tim O

2006-01-01

How and why sexual minorities select a primary care physician is critical to the development of methods for attracting these clients to a physician's practice. Data obtained from a sample of sexual minorities in a mid-size city in our nation's heartland would indicate that these patients are loyal when the primary care physician has a positive attitude toward their sexual orientation. The data also confirms that most sexual minorities select same sex physicians but not necessarily same sexual orientation physicians because of lack of knowledge of physicians' sexual orientation. Family practice physicians and other primary care physicians can reach out to this population by encouraging word of mouth advertising and by displaying literature on health issues for all sexual orientations in their offices.

Aesthetic and Functional Male to Female Genital and Perineal Surgery: Feminizing Vaginoplasty

PubMed Central

Reed, Harold Morgan

2011-01-01

Male to female transsexuals frequently seek feminizing vaginoplasty for “below the waist” conformation, enhancement of sexual identity, and interactive sexual function. The author shares his experience with his first 250 primary surgical procedures. Included is a brief historical background, the patient selection process, some guidelines from the World Professional Association for Transgender Health (standards of care), preoperative evaluation and instructions, surgical technique, postoperative regimen, risk factors, results, complications and management. The patients all underwent feminizing vaginoplasty at the author's ambulatory surgical facility, which includes an overnight stay. The author's results suggest that feminizing vaginoplasty when performed vigilantly on a select group of patients is feasible. PMID:22547974

Evolution of sexual dichromatism in relation to nesting habits in European passerines: a test of Wallace's hypothesis.

PubMed

Soler, J J; Moreno, J

2012-08-01

Wallace proposed in 1868 that natural rather than sexual selection could explain the striking differences in avian plumage dichromatism. Thus, he predicted that nesting habits, through their association with nest predation, could drive changes in sexual dichromatism by enabling females in cavity nesters to become as conspicuous as males, whereas Darwin (1871, The Descent of Man and Selection in Relation to Sex, John Murray, London) argued that sexual selection was the sole explanation for dichromatism. Sexual dichromatism is currently used as indicating the strength of sexual selection, and therefore testing Wallace's claim with modern phylogentically controlled methodologies is of prime interest for comparing the roles of natural and sexual selection in affecting the evolution of avian coloration. Here, we have related information on nest attendance, sexual dichromatism and nesting habits (open and cavity nesting) to male and female plumage conspicuousness in European passerines. Nest incubation attendance does not explain male or female plumage conspicuousness but nest type does. Moreover, although females of monochromatic and cavity nesting species are more conspicuous than females of other species, males of monochromatic and open nesting species are those with more cryptic plumage. Finally, analyses of character evolution suggest that changes in nesting habits influence the probability of changes in both dichromatism and plumage conspicuousness of males but do not significantly affect those in females. These results strongly suggest a role of nesting habits in the evolution of plumage conspicuousness of males, and a role for sexual selection also in females, both factors affecting the evolution of sexual dichromatism. We discuss our findings in relation to the debate that Darwin and Wallace maintained more than one century ago on the importance of natural and sexual selection in driving the evolution of plumage conspicuousness and sexual dichromatism in birds, and conclude that our results partly support the evolutionary scenarios envisaged by both extraordinary scientists. © 2012 The Authors. Journal of Evolutionary Biology © 2012 European Society For Evolutionary Biology.

Sexual selection drives speciation in an Amazonian frog

USGS Publications Warehouse

Boul, K.E.; Funk, W.C.; Darst, C.R.; Cannatella, D.C.; Ryan, M.J.

2007-01-01

One proposed mechanism of speciation is divergent sexual selection, whereby divergence in female preferences and male signals results in behavioural isolation. Despite the appeal of this hypothesis, evidence for it remains inconclusive. Here, we present several lines of evidence that sexual selection is driving behavioural isolation and speciation among populations of an Amazonian frog (Physalaemus petersi). First, sexual selection has promoted divergence in male mating calls and female preferences for calls between neighbouring populations, resulting in strong behavioural isolation. Second, phylogenetic analysis indicates that populations have become fixed for alternative call types several times throughout the species' range, and coalescent analysis rejects genetic drift as a cause for this pattern, suggesting that this divergence is due to selection. Finally, gene flow estimated with microsatellite loci is an average of 30 times lower between populations with different call types than between populations separated by a similar geographical distance with the same call type, demonstrating genetic divergence and incipient speciation. Taken together, these data provide strong evidence that sexual selection is driving behavioural isolation and speciation, supporting sexual selection as a cause for speciation in the wild. ?? 2006 The Royal Society.

Sexual selection and conflict as engines of ecological diversification.

PubMed

Bonduriansky, Russell

2011-12-01

Ecological diversification presents an enduring puzzle: how do novel ecological strategies evolve in organisms that are already adapted to their ecological niche? Most attempts to answer this question posit a primary role for genetic drift, which could carry populations through or around fitness "valleys" representing maladaptive intermediate phenotypes between alternative niches. Sexual selection and conflict are thought to play an ancillary role by initiating reproductive isolation and thereby facilitating divergence in ecological traits through genetic drift or local adaptation. Here, I synthesize theory and evidence suggesting that sexual selection and conflict could play a more central role in the evolution and diversification of ecological strategies through the co-optation of sexual traits for viability-related functions. This hypothesis rests on three main premises, all of which are supported by theory and consistent with the available evidence. First, sexual selection and conflict often act at cross-purposes to viability selection, thereby displacing populations from the local viability optimum. Second, sexual traits can serve as preadaptations for novel viability-related functions. Third, ancestrally sex-limited sexual traits can be transferred between sexes. Consequently, by allowing populations to explore a broad phenotypic space around the current viability optimum, sexual selection and conflict could act as powerful drivers of ecological adaptation and diversification.

The role of sexual and natural selection in shaping patterns of sexual dichromatism in the largest family of songbirds (Aves: Thraupidae).

PubMed

Shultz, Allison J; Burns, Kevin J

2017-04-01

Males and females can be under different evolutionary pressures if sexual and natural selection is differentially operating in each sex. As a result, many species have evolved sexual dichromatism, or differences in coloration between sexes. Although sexual dichromatism is often used as an index of the magnitude of sexual selection, sexual dichromatism is a composite trait. Here, we examine the evolution of sexual dichromatism in one of the largest and most ecologically diverse families of birds, the tanagers, using the avian visual perspective and a species-level phylogeny. Our results demonstrate that the evolutionary decreases of sexual dichromatism are more often associated with larger and more frequent changes in male plumage coloration, and evolutionary increases are not more often associated with larger changes in either sex. Furthermore, we show that the crown and ventral plumage regions are correlated with sexual dichromatism in males, and that only male plumage complexity is positively correlated with sexual dichromatism. Finally, we demonstrate that light environment is important in shaping both plumage brilliance and complexity. By conducting a multilevel analysis of plumage evolution in males and females, we show that sexual dichromatism evolves via a mosaic of sexual and natural selection in both sexes. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

SEXUAL SELECTION THROUGH FEMALE CHOICE IN LAWES' PAROTIA, A LEK-MATING BIRD OF PARADISE.

PubMed

Pruett-Jones, S G; Pruett-Jones, M A

1990-05-01

We studied sexual selection in Lawes' Parotia, a lek-mating bird of paradise, during 1981-1983 in Papua New Guinea. There was a high variance in mating success among males, with fewer than half of the individuals mating in any one year. This variance was independent of male-male interactions and disruptions. A role of female choice in sexual selection was suggested by the patterns of female visitation to courts and statistical correlations across males between phenotypic traits and mating success. Females repeatedly visited most males in their home ranges and began visiting males up to six weeks before mating. In one or more years, six aspects of male behavior and one morphological variable were positively correlated with mating success, but the probability values were not significant using a simultaneous inference test. Calculation of combined probability values across all three years revealed that one aspect of male display behavior, the probability of display, positively and significantly influenced mating status. The probability of display was also significantly correlated with relative mating success among males. Females showed strong fidelity to mates, both within and between seasons. Display sites of male Lawes' Parotia are variably dispersed, but mating success did not differ for grouped and solitary males. These data confirm an important role of female choice in sexual selection in birds of paradise but also suggest that female choice may be unrelated to the process of lek-initiation in this species. © 1990 The Society for the Study of Evolution.

Sexual selection explains sex-specific growth plasticity and positive allometry for sexual size dimorphism in a reef fish

PubMed Central

Walker, Stefan P. W.; McCormick, Mark I.

2009-01-01

In 1950, Rensch noted that in clades where males are the larger sex, sexual size dimorphism (SSD) tends to be more pronounced in larger species. This fundamental allometric relationship is now known as ‘Rensch's rule’. While most researchers attribute Rensch's rule to sexual selection for male size, experimental evidence is lacking. Here, we suggest that ultimate hypotheses for Rensch's rule should also apply to groups of individuals and that individual trait plasticity can be used to test those hypotheses experimentally. Specifically, we show that in the sex-changing fish Parapercis cylindrica, larger males have larger harems with larger females, and that SSD increases with harem size. Thus, sexual selection for male body size is the ultimate cause of sexual size allometry. In addition, we experimentally illustrate a positive relationship between polygyny potential and individual growth rate during sex change from female to male. Thus, sexual selection is the ultimate cause of variation in growth rate, and variation in growth rate is the proximate cause of sexual size allometry. Taken together, our results provide compelling evidence in support of the sexual selection hypothesis for Rensch's rule and highlight the potential importance of individual growth modification in the shaping of morphological patterns in Nature. PMID:19553253

Sexual selection and population divergence II. Divergence in different sexual traits and signal modalities in field crickets (Teleogryllus oceanicus).

PubMed

Pascoal, Sonia; Mendrok, Magdalena; Wilson, Alastair J; Hunt, John; Bailey, Nathan W

2017-06-01

Sexual selection can target many different types of traits. However, the relative influence of different sexually selected traits during evolutionary divergence is poorly understood. We used the field cricket Teleogryllus oceanicus to quantify and compare how five traits from each of three sexual signal modalities and components diverge among allopatric populations: male advertisement song, cuticular hydrocarbon (CHC) profiles and forewing morphology. Population divergence was unexpectedly consistent: we estimated the among-population (genetic) variance-covariance matrix, D, for all 15 traits, and D max explained nearly two-thirds of its variation. CHC and wing traits were most tightly integrated, whereas song varied more independently. We modeled the dependence of among-population trait divergence on genetic distance estimated from neutral markers to test for signatures of selection versus neutral divergence. For all three sexual trait types, phenotypic variation among populations was largely explained by a neutral model of divergence. Our findings illustrate how phenotypic integration across different types of sexual traits might impose constraints on the evolution of mating isolation and divergence via sexual selection. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

Sexual selection predicts brain structure in dragon lizards.

PubMed

Hoops, D; Ullmann, J F P; Janke, A L; Vidal-Garcia, M; Stait-Gardner, T; Dwihapsari, Y; Merkling, T; Price, W S; Endler, J A; Whiting, M J; Keogh, J S

2017-02-01

Phenotypic traits such as ornaments and armaments are generally shaped by sexual selection, which often favours larger and more elaborate males compared to females. But can sexual selection also influence the brain? Previous studies in vertebrates report contradictory results with no consistent pattern between variation in brain structure and the strength of sexual selection. We hypothesize that sexual selection will act in a consistent way on two vertebrate brain regions that directly regulate sexual behaviour: the medial preoptic nucleus (MPON) and the ventromedial hypothalamic nucleus (VMN). The MPON regulates male reproductive behaviour whereas the VMN regulates female reproductive behaviour and is also involved in male aggression. To test our hypothesis, we used high-resolution magnetic resonance imaging combined with traditional histology of brains in 14 dragon lizard species of the genus Ctenophorus that vary in the strength of precopulatory sexual selection. Males belonging to species that experience greater sexual selection had a larger MPON and a smaller VMN. Conversely, females did not show any patterns of variation in these brain regions. As the volumes of both these regions also correlated with brain volume (BV) in our models, we tested whether they show the same pattern of evolution in response to changes in BV and found that the do. Therefore, we show that the primary brain nuclei underlying reproductive behaviour in vertebrates can evolve in a mosaic fashion, differently between males and females, likely in response to sexual selection, and that these same regions are simultaneously evolving in concert in relation to overall brain size. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

Is sexual selection driving diversification of the bioluminescent ponyfishes (Teleostei: Leiognathidae)?

PubMed

Chakrabarty, Prosanta; Davis, Matthew P; Smith, W Leo; Baldwin, Zachary H; Sparks, John S

2011-07-01

Sexual selection may facilitate genetic isolation among populations and result in increased rates of diversification. As a mechanism driving diversification, sexual selection has been invoked and upheld in numerous empirical studies across disparate taxa, including birds, plants and spiders. In this study, we investigate the potential impact of sexual selection on the tempo and mode of ponyfish evolution. Ponyfishes (Leiognathidae) are bioluminescent marine fishes that exhibit sexually dimorphic features of their unique light-organ system (LOS). Although sexual selection is widely considered to be the driving force behind ponyfish speciation, this hypothesis has never been formally tested. Given that some leiognathid species have a sexually dimorphic LOS, whereas others do not, this family provides an excellent system within which to study the potential role of sexual selection in diversification and morphological differentiation. In this study, we estimate the phylogenetic relationships and divergence times for Leiognathidae, investigate the tempo and mode of ponyfish diversification, and explore morphological shape disparity among leiognathid clades. We recover strong support for a monophyletic Leiognathidae and estimate that all major ponyfish lineages evolved during the Paleogene. Our studies of ponyfish diversification demonstrate that there is no conclusive evidence that sexually dimorphic clades are significantly more species rich than nonsexually dimorphic lineages and that evidence is lacking to support any significant diversification rate increases within ponyfishes. Further, we detected a lineage-through-time signal indicating that ponyfishes have continuously diversified through time, which is in contrast to many recent diversification studies that identify lineage-through-time patterns that support mechanisms of density-dependent speciation. Additionally, there is no evidence of sexual selection hindering morphological diversity, as sexually dimorphic taxa are shown to be more disparate in overall shape morphology than nonsexually dimorphic taxa. Our results suggest that if sexual selection is occurring in ponyfish evolution, it is likely acting only as a genetic isolating mechanism that has allowed ponyfishes to continuously diversify over time, with no overall impact on increases in diversification rate or morphological disparity. © 2011 Blackwell Publishing Ltd.

Experimental removal and elevation of sexual selection: does sexual selection generate manipulative males and resistant females?

PubMed

Crudgington, Helen S; Beckerman, Andrew P; Brüstle, Lena; Green, Kathleen; Snook, Rhonda R

2005-05-01

Sexual conflict over reproduction can occur between males and females. In several naturally promiscuous insect species, experimental evolution studies that have enforced monogamy found evidence for sexual conflict. Here, we subjected the naturally promiscuous, sperm-heteromorphic fruit fly Drosophila pseudoobscura to enforced monogamy, standard levels of promiscuity, and elevated opportunities for promiscuity in four replicate lines. We examined the effect of male and female selection history and the proximate effect of variation in male density on female fitness parameters. We found that male density rather than male selection history explained a greater degree of female fecundity, egg hatching success, and productivity. Additionally, females selected under elevated promiscuity had greater fecundity and hatching success than did enforced monogamy females. Selection line males do not differ in their capacity to coerce females to remate, suggesting no divergence in precopulatory manipulative ability. However, these males did vary in their ability to suppress female remating, suggesting postcopulatory manipulation. These results indicate that sexual conflict can be manifested through both the proximate effects of male density and the historical levels of sexual selection and that the sexes respond differentially to these factors and further stress the multifarious channels of sexual communication that contribute to fitness.

Darwin's explanation of races by means of sexual selection.

PubMed

Millstein, Roberta L

2012-09-01

In Darwin's Sacred Cause, Adrian Desmond and James Moore contend that "Darwin would put his utmost into sexual selection because the subject intrigued him, no doubt, but also for a deeper reason: the theory vindicated his lifelong commitment to human brotherhood" (2009: p. 360). Without questioning Desmond and Moore's evidence, I will raise some puzzles for their view. I will show that attention to the structure of Darwin's arguments in the Descent of Man shows that they are far from straightforward. As Desmond and Moore note, Darwin seems to have intended sexual selection in non-human animals to serve as evidence for sexual selection in humans. However, Darwin's account of sexual selection in humans was different from the canonical cases that Darwin described at great length. If explaining the origin of human races was the main reason for introducing sexual selection, and if sexual selection was a key piece of Darwin's anti-slavery arguments, then it is puzzling why Darwin would have spent so much time discussing cases that did not really support his argument for the origin of human races, and it is also puzzling that his argument for the origin of human races would be so (atypically) poor. Copyright © 2012 Elsevier Ltd. All rights reserved.

Multivariate selection drives concordant patterns of pre- and postcopulatory sexual selection in a livebearing fish.

PubMed

Devigili, Alessandro; Evans, Jonathan P; Di Nisio, Andrea; Pilastro, Andrea

2015-09-15

In many species, females mate with multiple partners, meaning that sexual selection on male traits operates across a spectrum that encompasses the competition for mates (that is, before mating) and fertilizations (after mating). Despite being inextricably linked, pre- and postcopulatory sexual selection are typically studied independently, and we know almost nothing about how sexual selection operates across this divide. Here we bridge this knowledge gap using the livebearing fish Poecilia reticulata. We show that both selective episodes, as well as their covariance, explain a significant component of variance in male reproductive fitness. Moreover, linear and nonlinear selection simultaneously act on pre- and postcopulatory traits, and interact to generate multiple phenotypes with similar fitness.

Evidence for strong intralocus sexual conflict in the Indian meal moth, Plodia interpunctella.

PubMed

Lewis, Zenobia; Wedell, Nina; Hunt, John

2011-07-01

Males and females share a genome and express many shared phenotypic traits, which are often selected in opposite directions. This generates intralocus sexual conflict that may constrain trait evolution by preventing the sexes from reaching their optimal phenotype. Furthermore, if present across multiple loci, intralocus sexual conflict can result in a gender load that may diminish the benefits of sexual selection and help maintain genetic variation for fitness. Despite the importance of intralocus sexual conflict, surprisingly few empirical studies conclusively demonstrate its operation. We show that the pattern of multivariate selection acting on three sexually dimorphic life-history traits (development time, body size, and longevity) in the Indian meal moth, Plodia interpunctella, is opposing for the sexes. Moreover, we combined our estimates of selection with the additive genetic variance-covariance matrix (G) to predict the evolutionary response of the life-history traits in the sexes and showed that the angle between the vector of responses and the vector of sexually antagonistic selection was almost orthogonal at 84.70°. Thus, G biases the predicted response of life-history traits in the sexes away from the direction of sexually antagonistic selection, confirming the presence of strong intralocus sexual conflict in this species. Despite this, sexual dimorphism has evolved in all of the life-history traits examined suggesting that mechanism(s) have evolved to resolve this conflict and allow the sexes to reach their life-history optima. We argue that intralocus sexual conflict is likely to play an important role in the evolution of divergent life-history strategies between the sexes in this species. © 2011 The Author(s). Evolution© 2011 The Society for the Study of Evolution.

Sexual Selection on male cuticular hydrocarbons via male-male competition and female choice.

PubMed

Lane, S M; Dickinson, A W; Tregenza, T; House, C M

2016-07-01

Traditional views of sexual selection assumed that male-male competition and female mate choice work in harmony, selecting upon the same traits in the same direction. However, we now know that this is not always the case and that these two mechanisms often impose conflicting selection on male sexual traits. Cuticular hydrocarbons (CHCs) have been shown to be linked to both social dominance and male attractiveness in several insect species. However, although several studies have estimated the strength and form of sexual selection imposed on male CHCs by female mate choice, none have established whether these chemical traits are also subject to sexual selection via male-male competition. Using a multivariate selection analysis, we estimate and compare sexual selection exerted by male-male competition and female mate choice on male CHC composition in the broad-horned flour beetle Gnatocerus cornutus. We show that male-male competition exerts strong linear selection on both overall CHC abundance and body size in males, while female mate choice exerts a mixture of linear and nonlinear selection, targeting not just the overall amount of CHCs expressed but the relative abundance of specific hydrocarbons as well. We discuss the potential implications of this antagonistic selection with regard to male reproductive success. © 2016 The Authors. Journal of Evolutionary Biology published by John Wiley & Sons Ltd on behalf of European Society for Evolutionary Biology.

Sexual trauma disclosure in clinical settings: addressing diversity.

PubMed

Roberts, Sushma T; Watlington, Christina G; Nett, Sara D; Batten, Sonja V

2010-01-01

Although sexual trauma is an experience with wide prevalence, it remains difficult for many individuals to discuss this trauma openly with others. Disclosure of a sexual trauma history to a receptive individual can lead to both emotional and instrumental support. However, a myriad of factors related not only to current circumstances but also to cultural and individual differences determine whether an individual will choose to share his or her trauma history with someone else. Mental health clinicians may be more likely than many other people to be the recipients of a disclosure of sexual trauma. Thus, ensuring that clinicians show sensitivity to the role that diverse demographic and cultural factors can play in the process of disclosure is important to facilitating a thoughtful and productive response to such an event. The current article reviews a segment of the literature on disclosure of sexual assault and focuses on selected diversity domains (i.e., nonheterosexual orientation, age, gender, and race) that may impact the disclosure of sexual assault. Practical suggestions are proposed to assist clinicians in assessing sexual trauma and facilitating disclosure in a culturally competent manner.

Correlational selection leads to genetic integration of body size and an attractive plumage trait in dark-eyed juncos.

PubMed

McGlothlin, Joel W; Parker, Patricia G; Nolan, Val; Ketterson, Ellen D

2005-03-01

When a trait's effect on fitness depends on its interaction with other traits, the resultant selection is correlational and may lead to the integration of functionally related traits. In relation to sexual selection, when an ornamental trait interacts with phenotypic quality to determine mating success, correlational sexual selection should generate genetic correlations between the ornament and quality, leading to the evolution of honest signals. Despite its potential importance in the evolution of signal honesty, correlational sexual selection has rarely been measured in natural populations. In the dark-eyed junco (Junco hyemalis), males with experimentally elevated values of a plumage trait (whiteness in the tail or "tail white") are more attractive to females and dominant in aggressive encounters over resources. We used restricted maximum-likelihood analysis of a long-term dataset to measure the heritability of tail white and two components of body size (wing length and tail length), as well as genetic correlations between pairs of these traits. We then used multiple regression to assess directional, quadratic, and correlational selection as they acted on tail white and body size via four components of lifetime fitness (juvenile and adult survival, mating success, and fecundity). We found a positive genetic correlation between tail white and body size (as measured by wing length), which indicates past correlational selection. Correlational selection, which was largely due to sexual selection on males, was also found to be currently acting on the same pair of traits. Larger males with whiter tails sired young with more females, most likely due to a combination of female choice, which favors males with whiter tails, and male-male competition, which favors both tail white and larger body size. To our knowledge, this is the first study to show both genetic correlations between sexually selected traits and currently acting correlational sexual selection, and we suggest that correlational sexual selection frequently may be an important mechanism for maintaining the honesty of sexual signals.

The effect of parasites on sex differences in selection.

PubMed

Sharp, N P; Vincent, C M

2015-04-01

The life history strategies of males and females are often divergent, creating the potential for sex differences in selection. Deleterious mutations may be subject to stronger selection in males, owing to sexual selection, which can improve the mean fitness of females and reduce mutation load in sexual populations. However, sex differences in selection might also maintain sexually antagonistic genetic variation, creating a sexual conflict load. The overall impact of separate sexes on fitness is unclear, but the net effect is likely to be positive when there is a large sex difference in selection against deleterious mutations. Parasites can also have sex-specific effects on fitness, and there is evidence that parasites can intensify the fitness consequences of deleterious mutations. Using lines that accumulated mutations for over 60 generations, we studied the effect of the pathogenic bacterium Pseudomonas aeruginosa on sex differences in selection in the fruit fly Drosophila melanogaster. Pseudomonas infection increased the sex difference in selection, but may also have weakened the intersexual correlation for fitness. Our results suggest that parasites may increase the benefits of sexual selection.

Genetic Architecture of Sexual Selection: QTL Mapping of Male Song and Female Receiver Traits in an Acoustic Moth

PubMed Central

Limousin, Denis; Streiff, Réjane; Courtois, Brigitte; Dupuy, Virginie; Alem, Sylvain; Greenfield, Michael D.

2012-01-01

Models of indirect (genetic) benefits sexual selection predict linkage disequilibria between genes that influence male traits and female preferences, owing to non-random mate choice or physical linkage. Such linkage disequilibria can accelerate the evolution of traits and preferences to exaggerated levels. Both theory and recent empirical findings on species recognition suggest that such linkage disequilibria may result from physical linkage or pleiotropy, but very little work has addressed this possibility within the context of sexual selection. We studied the genetic architecture of sexually selected traits by analyzing signals and preferences in an acoustic moth, Achroia grisella, in which males attract females with a train of ultrasound pulses and females prefer loud songs and a fast pulse rhythm. Both male signal characters and female preferences are repeatable and heritable traits. Moreover, female choice is based largely on male song, while males do not appear to provide direct benefits at mating. Thus, some genetic correlation between song and preference traits is expected. We employed a standard crossing design between inbred lines and used AFLP markers to build a linkage map for this species and locate quantitative trait loci (QTL) that influence male song and female preference. Our analyses mostly revealed QTLs of moderate strength that influence various male signal and female receiver traits, but one QTL was found that exerts a major influence on the pulse-pair rate of male song, a critical trait in female attraction. However, we found no evidence of specific co-localization of QTLs influencing male signal and female receiver traits on the same linkage groups. This finding suggests that the sexual selection process would proceed at a modest rate in A. grisella and that evolution toward exaggerated character states may be tempered. We suggest that this equilibrium state may be more the norm than the exception among animal species. PMID:22957082

Evolution of female multiple mating: A quantitative model of the “sexually selected sperm” hypothesis

PubMed Central

Bocedi, Greta; Reid, Jane M

2015-01-01

Explaining the evolution and maintenance of polyandry remains a key challenge in evolutionary ecology. One appealing explanation is the sexually selected sperm (SSS) hypothesis, which proposes that polyandry evolves due to indirect selection stemming from positive genetic covariance with male fertilization efficiency, and hence with a male's success in postcopulatory competition for paternity. However, the SSS hypothesis relies on verbal analogy with “sexy-son” models explaining coevolution of female preferences for male displays, and explicit models that validate the basic SSS principle are surprisingly lacking. We developed analogous genetically explicit individual-based models describing the SSS and “sexy-son” processes. We show that the analogy between the two is only partly valid, such that the genetic correlation arising between polyandry and fertilization efficiency is generally smaller than that arising between preference and display, resulting in less reliable coevolution. Importantly, indirect selection was too weak to cause polyandry to evolve in the presence of negative direct selection. Negatively biased mutations on fertilization efficiency did not generally rescue runaway evolution of polyandry unless realized fertilization was highly skewed toward a single male, and coevolution was even weaker given random mating order effects on fertilization. Our models suggest that the SSS process is, on its own, unlikely to generally explain the evolution of polyandry. PMID:25330405

Sexual selection modulates genetic conflicts and patterns of genomic imprinting.

PubMed

Faria, Gonçalo S; Varela, Susana A M; Gardner, Andy

2017-03-01

Recent years have seen a surge of interest in linking the theories of kin selection and sexual selection. In particular, there is a growing appreciation that kin selection, arising through demographic factors such as sex-biased dispersal, may modulate sexual conflicts, including in the context of male-female arms races characterized by coevolutionary cycles. However, evolutionary conflicts of interest need not only occur between individuals, but may also occur within individuals, and sex-specific demography is known to foment such intragenomic conflict in relation to social behavior. Whether and how this logic holds in the context of sexual conflict-and, in particular, in relation to coevolutionary cycles-remains obscure. We develop a kin-selection model to investigate the interests of different genes involved in sexual and intragenomic conflict, and we show that consideration of these conflicting interests yields novel predictions concerning parent-of-origin specific patterns of gene expression and the detrimental effects of different classes of mutation and epimutation at loci underpinning sexually selected phenotypes. © 2016 The Author(s). Evolution published by Wiley Periodicals, Inc. on behalf of The Society for the Study of Evolution.

Genetic evidence for extreme polyandry and extraordinary sex-role reversal in a pipefish.

PubMed

Jones, A G; Walker, D; Avise, J C

2001-12-22

Due to the phenomenon of male pregnancy, the fish family Syngnathidae (seahorses and pipefishes) has historically been considered an archetypal example of a group in which sexual selection should act more strongly on females than on males. However, more recent work has called into question the idea that all species with male pregnancy are sex-role reversed with respect to the intensity of sexual selection. Furthermore, no studies have formally quantified the opportunity for sexual selection in any natural breeding assemblage of pipefishes or seahorses in order to demonstrate conclusively that sexual selection acts most strongly on females. Here, we use a DNA-based study of parentage in the Gulf pipefish Syngnathus scovelli in order to show that sexual selection indeed acts more strongly on females than on males in this species. Moreover, the Gulf pipefish exhibits classical polyandry with the greatest asymmetry in reproductive roles (as quantified by variances in mating success) between males and females yet documented in any system. Thus, the intensity of sexual selection on females in pipefish rivals that of any other taxon yet studied.

Genetic evidence for extreme polyandry and extraordinary sex-role reversal in a pipefish.

PubMed Central

Jones, A. G.; Walker, D.; Avise, J. C.

2001-01-01

Due to the phenomenon of male pregnancy, the fish family Syngnathidae (seahorses and pipefishes) has historically been considered an archetypal example of a group in which sexual selection should act more strongly on females than on males. However, more recent work has called into question the idea that all species with male pregnancy are sex-role reversed with respect to the intensity of sexual selection. Furthermore, no studies have formally quantified the opportunity for sexual selection in any natural breeding assemblage of pipefishes or seahorses in order to demonstrate conclusively that sexual selection acts most strongly on females. Here, we use a DNA-based study of parentage in the Gulf pipefish Syngnathus scovelli in order to show that sexual selection indeed acts more strongly on females than on males in this species. Moreover, the Gulf pipefish exhibits classical polyandry with the greatest asymmetry in reproductive roles (as quantified by variances in mating success) between males and females yet documented in any system. Thus, the intensity of sexual selection on females in pipefish rivals that of any other taxon yet studied. PMID:11749706

The evolution of female ornaments and weaponry: social selection, sexual selection and ecological competition.

PubMed

Tobias, Joseph A; Montgomerie, Robert; Lyon, Bruce E

2012-08-19

Ornaments, weapons and aggressive behaviours may evolve in female animals by mate choice and intrasexual competition for mating opportunities-the standard forms of sexual selection in males. However, a growing body of evidence suggests that selection tends to operate in different ways in males and females, with female traits more often mediating competition for ecological resources, rather than mate acquisition. Two main solutions have been proposed to accommodate this disparity. One is to expand the concept of sexual selection to include all mechanisms related to fecundity; another is to adopt an alternative conceptual framework-the theory of social selection-in which sexual selection is one component of a more general form of selection resulting from all social interactions. In this study, we summarize the history of the debate about female ornaments and weapons, and discuss potential resolutions. We review the components of fitness driving ornamentation in a wide range of systems, and show that selection often falls outside the limits of traditional sexual selection theory, particularly in females. We conclude that the evolution of these traits in both sexes is best understood within the unifying framework of social selection.

The mechanism of sound production in túngara frogs and its role in sexual selection and speciation.

PubMed

Ryan, Michael J; Guerra, Mónica A

2014-10-01

Sexual communication can evolve in response to sexual selection, and it can also cause behavioral reproductive isolation between populations and thus drive speciation. Anurans are an excellent system to investigate these links between behavior and evolution because we have detailed knowledge of how neural mechanisms generate behavioral preferences for calls and how these preferences then generate selection on call variation. But we know far less about the physical mechanisms of call production, especially how different laryngeal morphologies generate call variation. Here we review studies of a group of species that differ in the presence of a secondary call component that evolved under sexual selection. We discuss how the larynx produces this call component, and how laryngeal morphology generates sexual selection and can contribute to speciation. Copyright © 2014. Published by Elsevier Ltd.

Standards for Clinical Trials in Male and Female Sexual Dysfunction: III. Unique Aspects of Clinical Trials in Male Sexual Dysfunction.

PubMed

Fisher, William A; Gruenwald, Ilan; Jannini, Emmanuele A; Lev-Sagie, Ahinoam; Lowenstein, Lior; Pyke, Robert E; Reisman, Yakov; Revicki, Dennis A; Rubio-Aurioles, Eusebio

2017-01-01

This series of articles, Standards for Clinical Trials in Male and Female Sexual Dysfunction, began with the discussion of a common expected standard for clinical trial design in male and female sexual dysfunction, a common rationale for the design of phase I to IV clinical trials, and common considerations for the selection of study population and study duration in male and female sexual dysfunction. The second article in this series discussed fundamental principles in development, validation, and selection of patient- (and partner-) reported outcome assessment. The third and present article in this series discusses selected aspects of sexual dysfunction that are that are unique to male sexual dysfunctions and relevant to the conduct of clinical trials of candidate treatments for men. Copyright © 2016 International Society for Sexual Medicine. Published by Elsevier Inc. All rights reserved.

Selected Risk and Protective Factors Associated with Two or More Lifetime Sexual Intercourse Partners and Non-Condom Use during Last Coitus among U.S. Rural High School Students

ERIC Educational Resources Information Center

Yarber, William L.; Milhausen, Robin; Crosby, Richard A.; DiClemente, Ralph J.

2002-01-01

This analysis determined the association between 13 selected health risk and protective factors and reporting two or more lifetime sexual intercourse partners and non-condom use for last coitus among sexually experienced U.S. rural high school students. The sample was 569 sexually experienced adolescent females and 561 sexually experienced…

a Genetic Algorithm Based on Sexual Selection for the Multidimensional 0/1 Knapsack Problems

NASA Astrophysics Data System (ADS)

Varnamkhasti, Mohammad Jalali; Lee, Lai Soon

In this study, a new technique is presented for choosing mate chromosomes during sexual selection in a genetic algorithm. The population is divided into groups of males and females. During the sexual selection, the female chromosome is selected by the tournament selection while the male chromosome is selected based on the hamming distance from the selected female chromosome, fitness value or active genes. Computational experiments are conducted on the proposed technique and the results are compared with some selection mechanisms commonly used for solving multidimensional 0/1 knapsack problems published in the literature.

Pollen transfer efficiency and its effect on inflorescence size in deceptive pollination strategies.

PubMed

Scopece, G; Schiestl, F P; Cozzolino, S

2015-03-01

Pollination systems differ in pollen transfer efficiency, a variable that may influence the evolution of flower number. Here we apply a comparative approach to examine the link between pollen transfer efficiency and the evolution of inflorescence size in food and sexually deceptive orchids. We examined pollination performance in nine food-deceptive, and eight sexually deceptive orchids by recording pollen removal and deposition in the field. We calculated correlations between reproductive success and flower number (as a proxy for resources allocated during reproductive process), and directional selection differentials were estimated on flower number for four species. Results indicate that sexually deceptive species experience decreased pollen loss compared to food-deceptive species. Despite producing fewer flowers, sexually deceptive species attained levels of overall pollination success (through male and female function) similar to food-deceptive species. Furthermore, a positive correlation between flower number and pollination success was observed in food-deceptive species, but this correlation was not detected in sexually deceptive species. Directional selection differentials for flower number were significantly higher in food compared to sexually deceptive species. We suggest that pollination systems with more efficient pollen transfer and no correlation between pollination success and number of flowers produced, such as sexual deception, may allow the production of inflorescences with fewer flowers that permit the plant to allocate fewer resources to floral displays and, at the same time, limit transpiration. This strategy can be particularly important for ecological success in Mediterranean water-deprived habitats, and might explain the high frequency of sexually deceptive species in these specialised ecosystems. © 2014 German Botanical Society and The Royal Botanical Society of the Netherlands.

Validity for an integrated laboratory analogue of sexual aggression and bystander intervention.

PubMed

Parrott, Dominic J; Tharp, Andra Teten; Swartout, Kevin M; Miller, Cameron A; Hall, Gordon C Nagayama; George, William H

2012-01-01

This study sought to develop and validate an integrated laboratory paradigm of sexual aggression and bystander intervention. Participants were a diverse community sample (54% African American) of heterosexual males (N = 156) between 21 and 35 years of age who were recruited to complete the study with a male friend and an ostensibly single, heterosexual female who reported a strong dislike of sexual content in the media. Participants viewed a sexually explicit or nonsexually explicit film clip as part of contrived media rating task and made individual choices of which film clip to show the female confederate. Immediately thereafter, participants were required to reach consensus on a group decision of which film clip to show the female confederate. Subjecting a target to an unwanted experience with a sexual connotation was operationalized as selection of the sexually explicit video, whereas successful bystander intervention was operationalized as the event of one partner individually selecting the sexually explicit video but then selecting the nonsexually explicit video for the group choice. Results demonstrated that a 1-year history of sexual aggression and endorsement of pertinent misogynistic attitudes significantly predicted selection of the sexually-explicit video. In addition, bystander efficacy significantly predicted men's successful prevention of their male peer's intent to show the female confederate a sexually explicit video. Discussion focused on how these data inform future research and bystander intervention programming for sexual aggression. © 2012 Wiley Periodicals, Inc.

Evolutionary inevitability of sexual antagonism.

PubMed

Connallon, Tim; Clark, Andrew G

2014-02-07

Sexual antagonism, whereby mutations are favourable in one sex and disfavourable in the other, is common in natural populations, yet the root causes of sexual antagonism are rarely considered in evolutionary theories of adaptation. Here, we explore the evolutionary consequences of sex-differential selection and genotype-by-sex interactions for adaptation in species with separate sexes. We show that sexual antagonism emerges naturally from sex differences in the direction of selection on phenotypes expressed by both sexes or from sex-by-genotype interactions affecting the expression of such phenotypes. Moreover, modest sex differences in selection or genotype-by-sex effects profoundly influence the long-term evolutionary trajectories of populations with separate sexes, as these conditions trigger the evolution of strong sexual antagonism as a by-product of adaptively driven evolutionary change. The theory demonstrates that sexual antagonism is an inescapable by-product of adaptation in species with separate sexes, whether or not selection favours evolutionary divergence between males and females.

The evolution of female ornaments and weaponry: social selection, sexual selection and ecological competition

PubMed Central

Tobias, Joseph A.; Montgomerie, Robert; Lyon, Bruce E.

2012-01-01

Ornaments, weapons and aggressive behaviours may evolve in female animals by mate choice and intrasexual competition for mating opportunities—the standard forms of sexual selection in males. However, a growing body of evidence suggests that selection tends to operate in different ways in males and females, with female traits more often mediating competition for ecological resources, rather than mate acquisition. Two main solutions have been proposed to accommodate this disparity. One is to expand the concept of sexual selection to include all mechanisms related to fecundity; another is to adopt an alternative conceptual framework—the theory of social selection—in which sexual selection is one component of a more general form of selection resulting from all social interactions. In this study, we summarize the history of the debate about female ornaments and weapons, and discuss potential resolutions. We review the components of fitness driving ornamentation in a wide range of systems, and show that selection often falls outside the limits of traditional sexual selection theory, particularly in females. We conclude that the evolution of these traits in both sexes is best understood within the unifying framework of social selection. PMID:22777016

Sexual Selection and the differences between the sexes in Mandrills (Mandrillus sphinx).

PubMed

Setchell, Joanna M

2016-01-01

Sexual selection has become a major focus in evolutionary and behavioral ecology. It is also a popular research topic in primatology. I use studies of mandrills (Mandrillus sphinx), a classic example of extravagant armaments and ornaments in animals, to exemplify how a long-term, multidisciplinary approach that integrates field observations with laboratory methods can contribute to on-going theoretical debates in the field of sexual selection. I begin with a brief summary of the main concepts of sexual selection theory and the differences between the sexes. I then introduce mandrills and the study population and review mandrill life history, the ontogeny of sex differences, and maternal effects. Next, I focus on male-male competition and female choice, followed by the less well-studied questions of female-female competition and male choice. This review shows how different reproductive priorities lead to very different life histories and divergent adaptations in males and females. It demonstrates how broadening traditional perspectives on sexual selection beyond the ostentatious results of intense sexual selection on males leads to an understanding of more subtle and cryptic forms of competition and choice in both sexes and opens many productive avenues in the study of primate reproductive strategies. These include the potential for studies of postcopulatory selection, female intrasexual competition, and male choice. These studies of mandrills provide comparison and, I hope, inspiration for studies of both other polygynandrous species and species with mating systems less traditionally associated with sexual selection. © 2016 Wiley Periodicals, Inc.

Bold colors in a cryptic lineage: do Eastern Indigo Snakes exhibit color dimorphism?

PubMed

Deitloff, Jennifer; Johnson, Valerie M; Guyer, Craig

2013-01-01

Many species exhibit variation in the color of their scales, feathers, or fur. Various forms of natural selection, such as mimicry, crypsis, and species recognition, as well as sexual selection, can influence the evolution of color. Eastern Indigo Snakes (Drymarchon couperi), a federally threatened species, have coloration on the sides of the head and the chin that can vary from black to red or cream. Despite significant conservations efforts for this species, little is known about its biology in the field. Past researchers have proposed that the color variation on the head and chin is associated with the sex of the individual. Alternatively, color might vary among individuals because it is controlled by genes that are under natural selection or neutral evolution. We tested these alternative hypotheses by examining whether coloration of the sublabial, submaxillary, and ventral scales of this species differed by sex or among clutches. We used color spectrometry to characterize important aspects of color in two ways: by examining overall color differences across the entire color spectrum and by comparing differences within the ultraviolet, yellow, and red colorbands. We found that Eastern Indigo Snakes do not exhibit sexual dichromatism, but their coloration does vary among clutches; therefore, the pattern of sexual selection leading to sexual dichromatism observed in many squamates does not appear to play a role in the evolution and maintenance of color variation in Eastern Indigo Snakes. We suggest that future studies should focus on determining whether color variation in these snakes is determined by maternal effects or genetic components and if color is influenced by natural selection or neutral evolutionary processes. Studying species that exhibit bright colors within lineages that are not known for such coloration will contribute greatly to our understanding of the evolutionary and ecological factors that drive these differences.

Additive genetic variance in polyandry enables its evolution, but polyandry is unlikely to evolve through sexy or good sperm processes.

PubMed

Travers, L M; Simmons, L W; Garcia-Gonzalez, F

2016-05-01

Polyandry is widespread despite its costs. The sexually selected sperm hypotheses ('sexy' and 'good' sperm) posit that sperm competition plays a role in the evolution of polyandry. Two poorly studied assumptions of these hypotheses are the presence of additive genetic variance in polyandry and sperm competitiveness. Using a quantitative genetic breeding design in a natural population of Drosophila melanogaster, we first established the potential for polyandry to respond to selection. We then investigated whether polyandry can evolve through sexually selected sperm processes. We measured lifetime polyandry and offensive sperm competitiveness (P2 ) while controlling for sampling variance due to male × male × female interactions. We also measured additive genetic variance in egg-to-adult viability and controlled for its effect on P2 estimates. Female lifetime polyandry showed significant and substantial additive genetic variance and evolvability. In contrast, we found little genetic variance or evolvability in P2 or egg-to-adult viability. Additive genetic variance in polyandry highlights its potential to respond to selection. However, the low levels of genetic variance in sperm competitiveness suggest that the evolution of polyandry may not be driven by sexy sperm or good sperm processes. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

A Comparative Analysis of Sexual Harassment Policies at Selected Higher Education Institutions in South Africa

ERIC Educational Resources Information Center

Wilken, E. C.; Badenhorst, J. W.

2003-01-01

This article investigates sexual harassment issues by means of an in depth literature review and by analyzing and comparing the sexual harassment policies of selected universities in South Africa. Various alternatives that categorize sexual harassment are proposed in order to form a clear perspective on the different viewpoints that currently…

Systematic development of a self-help and motivational enhancement intervention to promote sexual health in HIV-positive men who have sex with men.

PubMed

Van Kesteren, Nicole M C; Kok, Gerjo; Hospers, Harm J; Schippers, Jan; De Wildt, Wencke

2006-12-01

The objective of this study was to describe the application of a systematic process-Intervention Mapping-to developing a theory- and evidence-based intervention to promote sexual health in HIV-positive men who have sex with men (MSM). Intervention Mapping provides a framework that gives program planners a systematic method for decision-making in each phase of intervention development. In Step 1, we focused on the improvement of two health-promoting behaviors: satisfactory sexual functioning and safer sexual behavior. These behaviors were then linked with selected personal and external determinants, such as attitudes and social support, to produce a set of proximal program objectives. In Step 2, theoretical methods were identified to influence the proximal program objectives and were translated into practical strategies. Although theoretical methods were derived from various theories, self-regulation theory and a cognitive model of behavior change provided the main framework for selecting the intervention methods. The main strategies chosen were bibliotherapy (i.e., the use of written material to help people solve problems or change behavior) and motivational interviewing. In Step 3, the theoretical methods and practical strategies were applied in a program that comprised a self-help guide, a motivational interviewing session and a motivational interviewing telephone call, both delivered by specialist nurses in HIV treatment centers. In Step 4, implementation was anticipated by developing a linkage group to ensure involvement of program users in the planning process and conducting additional research to understand how to implement our program better. In Step 5, program evaluation was anticipated based on the planning process from the previous Intervention Mapping steps.

Detection of Allelic Frequency Differences between the Sexes in Humans: A Signature of Sexually Antagonistic Selection.

PubMed

Lucotte, Elise A; Laurent, Romain; Heyer, Evelyne; Ségurel, Laure; Toupance, Bruno

2016-06-02

Sexually antagonistic (SA) selection, a form of selection that can occur when both sexes have different fitness optima for a trait, is a major force shaping the evolution of organisms. A seminal model developed by Rice (Rice WR. 1984. Sex chromosomes and the evolution of sexual dimorphism. Evolution 38:735-742.) predicts that the X chromosome should be a hotspot for the accumulation of loci under SA selection as compared with the autosomes. Here, we propose a methodological framework designed to detect a specific signature of SA selection on viability, differences in allelic frequencies between the sexes. Applying this method on genome-wide single nucleotide polymorphism (SNP) data in human populations where no sex-specific population stratification could be detected, we show that there are overall significantly more SNPs exhibiting differences in allelic frequencies between the sexes on the X chromosome as compared with autosomes, supporting the predictions of Rice's model. This pattern is consistent across populations and is robust to correction for potential biases such as differences in linkage disequilibrium, sample size, and genotyping errors between chromosomes. Although SA selection is not the only factor resulting in allelic frequency differences between the sexes, we further show that at least part of the identified X-linked loci is caused by such a sex-specific processes. © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

From Evolutionary Allometry to Sexual Display: (A Reply to Holman and Bro-Jørgensen).

PubMed

Raia, Pasquale; Passaro, Federico; Carotenuto, Francesco; Meiri, Shai; Piras, Paolo

2016-08-01

Conventional wisdom holds that the complex shapes of deer antlers are produced under the sole influence of sexual selection. We questioned this view by demonstrating that trends for increased body size evolution passively yield more-complex ornaments, even in organisms where no effect of sexual selection is possible, with similar allometric slopes. Recent investigations suggest that sexual selection on antlers of larger deer species is stronger than that in smaller species; hence, the use of conspicuous antlers for display in large male deer is a secondary function driven by especially intense sexual selection on these large-bodied species. Since ancestral deer were small and had very simple antlers, such an intense selection on antlers shape was probably absent in early deer. Therefore, the evolution of complex ornaments is coupled with body size evolution, even in deer.

Experimental stress during molt suggests the evolution of condition-dependent and condition-independent ornaments in the king penguin.

PubMed

Schull, Quentin; Robin, Jean-Patrice; Dobson, F Stephen; Saadaoui, Hédi; Viblanc, Vincent A; Bize, Pierre

2018-01-01

Sexual selection and social selection are two important theories proposed for explaining the evolution of colorful ornamental traits in animals. Understanding signal honesty requires studying how environmental and physiological factors during development influence the showy nature of sexual and social ornaments. We experimentally manipulated physiological stress and immunity status during the molt in adult king penguins ( Aptenodytes patagonicus ), and studied the consequences of our treatments on colourful ornaments (yellow-orange and UV beak spots and yellow-orange auricular feather patches) known to be used in sexual and social contexts in this species. Whereas some ornamental features showed strong condition-dependence (yellow auricular feather chroma, yellow and UV chroma of the beak), others were condition-independent and remained highly correlated before and after the molt (auricular patch size and beak UV hue). Our study provides a rare examination of the links between ornament determinism and selection processes in the wild. We highlight the coexistence of ornaments costly to produce that may be honest signals used in mate choice, and ornaments for which honesty may be enforced by social mediation or rely on genetic constraints.

Do men and women report their sexual partnerships differently? Evidence from Kisumu, Kenya.

PubMed

Clark, Shelley; Kabiru, Caroline; Zulu, Eliya

2011-12-01

It is generally believed that men and women misreport their sexual behaviors, which undermines the ability of researchers, program designers and health care providers to assess whether these behaviors compromise individuals' sexual and reproductive health. Data on 1,299 recent sexual partnerships were collected in a 2007 survey of 1,275 men and women aged 18-24 and living in Kisumu, Kenya. Chi-square and t tests were used to examine how sample selection bias and selective partnership reporting may result in gender differences in reported sexual behaviors. Correlation coefficients and kappa statistics were calculated in further analysis of a sample of 280 matched marital and nonmarital couples to assess agreement on reported behaviors. Even after adjustment for sample selection bias, men reported twice as many partnerships as women (0.5 vs. 0.2), as well as more casual partnerships. However, when selective reporting was controlled for, aggregate gender differences in sexual behaviors almost entirely disappeared. In the matched-couples sample, men and women exhibited moderate to substantial levels of agreement for most relationship characteristics and behaviors, including type of relationship, frequency of sex and condom use. Finally, men and women tended to agree about whether men had other nonmarital partners, but disagreed about women's nonmarital partners. Both sample selection bias and selective partnership reporting can influence the level of agreement between men's and women's reports of sexual behaviors. Although men report more casual partners than do women, accounts of sexual behavior within reported relationships are generally reliable.

The antidepressant fluoxetine alters mechanisms of pre- and post-copulatory sexual selection in the eastern mosquitofish (Gambusia holbrooki).

