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Sample records for sympatric ecological speciation

  1. Ecological speciation in sympatric palms: 1. Gene expression, selection and pleiotropy.

    PubMed

    Dunning, L T; Hipperson, H; Baker, W J; Butlin, R K; Devaux, C; Hutton, I; Igea, J; Papadopulos, A S T; Quan, X; Smadja, C M; Turnbull, C G N; Savolainen, V

    2016-08-01

    Ecological speciation requires divergent selection, reproductive isolation and a genetic mechanism to link the two. We examined the role of gene expression and coding sequence evolution in this process using two species of Howea palms that have diverged sympatrically on Lord Howe Island, Australia. These palms are associated with distinct soil types and have displaced flowering times, representing an ideal candidate for ecological speciation. We generated large amounts of RNA-Seq data from multiple individuals and tissue types collected on the island from each of the two species. We found that differentially expressed loci as well as those with divergent coding sequences between Howea species were associated with known ecological and phenotypic differences, including response to salinity, drought, pH and flowering time. From these loci, we identified potential 'ecological speciation genes' and further validate their effect on flowering time by knocking out orthologous loci in a model plant species. Finally, we put forward six plausible ecological speciation loci, providing support for the hypothesis that pleiotropy could help to overcome the antagonism between selection and recombination during speciation with gene flow. PMID:27177130

  2. On the origin of species by sympatric speciation

    NASA Astrophysics Data System (ADS)

    Dieckmann, Ulf; Doebeli, Michael

    1999-07-01

    Understanding speciation is a fundamental biological problem. It is believed that many species originated through allopatric divergence, where new species arise from geographically isolated populations of the same ancestral species. In contrast, the possibility of sympatric speciation (in which new species arise without geographical isolation) has often been dismissed, partly because of theoretical difficulties,. Most previous models analysing sympatric speciation concentrated on particular aspects of the problem while neglecting others. Here we present a model that integrates a novel combination of different features and show that sympatric speciation is a likely outcome of competition for resources. We use multilocus genetics to describe sexual reproduction in an individual-based model, and we consider the evolution of assortative mating (where individuals mate preferentially with like individuals) depending either on an ecological character affecting resource use or on a selectively neutral marker trait. In both cases, evolution of assortative mating often leads to reproductive isolation between ecologically diverging subpopulations. When assortative mating depends on a marker trait, and is therefore not directly linked to resource competition, speciation occurs when genetic drift breaks the linkage equilibrium between the marker and the ecological trait. Our theory conforms well with mounting empirical evidence for the sympatric origin of many species.

  3. Genomics of Rapid Incipient Speciation in Sympatric Threespine Stickleback

    PubMed Central

    Marques, David A.; Lucek, Kay; Meier, Joana I.; Mwaiko, Salome; Wagner, Catherine E.; Excoffier, Laurent; Seehausen, Ole

    2016-01-01

    Ecological speciation is the process by which reproductively isolated populations emerge as a consequence of divergent natural or ecologically-mediated sexual selection. Most genomic studies of ecological speciation have investigated allopatric populations, making it difficult to infer reproductive isolation. The few studies on sympatric ecotypes have focused on advanced stages of the speciation process after thousands of generations of divergence. As a consequence, we still do not know what genomic signatures of the early onset of ecological speciation look like. Here, we examined genomic differentiation among migratory lake and resident stream ecotypes of threespine stickleback reproducing in sympatry in one stream, and in parapatry in another stream. Importantly, these ecotypes started diverging less than 150 years ago. We obtained 34,756 SNPs with restriction-site associated DNA sequencing and identified genomic islands of differentiation using a Hidden Markov Model approach. Consistent with incipient ecological speciation, we found significant genomic differentiation between ecotypes both in sympatry and parapatry. Of 19 islands of differentiation resisting gene flow in sympatry, all were also differentiated in parapatry and were thus likely driven by divergent selection among habitats. These islands clustered in quantitative trait loci controlling divergent traits among the ecotypes, many of them concentrated in one region with low to intermediate recombination. Our findings suggest that adaptive genomic differentiation at many genetic loci can arise and persist in sympatry at the very early stage of ecotype divergence, and that the genomic architecture of adaptation may facilitate this. PMID:26925837

  4. Interactions among quantitative traits in the course of sympatric speciation

    NASA Astrophysics Data System (ADS)

    Kondrashov, Alexey S.; Kondrashov, Fyodor A.

    1999-07-01

    Sympatric speciation, the origin of two or more species from a single local population, has almost certainly been involved in formation of several species flocks, and may be fairly common in nature. The most straightforward scenario for sympatric speciation requires disruptive selection favouring two substantially different phenotypes, and consists of the evolution of reproductive isolation between them followed by the elimination of all intermediate phenotypes. Here we use the hypergeometric phenotypic model to show that sympatric speciation is possible even when fitness and mate choice depend on different quantitative traits, so that speciation must involve formation of covariance between these traits. The increase in the number of variable lociaffecting fitness facilitates sympatric speciation, whereas the increase in the number of variable loci affecting mate choice has the opposite effect. These predictions may enable more cases of sympatric speciation to be identified.

  5. Sympatric speciation as a consequence of male pregnancy in seahorses

    PubMed Central

    Jones, Adam G.; Moore, Glenn I.; Kvarnemo, Charlotta; Walker, DeEtte; Avise, John C.

    2003-01-01

    The phenomenon of male pregnancy in the family Syngnathidae (seahorses, pipefishes, and sea dragons) undeniably has sculpted the course of behavioral evolution in these fishes. Here we explore another potentially important but previously unrecognized consequence of male pregnancy: a predisposition for sympatric speciation. We present microsatellite data on genetic parentage that show that seahorses mate size-assortatively in nature. We then develop a quantitative genetic model based on these empirical findings to demonstrate that sympatric speciation indeed can occur under this mating regime in response to weak disruptive selection on body size. We also evaluate phylogenetic evidence bearing on sympatric speciation by asking whether tiny seahorse species are sister taxa to large sympatric relatives. Overall, our results indicate that sympatric speciation is a plausible mechanism for the diversification of seahorses, and that assortative mating (in this case as a result of male parental care) may warrant broader attention in the speciation process for some other taxonomic groups as well. PMID:12732712

  6. Adaptive methylation regulation of p53 pathway in sympatric speciation of blind mole rats, Spalax

    PubMed Central

    Zhao, Yang; Tang, Jia-Wei; Yang, Zhi; Cao, Yi-Bin; Ren, Ji-Long; Ben-Abu, Yuval; Li, Kexin; Chen, Xue-Qun; Du, Ji-Zeng; Nevo, Eviatar

    2016-01-01

    Epigenetic modifications play significant roles in adaptive evolution. The tumor suppressor p53, well known for controlling cell fate and maintaining genomic stability, is much less known as a master gene in environmental adaptation involving methylation modifications. The blind subterranean mole rat Spalax eherenbergi superspecies in Israel consists of four species that speciated peripatrically. Remarkably, the northern Galilee species Spalax galili (2n = 52) underwent adaptive ecological sympatric speciation, caused by the sharply divergent chalk and basalt ecologies. This was demonstrated by mitochondrial and nuclear genomic evidence. Here we show that the expression patterns of the p53 regulatory pathway diversified between the abutting sympatric populations of S. galili in sharply divergent chalk–basalt ecologies. We identified higher methylation on several sites of the p53 promoter in the population living in chalk soil (chalk population). Site mutagenesis showed that methylation on these sites linked to the transcriptional repression of p53 involving Cut-Like Homeobox 1 (Cux1), paired box 4 (Pax 4), Pax 6, and activator protein 1 (AP-1). Diverse expression levels of p53 between the incipiently sympatrically speciating chalk–basalt abutting populations of S. galili selectively affected cell-cycle arrest but not apoptosis. We hypothesize that methylation modification of p53 has adaptively shifted in supervising its target genes during sympatric speciation of S. galili to cope with the contrasting environmental stresses of the abutting divergent chalk–basalt ecologies. PMID:26858405