PubMed

Bertram, Michael G; Ecker, Tiarne E; Wong, Bob B M; O'Bryan, Moira K; Baumgartner, John B; Martin, Jake M; Saaristo, Minna

2018-03-19

Contamination of aquatic habitats with pharmaceuticals is a major environmental concern. Recent studies have detected pharmaceutical pollutants in a wide array of ecosystems and organisms, with many of these contaminants being highly resistant to biodegradation and capable of eliciting sub-lethal effects in non-target species. One such pollutant is fluoxetine, a widely prescribed antidepressant, which is frequently detected in surface waters globally and can alter physiology and behaviour in aquatic organisms. Despite this, relatively little is known about the potential for fluoxetine to disrupt mechanisms of sexual selection. Here, we investigate the impacts of 30-day exposure to two environmentally realistic levels of fluoxetine (low and high) on mechanisms of pre- and post-copulatory sexual selection in the eastern mosquitofish (Gambusia holbrooki). We tested 1) male mating behaviour in the absence or presence of a competitor male, and 2) sperm quality and quantity. We found that high-fluoxetine exposure increased male copulatory behaviour in the absence of a competitor, while no effect was detected under male-male competition. Further, fluoxetine exposure at both concentrations increased total sperm count relative to males from the control group, while no significant change in sperm quality was observed. Lastly, low-fluoxetine males showed a significant reduction in condition index (mass relative to length). Our study is the first to show altered mechanisms of both pre- and post-copulatory sexual selection in an aquatic species resulting from environmentally realistic fluoxetine exposure, highlighting the capacity of pharmaceutical pollution to interfere with sensitive reproductive processes in wildlife. Copyright © 2018 Elsevier Ltd. All rights reserved.

The sexual selection paradigm: have we overlooked other mechanisms in the evolution of male ornaments?

PubMed

Candolin, Ulrika; Tukiainen, Iina

2015-10-07

Extravagant male ornaments expressed during reproduction are almost invariably assumed to be sexually selected and evolve through competition for mating opportunities. Yet in species where male reproductive success depends on the defence of offspring, male ornaments could also evolve through social competition for offspring survival. However, in contrast to female ornaments, this possibility has received little attention in males. We show that a male ornament that is traditionally assumed to be sexually selected--the red nuptial coloration of the three-spined stickleback--is under stronger selection for offspring survival than for mating success. Males express most coloration during parenting, when they no longer attract females, and the colour correlates with nest retention and hatching success but not with attractiveness to females. This contradicts earlier assumptions and suggests that social selection for offspring survival rather than for sexual selection for mating success is the main mechanism maintaining the ornament in the population. These results suggest that we should consider other forms of social selection beyond sexual selection when seeking to explain the function and evolution of male ornaments. An incorrect assignment of selection pressures could hamper our understanding of evolution. © 2015 The Author(s).

Testing a model of the relationship between childhood sexual abuse and psychosis in a first-episode psychosis group: the role of hallucinations and delusions, posttraumatic intrusions, and selective attention.

PubMed

Bendall, Sarah; Hulbert, Carol Anne; Alvarez-Jimenez, Mario; Allott, Kelly; McGorry, Patrick D; Jackson, Henry James

2013-11-01

Several theories suggest that posttraumatic intrusive symptoms are central to the relationship between childhood trauma (CT) and hallucinations and delusions in psychosis. Biased selective attention has been implicated as a cognitive process underlying posttraumatic intrusions. The current study sought to test theories of the relationship between childhood sexual abuse (CSA), hallucinations and delusions, posttraumatic intrusions, and selective attention in first-episode psychosis (FEP). Twenty-eight people with FEP and 21 nonclinical controls were assessed for CT and psychotic and posttraumatic stress symptoms and completed an emotional Stroop test using CSA-related and other words. Those with FEP and CSA had more severe hallucinations and delusions than those with FEP and without CSA. They also reported posttraumatic intrusions at clinical levels and showed selective attention to CSA-related words. The results are consistent with the posttraumatic intrusions account of hallucinations and delusions in those with CSA and psychosis.

Environmental quality alters female costs and benefits of evolving under enforced monogamy.

PubMed

Grazer, Vera M; Demont, Marco; Michalczyk, Łukasz; Gage, Matthew J G; Martin, Oliver Y

2014-02-05

Currently many habitats suffer from quality loss due to environmental change. As a consequence, evolutionary trajectories might shift due to environmental effects and potentially increase extinction risk of resident populations. Nevertheless, environmental variation has rarely been incorporated in studies of sexual selection and sexual conflict, although local environments and individuals' condition undoubtedly influence costs and benefits. Here, we utilise polyandrous and monogamous selection lines of flour beetles, which evolved in presence or absence of sexual selection for 39 generations. We specifically investigated effects of low vs. standard food quality (i.e. stressful vs. benign environments) on reproductive success of cross pairs between beetles from the contrasting female and male selection histories to assess gender effects driving fitness. We found a clear interaction of food quality, male selection history and female selection history. Monogamous females generally performed more poorly than polyandrous counterparts, but reproductive success was shaped by selection history of their mates and environmental quality. When monogamous females were paired with polyandrous males in the standard benign environment, females seemed to incur costs, possibly due to sexual conflict. In contrast, in the novel stressful environment, monogamous females profited from mating with polyandrous males, indicating benefits of sexual selection outweigh costs. Our findings suggest that costs and benefits of sexually selected adaptations in both sexes can be profoundly altered by environmental quality. With regard to understanding possible impacts of environmental change, our results further show that the ecology of mating systems and associated selection pressures should be considered in greater detail.

The Evolution of Sex-Specific Dominance in Response to Sexually Antagonistic Selection.

PubMed

Spencer, Hamish G; Priest, Nicholas K

2016-05-01

Arguments about the evolutionary modification of genetic dominance have a long history in genetics, dating back more than 100 years. Mathematical investigations have shown that modifiers of the level of dominance at the locus of interest can spread at a reasonable rate only if heterozygotes at that locus are common. One hitherto neglected scenario is that of sexually antagonistic selection, which not only is ubiquitous in sexual species but also can generate stable high frequencies of heterozygotes that would appear to facilitate the spread of such modifiers. Here we present a mathematical model that shows that sexually specific dominance modification is a potential outcome of sexually antagonistic selection. Our model predicts that loci with higher levels of sexual conflict should exhibit greater differentiation between males and females in levels of dominance and that the strength of antagonistic selection experienced by one sex should be proportional to the level of dominance modification. We show that evidence from the literature is consistent with these predictions but suggest that empiricists should be alert to the possibility of there being numerous cases of sex-specific dominance. Further, in order to determine the significance of sexual conflict in the evolution of dominance, we need improved measures of sexual conflict and better characterization of loci that modify dominance of genes with sexually antagonistic fitness effects.

Sexual selection, sexual isolation and pheromones in Drosophila melanogaster strains after long-term maintaining on different diets.

PubMed

Trajković, Jelena; Miličić, Dragana; Savić, Tatjana; Pavković-Lučić, Sofija

2017-07-01

Evolution of reproductive isolation may be a consequence of a variety of signals used in courtship and mate preferences. Pheromones play an important role in both sexual selection and sexual isolation. The abundance of pheromones in Drosophila melanogaster may depend on different environmental factors, including diet. The aim of this study was to ascertain to which degree principal pheromones affect sexual selection in D. melanogaster. We used D. melanogaster strains reared for 14 years on four substrates: standard cornmeal substrate and those containing tomato, banana and carrot. We have previously determined that long-term maintaining of these dietary strains resulted in differences in their cuticular hydrocarbons profile (CHs). In this work, we have tested the level of sexual selection and sexual isolation between aforementioned strains. We found that the high levels of cis-vaccenyl acetate, 7-pentacosene and 7,11-nonacosadiene in the strain reared on a substrate containing carrot affected the individual attractiveness and influenced sexual isolation between flies of this strain and flies reared on a substrate containing banana. Based on these results, long-term different diets, may contribute, to sexual behaviour of D. melanogaster via the effects of principal pheromones. Copyright © 2017 Elsevier B.V. All rights reserved.

Parental mediation of adolescent media use and demographic factors as predictors of Kenyan high school students' exposure to sexual content in television.

PubMed

Ngula, Kyalo wa; Mberia, Hellen K; Miller, Ann Neville

2016-01-01

Research in Western nations suggests that parents' involvement in their children's media use can make a difference in how adolescents select, process and respond to sexual television messages. Little or no published research has investigated this issue in sub-Saharan Africa, even though adolescents and young adults remain among the groups at highest risk for HIV transmission. This study investigated the relationship between Kenyan adolescents' level of exposure to sexual television content and their parents' mediation of their television use. A cluster sample of 427 Nairobi public high school students was surveyed regarding parental mediation of their media use and their intake of sexual television content. Co-viewing with opposite sex friends was associated with higher intake of sexual TV content. This relationship was stronger among boarding school students than among day school students. Parental mediation and co-viewing variables predicted three times as much variance among boarding than among day school students.

[The confrontation of sexuality in the professional practice of future physicians: the viewpoint of medical interns].

PubMed

Salinas Urbina, Addis Abeba; Jarillo Soto, Edgar Carlos

2013-03-01

The subject of sexuality in academic and service institutions is perceived through predominantly biological conceptual perspectives, blurring the subjective component that is imbued in social and cultural processes. The meanings that medical staff construct around sexuality have implications in their professional development and practice. This work presents results from a qualitative study into the meaning of sexuality among medical interns from the Universidad Autónoma Metropolitana-Xochimilco. In-depth interviews were conducted with students during their community service. This group was selected because they had finished their studies and were performing an independent and autonomous professional practice. The results, which were analyzed based on Grounded Theory, revealed three dichotomies: biology vs. social construction, individual vs. professional and theoretical learning vs. experiences in the community. The most relevant aspect revealed was the antagonism found between a medical intern's biology-centered academic knowledge and the challenge posed by their patients' reproductive and sexual health needs. The interns recognize that they lack the necessary skills to face issues of sexuality in their professional practice.

Natural allelic variations of xenobiotic-metabolizing enzymes affect sexual dimorphism in Oryzias latipes.

PubMed

Katsumura, Takafumi; Oda, Shoji; Nakagome, Shigeki; Hanihara, Tsunehiko; Kataoka, Hiroshi; Mitani, Hiroshi; Kawamura, Shoji; Oota, Hiroki

2014-12-22

Sexual dimorphisms, which are phenotypic differences between males and females, are driven by sexual selection. Interestingly, sexually selected traits show geographical variations within species despite strong directional selective pressures. This paradox has eluded many evolutionary biologists for some time, and several models have been proposed (e.g. 'indicator model' and 'trade-off model'). However, disentangling which of these theories explains empirical patterns remains difficult, because genetic polymorphisms that cause variation in sexual differences are still unknown. In this study, we show that polymorphisms in cytochrome P450 (CYP) 1B1, which encodes a xenobiotic-metabolizing enzyme, are associated with geographical differences in sexual dimorphism in the anal fin morphology of medaka fish (Oryzias latipes). Biochemical assays and genetic cross experiments show that high- and low-activity CYP1B1 alleles enhanced and declined sex differences in anal fin shapes, respectively. Behavioural and phylogenetic analyses suggest maintenance of the high-activity allele by sexual selection, whereas the low-activity allele possibly has experienced positive selection due to by-product effects of CYP1B1 in inferred ancestral populations. The present data can elucidate evolutionary mechanisms behind genetic variations in sexual dimorphism and indicate trade-off interactions between two distinct mechanisms acting on the two alleles with pleiotropic effects of xenobiotic-metabolizing enzymes. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Sex in murky waters: algal-induced turbidity increases sexual selection in pipefish.

PubMed

Sundin, Josefin; Aronsen, Tonje; Rosenqvist, Gunilla; Berglund, Anders

2017-01-01

Algal-induced turbidity has been shown to alter several important aspects of reproduction and sexual selection. However, while turbidity has been shown to negatively affect reproduction and sexually selected traits in some species, it may instead enhance reproductive success in others, implying that the impact of eutrophication is far more complex than originally believed. In this study, we aimed to provide more insight into these inconsistent findings. We used molecular tools to investigate the impact of algal turbidity on reproductive success and sexual selection on males in controlled laboratory experiments, allowing mate choice, mating competition, and mate encounter rates to affect reproduction. As study species, we used the broad-nosed pipefish, Syngnathus typhle , a species practicing male pregnancy and where we have previously shown that male mate choice is impaired by turbidity. Here, turbidity instead enhanced sexual selection on male size and mating success as well as reproductive success. Effects from mating competition and mate encounter rates may thus override effects from mate choice based on visual cues, producing an overall stronger sexual selection in turbid waters. Hence, seemingly inconsistent effects of turbidity on sexual selection may depend on which mechanisms of sexual selection that have been under study. Algal blooms are becoming increasingly more common due to eutrophication of freshwater and marine environments. The high density of algae lowers water transparency and reduces the possibility for fish and other aquatic animals to perform behaviors dependent on vision. We have previously shown that pipefish are unable to select the best partner in mate choice trials when water transparency was reduced. However, fish might use other senses than vision to compensate for the reduction in water transparency. In this study, we found that when fish were allowed to freely interact, thereby allowing competition between partners and direct contact between the fish, the best partner was indeed chosen. Hence, the negative effects of reduced water visibility due to algal blooms may be counteracted by the use of other senses in fish.

Is it useful to view the brain as a secondary sexual characteristic?

PubMed

Ball, Gregory F; Balthazart, Jacques; McCarthy, Margaret M

2014-10-01

Many sex differences in brain and behavior related to reproduction are thought to have evolved based on sexual selection involving direct competition for mates during male-male competition and female choice. Therefore, certain aspects of brain circuitry can be viewed as secondary sexual characteristics. The study of proximate causes reveals that sex differences in the brain of mammals and birds reflect organizational and activational effects of sex steroids as articulated by Young and collaborators. However, sex differences in brain and behavior have been identified in the cognitive domain with no obvious link to reproduction. Recent views of sexual selection advocate for a broader view of how intra-sexual selection might occur including such examples as competition within female populations for resources that facilitate access to mates rather than mating competition per se. Sex differences can also come about for other reasons than sexual selection and recent work on neuroendocrine mechanisms has identified a plethora of ways that the brain can develop in a sex specific manner. Identifying the brain as sexually selected requires careful hypothesis testing so that one can link a sex-biased aspect of a neural trait to a behavior that provides an advantage in a competitive mating situation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Correlated evolution of migration and sexual dichromatism in the New World orioles (icterus).

PubMed

Friedman, Nicholas R; Hofmann, Christopher M; Kondo, Beatrice; Omland, Kevin E

2009-12-01

The evolution of sexual dimorphism has long been attributed to sexual selection, specifically as it would drive repeated gains of elaborate male traits. In contrast to this pattern, New World oriole species all exhibit elaborate male plumage, and the repeated gains of sexual dichromatism observed in the genus are due to losses of female elaboration. Interestingly, most sexually dichromatic orioles belong to migratory or temperate-breeding clades. Using character scoring and ancestral state reconstructions from two recent studies in Icterus, we tested a hypothesis of correlated evolution between migration and sexual dichromatism. We employed two discrete phylogenetic comparative approaches: the concentrated changes test and Pagel's discrete likelihood test. Our results show that the evolution of these traits is significantly correlated (CCT: uncorrected P < 0.05; ML: LRT = 12.470, P < 0.005). Indeed, our best model of character evolution suggests that gains of sexual dichromatism are 23 times more likely to occur in migratory taxa. This study demonstrates that a life-history trait with no direct relationship with sexual selection has a strong influence on the evolution of sexual dichromatism. We recommend that researchers further investigate the role of selection on elaborate female traits in the evolution of sexual dimorphism.

Do Men and Women Report Their Sexual Partnerships Differently? Evidence from Kisumu, Kenya

PubMed Central

Clark, Shelley; Kabiru, Caroline; Zulu, Eliya

2012-01-01

CONTEXT It is generally believed that men and women misreport their sexual behaviors, which undermines the ability of researchers, program designers and health care providers to assess whether these behaviors compromise individuals’ sexual and reproductive health. METHODS Data on 1,299 recent sexual partnerships were collected in a 2007 survey of 1,275 men and women aged 18–24 and living in Kisumu, Kenya. Chi-square and t tests were used to examine how sample selection bias and selective partnership reporting may result in gender differences in reported sexual behaviors. Correlation coefficients and kappa statistics were calculated in further analysis of a sample of 280 matched marital and nonmarital couples to assess agreement on reported behaviors. RESULTS Even after adjustment for sample selection bias, men reported twice as many partnerships as women (0.5 vs. 0.2), as well as more casual partnerships. However, when selective reporting was controlled for, aggregate gender differences in sexual behaviors almost entirely disappeared. In the matched-couples sample, men and women exhibited moderate to substantial levels of agreement for most relationship characteristics and behaviors, including type of relationship, frequency of sex and condom use. Finally, men and women tended to agree about whether men had other nonmarital partners, but disagreed about women’s nonmarital partners. CONCLUSIONS Both sample selection bias and selective partnership reporting can influence the level of agreement between men’s and women’s reports of sexual behaviors. Although men report more casual partners than do women, accounts of sexual behavior within reported relationships are generally reliable. PMID:22227625

Migration and the evolution of sexual dichromatism: evolutionary loss of female coloration with migration among wood-warblers.

PubMed

Simpson, Richard K; Johnson, Michele A; Murphy, Troy G

2015-06-22

The mechanisms underlying evolutionary changes in sexual dimorphism have long been of interest to biologists. A striking gradient in sexual dichromatism exists among songbirds in North America, including the wood-warblers (Parulidae): males are generally more colourful than females at northern latitudes, while the sexes are similarly ornamented at lower latitudes. We use phylogenetically controlled comparative analysis to test three non-mutually exclusive hypotheses for the evolution of sexual dichromatism among wood-warblers. The first two hypotheses focus on the loss of female coloration with the evolution of migration, either owing to the costs imposed by visual predators during migration, or owing to the relaxation of selection for female social signalling at higher latitudes. The third hypothesis focuses on whether sexual dichromatism evolved owing to changes in male ornamentation as the strength of sexual selection increases with breeding latitude. To test these hypotheses, we compared sexual dichromatism to three variables: the presence of migration, migration distance, and breeding latitude. We found that the presence of migration and migration distance were both positively correlated with sexual dichromatism, but models including breeding latitude alone were not strongly supported. Ancestral state reconstruction supports the hypothesis that the ancestral wood-warblers were monochromatic, with both colourful males and females. Combined, these results are consistent with the hypotheses that the evolution of migration is associated with the relaxation of selection for social signalling among females and that there are increased predatory costs along longer migratory routes for colourful females. These results suggest that loss of female ornamentation can be a driver of sexual dichromatism and that social or natural selection may be a stronger contributor to variation in dichromatism than sexual selection. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Migration and the evolution of sexual dichromatism: evolutionary loss of female coloration with migration among wood-warblers

PubMed Central

Simpson, Richard K.; Johnson, Michele A.; Murphy, Troy G.

2015-01-01

The mechanisms underlying evolutionary changes in sexual dimorphism have long been of interest to biologists. A striking gradient in sexual dichromatism exists among songbirds in North America, including the wood-warblers (Parulidae): males are generally more colourful than females at northern latitudes, while the sexes are similarly ornamented at lower latitudes. We use phylogenetically controlled comparative analysis to test three non-mutually exclusive hypotheses for the evolution of sexual dichromatism among wood-warblers. The first two hypotheses focus on the loss of female coloration with the evolution of migration, either owing to the costs imposed by visual predators during migration, or owing to the relaxation of selection for female social signalling at higher latitudes. The third hypothesis focuses on whether sexual dichromatism evolved owing to changes in male ornamentation as the strength of sexual selection increases with breeding latitude. To test these hypotheses, we compared sexual dichromatism to three variables: the presence of migration, migration distance, and breeding latitude. We found that the presence of migration and migration distance were both positively correlated with sexual dichromatism, but models including breeding latitude alone were not strongly supported. Ancestral state reconstruction supports the hypothesis that the ancestral wood-warblers were monochromatic, with both colourful males and females. Combined, these results are consistent with the hypotheses that the evolution of migration is associated with the relaxation of selection for social signalling among females and that there are increased predatory costs along longer migratory routes for colourful females. These results suggest that loss of female ornamentation can be a driver of sexual dichromatism and that social or natural selection may be a stronger contributor to variation in dichromatism than sexual selection. PMID:26019159

Sex steroids, sexual behavior, and selection attention for erotic stimuli in women using oral contraceptives.

PubMed

Alexander, G M; Sherwin, B B

1993-01-01

The relationship between sex steroids and sexual behavior was examined in 19 oral contraceptive users. Retrospective assessment of sexual attitudes were obtained and women completed daily ratings of sexual behavior and well-being for 28 days. Plasma levels of free testosterone (T), estradiol, and progesterone were measured at weekly intervals. In addition, women performed a novel selective attention task designed to measure the strength of the tendency to be distracted by sexual stimuli. Multiple regression analyses using average sexual behavior variables as dependent variables, and hormone levels sexual attitudes and well-being as predictor variables, showed that free T was strongly and positively associated with sexual desire, sexual thoughts, and anticipation of sexual activity. A role for T in attention to sexual stimuli was also supported by the positive correlation between free T and the bias for sexual stimuli in a subgroup of women. These results are consistent with the hypothesis that T may enhance cognitive aspects of women's sexual behavior.

Sexual Harassment on Campus: A Legal Compendium.

ERIC Educational Resources Information Center

Van Tol, Joan E., Ed.

Law review and journal articles on sexual harassment in higher education are presented along with policies and procedures from selected universities and organizations, guidance on drafting policies, and a selected bibliography. The following law review and journal articles are presented: "Recent Legal Developments in Sexual Harassment"…

Teen Sexuality Today: Bibliography of Selected Resources.

ERIC Educational Resources Information Center

Planned Parenthood Federation of America, Inc., New York, NY.

This document presents a selected bibliography of recent books and journal articles relating to adolescent sexuality and reproductive health. The compilation of annotated references is divided into sections which focus on the issues of: (1) Sexuality Education; (2) Contraception; (3) Parenthood; (4) Communication with Parents; (5) Reproductive…

Natural and sexual selection giveth and taketh away reproductive barriers: models of population divergence in guppies.

PubMed

Labonne, Jacques; Hendry, Andrew P

2010-07-01

The standard predictions of ecological speciation might be nuanced by the interaction between natural and sexual selection. We investigated this hypothesis with an individual-based model tailored to the biology of guppies (Poecilia reticulata). We specifically modeled the situation where a high-predation population below a waterfall colonizes a low-predation population above a waterfall. Focusing on the evolution of male color, we confirm that divergent selection causes the appreciable evolution of male color within 20 generations. The rate and magnitude of this divergence were reduced when dispersal rates were high and when female choice did not differ between environments. Adaptive divergence was always coupled to the evolution of two reproductive barriers: viability selection against immigrants and hybrids. Different types of sexual selection, however, led to contrasting results for another potential reproductive barrier: mating success of immigrants. In some cases, the effects of natural and sexual selection offset each other, leading to no overall reproductive isolation despite strong adaptive divergence. Sexual selection acting through female choice can thus strongly modify the effects of divergent natural selection and thereby alter the standard predictions of ecological speciation. We also found that under no circumstances did divergent selection cause appreciable divergence in neutral genetic markers.

Socially transmitted mate preferences in a monogamous bird: a non-genetic mechanism of sexual selection.

PubMed

Swaddle, John P; Cathey, Mark G; Correll, Maureen; Hodkinson, Brendan P

2005-05-22

There is increasing evidence that animals can acquire mate preferences through the use of public information, notably by observing (and copying) the mate preferences of others in the population. If females acquire preferences through social mechanisms, sexual selection could act very rapidly to spread the preference and drive elaboration of the preferred trait(s). Although there are reports of 'mate-choice copying' in polygynous species, there is no clear evidence for this process in monogamous species. Here, we investigated whether adult female zebra finches Taeniopygia guttata can socially acquire sexual preferences for individual males and, in a separate study, for a generalized trait (coloured leg bands) of males. In both studies, test females observed males in two simultaneous conditions: a ('chosen') mixed-sex situation in which a male was paired with a (model) female, and a ('unchosen') same-sex situation in which a male was paired with another male. In the first experiment, after two weeks of females observing males, test females significantly preferred individual males who had been paired with another female (i.e. chosen males). In the second experiment, test females significantly preferred novel males that were wearing the same leg band colour as the apparently chosen males. Our findings are consistent with the conclusion that female zebra finches' mate preferences are altered by public information. Our study implies that mate preferences can spread rapidly through populations by social mechanisms, affecting the strength of sexual selection in a monogamous species.

Associations between dopamine D4 receptor gene variation with both infidelity and sexual promiscuity.

PubMed

Garcia, Justin R; MacKillop, James; Aller, Edward L; Merriwether, Ann M; Wilson, David Sloan; Lum, J Koji

2010-11-30

Human sexual behavior is highly variable both within and between populations. While sex-related characteristics and sexual behavior are central to evolutionary theory (sexual selection), little is known about the genetic bases of individual variation in sexual behavior. The variable number tandem repeats (VNTR) polymorphism in exon III of the human dopamine D4 receptor gene (DRD4) has been correlated with an array of behavioral phenotypes and may be predicatively responsible for variation in motivating some sexual behaviors, particularly promiscuity and infidelity. We administered an anonymous survey on personal history of sexual behavior and intimate relationships to 181 young adults. We also collected buccal wash samples and genotyped the DRD4 VNTR. Here we show that individuals with at least one 7-repeat allele (7R+) report a greater categorical rate of promiscuous sexual behavior (i.e., having ever had a "one-night stand") and report a more than 50% increase in instances of sexual infidelity. DRD4 VNTR genotype varies considerably within and among populations and has been subject to relatively recent, local selective pressures. Individual differences in sexual behavior are likely partially mediated by individual genetic variation in genes coding for motivation and reward in the brain. Conceptualizing these findings in terms of r/K selection theory suggests a mechanism for selective pressure for and against the 7R+ genotype that may explain the considerable global allelic variation for this polymorphism.

Associations between Dopamine D4 Receptor Gene Variation with Both Infidelity and Sexual Promiscuity

PubMed Central

Garcia, Justin R.; MacKillop, James; Aller, Edward L.; Merriwether, Ann M.; Wilson, David Sloan; Lum, J. Koji

2010-01-01

Background Human sexual behavior is highly variable both within and between populations. While sex-related characteristics and sexual behavior are central to evolutionary theory (sexual selection), little is known about the genetic bases of individual variation in sexual behavior. The variable number tandem repeats (VNTR) polymorphism in exon III of the human dopamine D4 receptor gene (DRD4) has been correlated with an array of behavioral phenotypes and may be predicatively responsible for variation in motivating some sexual behaviors, particularly promiscuity and infidelity. Methodology/Principal Findings We administered an anonymous survey on personal history of sexual behavior and intimate relationships to 181 young adults. We also collected buccal wash samples and genotyped the DRD4 VNTR. Here we show that individuals with at least one 7-repeat allele (7R+) report a greater categorical rate of promiscuous sexual behavior (i.e., having ever had a “one-night stand”) and report a more than 50% increase in instances of sexual infidelity. Conclusions/Significance DRD4 VNTR genotype varies considerably within and among populations and has been subject to relatively recent, local selective pressures. Individual differences in sexual behavior are likely partially mediated by individual genetic variation in genes coding for motivation and reward in the brain. Conceptualizing these findings in terms of r/K selection theory suggests a mechanism for selective pressure for and against the 7R+ genotype that may explain the considerable global allelic variation for this polymorphism. PMID:21152404

Sexual selection and the evolution of genital shape and complexity in water striders.

PubMed

Rowe, Locke; Arnqvist, Göran

2012-01-01

Animal genitalia show two striking but incompletely understood evolutionary trends: a great evolutionary divergence in the shape of genitalic structures, and characteristic structural complexity. Both features are thought to result from sexual selection, but explicit comparative tests are hampered by the fact that it is difficult to quantify both morphological complexity and divergence in shape. We undertake a comparative study of multiple nongenitalic and male genital traits in a clade of 15 water strider species to quantify complexity and shape divergence. We show that genital structures are more complex and their shape more divergent among species than nongenital traits. Further, intromittent genital traits are more complex and have evolved more divergently than nonintromittent genital traits. More importantly, shape and complexity of nonintromittent genital traits show correlated evolution with indices of premating sexual selection and intromittent genital traits with postmating sexual selection, suggesting that the evolution of different components of genital morphology are shaped independently by distinct forms of sexual selection. Our quantitative results provide direct comparative support for the hypothesis that sexual selection is associated with morphological complexity in genitalic traits and highlight the importance of quantifying morphological shape and complexity, rather than size in studies of genital evolution. © 2011 The Author(s). Evolution © 2011 The Society for the Study of Evolution.

How cuckoldry can decrease the opportunity for sexual selection: Data and theory from a genetic parentage analysis of the sand goby, Pomatoschistus minutus

PubMed Central

Jones, Adam G.; Walker, DeEtte; Kvarnemo, Charlotta; Lindström, Kai; Avise, John C.

2001-01-01

Alternative mating strategies are common in nature and are generally thought to increase the intensity of sexual selection. However, cuckoldry can theoretically decrease the opportunity for sexual selection, particularly in highly polygamous species. We address here the influence of sneaking (fertilization thievery) on the opportunity for sexual selection in the sand goby Pomatoschistus minutus, a marine fish species in which males build and defend nests. Our microsatellite-based analysis of the mating system in a natural sand goby population shows high rates of sneaking and multiple mating by males. Sneaker males had fertilized eggs in ≈50% of the assayed nests, and multiple sneakers sometimes fertilized eggs from a single female. Successful males had received eggs from 2 to 6 females per nest (mean = 3.4). We developed a simple mathematical model showing that sneaking in this polygynous sand goby population almost certainly decreases the opportunity for sexual selection, an outcome that contrasts with the usual effects of cuckoldry in socially monogamous animals. These results highlight a more complex and interesting relationship between cuckoldry rates and the intensity of sexual selection than previously assumed in much of the literature on animal mating systems. PMID:11481481

Sexual selection predicts advancement of avian spring migration in response to climate change.

PubMed

Spottiswoode, Claire N; Tøttrup, Anders P; Coppack, Timothy

2006-12-22

Global warming has led to earlier spring arrival of migratory birds, but the extent of this advancement varies greatly among species, and it remains uncertain to what degree these changes are phenotypically plastic responses or microevolutionary adaptations to changing environmental conditions. We suggest that sexual selection could help to understand this variation, since early spring arrival of males is favoured by female choice. Climate change could weaken the strength of natural selection opposing sexual selection for early migration, which would predict greatest advancement in species with stronger female choice. We test this hypothesis comparatively by investigating the degree of long-term change in spring passage at two ringing stations in northern Europe in relation to a synthetic estimate of the strength of female choice, composed of degree of extra-pair paternity, relative testes size and degree of sexually dichromatic plumage colouration. We found that species with a stronger index of sexual selection have indeed advanced their date of spring passage to a greater extent. This relationship was stronger for the changes in the median passage date of the whole population than for changes in the timing of first-arriving individuals, suggesting that selection has not only acted on protandrous males. These results suggest that sexual selection may have an impact on the responses of organisms to climate change, and knowledge of a species' mating system might help to inform attempts at predicting these.

Overcoming statistical bias to estimate genetic mating systems in open populations: a comparison of Bateman's principles between the sexes in a sex-role-reversed pipefish.

PubMed

Mobley, Kenyon B; Jones, Adam G

2013-03-01

The genetic mating system is a key component of the sexual selection process, yet methods for the quantification of mating systems remain controversial. One approach involves metrics derived from Bateman's principles, which are based on variances in mating and reproductive success and the relationship between them. However, these measures are extremely difficult to measure for both sexes in open populations, because missing data can result in biased estimates. Here, we develop a novel approach for the estimation of mating system metrics based on Bateman's principles and apply it to a microsatellite-based parentage analysis of a natural population of the dusky pipefish, Syngnathus floridae. Our results show that both male and female dusky pipefish have significantly positive Bateman gradients. However, females exhibit larger values of the opportunity for sexual selection and the opportunity for selection compared to males. These differences translate into a maximum intensity of sexual selection (S'max) for females three times larger than that for males. Overall, this study identifies a critical source of bias that affects studies of mating systems in open populations, presents a novel method for overcoming this bias, and applies this method for the first time in a sex-role-reversed pipefish. © 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.

Selective Serotonin Reuptake Inhibitor-Induced Sexual Dysfunction in Adolescents: A Review.

ERIC Educational Resources Information Center

Scharko, Alexander M.

2004-01-01

Objective: To review the existing literature on selective serotonin reuptake inhibitor (SSRI)-induced sexual dysfunction in adolescents. Method: A literature review of SSRI-induced adverse effects in adolescents focusing on sexual dysfunction was done. Nonsexual SSRI-induced adverse effects were compared in adult and pediatric populations.…

Sexual Selection of Protamine 1 in Mammals.

PubMed

Lüke, Lena; Tourmente, Maximiliano; Roldan, Eduardo R S

2016-01-01

Protamines have a crucial role in male fertility. They are involved in sperm chromatin packaging and influence the shape of the sperm head and, hence, are important for sperm performance. Protamine structure is basic with numerous arginine-rich DNA-binding domains. Postcopulatory sexual selection is thought to play an important role in protamine sequence evolution and expression. Here, we analyze patterns of evolution and sexual selection (in the form of sperm competition) acting on protamine 1 gene sequence in 237 mammalian species. We assessed common patterns as well as differences between the major mammalian subclasses (Eutheria, Metatheria) and clades. We found that a high arginine content in protamine 1 associates with a lower sperm head width, which may have an impact on sperm swimming velocity. Increase in arginine content in protamine 1 across mammals appears to take place in a way consistent with sexual selection. In metatherians, increase in sequence length correlates with sexual selection. Differences in selective pressures on sequences and codon sites were observed between mammalian clades. Our study revealed a complex evolutionary pattern of protamine 1, with different selective constraints, and effects of sexual selection, between mammalian groups. In contrast, the effect of arginine content on head shape, and the possible involvement of sperm competition, was identified across all mammals. © The Author 2015. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Sexual selection on receptor organ traits: younger females attract males with longer antennae

NASA Astrophysics Data System (ADS)

Johnson, Tamara L.; Symonds, Matthew R. E.; Elgar, Mark A.

2017-06-01

Sexual selection theory predicts that female choice may favour the evolution of elaborate male signals. Darwin also suggested that sexual selection can favour elaborate receiver structures in order to better detect sexual signals, an idea that has been largely ignored. We evaluated this unorthodox perspective by documenting the antennal lengths of male Uraba lugens Walker (Lepidoptera: Nolidae) moths that were attracted to experimentally manipulated emissions of female sex pheromone. Either one or two females were placed in field traps for the duration of their adult lives in order to create differences in the quantity of pheromone emissions from the traps. The mean antennal length of males attracted to field traps baited with a single female was longer than that of males attracted to traps baited with two females, a pattern consistent with Darwin's prediction assuming the latter emits higher pheromone concentrations. Furthermore, younger females attracted males with longer antennae, which may reflect age-specific changes in pheromone emission. These field experiments provide the first direct evidence of an unappreciated role for sexual selection in the evolution of sexual dimorphism in moth antennae and raise the intriguing possibility that females select males with longer antennae through strategic emission of pheromones.

Positive allometry and the prehistory of sexual selection.

PubMed

Tomkins, Joseph L; LeBas, Natasha R; Witton, Mark P; Martill, David M; Humphries, Stuart

2010-08-01

The function of the exaggerated structures that adorn many fossil vertebrates remains largely unresolved. One recurrent hypothesis is that these elaborated traits had a role in thermoregulation. This orthodoxy persists despite the observation that traits exaggerated to the point of impracticality in extant organisms are almost invariably sexually selected. We use allometric scaling to investigate the role of sexual selection and thermoregulation in the evolution of exaggerated traits of the crested pterosaur Pteranodon longiceps and the sail-backed eupelycosaurs Dimetrodon and Edaphosaurus. The extraordinarily steep positive allometry of the head crest of Pteranodon rules out all of the current hypotheses for this trait's main function other than sexual signaling. We also find interspecific patterns of allometry and sexual dimorphism in the sails of Dimetrodon and patterns of elaboration in Edaphosaurus consistent with a sexually selected function. Furthermore, small ancestral, sail-backed pelycosaurs would have been too small to need adaptations to thermoregulation. Our results question the popular view that the elaborated structures of these fossil species evolved as thermoregulatory organs and provide evidence in support of the hypothesis that Pteranodon crests and eupelycosaur sails are among the earliest and most extreme examples of elaborate sexual signals in the evolution of terrestrial vertebrates.

Sexual homicides in South Africa: A national cross-sectional epidemiological study of adult women and children.

PubMed

Abrahams, Naeemah; Mathews, Shanaaz; Lombard, Carl; Martin, Lorna J; Jewkes, Rachel

2017-01-01

We conducted a retrospective national mortuary based study to identify all adult female homicides (18 years and older) and all child homicides (boys and girls < 18 years) in 2009 in a randomly selected, proportionate sample of mortuaries. Victim, perpetrator and crime data were collected in three processes: from the mortuary register, the autopsy report and from police with the identification of sexual homicides validated across the data collection processes. Among the 2670 (95% CI: 2311-2979) adult women killed in 2009, 494 (95% CI: 406-574) were identified as sexual homicides which was 19.8% (95% CI: 17.6-22.0) of all adult female homicides and among 1277 (95% CI: 1091-1462) children killed in SA, sexual homicides were found in 104 (95% CI: 77-132) of the child homicides which was 8.7% (95% CI: 10.9-11.2%) of these murders. Strangulation was the most common cause of death for both children and adult females. A distinct age and sex pattern was found among children with only 1% boy child death identified as a sexual homicide and 92% of all the child sexual homicides were among girls. Strangulation was the most common manner of death among children (35.5%) and perpetrators were seldom strangers. However, no difference in the proportion of convictions between the sexual homicides and non-sexual homicides were found for both adult females and children. Rape homicide is not a rare event in South Africa, with one in five female homicides and nearly one in ten child homicides identified with an associated sexual crime. These high prevalences are amongst the highest levels reported in the literature with our study among the few reporting on the epidemiology of child sexual homicide. Reducing mortality is an important policy goal for South Africa and for the rest of the world and the prevention of female and child homicide is an important part of attaining this goal.

Sexual practices in Malaysia: determinants of sexual intercourse among unmarried youths.

PubMed

Zulkifli, S N; Low, W Y

2000-10-01

This paper describes findings on selected determinants of sexual intercourse among 468 unmarried adolescents from a survey in Malaysia. Data on respondents' background, sexual experience, contraceptive use, and sexual attitudes are provided. Based on multiple logistic regressions, factors significantly predictive of sexual experience are gender, employment, and sexual attitudes.

Sexual selection and genetic colour polymorphisms in animals.

PubMed

Wellenreuther, Maren; Svensson, Erik I; Hansson, Bengt

2014-11-01

Genetic colour polymorphisms are widespread across animals and often subjected to complex selection regimes. Traditionally, colour morphs were used as simple visual markers to measure allele frequency changes in nature, selection, population divergence and speciation. With advances in sequencing technology and analysis methods, several model systems are emerging where the molecular targets of selection are being described. Here, we discuss recent studies on the genetics of sexually selected colour polymorphisms, aiming at (i) reviewing the evidence of sexual selection on colour polymorphisms, (ii) highlighting the genetic architecture, molecular and developmental basis underlying phenotypic colour diversification and (iii) discuss how the maintenance of such polymorphisms might be facilitated or constrained by these. Studies of the genetic architecture of colour polymorphism point towards the importance of tight clustering of colour loci with other trait loci, such as in the case of inversions and supergene structures. Other interesting findings include linkage between colour loci and mate preferences or sex determination, and the role of introgression and regulatory variation in fuelling polymorphisms. We highlight that more studies are needed that explicitly integrate fitness consequences of sexual selection on colour with the underlying molecular targets of colour to gain insights into the evolutionary consequences of sexual selection on polymorphism maintenance. © 2014 John Wiley & Sons Ltd.

Balancing Selection in Species with Separate Sexes: Insights from Fisher’s Geometric Model

PubMed Central

Connallon, Tim; Clark, Andrew G.

2014-01-01

How common is balancing selection, and what fraction of phenotypic variance is attributable to balanced polymorphisms? Despite decades of research, answers to these questions remain elusive. Moreover, there is no clear theoretical prediction about the frequency with which balancing selection is expected to arise within a population. Here, we use an extension of Fisher’s geometric model of adaptation to predict the probability of balancing selection in a population with separate sexes, wherein polymorphism is potentially maintained by two forms of balancing selection: (1) heterozygote advantage, where heterozygous individuals at a locus have higher fitness than homozygous individuals, and (2) sexually antagonistic selection (a.k.a. intralocus sexual conflict), where the fitness of each sex is maximized by different genotypes at a locus. We show that balancing selection is common under biologically plausible conditions and that sex differences in selection or sex-by-genotype effects of mutations can each increase opportunities for balancing selection. Although heterozygote advantage and sexual antagonism represent alternative mechanisms for maintaining polymorphism, they mutually exist along a balancing selection continuum that depends on population and sex-specific parameters of selection and mutation. Sexual antagonism is the dominant mode of balancing selection across most of this continuum. PMID:24812306

What Is New with Sexual Side Effects After Transurethral Male Lower Urinary Tract Symptom Surgery?

PubMed

Rieken, Malte; Antunes-Lopes, Tiago; Geavlete, Bogdan; Marcelissen, Tom

2018-01-01

Transurethral resection of the prostate as well as laser prostatectomy (by either holmium laser enucleation of the prostate or Greenlight laser vaporization) is associated with risks of sexual dysfunction such as antegrade ejaculation and occasionally erectile dysfunction. While ejaculation-sparing variations of these techniques show promising results, larger multicenter studies are needed to confirm promising data. Prostatic urethral lift maintains erectile and ejaculatory function at 5-yr follow-up. The same is true for the 3-yr data on the Rezum system. Recently, Aquablation has shown promising results; however, these 6-mo data need to be confirmed during longer follow-up. An individualized, shared decision-making process based on clinical parameters and patient preference is warranted to select the ideal treatment option for each patient. Sexual dysfunction such as loss of ejaculation and, less frequently, erectile dysfunction can occur after transurethral prostate surgery. Ejaculation-sparing modifications as well as minimally invasive alternatives show promising results. An individualized approach is warranted to select the ideal technique for each patient. Copyright © 2018 European Association of Urology. Published by Elsevier B.V. All rights reserved.

Can sexual selection theory inform genetic management of captive populations? A review

PubMed Central

Chargé, Rémi; Teplitsky, Céline; Sorci, Gabriele; Low, Matthew

2014-01-01

Captive breeding for conservation purposes presents a serious practical challenge because several conflicting genetic processes (i.e., inbreeding depression, random genetic drift and genetic adaptation to captivity) need to be managed in concert to maximize captive population persistence and reintroduction success probability. Because current genetic management is often only partly successful in achieving these goals, it has been suggested that management insights may be found in sexual selection theory (in particular, female mate choice). We review the theoretical and empirical literature and consider how female mate choice might influence captive breeding in the context of current genetic guidelines for different sexual selection theories (i.e., direct benefits, good genes, compatible genes, sexy sons). We show that while mate choice shows promise as a tool in captive breeding under certain conditions, for most species, there is currently too little theoretical and empirical evidence to provide any clear guidelines that would guarantee positive fitness outcomes and avoid conflicts with other genetic goals. The application of female mate choice to captive breeding is in its infancy and requires a goal-oriented framework based on the needs of captive species management, so researchers can make honest assessments of the costs and benefits of such an approach, using simulations, model species and captive animal data. PMID:25553072

Population genomics of early events in the ecological differentiation of bacteria

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shapiro, Jesse B.; Friedman, Jonatan; Cordero, Otto X.

Genetic exchange is common among bacteria, but its effect on population diversity during ecological differentiation remains controversial. A fundamental question is whether advantageous mutations lead to selection of clonal genomes or, as in sexual eukaryotes, sweep through populations on their own. Here, we show that in two recently diverged populations of ocean bacteria, ecological differentiation has occurred akin to a sexual mechanism: A few genome regions have swept through subpopulations in a habitat-specific manner, accompanied by gradual separation of gene pools as evidenced by increased habitat specificity of the most recent recombinations. These findings reconcile previous, seemingly contradictory empirical observationsmore » of the genetic structure of bacterial populations and point to a more unified process of differentiation in bacteria and sexual eukaryotes than previously thought.« less

Sexual selection on cuticular hydrocarbons in the Australian field cricket, Teleogryllus oceanicus

PubMed Central

Thomas, Melissa L; Simmons, Leigh W

2009-01-01

Background Females in a wide range of taxa have been shown to base their choice of mates on pheromone signals. However, little research has focussed specifically on the form and intensity of selection that mate choice imposes on the pheromone signal. Using multivariate selection analysis, we characterise directly the form and intensity of sexual selection acting on cuticular hydrocarbons, chemical compounds widely used in the selection of mates in insects. Using the Australian field cricket Teleogryllus oceanicus as a model organism, we use three measures of male attractiveness to estimate fitness; mating success, the duration of courtship required to elicit copulation, and subsequent spermatophore attachment duration. Results We found that all three measures of male attractiveness generated sexual selection on male cuticular hydrocarbons, however there were differences in the form and intensity of selection among these three measures. Mating success was the only measure of attractiveness that imposed both univariate linear and quadratic selection on cuticular hydrocarbons. Although we found that all three attractiveness measures generated nonlinear selection, again only mating success was found to exert statistically significant stabilizing selection. Conclusion This study shows that sexual selection plays an important role in the evolution of male cuticular hydrocarbon signals. PMID:19594896

Sexual selection and maintenance of sex: evidence from comparisons of rates of genomic accumulation of mutations and divergence of sex-related genes in sexual and hermaphroditic species of Caenorhabditis.

PubMed

Artieri, Carlo G; Haerty, Wilfried; Gupta, Bhagwati P; Singh, Rama S

2008-05-01

Several hypotheses have been proposed to explain the persistence of dioecy despite the reproductive advantages conferred to hermaphrodites, including greater efficiency at purging deleterious mutations in the former. Dioecy can benefit from both mutation purging and accelerated evolution by bringing together beneficial mutations in the same individual via recombination and shuffling of genotypes. In addition, mathematical treatment has shown that sexual selection is also capable of mitigating the cost of maintaining separate sexes by increasing the overall fitness of sexual populations, and genomic comparisons have shown that sexual selection can lead to accelerated evolution. Here, we examine the advantages of dioecy versus hermaphroditism by comparing the rate of evolution in sex-related genes and the rate of accumulation of deleterious mutations using a large number of orthologs (11,493) in the dioecious Caenorhabditis remanei and the hermaphroditic Caenorhabditis briggsae. We have used this data set to estimate the deleterious mutation rate per generation, U, in both species and find that although it is significantly higher in hermaphrodites, both species are at least 2 orders of magnitude lower than the value required to explain the persistence of sex by efficiency at purging deleterious mutations alone. We also find that genes expressed in sperm are evolving rapidly in both species; however, they show a greater increase in their rate of evolution relative to genes expressed in other tissues in C. remanei, suggesting stronger sexual selection pressure acting on these genes in dioecious species. Interestingly, the persistence of a signal of rapid evolution of sperm genes in C. briggsae suggests a recent evolutionary origin of hermaphrodism in this lineage. Our results provide empirical evidence of increased sexual selection pressure in dioecious animals, supporting the possibility that sexual selection may play an important role in the maintenance of sexual reproduction.

The form of sexual selection arising from male-male competition depends on the presence of females in the social environment.

PubMed

Procter, D S; Moore, A J; Miller, C W

2012-05-01

Sexual selection arises from social interactions, and if social environments vary so too should sexual selection. For example, male-male competition often occurs either in the presence or in the absence of females, and such changes in the social environment could affect the form and strength of sexual selection. Here we examine how the presence of a female influences selection arising from male-male competition in a leaf-footed cactus bug, Narnia femorata, which has a resource defence mating system. Males compete for territories on cacti because females lay eggs on the cactus plants. Females are not always present when this competition first occurs; however, the presence or absence of the female matters. We found that both the form and strength of selection on male traits, those traits that influenced success in intrasexual competition, depended on the social context. When a female was not present, male size and the area of the sexually dimorphic hind legs was only marginally important to winning a contest. However, males with larger overall size and leg area were more likely to win in the presence of a female. There was also positive quadratic selection on these traits when a female was present with both the largest and the smallest males winning. The implication is unexpected alternative strategies when females are present. Our results support the notion that sexual selection should be studied under all relevant social contexts. © 2012 The Authors. Journal of Evolutionary Biology © 2012 European Society For Evolutionary Biology.

Sympatric speciation by sexual selection alone is unlikely.

PubMed

Arnegard, Matthew E; Kondrashov, Alexey S

2004-02-01

According to Darwin, sympatric speciation is driven by disruptive, frequency-dependent natural selection caused by competition for diverse resources. Recently, several authors have argued that disruptive sexual selection can also cause sympatric speciation. Here, we use hypergeometric phenotypic and individual-based genotypic models to explore sympatric speciation by sexual selection under a broad range of conditions. If variabilities of preference and display traits are each caused by more than one or two polymorphic loci, sympatric speciation requires rather strong sexual selection when females exert preferences for extreme male phenotypes. Under this kind of mate choice, speciation can occur only if initial distributions of preference and display are close to symmetric. Otherwise, the population rapidly loses variability. Thus, unless allele replacements at very few loci are enough for reproductive isolation, female preferences for extreme male displays are unlikely to drive sympatric speciation. By contrast, similarity-based female preferences that do not cause sexual selection are less destabilizing to the maintenance of genetic variability and may result in sympatric speciation across a broader range of initial conditions. Certain groups of African cichlids have served as the exclusive motivation for the hypothesis of sympatric speciation by sexual selection. Mate choice in these fishes appears to be driven by female preferences for extreme male phenotypes rather than similarity-based preferences, and the evolution of premating reproductive isolation commonly involves at least several genes. Therefore, differences in female preferences and male display in cichlids and other species of sympatric origin are more likely to have evolved as isolating mechanisms under disruptive natural selection.

Changes in sexual signals are greater than changes in ecological traits in a dichromatic group of fishes.