  7. Adaptive methylation regulation of p53 pathway in sympatric speciation of blind mole rats, Spalax.

    PubMed

    Zhao, Yang; Tang, Jia-Wei; Yang, Zhi; Cao, Yi-Bin; Ren, Ji-Long; Ben-Abu, Yuval; Li, Kexin; Chen, Xue-Qun; Du, Ji-Zeng; Nevo, Eviatar

    2016-02-23

    Epigenetic modifications play significant roles in adaptive evolution. The tumor suppressor p53, well known for controlling cell fate and maintaining genomic stability, is much less known as a master gene in environmental adaptation involving methylation modifications. The blind subterranean mole rat Spalax eherenbergi superspecies in Israel consists of four species that speciated peripatrically. Remarkably, the northern Galilee species Spalax galili (2n = 52) underwent adaptive ecological sympatric speciation, caused by the sharply divergent chalk and basalt ecologies. This was demonstrated by mitochondrial and nuclear genomic evidence. Here we show that the expression patterns of the p53 regulatory pathway diversified between the abutting sympatric populations of S. galili in sharply divergent chalk-basalt ecologies. We identified higher methylation on several sites of the p53 promoter in the population living in chalk soil (chalk population). Site mutagenesis showed that methylation on these sites linked to the transcriptional repression of p53 involving Cut-Like Homeobox 1 (Cux1), paired box 4 (Pax 4), Pax 6, and activator protein 1 (AP-1). Diverse expression levels of p53 between the incipiently sympatrically speciating chalk-basalt abutting populations of S. galili selectively affected cell-cycle arrest but not apoptosis. We hypothesize that methylation modification of p53 has adaptively shifted in supervising its target genes during sympatric speciation of S. galili to cope with the contrasting environmental stresses of the abutting divergent chalk-basalt ecologies. PMID:26858405

  8. The Midas cichlid species complex: incipient sympatric speciation in Nicaraguan cichlid fishes?

    PubMed

    Barluenga, Marta; Meyer, Axel

    2004-07-01

    Abstract Sympatric speciation is a contentious concept, although theoretical models as well as empirical evidence support its relevance in evolutionary biology. The Midas cichlid species complex (Amphilophus citrinellus, labiatus, zaliosus) from several crater lakes in Nicaragua fits several of the key characteristics of a sympatric speciation model. In particular, in A. citrinellus (i) strong assortative mating on the basis of colour polymorphism and (ii) ecological differentiation based on morphological polymorphisms involving the feeding apparatus and body shape might both be mechanisms of incipient speciation. Seven microsatellite markers and mtDNA control region sequences [836 base pairs (bp)] were used to study the population genetic structure of 519 specimens of Midas cichlid populations from the two Great Lakes Managua and Nicaragua, and three crater lakes in Nicaragua, Central America. The three named species of the species complex occupy different ecological niches, are morphologically distinct and can be distinguished genetically. We uncovered allopatric genetic differentiation of populations of A. citrinellus from different lakes and distant locations within Lake Managua and, more interestingly, incipient genetic differentiation of several sympatric populations based on colouration (in A. citrinellus and A. labiatus) but not on the morphology of the pharyngeal jaws (in A. citrinellus). Sexual selection and assortative mating might be the driven forces of diversification within named species. The Midas cichlid species complex in Nicaragua is an excellent model system for the study of the incipient stages of adaptation, speciation and the formation of species flocks. PMID:15189226