PubMed

Martin, Michael D; Mendelson, Tamra C

2014-12-01

Understanding the mechanisms by which phenotypic divergence occurs is central to speciation research. These mechanisms can be revealed by measuring differences in traits that are subject to different selection pressures; greater influence of different types of selection can be inferred from greater divergence in associated traits. Here, we address the potential roles of natural and sexual selection in promoting phenotypic divergence between species of snubnose darters by comparing differences in body shape, an ecologically relevant trait, and male color, a sexual signal. Body shape was measured using geometric morphometrics, and male color was measured using digital photography and visual system-dependent color values. Differences in male color are larger than differences in body shape across eight allopatric, phylogenetically independent species pairs. While this does not exclude the action of divergent natural selection, our results suggest a relatively more important role for sexual selection in promoting recent divergence in darters. Variation in the relative differences between male color and body shape across species pairs reflects the continuous nature of speciation mechanisms, ranging from ecological speciation to speciation by sexual selection alone. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

Sexual Selection Halts the Relaxation of Protamine 2 among Rodents

PubMed Central

Lüke, Lena; Vicens, Alberto; Serra, Francois; Luque-Larena, Juan Jose; Dopazo, Hernán; Roldan, Eduardo R. S.; Gomendio, Montserrat

2011-01-01

Sexual selection has been proposed as the driving force promoting the rapid evolutionary changes observed in some reproductive genes including protamines. We test this hypothesis in a group of rodents which show marked differences in the intensity of sexual selection. Levels of sperm competition were not associated with the evolutionary rates of protamine 1 but, contrary to expectations, were negatively related to the evolutionary rate of cleaved- and mature-protamine 2. Since both domains were found to be under relaxation, our findings reveal an unforeseen role of sexual selection: to halt the degree of degeneration that proteins within families may experience due to functional redundancy. The degree of relaxation of protamine 2 in this group of rodents is such that in some species it has become dysfunctional and it is not expressed in mature spermatozoa. In contrast, protamine 1 is functionally conserved but shows directed positive selection on specific sites which are functionally relevant such as DNA-anchoring domains and phosphorylation sites. We conclude that in rodents protamine 2 is under relaxation and that sexual selection removes deleterious mutations among species with high levels of sperm competition to maintain the protein functional and the spermatozoa competitive. PMID:22216223

Diploidy and the selective advantage for sexual reproduction in unicellular organisms.

PubMed

Kleiman, Maya; Tannenbaum, Emmanuel

2009-11-01

This article develops mathematical models describing the evolutionary dynamics of both asexually and sexually reproducing populations of diploid unicellular organisms. The asexual and sexual life cycles are based on the asexual and sexual life cycles in Saccharomyces cerevisiae, Baker's yeast, which normally reproduces by asexual budding, but switches to sexual reproduction when stressed. The mathematical models consider three reproduction pathways: (1) Asexual reproduction, (2) self-fertilization, and (3) sexual reproduction. We also consider two forms of genome organization. In the first case, we assume that the genome consists of two multi-gene chromosomes, whereas in the second case, we consider the opposite extreme and assume that each gene defines a separate chromosome, which we call the multi-chromosome genome. These two cases are considered to explore the role that recombination has on the mutation-selection balance and the selective advantage of the various reproduction strategies. We assume that the purpose of diploidy is to provide redundancy, so that damage to a gene may be repaired using the other, presumably undamaged copy (a process known as homologous recombination repair). As a result, we assume that the fitness of the organism only depends on the number of homologous gene pairs that contain at least one functional copy of a given gene. If the organism has at least one functional copy of every gene in the genome, we assume a fitness of 1. In general, if the organism has l homologous pairs that lack a functional copy of the given gene, then the fitness of the organism is kappa(l). The kappa(l) are assumed to be monotonically decreasing, so that kappa(0) = 1 > kappa(1) > kappa(2) > cdots, three dots, centered > kappa(infinity) = 0. For nearly all of the reproduction strategies we consider, we find, in the limit of large N, that the mean fitness at mutation-selection balance is max{2e(-mu) - 1,0} where N is the number of genes in the haploid set of the genome, epsilon is the probability that a given DNA template strand of a given gene produces a mutated daughter during replication, and mu = Nepsilon. The only exception is the sexual reproduction pathway for the multi-chromosomed genome. Assuming a multiplicative fitness landscape where kappa(l) = alpha(l) for alpha in (0, 1), this strategy is found to have a mean fitness that exceeds the mean fitness of all the other strategies. Furthermore, while other reproduction strategies experience a total loss of viability due to the steady accumulation of deleterious mutations once mu exceeds [Formula: see text] no such transition occurs in the sexual pathway. Indeed, in the limit as alpha --> 1 for the multiplicative landscape, we can show that the mean fitness for the sexual pathway with the multi-chromosomed genome converges to e(-2mu), which is always positive. We explicitly allow for mitotic recombination in this study, which, in contrast to previous studies using different models, does not have any advantage over other asexual reproduction strategies. The results of this article provide a basis for understanding the selective advantage of the specific meiotic pathway that is employed by sexually reproducing organisms. The results of this article also suggest an explanation for why unicellular organisms such as Saccharomyces cerevisiae (Baker's yeast) switch to a sexual mode of reproduction when stressed. While the results of this article are based on modeling mutation-propagation in unicellular organisms, they nevertheless suggest that, in more complex organisms with significantly larger genomes, sex is necessary to prevent the loss of viability of a population due to genetic drift. Finally, and perhaps most importantly, the results of this article demonstrate a selective advantage for sexual reproduction with fewer and much less restrictive assumptions than those of previous studies.

Patient and partner perspectives on patient-delivered partner screening: acceptability, benefits, and barriers.

PubMed

McBride, Kimberly R; Goldsworthy, Richard C; Fortenberry, J Dennis

2010-10-01

The study examined willingness to engage in patient-delivered partner screening (PDPS) and preferences for expedited partner services (EPS). Forty urban U.S. sexually transmitted infection (STI) clinic patients participated in individual mixed-methods interviews exploring EPS preferences and PDPS willingness. Most participants selected PDPS and PDPT together and uptake varied by patient–partner relationship closeness. For PDPS, several potentially important barriers and benefits were identified. Perceived benefits included improved sexual health for patients and their sexual partner(s) as well as convenience, privacy, and the potential to enhance trust between sexual partners. Perceived barriers included concerns about PDPS processes (e.g., time it would take to receive the result, risk of sample contamination), the accuracy of results, STI stigma and associated blame, lack of trust for a sexual partner, and the packaging/appearance of the screening kit. PDPS affords benefits and may overcome treatment barriers in some situations; however, it shares common PDPT barriers and has its own unique challenges. There are also concerns regarding how the offer of PDPS may interact with PDPT utilization.

Evolution of dosage compensation under sexual selection differs between X and Z chromosomes

PubMed Central

Mullon, Charles; Wright, Alison E.; Reuter, Max; Pomiankowski, Andrew; Mank, Judith E.

2015-01-01

Complete sex chromosome dosage compensation has more often been observed in XY than ZW species. In this study, using a population genetic model and the chicken transcriptome, we assess whether sexual conflict can account for this difference. Sexual conflict over expression is inevitable when mutation effects are correlated across the sexes, as compensatory mutations in the heterogametic sex lead to hyperexpression in the homogametic sex. Coupled with stronger selection and greater reproductive variance in males, this results in slower and less complete evolution of Z compared with X dosage compensation. Using expression variance as a measure of selection strength, we find that, as predicted by the model, dosage compensation in the chicken is most pronounced in genes that are under strong selection biased towards females. Our study explains the pattern of weak dosage compensation in ZW systems, and suggests that sexual selection plays a major role in shaping sex chromosome dosage compensation. PMID:26212613

Why Sexually Selected Weapons Are Not Ornaments.

PubMed

McCullough, Erin L; Miller, Christine W; Emlen, Douglas J

2016-10-01

The elaboration and diversification of sexually selected weapons remain poorly understood. We argue that progress in this topic has been hindered by a strong bias in sexual selection research, and a tendency for weapons to be conflated with ornaments used in mate choice. Here, we outline how male-male competition and female choice are distinct mechanisms of sexual selection, and why weapons and ornaments are fundamentally different types of traits. We call for research on the factors contributing to weapon divergence, the potential for male-male competition to drive speciation, and the specific use of weapons in the context of direct fights versus displays. Given that weapons are first and foremost fighting structures, biomechanical approaches are an especially promising direction for understanding weapon design. Copyright © 2016 Elsevier Ltd. All rights reserved.

Phylogeny of the beaked whale genus Mesoplodon (Ziphiidae: Cetacea) revealed by nuclear introns: implications for the evolution of male tusks.

PubMed

Dalebout, Merel L; Steel, Debbie; Baker, C Scott

2008-12-01

With 14 species currently recognized, the beaked whale genus Mesoplodon (family Ziphiidae) is the most speciose in the order Cetacea. Beaked whales are widely distributed but are rarely seen at sea due to their oceanic distribution, deep-diving capacity, and apparent low abundance. Morphological differentiation among Mesoplodon species is relatively limited, with the exception of tooth form in adult males. Based on scarring patterns, males appear to use their tusk-like teeth as weapons in aggressive encounters with other males. Females are effectively toothless. We used sequences from seven nuclear introns (3348 base pairs) to construct a robust and highly resolved phylogeny, which was then used as a framework to test predictions from four hypotheses seeking to explain patterns of Mesoplodon tusk morphology and/or the processes that have driven the diversification of this genus: (1) linear progression of tusk form; (2) allopatric speciation through isolation in adjacent deep-sea canyons; (3) sympatric speciation through sexual selection on tusks; and (4) selection for species-recognition cues. Maximum-likelihood and Bayesian reconstructions confirmed the monophyly of the genus and revealed that what were considered ancestral and derived tusk forms have in fact arisen independently on several occasions, contrary to predictions from the linear-progression hypothesis. Further, none of the three well-supported species clades was confined to a single ocean basin, as might have been expected from the deep-sea canyon-isolation or sexual-selection hypotheses, and some species with similar tusks have overlapping distributions, contrary to predictions from the species-recognition hypothesis. However, the divergent tusk forms and sympatric distributions of three of the four sister-species pairs identified suggest that sexual selection on male tusks has likely played an important role in this unique radiation, although other forces are clearly also involved. To our knowledge, this is the first time that sexual selection has been explicitly implicated in the radiation of a mammalian group outside terrestrial ungulates.

Bold Colors in a Cryptic Lineage: Do Eastern Indigo Snakes Exhibit Color Dimorphism?

PubMed Central

Deitloff, Jennifer; Johnson, Valerie M.; Guyer, Craig

2013-01-01

Many species exhibit variation in the color of their scales, feathers, or fur. Various forms of natural selection, such as mimicry, crypsis, and species recognition, as well as sexual selection, can influence the evolution of color. Eastern Indigo Snakes (Drymarchon couperi), a federally threatened species, have coloration on the sides of the head and the chin that can vary from black to red or cream. Despite significant conservations efforts for this species, little is known about its biology in the field. Past researchers have proposed that the color variation on the head and chin is associated with the sex of the individual. Alternatively, color might vary among individuals because it is controlled by genes that are under natural selection or neutral evolution. We tested these alternative hypotheses by examining whether coloration of the sublabial, submaxillary, and ventral scales of this species differed by sex or among clutches. We used color spectrometry to characterize important aspects of color in two ways: by examining overall color differences across the entire color spectrum and by comparing differences within the ultraviolet, yellow, and red colorbands. We found that Eastern Indigo Snakes do not exhibit sexual dichromatism, but their coloration does vary among clutches; therefore, the pattern of sexual selection leading to sexual dichromatism observed in many squamates does not appear to play a role in the evolution and maintenance of color variation in Eastern Indigo Snakes. We suggest that future studies should focus on determining whether color variation in these snakes is determined by maternal effects or genetic components and if color is influenced by natural selection or neutral evolutionary processes. Studying species that exhibit bright colors within lineages that are not known for such coloration will contribute greatly to our understanding of the evolutionary and ecological factors that drive these differences. PMID:23691245

The brown anole dewlap revisited: do predation pressure, sexual selection, and species recognition shape among-population signal diversity?

PubMed Central

Van Damme, Raoul

2018-01-01

Animal signalling structures are amongst the most variable characteristics, as they are subjected to a diversity of selection pressures. A well-known example of a diverse signalling system in the animal kingdom is the dewlap of Anolis lizards. Dewlap characteristics can vary remarkably among and within species, and also between sexes. Although a considerable amount of studies have attempted to disentangle the functional significance of the staggering dewlap diversity in Anolis, the underlying evolutionary processes remain elusive. In this study, we focus on the contribution of biotic selective pressures in shaping geographic variation in dewlap design (size, colour, and pattern) and dewlap display behaviour at the intraspecific level. Notably, we have tried to replicate and extend previously reported results hereof in both sexes of the brown anole lizard (Anolis sagrei). To do this, we assembled a dataset consisting of 17 A. sagrei heterogeneous island populations from the Caribbean and specifically tested whether predation pressure, sexual selection, or species recognition could explain interpopulational variation in an array of dewlap characteristics. Our findings show that in neither males nor females estimates of predation pressure (island size, tail break frequency, model attack rate, presence of predatory Leiocephalus lizards) or sexual selection (sexual size dimorphism) could explain variation in dewlap design. We did find that A. sagrei males from larger islands showed higher dewlap display intensities than males from smaller islands, but the direct connection with predation pressure remains ambiguous and demands further investigation. Last, we could show indirect support for species recognition only in males, as they are more likely to have a ‘spotted’ dewlap pattern when co-occurring with a higher number of syntopic Anolis species. In conclusion, we found overall limited support for the idea that the extensive interpopulational variability in dewlap design and use in A. sagrei is mediated by variation in their biotic environment. We propose a variety of conceptual and methodological explanations for this unexpected finding. PMID:29761044

Stabilizing selection on sperm number revealed by artificial selection and experimental evolution.

PubMed

Cattelan, Silvia; Di Nisio, Andrea; Pilastro, Andrea

2018-03-01

Sperm competition is taxonomically widespread in animals and is usually associated with large sperm production, being the number of sperm in the competing pool the prime predictor of fertilization success. Despite the strong postcopulatory selection acting directionally on sperm production, its genetic variance is often very high. This can be explained by trade-offs between sperm production and traits associated with mate acquisition or survival, that may contribute to generate an overall stabilizing selection. To investigate this hypothesis, we first artificially selected male guppies (Poecilia reticulata) for high and low sperm production for three generations, while simultaneously removing sexual selection. Then, we interrupted artificial selection and restored sexual selection. Sperm production responded to divergent selection in one generation, and when we restored sexual selection, both high and low lines converged back to the mean sperm production of the original population within two generations, indicating that sperm number is subject to strong stabilizing total sexual selection (i.e., selection acting simultaneously on all traits associated with reproductive success). We discuss the possible mechanisms responsible for the maintenance of high genetic variability in sperm production despite strong selection acting on it. © 2018 The Author(s). Evolution © 2018 The Society for the Study of Evolution.

Sexuality Education Beliefs among Sexually Experienced Youth: Differences by Gender and Birth Control Use

ERIC Educational Resources Information Center

Tolma, Eleni L.; Vesely, Sara K.; Oman, Roy F.; Aspy, Cheryl B.; Rodine, Sharon

2006-01-01

Purpose: To examine whether gender and birth control use are associated with premarital sexual attitudes, beliefs about peers, family communication about sexual relationships, and sexuality education among sexually experienced youth. Methods: Data were collected from a randomly selected ethnically diverse youth sample (N = 1,253). Only the…

Menstrual cycle phase alters women's sexual preferences for composers of more complex music.

PubMed

Charlton, Benjamin D

2014-06-07

Over 140 years ago Charles Darwin first argued that birdsong and human music, having no clear survival benefit, were obvious candidates for sexual selection. Whereas the first contention is now universally accepted, his theory that music is a product of sexual selection through mate choice has largely been neglected. Here, I provide the first, to my knowledge, empirical support for the sexual selection hypothesis of music evolution by showing that women have sexual preferences during peak conception times for men that are able to create more complex music. Two-alternative forced-choice experiments revealed that woman only preferred composers of more complex music as short-term sexual partners when conception risk was highest. No preferences were displayed when women chose which composer they would prefer as a long-term partner in a committed relationship, and control experiments failed to reveal an effect of conception risk on women's preferences for visual artists. These results suggest that women may acquire genetic benefits for offspring by selecting musicians able to create more complex music as sexual partners, and provide compelling support for Darwin's assertion 'that musical notes and rhythm were first acquired by the male or female progenitors of mankind for the sake of charming the opposite sex'.

Pedophilic brain potential responses to adult erotic stimuli.

PubMed

Knott, Verner; Impey, Danielle; Fisher, Derek; Delpero, Emily; Fedoroff, Paul

2016-02-01

Cognitive mechanisms associated with the relative lack of sexual interest in adults by pedophiles are poorly understood and may benefit from investigations examining how the brain processes adult erotic stimuli. The current study used event-related brain potentials (ERP) to investigate the time course of the explicit processing of erotic, emotional, and neutral pictures in 22 pedophilic patients and 22 healthy controls. Consistent with previous studies, early latency anterior ERP components were highly selective for erotic pictures. Although the ERPs elicited by emotional stimuli were similar in patients and controls, an early frontal positive (P2) component starting as early as 185 ms was significantly attenuated and slow to onset in pedophilia, and correlated with a clinical measure of cognitive distortions. Failure of rapid attentional capture by erotic stimuli suggests a relative reduction in early processing in pedophilic patients which may be associated with relatively diminished sexual interest in adults. Copyright © 2016. Published by Elsevier B.V.

Sexy faces in a male paper wasp.

PubMed

de Souza, André Rodrigues; Alberto Mourão Júnior, Carlos; do Nascimento, Fabio Santos; Lino-Neto, José

2014-01-01

Sexually selected signals are common in many animals, though little reported in social insects. We investigated the occurrence of male visual signals mediating the dominance relationships among males and female choice of sexual partner in the paper wasp Polistes simillimus. Males have three conspicuous, variable and sexually dimorphic traits: black pigmentation on the head, a pair of yellow abdominal spots and body size differences. By conducting behavioral assays, we found that none of the three visual traits are associated with male-male dominance relationship. However, males with higher proportion of black facial pigmentation and bigger yellow abdominal spots are more likely chosen as sexual partners. Also, after experimentally manipulating the proportion of black pigment on males' face, we found that females may evaluate male facial coloration during the choice of a sexual partner. Thus, the black pigmentation on P. simillimus male's head appears to play a role as a sexually selected visual signal. We suggest that sexual selection is a common force in Polistes and we highlight the importance of this group as a model for the study of visual communication in insects.

Sexual dimorphism is associated with population fitness in the seed beetle Callosobruchus maculatus.

PubMed

Rankin, Daniel J; Arnqvist, Göran

2008-03-01

The population consequences of sexual selection remain empirically unexplored. Comparative studies, involving extinction risk, have yielded different results as to the effect of sexual selection on population densities make contrasting predictions. Here, we investigate the relationship between sexual dimorphism (SD) and population productivity in the seed beetle Callosobruchus maculatus, using 13 populations that have evolved in isolation. Geometric morphometric methods and image analysis are employed to form integrative measures of sexual dimorphism, composed of variation in weight, size, body shape, and pigmentation. We found a positive relationship between SD and adult fitness (net adult offspring production) across our study populations, but failed to find any association between SD and juvenile fitness (egg-to-adult survival). Several mechanisms may have contributed to the pattern found, and variance in sexual selection regimes across populations, either in female choice for "good genes" or in the magnitude of direct benefits provided by their mates, would tend to produce the pattern seen. However, our results suggest that evolutionary constraints in the form of intralocus sexual conflict may have been the major generator of the relationship seen between SD and population fitness.

Sexy Faces in a Male Paper Wasp

PubMed Central

de Souza, André Rodrigues; Alberto Mourão Júnior, Carlos; Santos do Nascimento, Fabio; Lino-Neto, José

2014-01-01

Sexually selected signals are common in many animals, though little reported in social insects. We investigated the occurrence of male visual signals mediating the dominance relationships among males and female choice of sexual partner in the paper wasp Polistes simillimus. Males have three conspicuous, variable and sexually dimorphic traits: black pigmentation on the head, a pair of yellow abdominal spots and body size differences. By conducting behavioral assays, we found that none of the three visual traits are associated with male-male dominance relationship. However, males with higher proportion of black facial pigmentation and bigger yellow abdominal spots are more likely chosen as sexual partners. Also, after experimentally manipulating the proportion of black pigment on males' face, we found that females may evaluate male facial coloration during the choice of a sexual partner. Thus, the black pigmentation on P. simillimus male's head appears to play a role as a sexually selected visual signal. We suggest that sexual selection is a common force in Polistes and we highlight the importance of this group as a model for the study of visual communication in insects. PMID:24849073

Drpiwi-1 is essential for germline cell formation during sexualization of the planarian Dugesia ryukyuensis.

PubMed

Nakagawa, Haruka; Ishizu, Hirotsugu; Hasegawa, Reiko; Kobayashi, Kazuya; Matsumoto, Midori

2012-01-01

A piwi homolog is required for the regulation of stem cells, formation and maintenance of germline stem cells, and gametogenesis in many metazoans. Planarians can change their reproductive mode seasonally, both asexually and sexually, and develop and maintain germ cells and sexual organs. They have many pluripotent stem cells (neoblasts) that can differentiate into both somatic and germline stem cells. Thus, we searched for a piwi subfamily in the planarian Dugesia ryukyuensis. Four piwi homologs, identified as Drpiwi-1, -2, -3, and -4, were expressed in sexually reproductive worms. We then selectively destroyed the neoblasts by irradiating the worms with X-rays. In such worms, Drpiwi-1, -2, and -3 were not expressed at all, whereas Drpiwi-4 was expressed to the same degree as that in non-irradiated controls, indicating that Drpiwi-1, -2, and -3, but not Drpiwi-4, are expressed in neoblasts. During the regeneration process, Drpiwi-2(RNAi) and -3(RNAi) worms failed to regenerate after ablation, but Drpiwi-1 and -4(RNAi) worms regenerated. During the sexualizing process, Drpiwi-1(RNAi) worms failed to develop ovaries and testes, but somatic sexual organs were unaffected. Germ cell development was normal in Drpiwi-4(RNAi) worms. Therefore, Drpiwi-2 and -3 may be related to the regulation of neoblasts important for maintaining homeostasis, and Drpiwi-1 is essential for the development of germ cells but not somatic sexual organs. DrPiwi-1 is localized in the cytoplasm of stem cells and germline cells and may be involved in regulating some gene expression. We suggest that planarian Piwi controls germline formation via RNA silencing mechanisms. Crown Copyright © 2011. Published by Elsevier Inc. All rights reserved.

Female sexual dysfunction in patients with major depressive disorder (MDD) treated with selective serotonin reuptake inhibitor (SSRI) and its association with serotonin 2A-1438 G/A single nucleotide polymorphisms.

PubMed

Masiran, Ruziana; Sidi, Hatta; Mohamed, Zahurin; Mohd Nazree, Nur Elia; Nik Jaafar, Nik Ruzyanei; Midin, Marhani; Das, Srijit; Mohamed Saini, Suriati

2014-04-01

Selective serotonin reuptake inhibitors (SSRIs) are known for their sexual side effects. Different SSRIs may affect different areas of sexual function at different rates. The study aimed to determine the prevalence of female sexual dysfunction (FSD), its clinical correlates, and association with 5HT2A (rs6311) single nucleotide polymorphisms (SNPs) in patients with major depressive disorder (MDD) who were on SSRI therapy. This was a cross-sectional study on 95 female outpatients with MDD treated with SSRI. The patients were in remission as determined by Montgomery-Asberg Depression Rating Scale. Genomic DNA was isolated from buccal swabs and samples were processed using a real time polymerase chain reaction. The presence or absence of FSD as measured by the Malay Version of Female Sexual Function Index and 5HT2A-1438 G/A (rs6311) SNP. The overall prevalence of FSD was 32.6%. After controlling for age, number of children, education level, total monthly income, SSRI types, and SSRI dosing, being employed significantly enhanced FSD by 4.5 times (odds ratio [OR] = 4.51; 95% confidence interval [CI] 1.00, 20.30; P = 0.05). Those having marital problems were 6.7 times more likely to have FSD (OR = 6.67; 95% CI 1.57, 28.34). 5HT2A-1438 G/A (rs6311) SNP was not significantly associated with FSD. There was no significant association between FSD and the 5HT2A (rs6311) SNP in patients with MDD on SSRI therapy. Employment status and marital state were significantly associated with FSD among these patients. © 2014 International Society for Sexual Medicine.

Balancing selection in species with separate sexes: insights from Fisher's geometric model.

PubMed

Connallon, Tim; Clark, Andrew G

2014-07-01

How common is balancing selection, and what fraction of phenotypic variance is attributable to balanced polymorphisms? Despite decades of research, answers to these questions remain elusive. Moreover, there is no clear theoretical prediction about the frequency with which balancing selection is expected to arise within a population. Here, we use an extension of Fisher's geometric model of adaptation to predict the probability of balancing selection in a population with separate sexes, wherein polymorphism is potentially maintained by two forms of balancing selection: (1) heterozygote advantage, where heterozygous individuals at a locus have higher fitness than homozygous individuals, and (2) sexually antagonistic selection (a.k.a. intralocus sexual conflict), where the fitness of each sex is maximized by different genotypes at a locus. We show that balancing selection is common under biologically plausible conditions and that sex differences in selection or sex-by-genotype effects of mutations can each increase opportunities for balancing selection. Although heterozygote advantage and sexual antagonism represent alternative mechanisms for maintaining polymorphism, they mutually exist along a balancing selection continuum that depends on population and sex-specific parameters of selection and mutation. Sexual antagonism is the dominant mode of balancing selection across most of this continuum. Copyright © 2014 by the Genetics Society of America.

Cross-sex genetic correlation does not extend to sexual size dimorphism in spiders

NASA Astrophysics Data System (ADS)

Turk, Eva; Kuntner, Matjaž; Kralj-Fišer, Simona

2018-02-01

Males and females are often subjected to different selection pressures for homologous traits, resulting in sex-specific optima. Because organismal attributes usually share their genetic architectures, sex-specific selection may lead to intralocus sexual conflict. Evolution of sexual dimorphism may resolve this conflict, depending on the degree of cross-sex genetic correlation ( r MF) and the strength of sex-specific selection. In theory, high r MF implies that sexes largely share the genetic base for a given trait and are consequently sexually monomorphic, while low r MF indicates a sex-specific genetic base and sexual dimorphism. Here, we broadly test this hypothesis on three spider species with varying degrees of female-biased sexual size dimorphism, Larinioides sclopetarius (sexual dimorphism index, SDI = 0.85), Nuctenea umbratica (SDI = 0.60), and Zygiella x-notata (SDI = 0.46). We assess r MF via same-sex and opposite-sex heritability estimates. We find moderate body mass heritability but no obvious patterns in sex-specific heritability. Against the prediction, the degree of sexual size dimorphism is unrelated to the relative strength of same-sex versus opposite-sex heritability. Our results do not support the hypothesis that sexual size dimorphism is negatively associated with r MF. We conclude that sex-specific genetic architecture may not be necessary for the evolution of a sexually dimorphic trait.

Human-induced evolution caused by unnatural selection through harvest of wild animals

PubMed Central

Allendorf, Fred W.; Hard, Jeffrey J.

2009-01-01

Human harvest of phenotypically desirable animals from wild populations imposes selection that can reduce the frequencies of those desirable phenotypes. Hunting and fishing contrast with agricultural and aquacultural practices in which the most desirable animals are typically bred with the specific goal of increasing the frequency of desirable phenotypes. We consider the potential effects of harvest on the genetics and sustainability of wild populations. We also consider how harvesting could affect the mating system and thereby modify sexual selection in a way that might affect recruitment. Determining whether phenotypic changes in harvested populations are due to evolution, rather than phenotypic plasticity or environmental variation, has been problematic. Nevertheless, it is likely that some undesirable changes observed over time in exploited populations (e.g., reduced body size, earlier sexual maturity, reduced antler size, etc.) are due to selection against desirable phenotypes—a process we call “unnatural” selection. Evolution brought about by human harvest might greatly increase the time required for over-harvested populations to recover once harvest is curtailed because harvesting often creates strong selection differentials, whereas curtailing harvest will often result in less intense selection in the opposing direction. We strongly encourage those responsible for managing harvested wild populations to take into account possible selective effects of harvest management and to implement monitoring programs to detect exploitation-induced selection before it seriously impacts viability. PMID:19528656

Prevalence of disruptive selection predicts extent of species differentiation in Lake Victoria cichlids.

PubMed

van Rijssel, Jacco C; Moser, Florian N; Frei, David; Seehausen, Ole

2018-01-31

Theory suggests that speciation with gene flow is most likely when both sexual and ecological selection are divergent or disruptive. Divergent sexual and natural selection on the visual system have been demonstrated before in sympatric, morphologically similar sister species of Lake Victoria cichlids, but this does not explain the subtle morphological differences between them. To investigate the significance of natural selection on morphology during speciation, we here ask whether the prevalence of disruptive ecological selection differs between sympatric sister species that are at different stages of speciation. Some of our species pairs do ( Pundamilia ) and others do not ( Neochromis ) differ distinctively in sexually selected male nuptial coloration. We find that (i) evidence for disruptive selection, and for evolutionary response to it, is prevalent in traits that are differentiated between sister species; (ii) prevalence of both predicts the extent of genetic differentiation; and (iii) genetic differentiation is weaker in species pairs with conserved male nuptial coloration. Our results speak to the existence of two different mechanisms of speciation with gene flow: speciation mainly by sexual selection tightly followed by ecological character displacement in some cases and speciation mainly by divergent ecological selection in others. © 2018 The Author(s).

Polyandry and sex-specific gene expression

PubMed Central

Mank, Judith E.; Wedell, Nina; Hosken, David J.

2013-01-01

Polyandry is widespread in nature, and has important evolutionary consequences for the evolution of sexual dimorphism and sexual conflict. Although many of the phenotypic consequences of polyandry have been elucidated, our understanding of the impacts of polyandry and mating systems on the genome is in its infancy. Polyandry can intensify selection on sexual characters and generate more intense sexual conflict. This has consequences for sequence evolution, but also for sex-biased gene expression, which acts as a link between mating systems, sex-specific selection and the evolution of sexual dimorphism. We discuss this and the remarkable confluence of sexual-conflict theory and patterns of gene expression, while also making predictions about transcription patterns, mating systems and sexual conflict. Gene expression is a key link in the genotype–phenotype chain, and although in its early stages, understanding the sexual selection–transcription relationship will provide significant insights into this critical association. PMID:23339238

Parental selection of children's sexual orientation.

PubMed

Greenberg, A S; Bailey, J M

2001-08-01

As we learn more about the causes of sexual orientation, the likelihood increases that parents will one day be able to select the orientation of their children. This possibility (at least that of selecting for heterosexuality) has generated a great deal of concern among supporters of homosexual rights, with such selection being widely condemned as harmful and morally repugnant. Notwithstanding this widespread condemnation, and even assuming, as we do, that homosexuality is entirely acceptable morally, allowing parents, by means morally unproblematic in themselves, to select for heterosexuality would be morally acceptable. This is because allowing parents to select their children's sexual orientation would further parent's freedom to raise the sort of children they wish to raise and because selection for heterosexuality may benefit parents and children and is unlikely to cause significant harm.

The nature of allometry in an exaggerated trait: The postocular flange in Platyneuromus Weele (Insecta: Megaloptera).

PubMed

Ramírez-Ponce, Andrés; Garfias-Lozano, Gabriela; Contreras-Ramos, Atilano

2017-01-01

The origin and function of exaggerated traits exhibited by a great number of species with sexual dimorphism remain largely unexplored. The usual model considered as the evolutionary mechanism for the development of these structures is sexual selection. The nature of growth of the postocular flange (POF) in three species of the dobsonfly genus Platyneuromus (Megaloptera, Corydalidae, Corydalinae) is analyzed to explore sexual size dimorphism and allometric scaling. Results involve positive allometry of POF in males of two species, and negative allometry in males of one species, in general with a female-biased sexual dimorphism. We suggest an ancestral condition of dual incipient ornamentation in Platyneuromus, with a subsequent departure of size and shape of POF in males, triggered by sexual selection. Different sexual selection intensities may explain the parallel or divergent growth of POF within the scheme of dual ornamentation. Empirical behavioral data as well as a phylogenetic framework are necessary to clarify possible causes of phenotypic development, time of origin, and evolution of the POF.

Networking activities and perceptions of HIV risk among male migrant market vendors in China.

PubMed

Wang, Wenqing; Muessig, Kathryn E; Li, Mingqiang; Zhang, Ying-Xia; Zhang, Yingxia

2014-02-01

HIV research among internal migrants in China has not fully explored the contexts and perceptions of "risk". In 2011, urban markets in Liuzhou, China were mapped, and sixty male vendors, age 22-56, were selected for in-depth interviews on migration, social and family life, and perceptions and practices of sexual risk behavior. Participants were evenly divided among higher income shop and small stall vendors. All men were sexually active. Only the shop vendors reported non-marital sexual partners, including concurrent partners (n = 15), commercial partners (n = 10), and other sexual relationships (n = 11). Shop vendors engaged in networking activities that facilitated commercial and non-commercial high-risk sex. Perceptions of HIV risk from commercial sex led some men to doubt the protective ability of condoms and rely on local (unproven) self-protection techniques. Networking activities played a role in high-risk sex and shaping migrants' risk perceptions and health practices. The networks created through these processes could also be used to facilitate health promotion activities.

Safe Schools and Sexual Harassment: The Relationship between School Climate and Coping with Unwanted Sexual Behaviour

ERIC Educational Resources Information Center

Timmerman, M. C.

2004-01-01

Objective: To explore the impact of the school climate on adolescents' reporting of sexual harassment. Design: A quantitative survey among students in their 4th year of secondary education. Setting: Questionnaires were completed in a class setting. Method: An a-select sampling strategy was used to select 2808 students in 22 schools. Results:…

Senior Adult Sexuality in Age Segregated and Age Integrated Communities.

ERIC Educational Resources Information Center

Weinstein, Stellye; Rosen, Efrem

1988-01-01

Middle-income older adults (N=314) responded to senior adult sexuality scale. Results showed that respondents who selected to reside in age-segregated leisure-type retirement communities exhibited significantly more sexual interest, sexual activities, and liberal sexual attitudes than did respondents residing in age-integrated mainstream…

Effectiveness of the Sexual Attitude Restructuring Curriculum amongst Taiwanese Graduate Students

ERIC Educational Resources Information Center

Lin, Yi-Li; Lin, Yen-Chin

2018-01-01

This article discusses the effectiveness of the Sexual Attitude Restructuring (SAR) curriculum in developing positive sexual attitudes amongst Taiwanese graduate students in human sexuality. Through purposive sampling, 32 graduate students in human sexuality were selected to participate in the study. Before and after providing participants with a…

Sexual Self-Concept and Sexual Risk-Taking.

ERIC Educational Resources Information Center

Breakwell, Glynis M.; Millward, Lynne J.

1997-01-01

Presents data from a survey of randomly selected adolescents (N=474) which examined differences between male and female sexual identities. Results indicate two main dimensions in male sexual self-concept: socioemotional and the relational. Female sexual self-concept revolved around concerns with assertiveness, such as controlling when sex occurs.…

Do males pay for sex? Sex-specific selection coefficients suggest not.

PubMed

Prokop, Zofia M; Prus, Monika A; Gaczorek, Tomasz S; Sychta, Karolina; Palka, Joanna K; Plesnar-Bielak, Agata; Skarboń, Magdalena

2017-03-01

Selection acting on males can reduce mutation load of sexual relative to asexual populations, thus mitigating the twofold cost of sex, provided that it seeks and destroys the same mutations as selection acting on females, but with higher efficiency. This could happen due to sexual selection-a potent evolutionary force that in most systems predominantly affects males. We used replicate populations of red flour beetles (Tribolium castaneum) to study sex-specific selection against deleterious mutations introduced with ionizing radiation. We found no evidence for selection being stronger in males than in females; in fact, we observed a nonsignificant trend in the opposite direction. This suggests that selection on males does not reduce mutation load below the level expected under the (hypothetical) scenario of asexual reproduction. Additionally, we employed a novel approach, based on a simple model, to quantify the relative contributions of sexual and offspring viability selection to the overall selection observed in males. We found them to be similar in magnitude; however, only the offspring viability component was statistically significant. In summary, we found no support for the hypothesis that selection on males in general, and sexual selection in particular, contributes to the evolutionary maintenance of sex. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

Sexual selection affects local extinction and turnover in bird communities

USGS Publications Warehouse

Doherty, P.F.; Sorci, G.; Royle, J. Andrew; Hines, J.E.; Nichols, J.D.; Boulinier, T.

2003-01-01

Predicting extinction risks has become a central goal for conservation and evolutionary biologists interested in population and community dynamics. Several factors have been put forward to explain risks of extinction, including ecological and life history characteristics of individuals. For instance, factors that affect the balance between natality and mortality can have profound effects on population persistence. Sexual selection has been identified as one such factor. Populations under strong sexual selection experience a number of costs ranging from increased predation and parasitism to enhanced sensitivity to environmental and demographic stochasticity. These findings have led to the prediction that local extinction rates should be higher for species/populations with intense sexual selection. We tested this prediction by analyzing the dynamics of natural bird communities at a continental scale over a period of 21 years (1975-1996), using relevant statistical tools. In agreement with the theoretical prediction, we found that sexual selection increased risks of local extinction (dichromatic birds had on average a 23% higher local extinction rate than monochromatic species). However, despite higher local extinction probabilities, the number of dichromatic species did not decrease over the period considered in this study. This pattern was caused by higher local turnover rates of dichromatic species, resulting in relatively stable communities for both groups of species. Our results suggest that these communities function as metacommunities, with frequent local extinctions followed by colonization. Anthropogenic factors impeding dispersal might therefore have a significant impact on the global persistence of sexually selected species.

A role for relaxed selection in the evolution of the language capacity

PubMed Central

Deacon, Terrence W.

2010-01-01

Explaining the extravagant complexity of the human language and our competence to acquire it has long posed challenges for natural selection theory. To answer his critics, Darwin turned to sexual selection to account for the extreme development of language. Many contemporary evolutionary theorists have invoked incredibly lucky mutation or some variant of the assimilation of acquired behaviors to innate predispositions in an effort to explain it. Recent evodevo approaches have identified developmental processes that help to explain how complex functional synergies can evolve by Darwinian means. Interestingly, many of these developmental mechanisms bear a resemblance to aspects of Darwin's mechanism of natural selection, often differing only in one respect (e.g., form of duplication, kind of variation, competition/cooperation). A common feature is an interplay between processes of stabilizing selection and processes of relaxed selection at different levels of organism function. These may play important roles in the many levels of evolutionary process contributing to language. Surprisingly, the relaxation of selection at the organism level may have been a source of many complex synergistic features of the human language capacity, and may help explain why so much language information is “inherited” socially. PMID:20445088

Can Foraging Ecology Drive the Evolution of Body Size in a Diving Endotherm?

PubMed Central

Cook, Timothée R.; Lescroël, Amélie; Cherel, Yves; Kato, Akiko; Bost, Charles-André

2013-01-01

Within a single animal species, different morphs can allow for differential exploitation of foraging niches between populations, while sexual size dimorphism can provide each sex with access to different resources. Despite being potentially important agents of evolution, resource polymorphisms, and the way they operate in wild populations, remain poorly understood. In this study, we examine how trophic factors can select for different body sizes between populations and sexes in a diving endotherm. Dive depth and duration are positively related to body size in diving birds and mammals, a relationship explained by a lower mass-specific metabolic rate and greater oxygen stores in larger individuals. Based on this allometry, we predict that selection for exploiting resources situated at different depths can drive the evolution of body size in species of diving endotherms at the population and sexual level. To test this prediction, we studied the foraging ecology of Blue-eyed Shags, a group of cormorants with male-biased sexual size dimorphism from across the Southern Ocean. We found that mean body mass and relative difference in body mass between sexes varied by up to 77% and 107% between neighbouring colonies, respectively. Birds from colonies with larger individuals dived deeper than birds from colonies with smaller individuals, when accounting for sex. In parallel, males dived further offshore and deeper than females and the sexual difference in dive depth reflected the level of sexual size dimorphism at each colony. We argue that body size in this group of birds is under intense selection for diving to depths of profitable benthic prey patches and that, locally, sexual niche divergence selection can exaggerate the sexual size dimorphism of Blue-eyed Shags initially set up by sexual selection. Our findings suggest that trophic resources can select for important geographic micro-variability in body size between populations and sexes. PMID:23409169

Can foraging ecology drive the evolution of body size in a diving endotherm?

PubMed

Cook, Timothée R; Lescroël, Amélie; Cherel, Yves; Kato, Akiko; Bost, Charles-André

2013-01-01

Within a single animal species, different morphs can allow for differential exploitation of foraging niches between populations, while sexual size dimorphism can provide each sex with access to different resources. Despite being potentially important agents of evolution, resource polymorphisms, and the way they operate in wild populations, remain poorly understood. In this study, we examine how trophic factors can select for different body sizes between populations and sexes in a diving endotherm. Dive depth and duration are positively related to body size in diving birds and mammals, a relationship explained by a lower mass-specific metabolic rate and greater oxygen stores in larger individuals. Based on this allometry, we predict that selection for exploiting resources situated at different depths can drive the evolution of body size in species of diving endotherms at the population and sexual level. To test this prediction, we studied the foraging ecology of Blue-eyed Shags, a group of cormorants with male-biased sexual size dimorphism from across the Southern Ocean. We found that mean body mass and relative difference in body mass between sexes varied by up to 77% and 107% between neighbouring colonies, respectively. Birds from colonies with larger individuals dived deeper than birds from colonies with smaller individuals, when accounting for sex. In parallel, males dived further offshore and deeper than females and the sexual difference in dive depth reflected the level of sexual size dimorphism at each colony. We argue that body size in this group of birds is under intense selection for diving to depths of profitable benthic prey patches and that, locally, sexual niche divergence selection can exaggerate the sexual size dimorphism of Blue-eyed Shags initially set up by sexual selection. Our findings suggest that trophic resources can select for important geographic micro-variability in body size between populations and sexes.

Multivariate sexual selection on male tegmina in wild populations of sagebrush crickets, Cyphoderris strepitans (Orthoptera: Haglidae).

PubMed

Ower, G D; Hunt, J; Sakaluk, S K

2017-02-01

Although the strength and form of sexual selection on song in male crickets have been studied extensively, few studies have examined selection on the morphological structures that underlie variation in males' song, particularly in wild populations. Geometric morphometric techniques were used to measure sexual selection on the shape, size and symmetry of both top and bottom tegmina in wild populations of sagebrush crickets, a species in which nuptial feeding by females imposes an unambiguous phenotypic marker on males. The size of the tegmina negatively covaried with song dominant frequency and positively covaried with song pulse duration. Sexual selection was more intense on the bottom tegmen, conceivably because it interacts more freely with the subtegminal airspace, which may play a role in song amplification. An expanded coastal/subcostal region was one of the phenotypes strongly favoured by disruptive selection on the bottom tegmen, an adaptation that may form a more effective seal with the thorax to prevent noise cancellation. Directional selection also favoured increased symmetry in tegminal shape. Assuming more symmetrical males are better able to buffer against developmental noise, the song produced by these males may make them more attractive to females. Despite the strong stabilizing selection documented previously on the dominant frequency of the song, stabilizing selection on the resonator that regulates dominant frequency was surprisingly absent. Nonetheless, wing morphology had an important influence on song structure and appears to be subject to significant linear and nonlinear sexual selection through female mate choice. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

Sexy sons: a dead end for cytoplasmic genes.

PubMed

Zeh, Jeanne A

2004-08-07

Critics of sexual conflict theory argue that females may gain a net reproductive benefit from mating with manipulative males because the direct costs that they suffer may be offset by the production of sexy, i.e. manipulative, sons. However, this exclusive focus on nuclear gene effects represents an incomplete view of female fitness. Females differ fundamentally from males in transmitting not only nuclear genes but also a wide range of cytoplasmic genetic elements (CGEs) that can have profound effects, from male killing to influencing development of the nervous system and cognitive ability. Maternal transmission of CGEs has two major implications for sexual selection. First, the evolution of male fitness traits, such as sperm competitive ability, may be constrained because response to selection on mitochondrial genomes can occur only through the female line. Second, CGEs bear the direct costs of male manipulation but gain no indirect benefits when females produce sexy sons. This should result in perpetual antagonistic coevolution between nuclear genes involved in male manipulation and CGEs that promote female resistance to male sexually selected traits. Explicit consideration of the consequences of selection acting on CGEs is therefore necessary for a better understanding of the relationship between sexual selection and sexual conflict.

Sexy sons: a dead end for cytoplasmic genes.

PubMed Central

Zeh, Jeanne A

2004-01-01

Critics of sexual conflict theory argue that females may gain a net reproductive benefit from mating with manipulative males because the direct costs that they suffer may be offset by the production of sexy, i.e. manipulative, sons. However, this exclusive focus on nuclear gene effects represents an incomplete view of female fitness. Females differ fundamentally from males in transmitting not only nuclear genes but also a wide range of cytoplasmic genetic elements (CGEs) that can have profound effects, from male killing to influencing development of the nervous system and cognitive ability. Maternal transmission of CGEs has two major implications for sexual selection. First, the evolution of male fitness traits, such as sperm competitive ability, may be constrained because response to selection on mitochondrial genomes can occur only through the female line. Second, CGEs bear the direct costs of male manipulation but gain no indirect benefits when females produce sexy sons. This should result in perpetual antagonistic coevolution between nuclear genes involved in male manipulation and CGEs that promote female resistance to male sexually selected traits. Explicit consideration of the consequences of selection acting on CGEs is therefore necessary for a better understanding of the relationship between sexual selection and sexual conflict. PMID:15504002

The effects of selection and genetic drift on the genomic distribution of sexually antagonistic alleles.

PubMed

Mullon, Charles; Pomiankowski, Andrew; Reuter, Max

2012-12-01

Sexual antagonism (SA) occurs when an allele that is beneficial to one sex, is detrimental to the other. This conflict can result in balancing, directional, or disruptive selection acting on SA alleles. A body of theory predicts the conditions under which sexually antagonistic mutants will invade and be maintained in stable polymorphism under balancing selection. There remains, however, considerable debate over the distribution of SA genetic variation across autosomes and sex chromosomes, with contradictory evidence coming from data and theory. In this article, we investigate how the interplay between selection and genetic drift will affect the genomic distribution of sexually antagonistic alleles. The effective population sizes can differ between the autosomes and the sex chromosomes due to a number of ecological factors and, consequently, the distribution of SA genetic variation in genomes. In general, we predict the interplay of SA selection and genetic drift should lead to the accumulation of SA alleles on the X in male heterogametic (XY) species and, on the autosomes in female heterogametic (ZW) species, especially when sexual competition is strong among males. © 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.

Variation in recombination frequency and distribution across eukaryotes: patterns and processes

PubMed Central

Feulner, Philine G. D.; Johnston, Susan E.; Santure, Anna W.; Smadja, Carole M.

2017-01-01

Recombination, the exchange of DNA between maternal and paternal chromosomes during meiosis, is an essential feature of sexual reproduction in nearly all multicellular organisms. While the role of recombination in the evolution of sex has received theoretical and empirical attention, less is known about how recombination rate itself evolves and what influence this has on evolutionary processes within sexually reproducing organisms. Here, we explore the patterns of, and processes governing recombination in eukaryotes. We summarize patterns of variation, integrating current knowledge with an analysis of linkage map data in 353 organisms. We then discuss proximate and ultimate processes governing recombination rate variation and consider how these influence evolutionary processes. Genome-wide recombination rates (cM/Mb) can vary more than tenfold across eukaryotes, and there is large variation in the distribution of recombination events across closely related taxa, populations and individuals. We discuss how variation in rate and distribution relates to genome architecture, genetic and epigenetic mechanisms, sex, environmental perturbations and variable selective pressures. There has been great progress in determining the molecular mechanisms governing recombination, and with the continued development of new modelling and empirical approaches, there is now also great opportunity to further our understanding of how and why recombination rate varies. This article is part of the themed issue ‘Evolutionary causes and consequences of recombination rate variation in sexual organisms’. PMID:29109219

Through their eyes: selective attention in peahens during courtship

PubMed Central

Yorzinski, Jessica L.; Patricelli, Gail L.; Babcock, Jason S.; Pearson, John M.; Platt, Michael L.

2013-01-01

SUMMARY Conspicuous, multicomponent ornamentation in male animals can be favored by female mate choice but we know little about the cognitive processes females use to evaluate these traits. Sexual selection may favor attention mechanisms allowing the choosing females to selectively and efficiently acquire relevant information from complex male display traits and, in turn, may favor male display traits that effectively capture and hold female attention. Using a miniaturized telemetric gaze-tracker, we show that peahens (Pavo cristatus) selectively attend to specific components of peacock courtship displays and virtually ignore other, highly conspicuous components. Females gazed at the lower train but largely ignored the head, crest and upper train. When the lower train was obscured, however, females spent more time gazing at the upper train and approached the upper train from a distance. Our results suggest that peahens mainly evaluate the lower train during close-up courtship but use the upper train as a long-distance attraction signal. Furthermore, we found that behavioral display components (train rattling and wing shaking) captured and maintained female attention, indicating that interactions between display components may promote the evolution of multicomponent displays. Taken together, these findings suggest that selective attention plays a crucial role in sexual selection and likely influences the evolution of male display traits. PMID:23885088

Sexual selection on male size drives the evolution of male-biased sexual size dimorphism via the prolongation of male development.

PubMed

Rohner, Patrick T; Blanckenhorn, Wolf U; Puniamoorthy, Nalini

2016-06-01

Sexual size dimorphism (SSD) arises when the net effects of natural and sexual selection on body size differ between the sexes. Quantitative SSD variation between taxa is common, but directional intraspecific SSD reversals are rare. We combined micro- and macroevolutionary approaches to study geographic SSD variation in closely related black scavenger flies. Common garden experiments revealed stark intra- and interspecific variation: Sepsis biflexuosa is monomorphic across the Holarctic, while S. cynipsea (only in Europe) consistently exhibits female-biased SSD. Interestingly, S. neocynipsea displays contrasting SSD in Europe (females larger) and North America (males larger), a pattern opposite to the geographic reversal in SSD of S. punctum documented in a previous study. In accordance with the differential equilibrium model for the evolution of SSD, the intensity of sexual selection on male size varied between continents (weaker in Europe), whereas fecundity selection on female body size did not. Subsequent comparative analyses of 49 taxa documented at least six independent origins of male-biased SSD in Sepsidae, which is likely caused by sexual selection on male size and mediated by bimaturism. Therefore, reversals in SSD and the associated changes in larval development might be much more common and rapid and less constrained than currently assumed. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

Evolution of male and female genitalia following release from sexual selection.

PubMed

Cayetano, Luis; Maklakov, Alexei A; Brooks, Robert C; Bonduriansky, Russell

2011-08-01

Despite the key functions of the genitalia in sexual interactions and fertilization, the role of sexual selection and conflict in shaping genital traits remains poorly understood. Seed beetle (Callosobruchus maculatus) males possess spines on the intromittent organ, and females possess a thickened reproductive tract wall that also bears spines. We investigated the role of sexual selection and conflict by imposing monogamous mating on eight replicate populations of this naturally polygamous insect, while maintaining eight other populations under polygamy. To establish whether responses to mating system manipulation were robust to ecological context, we simultaneously manipulated life-history selection (early/late reproduction). Over 18-21 generations, male genital spines evolved relatively reduced length in large males (i.e., shallower static allometry) in monogamous populations. Two nonintromittent male genital appendages also evolved in response to the interaction of mating system and ecology. In contrast, no detectable evolution occurred in female genitalia, consistent with the expectation of a delayed response in defensive traits. Our results support a sexually antagonistic role for the male genital spines, and demonstrate the evolution of static allometry in response to variation in sexual selection opportunity. We argue that further advances in the study of genital coevolution will require a much more detailed understanding of the functions of male and female genital traits. © 2011 The Author(s). Evolution© 2011 The Society for the Study of Evolution.

'And next, just for your enjoyment!': sex, technology and the constitution of desire.

PubMed

Dowsett, Gary W

2015-01-01

In the 1976 sci-fi film Logan's Run, actor Michael York, relaxing in a fetching caftan after a day hunting 'Runners', logs-in to the 'Circuit', a de- and re-materialisation technology that allows those seeking sex to select partners. Logan's first candidate, a young man, is passed over with a smile. The second is co-star Jenny Agutter; she is accepted and we join a sexual ride in the future. Online dating sites such as Gaydar® and RSVP® would seem to have a long way to go to achieve that, and Microsoft™ needs some fast apps development to get us there. Against this background, this paper examines some starting points in our fascination with technosex, long before the Internet, in books and magazines, the creative arts and other media and cultural forms. It focuses upon gay men's contribution to this fascination, and looks at the queering of heterosexuality and the part technology has played in that process. Online technologies are examined, particularly in relation to the 'publicisation' of sexual life and to shifts in sexual identity and practice related to changing processes of sexual objectification, self-objectification and subjectification. Finally, the transformation of sex into health and healthy sex is discussed.

The effects of stress and sex on selection, genetic covariance, and the evolutionary response.

PubMed

Holman, L; Jacomb, F

2017-10-01

The capacity of a population to adapt to selection (evolvability) depends on whether the structure of genetic variation permits the evolution of fitter trait combinations. Selection, genetic variance and genetic covariance can change under environmental stress, and males and females are not genetically independent, yet the combined effects of stress and dioecy on evolvability are not well understood. Here, we estimate selection, genetic (co)variance and evolvability in both sexes of Tribolium castaneum flour beetles under stressful and benign conditions, using a half-sib breeding design. Although stress uncovered substantial latent heritability, stress also affected genetic covariance, such that evolvability remained low under stress. Sexual selection on males and natural selection on females favoured a similar phenotype, and there was positive intersex genetic covariance. Consequently, sexual selection on males augmented adaptation in females, and intralocus sexual conflict was weak or absent. This study highlights that increased heritability does not necessarily increase evolvability, suggests that selection can deplete genetic variance for multivariate trait combinations with strong effects on fitness, and tests the recent hypothesis that sexual conflict is weaker in stressful or novel environments. © 2017 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2017 European Society For Evolutionary Biology.

Selection on an antagonistic behavioral trait can drive rapid genital coevolution in the burying beetle, Nicrophorus vespilloides

PubMed Central

Hopwood, Paul E.; Head, Megan L.; Jordan, Eleanor J.; Carter, Mauricio J.; Davey, Emma; Moore, Allen J.; Royle, Nick J.

2016-01-01

Male and female genital morphology varies widely across many taxa, and even among populations. Disentangling potential sources of selection on genital morphology is problematic because each sex is predicted to respond to adaptations in the other due to reproductive conflicts of interest. To test how variation in this sexual conflict trait relates to variation in genital morphology we used our previously developed artificial selection lines for high and low repeated mating rates. We selected for high and low repeated mating rates using monogamous pairings to eliminate contemporaneous female choice and male–male competition. Male and female genital shape responded rapidly to selection on repeated mating rate. High and low mating rate lines diverged from control lines after only 10 generations of selection. We also detected significant patterns of male and female genital shape coevolution among selection regimes. We argue that because our selection lines differ in sexual conflict, these results support the hypothesis that sexually antagonistic coevolution can drive the rapid divergence of genital morphology. The greatest divergence in morphology corresponded with lines in which the resolution of sexual conflict over mating rate was biased in favor of male interests. PMID:27144373

Female homosexual behavior and inter-sexual mate competition in Japanese macaques: possible implications for sexual selection theory.

PubMed

Vasey, Paul L; Leca, Jean-Baptiste; Gunst, Noëlle; VanderLaan, Doug P

2014-10-01

In this paper, we review research related to female homosexual behavior in Japanese macaques (Macaca fuscata), including our 20-year program of research on this species. Multiple lines of evidence indicate that female homosexual behavior in this species is sexually motivated. In contrast, many sociosexual hypotheses have been tested in relation to female homosexual behavior in Japanese macaques, but none have been supported. Female Japanese macaques sometimes engage in same-sex sexual activity even when motivated opposite-sex alternatives are available. Within this context of mate choice, males compete inter-sexually for opportunities to copulate with females above and beyond any intra-sexual competition that is required. Anecdotal evidence suggests that inter-sexual competition for female sexual partners has been observed in a number of other species, including humans. At present it is unclear whether inter-sexual competition for sexual partners influences patterns of reproduction. Our understanding of sexual selection and the evolution of mating systems may be improved by investigating whether inter-sexual mate competition influences the acquisition and maintenance of reproductive partners in those species in which such interactions occur. Copyright © 2014 Elsevier Ltd. All rights reserved.

Sexually antagonistic selection during parental care is not generated by a testosterone-related intralocus sexual conflict-insights from full-sib comparisons.

PubMed

Iserbyt, Arne; Eens, Marcel; Müller, Wendt

2015-12-02

The evolution of shared male and female traits can be hampered if selection favours sex-specific optima. However, such genomic conflicts can be resolved when independent male and female mechanisms evolve. The existence, extent and consequences of conflict and/or conflict resolution are currently debated. Endocrinological traits like plasma testosterone (T) are suitable test cases, given their important role in mediating correlated traits, plus their opposing sex-specific fitness effects. We compared full-sibling (brother/sister) captive canaries to test for (1) sexually antagonistic selection characterized by contrasting fitness patterns within pairs of relatives, (2) intersexual genetic correlation of plasma T (h(²) = 0.41  ±  0.31) and (3) intralocus sexual conflict over T levels featured by distinct sex-specific fitness optima. We found potential for sexually antagonistic selection, since high fledgling mass was reached by either brothers or sisters, but not by both. We report a positive intersexual correlation for T, as a requirement for intralocus sexual conflict. However, high levels of T were associated with increased female and decreased male fitness (fledgling mass), which contrasts our expectations and challenges the hypothesis of intralocus sexual conflict driven by T. We hypothesize that behavioural and physiological trade-offs differ between sexes when raising offspring, driving T levels towards a state of monomorphism.

A test of the size-constraint hypothesis for a limit to sexual dimorphism in plants.

PubMed

Labouche, Anne-Marie; Pannell, John R

2016-07-01

In flowering plants, many dioecious species display a certain degree of sexual dimorphism in non-reproductive traits, but this dimorphism tends to be much less striking than that found in animals. Sexual size dimorphism in plants may be limited because competition for light in crowded environments so strongly penalises small plants. The idea that competition for light constrains the evolution of strong sexual size dimorphism in plants (the size-constraint hypothesis) implies a strong dependency of the expression of sexual size dimorphism on the neighbouring density as a result of the capacity of plants to adjust their reproductive effort and investment in growth in response to their local environment. Here, we tested this hypothesis by experimentally altering the context of competition for light among male-female pairs of the light-demanding dioecious annual plant Mercurialis annua. We found that males were smaller than females across all treatments, but sexual size dimorphism was diminished for pairs grown at higher densities. This result is consistent with the size-constraint hypothesis. We discuss our results in terms of the tension between selection on size acting in opposite directions on males and females, which have different optima under sexual selection, and stabilizing selection for similar sizes in males and females, which have similar optima under viability selection for plasticity in size expression under different density conditions.

Inter-genomic sexual conflict drives antagonistic coevolution in harvester ants

PubMed Central

Herrmann, Michael; Cahan, Sara Helms

2014-01-01

The reproductive interests of males and females are not always aligned, leading to sexual conflict over parental investment, rate of reproduction and mate choice. Traits that increase the genetic interests of one sex often occur at the expense of the other, selecting for counter-adaptations leading to antagonistic coevolution. Reproductive conflict is not limited to intraspecific interactions; interspecific hybridization can produce pronounced sexual conflict between males and females of different species, but it is unclear whether such conflict can drive sexually antagonistic coevolution between reproductively isolated genomes. We tested for hybridization-driven sexually antagonistic adaptations in queens and males of the socially hybridogenetic ‘J’ lineages of Pogonomyrmex harvester ants, whose mating system promotes hybridization in queens but selects against it in males. We conducted no-choice mating assays to compare patterns of mating behaviour and sperm transfer between inter- and intra-lineage pairings. There was no evidence for mate discrimination on the basis of pair type, and the total quantity of sperm transferred did not differ between intra- and inter-lineage pairs; however, further dissection of the sperm transfer process into distinct mechanistic components revealed significant, and opposing, cryptic manipulation of copulatory investment by both sexes. Males of both lineages increased their rate of sperm transfer to high-fitness intra-lineage mates, with a stronger response in the rarer lineage for whom mating mistakes are the most likely. By contrast, the total duration of copulation for intra-lineage mating pairs was significantly shorter than for inter-lineage crosses, suggesting that queens respond to prevent excessive sperm loading by prematurely terminating copulation. These findings demonstrate that sexual conflict can lead to antagonistic coevolution in both intra-genomic and inter-genomic contexts. Indeed, the resolution of sexual conflict may be a key determinant of the long-term evolutionary potential of host-dependent reproductive strategies, counteracting the inherent instabilities arising from such systems. PMID:25355474

Erotic subset for the Nencki Affective Picture System (NAPS ERO): cross-sexual comparison study.

PubMed

Wierzba, Małgorzata; Riegel, Monika; Pucz, Anna; Leśniewska, Zuzanna; Dragan, Wojciech Ł; Gola, Mateusz; Jednoróg, Katarzyna; Marchewka, Artur

2015-01-01

Research on the processing of sexual stimuli has proved that such material has high priority in human cognition. Yet, although sex differences in response to sexual stimuli were extensively discussed in the literature, sexual orientation was given relatively little consideration, and material suitable for relevant research is difficult to come by. With this in mind, we present a collection of 200 erotic images, accompanied by their self-report ratings of emotional valence and arousal by homo- and heterosexual males and females (n = 80, divided into four equal-sized subsamples). The collection complements the Nencki Affective Picture System (NAPS) and is intended to be used as stimulus material in experimental research. The erotic images are divided into five categories, depending on their content: opposite-sex couple (50), male couple (50), female couple (50), male (25) and female (25). Additional 100 control images from the NAPS depicting people in a non-erotic context were also used in the study. We showed that recipient sex and sexual orientation strongly influenced the evaluation of erotic content. Thus, comparisons of valence and arousal ratings in different subject groups will help researchers select stimuli set for the purpose of various experimental designs. To facilitate the use of the dataset, we provide an on-line tool, which allows the user to browse the images interactively and select proper stimuli on the basis of several parameters. The NAPS ERO image collection together with the data are available to the scientific community for non-commercial use at http://naps.nencki.gov.pl.

Erotic subset for the Nencki Affective Picture System (NAPS ERO): cross-sexual comparison study

PubMed Central

Wierzba, Małgorzata; Riegel, Monika; Pucz, Anna; Leśniewska, Zuzanna; Dragan, Wojciech Ł.; Gola, Mateusz; Jednoróg, Katarzyna; Marchewka, Artur

2015-01-01

Research on the processing of sexual stimuli has proved that such material has high priority in human cognition. Yet, although sex differences in response to sexual stimuli were extensively discussed in the literature, sexual orientation was given relatively little consideration, and material suitable for relevant research is difficult to come by. With this in mind, we present a collection of 200 erotic images, accompanied by their self-report ratings of emotional valence and arousal by homo- and heterosexual males and females (n = 80, divided into four equal-sized subsamples). The collection complements the Nencki Affective Picture System (NAPS) and is intended to be used as stimulus material in experimental research. The erotic images are divided into five categories, depending on their content: opposite-sex couple (50), male couple (50), female couple (50), male (25) and female (25). Additional 100 control images from the NAPS depicting people in a non-erotic context were also used in the study. We showed that recipient sex and sexual orientation strongly influenced the evaluation of erotic content. Thus, comparisons of valence and arousal ratings in different subject groups will help researchers select stimuli set for the purpose of various experimental designs. To facilitate the use of the dataset, we provide an on-line tool, which allows the user to browse the images interactively and select proper stimuli on the basis of several parameters. The NAPS ERO image collection together with the data are available to the scientific community for non-commercial use at http://naps.nencki.gov.pl. PMID:26441715

Non-random pairing in American kestrels: mate choice versus intra-sexual competition

USGS Publications Warehouse

Bortolotti, Gary R.; Iko, William M.

1992-01-01

Natural selection may influence the arrangement of individuals into mated pairs through either inter-sexual (mate choice) or intra-sexual selection (competition). A study of the American kestrel, Falco sparverius, in northern Saskatchewan distinguished between these two processes using size as a measure of the bird's competitive ability, and condition (mass scaled to body size) as an index of quality. Both sexes arrive on the study area after spring migration in equal numbers and males establish territories. Males and females that moved among territories at the time of pair formation were not different in size or condition from those that did not move, suggesting that birds were not being displaced by superior competitors, and that females moved to encounter potential mates. Within mated pairs, there was no relationship between a bird's size and the condition of its mate for either sex as would be predicted if intra-sexual competitition explained mating patterns. Instead, there was positive assortative mating by condition, suggesting that both sexes used quality as the criterion in choosing mates. There was no correlation between the sizes of males and females in mated paird. Because there were no differences in size or condition of breeding and non-breeding males, factors other than physical attributes, such as prior experience with the area, may determine a male's success in obtaining a territory. Because females that did not obtain mates were in poorer condition than those that did, males may have rejected poor quality females. The results suggest that intra-sexual competition was not important for pair formation, and that kestrels chose mates on the basis of quality.

Dopamine receptors play distinct roles in sexual behavior expression of rats with a different sexual motivational tone.

PubMed

Guadarrama-Bazante, Irma L; Canseco-Alba, Ana; Rodríguez-Manzo, Gabriela

2014-10-01

Dopamine (DA) plays a central role in the expression of male sexual behavior. The effects of DA-enhancing drugs on copulation seem to vary depending on the dose of the agonist used, the type of DA receptor activated, and the sexual condition of the animals. The aim of the present study was to carry out a systematic analysis of the effects of dopaminergic agonists on the expression of male sexual behavior by sexually competent rats in different sexual motivational states, that is when sexually active (sexually experienced) and when temporarily inhibited (sexually exhausted). To this end, the same doses of the nonselective DA receptor agonist apomorphine, the selective D2-like DA receptor agonist quinpirole, and the selective D1-like DA receptor agonist SKF38393 were injected intraperitoneally to sexually experienced or sexually exhausted male rats and their sexual behavior was recorded. Low apomorphine doses induced expression of sexual behavior in sexually satiated rats, but only reduced the intromission latency of sexually experienced rats. SKF38393 facilitated the expression of sexual behavior by sexually exhausted rats, but not that of sexually experienced males and quinpirole did not exert an effect in both types of animal. In line with these results, the apomorphine-induced reversal of sexual exhaustion was blocked by the D1-like receptor antagonist SCH23390. The data suggest that DA receptors play distinct roles in the expression of sexual behavior by male rats depending on their motivational state and that activation of D1-like receptors promotes the expression of sexual behavior in satiated rats.

On the affective force of "nasty love".

PubMed

Steinbock, Eliza

2014-01-01

Tackling the mimetic logic of sex-gender that limits the transsexual subject's sexuality into seeming a poor representation, the author argues that trans pornography and autoethnographic accounts from trans scholars emphasize the affective dimension of trans sex, a material remainder absent from mimetic theories of sexuality. Developing concepts from Alfred North Whitehead's process philosophy, in tandem with Morty Diamond's film Trans Entities: The Nasty Love of Papí and Wil (2007) and a selection of trans theorists, this article elaborates on the horizon of affective potential opened by transgender, brown, kinky, and pornographic "nastiness." The event of "nasty love" solicits a differential becoming, growing the edge of self.

Genetic conflict between sexual signalling and juvenile survival in the three-spined stickleback.

PubMed

Kim, Sin-Yeon; Velando, Alberto

2016-02-29

Secondary sexual traits and mating preferences may evolve in part because the offspring of attractive males inherit attractiveness and other genetically correlated traits such as fecundity and viability. A problem regarding these indirect genetic mechanisms is how sufficient genetic variation in the traits subject to sexual selection is maintained within a population. Here we explored the additive genetic correlations between carotenoid-based male ornament colouration, female fecundity and juvenile survival rate in the three-spined stickleback (Gasterosteus aculeatus) to test the possibility that attractiveness genes reduce important fitness components in the bearers not expressing the sexual trait. Male sexual attractiveness (i.e., red nuptial colouration) as well as female fecundity and juvenile viability showed heritable variations in the three-spined stickleback. Thus, females can gain indirect benefits by mating with an attractive male. There was a strong positive genetic correlation between female fecundity and juvenile viability. However, red sexual signal of male sticklebacks was negatively genetically correlated with juvenile survival, suggesting genetic conflict between attractiveness and viability. There was no significant correlation between attractiveness of brothers and fecundity of sisters, suggesting no intra-locus sexual conflict. The negative effects of mating with a colourful male on offspring viability may contribute to maintaining the heritable variation under strong directional sexual selection. The strength of indirect sexual selection may be weaker than previously thought due to the hidden genetic conflicts.

The Relationship between Childhood Sexual Abuse and Sexual Dysfunction in Jamaican Adults

ERIC Educational Resources Information Center

Swaby, Antoneal N.; Morgan, Kai A. D.

2009-01-01

This study examined the associations between early traumatic sexualization and later sexual dysfunction in a sample of 100 Jamaican adults while identifying the linkages between age, frequency of abuse, and gender on sexual functioning. Participants were selected via purposive and convenience sampling and divided equally into comparison and…

Dangerous mating systems: signal complexity, signal content and neural capacity in spiders.

PubMed

Herberstein, M E; Wignall, A E; Hebets, E A; Schneider, J M

2014-10-01

Spiders are highly efficient predators in possession of exquisite sensory capacities for ambushing prey, combined with machinery for launching rapid and determined attacks. As a consequence, any sexually motivated approach carries a risk of ending up as prey rather than as a mate. Sexual selection has shaped courtship to effectively communicate the presence, identity, motivation and/or quality of potential mates, which help ameliorate these risks. Spiders communicate this information via several sensory channels, including mechanical (e.g. vibrational), visual and/or chemical, with examples of multimodal signalling beginning to emerge in the literature. The diverse environments that spiders inhabit have further shaped courtship content and form. While our understanding of spider neurobiology remains in its infancy, recent studies are highlighting the unique and considerable capacities of spiders to process and respond to complex sexual signals. As a result, the dangerous mating systems of spiders are providing important insights into how ecology shapes the evolution of communication systems, with future work offering the potential to link this complex communication with its neural processes. Copyright © 2014 Elsevier Ltd. All rights reserved.

Reproductive skew drives patterns of sexual dimorphism in sponge-dwelling snapping shrimps

PubMed Central

Chak, Solomon Tin Chi; Duffy, J. Emmett; Rubenstein, Dustin R.

2015-01-01

Sexual dimorphism is typically a result of strong sexual selection on male traits used in male–male competition and subsequent female choice. However, in social species where reproduction is monopolized by one or a few individuals in a group, selection on secondary sexual characteristics may be strong in both sexes. Indeed, sexual dimorphism is reduced in many cooperatively breeding vertebrates and eusocial insects with totipotent workers, presumably because of increased selection on female traits. Here, we examined the relationship between sexual dimorphism and sociality in eight species of Synalpheus snapping shrimps that vary in social structure and degree of reproductive skew. In species where reproduction was shared more equitably, most members of both sexes were physiologically capable of breeding. However, in species where reproduction was monopolized by a single individual, a large proportion of females—but not males—were reproductively inactive, suggesting stronger reproductive suppression and conflict among females. Moreover, as skew increased across species, proportional size of the major chela—the primary antagonistic weapon in snapping shrimps—increased among females and sexual dimorphism in major chela size declined. Thus, as reproductive skew increases among Synalpheus, female–female competition over reproduction appears to increase, resulting in decreased sexual dimorphism in weapon size. PMID:26041357

The sight of the peacock's tail makes me sick: the early arguments on sexual selection.

PubMed

Hiraiwa-Hasegawa, M

2000-03-01

Why does a peacock have a beautiful train, while a peahen is sober without such flamboyance? Darwin proposed the theory of sexual selection to explain the differences between the sexes of the same species. Recently the study of sexual selection has been one of the most flourishing areas in evolutionary biology. However, the theory met with great resistance from biologists since the publication of the idea and the history of the theory included a lot of misunderstanding and confusion. There are several reasons for this. First, classical Darwinism failed to recognize social competition as an important selective force. Second, the good-for-the-species argument, which persisted in the days after Darwin, made the sexual selection argument more difficult to under-stand. Compared to the discussions on animals, Darwin's argument on human sex differences is not satisfactory. The reason probably lies in the debate over human racial differences which prevailed in the 19th century.

The tale of the shrinking weapon: seasonal changes in nutrition affect weapon size and sexual dimorphism, but not contemporary evolution.

PubMed

Miller, C W; McDonald, G C; Moore, A J

2016-11-01

Sexually selected traits are often highly variable in size within populations due to their close link with the physical condition of individuals. Nutrition has a large impact on physical condition, and thus, any seasonal changes in nutritional quality are predicted to alter the average size of sexually selected traits as well as the degree of sexual dimorphism in populations. However, although traits affected by mate choice are well studied, we have a surprising lack of knowledge of how natural variation in nutrition affects the expression of sexually selected weapons and sexual dimorphism. Further, few studies explicitly test for differences in the heritability and mean-scaled evolvability of sexually selected traits across conditions. We studied Narnia femorata (Hemiptera: Coreidae), an insect where males use their hind legs as weapons and the femurs are enlarged, to understand the extent to which weapon expression, sexual dimorphism and evolvability change across the actual range of nutrition available in the wild. We found that insects raised on a poor diet (cactus without fruit) are nearly monomorphic, whereas those raised on a high-quality diet (cactus with ripe fruit) are distinctly sexually dimorphic via the expression of large hind leg weapons in males. Contrary to our expectations, we found little evidence of a potential for evolutionary change for any trait measured. Thus, although we show weapons are highly condition dependent, and changes in weapon expression and dimorphism could alter evolutionary dynamics, our populations are unlikely to experience further evolutionary changes under current conditions. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

Hemiclonal analysis of interacting phenotypes in male and female Drosophila melanogaster

PubMed Central

2014-01-01

Background Identifying the sources of variation in mating interactions between males and females is important because this variation influences the strength and/or the direction of sexual selection that populations experience. While the origins and effects of variation in male attractiveness and ornamentation have received much scrutiny, the causes and consequences of intraspecific variation in females have been relatively overlooked. We used cytogenetic cloning techniques developed for Drosophila melanogaster to create “hemiclonal” males and females with whom we directly observed sexual interaction between individuals of different known genetic backgrounds and measured subsequent reproductive outcomes. Using this approach, we were able to quantify the genetic contribution of each mate to the observed phenotypic variation in biologically important traits including mating speed, copulation duration, and subsequent offspring production, as well as measure the magnitude and direction of intersexual genetic correlation between female choosiness and male attractiveness. Results We found significant additive genetic variation contributing to mating speed that can be attributed to male genetic identity, female genetic identity, but not their interaction. Furthermore we found that phenotypic variation in copulation duration had a significant male-associated genetic component. Female genetic identity and the interaction between male and female genetic identity accounted for a substantial amount of the observed phenotypic variation in egg size. Although previous research predicts a trade-off between egg size and fecundity, this was not evident in our results. We found a strong negative genetic correlation between female choosiness and male attractiveness, a result that suggests a potentially important role for sexually antagonistic alleles in sexual selection processes in our population. Conclusion These results further our understanding of sexual selection because they identify that genetic identity plays a significant role in phenotypic variation in female behaviour and fecundity. This variation may be potentially due to ongoing sexual conflict found between the sexes for interacting phenotypes. Our unexpected observation of a negative correlation between female choosiness and male attractiveness highlights the need for more explicit theoretical models of genetic covariance to investigate the coevolution of female choosiness and male attractiveness. PMID:24884361

Sexual selection favours male parental care, when females can choose

PubMed Central

Alonzo, Suzanne H.

2012-01-01

Explaining the evolution of male care has proved difficult. Recent theory predicts that female promiscuity and sexual selection on males inherently disfavour male care. In sharp contrast to these expectations, male-only care is often found in species with high extra-pair paternity and striking variation in mating success, where current theory predicts female-only care. Using a model that examines the coevolution of male care, female care and female choice; I show that inter-sexual selection can drive the evolution of male care when females are able to bias mating or paternity towards parental males. Surprisingly, female choice for parental males allows male care to evolve despite low relatedness between the male and the offspring in his care. These results imply that predicting how sexual selection affects parental care evolution will require further understanding of why females, in many species, either do not prefer or cannot favour males that provide care. PMID:22171082

The evolutionary outcome of sexual conflict

PubMed Central

Lessells, C(Kate). M

2006-01-01

Inter-locus sexual conflict occurs by definition when there is sexually antagonistic selection on a trait so that the optimal trait value differs between the sexes. As a result, there is selection on each sex to manipulate the trait towards its own optimum and resist such manipulation by the other sex. Sexual conflict often leads additionally to the evolution of harmful behaviour and to self-reinforcing and even perpetual sexually antagonistic coevolution. In an attempt to understand the determinants of these different outcomes, I compare two groups of traits—those related to parental investment (PI) and to mating—over which there is sexual conflict, but which have to date been explored by largely separate research traditions. A brief review suggests that sexual conflict over PI, particularly over PI per offspring, leads less frequently to the evolution of manipulative behaviour, and rarely to the evolution of harmful behaviour or to the rapid evolutionary changes which may be symptomatic of sexually antagonistic coevolution. The chief determinants of the evolutionary outcome of sexual conflict are the benefits of manipulation and resistance, the costs of manipulation and resistance, and the feasibility of manipulation. All three of these appear to contribute to the differences in the evolutionary outcome of conflicts over PI and mating. A detailed dissection of the evolutionary changes following from sexual conflict exposes greater complexity than a simple adaptation–counter-adaptation cycle and clarifies the role of harm. Not all of the evolutionary changes that follow from sexual conflict are sexually antagonistic, and harm is not necessary for sexually antagonistic coevolution to occur. In particular, whereas selection on the trait over which there is conflict is by definition sexually antagonistic, collateral harm is usually in the interest of neither sex. This creates the opportunity for palliative adaptations which reduce collateral harm. Failure to recognize that such adaptations are in the interest of both sexes can hinder our understanding of the evolutionary outcome of sexual conflict. PMID:16612889

The evolutionary outcome of sexual conflict.

PubMed

Lessells, C M

2006-02-28

Inter-locus sexual conflict occurs by definition when there is sexually antagonistic selection on a trait so that the optimal trait value differs between the sexes. As a result, there is selection on each sex to manipulate the trait towards its own optimum and resist such manipulation by the other sex. Sexual conflict often leads additionally to the evolution of harmful behaviour and to self-reinforcing and even perpetual sexually antagonistic coevolution. In an attempt to understand the determinants of these different outcomes, I compare two groups of traits-those related to parental investment (PI) and to mating-over which there is sexual conflict, but which have to date been explored by largely separate research traditions. A brief review suggests that sexual conflict over PI, particularly over PI per offspring, leads less frequently to the evolution of manipulative behaviour, and rarely to the evolution of harmful behaviour or to the rapid evolutionary changes which may be symptomatic of sexually antagonistic coevolution. The chief determinants of the evolutionary outcome of sexual conflict are the benefits of manipulation and resistance, the costs of manipulation and resistance, and the feasibility of manipulation. All three of these appear to contribute to the differences in the evolutionary outcome of conflicts over PI and mating. A detailed dissection of the evolutionary changes following from sexual conflict exposes greater complexity than a simple adaptation-counter-adaptation cycle and clarifies the role of harm. Not all of the evolutionary changes that follow from sexual conflict are sexually antagonistic, and harm is not necessary for sexually antagonistic coevolution to occur. In particular, whereas selection on the trait over which there is conflict is by definition sexually antagonistic, collateral harm is usually in the interest of neither sex. This creates the opportunity for palliative adaptations which reduce collateral harm. Failure to recognize that such adaptations are in the interest of both sexes can hinder our understanding of the evolutionary outcome of sexual conflict.

Selection for predation, not female fecundity, explains sexual size dimorphism in the orchid mantises.

PubMed

Svenson, Gavin J; Brannoch, Sydney K; Rodrigues, Henrique M; O'Hanlon, James C; Wieland, Frank

2016-12-01

Here we reconstruct the evolutionary shift towards floral simulation in orchid mantises and suggest female predatory selection as the likely driving force behind the development of extreme sexual size dimorphism. Through analysis of body size data and phylogenetic modelling of trait evolution, we recovered an ancestral shift towards sexual dimorphisms in both size and appearance in a lineage of flower-associated praying mantises. Sedentary female flower mantises dramatically increased in size prior to a transition from camouflaged, ambush predation to a floral simulation strategy, gaining access to, and visually attracting, a novel resource: large pollinating insects. Male flower mantises, however, remained small and mobile to facilitate mate-finding and reproductive success, consistent with ancestral male life strategy. Although moderate sexual size dimorphisms are common in many arthropod lineages, the predominant explanation is female size increase for increased fecundity. However, sex-dependent selective pressures acting outside of female fecundity have been suggested as mechanisms behind niche dimorphisms. Our hypothesised role of predatory selection acting on females to generate both extreme sexual size dimorphism coupled with niche dimorphism is novel among arthropods.

Selection for predation, not female fecundity, explains sexual size dimorphism in the orchid mantises

PubMed Central

Svenson, Gavin J.; Brannoch, Sydney K.; Rodrigues, Henrique M.; O’Hanlon, James C.; Wieland, Frank

2016-01-01

Here we reconstruct the evolutionary shift towards floral simulation in orchid mantises and suggest female predatory selection as the likely driving force behind the development of extreme sexual size dimorphism. Through analysis of body size data and phylogenetic modelling of trait evolution, we recovered an ancestral shift towards sexual dimorphisms in both size and appearance in a lineage of flower-associated praying mantises. Sedentary female flower mantises dramatically increased in size prior to a transition from camouflaged, ambush predation to a floral simulation strategy, gaining access to, and visually attracting, a novel resource: large pollinating insects. Male flower mantises, however, remained small and mobile to facilitate mate-finding and reproductive success, consistent with ancestral male life strategy. Although moderate sexual size dimorphisms are common in many arthropod lineages, the predominant explanation is female size increase for increased fecundity. However, sex-dependent selective pressures acting outside of female fecundity have been suggested as mechanisms behind niche dimorphisms. Our hypothesised role of predatory selection acting on females to generate both extreme sexual size dimorphism coupled with niche dimorphism is novel among arthropods. PMID:27905469

Independent evolution of the sexes promotes amphibian diversification

PubMed Central

De Lisle, Stephen P.; Rowe, Locke

2015-01-01

Classic ecological theory predicts that the evolution of sexual dimorphism constrains diversification by limiting morphospace available for speciation. Alternatively, sexual selection may lead to the evolution of reproductive isolation and increased diversification. We test contrasting predictions of these hypotheses by examining the relationship between sexual dimorphism and diversification in amphibians. Our analysis shows that the evolution of sexual size dimorphism (SSD) is associated with increased diversification and speciation, contrary to the ecological theory. Further, this result is unlikely to be explained by traditional sexual selection models because variation in amphibian SSD is unlikely to be driven entirely by sexual selection. We suggest that relaxing a central assumption of classic ecological models—that the sexes share a common adaptive landscape—leads to the alternative hypothesis that independent evolution of the sexes may promote diversification. Once the constraints of sexual conflict are relaxed, the sexes can explore morphospace that would otherwise be inaccessible. Consistent with this novel hypothesis, the evolution of SSD in amphibians is associated with reduced current extinction threat status, and an historical reduction in extinction rate. Our work reconciles conflicting predictions from ecological and evolutionary theory and illustrates that the ability of the sexes to evolve independently is associated with a spectacular vertebrate radiation. PMID:25694616

Using intervention mapping for the development of a targeted secure web-based outreach strategy named SafeFriend, for Chlamydia trachomatis testing in young people at risk

PubMed Central

2013-01-01

Background Many young people at high risk for Chlamydia trachomatis (Ct) are not reached by current sexual health care systems, such as general practitioners and public sexual health care centres (sexually transmitted infection clinics).Ct is the most frequently diagnosed bacterial sexually transmitted infection (STI) among sexually active people and in particular young heterosexuals. Innovative screening strategies are needed to interrupt the transmission of Ct among young people and connect the hidden cases to care. Methods Intervention Mapping (IM), a systematic approach to develop theory- and evidence-based interventions, was used to develop a strategy to target Ct testing towards young people who are currently hidden to care in The Netherlands. Both clinical users (i.e. sexual health care nurses) and public users (i.e., young people at risk for Ct) were closely involved in the IM process. A needs assessment study was carried out using semi-structured interviews among users (N = 21), a literature search and by taking lessons learned from existing screening programmes. Theoretical methods and practical applications to reach high risk young people and influence testing were selected and translated into specific programme components. Results The IM approach resulted in the development of a secure and web-based outreach Ct screening strategy, named SafeFriend. It is developed to target groups of high-risk young people who are currently hidden to care. Key methods include web-based Respondent Driven Sampling, starting from young Ct positive sexual health care centre clients, to reach and motivate peers (i.e., sex partners and friends) to get tested for Ct. Testing and the motivation of peers were proposed as the desired behavioural outcomes and the Precaution Adoption Process Model was chosen as theoretical framework. End users, i.e., young people and sexual health care nurses were interviewed and included in the development process to increase the success of implementation. Conclusions IM proved useful to develop an intervention for targeted Ct testing among young people. We believe this to be the first web-based outreach screening strategy which combines chain referral sampling with the delivery of targeted Ct testing to high risk young people within their sexual and social networks. PMID:24148656

Using intervention mapping for the development of a targeted secure web-based outreach strategy named SafeFriend, for Chlamydia trachomatis testing in young people at risk.

PubMed

Theunissen, Kevin A T M; Hoebe, Christian J P A; Crutzen, Rik; Kara-Zaïtri, Chakib; de Vries, Nanne K; van Bergen, Jan E A M; van der Sande, Marianne A B; Dukers-Muijrers, Nicole H T M

2013-10-22

Many young people at high risk for Chlamydia trachomatis (Ct) are not reached by current sexual health care systems, such as general practitioners and public sexual health care centres (sexually transmitted infection clinics).Ct is the most frequently diagnosed bacterial sexually transmitted infection (STI) among sexually active people and in particular young heterosexuals. Innovative screening strategies are needed to interrupt the transmission of Ct among young people and connect the hidden cases to care. Intervention Mapping (IM), a systematic approach to develop theory- and evidence-based interventions, was used to develop a strategy to target Ct testing towards young people who are currently hidden to care in The Netherlands. Both clinical users (i.e. sexual health care nurses) and public users (i.e., young people at risk for Ct) were closely involved in the IM process. A needs assessment study was carried out using semi-structured interviews among users (N = 21), a literature search and by taking lessons learned from existing screening programmes. Theoretical methods and practical applications to reach high risk young people and influence testing were selected and translated into specific programme components. The IM approach resulted in the development of a secure and web-based outreach Ct screening strategy, named SafeFriend. It is developed to target groups of high-risk young people who are currently hidden to care. Key methods include web-based Respondent Driven Sampling, starting from young Ct positive sexual health care centre clients, to reach and motivate peers (i.e., sex partners and friends) to get tested for Ct. Testing and the motivation of peers were proposed as the desired behavioural outcomes and the Precaution Adoption Process Model was chosen as theoretical framework. End users, i.e., young people and sexual health care nurses were interviewed and included in the development process to increase the success of implementation. IM proved useful to develop an intervention for targeted Ct testing among young people. We believe this to be the first web-based outreach screening strategy which combines chain referral sampling with the delivery of targeted Ct testing to high risk young people within their sexual and social networks.

Darwin on woman.

PubMed

Cohen, Claudine

2010-02-01

In his 1871 book The Descent of Man, Darwin exposed the idea of sexual selection as a major principle of human evolution. His main hypothesis, which was already briefly presented in The Origin of Species, is that there exists, besides "natural selection", another form of selection, milder in its effect, but no less efficient. This selection is operated by females to mate and reproduce with some partners that are gifted with more qualities than others, and more to their taste. At more evolved stages, sexual selection was exerted by men who became able to choose the women most attractive to their taste. However, Darwin insists, sexual selection in the human species is limited by a certain number of cultural practices. If Darwin's demonstration sometimes carried the prejudices of his times regarding gender differences he was the first who took into account the importance of sexual choices in his view on evolution, and who insisted on the evolutionary role of women at the dawn of humanity. Thus, he opened the space for a rich reflection, which after him was widely developed and discussed in anthropological and gender studies. 2010. Published by Elsevier SAS.

Is meiosis a fundamental cause of inviability among sexual and asexual plants and animals?

PubMed

Levitis, Daniel A; Zimmerman, Kolea; Pringle, Anne

2017-08-16

Differences in viability between asexually and sexually generated offspring strongly influence the selective advantage and therefore the prevalence of sexual reproduction (sex). However, no general principle predicts when sexual offspring will be more viable than asexual offspring. We hypothesize that when any kind of reproduction is based on a more complex cellular process, it will encompass more potential failure points, and therefore lower offspring viability. Asexual reproduction (asex) can be simpler than sex, when offspring are generated using only mitosis. However, when asex includes meiosis and meiotic restitution, gamete production is more complex than in sex. We test our hypothesis by comparing the viability of asexual and closely related sexual offspring across a wide range of plants and animals, and demonstrate that meiotic asex does result in lower viability than sex; without meiosis, asex is mechanistically simple and provides higher viability than sex. This phylogenetically robust pattern is supported in 42 of 44 comparisons drawn from diverse plants and animals, and is not explained by the other variables included in our model. Other mechanisms may impact viability, such as effects of reproductive mode on heterozygosity and subsequent viability, but we propose the complexity of cellular processes of reproduction, particularly meiosis, as a fundamental cause of early developmental failure and mortality. Meiosis, the leading cause of inviability in humans, emerges as a likely explanation of offspring inviability among diverse eukaryotes. © 2017 The Author(s).

Sexual selection on morphological and physiological traits and fluctuating asymmetry in the black scavenger fly Sepsis cynipsea.

PubMed

Blanckenhorn, W U; Kraushaar, U R S; Teuschl, Y; Reim, C

2004-05-01

Previous univariate studies of the fly Sepsis cynipsea (Diptera: Sepsidae) have demonstrated spatiotemporally variable and consequently overall weak sexual selection favouring large male size, which is nevertheless stronger on average than fecundity selection favouring larger females. To identify specific target(s) of selection on body size and additional traits possibly affecting mating success, two multivariate field studies of sexual selection were conducted. In one study using seasonal replicates from three populations, we assessed 15 morphological traits. No clear targets of sexual selection on male size could be detected, perhaps because spatiotemporal variation in selection was again strong. In particular, there was no (current) selection on male abdomen length or fore coxa length, the only traits for which S. cynipsea males are not smaller than females. Interestingly, copulating males had a consistently shorter fore femur base, a secondary sexual trait, and a wider clasper (hypopygium) gap, an external genital trait. In a second study using daily and seasonal replicates from one population, we included physiological measures of energy reserves (lipids, glucose, glycogen), in addition to hind tibia length and fluctuating asymmetry (FA) of all pairs of legs. This study again confirmed the mating advantage of large males, and additionally suggests independent positive influences of lipids (the long-term energy stores), with effects of glucose and glycogen (the short-term energy stores) tending to be negative. FA of paired traits was not associated with male mating success. Our study suggests that inclusion of physiological measures and genital traits in phenomenological studies of selection, which is rare, would be fruitful in other species.

Female brain size affects the assessment of male attractiveness during mate choice.

PubMed

Corral-López, Alberto; Bloch, Natasha I; Kotrschal, Alexander; van der Bijl, Wouter; Buechel, Severine D; Mank, Judith E; Kolm, Niclas

2017-03-01

Mate choice decisions are central in sexual selection theory aimed to understand how sexual traits evolve and their role in evolutionary diversification. We test the hypothesis that brain size and cognitive ability are important for accurate assessment of partner quality and that variation in brain size and cognitive ability underlies variation in mate choice. We compared sexual preference in guppy female lines selected for divergence in relative brain size, which we have previously shown to have substantial differences in cognitive ability. In a dichotomous choice test, large-brained and wild-type females showed strong preference for males with color traits that predict attractiveness in this species. In contrast, small-brained females showed no preference for males with these traits. In-depth analysis of optomotor response to color cues and gene expression of key opsins in the eye revealed that the observed differences were not due to differences in visual perception of color, indicating that differences in the ability to process indicators of attractiveness are responsible. We thus provide the first experimental support that individual variation in brain size affects mate choice decisions and conclude that differences in cognitive ability may be an important underlying mechanism behind variation in female mate choice.

Looking for sexual selection in the female brain.

PubMed

Cummings, Molly E

2012-08-19

Female mate choice behaviour has significant evolutionary consequences, yet its mechanistic origins are not fully understood. Recent studies of female sensory systems have made great strides in identifying internal mechanisms governing female preferences. Only recently, however, have we begun to identify the dynamic genomic response associated with mate choice behaviour. Poeciliids provide a powerful comparative system to examine genomic responses governing mate choice and female preference behaviour, given the great range of mating systems: from female mate choice taxa with ornamental courting males to species lacking male ornamentation and exhibiting only male coercion. Furthermore, they exhibit laboratory-tractable preference responses without sexual contact that are decoupled from reproductive state, allowing investigators to isolate mechanisms in the brain without physiological confounds. Early investigations with poeciliid species (Xiphophorus nigrensis and Gambusia affinis) have identified putative candidate genes associated with female preference response and highlight a possible genomic pathway underlying female social interactions with males linked functionally with synaptic plasticity and learning processes. This network is positively correlated with female preference behaviour in the female mate choice species, but appears inhibited in the male coercive species. This behavioural genomics approach provides opportunity to elucidate the fundamental building blocks, and evolutionary dynamics, of sexual selection.

Acoustic communication in insect disease vectors

PubMed Central

Vigoder, Felipe de Mello; Ritchie, Michael Gordon; Gibson, Gabriella; Peixoto, Alexandre Afranio

2013-01-01

Acoustic signalling has been extensively studied in insect species, which has led to a better understanding of sexual communication, sexual selection and modes of speciation. The significance of acoustic signals for a blood-sucking insect was first reported in the XIX century by Christopher Johnston, studying the hearing organs of mosquitoes, but has received relatively little attention in other disease vectors until recently. Acoustic signals are often associated with mating behaviour and sexual selection and changes in signalling can lead to rapid evolutionary divergence and may ultimately contribute to the process of speciation. Songs can also have implications for the success of novel methods of disease control such as determining the mating competitiveness of modified insects used for mass-release control programs. Species-specific sound “signatures” may help identify incipient species within species complexes that may be of epidemiological significance, e.g. of higher vectorial capacity, thereby enabling the application of more focussed control measures to optimise the reduction of pathogen transmission. Although the study of acoustic communication in insect vectors has been relatively limited, this review of research demonstrates their value as models for understanding both the functional and evolutionary significance of acoustic communication in insects. PMID:24473800

Preference for aggressive and sexual stimuli in children with disruptive behavior disorder and normal controls.

PubMed

van Goozen, Stephanie H M; Cohen-Kettenis, Peggy T; Matthys, Walter; van Engeland, Herman

2002-06-01

Children with disruptive behavior disorders (DBD) have poor social skills and show aggressive interaction patterns. There is evidence from prospective studies of an association between early physical abuse, later social information-processing patterns, and aggressive behavior. A pattern of hypervigilance to hostile cues has been found in DBD children, but very few studies have investigated encoding or perceptual preference for specific classes of stimuli. Some DBD children have a suspected history of sexual abuse and a few have themselves been sexually offensive. Our belief that the sexuality of DBD children should be investigated raised the issue of how to go about doing this. A procedure was developed in which we measured the relative preference for sexual and aggressive stimuli in comparison to other stimulus categories, and the data of DBD children were compared with those of normal controls. It was found that DBD children preferred viewing sexual slides and had a lower preference for nonaggressive slides. Furthermore, boys in general preferred viewing aggressive slides, did so for longer, and chose them earlier, whereas the more aggressive DBD children distinguished themselves in selecting aggressive stimuli earlier. The implications of these findings were discussed and it was concluded that sexuality is clearly an important topic to address in aggressive children in general and not only in the abused ones.

Review: The effect of nutrition on timing of pubertal onset and subsequent fertility in the bull.

PubMed

Kenny, D A; Byrne, C J

2018-06-01

The advent of genomic selection has led to increased interest within the cattle breeding industry to market semen from young bulls as early as possible. However, both the quantity and quality of such semen is dictated by the age at which these animals reach puberty. Enhancing early life plane of nutrition of the bull stimulates a complex biochemical interplay involving metabolic and neuroendocrine signalling and culminating in enhanced testicular growth and development and earlier onset of sexual maturation. Recent evidence suggests that an enhanced plane of nutrition leads to an advancement of testicular development in bulls at 18 weeks of age. However, as of yet, much of the neuronal mechanisms regulating these developmental processes remain to be elucidated in the bull. While early life nutrition clearly affects the sexual maturation process in bulls, there is little evidence for latent effects on semen traits post-puberty. Equally the influence of prevailing nutritional status on the fertility of mature bulls is unclear though management practices that result in clinical or even subclinical metabolic disease can undoubtedly impact upon normal sexual function. Dietary supplements enriched with various polyunsaturated fatty acids or fortified with trace elements do not consistently affect reproductive function in the bull, certainly where animals are already adequately nourished. Further insight on how nutrition mediates the biochemical interaction between neuroendocrine and testicular processes will facilitate optimisation of nutritional regimens to optimise sexual maturation and subsequent semen production in bulls.

The Evolution of Sexually Antagonistic Phenotypes

PubMed Central

Perry, Jennifer C.; Rowe, Locke

2015-01-01

Sexual conflict occurs whenever there is sexually antagonistic selection on shared traits. When shared traits result from interactions (e.g., mating rate) and have a different genetic basis in each sex (i.e., interlocus conflict), then sex-specific traits that shift the value of these interaction traits toward the sex-specific optimum will be favored. Male traits can be favored that increase the fitness of their male bearers, but decrease the fitness of interacting females. Likewise, female traits that reduce the costs of interacting with harmful males may simultaneously impose costs on males. If the evolution of these antagonistic traits changes the nature of selection acting on the opposite sex, interesting coevolutionary dynamics will result. Here we examine three current issues in the study of sexually antagonistic interactions: the female side of sexual conflict, the ecological context of sexual conflict, and the strength of evidence for sexually antagonistic coevolution. PMID:26032715

Sexual conflict predicts morphology and behavior in two species of penduline tits

PubMed Central

2010-01-01

Background The evolutionary interests of males and females rarely coincide (sexual conflict), and these conflicting interests influence morphology, behavior and speciation in various organisms. We examined consequences of variation in sexual conflict in two closely-related passerine birds with contrasting breeding systems: the Eurasian penduline tit Remiz pendulinus (EPT) exhibiting a highly polygamous breeding system with sexually antagonistic interests over parental care, and the socially monogamous Cape penduline tit Anthoscopus minutus (CPT). We derived four a priori predictions from sexual conflict theory and tested these using data collected in Central Europe (EPT) and South Africa (CPT). Firstly, we predicted that EPTs exhibit more sexually dimorphic plumage than CPTs due to more intense sexual selection. Secondly, we expected brighter EPT males to provide less care than duller males. Thirdly, since song is a sexually selected trait in many birds, male EPTs were expected to exhibit more complex songs than CPT males. Finally, intense sexual conflict in EPT was expected to lead to low nest attendance as an indication of sexually antagonistic interests, whereas we expected more cooperation between parents in CPT consistent with their socially monogamous breeding system. Results Consistent with our predictions EPTs exhibited greater sexual dimorphism in plumage and more complex song than CPTs, and brighter EPT males provided less care than duller ones. EPT parents attended the nest less frequently and less simultaneously than CPT parents. Conclusions These results are consistent with sexual conflict theory: species in which sexual conflict is more manifested (EPT) exhibited a stronger sexual dimorphism and more elaborated sexually selected traits than species with less intense sexual conflict (CPT). Our results are also consistent with the notion that EPTs attempt to force their partner to work harder as expected under sexual conflict: each member of the breeding pair attempts to shift the costs of care to the other parent. More brightly colored males benefit more from desertion than dull ones, because they are more likely to remate with a new female. Taken together, the comparison between two closely related species with contrasting breeding systems suggest that sexual conflict over care has influenced the evolution of behavior and morphology in penduline tits. PMID:20416066

Sexual conflict predicts morphology and behavior in two species of penduline tits.

PubMed

van Dijk, René E; Pogány, Akos; Komdeur, Jan; Lloyd, Penn; Székely, Tamás

2010-04-23

The evolutionary interests of males and females rarely coincide (sexual conflict), and these conflicting interests influence morphology, behavior and speciation in various organisms. We examined consequences of variation in sexual conflict in two closely-related passerine birds with contrasting breeding systems: the Eurasian penduline tit Remiz pendulinus (EPT) exhibiting a highly polygamous breeding system with sexually antagonistic interests over parental care, and the socially monogamous Cape penduline tit Anthoscopus minutus (CPT). We derived four a priori predictions from sexual conflict theory and tested these using data collected in Central Europe (EPT) and South Africa (CPT). Firstly, we predicted that EPTs exhibit more sexually dimorphic plumage than CPTs due to more intense sexual selection. Secondly, we expected brighter EPT males to provide less care than duller males. Thirdly, since song is a sexually selected trait in many birds, male EPTs were expected to exhibit more complex songs than CPT males. Finally, intense sexual conflict in EPT was expected to lead to low nest attendance as an indication of sexually antagonistic interests, whereas we expected more cooperation between parents in CPT consistent with their socially monogamous breeding system. Consistent with our predictions EPTs exhibited greater sexual dimorphism in plumage and more complex song than CPTs, and brighter EPT males provided less care than duller ones. EPT parents attended the nest less frequently and less simultaneously than CPT parents. These results are consistent with sexual conflict theory: species in which sexual conflict is more manifested (EPT) exhibited a stronger sexual dimorphism and more elaborated sexually selected traits than species with less intense sexual conflict (CPT). Our results are also consistent with the notion that EPTs attempt to force their partner to work harder as expected under sexual conflict: each member of the breeding pair attempts to shift the costs of care to the other parent. More brightly colored males benefit more from desertion than dull ones, because they are more likely to remate with a new female. Taken together, the comparison between two closely related species with contrasting breeding systems suggest that sexual conflict over care has influenced the evolution of behavior and morphology in penduline tits.