  9. Habitat avoidance: overlooking an important aspect of host-specific mating and sympatric speciation?

    PubMed

    Forbes, Andrew A; Fisher, Joan; Feder, Jeffrey L

    2005-07-01

    Understanding speciation requires discerning how reproductive barriers to gene flow evolve between previously interbreeding populations. Models of sympatric speciation for phytophagous insects posit that reproductive isolation can evolve in the absence of geographic isolation as a consequence of an insect shifting and ecologically adapting to a new host plant. One important adaptation contributing to sympatric differentiation is host-specific mating. When organisms mate in preferred habitats, a system of positive assortative mating is established that facilitates sympatric divergence. Models of host fidelity generally assume that host choice is determined by the aggregate effect of alleles imparting positive preferences for different plant species. But negative effect genes for avoiding nonnatal plants may also influence host use. Previous studies have shown that apple and hawthorn-infesting races of Rhagoletis pomonella flies use volatile compounds emitted from the surface of fruit as key chemosensory cues to recognize and distinguish between their host plants. Here, we report results from field trials indicating that in addition to preferring the odor of their natal fruit, apple and hawthorn flies, and their undescribed sister species infesting flowering dogwood (Cornus florida), also avoid the odors of nonnatal fruit. We discuss the implications of nonnatal fruit avoidance for the evolutionary dynamics and genetics of sympatric speciation. Our findings reveal an underappreciated role for habitat avoidance as a potential postmating, as well as prezygotic, barrier to gene flow. PMID:16153040

  10. Host races in plant-feeding insects and their importance in sympatric speciation.

    PubMed Central

    Drès, Michele; Mallet, James

    2002-01-01

    The existence of a continuous array of sympatric biotypes - from polymorphisms, through ecological or host races with increasing reproductive isolation, to good species - can provide strong evidence for a continuous route to sympatric speciation via natural selection. Host races in plant-feeding insects, in particular, have often been used as evidence for the probability of sympatric speciation. Here, we provide verifiable criteria to distinguish host races from other biotypes: in brief, host races are genetically differentiated, sympatric populations of parasites that use different hosts and between which there is appreciable gene flow. We recognize host races as kinds of species that regularly exchange genes with other species at a rate of more than ca. 1% per generation, rather than as fundamentally distinct taxa. Host races provide a convenient, although admittedly somewhat arbitrary intermediate stage along the speciation continuum. They are a heuristic device to aid in evaluating the probability of speciation by natural selection, particularly in sympatry. Speciation is thereby envisaged as having two phases: (i) the evolution of host races from within polymorphic, panmictic populations; and (ii) further reduction of gene flow between host races until the diverging populations can become generally accepted as species. We apply this criterion to 21 putative host race systems. Of these, only three are unambiguously classified as host races, but a further eight are strong candidates that merely lack accurate information on rates of hybridization or gene flow. Thus, over one-half of the cases that we review are probably or certainly host races, under our definition. Our review of the data favours the idea of sympatric speciation via host shift for three major reasons: (i) the evolution of assortative mating as a pleiotropic by-product of adaptation to a new host seems likely, even in cases where mating occurs away from the host; (ii) stable genetic differences in

  11. Sympatric incipient speciation of spiny mice Acomys at “Evolution Canyon,” Israel

    PubMed Central

    Hadid, Yarin; Pavlíček, Tomáš; Beiles, Avigdor; Ianovici, Ron; Raz, Shmuel; Nevo, Eviatar

    2014-01-01

    Does the paucity of empirical evidence of sympatric speciation in nature reflect reality, despite theoretical support? Or is it due to inappropriate searches in nature with overly restrictive assumptions and an incorrect null hypothesis? Spiny mice, Acomys, described here at Evolution Canyon (EC) incipiently and sympatrically speciate owing to microclimatic interslope divergence. The opposite slopes at EC vary dramatically, physically and biotically, representing the dry and hot south-facing slope savannoid-African continent [“African” slope (AS)], abutting with the north-facing slope forested south-European continent [“European” slope (ES)]. African-originated spiny mice, of the Acomys cahirinus complex, colonized Israel 30,000 y ago based on fossils. Genotypically, we showed significantly higher genetic diversity of mtDNA and amplified fragment length polymorphism of Acomys on the AS compared with the ES. This is also true regionally across Israel. In complete mtDNA, 25% of the haplotypes at EC were slope-biased. Phenotypically, the opposite slope’s populations also showed adaptive morphology, physiology, and behavior divergence paralleling regional populations across Israel. Preliminary tests indicate slope-specific mate choices. Colonization of Acomys at the EC first occurred on the AS and then moved to the ES. Strong slope-specific natural selection (both positive and negative) overrules low interslope gene flow. Both habitat slope selection and mate choices suggest ongoing incipient sympatric speciation. We conclude that Acomys at the EC is ecologically and genetically adaptively, incipiently, sympatrically speciating on the ES owing to adaptive microclimatic natural selection. PMID:24402169