Specialization for aggression in sexually dimorphic skeletal morphology in grey wolves (Canis lupus)

PubMed Central

Morris, Jeremy S; Brandt, Ellissa K

2014-01-01

Aggressive behaviour is important in the life history of many animals. In grey wolves (Canis lupus), territory defence through direct competition with conspecifics is severe and often lethal. Thus, performance in aggressive encounters may be under strong selection. Additionally, grey wolves frequently kill large dangerous prey species. Because both sexes actively participate in aggressive activities and prey capture, wolves are expected to exhibit a low level of musculoskeletal sexual dimorphism. However, male wolves more often lead in agonistic encounters with conspecifics and must provision the nursing female during the pup-rearing period of the breeding season. These behaviours may select for males that exhibit a higher degree of morphological adaptation associated with aggression and prey capture performance. To test this prediction, we assessed skeletal sexual dimorphism in three subspecies of grey wolves using functional indices reflecting morphological specialization for aggression. As expected, sexual dimorphism in skeletal shape was limited. However, in two of three subspecies, we found sexually dimorphic traits in the skull, forelimbs and hindlimbs that are consistent with the hypothesis that males are more specialized for aggression. These characters may also be associated with selection for improved prey capture performance by males. Thus, the sexually dimorphic functional traits identified by our analysis may be adaptive in the contexts of both natural and sexual selection. Several of these traits may conflict with locomotor economy, indicating the importance of aggression in the life history of male grey wolves. The presence of functional specialization for aggression in a generally monogamous species indicates that sexual dimorphism in specific musculoskeletal traits may be widespread among mammals. PMID:24810384

Biochemical factors modulating female genital sexual arousal physiology.

PubMed

Traish, Abdulmaged M; Botchevar, Ella; Kim, Noel N

2010-09-01

Female genital sexual arousal responses are complex neurophysiological processes consisting of central and peripheral components that occur following sexual stimulation. The peripheral responses in sexual arousal include genital vasocongestion, engorgement and lubrication resulting from a surge of vaginal and clitoral blood flow. These hemodynamic events are mediated by a host of neurotransmitters and vasoactive agents. To discuss the role of various biochemical factors modulating female genital sexual arousal responses. A comprehensive literature review was conducted using the PubMed database and citations were selected, based on topical relevance, and examined for study methodology and major findings. Data from peer-reviewed publications. Adrenergic as well as non-adrenergic non-cholinergic neurotransmitters play an important role in regulating genital physiological responses by mediating vascular and non-vascular smooth muscle contractility. Vasoactive peptides and neuropeptides also modulate genital sexual responses by regulating vascular and non-vascular smooth muscle cells and epithelial function. The endocrine milieu, particularly sex steroid hormones, is critical in the maintenance of tissue structure and function. Reduced levels of estrogens and androgen are associated with dramatic alterations in genital tissue structure, including the nerve network, as well as the response to physiological modulators. Furthermore, estrogen and androgen deficiency is associated with reduced expression of sex steroid receptors and most importantly with attenuated genital blood flow and lubrication in response to pelvic nerve stimulation. This article provides an integrated framework describing the physiological and molecular basis of various pathophysiological conditions associated with female genital sexual arousal dysfunction. © 2010 International Society for Sexual Medicine.

Sexual selection, genetic conflict, selfish genes, and the atypical patterns of gene expression in spermatogenic cells.

PubMed

Kleene, Kenneth C

2005-01-01

This review proposes that the peculiar patterns of gene expression in spermatogenic cells are the consequence of powerful evolutionary forces known as sexual selection. Sexual selection is generally characterized by intense competition of males for females, an enormous variety of the strategies to maximize male reproductive success, exaggerated male traits at all levels of biological organization, co-evolution of sexual traits in males and females, and conflict between the sexual advantage of the male trait and the reproductive fitness of females and the individual fitness of both sexes. In addition, spermatogenesis is afflicted by selfish genes that promote their transmission to progeny while causing deleterious effects. Sexual selection, selfish genes, and genetic conflict provide compelling explanations for many atypical features of gene expression in spermatogenic cells including the gross overexpression of certain mRNAs, transcripts encoding truncated proteins that cannot carry out basic functions of the proteins encoded by the same genes in somatic cells, the large number of gene families containing paralogous genes encoding spermatogenic cell-specific isoforms, the large number of testis-cancer-associated genes that are expressed only in spermatogenic cells and malignant cells, and the overbearing role of Sertoli cells in regulating the number and quality of spermatozoa.

The middle way of evolution

PubMed Central

Hunt, Tam

2012-01-01

This essay provides a critical review of two recent books on evolution: Richard Dawkins’ The Greatest Show on Earth, and Jerry Coyne’s Why Evolution is True, as well as a critique of mainstream evolutionary theory and of natural selection. I also suggest a generalization of sexual selection theory that acknowledges mind as pervasive in nature. Natural selection, as the primary theory of how biological change occurs, must be carefully framed to avoid the long-standing “tautology problem” and must also be modified to more explicitly include the role of mind in evolution. A propensity approach to natural selection, in which “expected fitness” is utilized rather than “fitness,” can save natural selection from tautology. But to be a productive theory, natural selection theory should be placed alongside sexual selection – which is explicitly agentic/intentional – as a twin force, but also placed alongside purely endogenous factors such as genetic drift. This framing is contrary to the normal convention that often groups all of these factors under the rubric of “natural selection.” I suggest some approaches for improving modern evolutionary theory, including a “generalized sexual selection,” a panpsychist extension of Darwin’s theory of sexual selection that explicitly recognizes the role of mind at all levels of nature and which may play the part of a general theory of evolution better than natural selection theory. PMID:23181154

Divergent sexual selection via male competition: ecology is key.

PubMed

Lackey, A C R; Boughman, J W

2013-08-01

Sexual selection and ecological differences are important drivers of speciation. Much research has focused on female choice, yet the role of male competition in ecological speciation has been understudied. Here, we test how mating habitats impact sexual selection and speciation through male competition. Using limnetic and benthic species of threespine stickleback fish, we find that different mating habitats select differently on male traits through male competition. In mixed habitat with both vegetated and open areas, selection favours two trait combinations of male body size and nuptial colour: large with little colour and small with lots of colour. This matches what we see in reproductively isolated stickleback species, suggesting male competition could promote trait divergence and reproductive isolation. In contrast, when only open habitat exists, selection favours one trait combination, large with lots of colour, which would hinder trait divergence and reproductive isolation. Other behavioural mechanisms in male competition that might promote divergence, such as avoiding aggression with heterospecifics, are insufficient to maintain separate species. This work highlights the importance of mating habitats in male competition for both sexual selection and speciation. © 2013 The Authors. Journal of Evolutionary Biology © 2013 European Society For Evolutionary Biology.

Unconscious Desire: The Affective and Motivational Aspects of Subliminal Sexual Priming.

PubMed

Gillath, Omri; Collins, Tara

2016-01-01

Sexual arousal is thought to be the result of the processing of sexual cues at two levels: conscious and unconscious. Whereas numerous studies have examined the affective and motivational responses to supraliminal (consciously processed) sexual cues, much less is known regarding the responses to subliminal (processed outside of one's awareness) sexual cues. Five studies examined responses to subliminal sexual cues. Studies 1–3 demonstrated increases in adults' positive affect following exposure to subliminal sexual cues compared to control cues. Study 4 demonstrated that the positive affect resulting from exposure to subliminal sexual cues increased motivation to further engage in a neutral task. Study 5 provided evidence suggesting that the affect and motivation found in Studies 1–4 were associated with motivation to engage in sex specifically, rather than a general approach motivation. The implications of these findings for the processing of subliminal sexual cues and for human sexuality are discussed.

Measurement and Design Issues in the Study of Adolescent Sexual Behavior and the Evaluation of Adolescent Sexual Health Behavior Interventions

ERIC Educational Resources Information Center

Young, Michael; Palacios, Rebecca; Penhollow, Tina M.

2012-01-01

To improve the quality of research and commentary concerning adolescent sexuality and evaluation of both comprehensive sexuality education and abstinence education programs, this article aims to help readers (1) select appropriate measures to study adolescent sexual behavior, (2) develop appropriate study designs to evaluate adolescent sexual…

The nature of allometry in an exaggerated trait: The postocular flange in Platyneuromus Weele (Insecta: Megaloptera)

PubMed Central

Ramírez-Ponce, Andrés; Garfias-Lozano, Gabriela; Contreras-Ramos, Atilano

2017-01-01

The origin and function of exaggerated traits exhibited by a great number of species with sexual dimorphism remain largely unexplored. The usual model considered as the evolutionary mechanism for the development of these structures is sexual selection. The nature of growth of the postocular flange (POF) in three species of the dobsonfly genus Platyneuromus (Megaloptera, Corydalidae, Corydalinae) is analyzed to explore sexual size dimorphism and allometric scaling. Results involve positive allometry of POF in males of two species, and negative allometry in males of one species, in general with a female-biased sexual dimorphism. We suggest an ancestral condition of dual incipient ornamentation in Platyneuromus, with a subsequent departure of size and shape of POF in males, triggered by sexual selection. Different sexual selection intensities may explain the parallel or divergent growth of POF within the scheme of dual ornamentation. Empirical behavioral data as well as a phylogenetic framework are necessary to clarify possible causes of phenotypic development, time of origin, and evolution of the POF. PMID:28212437

Differential regulation of msx genes in the development of the gonopodium, an intromittent organ, and of the "sword," a sexually selected trait of swordtail fishes (Xiphophorus).

PubMed

Zauner, Hans; Begemann, Gerrit; Marí-Beffa, Manuel; Meyer, Axel

2003-01-01

The possession of a conspicuous extension of colored ventral rays of the caudal fin in male fish of swordtails (genus Xiphophorus) is a prominent example for a trait that evolved by sexual selection. To understand the evolutionary history of this so-called sword molecularly, it is of interest to unravel the developmental pathways responsible for extended growth of sword rays during development of swordtail males. We isolated two msx genes and showed that they are differentially regulated during sword outgrowth. During sword growth in juvenile males, as well as during testosterone-induced sword development and fin ray regeneration in the sword after amputation, expression of msxC is markedly up-regulated in the sword forming fin rays. In contrast, msxE/1 is not differentially expressed in ventral and dorsal male fin rays, suggesting a link between the development of male secondary sexual characters in fins and up-regulation of msxC expression. In addition, we showed that msx gene expression patterns differ significantly between Xiphophorus and zebrafish. We also included in our study the gonopodium, a testosterone-dependent anal fin modification that serves as a fertilization organ in males of live-bearing fishes. Our finding that increased levels of msxC expression are associated with the testosterone-induced outgrowth of the gonopodium might suggest either that at least parts of the signaling pathways that pattern the evolutionary older gonopodium have been coopted to evolve a sexually selected innovation such as the sword or that increased msxC expression may be inherent to the growth process of long fin rays in general.

Selecting at-risk populations for sexually transmitted disease/HIV intervention studies.

PubMed

Wu, Zunyou; Rotheram-Borus, Mary Jane; Detels, Roger; Li, Li; Guan, Jihui; Liang, Guojun; Yap, Lorraine

2007-12-01

This paper describes one option to select populations for randomized, controlled trials (RCT). We used a popular opinion leader intervention in Fuzhou, China, to: (1) identify population selection criteria; (2) systematically examine the suitability of potential target populations and settings; (3) briefly evaluate risk and stability in the population; and (4) evaluate regional and organizational support among administrators and government officials. After comparing migrant villagers, truck drivers, factory workers, construction workers, and market employees in five regions of China, market employees in Fuzhou were identified as the optimal target population. Markets were the optimal sites for several reasons: (1) the population demonstrated a sufficient base rate of sexually transmitted diseases; (2) the population was stable over time; (3) a sufficient number of sites of manageable sizes were available; (4) stable networks existed; (5) local gatekeepers/stakeholders supported the intervention; (6) there was organizational capacity in the local health department to mount the intervention; (7) the demographic profile was similar across potential sites; and (8) the sites were sufficiently distanced to minimize contamination. Evaluating intervention efficacy in an RCT requires a time-consuming and rigorous process that systematically and routinely documents selection criteria, evaluates multiple populations, sites, and organizations for their appropriateness.

A general population genetic framework for antagonistic selection that accounts for demography and recurrent mutation.

PubMed

Connallon, Tim; Clark, Andrew G

2012-04-01

Antagonistic selection--where alleles at a locus have opposing effects on male and female fitness ("sexual antagonism") or between components of fitness ("antagonistic pleiotropy")--might play an important role in maintaining population genetic variation and in driving phylogenetic and genomic patterns of sexual dimorphism and life-history evolution. While prior theory has thoroughly characterized the conditions necessary for antagonistic balancing selection to operate, we currently know little about the evolutionary interactions between antagonistic selection, recurrent mutation, and genetic drift, which should collectively shape empirical patterns of genetic variation. To fill this void, we developed and analyzed a series of population genetic models that simultaneously incorporate these processes. Our models identify two general properties of antagonistically selected loci. First, antagonistic selection inflates heterozygosity and fitness variance across a broad parameter range--a result that applies to alleles maintained by balancing selection and by recurrent mutation. Second, effective population size and genetic drift profoundly affect the statistical frequency distributions of antagonistically selected alleles. The "efficacy" of antagonistic selection (i.e., its tendency to dominate over genetic drift) is extremely weak relative to classical models, such as directional selection and overdominance. Alleles meeting traditional criteria for strong selection (N(e)s > 1, where N(e) is the effective population size, and s is a selection coefficient for a given sex or fitness component) may nevertheless evolve as if neutral. The effects of mutation and demography may generate population differences in overall levels of antagonistic fitness variation, as well as molecular population genetic signatures of balancing selection.

Sexual selection and population divergence I: The influence of socially flexible cuticular hydrocarbon expression in male field crickets (Teleogryllus oceanicus).

PubMed

Pascoal, Sonia; Mendrok, Magdalena; Mitchell, Christopher; Wilson, Alastair J; Hunt, John; Bailey, Nathan W

2016-01-01

Debates about how coevolution of sexual traits and preferences might promote evolutionary diversification have permeated speciation research for over a century. Recent work demonstrates that the expression of such traits can be sensitive to variation in the social environment. Here, we examined social flexibility in a sexually selected male trait-cuticular hydrocarbon (CHC) profiles-in the field cricket Teleogryllus oceanicus and tested whether population genetic divergence predicts the extent or direction of social flexibility in allopatric populations. We manipulated male crickets' social environments during rearing and then characterized CHC profiles. CHC signatures varied considerably across populations and also in response to the social environment, but our prediction that increased social flexibility would be selected in more recently founded populations exposed to fluctuating demographic environments was unsupported. Furthermore, models examining the influence of drift and selection failed to support a role of sexual selection in driving population divergence in CHC profiles. Variation in social environments might alter the dynamics of sexual selection, but our results align with theoretical predictions that the role social flexibility plays in modulating evolutionary divergence depends critically on whether responses to variation in the social environment are homogeneous across populations, or whether gene by social environment interactions occur. © 2015 The Author(s). Evolution © 2015 The Society for the Study of Evolution.

A multivariate analysis of genetic variation in the advertisement call of the gray treefrog, Hyla versicolor.

PubMed

Welch, Allison M; Smith, Michael J; Gerhardt, H Carl

2014-06-01

Genetic variation in sexual displays is crucial for an evolutionary response to sexual selection, but can be eroded by strong selection. Identifying the magnitude and sources of additive genetic variance underlying sexually selected traits is thus an important issue in evolutionary biology. We conducted a quantitative genetics experiment with gray treefrogs (Hyla versicolor) to investigate genetic variances and covariances among features of the male advertisement call. Two energetically expensive traits showed significant genetic variation: call duration, expressed as number of pulses per call, and call rate, represented by its inverse, call period. These two properties also showed significant genetic covariance, consistent with an energetic constraint to call production. Combining the genetic variance-covariance matrix with previous estimates of directional sexual selection imposed by female preferences predicts a limited increase in call duration but no change in call rate despite significant selection on both traits. In addition to constraints imposed by the genetic covariance structure, an evolutionary response to sexual selection may also be limited by high energetic costs of long-duration calls and by preferences that act most strongly against very short-duration calls. Meanwhile, the persistence of these preferences could be explained by costs of mating with males with especially unattractive calls. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

Reproductive social behavior: cooperative games to replace sexual selection.

PubMed

Roughgarden, Joan; Oishi, Meeko; Akçay, Erol

2006-02-17

Theories about sexual selection can be traced back to Darwin in 1871. He proposed that males fertilize as many females as possible with inexpensive sperm, whereas females, with a limited supply of large eggs, select the genetically highest quality males to endow their offspring with superior capabilities. Since its proposal, problems with this narrative have continued to accumulate, and it is our view that sexual selection theory needs to be replaced. We suggest an approach that relies on the exchange of direct ecological benefits among cooperating animals without reference to genetic benefits. This approach can be expressed mathematically in a branch of game theory that pertains to bargaining and side payments.

Differences in the Selection Bottleneck between Modes of Sexual Transmission Influence the Genetic Composition of the HIV-1 Founder Virus

PubMed Central

Tully, Damien C.; Ogilvie, Colin B.; Batorsky, Rebecca E.; Bean, David J.; Power, Karen A.; Ghebremichael, Musie; Bedard, Hunter E.; Gladden, Adrianne D.; Seese, Aaron M.; Amero, Molly A.; Lane, Kimberly; McGrath, Graham; Bazner, Suzane B.; Tinsley, Jake; Lennon, Niall J.; Henn, Matthew R.; Brumme, Zabrina L.; Norris, Philip J.; Rosenberg, Eric S.; Mayer, Kenneth H.; Jessen, Heiko; Kosakovsky Pond, Sergei L.; Walker, Bruce D.; Altfeld, Marcus; Carlson, Jonathan M.; Allen, Todd M.

2016-01-01

Due to the stringent population bottleneck that occurs during sexual HIV-1 transmission, systemic infection is typically established by a limited number of founder viruses. Elucidation of the precise forces influencing the selection of founder viruses may reveal key vulnerabilities that could aid in the development of a vaccine or other clinical interventions. Here, we utilize deep sequencing data and apply a genetic distance-based method to investigate whether the mode of sexual transmission shapes the nascent founder viral genome. Analysis of 74 acute and early HIV-1 infected subjects revealed that 83% of men who have sex with men (MSM) exhibit a single founder virus, levels similar to those previously observed in heterosexual (HSX) transmission. In a metadata analysis of a total of 354 subjects, including HSX, MSM and injecting drug users (IDU), we also observed no significant differences in the frequency of single founder virus infections between HSX and MSM transmissions. However, comparison of HIV-1 envelope sequences revealed that HSX founder viruses exhibited a greater number of codon sites under positive selection, as well as stronger transmission indices possibly reflective of higher fitness variants. Moreover, specific genetic “signatures” within MSM and HSX founder viruses were identified, with single polymorphisms within gp41 enriched among HSX viruses while more complex patterns, including clustered polymorphisms surrounding the CD4 binding site, were enriched in MSM viruses. While our findings do not support an influence of the mode of sexual transmission on the number of founder viruses, they do demonstrate that there are marked differences in the selection bottleneck that can significantly shape their genetic composition. This study illustrates the complex dynamics of the transmission bottleneck and reveals that distinct genetic bottleneck processes exist dependent upon the mode of HIV-1 transmission. PMID:27163788

Differences in the Selection Bottleneck between Modes of Sexual Transmission Influence the Genetic Composition of the HIV-1 Founder Virus.

PubMed

Tully, Damien C; Ogilvie, Colin B; Batorsky, Rebecca E; Bean, David J; Power, Karen A; Ghebremichael, Musie; Bedard, Hunter E; Gladden, Adrianne D; Seese, Aaron M; Amero, Molly A; Lane, Kimberly; McGrath, Graham; Bazner, Suzane B; Tinsley, Jake; Lennon, Niall J; Henn, Matthew R; Brumme, Zabrina L; Norris, Philip J; Rosenberg, Eric S; Mayer, Kenneth H; Jessen, Heiko; Kosakovsky Pond, Sergei L; Walker, Bruce D; Altfeld, Marcus; Carlson, Jonathan M; Allen, Todd M

2016-05-01

Due to the stringent population bottleneck that occurs during sexual HIV-1 transmission, systemic infection is typically established by a limited number of founder viruses. Elucidation of the precise forces influencing the selection of founder viruses may reveal key vulnerabilities that could aid in the development of a vaccine or other clinical interventions. Here, we utilize deep sequencing data and apply a genetic distance-based method to investigate whether the mode of sexual transmission shapes the nascent founder viral genome. Analysis of 74 acute and early HIV-1 infected subjects revealed that 83% of men who have sex with men (MSM) exhibit a single founder virus, levels similar to those previously observed in heterosexual (HSX) transmission. In a metadata analysis of a total of 354 subjects, including HSX, MSM and injecting drug users (IDU), we also observed no significant differences in the frequency of single founder virus infections between HSX and MSM transmissions. However, comparison of HIV-1 envelope sequences revealed that HSX founder viruses exhibited a greater number of codon sites under positive selection, as well as stronger transmission indices possibly reflective of higher fitness variants. Moreover, specific genetic "signatures" within MSM and HSX founder viruses were identified, with single polymorphisms within gp41 enriched among HSX viruses while more complex patterns, including clustered polymorphisms surrounding the CD4 binding site, were enriched in MSM viruses. While our findings do not support an influence of the mode of sexual transmission on the number of founder viruses, they do demonstrate that there are marked differences in the selection bottleneck that can significantly shape their genetic composition. This study illustrates the complex dynamics of the transmission bottleneck and reveals that distinct genetic bottleneck processes exist dependent upon the mode of HIV-1 transmission.

Artificial selection reveals sex differences in the genetic basis of sexual attractiveness.

PubMed

Gosden, Thomas P; Reddiex, Adam J; Chenoweth, Stephen F

2018-05-07

Mutual mate choice occurs when males and females base mating decisions on shared traits. Despite increased awareness, the extent to which mutual choice drives phenotypic change remains poorly understood. When preferences in both sexes target the same traits, it is unclear how evolution will proceed and whether responses to sexual selection from male choice will match or oppose responses to female choice. Answering this question is challenging, as it requires understanding, genetic relationships between the traits targeted by choice, mating success, and, ultimately, fitness for both sexes. Addressing this, we applied artificial selection to the cuticular hydrocarbons of the fly Drosophila serrata that are targeted by mutual choice and tracked evolutionary changes in males and females alongside changes in mating success. After 10 generations, significant trait evolution occurred in both sexes, but intriguingly there were major sex differences in the associated fitness consequences. Sexually selected trait evolution in males led to a genetically based increase in male mating success. By contrast, although trait evolution also occurred in females, there was no change in mating success. Our results suggest that phenotypic sexual selection on females from male choice is environmentally, rather than genetically, generated. Thus, compared with female choice, male choice is at best a weak driver of signal trait evolution in this species. Instead, the evolution of apparent female ornamentation seems more likely due to a correlated response to sexual selection on males and possibly other forms of natural selection.

Sexual Identity, Sex of Sexual Contacts, and Health-Related Behaviors among Students in Grades 9-12--United States and Selected Sites, 2015. Morbidity and Mortality Weekly Report. Surveillance Summaries. Volume 65, Number 9

ERIC Educational Resources Information Center

Kann, Laura; Olsen, Emily O'Malley; McManus, Tim; Harris, William A.; Shanklin, Shari L.; Flint, Katherine H.; Queen, Barbara; Lowry, Richard; Chyen, David; Whittle, Lisa; Thornton, Jemekia; Lim, Connie; Yamakawa, Yoshimi; Brener, Nancy; Zaza, Stephanie

2016-01-01

Problem: Sexual identity and sex of sexual contacts can both be used to identify sexual minority youth. Significant health disparities exist between sexual minority and nonsexual minority youth. However, not enough is known about health-related behaviors that contribute to negative health outcomes among sexual minority youth and how the prevalence…

The shadow of silence on the sexual rights of married Iranian women.

PubMed

Janghorban, Roksana; Latifnejad Roudsari, Robab; Taghipour, Ali; Abbasi, Mahmoud; Lottes, Ilsa

2015-01-01

There has been a recent shift in the field of sexual health, representing a move away from biomedical concerns to sexual rights frameworks. However, few studies on sexuality are based on a rights framework. The unspoken nature of sexuality in Iranian culture has led to a lack of national studies on the topic. The objective of this study was to explore the perceptions and experiences of married Iranian women on sexual rights in their sexual relationships. In this grounded theory study, 37 participants (25 married women, 5 husbands, and 7 midwives) were selected. Data were collected through in-depth interviews and analyzed through open, axial, and selective coding using MAXQDA software version 2007. The analysis revealed the core category of "sexual interaction in the shadow of silence." The interrelated categories subsumed under the core category included adopting a strategy of silence, trying to negotiate sex, seeking help, and sexual adjustment. The silence originating from women's interactions with their families and society, from girlhood to womanhood, was identified as the core concept in Iranian women's experiences of sexual rights. A focus on husbands' roles seems salient because they can direct or alter some learned feminine roles, especially silence regarding sexual matters, which then affects the realization of women's sexual rights.

The Shadow of Silence on the Sexual Rights of Married Iranian Women

PubMed Central

Lottes, Ilsa

2015-01-01

There has been a recent shift in the field of sexual health, representing a move away from biomedical concerns to sexual rights frameworks. However, few studies on sexuality are based on a rights framework. The unspoken nature of sexuality in Iranian culture has led to a lack of national studies on the topic. The objective of this study was to explore the perceptions and experiences of married Iranian women on sexual rights in their sexual relationships. In this grounded theory study, 37 participants (25 married women, 5 husbands, and 7 midwives) were selected. Data were collected through in-depth interviews and analyzed through open, axial, and selective coding using MAXQDA software version 2007. The analysis revealed the core category of “sexual interaction in the shadow of silence.” The interrelated categories subsumed under the core category included adopting a strategy of silence, trying to negotiate sex, seeking help, and sexual adjustment. The silence originating from women's interactions with their families and society, from girlhood to womanhood, was identified as the core concept in Iranian women's experiences of sexual rights. A focus on husbands' roles seems salient because they can direct or alter some learned feminine roles, especially silence regarding sexual matters, which then affects the realization of women's sexual rights. PMID:25705669

Mosquito biology. Evolution of sexual traits influencing vectorial capacity in anopheline mosquitoes.

PubMed

Mitchell, Sara N; Kakani, Evdoxia G; South, Adam; Howell, Paul I; Waterhouse, Robert M; Catteruccia, Flaminia

2015-02-27

The availability of genome sequences from 16 anopheline species provides unprecedented opportunities to study the evolution of reproductive traits relevant for malaria transmission. In Anopheles gambiae, a likely candidate for sexual selection is male 20-hydroxyecdysone (20E). Sexual transfer of this steroid hormone as part of a mating plug dramatically changes female physiological processes intimately tied to vectorial capacity. By combining phenotypic studies with ancestral state reconstructions and phylogenetic analyses, we show that mating plug transfer and male 20E synthesis are both derived characters that have coevolved in anophelines, driving the adaptation of a female 20E-interacting protein that promotes oogenesis via mechanisms also favoring Plasmodium survival. Our data reveal coevolutionary dynamics of reproductive traits between the sexes likely to have shaped the ability of anophelines to transmit malaria. Copyright © 2015, American Association for the Advancement of Science.

Initial orienting towards sexually relevant stimuli: preliminary evidence from eye movement measures.

PubMed

Fromberger, Peter; Jordan, Kirsten; von Herder, Jakob; Steinkrauss, Henrike; Nemetschek, Rebekka; Stolpmann, Georg; Müller, Jürgen Leo

2012-08-01

It has been proposed that sexual stimuli will be processed in a comparable manner to other evolutionarily meaningful stimuli (such as spiders or snakes) and therefore elicit an attentional bias and more attentional engagement (Spiering and Everaerd, In E. Janssen (Ed.), The psychophysiology of sex (pp. 166-183). Bloomington: Indiana University Press, 2007). To investigate early and late attentional processes while looking at sexual stimuli, heterosexual men (n = 12) viewed pairs of sexually preferred (images of women) and sexually non-preferred images (images of girls, boys or men), while eye movements were measured. Early attentional processing (initial orienting) was assessed by the number of first fixations and late attentional processing (maintenance of attention) was assessed by relative fixation time. Results showed that relative fixation time was significantly longer for sexually preferred stimuli than for sexually non-preferred stimuli. Furthermore, the first fixation was more often directed towards the preferred sexual stimulus, when simultaneously presented with a non-sexually preferred stimulus. Thus, the current study showed for the first time an attentional bias to sexually relevant stimuli when presented simultaneously with sexually irrelevant pictures. This finding, along with the discovery that heterosexual men maintained their attention to sexually relevant stimuli, highlights the importance of investigating early and late attentional processes while viewing sexual stimuli. Furthermore, the current study showed that sexually relevant stimuli are favored by the human attentional system.

The contrasting role of male relatedness in different mechanisms of sexual selection in red junglefowl

PubMed Central

Tan, Cedric Kai Wei; Doyle, Philippa; Bagshaw, Emma; Richardson, David S.; Wigby, Stuart; Pizzari, Tommaso

2017-01-01

In structured populations, competition for reproductive opportunities should be relaxed among related males. The few tests of this prediction often neglect the fact that sexual selection acts through multiple mechanisms, both before and after mating. We performed experiments to study the role of within‐group male relatedness across pre‐ and postcopulatory mechanisms of sexual selection in social groups of red junglefowl, Gallus gallus, in which two related males and one unrelated male competed over females unrelated to all the males. We confirm theoretical expectations that, after controlling for male social status, competition over mating was reduced among related males. However, this effect was contrasted by other sexual selection mechanisms. First, females biased male mating in favor of the unrelated male, and might also favor his inseminations after mating. Second, males invested more—rather than fewer—sperm in postcopulatory competition with relatives. A number of factors may contribute to explain this counterintuitive pattern of sperm allocation, including trade‐offs between male investment in pre‐ versus postcopulatory competition, differences in the relative relatedness of pre‐ versus postcopulatory competitors, and female bias in sperm utilization in response to male relatedness. Collectively, these results reveal that within‐group male relatedness may have contrasting effects in different mechanisms of sexual selection. PMID:27925168

Brain size evolution in pipefishes and seahorses: the role of feeding ecology, life history and sexual selection.

PubMed

Tsuboi, M; Lim, A C O; Ooi, B L; Yip, M Y; Chong, V C; Ahnesjö, I; Kolm, N

2017-01-01

Brain size varies greatly at all taxonomic levels. Feeding ecology, life history and sexual selection have been proposed as key components in generating contemporary diversity in brain size across vertebrates. Analyses of brain size evolution have, however, been limited to lineages where males predominantly compete for mating and females choose mates. Here, we present the first original data set of brain sizes in pipefishes and seahorses (Syngnathidae) a group in which intense female mating competition occurs in many species. After controlling for the effect of shared ancestry and overall body size, brain size was positively correlated with relative snout length. Moreover, we found that females, on average, had 4.3% heavier brains than males and that polyandrous species demonstrated more pronounced (11.7%) female-biased brain size dimorphism. Our results suggest that adaptations for feeding on mobile prey items and sexual selection in females are important factors in brain size evolution of pipefishes and seahorses. Most importantly, our study supports the idea that sexual selection plays a major role in brain size evolution, regardless of on which sex sexual selection acts stronger. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

Intra-sexual selection in cooperative mammals and birds: why are females not bigger and better armed?

PubMed

Young, Andrew J; Bennett, Nigel C

2013-01-01

In cooperatively breeding mammals and birds, intra-sexual reproductive competition among females may often render variance in reproductive success higher among females than males, leading to the prediction that intra-sexual selection in such species may have yielded the differential exaggeration of competitive traits among females. However, evidence to date suggests that female-biased reproductive variance in such species is rarely accompanied by female-biased sexual dimorphisms. We illustrate the problem with data from wild Damaraland mole-rat, Fukomys damarensis, societies: the variance in lifetime reproductive success among females appears to be higher than that among males, yet males grow faster, are much heavier as adults and sport larger skulls and incisors (the weapons used for fighting) for their body lengths than females, suggesting that intra-sexual selection has nevertheless acted more strongly on the competitive traits of males. We then consider potentially general mechanisms that could explain these disparities by tempering the relative intensity of selection for competitive trait exaggeration among females in cooperative breeders. Key among these may be interactions with kin selection that could nevertheless render the variance in inclusive fitness lower among females than males, and fundamental aspects of the reproductive biology of females that may leave reproductive conflict among females more readily resolved without overt physical contests.

Selection on an antagonistic behavioral trait can drive rapid genital coevolution in the burying beetle, Nicrophorus vespilloides.

PubMed

Hopwood, Paul E; Head, Megan L; Jordan, Eleanor J; Carter, Mauricio J; Davey, Emma; Moore, Allen J; Royle, Nick J

2016-06-01

Male and female genital morphology varies widely across many taxa, and even among populations. Disentangling potential sources of selection on genital morphology is problematic because each sex is predicted to respond to adaptations in the other due to reproductive conflicts of interest. To test how variation in this sexual conflict trait relates to variation in genital morphology we used our previously developed artificial selection lines for high and low repeated mating rates. We selected for high and low repeated mating rates using monogamous pairings to eliminate contemporaneous female choice and male-male competition. Male and female genital shape responded rapidly to selection on repeated mating rate. High and low mating rate lines diverged from control lines after only 10 generations of selection. We also detected significant patterns of male and female genital shape coevolution among selection regimes. We argue that because our selection lines differ in sexual conflict, these results support the hypothesis that sexually antagonistic coevolution can drive the rapid divergence of genital morphology. The greatest divergence in morphology corresponded with lines in which the resolution of sexual conflict over mating rate was biased in favor of male interests. © 2016 The Author(s). Evolution published by Wiley Periodicals, Inc. on behalf of The Society for the Study of Evolution.

Elimination of a genetic correlation between the sexes via artificial correlational selection.

PubMed

Delph, Lynda F; Steven, Janet C; Anderson, Ingrid A; Herlihy, Christopher R; Brodie, Edmund D

2011-10-01

Genetic correlations between the sexes can constrain the evolution of sexual dimorphism and be difficult to alter, because traits common to both sexes share the same genetic underpinnings. We tested whether artificial correlational selection favoring specific combinations of male and female traits within families could change the strength of a very high between-sex genetic correlation for flower size in the dioecious plant Silene latifolia. This novel selection dramatically reduced the correlation in two of three selection lines in fewer than five generations. Subsequent selection only on females in a line characterized by a lower between-sex genetic correlation led to a significantly lower correlated response in males, confirming the potential evolutionary impact of the reduced correlation. Although between-sex genetic correlations can potentially constrain the evolution of sexual dimorphism, our findings reveal that these constraints come not from a simple conflict between an inflexible genetic architecture and a pattern of selection working in opposition to it, but rather a complex relationship between a changeable correlation and a form of selection that promotes it. In other words, the form of selection on males and females that leads to sexual dimorphism may also promote the genetic phenomenon that limits sexual dimorphism. © 2011 The Author(s). Evolution© 2011 The Society for the Study of Evolution.

"Adopting self-sacrifice": how Iranian women cope with the sexual problems during the menopausal transition? An exploratory qualitative study.

PubMed

Bahri, Narjes; Latifnejad Roudsari, Robab; Azimi Hashemi, Mozhgan

2017-09-01

In the menopausal transition sexual problems are an important issue and one of the most frequently presented health concerns of women attending menopause clinics. This study aimed to explore the ways of managing sexual dysfunctions during the menopausal transition among Iranian women. This exploratory qualitative study was conducted in Iran, from May 2013 to April 2015. Twenty-one women in three stages of menopausal transition, aged 42-55 years old, were purposively selected from urban health centers in Mashhad and Gonabad, Iran. Semi-structured in depth interviews were conducted for data collection until data saturation was achieved. All interviews were recorded electronically and transcribed verbatim. Conventional content analysis was used for data analysis using Granehiem and Lundman (2004) recommended method. MAXQDA 2007 software was used for organizing data and managing the process of analysis. Data analysis demonstrated one overarching theme entitled "Adopting self-sacrifice" consisting of three categories and seven sub-categories. Major categories included: (1) Confronting decline of libido with two subcategories of women's libido decline and inability to fulfill husbands' sexual needs, (2) Seeking strategies for coping with two subcategories of looking for experiences of peer menopausal women and choosing how to interact with the husband and (3) Achieving problem solving strategies with three sub-categories of obedience in sexual relationships (Tamkin), employing affection based on religious advice, and giving up own right to reach mutual understanding. The major finding of this study was "Adopting self-sacrifice" in the process of managing sexual dysfunctions during the menopausal transition. The reason for choosing this passive approach by the majority of women has deep roots in their cultural and traditional beliefs.

Putting sex education in its place.

PubMed

Cassell, C

1981-04-01

In order to help reduce fears and anxieties regarding the influence of sex education in a public school setting, school and community sexuality educators need to better articulate the difference between formal and structured sex education and non-formal, informal and incidental sex learning. Sex education is only 1 aspect of the sexual learning process. 2 main points have to be clarified for parents and the general public to set the stage for a new way to view the school and community involvement in the sexual learning process: the schools' sexuality education courses constitute only a small portion of the sexual learning process; and sexual learning is not an event for youth only, but a process spanning life. Sex education (the process) connotates an academic setting with a specific curricula taught by a trained instructor, but sexual learning relates to environmental, non-formal incidental learning from a multitude of sources. Studies indicate that teenagers receive about 90% of their contraceptive and sexuality informaation from peers and mass media and that these sources of information are becoming their preferred sources of sex education. What is needed is a way to address and improve the conditions of sexual learning in the community. As home is the ideal environment for primary and positive sexual learning, parents need support in their role as sex educators. Classroom sexuality education curricula in all school settings have a solid place in the process of sexual learning.

Sexual Assault: Better Resource Management Needed to Improve Prevention and Response in the Army National Guard and Army Reserve

DTIC Science & Technology

2017-02-01

The Selected Reserve consists of units and individuals designated as so essential to initial wartime missions that they have priority over all... designed to allow sexual assault victims to confidentially disclose an alleged sexual assault to selected individuals...decisions fall within their designated authorities, we found that the National Guard’s and Army Reserve’s current approaches to staffing pose several

Intraspecific eye color variability in birds and mammals: a recent evolutionary event exclusive to humans and domestic animals.

PubMed

Negro, Juan J; Carmen Blázquez, M; Galván, Ismael

2017-01-01

Human populations and breeds of domestic animals are composed of individuals with a multiplicity of eye (= iris) colorations. Some wild birds and mammals may have intraspecific eye color variability, but this variation seems to be due to the developmental stage of the individual, its breeding status, and/or sexual dimorphism. In other words, eye colour tends to be a species-specific trait in wild animals, and the exceptions are species in which individuals of the same age group or gender all develop the same eye colour. Domestic animals, by definition, include bird and mammal species artificially selected by humans in the last few thousand years. Humans themselves may have acquired a diverse palette of eye colors, likewise in recent evolutionary time, in the Mesolithic or in the Upper Paleolithic. We posit two previously unrecognized hypotheses regarding eye color variation: 1) eye coloration in wild animals of every species tends to be a fixed trait. 2) Humans and domestic animal populations, on the contrary, have eyes of multiple colors. Sexual selection has been invoked for eye color variation in humans, but this selection mode does not easily apply in domestic animals, where matings are controlled by the human breeder. Eye coloration is polygenic in humans. We wish to investigate the genetics of eye color in other animals, as well as the ecological correlates. Investigating the origin and function of eye colors will shed light on the reason why some species may have either light-colored irises (e.g., white, yellow or light blue) or dark ones (dark red, brown or black). The causes behind the vast array of eye colors across taxa have never been thoroughly investigated, but it may well be that all Darwinian selection processes are at work: sexual selection in humans, artificial selection for domestic animals, and natural selection (mainly) for wild animals.

A General Population Genetic Framework for Antagonistic Selection That Accounts for Demography and Recurrent Mutation

PubMed Central

Connallon, Tim; Clark, Andrew G.

2012-01-01

Antagonistic selection—where alleles at a locus have opposing effects on male and female fitness (“sexual antagonism”) or between components of fitness (“antagonistic pleiotropy”)—might play an important role in maintaining population genetic variation and in driving phylogenetic and genomic patterns of sexual dimorphism and life-history evolution. While prior theory has thoroughly characterized the conditions necessary for antagonistic balancing selection to operate, we currently know little about the evolutionary interactions between antagonistic selection, recurrent mutation, and genetic drift, which should collectively shape empirical patterns of genetic variation. To fill this void, we developed and analyzed a series of population genetic models that simultaneously incorporate these processes. Our models identify two general properties of antagonistically selected loci. First, antagonistic selection inflates heterozygosity and fitness variance across a broad parameter range—a result that applies to alleles maintained by balancing selection and by recurrent mutation. Second, effective population size and genetic drift profoundly affect the statistical frequency distributions of antagonistically selected alleles. The “efficacy” of antagonistic selection (i.e., its tendency to dominate over genetic drift) is extremely weak relative to classical models, such as directional selection and overdominance. Alleles meeting traditional criteria for strong selection (Nes >> 1, where Ne is the effective population size, and s is a selection coefficient for a given sex or fitness component) may nevertheless evolve as if neutral. The effects of mutation and demography may generate population differences in overall levels of antagonistic fitness variation, as well as molecular population genetic signatures of balancing selection. PMID:22298707

Convergent evolution of sexual shape dimorphism in Diptera.

PubMed

Bonduriansky, Russell

2006-05-01

Several patterns of sexual shape dimorphism, such as male body elongation, eye stalks, or extensions of the exoskeleton, have evolved repeatedly in the true flies (Diptera). Although these dimorphisms may have evolved in response to sexual selection on male body shape, conserved genetic factors may have contributed to this convergent evolution, resulting in stronger phenotypic convergence than might be expected from functional requirements alone. I compared phenotypic variation in body shape in two distantly related species exhibiting sexually dimorphic body elongation: Prochyliza xanthostoma (Piophilidae) and Telostylinus angusticollis (Neriidae). Although sexual selection appears to act differently on male body shape in these species, they exhibited strikingly similar patterns of sexual dimorphism. Likewise, patterns of within-sex shape variation were similar in the two species, particularly in males: relative elongation of the male head capsule, antenna, and legs was associated with reduced head capsule width and wing length, but was nearly independent of variation in thorax length. However, the two species presented contrasting patterns of static allometry: male sexual traits exhibited elevated allometric slopes in T. angusticollis, but not in P. xanthostoma. These results suggest that a shared pattern of covariation among traits may have channeled the evolution of sexually dimorphic body elongation in these species. Nonetheless, static allometries may have been shaped by species-specific selection pressures or genetic architectures. Copyright 2006 Wiley-Liss, Inc.

Sexual Attraction and Religious Therapists: Survey Findings and Implications.

ERIC Educational Resources Information Center

Case, Paul W.; McMinn, Mark R.; Meek, Katheryn Rhoads

1997-01-01

Christian therapists were surveyed concerning beliefs and behaviors regarding sexual attraction and sexual expression toward their clients (N=500). Responses are compared with those from a similar survey of 456 psychologists selected without regard to religious values. Religious factors that may increase the stigma of admitting sexual attraction…

Women with Intellectual Disabilities Talk about Their Perceptions of Sex

ERIC Educational Resources Information Center

Bernert, D. J.; Ogletree, R. J.

2013-01-01

Background: Sexuality is learned through sexual socialisation that women with intellectual disabilities (IDs) understand and express. Rules of sexual engagement for these women can include barriers for their socialisation, intimate partner selection, and sexual expression. These rules can become more limiting when coupled with rules of femininity…

Public Opinion toward Sexuality Education: Findings among One South Florida County

ERIC Educational Resources Information Center

Howard-Barr, Elissa; Moore, Michele Johnson; Weiss, Josie A.; Jobli, Edessa

2011-01-01

As part of a community plan to implement abstinence-based sexuality education, this study assessed opinions toward sexuality education among residents. Respondents (N = 1,090) were selected by random digit dialing. The survey, adopted from previous national studies, assessed attitudes towards sexuality education. Chi-square tests of significance…

Choosing "Something Else" as a Sexual Identity: Evaluating Response Options on the National Health Interview Survey.

PubMed

Eliason, Michele J; Streed, Carl G

2017-10-01

Researchers struggle to find effective ways to measure sexual and gender identities to determine whether there are health differences among subsets of the LGBTQ+ population. This study examines responses on the National Health Interview Survey (NHIS) sexual identity questions among 277 LGBTQ+ healthcare providers. Eighteen percent indicated that their sexual identity was "something else" on the first question, and 57% of those also selected "something else" on the second question. Half of the genderqueer/gender variant participants and 100% of transgender-identified participants selected "something else" as their sexual identity. The NHIS question does not allow all respondents in LGBTQ+ populations to be categorized, thus we are potentially missing vital health disparity information about subsets of the LGBTQ+ population.

Sex-specific selection under environmental stress in seed beetles.

PubMed

Martinossi-Allibert, I; Arnqvist, G; Berger, D

2017-01-01

Sexual selection can increase rates of adaptation by imposing strong selection in males, thereby allowing efficient purging of the mutation load on population fitness at a low demographic cost. Indeed, sexual selection tends to be male-biased throughout the animal kingdom, but little empirical work has explored the ecological sensitivity of this sex difference. In this study, we generated theoretical predictions of sex-specific strengths of selection, environmental sensitivities and genotype-by-environment interactions and tested them in seed beetles by manipulating either larval host plant or rearing temperature. Using fourteen isofemale lines, we measured sex-specific reductions in fitness components, genotype-by-environment interactions and the strength of selection (variance in fitness) in the juvenile and adult stage. As predicted, variance in fitness increased with stress, was consistently greater in males than females for adult reproductive success (implying strong sexual selection), but was similar in the sexes in terms of juvenile survival across all levels of stress. Although genetic variance in fitness increased in magnitude under severe stress, heritability decreased and particularly so in males. Moreover, genotype-by-environment interactions for fitness were common but specific to the type of stress, sex and life stage, suggesting that new environments may change the relative alignment and strength of selection in males and females. Our study thus exemplifies how environmental stress can influence the relative forces of natural and sexual selection, as well as concomitant changes in genetic variance in fitness, which are predicted to have consequences for rates of adaptation in sexual populations. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

EVOLUTION, PHYLOGENY, SEXUAL DIMORPHISM AND MATING SYSTEM IN THE GRACKLES (QUISCALUS SPP.: ICTERINAE).

PubMed

Björklund, Mats

1991-05-01

According to theory, two consequences of sexual selection are sexual dimorphism in size and secondary sexual characteristics, due to either intra- or intersexual selection. In this paper I suggest three criteria for the test of an evolutionary hypothesis involving quantitative morphological characters. First, the postulated change must be shown to have occurred in evolutionary time. Second, this change must be positively correlated with a change in the proposed selective agent. Third, given two taxa with different degrees of sexual size dimorphism and different mating system, the possible influence of drift must be rejected. If the hypothesis is not rejected by these three criteria, then we still have no proof of causality, but we can at least be more confident about its plausibility. This is applied to the particular hypothesis that sexual dimorphism in the Boat-tailed and Great-tailed grackles (Quiscalus spp; Icterinae; Aves) is caused by the highly polygynous mating system in these species. In relation to an outgroup, both species have increased disproportionately in male tarsus and tail size, creating an increased sexual dimorphism. This has cooccurred with the evolution of their particular mating system. However, the variance among species in male tarsus size can be accounted for by drift, and need not be a result of selection for increased size. In contrast, the variance among species in male tail size was much larger than expected under a null model of drift, indicating directional selection for long tails. The variance in female tail size was not larger than expected by drift, whereas the variance in female tarsus size was in fact lower than expected by drift, indicating stabilizing selection. The data are consistent with the hypothesis with regard to tail size, but not with regard to body size. © 1991 The Society for the Study of Evolution.

Independent evolution of the sexes promotes amphibian diversification.

PubMed

De Lisle, Stephen P; Rowe, Locke

2015-03-22

Classic ecological theory predicts that the evolution of sexual dimorphism constrains diversification by limiting morphospace available for speciation. Alternatively, sexual selection may lead to the evolution of reproductive isolation and increased diversification. We test contrasting predictions of these hypotheses by examining the relationship between sexual dimorphism and diversification in amphibians. Our analysis shows that the evolution of sexual size dimorphism (SSD) is associated with increased diversification and speciation, contrary to the ecological theory. Further, this result is unlikely to be explained by traditional sexual selection models because variation in amphibian SSD is unlikely to be driven entirely by sexual selection. We suggest that relaxing a central assumption of classic ecological models-that the sexes share a common adaptive landscape-leads to the alternative hypothesis that independent evolution of the sexes may promote diversification. Once the constraints of sexual conflict are relaxed, the sexes can explore morphospace that would otherwise be inaccessible. Consistent with this novel hypothesis, the evolution of SSD in amphibians is associated with reduced current extinction threat status, and an historical reduction in extinction rate. Our work reconciles conflicting predictions from ecological and evolutionary theory and illustrates that the ability of the sexes to evolve independently is associated with a spectacular vertebrate radiation. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Specialization for aggression in sexually dimorphic skeletal morphology in grey wolves (Canis lupus).

PubMed

Morris, Jeremy S; Brandt, Ellissa K

2014-07-01

Aggressive behaviour is important in the life history of many animals. In grey wolves (Canis lupus), territory defence through direct competition with conspecifics is severe and often lethal. Thus, performance in aggressive encounters may be under strong selection. Additionally, grey wolves frequently kill large dangerous prey species. Because both sexes actively participate in aggressive activities and prey capture, wolves are expected to exhibit a low level of musculoskeletal sexual dimorphism. However, male wolves more often lead in agonistic encounters with conspecifics and must provision the nursing female during the pup-rearing period of the breeding season. These behaviours may select for males that exhibit a higher degree of morphological adaptation associated with aggression and prey capture performance. To test this prediction, we assessed skeletal sexual dimorphism in three subspecies of grey wolves using functional indices reflecting morphological specialization for aggression. As expected, sexual dimorphism in skeletal shape was limited. However, in two of three subspecies, we found sexually dimorphic traits in the skull, forelimbs and hindlimbs that are consistent with the hypothesis that males are more specialized for aggression. These characters may also be associated with selection for improved prey capture performance by males. Thus, the sexually dimorphic functional traits identified by our analysis may be adaptive in the contexts of both natural and sexual selection. Several of these traits may conflict with locomotor economy, indicating the importance of aggression in the life history of male grey wolves. The presence of functional specialization for aggression in a generally monogamous species indicates that sexual dimorphism in specific musculoskeletal traits may be widespread among mammals. © 2014 Anatomical Society.

Intraspecific divergence in sperm morphology of the green sea urchin, Strongylocentrotus droebachiensis: implications for selection in broadcast spawners

PubMed Central

2008-01-01

Background Sperm morphology can be highly variable among species, but less is known about patterns of population differentiation within species. Most studies of sperm morphometric variation are done in species with internal fertilization, where sexual selection can be mediated by complex mating behavior and the environment of the female reproductive tract. Far less is known about patterns of sperm evolution in broadcast spawners, where reproductive dynamics are largely carried out at the gametic level. We investigated variation in sperm morphology of a broadcast spawner, the green sea urchin (Strongylocentrotus droebachiensis), within and among spawnings of an individual, among individuals within a population, and among populations. We also examined population-level variation between two reproductive seasons for one population. We then compared among-population quantitative genetic divergence (QST) for sperm characters to divergence at neutral microsatellite markers (FST). Results All sperm traits except total length showed strong patterns of high diversity among populations, as did overall sperm morphology quantified using multivariate analysis. We also found significant differences in almost all traits among individuals in all populations. Head length, axoneme length, and total length had high within-male repeatability across multiple spawnings. Only sperm head width had significant within-population variation across two reproductive seasons. We found signatures of directional selection on head length and head width, with strong selection possibly acting on head length between the Pacific and West Atlantic populations. We also discuss the strengths and limitations of the QST-FST comparison. Conclusion Sperm morphology in S. droebachiensis is highly variable, both among populations and among individuals within populations, and has low variation within an individual across multiple spawnings. Selective pressures acting among populations may differ from those acting within, with directional selection implicated in driving divergence among populations and balancing selection as a possible mechanism for producing variability among males. Sexual selection in broadcast spawners may be mediated by different processes from those acting on internal fertilizers. Selective divergence in sperm head length among populations is associated with ecological differences among populations that may play a large role in mediating sexual selection in this broadcast spawner. PMID:18851755

The genomic signature of sexual selection in the genetic diversity of the sex chromosomes and autosomes.

PubMed

Corl, Ammon; Ellegren, Hans

2012-07-01

Genomic levels of variation can help reveal the selective and demographic forces that have affected a species during its history. The relative amount of genetic diversity observed on the sex chromosomes as compared to the autosomes is predicted to differ among monogamous and polygynous species. Many species show departures from the expectation for monogamy, but it can be difficult to conclude that this pattern results from variation in mating system because forces other than sexual selection can act upon sex chromosome genetic diversity. As a critical test of the role of mating system, we compared levels of genetic diversity on the Z chromosome and autosomes of phylogenetically independent pairs of shorebirds that differed in their mating systems. We found general support for sexual selection shaping sex chromosome diversity because most polygynous species showed relatively reduced genetic variation on their Z chromosomes as compared to monogamous species. Differences in levels of genetic diversity between the sex chromosomes and autosomes may therefore contribute to understanding the long-term history of sexual selection experienced by a species. © 2012 The Author(s).

Networking Activities and Perceptions of HIV Risk Among Male Migrant Market Vendors in China

PubMed Central

Wang, Wenqing; Muessig, Kathryn E.; Li, Mingqiang; Zhang, Yingxia

2013-01-01

HIV research among internal migrants in China has not fully explored the contexts and perceptions of “risk”. In 2011, urban markets in Liuzhou, China were mapped, and sixty male vendors, age 22 to 56, were selected for in-depth interviews on migration, social and family life, and perceptions and practices of sexual risk behavior. Participants were evenly divided among higher income shop and small stall vendors. All men were sexually active. Only the shop vendors reported non-marital sexual partners, including concurrent partners (n=15), commercial partners (n=10), and other sexual relationships (n=11). Shop vendors engaged in networking activities that facilitated commercial and non-commercial high-risk sex. Perceptions of HIV risk from commercial sex led some men to doubt the protective ability of condoms and rely on local (unproven) self-protection techniques. Networking activities played a role in high-risk sex and shaping migrants' risk perceptions and health practices. The networks created through these processes could also be used to facilitate health promotion activities. PMID:23572155

Public information influences sperm transfer to females in sailfin molly males.

PubMed

Nöbel, Sabine; Witte, Klaudia

2013-01-01

In animals, including humans, the social environment can serve as a public information network in which individuals can gather public information about the quality of potential mates by observing conspecifics during sexual interactions. The observing individual itself is also a part of this information network. When recognized by the observed conspecifics as an audience, his/her presence could influence the sexual interaction between those individuals, because the observer might be considered as a potential mate or competitor. One of the most challenging questions in sexual selection to date is how the use of public information in the context of mate choice is linked to the fitness of individuals. Here, we could show that public information influences mate-choice behaviour in sailfin molly males, Poecilia latipinna, and influences the amount of sperm males transfer to a female partner. In the presence of an audience male, males spent less time with the previously preferred, larger of two females and significantly more time with the previously non-preferred, smaller female. When males could physically interact with a female and were faced with an audience male, three audience females or no audience, males transferred significantly more sperm to a female partner in the presence of an audience male than with female audience or no audience and spent less time courting his female partner. This is the first study showing that public information use turns into fitness investment, which is the crucial factor to understand the role of public information in the dynamic processes in sexual selection.

A gender- and sexual orientation-dependent spatial attentional effect of invisible images.

PubMed

Jiang, Yi; Costello, Patricia; Fang, Fang; Huang, Miner; He, Sheng

2006-11-07

Human observers are constantly bombarded with a vast amount of information. Selective attention helps us to quickly process what is important while ignoring the irrelevant. In this study, we demonstrate that information that has not entered observers' consciousness, such as interocularly suppressed (invisible) erotic pictures, can direct the distribution of spatial attention. Furthermore, invisible erotic information can either attract or repel observers' spatial attention depending on their gender and sexual orientation. While unaware of the suppressed pictures, heterosexual males' attention was attracted to invisible female nudes, heterosexual females' attention was attracted to invisible male nudes, gay males behaved similarly to heterosexual females, and gay/bisexual females performed in-between heterosexual males and females.

A gender- and sexual orientation-dependent spatial attentional effect of invisible images

PubMed Central

Jiang, Yi; Costello, Patricia; Fang, Fang; Huang, Miner; He, Sheng

2006-01-01

Human observers are constantly bombarded with a vast amount of information. Selective attention helps us to quickly process what is important while ignoring the irrelevant. In this study, we demonstrate that information that has not entered observers' consciousness, such as interocularly suppressed (invisible) erotic pictures, can direct the distribution of spatial attention. Furthermore, invisible erotic information can either attract or repel observers' spatial attention depending on their gender and sexual orientation. While unaware of the suppressed pictures, heterosexual males' attention was attracted to invisible female nudes, heterosexual females' attention was attracted to invisible male nudes, gay males behaved similarly to heterosexual females, and gay/bisexual females performed in-between heterosexual males and females. PMID:17075055

Environmental variability and acoustic signals: a multi-level approach in songbirds.

PubMed

Medina, Iliana; Francis, Clinton D

2012-12-23

Among songbirds, growing evidence suggests that acoustic adaptation of song traits occurs in response to habitat features. Despite extensive study, most research supporting acoustic adaptation has only considered acoustic traits averaged for species or populations, overlooking intraindividual variation of song traits, which may facilitate effective communication in heterogeneous and variable environments. Fewer studies have explicitly incorporated sexual selection, which, if strong, may favour variation across environments. Here, we evaluate the prevalence of acoustic adaptation among 44 species of songbirds by determining how environmental variability and sexual selection intensity are associated with song variability (intraindividual and intraspecific) and short-term song complexity. We show that variability in precipitation can explain short-term song complexity among taxonomically diverse songbirds, and that precipitation seasonality and the intensity of sexual selection are related to intraindividual song variation. Our results link song complexity to environmental variability, something previously found for mockingbirds (Family Mimidae). Perhaps more importantly, our results illustrate that individual variation in song traits may be shaped by both environmental variability and strength of sexual selection.

Sexual selection of male parental care in giant water bugs

PubMed Central

Ohba, Shin-ya; Okuda, Noboru; Kudo, Shin-ichi

2016-01-01

Paternal care can be maintained under sexual selection, if it helps in attracting more mates. We tested the hypothesis in two giant water bug species, Appasus major and Appasus japonicus, that male parental care is sexually selected through female preference for caring males. Females were given an opportunity to choose between two males. In the first test of female mate choice, one male carried eggs on its back, while the other did not. The egg status was switched between these two males in the second test. The experiment revealed that females of both species preferred caring males (i.e. egg-bearing) to non-caring males. Nonetheless, the female mate preference for egg-bearing males was stronger in A. major than in A. japonicus. Our results suggest that sexual selection plays an important role in maintaining elaborate paternal care in giant water bugs, but the importance of egg-bearing by males in female mate choice varies among species. PMID:27293778

Sexual homicides in South Africa: A national cross-sectional epidemiological study of adult women and children

PubMed Central

Mathews, Shanaaz; Lombard, Carl; Martin, Lorna J.; Jewkes, Rachel

2017-01-01

Sexual homicides of women and children are extreme forms of violence against women and children and are located within the broader context of gender inequality and social norms that condone sexual violence and gender based violence against women and children. The aim of this study is to describe the prevalence and characteristics of sexual homicide of women and children nationally in South Africa. Methods We conducted a retrospective national mortuary based study to identify all adult female homicides (18 years and older) and all child homicides (boys and girls < 18 years) in 2009 in a randomly selected, proportionate sample of mortuaries. Victim, perpetrator and crime data were collected in three processes: from the mortuary register, the autopsy report and from police with the identification of sexual homicides validated across the data collection processes. Findings Among the 2670 (95% CI: 2311–2979) adult women killed in 2009, 494 (95% CI: 406–574) were identified as sexual homicides which was 19.8% (95% CI: 17.6–22.0) of all adult female homicides and among 1277 (95% CI: 1091–1462) children killed in SA, sexual homicides were found in 104 (95% CI: 77–132) of the child homicides which was 8.7% (95% CI: 10.9–11.2%) of these murders. Strangulation was the most common cause of death for both children and adult females. A distinct age and sex pattern was found among children with only 1% boy child death identified as a sexual homicide and 92% of all the child sexual homicides were among girls. Strangulation was the most common manner of death among children (35.5%) and perpetrators were seldom strangers. However, no difference in the proportion of convictions between the sexual homicides and non-sexual homicides were found for both adult females and children. Conclusion Rape homicide is not a rare event in South Africa, with one in five female homicides and nearly one in ten child homicides identified with an associated sexual crime. These high prevalences are amongst the highest levels reported in the literature with our study among the few reporting on the epidemiology of child sexual homicide. Reducing mortality is an important policy goal for South Africa and for the rest of the world and the prevention of female and child homicide is an important part of attaining this goal. PMID:29040329

The peacock train does not handicap cursorial locomotor performance

PubMed Central

Thavarajah, Nathan K.; Tickle, Peter G.; Nudds, Robert L.; Codd, Jonathan R.

2016-01-01

Exaggerated traits, like the peacock train, are recognized as classic examples of sexual selection. The evolution of sexual traits is often considered paradoxical as, although they enhance reproductive success, they are widely presumed to hinder movement and survival. Many exaggerated traits represent an additional mechanical load that must be carried by the animal and therefore may influence the metabolic cost of locomotion and constrain locomotor performance. Here we conducted respirometry experiments on peacocks and demonstrate that the exaggerated sexually selected train does not compromise locomotor performance in terms of the metabolic cost of locomotion and its kinematics. Indeed, peacocks with trains had a lower absolute and mass specific metabolic cost of locomotion. Our findings suggest that adaptations that mitigate any costs associated with exaggerated morphology are central in the evolution of sexually selected traits. PMID:27805067

Sexual dimorphism in cuticular hydrocarbons of the Australian field cricket Teleogryllus oceanicus (Orthoptera: Gryllidae).

PubMed

Thomas, Melissa L; Simmons, Leigh W

2008-06-01

Sexual dimorphism is presumed to reflect adaptive divergence in response to selection favouring different optimal character states in the two sexes. Here, we analyse patterns of sexual dimorphism in the cuticular hydrocarbons of the Australian field cricket Teleogryllus oceanicus using gas chromatography. Ten of the 25 peaks found in our chromatographs, differed in their relative abundance between the sexes. The presence of sexual dimorphism in T. oceanicus is discussed in reference to a review of sexual dimorphism in cuticular hydrocarbons of other insects. We found that this trait has been examined in 103 species across seven different orders. Seventy-six of these species (73%) displayed sex specificity of cuticular hydrocarbons, the presence/absence of which does not appear to be directly linked to phylogeny. The occurrence of sexual dimorphism in cuticular hydrocarbons of some but not other species, and the extent of variation within genera, suggest that this divergence has been driven primarily by sexual selection.

Selection of Film Clips and Development of a Video for the Investigation of Sexual Decision Making among Men Who Have Sex with Men

PubMed Central

Woolf-King, Sarah E.; Maisto, Stephen; Carey, Michael; Vanable, Peter

2013-01-01

Experimental research on sexual decision making is limited, despite the public health importance of such work. We describe formative work conducted in advance of an experimental study designed to evaluate the effects of alcohol intoxication and sexual arousal on risky sexual decision making among men who have sex with men. In Study 1, we describe the procedures for selecting and validating erotic film clips (to be used for the experimental manipulation of arousal). In Study 2, we describe the tailoring of two interactive role-play videos to be used to measure risk perception and communication skills in an analog risky sex situation. Together, these studies illustrate a method for creating experimental stimuli to investigate sexual decision making in a laboratory setting. Research using this approach will support experimental research that affords a stronger basis for drawing causal inferences regarding sexual decision making. PMID:19760530

Sexual Dimorphism and Sexual Selection: A Unified Economic Analysis1

PubMed Central

Chu, C. Y. Cyrus; Lee, Ronald D.

2012-01-01

We develop a life history model with two sexes, and study the optimal energy allocation strategy of males and females. We join Darwin and others in suggesting that the origin of sexual dimorphism and sexual selection is the difference between male and female reproduction costs. Due to this assumed cost difference, the resulting Bellman equations of gene dynamics in our two-sex life history model imply a large “energy surplus” on the part of males. This allows the male form to devote energy to the development of some costly male traits that help the males to compete for access to females. These costly male traits are sexually dimorphic. Using this life history model, we are able to explain important features of sexual dimorphism, as well as why males often transfer less to their offspring than do females, and why only females have menopause. PMID:22699007

Feederism: an exaggeration of a normative mate selection preference?

PubMed

Terry, Lesley L; Suschinsky, Kelly D; Lalumière, Martin L; Vasey, Paul L

2012-02-01

Quinsey and Lalumière (1995) suggested that some, if not most, paraphilias are exaggerated manifestations of more normative and functional mate selection preferences. The present study tested whether Feederism, a fat fetish focused on erotic eating, feeding, and gaining weight, is an exaggeration of a sexual arousal pattern commonly seen in the general population. Thirty participants (15 men and 15 women) recruited from the general population were assessed using penile plethysmography and vaginal photoplethysmography, respectively. None of the participants were self-identified Feeders or Feedees. Participants were shown sexual, neutral, and feeding still images while listening to audio recordings of sexual, neutral, and feeding stories. Participants did not genitally respond to feeding stimuli. However, both men and women subjectively rated feeding stimuli as more sexually arousing than neutral stimuli. We discuss the discordance between physiological and self-reported sexual arousal in the context of sex differences in sexual concordance and implications for future research.

Adolescent Sexuality Related Beliefs and Differences by Sexual Experience Status

ERIC Educational Resources Information Center

Tolma, Eleni L.; Oman, Roy F.; Vesely, Sara K.; Aspy, Cheryl B.; Rodine, Sharon; Marshall, LaDonna; Fluhr, Janene

2007-01-01

Purpose: To examine if attitudes toward premarital sex, beliefs about peer influence, and family communication about sexual relationships differ by sexual experience status. Methods: Data were collected from a randomly selected ethnically diverse youth sample (N = 1,318) residing in two Midwestern cities. The primary method used in data analysis…

Sexual Experiences Survey: A Research Instrument Investigating Sexual Aggression and Victimization.

ERIC Educational Resources Information Center

Koss, Mary P. Oros, Cheryl J.

1982-01-01

Developed a survey capable of reflecting hidden cases of rape and of documenting a dimensional view of sexual aggression/sexual victimization. The survey was administered to 3,862 university students. Results supported a dimensional view. Discusses the viability of a survey approach to sample selection for future rape research. (Author)

Selection on bristle length has the ability to drive the evolution of male abdominal appendages in the sepsid fly Themira biloba.

PubMed

Herath, B; Dochtermann, N A; Johnson, J I; Leonard, Z; Bowsher, J H

2015-12-01

Many exaggerated and novel traits are strongly influenced by sexual selection. Although sexual selection is a powerful evolutionary force, underlying genetic interactions can constrain evolutionary outcomes. The relative strength of selection vs. constraint has been a matter of debate for the evolution of male abdominal appendages in sepsid flies. These abdominal appendages are involved in courtship and mating, but their function has not been directly tested. We performed mate choice experiments to determine whether sexual selection acts on abdominal appendages in the sepsid Themira biloba. We tested whether appendage bristle length influenced successful insemination by surgically trimming the bristles. Females paired with males that had shortened bristles laid only unfertilized eggs, indicating that long bristles are necessary for successful insemination. We also tested whether the evolution of bristle length was constrained by phenotypic correlations with other traits. Analyses of phenotypic covariation indicated that bristle length was highly correlated with other abdominal appendage traits, but was not correlated with abdominal sternite size. Thus, abdominal appendages are not exaggerated traits like many sexual ornaments, but vary independently from body size. At the same time, strong correlations between bristle length and appendage length suggest that selection on bristle length is likely to result in a correlated increase in appendage length. Bristle length is under sexual selection in T. biloba and has the potential to evolve independently from abdomen size. © 2015 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2015 European Society For Evolutionary Biology.

Sexual selection in a lekking bird: the relative opportunity for selection by female choice and male competition.

PubMed

DuVal, Emily H; Kempenaers, Bart

2008-09-07

Leks are classic models for studies of sexual selection due to extreme variance in male reproductive success, but the relative influence of intrasexual competition and female mate choice in creating this skew is debatable. In the lekking lance-tailed manakin (Chiroxiphia lanceolata), these selective episodes are temporally separated into intrasexual competition for alpha status and female mate choice among alpha males that rarely interact. Variance in reproductive success between status classes of adult males (alpha versus non-alpha) can therefore be attributed to male-male competition whereas that within status largely reflects female mate choice. This provides an excellent opportunity for quantifying the relative contribution of each of these mechanisms of sexual selection to the overall opportunity for sexual selection on males (I males). To calculate variance in actual reproductive success, we assigned genetic paternity to 92.3% of 447 chicks sampled in seven years. Reproduction by non-alphas was rare and apparently reflected status misclassifications or opportunistic copulations en route to attaining alpha status rather than alternative mating strategies. On average 31% (range 7-44%, n=6 years) of the total I males was due to variance in reproductive success between alphas and non-alphas. Similarly, in a cohort of same-aged males followed for six years, 44-58% of the total I males was attributed to variance between males of different status. Thus, both intrasexual competition for status and female mate choice among lekking alpha males contribute substantially to the potential for sexual selection in this species.

Sexual selection in a lekking bird: the relative opportunity for selection by female choice and male competition

PubMed Central

DuVal, Emily H; Kempenaers, Bart

2008-01-01

Leks are classic models for studies of sexual selection due to extreme variance in male reproductive success, but the relative influence of intrasexual competition and female mate choice in creating this skew is debatable. In the lekking lance-tailed manakin (Chiroxiphia lanceolata), these selective episodes are temporally separated into intrasexual competition for alpha status and female mate choice among alpha males that rarely interact. Variance in reproductive success between status classes of adult males (alpha versus non-alpha) can therefore be attributed to male–male competition whereas that within status largely reflects female mate choice. This provides an excellent opportunity for quantifying the relative contribution of each of these mechanisms of sexual selection to the overall opportunity for sexual selection on males (Imales). To calculate variance in actual reproductive success, we assigned genetic paternity to 92.3% of 447 chicks sampled in seven years. Reproduction by non-alphas was rare and apparently reflected status misclassifications or opportunistic copulations en route to attaining alpha status rather than alternative mating strategies. On average 31% (range 7–44%, n=6 years) of the total Imales was due to variance in reproductive success between alphas and non-alphas. Similarly, in a cohort of same-aged males followed for six years, 44–58% of the total Imales was attributed to variance between males of different status. Thus, both intrasexual competition for status and female mate choice among lekking alpha males contribute substantially to the potential for sexual selection in this species. PMID:18495620

Prevalence and risk factors of female sexual dysfunction among healthcare personnel in Malaysia.

PubMed

Grewal, Gurdeep Singh; Gill, Jesjeet Singh; Sidi, Hatta; Gurpreet, Kaur; Jambunathan, Stephen Thevanathan; Suffee, Nusrat J; Midin, Marhani; Nik Jaafar, Nik Ruzyanei; Das, Srijit

2014-01-01

To determine the prevalence and risk factors of female sexual dysfunction (FSD) among healthcare personnel in selected healthcare facilities in Malaysia. This was a cross-sectional study carried out at three large healthcare facilities that were selected by convenience sampling. Within each facility, stratified random sampling was used to select suitable candidates to participate in the study (n=201). Validated questionnaires were used to assess depression, anxiety, sexual function in women and erectile dysfunction (ED) in their partners. The prevalence of FSD was 5.5%. Women with sexual dysfunction were more likely to be married longer (OR=4.08; 95% CI; 1.15-4.50), had lower frequency of sexual intercourse (OR=5.00; 95% C; 1.05-23.76) and had a spouse with ED (OR=24.35; 95% CI; 4.55-130.37). Multivariate analysis showed that ED was the strongest predictor for FSD (AOR=27.30; 95% CI; 4.706-159.08). One in eighteen female healthcare personnel suffered from FSD and presence of ED in the partner strongly impacted her sexual function, negatively. The findings highlight the importance of including the male partner in clinical assessment of FSD. Copyright © 2014 Elsevier Inc. All rights reserved.

Positive feedback in the transition from sexual reproduction to parthenogenesis.

PubMed

Schwander, Tanja; Vuilleumier, Séverine; Dubman, Janie; Crespi, Bernard J

2010-05-07

Understanding how new phenotypes evolve is challenging because intermediate stages in transitions from ancestral to derived phenotypes often remain elusive. Here we describe and evaluate a new mechanism facilitating the transition from sexual reproduction to parthenogenesis. In many sexually reproducing species, a small proportion of unfertilized eggs can hatch spontaneously ('tychoparthenogenesis') and develop into females. Using an analytical model, we show that if females are mate-limited, tychoparthenogenesis can result in the loss of males through a positive feedback mechanism whereby tychoparthenogenesis generates female-biased sex ratios and increasing mate limitation. As a result, the strength of selection for tychoparthenogenesis increases in concert with the proportion of tychoparthenogenetic offspring in the sexual population. We then tested the hypothesis that mate limitation selects for tychoparthenogenesis and generates female-biased sex ratios, using data from natural populations of sexually reproducing Timema stick insects. Across 41 populations, both the tychoparthenogenesis rates and the proportions of females increased exponentially as the density of individuals decreased, consistent with the idea that low densities of individuals result in mate limitation and selection for reproductive insurance through tychoparthenogenesis. Our model and data from Timema populations provide evidence for a simple mechanism through which parthenogenesis can evolve rapidly in a sexual population.

How multiple mating by females affects sexual selection

PubMed Central

Shuster, Stephen M.; Briggs, William R.; Dennis, Patricia A.

2013-01-01

Multiple mating by females is widely thought to encourage post-mating sexual selection and enhance female fitness. We show that whether polyandrous mating has these effects depends on two conditions. Condition 1 is the pattern of sperm utilization by females; specifically, whether, among females, male mating number, m (i.e. the number of times a male mates with one or more females) covaries with male offspring number, o. Polyandrous mating enhances sexual selection only when males who are successful at multiple mating also sire most or all of each of their mates' offspring, i.e. only when Cov♂(m,o), is positive. Condition 2 is the pattern of female reproductive life-history; specifically, whether female mating number, m, covaries with female offspring number, o. Only semelparity does not erode sexual selection, whereas iteroparity (i.e. when Cov♀(m,o), is positive) always increases the variance in offspring numbers among females, which always decreases the intensity of sexual selection on males. To document the covariance between mating number and offspring number for each sex, it is necessary to assign progeny to all parents, as well as identify mating and non-mating individuals. To document significant fitness gains by females through iteroparity, it is necessary to determine the relative magnitudes of male as well as female contributions to the total variance in relative fitness. We show how such data can be collected, how often they are collected, and we explain the circumstances in which selection favouring multiple mating by females can be strong or weak. PMID:23339237

A quasispecies approach to the evolution of sexual replication in unicellular organisms.

PubMed

Tannenbaum, Emmanuel; Fontanari, José F

2008-03-01

This study develops a simplified model describing the evolutionary dynamics of a population composed of obligate sexually and asexually reproducing, unicellular organisms. The model assumes that the organisms have diploid genomes consisting of two chromosomes, and that the sexual organisms replicate by first dividing into haploid intermediates, which then combine with other haploids, followed by the normal mitotic division of the resulting diploid into two new daughter cells. We assume that the fitness landscape of the diploids is analogous to the single-fitness-peak approach often used in single-chromosome studies. That is, we assume a master chromosome that becomes defective with just one point mutation. The diploid fitness then depends on whether the genome has zero, one, or two copies of the master chromosome. We also assume that only pairs of haploids with a master chromosome are capable of combining so as to produce sexual diploid cells, and that this process is described by second-order kinetics. We find that, in a range of intermediate values of the replication fidelity, sexually reproducing cells can outcompete asexual ones, provided the initial abundance of sexual cells is above some threshold value. The range of values where sexual reproduction outcompetes asexual reproduction increases with decreasing replication rate and increasing population density. We critically evaluate a common approach, based on a group selection perspective, used to study the competition between populations and show its flaws in addressing the evolution of sex problem.

Sexual selection and sex linkage.

PubMed

Kirkpatrick, Mark; Hall, David W

2004-04-01

Some animal groups, such as birds, seem prone to extreme forms of sexual selection. One contributing factor may be sex linkage of genes affecting male displays and female preferences. Here we show that sex linkage can have substantial effects on the genetic correlation between these traits and consequently for Fisher's runaway and the good-genes mechanisms of sexual selection. Under some kinds of sex linkage (e.g. Z-linked preferences), a runaway is more likely than under autosomal inheritance, while under others (e.g., X-linked preferences and autosomal displays), the good-genes mechanism is particularly powerful. These theoretical results suggest empirical tests based on the comparative method.

Does students' exposure to gender discrimination and sexual harassment in medical school affect specialty choice and residency program selection?

PubMed

Stratton, Terry D; McLaughlin, Margaret A; Witte, Florence M; Fosson, Sue E; Nora, Lois Margaret

2005-04-01

To examine the role of gender discrimination and sexual harassment in medical students' choice of specialty and residency program. Anonymous, self-administered questionnaires were distributed in 1997 to fourth-year students enrolled in 14 public and private U.S. medical schools. In addition to reporting the frequency of gender discrimination and sexual harassment encountered during preclinical coursework, core clerkships, elective clerkships, and residency selection, students assessed the impact of these exposures (none, a little, some, quite a bit, the deciding factor) on their specialty choices and rankings of residency programs. A total of 1,314 (69%) useable questionnaires were returned. Large percentages of men (83.2%) and women (92.8%) experienced, observed, or heard about at least one incident of gender discrimination and sexual harassment during medical school, although more women reported such behavior across all training contexts. Compared with men, significantly (p

Queer narratives and minority stress: Stories from lesbian, gay and bisexual individuals in Norway.

PubMed

Synnes, Oddgeir; Malterud, Kirsti

2018-03-01

This study aims to explore how minority stress related to sexual orientation is reflected in narratives from lesbian, gay and bisexual (LGB) individuals in Norway, with an impact for national public health policy. Arthur Frank's dialogical narrative analysis was applied to personal stories from 65 persons self-referring to different categories of queer identities, submitted online anonymously to a Norwegian national archive for queer history. A purposive sample of three different stories were selected due to their capacity to illuminate how various aspects of minority stress are narrated in diverse interplays between individual voices and resources, and cultural scripts and societal influences. Our analysis highlighted how stories may offer significant glimpses into the dynamic and complex fashioning of sexual identities, giving precious clues to the vulnerabilities and strengths of the narrator. Contemporary queer narratives from Norway reflect meaning-making related to sexual orientation that are influenced by, and expand upon, the classical scripts dominated by tragedy and tristesse, personal progress or simply no particular tension. LGB individuals of different ages and backgrounds had experienced aspects of minority stress related to their sexual orientation, with a substantial impact on identity, even when significant others were encouraging. The stories indicate that positive proximal processes, such as personal resilience and sympathetic environments, can support mental health and counteract negative effects of distal processes contributing to minority stress, such as heteronormativity and subtle microaggression. Public health strategies addressing attitudes to sexual orientation among the general population may contribute to diverse affirmative cultural scripts about queer lives, thereby enhancing queer mental health.

Symbolic meanings of sex in relationships: Developing the Meanings of Sexual Behavior Inventory.

PubMed

Shaw, Amanda M; Rogge, Ronald D

2017-10-01

Consistent with symbolic interactionism and motivation research, the study explored the meanings of sexual behavior in romantic relationships in a sample of 3,003 online respondents. Starting with a pool of 104 respondent-generated items, Exploratory and Confirmatory Factor analyses in separate sample halves revealed a stable set of 9 dimensions within that item pool that formed 2 higher-order factors representing positive (to share pleasure, to bond, to de-stress, to energize the relationship, to learn more about each other) and negative (to manage conflict, as an incentive, to express anger, and to control partner) meanings of sexual behavior within relationships. Item Response Theory analyses helped select the 4-5 most effective items of each dimension for inclusion in the Meanings of Sexual Behavior Inventory (MoSBI). Generalizability analyses suggested that the MoSBI subscale scores continued to show high levels of internal consistency across a broad range of demographic subgroups (e.g., racial/ethnic groups, gay and lesbian respondents, and various levels of education). The MoSBI subscales demonstrated moderate and distinct patterns of association with a range of conceptual boundary scales (e.g., relationship and sexual satisfaction, emotional support, negative conflict behavior, and frequency of sexual behavior) suggesting that these scales represent novel relationship processes. Consistent with this, analyses in the 862 respondents completing a 2-month follow-up assessment suggested that the meanings of sexual behavior predicted residual change in relationship satisfaction, even after controlling for frequency of sexual behavior within the relationships. Implications are discussed. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

BODY SIZE AND HAREM SIZE IN MALE RED-WINGED BLACKBIRDS: MANIPULATING SELECTION WITH SEX-SPECIFIC FEEDERS.

PubMed

Rohwer, Sievert; Langston, Nancy; Gori, Dave

1996-10-01

We experimentally manipulated the strength of selection in the field on red-winged blackbirds (Agelaius phoeniceus) to test hypotheses about contrasting selective forces that favor either large or small males in sexually size dimorphic birds. Selander (1972) argued that sexual selection favors larger males, while survival selection eventually stabilizes male size because larger males do not survive as well as smaller males during harsh winters. Searcy (1979a) proposed instead that sexual selection may be self limiting: male size might be stabilized not by overwinter mortality, but by breeding-season sexual selection that favors smaller males. Under conditions of energetic stress, smaller males should be able to display more and thus achieve higher reproductive success. Using feeders that provisioned males or females but not both, we produced conditions that mimicked the extremes of natural conditions. We found experimental support for the hypothesis that when food is abundant, sexual selection favors larger males. But even under conditions of severe energetic stress, smaller males did not gain larger harems, as the self-limiting hypothesis predicted. Larger males were more energetically stressed than smaller males, but in ways that affected their future reproductive output rather than their current reproductive performance. Stressed males that returned had smaller wings and tails than those that did not return; among returning stressed males, relative harem sizes were inversely related to wing and tail length. Thus, male body size may be stabilized not by survival costs during the non-breeding season, nor by energetic costs during the breeding season, but by costs of future reproduction that larger males pay for their increased breeding-season effort. © 1996 The Society for the Study of Evolution.

Sexual health problems of adolescents attending a sexual health service.

PubMed

Black, Christine; McGough, Pauline; Fargie, Fiona; Brown, Beverley Wilson

2012-02-01

To determine whether adolescents who present at a sexual health service aged 13 have more sexual health problems in later years than those who present aged 15. A case-note review was done in 2009 to identify sexual health problems for all 13-year-olds who registered with Sandyford sexual health service from April 2003 until December 2004 (group 1). This was compared with selected notes from adolescents who were 15 years old at the time of registration (group 2). Eighty-eight youths aged 13 and 632 aged 15 registered in the aforementioned period. Ninety records of 15-year-olds were selected for comparison. Twenty two of the 86 girls in group 1 and 31 of the 87 girls in group 2 had at least one pregnancy. Twenty-one adolescents in group 1 and 25 of those in group 2 had a sexually transmitted infection. Thirteen youths in group 1 and one in group 2 had suffered a sexual assault. Adolescents aged 13 at first registration with this service have more sexual health problems and warrant additional support throughout their teenage years. A very young age at first registration should prompt health professionals to provide additional clinical, emotional and social support.

Colour ornamentation in the blue tit: quantitative genetic (co)variances across sexes

PubMed Central

Charmantier, A; Wolak, M E; Grégoire, A; Fargevieille, A; Doutrelant, C

2017-01-01

Although secondary sexual traits are commonly more developed in males than females, in many animal species females also display elaborate ornaments or weaponry. Indirect selection on correlated traits in males and/or direct sexual or social selection in females are hypothesized to drive the evolution and maintenance of female ornaments. Yet, the relative roles of these evolutionary processes remain unidentified, because little is known about the genetic correlation that might exist between the ornaments of both sexes, and few estimates of sex-specific autosomal or sex-linked genetic variances are available. In this study, we used two wild blue tit populations with 9 years of measurements on two colour ornaments: one structurally based (blue crown) and one carotenoid based (yellow chest). We found significant autosomal heritability for the chromatic part of the structurally based colouration in both sexes, whereas carotenoid chroma was heritable only in males, and the achromatic part of both colour patches was mostly non heritable. Power limitations, which are probably common among most data sets collected so far in wild populations, prevented estimation of sex-linked genetic variance. Bivariate analyses revealed very strong cross-sex genetic correlations in all heritable traits, although the strength of these correlations was not related to the level of sexual dimorphism. In total, our results suggest that males and females share a majority of their genetic variation underlying colour ornamentation, and hence the evolution of these sex-specific traits may depend greatly on correlated responses to selection in the opposite sex. PMID:27577691

The evolution of sex is favoured during adaptation to new environments.

PubMed

Becks, Lutz; Agrawal, Aneil F

2012-01-01

Both theory and experiments have demonstrated that sex can facilitate adaptation, potentially yielding a group-level advantage to sex. However, it is unclear whether this process can help solve the more difficult problem of the maintenance of sex within populations. Using experimental populations of the facultatively sexual rotifer Brachionus calyciflorus, we show that rates of sex evolve to higher levels during adaptation but then decline as fitness plateaus. To assess the fitness consequences of genetic mixing, we directly compare the fitnesses of sexually and asexually derived genotypes that naturally occur in our experimental populations. Sexually derived genotypes are more fit than asexually derived genotypes when adaptive pressures are strong, but this pattern reverses as the pace of adaptation slows, matching the pattern of evolutionary change in the rate of sex. These fitness assays test the net effect of sex but cannot be used to disentangle whether selection on sex arises because highly sexual lineages become associated with different allele combinations or with different allele frequencies than less sexual lineages (i.e., "short-" or "long-term" effects, respectively). We infer which of these mechanisms provides an advantage to sex by performing additional manipulations to obtain fitness distributions of sexual and asexual progeny arrays from unbiased parents (rather than from naturally occurring, and thereby evolutionarily biased, parents). We find evidence that sex breaks down adaptive gene combinations, resulting in lower average fitness of sexual progeny (i.e., a short-term disadvantage to sex). As predicted by theory, the advantage to sex arises because sexually derived progeny are more variable in fitness, allowing for faster adaptation. This "long-term advantage" builds over multiple generations, eventually resulting in higher fitness of sexual types.

The Evolution of Sex Is Favoured During Adaptation to New Environments

PubMed Central

Becks, Lutz; Agrawal, Aneil F.

2012-01-01

Both theory and experiments have demonstrated that sex can facilitate adaptation, potentially yielding a group-level advantage to sex. However, it is unclear whether this process can help solve the more difficult problem of the maintenance of sex within populations. Using experimental populations of the facultatively sexual rotifer Brachionus calyciflorus, we show that rates of sex evolve to higher levels during adaptation but then decline as fitness plateaus. To assess the fitness consequences of genetic mixing, we directly compare the fitnesses of sexually and asexually derived genotypes that naturally occur in our experimental populations. Sexually derived genotypes are more fit than asexually derived genotypes when adaptive pressures are strong, but this pattern reverses as the pace of adaptation slows, matching the pattern of evolutionary change in the rate of sex. These fitness assays test the net effect of sex but cannot be used to disentangle whether selection on sex arises because highly sexual lineages become associated with different allele combinations or with different allele frequencies than less sexual lineages (i.e., “short-” or “long-term” effects, respectively). We infer which of these mechanisms provides an advantage to sex by performing additional manipulations to obtain fitness distributions of sexual and asexual progeny arrays from unbiased parents (rather than from naturally occurring, and thereby evolutionarily biased, parents). We find evidence that sex breaks down adaptive gene combinations, resulting in lower average fitness of sexual progeny (i.e., a short-term disadvantage to sex). As predicted by theory, the advantage to sex arises because sexually derived progeny are more variable in fitness, allowing for faster adaptation. This “long-term advantage” builds over multiple generations, eventually resulting in higher fitness of sexual types. PMID:22563299

Quantitative measures of sexual selection reveal no evidence for sex-role reversal in a sea spider with prolonged paternal care.

PubMed

Barreto, Felipe S; Avise, John C

2010-10-07

Taxa in which males alone invest in postzygotic care of offspring are often considered good models for investigating the proffered relationships between sexual selection and mating systems. In the pycnogonid sea spider Pycnogonum stearnsi, males carry large egg masses on their bodies for several weeks, so this species is a plausible candidate for sex-role reversal (greater intensity of sexual selection on females than on males). Here, we couple a microsatellite-based assessment of the mating system in a natural population with formal quantitative measures of genetic fitness to investigate the direction of sexual selection in P. stearnsi. Both sexes proved to be highly polygamous and showed similar standardized variances in reproductive and mating successes. Moreover, the fertility (number of progeny) of males and females appeared to be equally and highly dependent on mate access, as shown by similar Bateman gradients for the two sexes. The absence of sex-role reversal in this population of P. stearnsi is probably attributable to the fact that males are not limited by brooding space but have evolved an ability to carry large numbers of progeny. Body length was not a good predictor of male mating or reproductive success, so the aim of future studies should be to determine what traits are the targets of sexual selection in this species.

The contrasting role of male relatedness in different mechanisms of sexual selection in red junglefowl.

PubMed

Tan, Cedric Kai Wei; Doyle, Philippa; Bagshaw, Emma; Richardson, David S; Wigby, Stuart; Pizzari, Tommaso

2017-02-01

In structured populations, competition for reproductive opportunities should be relaxed among related males. The few tests of this prediction often neglect the fact that sexual selection acts through multiple mechanisms, both before and after mating. We performed experiments to study the role of within-group male relatedness across pre- and postcopulatory mechanisms of sexual selection in social groups of red junglefowl, Gallus gallus, in which two related males and one unrelated male competed over females unrelated to all the males. We confirm theoretical expectations that, after controlling for male social status, competition over mating was reduced among related males. However, this effect was contrasted by other sexual selection mechanisms. First, females biased male mating in favor of the unrelated male, and might also favor his inseminations after mating. Second, males invested more-rather than fewer-sperm in postcopulatory competition with relatives. A number of factors may contribute to explain this counterintuitive pattern of sperm allocation, including trade-offs between male investment in pre- versus postcopulatory competition, differences in the relative relatedness of pre- versus postcopulatory competitors, and female bias in sperm utilization in response to male relatedness. Collectively, these results reveal that within-group male relatedness may have contrasting effects in different mechanisms of sexual selection. © 2016 The Author(s). Evolution published by Wiley Periodicals, Inc. on behalf of The Society for the Study of Evolution.

Rapid loss of behavioral plasticity and immunocompetence under intense sexual selection.

PubMed

van Lieshout, Emile; McNamara, Kathryn B; Simmons, Leigh W

2014-09-01

Phenotypic plasticity allows animals to maximize fitness by conditionally expressing the phenotype best adapted to their environment. Although evidence for such adjustment in reproductive tactics is common, little is known about how phenotypic plasticity evolves in response to sexual selection. We examined the effect of sexual selection intensity on phenotypic plasticity in mating behavior using the beetle Callosobruchus maculatus. Male genital spines harm females during mating and females exhibit copulatory kicking, an apparent resistance trait aimed to dislodge mating males. After exposing individuals from male- and female-biased experimental evolution lines to male- and female-biased sociosexual environments, we examined behavioral plasticity in matings with standard partners. While females from female-biased lines kicked sooner after exposure to male-biased sociosexual contexts, in male-biased lines this plasticity was lost. Ejaculate size did not diverge in response to selection history, but males from both treatments exhibited plasticity consistent with sperm competition intensity models, reducing size as the number of competitors increased. Analysis of immunocompetence revealed reduced immunity in both sexes in male-biased lines, pointing to increased reproductive costs under high sexual selection. These results highlight how male and female reproductive strategies are shaped by interactions between phenotypically plastic and genetic mechanisms of sexual trait expression. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

Meiotic drive influences the outcome of sexually antagonistic selection at a linked locus.

PubMed

Patten, M M

2014-11-01

Most meiotic drivers, such as the t-haplotype in Mus and the segregation distorter (SD) in Drosophila, act in a sex-specific manner, gaining a transmission advantage through one sex although suffering only the fitness costs associated with the driver in the other. Their inheritance is thus more likely through one of the two sexes, a property they share with sexually antagonistic alleles. Previous theory has shown that pairs of linked loci segregating for sexually antagonistic alleles are more likely to remain polymorphic and that linkage disequilibrium accrues between them. I probe this similarity between drive and sexual antagonism and examine the evolution of chromosomes experiencing these selection pressures simultaneously. Reminiscent of previous theory, I find that: the opportunity for polymorphism increases for a sexually antagonistic locus that is physically linked to a driving locus; the opportunity for polymorphism at a driving locus also increases when linked to a sexually antagonistic locus; and stable linkage disequilibrium accompanies any polymorphic equilibrium. Additionally, I find that drive at a linked locus favours the fixation of sexually antagonistic alleles that benefit the sex in which drive occurs. Further, I show that under certain conditions reduced recombination between these two loci is selectively favoured. These theoretical results provide clear, testable predictions about the nature of sexually antagonistic variation on driving chromosomes and have implications for the evolution of genomic architecture. © 2014 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

Novel host plant leads to the loss of sexual dimorphism in a sexually selected male weapon.

PubMed

Allen, Pablo E; Miller, Christine W

2017-08-16

In this time of massive global change, species are now frequently interacting with novel players. Greater insight into the impact of these novel interactions on traits linked to fitness is essential, because effects on these traits can hinder population existence or promote rapid adaptation. Sexually selected weapons and ornaments frequently influence fitness and often have heightened condition-dependence in response to nutrition. Condition-dependence in response to different ecological conditions, a form of developmental plasticity, may be responsible for much of the intraspecific variation in sexually selected ornaments and weapons in wild populations. Here we examined the consequences of developing on a novel plant for the expression of size and shape in the leaf-footed cactus bug Narnia femorata (Hemiptera: Coreidae). The males of this species possess enlarged, sexually dimorphic femurs on their hind legs. These legs are used as weapons in male-male contests. Females are typically larger in overall body size. Our study revealed that developing upon a novel host can lead to pronounced phenotypically plastic change in sexually dimorphic traits. Male hind femurs were greatly impacted by the novel diet to the extent that the sexual dimorphism in hind femurs was lost. Further, dimorphism in body size increased, as males became tiny adults while females better maintained their body size. These patterns underscore the complex effects that novel species interactions may have on sexual phenotypes. © 2017 The Author(s).

The Influence of Knowledge and Awareness of Sexually Transmitted Diseases (STDs) on Change in Sexual Behaviour of Fresh Undergraduates of the Obafemi Awolowo University, Ile-Ife, Nigeria

ERIC Educational Resources Information Center

Adeniyi, W. O.; Okewole, J. O.

2014-01-01

The study examined the influence of knowledge and awareness of sexually transmitted diseases on change in sexual behaviour of fresh undergraduates with a view to providing useful suggestions for positive sexual behaviour of adolescents. The study adopted the descriptive survey design. A sample of 600 fresh undergraduates was selected from the…

Multiple origins of elytral reticulation modifications in the west palearctic Agabus bipustulatus complex (coleoptera, dytiscidae).

PubMed

Drotz, Marcus K; Brodin, Tomas; Nilsson, Anders N

2010-02-03

The Agabus bipustulatus complex includes one of Europe's most widely distributed and common diving beetles. This complex, which is known for its large morphological variation, has a complex demographic and altitudinal variation in elytral reticulation. The various depth of the reticulation imprint, both in smaller and larger meshes, results in both mat and shiny individuals, as well as intermediate forms. The West Palearctic lowland is inhabited by a sexually dimorphic form, with shiny males and mat females. In mountain regions, shiny individuals of both sexes are found intermixed with mat individuals or in pure populations in central and southern areas, whereas pure populations of mat individuals are exclusively found in the northern region at high altitude. Sexual selection is proposed as a driving force in shaping this variation. However, the occurrence of different types of reticulation in both sexes and disjunct geographical distribution patterns suggest an additional function of the reticulation. Here we investigate the phylogeographical history, genetic structure and reticulation variation of several named forms within the Agabus bipustulatus complex including A. nevadensis. The molecular analyses recognised several well-supported clades within the complex. Several of the named forms had two or more independent origins. Few south European populations were uniform in reticulation patterns, and the males were found to display large variation. Reticulation diversity and population genetic variability were clearly correlated to altitude, but no genetic differences were detected among populations with mixed or homogenous forms. Observed reduction in secondary reticulation in female and increased variance in male at high altitude in South Europe may be explained by the occurrence of an additional selective force, beside sexual selection. The combined effect of these selective processes is here demonstrated in an extreme case to generate isolation barriers between populations at high altitudes. Here we discuss this selective force in relation to thermal selection.

Female mediation of competitive fertilization success in Drosophila melanogaster.

PubMed

Lüpold, Stefan; Pitnick, Scott; Berben, Kirstin S; Blengini, Cecilia S; Belote, John M; Manier, Mollie K

2013-06-25

How females store and use sperm after remating can generate postcopulatory sexual selection on male ejaculate traits. Variation in ejaculate performance traits generally is thought to be intrinsic to males but is likely to interact with the environment in which sperm compete (e.g., the female reproductive tract). Our understanding of female contributions to competitive fertilization success is limited, however, in part because of the challenges involved in observing events within the reproductive tract of internally fertilizing species while discriminating among sperm from competing males. Here, we used females from crosses among isogenic lines of Drosophila melanogaster, each mated to two genetically standardized males (the first with green- and the second with red-tagged sperm heads) to demonstrate heritable variation in female remating interval, progeny production rate, sperm-storage organ morphology, and a number of sperm performance, storage, and handling traits. We then used multivariate analyses to examine relationships between this female-mediated variation and competitive paternity. In particular, the timing of female ejection of excess second-male and displaced first-male sperm was genetically variable and, by terminating the process of sperm displacement, significantly influenced the relative numbers of sperm from each male competing for fertilization, and consequently biased paternity. Our results demonstrate that females do not simply provide a static arena for sperm competition but rather play an active and pivotal role in postcopulatory processes. Resolving the adaptive significance of genetic variation in female-mediated mechanisms of sperm handling is critical for understanding sexual selection, sexual conflict, and the coevolution of male and female reproductive traits.

Sexual Identity, Sex of Sexual Contacts, and Health-Risk Behaviors among Students in Grades 9-12--Youth Risk Behavior Surveillance, Selected Sites, United States, 2001-2009. Morbidity and Mortality Weekly Report. Early Release. Volume 60

ERIC Educational Resources Information Center

Kann, Laura; O'Malley Olsen, Emily; McManus, Tim; Kinchen, Steve; Chyen, David; Harris, William A.; Wechsler, Howell

2011-01-01

Problem: Sexual minority youths are youths who identify themselves as gay or lesbian, bisexual, or unsure of their sexual identity or youths who have only had sexual contact with persons of the same sex or with both sexes. Population-based data on the health-risk behaviors practiced by sexual minority youths are needed at the state and local…

Adolescents' sexual media diets.

PubMed

Brown, J D

2000-08-01

A model of how adolescents choose, interpret, and interact with the mass media is discussed in the context of sexual development. The Media Practice Model suggests that adolescents select and react to sexual media diets that speak to an emerging sense of themselves as sexual human beings. Relatively little is known about how the sexual content adolescents attend to in the media is interpreted or incorporated into their lives. Entertainment-education and media literacy are two strategies for increasing the possibility of healthy outcomes from adolescents' use of sexual media.

How To Teach "Dirty" Books in High School.

ERIC Educational Resources Information Center

O'Malley, William J.

1967-01-01

Today's self-centered, utopian attitudes toward sexual experience compel teachers to avoid both overcaution and over-indulgence in selecting controversial books for classroom use. One method of selection is to rank books in a gradual progression from those requiring little literary and sexual sophistication in the reader to those requiring much…

Disturbances in the Field: Sexual Harassment Part III. Policies and Procedures of Selected National Organizations.

ERIC Educational Resources Information Center

Watstein, Sarah Barbara; Wilcots, Rosalyn

1994-01-01

Compares and contrasts policies and procedures pertaining to sexual harassment from selected national organizations with those of the American Library Association (ALA). Policies from the American Bar Association, American Council on Education, American Association of University Professors, American Psychological Association, and National…

The contributions of premating and postmating selection episodes to total selection in sex-role-reversed Gulf pipefish.

PubMed

Rose, Emily; Paczolt, Kimberly A; Jones, Adam G

2013-09-01

Empirical studies of sexual selection often focus on events occurring either before or after mating but rarely both and consequently may fail to discern the relative magnitudes and interactions of premating and postmating episodes of selection. Here, we simultaneously quantify premating and postmating selection in the sex-role-reversed Gulf pipefish by using a microsatellite-based analysis of parentage in experimental populations. Female pipefish exhibited an opportunity for selection (I) of 1.64, which was higher than that of males (0.35). Decompositions of I and the selection differential on body size showed that over 95% of the selection on females arose from the premating phase. We also found evidence for a trade-off between selection phases, where multiply mating females had significantly lower offspring survivorship compared to singly mated females. In males, variance in relative fitness arose mainly from the number of eggs received per copulation and a small number of males who failed to mate. Overall, our study exemplifies a general approach for the decomposition of total selection into premating and postmating phases to understand the interplay among components of natural and sexual selection that conspire to shape sexually selected traits.