  12. Genetics of ecological divergence during speciation

    PubMed Central

    Arnegard, Matthew E.; McGee, Matthew D.; Matthews, Blake; Marchinko, Kerry B.; Conte, Gina L.; Kabir, Sahriar; Bedford, Nicole; Bergek, Sara; Chan, Yingguang Frank; Jones, Felicity C.; Kingsley, David M.; Peichel, Catherine L.; Schluter, Dolph

    2014-01-01

    Ecological differences often evolve early in speciation as divergent natural selection drives adaptation to distinct ecological niches, leading ultimately to reproductive isolation. Though this process is a major generator of biodiversity, its genetic basis remains poorly understood. Here we investigate the genetic architecture of niche differentiation in a sympatric species pair of threespine stickleback fish by mapping the environment-dependent effects of phenotypic traits on hybrid feeding and performance under semi-natural conditions. We show that multiple, unlinked loci act largely additively to determine position along the major niche axis separating these recently diverged species. We also find that functional mismatch between phenotypic traits reduces growth of some stickleback hybrids beyond that expected from an intermediate phenotype, suggesting a role for epistasis between the underlying genes. This functional mismatch might lead to hybrid incompatibilities that are analogous to those underlying intrinsic reproductive isolation but that depend on the ecological context. PMID:24909991

  13. Modeling coevolution and sympatric speciation of flowers and pollinators

    NASA Astrophysics Data System (ADS)

    Bhattacharyay, A.; Drossel, B.

    2005-01-01

    A model based on quantitative genetics for the coevolution of plants and their pollinators is proposed. The model is characterized by competition for resources and by a two-fold coupling between the two types of species: pollinators depend on plants for resources and plants on pollinators for pollination. Starting with unimodal trait distributions, we study the dynamics of the model using computer simulations with discrete generations and alternating reproduction and selection. Under a variety of conditions we observe an evolution towards bimodal distributions, with two subpopulations that are reproductively isolated to a large extent. We also find sympatric speciation in situations where two pollinators pollinate the same plant, and where one pollinator pollinates two plants.

  14. An Evaluation of Putative Sympatric Speciation within Limnanthes (Limnanthaceae)

    PubMed Central

    Meyers, Stephen C.; Liston, Aaron; Meinke, Robert

    2012-01-01

    Limnanthes floccosa ssp. floccosa and L. floccosa ssp. grandiflora are two of five subspecies within Limnanthes floccosa endemic to vernal pools in southern Oregon and northern California. Three seasons of monitoring natural populations have quantified that L. floccosa ssp. grandiflora is always found growing sympatrically with L. floccosa ssp. floccosa and that their flowering times overlap considerably. Despite their subspecific rank within the same species crossing experiments have confirmed that their F1 hybrids are sterile. An analysis of twelve microsatellite markers, with unique alleles in each taxon, also shows exceedingly low levels of gene flow between populations of the two subspecies. Due to the lack of previous phylogenetic resolution among L. floccosa subspecies, we used Illumina next generation sequencing to identify single nucleotide polymorphisms from genomic DNA libraries of L. floccosa ssp. floccosa and L. floccosa ssp. grandiflora. These data were used to identify single nucleotide polymorphisms in the chloroplast, mitochondrial, and nuclear genomes. From these variable loci, a total of 2772 bp was obtained using Sanger sequencing of ten individuals representing all subspecies of L. floccosa and an outgroup. The resulting phylogenetic reconstruction was fully resolved. Our results indicate that although L. floccosa ssp. floccosa and L. floccosa ssp. grandiflora are closely related, they are not sister taxa and therefore likely did not diverge as a result of a sympatric speciation event. PMID:22563502

  15. How sympatric is speciation in the Howea palms of Lord Howe Island?

    PubMed

    Babik, Wiesław; Butlin, Roger K; Baker, William J; Papadopulos, Alexander S T; Boulesteix, Matthieu; Anstett, Marie-Charlotte; Lexer, Christian; Hutton, Ian; Savolainen, Vincent

    2009-09-01

    The two species of the palm genus Howea (Arecaceae) from Lord Howe Island, a minute volcanic island in the Tasman Sea, are now regarded as one of the most compelling examples of sympatric speciation, although this view is still disputed by some authors. Population genetic and ecological data are necessary to provide a more coherent and comprehensive understanding of this emerging model system. Here, we analyse data on abundance, juvenile recruitment, pollination mode and genetic variation and structure in both species. We find that Howea forsteriana is less abundant than Howea belmoreana. The genetic data based on amplified fragment length polymorphisms markers indicate similar levels of variation in the two species, despite the estimated census population size of H. belmoreana being three times larger than that of H. forsteriana. Genetic structure within species is low although some weak isolation by distance is detectable. Gene flow between species appears to be extremely limited and restricted to early-generation hybrids - only three admixed individuals, classified as F2s or first generation backcrosses to a parental species, were found among sampled palms. We conclude that speciation in Howea was indeed sympatric, although under certain strict definitions it may be called parapatric. PMID:19674301

  16. Are sympatrically speciating Midas cichlid fish special? Patterns of morphological and genetic variation in the closely related species Archocentrus centrarchus.

    PubMed

    Fruciano, Carmelo; Franchini, Paolo; Raffini, Francesca; Fan, Shaohua; Meyer, Axel

    2016-06-01

    Established empirical cases of sympatric speciation are scarce, although there is an increasing consensus that sympatric speciation might be more common than previously thought. Midas cichlid fish are one of the few substantiated cases of sympatric speciation, and they formed repeated radiations in crater lakes. In contrast, in the same environment, such radiation patterns have not been observed in other species of cichlids and other families of fish. We analyze morphological and genetic variation in a cichlid species (Archocentrus centrarchus) that co-inhabits several crater lakes with the Midas species complex. In particular, we analyze variation in body and pharyngeal jaw shape (two ecologically important traits in sympatrically divergent Midas cichlids) and relate that to genetic variation in mitochondrial control region and microsatellites. Using these four datasets, we analyze variation between and within two Nicaraguan lakes: a crater lake where multiple Midas cichlids have been described and a lake where the source population lives. We do not observe any within-lake clustering consistent across morphological traits and genetic markers, suggesting the absence of sympatric divergence in A. centrarchus. Genetic differentiation between lakes was low and morphological divergence absent. Such morphological similarity between lakes is found not only in average morphology, but also when analyzing covariation between traits and degree of morphospace occupation. A combined analysis of the mitochondrial control region in A. centrarchus and Midas cichlids suggests that a difference between lineages in the timing of crater lake colonization cannot be invoked as an explanation for the difference in their levels of diversification. In light of our results, A. centrarchus represents the ideal candidate to study the genomic differences between these two lineages that might explain why some lineages are more likely to speciate and diverge in sympatry than others. PMID

  17. Transcriptome, genetic editing, and microRNA divergence substantiate sympatric speciation of blind mole rat, Spalax.

    PubMed

    Li, Kexin; Wang, Liuyang; Knisbacher, Binyamin A; Xu, Qinqin; Levanon, Erez Y; Wang, Huihua; Frenkel-Morgenstern, Milana; Tagore, Satabdi; Fang, Xiaodong; Bazak, Lily; Buchumenski, Ilana; Zhao, Yang; Lövy, Matěj; Li, Xiangfeng; Han, Lijuan; Frenkel, Zeev; Beiles, Avigdor; Cao, Yi Bin; Wang, Zhen Long; Nevo, Eviatar