Receiver discriminability drives the evolution of complex sexual signals by sexual selection.

PubMed

Cui, Jianguo; Song, Xiaowei; Zhu, Bicheng; Fang, Guangzhan; Tang, Yezhong; Ryan, Michael J

2016-04-01

A hallmark of sexual selection by mate choice is the evolution of exaggerated traits, such as longer tails in birds and more acoustic components in the calls of birds and frogs. Trait elaboration can be opposed by costs such as increased metabolism and greater predation risk, but cognitive processes of the receiver can also put a brake on trait elaboration. For example, according to Weber's Law traits of a fixed absolute difference will be more difficult to discriminate as the absolute magnitude increases. Here, we show that in the Emei music frog (Babina daunchina) increases in the fundamental frequency between successive notes in the male advertisement call, which increases the spectral complexity of the call, facilitates the female's ability to compare the number of notes between calls. These results suggest that female's discriminability provides the impetus to switch from enhancement of signaling magnitude (i.e., adding more notes into calls) to employing a new signal feature (i.e., increasing frequency among notes) to increase complexity. We suggest that increasing the spectral complexity of notes ameliorates some of the effects of Weber's Law, and highlights how perceptual and cognitive biases of choosers can have important influences on the evolution of courtship signals. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

Rapid evolution of asymmetric reproductive incompatibilities in stalk-eyed flies.

PubMed

Rose, Emily G; Brand, Cara L; Wilkinson, Gerald S

2014-02-01

The steps by which isolated populations acquire reproductive incompatibilities remain poorly understood. One potentially important process is postcopulatory sexual selection because it can generate divergence between populations in traits that influence fertilization success after copulation. Here we present a comprehensive analysis of this form of reproductive isolation by conducting reciprocal crosses between variably diverged populations of stalk-eyed flies (Teleopsis dalmanni). First, we measure seven types of reproductive incompatibility between copulation and fertilization. We then compare fertilization success to hatching success to quantify hybrid inviability. Finally, we determine if sperm competition acts to reinforce or counteract any incompatibilities. We find evidence for multiple incompatibilities in most crosses, including failure to store sperm after mating, failure of sperm to reach the site of fertilization, failure of sperm to fertilize eggs, and failure of embryos to develop. Local sperm have precedence over foreign sperm, but this effect is due mainly to differences in sperm transfer and reduced hatching success. Crosses between recently diverged populations are asymmetrical with regard to the degree and type of incompatibility. Because sexual conflict in these flies is low, postcopulatory sexual selection, rather than antagonistic coevolution, likely causes incompatibilities due to mismatches between male and female reproductive traits. © 2013 The Author(s). Evolution © 2013 The Society for the Study of Evolution.

Sex-specific genetic variance and the evolution of sexual dimorphism: a systematic review of cross-sex genetic correlations.

PubMed

Poissant, Jocelyn; Wilson, Alastair J; Coltman, David W

2010-01-01

The independent evolution of the sexes may often be constrained if male and female homologous traits share a similar genetic architecture. Thus, cross-sex genetic covariance is assumed to play a key role in the evolution of sexual dimorphism (SD) with consequent impacts on sexual selection, population dynamics, and speciation processes. We compiled cross-sex genetic correlations (r(MF)) estimates from 114 sources to assess the extent to which the evolution of SD is typically constrained and test several specific hypotheses. First, we tested if r(MF) differed among trait types and especially between fitness components and other traits. We also tested the theoretical prediction of a negative relationship between r(MF) and SD based on the expectation that increases in SD should be facilitated by sex-specific genetic variance. We show that r(MF) is usually large and positive but that it is typically smaller for fitness components. This demonstrates that the evolution of SD is typically genetically constrained and that sex-specific selection coefficients may often be opposite in sign due to sub-optimal levels of SD. Most importantly, we confirm that sex-specific genetic variance is an important contributor to the evolution of SD by validating the prediction of a negative correlation between r(MF) and SD.

Female behaviour and the interaction of male and female genital traits mediate sperm transfer during mating.

PubMed

Friesen, C R; Uhrig, E J; Mason, R T; Brennan, P L R

2016-05-01

Natural selection and post-copulatory sexual selection, including sexual conflict, contribute to genital diversification. Fundamental first steps in understanding how these processes shape the evolution of specific genital traits are to determine their function experimentally and to understand the interactions between female and male genitalia during copulation. Our experimental manipulations of male and female genitalia in red-sided garter snakes (Thamnophis sirtalis parietalis) reveal that copulation duration and copulatory plug deposition, as well as total and oviductal/vaginal sperm counts, are influenced by the interaction between male and female genital traits and female behaviour during copulation. By mating females with anesthetized cloacae to males with spine-ablated hemipenes using a fully factorial design, we identified significant female-male copulatory trait interactions and found that females prevent sperm from entering their oviducts by contracting their vaginal pouch. Furthermore, these muscular contractions limit copulatory plug size, whereas the basal spine of the male hemipene aids in sperm and plug transfer. Our results are consistent with a role of sexual conflict in mating interactions and highlight the evolutionary importance of female resistance to reproductive outcomes. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

Wear Fast, Die Young: More Worn Teeth and Shorter Lives in Iberian Compared to Scottish Red Deer

PubMed Central

Pérez-Barbería, F. J.; Carranza, J.; Sánchez-Prieto, C.

2015-01-01

Teeth in Cervidae are permanent structures that are not replaceable or repairable; consequently their rate of wear, due to the grinding effect of food and dental attrition, affects their duration and can determine an animal's lifespan. Tooth wear is also a useful indicator of accumulative life energy investment in intake and mastication and their interactions with diet. Little is known regarding how natural and sexual selection operate on dental structures within a species in contrasting environments and how these relate to life history traits to explain differences in population rates of tooth wear and longevity. We hypothesised that populations under harsh environmental conditions should be selected for more hypsodont teeth while sexual selection may maintain similar sex differences within different populations. We investigated the patterns of tooth wear in males and females of Iberian red deer (Cervus elaphus hispanicus) in Southern Spain and Scottish red deer (C. e. scoticus) across Scotland, that occur in very different environments, using 10343 samples from legal hunting activities. We found higher rates of both incisor and molar wear in the Spanish compared to Scottish populations. However, Scottish red deer had larger incisors at emergence than Iberian red deer, whilst molars emerged at a similar size in both populations and sexes. Iberian and Scottish males had earlier tooth depletion than females, in support of a similar sexual selection process in both populations. However, whilst average lifespan for Iberian males was 4 years shorter than that for Iberian females and Scottish males, Scottish males only showed a reduction of 1 year in average lifespan with respect to Scottish females. More worn molars were associated with larger mandibles in both populations, suggesting that higher intake and/or greater investment in food comminution may have favoured increased body growth, before later loss of tooth efficiency due to severe wear. These results illustrate how independent selection in both subspecies, that diverged 11,700 years BP, has resulted in the evolution of different longevity, although sexual selection has maintained a similar pattern of relative sex differences in tooth depletion. This study opens interesting questions on optimal allocation in life history trade-offs and the independent evolution of allopatric populations. PMID:26252380

Wear Fast, Die Young: More Worn Teeth and Shorter Lives in Iberian Compared to Scottish Red Deer.

PubMed

Pérez-Barbería, F J; Carranza, J; Sánchez-Prieto, C

2015-01-01

Teeth in Cervidae are permanent structures that are not replaceable or repairable; consequently their rate of wear, due to the grinding effect of food and dental attrition, affects their duration and can determine an animal's lifespan. Tooth wear is also a useful indicator of accumulative life energy investment in intake and mastication and their interactions with diet. Little is known regarding how natural and sexual selection operate on dental structures within a species in contrasting environments and how these relate to life history traits to explain differences in population rates of tooth wear and longevity. We hypothesised that populations under harsh environmental conditions should be selected for more hypsodont teeth while sexual selection may maintain similar sex differences within different populations. We investigated the patterns of tooth wear in males and females of Iberian red deer (Cervus elaphus hispanicus) in Southern Spain and Scottish red deer (C. e. scoticus) across Scotland, that occur in very different environments, using 10343 samples from legal hunting activities. We found higher rates of both incisor and molar wear in the Spanish compared to Scottish populations. However, Scottish red deer had larger incisors at emergence than Iberian red deer, whilst molars emerged at a similar size in both populations and sexes. Iberian and Scottish males had earlier tooth depletion than females, in support of a similar sexual selection process in both populations. However, whilst average lifespan for Iberian males was 4 years shorter than that for Iberian females and Scottish males, Scottish males only showed a reduction of 1 year in average lifespan with respect to Scottish females. More worn molars were associated with larger mandibles in both populations, suggesting that higher intake and/or greater investment in food comminution may have favoured increased body growth, before later loss of tooth efficiency due to severe wear. These results illustrate how independent selection in both subspecies, that diverged 11,700 years BP, has resulted in the evolution of different longevity, although sexual selection has maintained a similar pattern of relative sex differences in tooth depletion. This study opens interesting questions on optimal allocation in life history trade-offs and the independent evolution of allopatric populations.

Heightened sexual interest and sleep disturbance

NASA Technical Reports Server (NTRS)

Zarcone, V.; De La Pena, A.; Dement, W. C.

1974-01-01

The study demonstrates a behavioral effect of selective sleep disturbance in normal human subjects. Ten male subjects were selectively REM-deprived for two nights by awakening them at the onset of REM sleep. In addition, there were baseline and non-REM awakening conditions. Heightened sexual interest was defined by the number of film frames (using a Mackworth camera) in which subjects fixated on parts of the female figure in photographs. The largest mean difference in sexual interest was found between baseline and REM-deprivation. Both the non-REM awakenings and REM-sleep deprivation enhanced sexual interest. The failure to demonstrate a significant difference between REM-deprivation and non-REM awakenings may be due to the fact that subjects were REM-sleep-deprived in both conditions. It is suggested that REM-sleep loss may lead to increased selective attention and preoccupation with any cues which are usually interesting.

Adaptive genetic complementarity in mate choice coexists with selection for elaborate sexual traits

PubMed Central

Oh, Kevin P; Badyaev, Alexander V

2006-01-01

Choice of genetically unrelated mates is widely documented, yet it is not known how self-referential mate choice can co-occur with commonly observed directional selection on sexual displays. Across 10 breeding seasons in a wild bird population, we found strong fitness benefits of matings between genetically unrelated partners and show that self-referential choice of genetically unrelated mates alternates with sexual selection on elaborate plumage. Seasonal cycles of diminishing variation in ornamentation, caused by early pairing of the most elaborated males, and influx of increasingly genetically unrelated available mates caused by female-biased dispersal, lead to temporal fluctuations in the target of mate choice and enabled coexistence of directional selection for ornament elaboration with adaptive pairing of genetically unrelated partners. PMID:16822752

Widespread genetic linkage of mating signals and preferences in the Hawaiian cricket Laupala

PubMed Central

Wiley, Chris; Ellison, Christopher K.; Shaw, Kerry L.

2012-01-01

The evolution of novel sexual communication systems is integral to the process of speciation, as it discourages gene flow between incipient species. Physical linkage between genes underlying male–female communication (i.e. sexual signals and preferences for them) facilitates both rapid and coordinated divergence of sexual communication systems between populations and reduces recombination in the face of occasional hybridization between diverging populations. Despite these ramifications of the genetic architecture of sexual communication for sexual selection and speciation, few studies have examined this relationship empirically. Previous studies of the closely related Hawaiian crickets Laupala paranigra and Laupala kohalensis have indirectly suggested that many of the genes underlying the difference in pulse rate of male song are physically linked with genes underlying the difference in female preference for pulse rate. Using marker-assisted introgression, we moved ‘slow pulse rate’ alleles from L. paranigra at five known quantitative trait loci (QTL) underlying male pulse rate into the ‘fast pulse rate’ genetic background of L. kohalensis and assessed the effect of these loci on female preference. An astounding four out of five song QTL predicted the preferences of female fourth-generation backcrosses, providing direct evidence for the extensive genetic linkage of song and preference in one of the fastest diversifying genera currently known. PMID:21957135

Aging modulates cuticular hydrocarbons and sexual attractiveness in Drosophila melanogaster

PubMed Central

Kuo, Tsung-Han; Yew, Joanne Y.; Fedina, Tatyana Y.; Dreisewerd, Klaus; Dierick, Herman A.; Pletcher, Scott D.

2012-01-01

SUMMARY Attractiveness is a major component of sexual selection that is dependent on sexual characteristics, such as pheromone production, which often reflect an individual’s fitness and reproductive potential. Aging is a process that results in a steady decline in survival and reproductive output, yet little is known about its effect on specific aspects of attractiveness. In this report we asked how aging impacts pheromone production and sexual attractiveness in Drosophila melanogaster. Evidence suggests that key pheromones in Drosophila are produced as cuticular hydrocarbons (CHC), whose functions in attracting mates and influencing behavior have been widely studied. We employed gas chromatography/mass spectrometry and laser desorption/ionization mass spectrometry to show that the composition of D. melanogaster CHC is significantly affected by aging in both sexes and that these changes are robust to different genetic backgrounds. Aging affected the relative levels of many individual CHC, and it shifted overall hydrocarbon profiles to favor compounds with longer chain lengths. We also show that the observed aging-related changes in CHC profiles are responsible for a significant reduction in sexual attractiveness. These studies illuminate causal links among pheromones, aging and attractiveness and suggest that CHC production may be an honest indicator of animal health and fertility. PMID:22323204

Adapting and Validating a Scale to Measure Sexual Stigma among Lesbian, Bisexual and Queer Women

PubMed Central

Logie, Carmen H.; Earnshaw, Valerie

2015-01-01

Lesbian, bisexual and queer (LBQ) women experience pervasive sexual stigma that harms wellbeing. Stigma is a multi-dimensional construct and includes perceived stigma, awareness of negative attitudes towards one’s group, and enacted stigma, overt experiences of discrimination. Despite its complexity, sexual stigma research has generally explored singular forms of sexual stigma among LBQ women. The study objective was to develop a scale to assess perceived and enacted sexual stigma among LBQ women. We adapted a sexual stigma scale for use with LBQ women. The validation process involved 3 phases. First, we held a focus group where we engaged a purposively selected group of key informants in cognitive interviewing techniques to modify the survey items to enhance relevance to LBQ women. Second, we implemented an internet-based, cross-sectional survey with LBQ women (n=466) in Toronto, Canada. Third, we administered an internet-based survey at baseline and 6-week follow-up with LBQ women in Toronto (n=24) and Calgary (n=20). We conducted an exploratory factor analysis using principal components analysis and descriptive statistics to explore health and demographic correlates of the sexual stigma scale. Analyses yielded one scale with two factors: perceived and enacted sexual stigma. The total scale and subscales demonstrated adequate internal reliability (total scale alpha coefficient: 0.78; perceived sub-scale: 0.70; enacted sub-scale: 0.72), test-retest reliability, and construct validity. Perceived and enacted sexual stigma were associated with higher rates of depressive symptoms and lower self-esteem, social support, and self-rated health scores. Results suggest this sexual stigma scale adapted for LBQ women has good psychometric properties and addresses enacted and perceived stigma dimensions. The overwhelming majority of participants reported experiences of perceived sexual stigma. This underscores the importance of moving beyond a singular focus on discrimination to explore perceptions of social judgment, negative attitudes and social norms. PMID:25679391

Generational differences in the sexual communication process of African American grandparent and parent caregivers of adolescents.

PubMed

Cornelius, Judith B; Xiong, Pa H

2015-07-01

This study assessed generational differences in the sexual communication process between 40 African American parent and 40 grandparent caregivers of adolescent children. The study reports findings from a secondary analysis of data from two databases. The HIV Risk Reduction Survey was used to examine the sexual communication process. Grandparents wanted to talk about sex and had open sexual communications, while parents valued sexual abstinence and had limited communications. Based on the findings, healthcare providers and programs need to recognize that differences do exist between parents and grandparents with sexual communications. © 2015, Wiley Periodicals, Inc.

Handgrip Strength as a Darwinian Fitness Indicator in Men.

PubMed

Gallup, Andrew C; Fink, Bernhard

2018-01-01

Handgrip strength (HGS) is a robust measure of overall muscular strength and function, and has long been predictive of a multitude of health factors and physical outcomes for both men and women. The fact that HGS represents such a ubiquitous measure of health and vitality may reflect the significance of this trait during human evolution. This trait is also highly sexually dimorphic due to influences of androgenic hormones and fat-free body mass, suggesting that it has been further elaborated through sexual selection. Consistent with this view, research within evolutionary psychology and related fields has documented distinct relationships between HGS and measures of social and sexual behavior, especially in men. Here, we review studies across different societies and cultural contexts showing that male HGS predicts measures of aggression and social dominance, perceived formidability, male-typical body morphology and movement, courtship display, physical attractiveness, and sexual behavior and reproductive fitness. These findings underscore the value of including HGS as an independent measure within studies examining human sexual selection, and corroborate existing research suggesting that specific features of physical strength have and continue to be under positive directional selection in men.

Genetic basis and fitness correlates of dynamic carotenoid-based ornamental coloration in male and female common kestrels Falco tinnunculus.

PubMed

Vergara, P; Fargallo, J A; Martínez-Padilla, J

2015-01-01

Knowledge of the genetic basis of sexual ornaments is essential to understand their evolution through sexual selection. Although carotenoid-based ornaments have been instrumental in the study of sexual selection, given the inability of animals to synthesize carotenoids de novo, they are generally assumed to be influenced solely by environmental variation. However, very few studies have directly estimated the role of genes and the environment in shaping variation in carotenoid-based traits. Using long-term individual-based data, we here explore the evolutionary potential of a dynamic, carotenoid-based ornament (namely skin coloration), in male and female common kestrels. We first estimate the amount of genetic variation underlying variation in hue, chroma and brightness. After correcting for sex differences, the chroma of the orange-yellow eye ring coloration was significantly heritable (h2±SE=0.40±0.17), whereas neither hue (h2=0) nor brightness (h2=0.02) was heritable. Second, we estimate the strength and shape of selection acting upon chromatic (hue and chroma) and achromatic (brightness) variation and show positive and negative directional selection on female but not male chroma and hue, respectively, whereas brightness was unrelated to fitness in both sexes. This suggests that different components of carotenoid-based signals traits may show different evolutionary dynamics. Overall, we show that carotenoid-based coloration is a complex and multifaceted trait. If we are to gain a better understanding of the processes responsible for the generation and maintenance of variation in carotenoid-based coloration, these complexities need to be taken into account. © 2014 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

Is male rhesus macaque red color ornamentation attractive to females?

PubMed Central

Dubuc, Constance; Allen, William L.; Maestripieri, Dario; Higham, James P.

2014-01-01

Male sexually-selected traits can evolve through different mechanisms: conspicuous and colorful ornaments usually evolve through inter-sexual selection, while weapons usually evolve through intra-sexual selection. Male ornaments are rare among mammals in comparison to birds, leading to the notion that female mate choice generally plays little role in trait evolution in this taxon. Supporting this view, when ornaments are present in mammals they typically indicate social status and are products of male-male competition. This general mammalian pattern, however, may not apply to rhesus macaques (Macaca mulatta). Males of this species display conspicuous skin coloration, but this expression is not correlated to dominance rank, and is therefore unlikely to have evolved due to male-male competition. Here, we investigate whether male color expression influences female proceptivity towards males in the Cayo Santiago free-ranging rhesus macaque population. We collected face images of 24 adult males varying in dominance rank and age at the peak of the mating season, and modeled these to rhesus macaque visual perception. We also recorded female socio-sexual behaviors towards these males. Results show that dark red males received more sexual solicitations, by more females, than pale pink ones. Together with previous results, our study suggests that male color ornaments are more likely to be a product of inter- rather than intra-sexual selection. This may especially be the case in rhesus macaques due to the particular characteristics of male-male competition in this species. PMID:25246728

Sexually dichromatic coloration reflects size and immunocompetence in female Spanish terrapins, Mauremys leprosa

NASA Astrophysics Data System (ADS)

Ibáñez, Alejandro; Marzal, Alfonso; López, Pilar; Martín, José

2013-12-01

Many studies have shown the importance of colorful ornamentation in mate choosiness or intrasexual conflict. However, research on color ornaments has focused mainly on birds, lizards or fish, but remains practically unknown in other animal groups such as turtles. In addition, female ornaments and their relation with sexual selection also remain almost unknown. Here, we measured the coloration of the shell and the limb stripes of male and female Spanish terrapins Mauremys leprosa and explored the existence of sexual dichromatism and the relation of color characteristics with body size and health state estimated from the immune response to the injection of an antigen (phytohaemagglutinin test). Our results showed that shell coloration, which could be constrained by natural selection to be cryptic, changed with body size, but did not differ between sexes. In contrast, females had brighter and less ultraviolet-saturated and more orange-saturated limb stripes than males. In females, interindividual variation in limb stripe coloration was related with body size and immune response suggesting that this coloration may inform honestly about multiple traits that could be important in sexual selection. In contrast, coloration of limb stripes of males was duller than in females, and was not related with any trait suggesting that coloration is not important in sexual selection for males.

High temperatures disrupt Artemia franciscana mating patterns and impact sexual selection intensity

NASA Astrophysics Data System (ADS)

Santos, Maria R.; Vieira, Natividade; Monteiro, Nuno M.

2018-07-01

Temperature plays a critical role in survival and reproduction, especially in ectotherms. Therefore, it is important to understand the mechanisms influencing life history traits and reproductive behaviours in order to predict climate change impacts on species' occurrence and performance. Here, we used the crustacean Artemia franciscana to investigate the potential impacts of temperature on life history traits, mating patterns and intensity of sexual selection. We reared A. franciscana at three temperatures 20 °C, 25 °C, and 30 °C and measured life history traits such as growth, mortality or development of sexual traits. Our observations confirmed a clear link between life history traits and temperature, with advanced sexual maturity and increased mortality rates following temperature rises. Also, we found that mating is size assortative close to the ideal developmental temperature. Nevertheless, when temperatures deviate from the optimum, mating patterns were altered. Although selection intensity for females remained similar at all tested temperatures, as males preferentially mated with the larger females, size assortative mating disappeared at the highest temperature. Overall, our results highlight the potential for a temperature-dependent disruption of A. franciscana mating patterns. This disruption is especially pronounced under high temperatures as reproduction becomes progressively more random, thus entailing a relaxation of sexual selection intensity.

Selection in a fluctuating environment and the evolution of sexual dimorphism in the seed beetle Callosobruchus maculatus.

PubMed

Hallsson, L R; Björklund, M

2012-08-01

Temperature changes in the environment, which realistically include environmental fluctuations, can create both plastic and evolutionary responses of traits. Sexes might differ in either or both of these responses for homologous traits, which in turn has consequences for sexual dimorphism and its evolution. Here, we investigate both immediate changes in and the evolution of sexual dimorphism in response to a changing environment (with and without fluctuations) using the seed beetle Callosobruchus maculatus. We investigate sex differences in plasticity and also the genetic architecture of body mass and developmental time dimorphism to test two existing hypotheses on sex differences in plasticity (adaptive canalization hypothesis and condition dependence hypothesis). We found a decreased sexual size dimorphism in higher temperature and that females responded more plastically than males, supporting the condition dependence hypothesis. However, selection in a fluctuating environment altered sex-specific patterns of genetic and environmental variation, indicating support for the adaptive canalization hypothesis. Genetic correlations between sexes (r(MF) ) were affected by fluctuating selection, suggesting facilitated independent evolution of the sexes. Thus, the selective past of a population is highly important for the understanding of the evolutionary dynamics of sexual dimorphism. © 2012 The Authors. Journal of Evolutionary Biology © 2012 European Society For Evolutionary Biology.

A selective androgen receptor modulator with minimal prostate hypertrophic activity enhances lean body mass in male rats and stimulates sexual behavior in female rats.

PubMed

Allan, George F; Tannenbaum, Pamela; Sbriscia, Tifanie; Linton, Olivia; Lai, Muh-Tsann; Haynes-Johnson, Donna; Bhattacharjee, Sheela; Zhang, Xuqing; Sui, Zhihua; Lundeen, Scott G

2007-08-01

Androgen receptor (AR) ligands with tissue selectivity (selective androgen receptor modulators, or SARMs) have potential for treating muscle wasting, hypogonadism of aging, osteoporosis, female sexual dysfunction, and other indications. JNJ-28330835 is a nonsteroidal AR ligand with mixed agonist and antagonist activity in androgen-responsive cell-based assays. It is an orally active SARM with muscle selectivity in orchidectomized rat models. It stimulated growth of the levator ani muscle, stimulating maximal growth at a dose of 10 mg/kg. At the same time, JNJ-28330835 reduced prostate weight in intact rats by a mean of 30% at 10 mg/kg, while having no inhibitory effect on muscle. Using magnetic resonance imaging (MRI) to monitor body composition, it prevented half of the loss of lean body mass associated with orchidectomy, and restored about 30% of lost lean mass to aged orchidectomized rats. It had agonist effects on markers of both osteoclast and osteoblast activity, suggesting that it reduces bone turnover. In a model of sexual behavior, JNJ-28330835 enhanced the preference of ovariectomized female rats for sexually intact male rats over nonsexual orchidectomized males. JNJ-28330835 is a prostate-sparing SARM with the potential for clinically beneficial effects in muscle-wasting diseases and sexual function disorders.

Standard symptom- and sexual history-based testing misses anorectal Chlamydia trachomatis and neisseria gonorrhoeae infections in swingers and men who have sex with men.

PubMed

van Liere, Geneviève A F S; Hoebe, Christian J P A; Niekamp, Anne-Marie; Koedijk, Femke D H; Dukers-Muijrers, Nicole H T M

2013-04-01

Currently, individuals at risk for sexually transmitted diseases (STDs) are tested extragenitally only if indicated, most often when there is a history of self-reported symptoms or self-reported anal sex. The sensitivity of such selective symptom- and sexual history-based testing for detection of anorectal STD has not been determined. All men having sex with men (MSM) and swingers (heterosexual couples who have sex with other heterosexual couples and their self-identified heterosexual sex partners) attending our STD clinic (consults: n = 1690) from January 2010 until February 2011 were universally tested for urogenital, anorectal, and oropharyngeal Chlamydia trachomatis and Neisseria gonorrhoeae infections (STD). We compared STD prevalence at anorectal site based on universal versus selective testing. Sensitivity of selective symptom- and sexual history-based testing for anorectal STD was 52% for homosexual MSM, 40% for bisexual MSM, 43% for bisexual male swingers, 40% for heterosexual male swingers, and 47% for female swingers. Universal testing of STD clinic clients who were MSM and swingers yielded more than half of all anorectal STD infections and is more sensitive for identifying anorectal STD infections compared with selective testing. Universal testing may be a more effective strategy for interrupting the ongoing transmission in high-risk sexual networks.

Genome-wide selection components analysis in a fish with male pregnancy.

PubMed

Flanagan, Sarah P; Jones, Adam G

2017-04-01

A major goal of evolutionary biology is to identify the genome-level targets of natural and sexual selection. With the advent of next-generation sequencing, whole-genome selection components analysis provides a promising avenue in the search for loci affected by selection in nature. Here, we implement a genome-wide selection components analysis in the sex role reversed Gulf pipefish, Syngnathus scovelli. Our approach involves a double-digest restriction-site associated DNA sequencing (ddRAD-seq) technique, applied to adult females, nonpregnant males, pregnant males, and their offspring. An F ST comparison of allele frequencies among these groups reveals 47 genomic regions putatively experiencing sexual selection, as well as 468 regions showing a signature of differential viability selection between males and females. A complementary likelihood ratio test identifies similar patterns in the data as the F ST analysis. Sexual selection and viability selection both tend to favor the rare alleles in the population. Ultimately, we conclude that genome-wide selection components analysis can be a useful tool to complement other approaches in the effort to pinpoint genome-level targets of selection in the wild. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

Design and integration of ethnography within an international behavior change HIV/sexually transmitted disease prevention trial

PubMed Central

2008-01-01

Objective To use a common ethnographic study protocol across five countries to provide data to confirm social and risk settings and risk behaviors, develop the assessment instruments, tailor the intervention, design a process evaluation of the intervention, and design an understandable informed consent process. Design Methods determined best for capturing the core data elements were selected. Standards for data collection methods were established to enable comparable implementation of the ethnographic study across the five countries. Methods The methods selected were participant observation, focus groups, open-ended interviews, and social mapping. Standards included adhering to core data elements, number of participants, mode of data collection, type of data collection instrument, number of data collectors at each type of activity, duration of each type of activity, and type of informed consent administered. Sites had discretion in selecting which methods to use to obtain specific data. Results The ethnographic studies provided input to the Trial’s methods for data collection, described social groups in the target communities, depicted sexual practices, and determined core opinion leader characteristics; thus providing information that drove the adaptation of the intervention and facilitated the selection of venues, behavioral outcomes, and community popular opinion leaders (C-POLs). Conclusion The described rapid ethnographic approach worked well across the five countries, where findings allowed local adaptation of the intervention. When introducing the C-POL intervention in new areas, local non-governmental and governmental community and health workers can use this rapid ethnographic approach to identify the communities, social groups, messages, and C-POLs best suited for local implementation. PMID:17413263

Bateman's principle is reversed in a cooperatively breeding bird.

PubMed

Apakupakul, Kathleen; Rubenstein, Dustin R

2015-04-01

Bateman's principle is not only used to explain sex differences in mating behaviour, but also to determine which sex has the greater opportunity for sexual selection. It predicts that the relationship between the number of mates and the number of offspring produced should be stronger for males than for females. Yet, it is unclear whether Bateman's principle holds in cooperatively breeding systems where the strength of selection on traits used in intrasexual competition is high in both sexes. We tested Bateman's principle in the cooperatively breeding superb starling (Lamprotornis superbus), finding that only females showed a significant, positive Bateman gradient. We also found that the opportunity for selection was on average higher in females, but that its strength and direction oscillated through time. These data are consistent with the hypothesis that sexual selection underlies the female trait elaboration observed in superb starlings and other cooperative breeders. Even though the Bateman gradient was steeper for females than for males, the year-to-year oscillation in the strength and direction of the opportunity for selection likely explains why cooperative breeders do not exhibit sexual role reversal. Thus, Bateman's principle may not hold in cooperative breeders where both sexes appear to be under mutually strong sexual selection. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Potential fitness benefits from mate selection in the Atlantic cod (Gadus morhua).

PubMed

Rudolfsen, G; Figenschou, L; Folstad, I; Nordeide, J T; Søreng, E

2005-01-01

Little evidence of benefits from female mate choice has been found when males provide no parental care or resources. Yet, good genes models of sexual selection suggest that elaborated male sexual characters are reliable signals of mate quality and that the offspring of males with elaborate sexual ornaments will perform better than those of males with less elaborate ornaments. We used cod (Gadus morhua L.), an externally fertilizing species where males provide nothing but sperm, to examine the potential of optimal mate selection with respect to offspring survival. By applying in vitro fertilizations, we crossed eight females with nine males in all possible combinations and reared each of the 72 sib groups. We found that offspring survival was dependent on which female was mated with which male and that optimal mate selection has the potential to increase mean offspring survival from 31.9 to 55.6% (a 74% increase). However, the size of the male sexual ornaments and sperm quality (i.e. sperm velocity and sperm density) could not predict offspring survival. Thus, even if there may be large fitness benefits of mate selection, we might not yet have identified the male characteristics generating high offspring survival.

Postcopulatory sexual selection influences baculum evolution in primates and carnivores.

PubMed

Brindle, Matilda; Opie, Christopher

2016-12-14

The extreme morphological variability of the baculum across mammals is thought to be the result of sexual selection (particularly, high levels of postcopulatory selection). However, the evolutionary trajectory of the mammalian baculum is little studied and evidence for the adaptive function of the baculum has so far been elusive. Here, we use Markov chain Monte Carlo methods implemented in a Bayesian phylogenetic framework to reconstruct baculum evolution across the mammalian class and investigate the rate of baculum length evolution within the primate order. We then test the effects of testes mass (postcopulatory sexual selection), polygamy, seasonal breeding and intromission duration on the baculum in primates and carnivores. The ancestral mammal did not have a baculum, but both ancestral primates and carnivores did. No relationship was found between testes mass and baculum length in either primates or carnivores. Intromission duration correlated with baculum presence over the course of primate evolution, and prolonged intromission predicts significantly longer bacula in extant primates and carnivores. Both polygamous and seasonal breeding systems predict significantly longer bacula in primates. These results suggest the baculum plays an important role in facilitating reproductive strategies in populations with high levels of postcopulatory sexual selection. © 2016 The Authors.

Postcopulatory sexual selection influences baculum evolution in primates and carnivores

PubMed Central

Brindle, Matilda

2016-01-01

The extreme morphological variability of the baculum across mammals is thought to be the result of sexual selection (particularly, high levels of postcopulatory selection). However, the evolutionary trajectory of the mammalian baculum is little studied and evidence for the adaptive function of the baculum has so far been elusive. Here, we use Markov chain Monte Carlo methods implemented in a Bayesian phylogenetic framework to reconstruct baculum evolution across the mammalian class and investigate the rate of baculum length evolution within the primate order. We then test the effects of testes mass (postcopulatory sexual selection), polygamy, seasonal breeding and intromission duration on the baculum in primates and carnivores. The ancestral mammal did not have a baculum, but both ancestral primates and carnivores did. No relationship was found between testes mass and baculum length in either primates or carnivores. Intromission duration correlated with baculum presence over the course of primate evolution, and prolonged intromission predicts significantly longer bacula in extant primates and carnivores. Both polygamous and seasonal breeding systems predict significantly longer bacula in primates. These results suggest the baculum plays an important role in facilitating reproductive strategies in populations with high levels of postcopulatory sexual selection. PMID:27974519

Does Endometriosis Affect Sexual Activity and Satisfaction of the Man Partner? A Comparison of Partners From Women Diagnosed With Endometriosis and Controls.

PubMed

Hämmerli, Silvan; Kohl Schwartz, Alexandra Sabrina; Geraedts, Kirsten; Imesch, Patrick; Rauchfuss, Martina; Wölfler, Monika Maria; Haeberlin, Felix; von Orelli, Stefanie; Eberhard, Markus; Imthurn, Bruno; Leeners, Brigitte

2018-06-01

Endometriosis-associated pain and dyspareunia influence female sexuality, but little is known about men's experiences in affected couples. To investigate how men partners experience sexuality in partnership with women with endometriosis. A multi-center case-control study was performed between 2010 and 2015 in Switzerland, Germany, and Austria. 236 Partners of endometriosis patients and 236 partners of age-matched control women without endometriosis with a similar ethnic background were asked to answer selected, relevant questions of the Brief Index of Sexual Functioning and the Global Sexual Functioning questionnaire, as well as some investigator-derived questions. We sought to evaluate sexual satisfaction of men partners of endometriosis patients, investigate differences in sexual activities between men partners of women with and without endometriosis, and identify options to improve partnership sexuality in couples affected by endometriosis. Many partners of endometriosis patients reported changes in sexuality (75%). A majority of both groups was (very) satisfied with their sexual relationship (73.8% vs 58.1%, P = .002). Nevertheless, more partners of women diagnosed with endometriosis were not satisfied (P = .002) and their sexual problems more strongly interfered with relationship happiness (P = .001) than in partners of control women. Frequencies of sexual intercourse (P < .001) and all other partnered sexual activities (oral sex, petting) were significantly higher in the control group. The wish for an increased frequency of sexual activity (P = .387) and sexual desire (P = .919) did not differ statistically between both groups. There is a need to evaluate qualitative factors that influence sexual satisfaction in endometriosis patients. This is one of the first studies to investigate male sexuality affected by endometriosis. The meticulous verification of diagnosis and disease stage according to operation reports and histology allows for a high reliability of diagnosis. Our men's response rate of almost 50% is higher compared to other studies. Recruiting men through their woman partner may have caused selection bias. The adjustment to the specific situation in endometriosis by selecting questions from the Brief Index of Sexual Functioning and Global Sexual Functioning and adding investigator-derived questions likely influenced the validity of the questionnaires. Despite the fact that both partners of endometriosis patients and of control women largely reported high sexual satisfaction, there are challenges for some couples that arise in the context of a sexual relationship when one partner has endometriosis. Challenges such as sexuality-related pain or a reduced frequency of sexual activities should be addressed by health care professionals to ameliorate any current difficulties and to prevent the development or aggravation of sexual dysfunction. Hämmerli S, Kohl Schwartz AS, Geraedts K, et al. Does Endometriosis Affect Sexual Activity and Satisfaction of the Man Partner? A Comparison of Partners From Women Diagnosed With Endometriosis and Controls. J Sex Med 2018;15:853-865. Copyright © 2018 International Society for Sexual Medicine. Published by Elsevier Inc. All rights reserved.

Sexual Response Models: Toward a More Flexible Pattern of Women's Sexuality.

PubMed

Ferenidou, Fotini; Kirana, Paraskevi-Sofia; Fokas, Konstantinos; Hatzichristou, Dimitrios; Athanasiadis, Loukas

2016-09-01

Recent research suggests that none of the current theoretical models can sufficiently describe women's sexual response, because several factors and situations can influence this. To explore individual variations of a sexual model that describes women's sexual responses and to assess the association of endorsement of that model with sexual dysfunctions and reasons to engage in sexual activity. A sample of 157 randomly selected hospital employees completed self-administered questionnaires. Two models were developed: one merged the Master and Johnson model with the Kaplan model (linear) and the other was the Basson model (circular). Sexual function was evaluated by the Female Sexual Function Index and the Brief Sexual Symptom Checklist for Women. The Reasons for Having Sex Questionnaire was administered to investigate the reasons for which women have sex. Women reported that their current sexual experiences were at times consistent with the linear and circular models (66.9%), only the linear model (27%), only the circular model (5.4%), and neither model (0.7%). When the groups were reconfigured to the group that endorsed more than 5 of 10 sexual experiences, 64.3% of women endorsed the linear model, 20.4% chose the linear and circular models, 14.6% chose the circular model, and 0.7% selected neither. The Female Sexual Function Index, demographic factors, having sex for insecurity reasons, and sexual satisfaction correlated with the endorsement of a sexual response model. When these factors were entered in a stepwise logistic regression analysis, only the Female Sexual Function Index and having sex for insecurity reasons maintained a significant association with the sexual response model. The present study emphasizes the heterogeneity of female sexuality, with most of the sample reporting alternating between the linear and circular models. Sexual dysfunctions and having sex for insecurity reasons were associated with the Basson model. Copyright © 2016 International Society for Sexual Medicine. Published by Elsevier Inc. All rights reserved.

Comparing Help-Seeking Behavior of Male and Female Survivors of Sexual Assault: A Content Analysis of a Hotline.

PubMed

Young, Stephen M; Pruett, Jana A; Colvin, Marianna L

2018-06-01

This content analysis examines written documentation of telephone calls to a regional sexual assault hotline over a 5-year period. All male callers identified as primary victims were selected for analysis ( n = 58) and a corresponding sample of female primary victims ( n = 58) were randomly selected for comparison to better understand the help-seeking behavior of sexual assault survivors and inform services accordingly. A summative content analysis revealed significant contrasting themes between male and female victims, including females significantly receiving more referrals and males accessing the hotline to tell their experience of being sexually assaulted due to perceived limited support. Implications for training, practice, and future research are discussed.

Seasonal dimorphism in the horny bills of sparrows

EPA Science Inventory

Bill shape and size are often viewed as species-specific adaptations for feeding, but they sometimes vary between sexes, suggesting that sexual selection or inter-sexual competition may also be important. Hypotheses to explain sexual bill size dimorphism in birds avian bill size...

Sexual and ethnic identity development among gay-bisexual-questioning (GBQ) male ethnic minority adolescents.

PubMed

Jamil, Omar B; Harper, Gary W; Fernandez, M Isabel

2009-07-01

Identity development is a critical task of adolescence and occurs across multiple areas of self-identification. Although research on the identity development process among individuals who are ethnic and sexual minorities has been conducted for individuals who have 1 minority status or the other, few studies have examined these processes in people who are both ethnic and sexual minorities. In this qualitative study, the authors examined the dual identity development processes related to ethnic and sexual identity among gay-bisexual-questioning (GBQ) Latino and African American male adolescents. Results indicated that the processes associated with the development of sexual orientation and ethnic identity occur concurrently. However, the actual processes involved with the development of each identity not only differed, but seemed to be independent of each other because neither process was referenced in the development of the other. Overall, the process of ethnic identity development involved the process of becoming aware of one's ethnic and cultural heritage, whereas sexual identity development involved finding one's own personally relevant sexual orientation label and connecting to that community. The implications of these findings for the development of interventions to assist in the healthy development of GBQ adolescents are discussed.

Sexual and Ethnic Identity Development among Gay/Bisexual/Questioning (GBQ) Male Ethnic Minority Adolescents

PubMed Central

Jamil, Omar B.; Harper, Gary W.; Fernandez, M. Isabel

2010-01-01

Identity development is a critical task of adolescence and occurs across multiple areas of self identification. Though research on the identity development process among individuals who are ethnic and sexual minorities has been conducted for individuals who have one minority status or the other, few studies have examined these processes in persons who are both ethnic and sexual minorities. This qualitative study examined the dual identity development processes related to ethnic and sexual identity among gay/bisexual/questioning (GBQ) Latino and African American male adolescents. Results indicated that the processes associated with the development of sexual orientation and ethnic identity occur concurrently. However, the actual processes involved with the development of each identity not only differed, but seemed to be independent of each other since neither process was referenced in the development of the other. Overall, the process of ethnic identity development involved the process of becoming aware of one’s ethnic and cultural heritage, while sexual identity development involved finding one’s own personally relevant sexual orientation label and connecting to that community. The implications of these findings for the development of interventions to assist in the healthy development of GBQ adolescents are discussed. PMID:19594249

Evolutionary Trade-Off between Secondary Sexual Traits and Ejaculates.

PubMed

Simmons, Leigh W; Lüpold, Stefan; Fitzpatrick, John L

2017-12-01

Recent theoretical models predict that the evolutionary diversification of the weapons and ornaments of pre-mating sexual selection should be influenced by trade-offs with male expenditure on ejaculates. However, the patterns of association between secondary sexual traits and ejaculate expenditure are frequently inconsistent in their support of this prediction. We show why consideration of additional life-history, ecological, and mating-system variables is crucial for the interpretation of associations between secondary sexual traits and ejaculate production. Incorporation of these 'missing variables' provides evidence that interactions between pre- and post-mating sexual selection can underlie broad patterns of diversification in male weapons and ornaments. We call for more experimental and genetic approaches to uncover trade-offs, as well as for studies that consider the costs of mate-searching. Copyright © 2017 Elsevier Ltd. All rights reserved.

A comparative test of adaptive hypotheses for sexual size dimorphism in lizards.

PubMed

Cox, Robert M; Skelly, Stephanie L; John-Alder, Henry B

2003-07-01

It is commonly argued that sexual size dimorphism (SSD) in lizards has evolved in response to two primary, nonexclusive processes: (1) sexual selection for large male size, which confers an advantage in intrasexual mate competition (intrasexual selection hypothesis), and (2) natural selection for large female size, which confers a fecundity advantage (fecundity advantage hypothesis). However, outside of several well-studied lizard genera, the empirical support for these hypotheses has not been examined with appropriate phylogenetic control. We conducted a comparative phylogenetic analysis to test these hypotheses using literature data from 497 lizard populations representing 302 species and 18 families. As predicted by the intrasexual selection hypothesis, male aggression and territoriality are correlated with SSD, but evolutionary shifts in these categorical variables each explain less than 2% of the inferred evolutionary change in SSD. We found stronger correlations between SSD and continuous estimates of intrasexual selection such as male to female home range ratio and female home range size. These results are consistent with the criticism that categorical variables may obscure much of the actual variation in intrasexual selection intensity needed to explain patterns in SSD. In accordance with the fecundity advantage hypothesis, SSD is correlated with clutch size, reproductive frequency, and reproductive mode (but not fecundity slope, reduced major axis estimator of fecundity slope, length of reproductive season, or latitude). However, evolutionary shifts in clutch size explain less than 8% of the associated change in SSD, which also varies significantly in the absence of evolutionary shifts in reproductive frequency and mode. A multiple regression model retained territoriality and clutch size as significant predictors of SSD, but only 16% of the variation in SSD is explained using these variables. Intrasexual selection for large male size and fecundity selection for large female size have undoubtedly helped to shape patterns of SSD across lizards, but the comparative data at present provide only weak support for these hypotheses as general explanations for SSD in this group. Future work would benefit from the consideration of alternatives to these traditional evolutionary hypotheses, and the elucidation of proximate mechanisms influencing growth and SSD within populations.

Mating systems and sexual selection in male-pregnant pipefishes and seahorses: insights from microsatellite-based studies of maternity.

PubMed

Jones, A G; Avise, J C

2001-01-01

In pipefishes and seahorses (family Syngnathidae), the males provide all postzygotic care of offspring by brooding embryos on their ventral surfaces. In some species, this phenomenon of male "pregnancy" results in a reversal of the usual direction of sexual selection, such that females compete more than males for access to mates, and secondary sexual characteristics evolve in females. Thus the syngnathids can provide critical tests of theories related to the evolution of sex differences and sexual selection. Microsatellite-based studies of the genetic mating systems of several species of pipefishes and seahorses have provided insights into important aspects of the natural history and evolution of these fishes. First, males of species with completely enclosed pouches have complete confidence of paternity, as might be predicted from parental investment theory for species in which males invest so heavily in offspring. Second, a wide range of genetic mating systems have been documented in nature, including genetic monogamy in a seahorse, polygynandry in two species of pipefish, and polyandry in a third pipefish species. The genetic mating systems appear to be causally related to the intensity of sexual selection, with secondary sex characters evolving most often in females of the more polyandrous species. Third, genetic studies of captive-breeding pipefish suggest that the sexual selection gradient (or Bateman gradient) may be a substantially better method for characterizing the mating system than previously available techniques. Finally, these genetic studies of syngnathid mating systems have led to some general insights into the occurrence of clustered mutations at microsatellite loci, the utility of linked loci in studies of parentage, and the use of parentage data for direct estimation of adult population size.

Sexual signals and mating patterns in Syngnathidae.

PubMed

Rosenqvist, G; Berglund, A

2011-06-01

Male pregnancy in the family Syngnathidae (pipefishes, seahorses and seadragons) predisposes males to limit female reproductive success; sexual selection may then operate more strongly on females and female sexual signals may evolve (sex-role reversal). A bewildering array of female signals has evolved in Syngnathids, e.g. skin folds, large body size, colouration, markings on the body and elaborate courtship. These female sexual signals do not seem quantitatively or qualitatively different from those that evolve in males in species with conventional sex roles where males provide females or offspring with direct benefits. In several syngnathid species, males also evolve ornaments, females are choosy in addition to being competitive and males compete as well as choosing partners. Thus, sex roles form a continuum, spanning from conventional to reversed within this group of fishes. Cases are presented here suggesting that stronger sexual selection on females may be most extreme in species showing classical polyandry (one male mates with several females, such as many species where males brood their eggs on the trunk), intermediate in polygynandrous species (males and females both mate with more than one partner, as in many species where males brood their eggs on the tail) and least extreme, even exhibiting conventional sex roles, in monogamous species (one male mates solely with one female, as in many seahorses and tropical pipefishes). At the same time caution is needed before unanimously establishing this pattern: first, the connection between mating patterns, strength of sexual selection, sex roles and ornament expression is far from simple and straightforward, and second, knowledge of the actual morphology, ecology and behaviour of most syngnathid species is scanty. Basically only a few Nerophis, Syngnathus and Hippocampus species have been studied in any detail. It is known, however, that this group of fishes exhibits a remarkable variation in sex roles and ornamentation, making them an ideal group for the study of mating patterns, sexual selection and sexually selected signals. © 2011 The Authors. Journal of Fish Biology © 2011 The Fisheries Society of the British Isles.

Sperm Bindin Divergence under Sexual Selection and Concerted Evolution in Sea Stars.

PubMed

Patiño, Susana; Keever, Carson C; Sunday, Jennifer M; Popovic, Iva; Byrne, Maria; Hart, Michael W

2016-08-01

Selection associated with competition among males or sexual conflict between mates can create positive selection for high rates of molecular evolution of gamete recognition genes and lead to reproductive isolation between species. We analyzed coding sequence and repetitive domain variation in the gene encoding the sperm acrosomal protein bindin in 13 diverse sea star species. We found that bindin has a conserved coding sequence domain structure in all 13 species, with several repeated motifs in a large central region that is similar among all sea stars in organization but highly divergent among genera in nucleotide and predicted amino acid sequence. More bindin codons and lineages showed positive selection for high relative rates of amino acid substitution in genera with gonochoric outcrossing adults (and greater expected strength of sexual selection) than in selfing hermaphrodites. That difference is consistent with the expectation that selfing (a highly derived mating system) may moderate the strength of sexual selection and limit the accumulation of bindin amino acid differences. The results implicate both positive selection on single codons and concerted evolution within the repetitive region in bindin divergence, and suggest that both single amino acid differences and repeat differences may affect sperm-egg binding and reproductive compatibility. © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Sexual selection and the evolution of male pheromone glands in philanthine wasps (Hymenoptera, Crabronidae).

PubMed

Weiss, Katharina; Herzner, Gudrun; Strohm, Erhard

2017-06-06

Sexual selection is thought to promote evolutionary changes and diversification. However, the impact of sexual selection in relation to other selective forces is difficult to evaluate. Male digger wasps of the tribe Philanthini (Hymenoptera, Philanthinae) scent mark territories to attract receptive females. Consequently, the organs for production and storage of the marking secretion, the mandibular gland (MG) and the postpharyngeal gland (PPG), are subject to sexual selection. In female Philanthini, these glands are most likely solely subject to natural selection and show very little morphological diversity. According to the hypothesis that sexual selection drives interspecific diversity, we predicted that the MG and PPG show higher interspecific variation in males than in females. Using histological methods, 3D-reconstructions, and multivariate statistical analysis of morphological characters, we conducted a comparative analysis of the MG and the PPG in males of 30 species of Philanthini and three species of the Cercerini and Aphilanthopsini, two related tribes within the Philanthinae. We found substantial interspecific diversity in gland morphology with regard to gland incidence, size, shape and the type of associated secretory cells. Overall there was a phylogenetic trend: Ensuing from the large MGs and small PPGs of male Cercerini and Aphilanthopsini, the size and complexity of the MG was reduced in male Philanthini, while their PPG became considerably enlarged, substantially more complex, and associated with an apparently novel type of secretory cells. In some clades of the Philanthini the MG was even lost and entirely replaced by the PPG. However, several species showed reversals of and exceptions from this trend. Head gland morphology was significantly more diverse among male than among female Philanthinae. Our results show considerable variation in male head glands including the loss of an entire gland system and the evolution of a novel kind of secretory cells, confirming the prediction that interspecific diversity in head gland morphology is higher in male than in female Philanthini. We discuss possible causes for the remarkable evolutionary changes in males and we conclude that this high diversity has been caused by sexual selection.

Natural and sexual selection in a monogamous historical human population.

PubMed

Courtiol, Alexandre; Pettay, Jenni E; Jokela, Markus; Rotkirch, Anna; Lummaa, Virpi

2012-05-22

Whether and how human populations exposed to the agricultural revolution are still affected by Darwinian selection remains controversial among social scientists, biologists, and the general public. Although methods of studying selection in natural populations are well established, our understanding of selection in humans has been limited by the availability of suitable datasets. Here, we present a study comparing the maximum strengths of natural and sexual selection in humans that includes the effects of sex and wealth on different episodes of selection. Our dataset was compiled from church records of preindustrial Finnish populations characterized by socially imposed monogamy, and it contains a complete distribution of survival, mating, and reproductive success for 5,923 individuals born 1760-1849. Individual differences in early survival and fertility (natural selection) were responsible for most variation in fitness, even among wealthier individuals. Variance in mating success explained most of the higher variance in reproductive success in males compared with females, but mating success also influenced reproductive success in females, allowing for sexual selection to operate in both sexes. The detected opportunity for selection is in line with measurements for other species but higher than most previous reports for human samples. This disparity results from biological, demographic, economic, and social differences across populations as well as from failures by most previous studies to account for variation in fitness introduced by nonreproductive individuals. Our results emphasize that the demographic, cultural, and technological changes of the last 10,000 y did not preclude the potential for natural and sexual selection in our species.

Natural and sexual selection in a monogamous historical human population

PubMed Central

Courtiol, Alexandre; Pettay, Jenni E.; Jokela, Markus; Rotkirch, Anna; Lummaa, Virpi

2012-01-01

Whether and how human populations exposed to the agricultural revolution are still affected by Darwinian selection remains controversial among social scientists, biologists, and the general public. Although methods of studying selection in natural populations are well established, our understanding of selection in humans has been limited by the availability of suitable datasets. Here, we present a study comparing the maximum strengths of natural and sexual selection in humans that includes the effects of sex and wealth on different episodes of selection. Our dataset was compiled from church records of preindustrial Finnish populations characterized by socially imposed monogamy, and it contains a complete distribution of survival, mating, and reproductive success for 5,923 individuals born 1760–1849. Individual differences in early survival and fertility (natural selection) were responsible for most variation in fitness, even among wealthier individuals. Variance in mating success explained most of the higher variance in reproductive success in males compared with females, but mating success also influenced reproductive success in females, allowing for sexual selection to operate in both sexes. The detected opportunity for selection is in line with measurements for other species but higher than most previous reports for human samples. This disparity results from biological, demographic, economic, and social differences across populations as well as from failures by most previous studies to account for variation in fitness introduced by nonreproductive individuals. Our results emphasize that the demographic, cultural, and technological changes of the last 10,000 y did not preclude the potential for natural and sexual selection in our species. PMID:22547810

Men and Sexuality: Bibliography of Selected Resources.

ERIC Educational Resources Information Center

Planned Parenthood Federation of America, Inc., New York, NY. Education Dept.

This selective, annotated bibliography covers a range of topics associated with male sexuality, reproductive health, and sexism. The books listed in this document are organized in five categories which are not strictly exclusive, as most of the entries overlap topic areas. Part I, Men in Society, contains 10 entries dealing with masculinity,…

Selections from Unequal Partners: Teaching about Power, Consent, and Healthy Relationships

ERIC Educational Resources Information Center

deFur, Kirsten

2016-01-01

The Center for Sex Education recently published the fourth edition of "Unequal Partners: Teaching about Power, Consent, and Healthy Relationships, Volumes 1 and 2." Included here are two lesson plans about sexual consent selected from each volume. "What does it take … to give sexual consent?" [Sue Montfort and Peggy Brick] is…

Positive feedback in the transition from sexual reproduction to parthenogenesis

PubMed Central

Schwander, Tanja; Vuilleumier, Séverine; Dubman, Janie; Crespi, Bernard J.

2010-01-01

Understanding how new phenotypes evolve is challenging because intermediate stages in transitions from ancestral to derived phenotypes often remain elusive. Here we describe and evaluate a new mechanism facilitating the transition from sexual reproduction to parthenogenesis. In many sexually reproducing species, a small proportion of unfertilized eggs can hatch spontaneously (‘tychoparthenogenesis’) and develop into females. Using an analytical model, we show that if females are mate-limited, tychoparthenogenesis can result in the loss of males through a positive feedback mechanism whereby tychoparthenogenesis generates female-biased sex ratios and increasing mate limitation. As a result, the strength of selection for tychoparthenogenesis increases in concert with the proportion of tychoparthenogenetic offspring in the sexual population. We then tested the hypothesis that mate limitation selects for tychoparthenogenesis and generates female-biased sex ratios, using data from natural populations of sexually reproducing Timema stick insects. Across 41 populations, both the tychoparthenogenesis rates and the proportions of females increased exponentially as the density of individuals decreased, consistent with the idea that low densities of individuals result in mate limitation and selection for reproductive insurance through tychoparthenogenesis. Our model and data from Timema populations provide evidence for a simple mechanism through which parthenogenesis can evolve rapidly in a sexual population. PMID:20071382

A link between altruism and sexual selection: genetic influence on altruistic behaviour and mate preference towards it.

PubMed

Phillips, Tim; Ferguson, Eamonn; Rijsdijk, Fruhling

2010-11-01

Altruistic behaviour raises major questions for psychology and biology. One hypothesis proposes that human altruistic behaviour evolved as a result of sexual selection. Mechanisms that seek to explain how sexual selection works suggest genetic influence acting on both the mate preference for the trait and the preferred trait itself. We used a twin study to estimate whether genetic effects influenced responses to psychometric scales measuring mate preference towards altruistic traits (MPAT) and the preferred trait (i.e., 'altruistic personality'). As predicted, we found significant genetic effects influencing variation in both. We also predicted that individuals expressing stronger MPAT and 'altruistic personality' would have mated at a greater frequency in ancestral populations. We found evidence for this in that 67% of the covariance in the phenotypic correlation between the two scales was associated with significant genetic effects. Both sets of findings are thus consistent with the hypothesized link between sexual selection and human altruism towards non-kin. We discuss how this study contributes to our understanding of altruistic behaviour and how further work might extend this understanding.

Human face processing is tuned to sexual age preferences

PubMed Central

Ponseti, J.; Granert, O.; van Eimeren, T.; Jansen, O.; Wolff, S.; Beier, K.; Deuschl, G.; Bosinski, H.; Siebner, H.

2014-01-01

Human faces can motivate nurturing behaviour or sexual behaviour when adults see a child or an adult face, respectively. This suggests that face processing is tuned to detecting age cues of sexual maturity to stimulate the appropriate reproductive behaviour: either caretaking or mating. In paedophilia, sexual attraction is directed to sexually immature children. Therefore, we hypothesized that brain networks that normally are tuned to mature faces of the preferred gender show an abnormal tuning to sexual immature faces in paedophilia. Here, we use functional magnetic resonance imaging (fMRI) to test directly for the existence of a network which is tuned to face cues of sexual maturity. During fMRI, participants sexually attracted to either adults or children were exposed to various face images. In individuals attracted to adults, adult faces activated several brain regions significantly more than child faces. These brain regions comprised areas known to be implicated in face processing, and sexual processing, including occipital areas, the ventrolateral prefrontal cortex and, subcortically, the putamen and nucleus caudatus. The same regions were activated in paedophiles, but with a reversed preferential response pattern. PMID:24850896

A comprehensive survey of the Plasmodium life cycle by genomic, transcriptomic, and proteomic analyses.

PubMed

Hall, Neil; Karras, Marianna; Raine, J Dale; Carlton, Jane M; Kooij, Taco W A; Berriman, Matthew; Florens, Laurence; Janssen, Christoph S; Pain, Arnab; Christophides, Georges K; James, Keith; Rutherford, Kim; Harris, Barbara; Harris, David; Churcher, Carol; Quail, Michael A; Ormond, Doug; Doggett, Jon; Trueman, Holly E; Mendoza, Jacqui; Bidwell, Shelby L; Rajandream, Marie-Adele; Carucci, Daniel J; Yates, John R; Kafatos, Fotis C; Janse, Chris J; Barrell, Bart; Turner, C Michael R; Waters, Andrew P; Sinden, Robert E

2005-01-07

Plasmodium berghei and Plasmodium chabaudi are widely used model malaria species. Comparison of their genomes, integrated with proteomic and microarray data, with the genomes of Plasmodium falciparum and Plasmodium yoelii revealed a conserved core of 4500 Plasmodium genes in the central regions of the 14 chromosomes and highlighted genes evolving rapidly because of stage-specific selective pressures. Four strategies for gene expression are apparent during the parasites' life cycle: (i) housekeeping; (ii) host-related; (iii) strategy-specific related to invasion, asexual replication, and sexual development; and (iv) stage-specific. We observed posttranscriptional gene silencing through translational repression of messenger RNA during sexual development, and a 47-base 3' untranslated region motif is implicated in this process.

Evolution and human sexuality.

PubMed

Gray, Peter B

2013-12-01

The aim of this review is to put core features of human sexuality in an evolutionary light. Toward that end, I address five topics concerning the evolution of human sexuality. First, I address theoretical foundations, including recent critiques and developments. While much traces back to Darwin and his view of sexual selection, more recent work helps refine the theoretical bases to sex differences and life history allocations to mating effort. Second, I consider central models attempting to specify the phylogenetic details regarding how hominin sexuality might have changed, with most of those models honing in on transitions from a possible chimpanzee-like ancestor to the slightly polygynous and long-term bonded sociosexual partnerships observed among most recently studied hunter-gatherers. Third, I address recent genetic and physiological data contributing to a refined understanding of human sexuality. As examples, the availability of rapidly increasing genomic information aids comparative approaches to discern signals of selection in sexuality-related phenotypes, and neuroendocrine studies of human responses to sexual stimuli provide insight into homologous and derived mechanisms. Fourth, I consider some of the most recent, large, and rigorous studies of human sexuality. These provide insights into sexual behavior across other national samples and on the Internet. Fifth, I discuss the relevance of a life course perspective to understanding the evolution of human sexuality. Most research on the evolution of human sexuality focuses on young adults. Yet humans are sexual beings from gestation to death, albeit in different ways across the life course, and in ways that can be theoretically couched within life history theory. Copyright © 2013 Wiley Periodicals, Inc.

Linguistic validation of the Sexual Inhibition and Sexual Excitation Scales (SIS/SES) translated into five South Asian languages: Oxford Sexual Dysfunction Study (OSDS).

PubMed

Malavige, Lasantha S; Wijesekara, Pabasi N; Jayaratne, Shanthilal D; Kathriarachchi, Samudra T; Ranasinghe, Priyanga; Sivayogan, Sivagurunathan; Levy, Jonathan C; Bancroft, John

2013-12-20

The purpose of the linguistic validation of the Sexual Inhibition and Sexual Excitation Scales (SIS/SES) was to produce translated versions in five South Asian languages (Hindi, Urdu, Panjabi, Tamil and Sinhalese) that was "conceptually equivalent" to the original U.S. English version, for use in the Oxford Sexual Dysfunction Study (OSDS). Initially an expert committee was appointed to carry out the task of linguistic validation. This committee included the principal investigator, project coordinator and the associate project manager of the OSDS and a language consultant for each of the South Asian languages. The process of translation and validation was conducted in the following order; a) production of two independent forward translations, b) comparison and reconciliation of the translations, c) backward translation of the first reconciled version, d) comparison of the original version of SIS/SES and the backward version leading to the production of the second reconciled version and e) pilot testing and finalization. Several linguistic and conceptual issues arose during the process of translating the instrument. Problems were also encountered with cultural differences in acceptability of certain concepts, and with semantic difficulties in finding an appropriate translation. In addition, the researchers had to find culturally acceptable equivalents for some terms and idiomatic phrases. The problems encountered in pilot testing, during cognitive debriefing and clinicians' review, were categorized as cultural or conceptual/semantic. Cultural issues describe the acceptability of using certain terms and phrases in a particular socio-cultural milieu. The conceptual and semantic difficulties reflect the inability to deliver the idea/meaning of a source statement in the target language. The current paper describes a selection of these issues. We applied a rigorous translation method to ensure conceptual equivalence and acceptability of SIS/SES in the five different South Asian languages prior to its utilization in the OSDS. However, to complete the cultural adaptation process, future psychometric validation of the translated versions is required among the different language speakers.

Premature ejaculation.

PubMed

McMahon, Chris G

2007-04-01

Premature ejaculation (PE) is a common male sexual disorder. Recent normative data suggests that men with an intravaginal ejaculatory latency time (IELT) of less than 1 minute have "definite" PE, while men with IELTs between 1 and 1.5 minutes have "probable" PE. Although there is insufficient empirical evidence to identify the etiology of PE, there is limited correlational evidence to suggest that men with PE have high levels of sexual anxiety and inherited altered sensitivity of central 5-HT (5-hydroxytryptamine, serotonin) receptors. Pharmacological modulation of the ejaculatory threshold using off-label daily or on-demand selective serotonin re-uptake inhibitors is well tolerated and offers patients a high likelihood of achieving improved ejaculatory control within a few days of initiating treatment, consequential improvements in sexual desire and other sexual domains. Investigational drugs such as the ejaculo-selective serotonin transport inhibitor, dapoxetine represent a major development in sexual medicine. These drugs offer patients the convenience of on-demand dosing, significant improvements in IELT, ejaculatory control and sexual satisfaction with minimal adverse effects.

Premature ejaculation

PubMed Central

McMahon, Chris G.

2007-01-01

Premature ejaculation (PE) is a common male sexual disorder. Recent normative data suggests that men with an intravaginal ejaculatory latency time (IELT) of less than 1 minute have “definite” PE, while men with IELTs between 1 and 1.5 minutes have “probable” PE. Although there is insufficient empirical evidence to identify the etiology of PE, there is limited correlational evidence to suggest that men with PE have high levels of sexual anxiety and inherited altered sensitivity of central 5-HT (5-hydroxytryptamine, serotonin) receptors. Pharmacological modulation of the ejaculatory threshold using off-label daily or on-demand selective serotonin re-uptake inhibitors is well tolerated and offers patients a high likelihood of achieving improved ejaculatory control within a few days of initiating treatment, consequential improvements in sexual desire and other sexual domains. Investigational drugs such as the ejaculo-selective serotonin transport inhibitor, dapoxetine represent a major development in sexual medicine. These drugs offer patients the convenience of on-demand dosing, significant improvements in IELT, ejaculatory control and sexual satisfaction with minimal adverse effects. PMID:19675782

EXPERIMENTAL STUDIES OF THE EVOLUTIONARY SIGNIFICANCE OF SEXUAL REPRODUCTION. V. A FIELD TEST OF THE SIB-COMPETITION LOTTERY HYPOTHESIS.

PubMed

Kelley, Steven E

1989-08-01

Sexually and asexually derived tillers of Anthoxanthum odoratum were planted directly in the field to test the hypothesis that competition among groups of sexual and asexual siblings favors the maintenance of sexual reproduction in populations. The results showed a substantial fitness advantage for sexual tillers. However, in contrast with the models, the advantage of sex did not increase with increasing numbers of colonists in the patch, there were multiple survivors among colonists, and an advantage was observed even for singly planted tillers. When a truncation-selection scheme was imposed ex post facto on the data, the relative performance of sexual tillers was similar to that predicted by the Bulmer (1980) model, suggesting that sib-competition models fail due to the violation of the assumption of truncation selection. The advantage of sex was not correlated with the presence of other species, total percentage cover, or species diversity, although sites where sex was favored were physically clustered. © 1989 The Society for the Study of Evolution.

Canine tooth size and fitness in male mandrills (Mandrillus sphinx).

PubMed

Leigh, Steven R; Setchell, Joanna M; Charpentier, Marie; Knapp, Leslie A; Wickings, E Jean

2008-07-01

Sexual selection theory explains the evolution of exaggerated male morphologies and weaponry, but the fitness consequences of developmental and age-related changes in these features remain poorly understood. This long-term study of mandrill monkeys (Mandrillus sphinx) demonstrates how age-related changes in canine tooth weaponry and adult canine size correlate closely with male lifetime reproductive success. Combining long-term demographic and morphometric data reveals that male fitness covaries simply and directly with canine ontogeny, adult maximum size, and wear. However, fitness is largely independent of other somatometrics. Male mandrills sire offspring almost exclusively when their canines exceed approximately 30 mm, or two-thirds of average adult value (45 mm). Moreover, sires have larger canines than nonsires. The tooth diminishes through wear as animals age, corresponding with, and perhaps influencing, reproductive senescence. These factors combine to constrain male reproductive opportunities to a brief timespan, defined by the period of maximum canine length. Sexually-selected weaponry, especially when it is nonrenewable like the primate canine tooth, is intimately tied to the male life course. Our analyses of this extremely dimorphic species indicate that sexual selection is closely intertwined with growth, development, and aging, pointing to new directions for sexual selection theory. Moreover, the primate canine tooth has potential as a simple mammalian system for testing genetically-based models of aging. Finally, the tooth may record details of life histories in fossil primates, especially when sexual selection has played a role in the evolution of dimorphism.

Sexual selection for male dominance reduces opportunities for female mate choice in the European bitterling (Rhodeus sericeus).

PubMed

Reichard, M; Bryja, J; Ondracková, M; Dávidová, M; Kaniewska, P; Smith, C

2005-04-01

Sexual selection involves two main mechanisms: intrasexual competition for mates and intersexual mate choice. We experimentally separated intrasexual (male-male interference competition) and intersexual (female choice) components of sexual selection in a freshwater fish, the European bitterling (Rhodeus sericeus). We compared the roles of multiple morphological and behavioural traits in male success in both components of sexual competition, and their relation to male reproductive success, measured as paternity of offspring. Body size was important for both female choice and male-male competition, though females also preferred males that courted more vigorously. However, dominant males often monopolized females regardless of female preference. Subordinate males were not excluded from reproduction and sired some offspring, possibly through sneaked ejaculations. Male dominance and a greater intensity of carotenoid-based red colouration in their iris were the best predictors of male reproductive success. The extent of red iris colouration and parasite load did not have significant effects on female choice, male dominance or male reproductive success. No effect of parasite load on the expression of red eye colouration was detected, though this may have been due to low parasite prevalence in males overall. In conclusion, we showed that even though larger body size was favoured in both intersexual and intrasexual selection, male-male interference competition reduced opportunities for female choice. Females, despite being choosy, had limited control over the paternity of their offspring. Our study highlights the need for reliable measures of male reproductive success in studies of sexual selection.

Sexual-perception processes in acquaintance-targeted sexual aggression.

PubMed

Treat, Teresa A; Viken, Richard J

2018-05-01

This study analyzes data from seven published studies to examine whether three performance-based indices of men's misperception of women's sexual interest (MSI), derived from a self-report questionnaire, are associated with sexual-aggression history, rape-supportive attitudes, sociosexuality, problem drinking, and self-reported MSI. Almost 2000 undergraduate men judged the justifiability of a man's increasingly unwanted advances toward a woman on the Heterosocial Perception Survey-Revised. Participants self-reported any sexual-aggression history, and some completed questionnaires assessing rape-supportive attitudes, sociosexuality, problem drinking, and self-reported MSI. A three-parameter logistic function was fitted to participants' justifiability ratings within a non-linear mixed-effects framework, which provided precise participant-specific estimates of three sexual-perception processes (baseline justifiability, bias, and sensitivity). Sexual-aggression history and rape-supportive attitudes predicted: (a) reduced sensitivity to women's affect; (b) more liberal biases, such that the woman's affect had to be more negative before justifiability ratings dropped substantially; and (c) greater baseline justifiability of continued advances after a positive response. Sexual-aggression history and attitudes correlated more strongly with sensitivity than baseline justifiability; remaining variables showed the opposite pattern. This work underscores the role of sexual-perception processes in sexual aggression and illustrates the derivation of performance-based estimates of sexual-perception processes from questionnaire responses. © 2018 Wiley Periodicals, Inc.

A systematic review of fantasy driven vs. contact driven internet-initiated sexual offences: Discrete or overlapping typologies?

PubMed

Broome, Laura Jayne; Izura, Cristina; Lorenzo-Dus, Nuria

2018-05-01

Within the literature individuals who use the internet to facilitate the sexual abuse of a minor are generally classified as being fantasy or contact driven. Classification is based upon the intended location for sexual climax: fantasy driven individuals aim to reach sexual climax online, whereas contact driven individuals target minors to achieve physical sex offline. This review systematically investigates whether there is an empirical basis for the distinction between these two proposed discrete types. Comparison of tactics and behaviour are considered to examine whether the contact vs. fantasy distinction is useful. A two-stage literature selection process, considered against pre-determined inclusion criteria, identified a total of twenty-two studies. As methodological heterogeneity limited the ability to conduct pooled analysis, a narrative synthesis of data employing an interpretive approach was conducted. This showed that the contact and fantasy distinction is ambiguous, given that both groups engage in online behaviours that provide them with online sexual gratification that can also lead to offline contact. Furthermore, no clear pattern of behaviour was found to define contact and fantasy individuals idiosyncratically. The European Online Grooming Project typology is thus proposed as a better representation of this behaviour; intimacy seeking, adaptable and hypersexualized groups. The distinction between these groups focuses primarily on the intensity of the relationship, acknowledging that sexual abuse can occur with or without offline contact. This review also highlights the need for larger, methodologically robust studies that examine the behaviour of online child sexual offenders. Copyright © 2018 Elsevier Ltd. All rights reserved.

Neural Correlates of Antidepressant-Related Sexual Dysfunction: A Placebo-Controlled fMRI Study on Healthy Males Under Subchronic Paroxetine and Bupropion

PubMed Central

Abler, Birgit; Seeringer, Angela; Hartmann, Antonie; Grön, Georg; Metzger, Coraline; Walter, Martin; Stingl, Julia

2011-01-01

Sexual dysfunction is a common side effect of selective serotonin reuptake inhibitors (SSRIs) like paroxetine in the treatment of depression, imposing a considerable risk on medication adherence and hence therapeutic success. Bupropion, a norepinephrine and dopamine reuptake inhibitor, is recommended as an alternative treatment without adverse effects concerning sexual arousal and libido. We investigated the neural bases of paroxetine-related subjective sexual dysfunction when compared with bupropion and placebo. We scanned 18 healthy, heterosexual males in a randomized, double-blind, within-subject design while watching video clips of erotic and nonerotic content under steady-state conditions after taking 20 mg of paroxetine, 150 mg of bupropion, and placebo for 7 days each. Under paroxetine, ratings of subjective sexual dysfunction increased compared with placebo or bupropion. Activation along the anterior cingulate cortex (ACC), including subgenual, pregenual, and midcingulate cortices, in the ventral striatum and midbrain was decreased when compared with placebo. In contrast, bupropion let subjective ratings and ACC activations unchanged and increased activity of brain regions including posterior midcingulate cortex, mediodorsal thalamus, and extended amygdala relative to placebo and paroxetine. Brain regions that have been related to the processing of motivational (ventral striatum), emotional, and autonomic components of erotic stimulation (anterior cingulate) in previous studies showed reduced responsiveness under paroxetine in our study. Drug effects on these regions may be part of the mechanism underlying SSRI-related sexual dysfunction. Increased activation under bupropion may point to an opposite effect that may relate to the lack of impaired sexual functioning. PMID:21544071

Neural correlates of antidepressant-related sexual dysfunction: a placebo-controlled fMRI study on healthy males under subchronic paroxetine and bupropion.

PubMed

Abler, Birgit; Seeringer, Angela; Hartmann, Antonie; Grön, Georg; Metzger, Coraline; Walter, Martin; Stingl, Julia

2011-08-01

Sexual dysfunction is a common side effect of selective serotonin reuptake inhibitors (SSRIs) like paroxetine in the treatment of depression, imposing a considerable risk on medication adherence and hence therapeutic success. Bupropion, a norepinephrine and dopamine reuptake inhibitor, is recommended as an alternative treatment without adverse effects concerning sexual arousal and libido. We investigated the neural bases of paroxetine-related subjective sexual dysfunction when compared with bupropion and placebo. We scanned 18 healthy, heterosexual males in a randomized, double-blind, within-subject design while watching video clips of erotic and nonerotic content under steady-state conditions after taking 20 mg of paroxetine, 150 mg of bupropion, and placebo for 7 days each. Under paroxetine, ratings of subjective sexual dysfunction increased compared with placebo or bupropion. Activation along the anterior cingulate cortex (ACC), including subgenual, pregenual, and midcingulate cortices, in the ventral striatum and midbrain was decreased when compared with placebo. In contrast, bupropion let subjective ratings and ACC activations unchanged and increased activity of brain regions including posterior midcingulate cortex, mediodorsal thalamus, and extended amygdala relative to placebo and paroxetine. Brain regions that have been related to the processing of motivational (ventral striatum), emotional, and autonomic components of erotic stimulation (anterior cingulate) in previous studies showed reduced responsiveness under paroxetine in our study. Drug effects on these regions may be part of the mechanism underlying SSRI-related sexual dysfunction. Increased activation under bupropion may point to an opposite effect that may relate to the lack of impaired sexual functioning.

Remembrance of things past retrieved from the Paramecium genome.

PubMed

Sperling, Linda

2011-01-01

Paramecium and other ciliates are the only unicellular eukaryotes that separate germinal and somatic functions. A germline micronucleus transmits the genetic information to sexual progeny, while a somatic macronucleus expresses the genetic information during vegetative growth to determine the phenotype. At each sexual generation, a new macronucleus develops from the zygotic nucleus through programmed rearrangements of the germline genome. Paramecium tetraurelia somatic genome sequencing, reviewed here, has provided insight into the organization and evolution of the genome. A series of at least 3 whole genome duplications was detected in the Paramecium lineage and selective pressures that determine the fate of the gene duplicates analyzed. Variability in the somatic DNA was characterized and could be attributed to the genome rearrangement processes. Since, in Paramecium, alternative genome rearrangement patterns can be inherited across sexual generations by homology-dependent epigenetic mechanisms and can affect phenotype, I discuss the possibility that ciliate nuclear dimorphism buffers genetic variation hidden in the germline. Copyright © 2011 Institut Pasteur. Published by Elsevier SAS. All rights reserved.

The use of monoamine pharmacological agents in the treatment of sexual dysfunction: evidence in the literature.

PubMed

Moll, Jennifer L; Brown, Candace S

2011-04-01

The monoamine neurotransmitters serotonin, dopamine, and norepinephrine play an important role in many medical and psychological conditions, including sexual responsiveness and behavior. Pharmacological agents that modulate monoamines may help alleviate sexual dysfunction. To provide an overview of pharmacological agents that modulate monoamines and their use in the treatment of sexual dysfunction. EMBASE and PubMed search for articles published between 1950 and 2010 using key words "sexual dysfunction,"monoamines,"monoaminergic receptors," and "generic names for pharmacological agents." To assess the literature evaluating the efficacy of monoamine pharmacologic agents used in the treatment of sexual dysfunction. The literature primarily cites the use of monoaminergic agents to treat sexual side effects from serotonergic reuptake inhibitors (SSRIs), with bupropion, buspirone and ropinirole providing the most convincing evidence. Controlled trials have shown that bupropion improves overall sexual dysfunction, but not frequency of sexual activity in depressed and nondepressed patients. Nefazodone and apomorphine have been used to treat sexual dysfunction, but their use is limited by significant side effect and safety profiles. New research on pharmacologic agents with subtype selectivity at dopaminergic and serotonergic receptors and those that possess dual mechanisms of action are being investigated. There has been tremendous progress over the past 50 years in understanding the role of monoamines in sexual function and the effect of pharmacologic agents which stimulate or antagonize monoaminergic receptors on sexual dysfunction. Nevertheless, large, double-blind, placebo-controlled studies evaluating the efficacy of currently available agents in populations without comorbid disorders are limited, preventing adequate interpretation of data. Continued research on sexual function and specific receptor subtypes will result in the development of more selective pharmacologic agents with the goal of increasing efficacy without the dose-limiting side effects of nonselective agents. © 2011 International Society for Sexual Medicine.

The Roles of Featural and Configural Face Processing in Snap Judgments of Sexual Orientation

PubMed Central

Tabak, Joshua A.; Zayas, Vivian

2012-01-01

Research has shown that people are able to judge sexual orientation from faces with above-chance accuracy, but little is known about how these judgments are formed. Here, we investigated the importance of well-established face processing mechanisms in such judgments: featural processing (e.g., an eye) and configural processing (e.g., spatial distance between eyes). Participants judged sexual orientation from faces presented for 50 milliseconds either upright, which recruits both configural and featural processing, or upside-down, when configural processing is strongly impaired and featural processing remains relatively intact. Although participants judged women’s and men’s sexual orientation with above-chance accuracy for upright faces and for upside-down faces, accuracy for upside-down faces was significantly reduced. The reduced judgment accuracy for upside-down faces indicates that configural face processing significantly contributes to accurate snap judgments of sexual orientation. PMID:22629321

[Sex differences in sexual versus emotional jealousy: evolutionary approach and recent discussions].

PubMed

Demirtaş Madran, H Andaç

2008-01-01

Sex differences in jealousy have been reported widely in the social psychological, clinical psychological, psychiatric, and anthropological literature. Many of the studies conducted on jealousy have focused on the sex differences in the level of reported jealousy. Most research has reported that there is no difference between men and women regarding the level of reported jealousy, but there are some sex differences between sexual and emotional jealousy. Evolutionary psychologists divide jealousy into 2 dimensions based on their observations and empirical research findings: Sexual jealousy and emotional jealousy. Sexual jealousy is knowing or suspecting that one's partners has had sexual relationship with a third person, whereas emotional jealousy is triggered by partner's emotional involvement with and/or love for another person. The parental investment model, which extended Darwin's explanations of sexual selection, provides a useful theoretical framework for studying sexual and emotional jealousy. According to this model sexual selection is driven by differential parental investment by men and women; men should experience more sexual jealousy than women and women should experience more emotional jealousy than men. Considerable research has focused on testing this hypothesis and, with a few exceptions, the results are generally consistent with the evolutionary account. In this study, firstly, a brief definition of the sexual and emotional jealousy will be given. Then, sex differences in sexual and emotional jealousy will be explained according to the evolutionary theory. Finally, the results of empirical studies and critiques of the evolutionary model will be given.

Freshman Sexual Attitudes and Behavior.

ERIC Educational Resources Information Center

Nutt, Roberta L.; Sedlacek, William E.

At the University of Maryland, 758 randomly selected incoming freshman students were administered an anonymous poll regarding their sexual attitudes and behavior. Results showed that the Maryland freshman generally resembled other U.S. college students in their sexual experience. Approximately half (52% of males, 46% of females) reported that they…

Florida Residents' Preferred Approach to Sexuality Education

ERIC Educational Resources Information Center

Howard-Barr, Elissa M.; Moore, Michele Johnson

2007-01-01

Although there is widespread support for sexuality education, whether to use an abstinence-only or comprehensive approach is hotly debated. This study assessed Florida residents preferred approach to school-based sexuality education. The 641 respondents were selected by random digit dialing, using methods to ensure ethnic and geographic…

When parsimony is not enough: Considering dual processes and dual levels of influence in sexual decision making

PubMed Central

Rendina, H. Jonathon

2015-01-01

The literature on sexual decision making that has been used to understand behaviors relevant to HIV and STI risk has relied primarily on cognitive antecedents of behavior. In contrast, several prominent models of decision making outside of the sexual behavior literature rely on dual process models, in which both affective and cognitive processing are considered important precursors to behavior. Moreover, much of the literature on sexual behavior utilizes individual-level traits and characteristics to predict aggregated sexual behavior, despite decision making itself being a situational or event-level process. This paper proposes a framework for understanding sexual decision making as the result of dual processes (affective and cognitive) operating at dual level of influence (individual and situational). Finally, the paper ends with a discussion of the conceptual and methodological benefits and challenges to its use and future directions for research. PMID:26168978

Sexual Satellites, Moonlight and the Nuptial Dances of Worms: the Influence of the Moon on the Reproduction of Marine Animals

NASA Astrophysics Data System (ADS)

Bentley, M. G.; Olive, P. J. W.; Last, K.

The evidence that the moon has a profound effect on the timing of reproductive activities of marine animals is compelling. Some moon phase related spawning events are revealed by the constant phase relationship between the timing of ``once per year'' spawning events and the lunar phase as in the highly synchronised breeding of the palolo worm Palola viridis and the Japanese crinoid Comanthus japonicus In other cases there is a repeated lunar cycle of reproductive activity and again the marine worms provide many good examples. The breeding of the palolo worm involves the highly synchronised release of what are in effect detached sexual satellites and the timing of this has annual (solar year), lunar, daily and tidal rhythm components. In a similar way, the onset of sexual maturation and participation in the nuptial dance of Platynereis dumerilli has strong lunar components. Sexual reproduction is the culmination of a process of sexual maturation that takes many months for completion and the mechanisms by which moon phase relationships are imposed on this process must have been selected for by mechanisms relating to reproductive success. The polychaetes provide excellent models for investigation of both the selective advantage and the physiological processes involved in reproductive synchrony. We have recently shown that the spawning of the lugworm Arenicola marina has lunar components and we conclude that an interaction between solar and lunar signals is widespread in the timing of reproduction in marine animals. Carl Hauenschild was the first to demonstrate the existence of a free-running circa-lunar rhythm in marine animals using captive populations of Platynereis dumerilli His experiments also provided clear evidence for the influence of moonlight (light at night) as the zeitgeber for this rhythm. This implies a high level of sensitivity to light, and the operation of appropriate endogenous biological rhythms. Using Nereis virens we have demonstrated a high level of sensitivity to low intensity solar light signals in relation to rhythmic processes with the properties similar to the circadian and photoperiodic mechanisms of terrestrial organisms. The spawning of N. virens is also believed to have lunar components reflecting the complex influences of the sun and the moon in the marine domain, where influences of the moon and sun are more equal. We suggest that evolution of biological rhythmicity that can be entrained to either lunar or solar systems arose in the marine domain. Recent advances in understanding the molecular components of the circadian clock system suggest that a search for a common molecular mechanism for both lunar and solar related biological rhythms in marine organisms might be very fruitful.

Runaway cultural niche construction

PubMed Central

Rendell, Luke; Fogarty, Laurel; Laland, Kevin N.

2011-01-01

Cultural niche construction is a uniquely potent source of selection on human populations, and a major cause of recent human evolution. Previous theoretical analyses have not, however, explored the local effects of cultural niche construction. Here, we use spatially explicit coevolutionary models to investigate how cultural processes could drive selection on human genes by modifying local resources. We show that cultural learning, expressed in local niche construction, can trigger a process with dynamics that resemble runaway sexual selection. Under a broad range of conditions, cultural niche-constructing practices generate selection for gene-based traits and hitchhike to fixation through the build up of statistical associations between practice and trait. This process can occur even when the cultural practice is costly, or is subject to counteracting transmission biases, or the genetic trait is selected against. Under some conditions a secondary hitchhiking occurs, through which genetic variants that enhance the capability for cultural learning are also favoured by similar dynamics. We suggest that runaway cultural niche construction could have played an important role in human evolution, helping to explain why humans are simultaneously the species with the largest relative brain size, the most potent capacity for niche construction and the greatest reliance on culture. PMID:21320897

The Family Hour Focus Groups: Children's Responses to Sexual Content on TV and Their Parents' Reactions.

ERIC Educational Resources Information Center

Kaiser Foundation, Oakland, CA.

With regard to sexual content, an argument is often made that sexual jokes, innuendoes, and behavior on television "go over kids' heads." To address this issue, focus groups were conducted with children between the ages of 8 and 13. Children viewed a tape of a selection of clips containing sexual content from programs aired in 1996…

Sexual orientation in males and the evolution of anisogamy.

PubMed

Reed, Lawrence Ian

2010-02-01

How might homosexual orientation have evolved and been maintained? Several adaptationist explanations have been examined in attempt to reconcile the presence of same-sex sexual behaviors with traditional selection-based theory, showing little empirical support. The current paper presents a novel adaptationist explanation for the evolution and maintenance of same-sex sexual behaviors in males, both between- and within-species, related to the evolution of anisogamy. Under conditions of isogamy, sexual reproduction occurs between individuals with gametes of similar morphology. With the evolution of anisogamy came greater specificity on the types of individuals that would produce offspring when mated with (i.e. those with opposing gamete sizes). It is suggested that with this evolutionary change, a specified psychological adaptation orienting individuals primarily towards mating partners with newly opposing gamete sizes was then selected for. It is thus hypothesized that sexual orientation will vary along the anisogamy-isogamy continuum, with homosexual orientation being associated with closer approximations towards isogamy. This hypothesis leads to two specific predictions. First, in comparisons between species, the presence of same-sex sexual behaviors will be more likely to occur as sperm to egg ratios approach 1:1. Second, in comparisons within species, those individuals with greater sperm lengths will be more likely to exhibit same-sex sexual behaviors than those with lesser sperm lengths. Examination of the present hypothesis stands to greatly increase our knowledge of the selective forces shaping both biological and psychological evolution.

Migrate small, sound big: functional constraints on body size promote tracheal elongation in cranes.

PubMed

Jones, M R; Witt, C C

2014-06-01

Organismal traits often represent the outcome of opposing selection pressures. Although social or sexual selection can cause the evolution of traits that constrain function or survival (e.g. ornamental feathers), it is unclear how the strength and direction of selection respond to ecological shifts that increase the severity of the constraint. For example, reduced body size might evolve by natural selection to enhance flight performance in migratory birds, but social or sexual selection favouring large body size may provide a countervailing force. Tracheal elongation is a potential outcome of these opposing pressures because it allows birds to convey an auditory signal of exaggerated body size. We predicted that the evolution of migration in cranes has coincided with a reduction in body size and a concomitant intensification of social or sexual selection for apparent large body size via tracheal elongation. We used a phylogenetic comparative approach to examine the relationships among migration distance, body mass and trachea length in cranes. As predicted, we found that migration distance correlated negatively with body size and positively with proportional trachea length. This result was consistent with our hypothesis that evolutionary reductions in body size led to intensified selection for trachea length. The most likely ultimate causes of intensified positive selection on trachea length are the direct benefits of conveying a large body size in intraspecific contests for mates and territories. We conclude that the strength of social or sexual selection on crane body size is linked to the degree of functional constraint. © 2014 The Authors. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

Dopamine and serotonin: influences on male sexual behavior.

PubMed

Hull, Elaine M; Muschamp, John W; Sato, Satoru

2004-11-15

Steroid hormones regulate sexual behavior primarily by slow, genomically mediated effects. These effects are realized, in part, by enhancing the processing of relevant sensory stimuli, altering the synthesis, release, and/or receptors for neurotransmitters in integrative areas, and increasing the responsiveness of appropriate motor outputs. Dopamine has facilitative effects on sexual motivation, copulatory proficiency, and genital reflexes. Dopamine in the nigrostriatal tract influences motor activity; in the mesolimbic tract it activates numerous motivated behaviors, including copulation; in the medial preoptic area (MPOA) it controls genital reflexes, copulatory patterns, and specifically sexual motivation. Testosterone increases nitric oxide synthase in the MPOA; nitric oxide increases basal and female-stimulated dopamine release, which in turn facilitates copulation and genital reflexes. Serotonin (5-HT) is primarily inhibitory, although stimulation of 5-HT(2C) receptors increases erections and inhibits ejaculation, whereas stimulation of 5-HT(1A) receptors has the opposite effects: facilitation of ejaculation and, in some circumstances, inhibition of erection. 5-HT is released in the anterior lateral hypothalamus at the time of ejaculation. Microinjections of selective serotonin reuptake inhibitors there delay the onset of copulation and delay ejaculation after copulation begins. One means for this inhibition is a decrease in dopamine release in the mesolimbic tract.

Understanding processes of risk and protection that shape the sexual and reproductive health of young women affected by conflict: the price of protection.

PubMed

Hutchinson, Aisha; Waterhouse, Philippa; March-McDonald, Jane; Neal, Sarah; Ingham, Roger

2017-01-01

It is assumed that knowing what puts young women at risk of poor sexual health outcomes and, in turn, what protects them against these outcomes, will enable greater targeted protection as well as help in designing more effective programmes. Accordingly, efforts have been directed towards mapping risk and protective factors onto general ecological frameworks, but these currently do not take into account the context of modern armed conflict. A literature overview approach was used to identify SRH related risk and protective factors specifically for young women affected by modern armed conflict. A range of keywords were used to identify academic articles which explored the sexual and reproductive health needs of young women affected by modern armed conflict. Selected articles were read to identify risk and protective factors in relation to sexual and reproductive health. While no articles explicitly identified 'risk' or 'protective' factors, we were able to extrapolate these through a thorough engagement with the text. However, we found that it was difficult to identify factors as either 'risky' or 'protective', with many having the capacity to be both risky and protective (i.e. refugee camps or family). Therefore, using an ecological model, six environments that impact upon young women's lives in contexts of modern armed conflict are used to illustrate the dynamic and complex operation of risk and protection - highlighting processes of protection and the 'trade-offs' between risks. We conclude that there are no simple formulaic risk/protection patterns to be applied in every conflict and post-conflict context. Instead, there needs to be greater recognition of the 'processes' of protection, including the role of 'trade-offs' (what we term as 'protection at a price'), in order to further effective policy and practical responses to improve sexual and reproductive health outcomes during or following armed conflict. Focus on specific 'factors' (such as 'female headed household') takes attention away from the processes through which factors manifest themselves and which often determine whether the factor will later be considered 'risk inducing' or protective.

Improving Measures of Sexual and Gender Identity in English and Spanish to Identify LGBT Older Adults in Surveys.

PubMed

Michaels, Stuart; Milesi, Carolina; Stern, Michael; Viox, Melissa Heim; Morrison, Heather; Guerino, Paul; Dragon, Christina N; Haffer, Samuel C

2017-12-01

The goal of this research is to advance the study of health disparities faced by older sexual and gender minorities by assessing comprehension of and improving measures of sexual and gender identity in surveys. Cognitive interviews were conducted by expert interviewers with 48 non-lesbian, gay, bisexual, and transgender (non-LGBT) and 9 LGBT older English and Spanish speakers. All respondents were able to answer questions about their sex assigned at birth and current gender identity successfully despite some cisgender respondents' lack of clear understanding of the transgender response option. On the contrary, while the vast majority of English speakers could answer the question about their sexual identity successfully, almost 60% of the non-LGBT Spanish speakers did not select the "heterosexual, that is, not gay (or lesbian)" response category. Qualitative probing of their response process pointed mainly to difficulties understanding the term "heterosexual," leading to their choosing "something else" or saying that they didn't know how to answer. A second round of testing of alternative response categories for the sexual identity question with Spanish speakers found a marked improvement when offered "not gay (or lesbian), that is, heterosexual" instead of beginning with the term "heterosexual." This research adds to our understanding of gender and sexual identity questions appropriate for population surveys with older adults. Inclusion of these measures in surveys is a crucial step in advancing insights into the needs of and disparities faced by LGBT older adults.

Evolutionary perspectives on learning: conceptual and methodological issues in the study of adaptive specializations.

PubMed

Krause, Mark A

2015-07-01

Inquiry into evolutionary adaptations has flourished since the modern synthesis of evolutionary biology. Comparative methods, genetic techniques, and various experimental and modeling approaches are used to test adaptive hypotheses. In psychology, the concept of adaptation is broadly applied and is central to comparative psychology and cognition. The concept of an adaptive specialization of learning is a proposed account for exceptions to general learning processes, as seen in studies of Pavlovian conditioning of taste aversions, sexual responses, and fear. The evidence generally consists of selective associations forming between biologically relevant conditioned and unconditioned stimuli, with conditioned responses differing in magnitude, persistence, or other measures relative to non-biologically relevant stimuli. Selective associations for biologically relevant stimuli may suggest adaptive specializations of learning, but do not necessarily confirm adaptive hypotheses as conceived of in evolutionary biology. Exceptions to general learning processes do not necessarily default to an adaptive specialization explanation, even if experimental results "make biological sense". This paper examines the degree to which hypotheses of adaptive specializations of learning in sexual and fear response systems have been tested using methodologies developed in evolutionary biology (e.g., comparative methods, quantitative and molecular genetics, survival experiments). A broader aim is to offer perspectives from evolutionary biology for testing adaptive hypotheses in psychological science.

Female sexual dysfunction and adolescents.

PubMed

Greydanus, Donald E; Matytsina, Lyubov

2010-10-01

To review recent publications in the area of sexual dysfunction in females including the adolescent age group. Though as many as 40% of adult females have a sexual dysfunction, the incidence among adolescent females is unknown. Though over half of adolescents are sexually active, sexual dysfunction is not a term universally accepted among the general public as well as researchers. Research on sexual dysfunction in females typically starts with age 18 years or over. Causes of sexual dysfunction include medical disorders, gynecological problems, which started from the adolescent age, psychiatric disorders, and complications of medications such as selective serotonin reuptake inhibitors (SSRIs), antipsychotics, and others. Management includes identification of the specific sexual dysfunction and treatment of the underlying condition, including surgical treatment in such cases as absent vagina or obstetrics fistula. Psychological therapy is helpful when psychological factors are contributory to the dysfunction. Pharmacologic principles of management cases can, for example, include treatment of gynecological problems such as pelvic inflammatory disease (PID) or endometriosis as a cause of sexual dysfunction or include removal of the offending drug, use of glutamatergic strategies or trazodone in SSRI-association dysfunction, and addition of bupropion or other medications in select cases. No medication is FDA-approved for sexual dysfunction in females. Sexual dysfunction in females includes lack of sexual desire, sexual pain disorders (as dyspareunia), anorgasmia, and sexual arousal dysfunction. Acceptance of the high incidence of sexual dysfunction in all female populations is necessary to appreciate this phenomenon in the adolescent cohort, because some gynecological disease can arise from the adolescent age and can cause sexual dysfunction. Some sexual dysfunctions require immediate treatment, including surgical in the case of congenital anomaly, ovarian cyst, or tumor. Current understanding is based on extrapolation of research in the adult population. Management principles include removal of offending drugs and treatment of underlying disorders. Research in the adolescent population is recommended for more understanding and acceptance of this phenomenon in this age group.

The role of ecology, neutral processes and antagonistic coevolution in an apparent sexual arms race.

PubMed

Perry, Jennifer C; Garroway, Colin J; Rowe, Locke

2017-09-01

Some of the strongest examples of a sexual 'arms race' come from observations of correlated evolution in sexually antagonistic traits among populations. However, it remains unclear whether these cases truly represent sexually antagonistic coevolution; alternatively, ecological or neutral processes might also drive correlated evolution. To investigate these alternatives, we evaluated the contributions of intersex genetic correlations, ecological context, neutral genetic divergence and sexual coevolution in the correlated evolution of antagonistic traits among populations of Gerris incognitus water striders. We could not detect intersex genetic correlations for these sexually antagonistic traits. Ecological variation was related to population variation in the key female antagonistic trait (spine length, a defence against males), as well as body size. Nevertheless, population covariation between sexually antagonistic traits remained substantial and significant even after accounting for all of these processes. Our results therefore provide strong evidence for a contemporary sexual arms race. © 2017 John Wiley & Sons Ltd/CNRS.

Evolutionary divergence in sexual signals: Insights from within and among barn swallow populations

NASA Astrophysics Data System (ADS)

Wilkins, Matthew Reed

A wealth of studies across diverse animal groups indicate the importance of sexual selection in shaping phenotypes within and across breeding populations. In recent decades, much research has focused on how divergent sexual selection pressures among populations may lead to speciation. For my first dissertation chapter, I performed a literature review on the causes and consequences of evolutionary divergence in acoustic signals and developed the acoustic window conceptual framework for understanding the contributions of selection, genetic drift, and evolutionary constraint to signal divergence. Further, I found that sexual selection explains acoustic differences between recently diverged populations of the best-studied taxa. However, the relative contributions of ecological selection, sexual selection, and drift to acoustic divergence have not typically been considered within the same study systems. The remainder of my dissertation used the Northern Hemisphere-distributed barn swallow ( Hirundo rustica) species complex as a model system to study sender-receiver dynamics, intra- and intersexual selection pressures, and visual and acoustic signal interactions at the local scale, and signal divergence across populations at the global scale. From song recordings taken across 19 sampling sites, spanning five of six described subspecies, I demonstrated considerable conservation in song structure. However, temporal traits were highly divergent across subspecies, and in particular, the speed of the terminal trill of songs. In a detailed study of the multimodal communication system of the barn swallow (including visual and acoustic traits), I demonstrated that males and females use different types of signals to mediate competition and mate choice. One of the only exceptions to this rule was trill rate, which was also implicated in song divergence across populations. In order to test the function of trill rate in communication, I performed a two-year playback study within the North American subspecies, H. r. erythrogaster. Contrary to expectations, males did not have stronger responses to faster trilling (high performance) simulated intruders. Instead, resident males had stronger responses to the high performance stimulus only when the intruder was also darker than the resident. Collectively, my dissertation offers novel insight into the evolutionary dynamics of complex sexual signaling at multiple spatial scales.

Sexual selection affects the evolution of lifespan and ageing in the decorated cricket Gryllodes sigillatus.

PubMed

Archer, C R; Zajitschek, F; Sakaluk, S K; Royle, N J; Hunt, J

2012-10-01

Recent work suggests that sexual selection can influence the evolution of ageing and lifespan by shaping the optimal timing and relative costliness of reproductive effort in the sexes. We used inbred lines of the decorated cricket, Gryllodes sigillatus, to estimate the genetic (co)variance between age-dependent reproductive effort, lifespan, and ageing within and between the sexes. Sexual selection theory predicts that males should die sooner and age more rapidly than females. However, a reversal of this pattern may be favored if reproductive effort increases with age in males but not in females. We found that male calling effort increased with age, whereas female fecundity decreased, and that males lived longer and aged more slowly than females. These divergent life-history strategies were underpinned by a positive genetic correlation between early-life reproductive effort and ageing rate in both sexes, although this relationship was stronger in females. Despite these sex differences in life-history schedules, age-dependent reproductive effort, lifespan, and ageing exhibited strong positive intersexual genetic correlations. This should, in theory, constrain the independent evolution of these traits in the sexes and may promote intralocus sexual conflict. Our study highlights the importance of sexual selection to the evolution of sex differences in ageing and lifespan in G. sigillatus. © 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.