    2016-07-01

    Incipient sympatric speciation in blind mole rat, Spalax galili, in Israel, caused by sharp ecological divergence of abutting chalk-basalt ecologies, has been proposed previously based on mitochondrial and whole-genome nuclear DNA. Here, we present new evidence, including transcriptome, DNA editing, microRNA, and codon usage, substantiating earlier evidence for adaptive divergence in the abutting chalk and basalt populations. Genetic divergence, based on the previous and new evidence, is ongoing despite restricted gene flow between the two populations. The principal component analysis, neighbor-joining tree, and genetic structure analysis of the transcriptome clearly show the clustered divergent two mole rat populations. Gene-expression level analysis indicates that the population transcriptome divergence is displayed not only by soil divergence but also by sex. Gene ontology enrichment of the differentially expressed genes from the two abutting soil populations highlights reproductive isolation. Alternative splicing variation of the two abutting soil populations displays two distinct splicing patterns. L-shaped FST distribution indicates that the two populations have undergone divergence with gene flow. Transcriptome divergent genes highlight neurogenetics and nutrition characterizing the chalk population, and energetics, metabolism, musculature, and sensory perception characterizing the abutting basalt population. Remarkably, microRNAs also display divergence between the two populations. The GC content is significantly higher in chalk than in basalt, and stress-response genes mostly prefer nonoptimal codons. The multiple lines of evidence of ecological-genomic and genetic divergence highlight that natural selection overrules the gene flow between the two abutting populations, substantiating the sharp ecological chalk-basalt divergence driving sympatric speciation. PMID:27339131

  18. Sympatric speciation revealed by genome-wide divergence in the blind mole rat Spalax.

    PubMed

    Li, Kexin; Hong, Wei; Jiao, Hengwu; Wang, Guo-Dong; Rodriguez, Karl A; Buffenstein, Rochelle; Zhao, Yang; Nevo, Eviatar; Zhao, Huabin

    2015-09-22

    Sympatric speciation (SS), i.e., speciation within a freely breeding population or in contiguous populations, was first proposed by Darwin [Darwin C (1859) On the Origins of Species by Means of Natural Selection] and is still controversial despite theoretical support [Gavrilets S (2004) Fitness Landscapes and the Origin of Species (MPB-41)] and mounting empirical evidence. Speciation of subterranean mammals generally, including the genus Spalax, was considered hitherto allopatric, whereby new species arise primarily through geographic isolation. Here we show in Spalax a case of genome-wide divergence analysis in mammals, demonstrating that SS in continuous populations, with gene flow, encompasses multiple widespread genomic adaptive complexes, associated with the sharply divergent ecologies. The two abutting soil populations of S. galili in northern Israel habituate the ancestral Senonian chalk population and abutting derivative Plio-Pleistocene basalt population. Population divergence originated ∼0.2-0.4 Mya based on both nuclear and mitochondrial genome analyses. Population structure analysis displayed two distinctly divergent clusters of chalk and basalt populations. Natural selection has acted on 300+ genes across the genome, diverging Spalax chalk and basalt soil populations. Gene ontology enrichment analysis highlights strong but differential soil population adaptive complexes: in basalt, sensory perception, musculature, metabolism, and energetics, and in chalk, nutrition and neurogenetics are outstanding. Population differentiation of chemoreceptor genes suggests intersoil population's mate and habitat choice substantiating SS. Importantly, distinctions in protein degradation may also contribute to SS. Natural selection and natural genetic engineering [Shapiro JA (2011) Evolution: A View From the 21st Century] overrule gene flow, evolving divergent ecological adaptive complexes. Sharp ecological divergences abound in nature; therefore, SS appears to be an

  19. Strong assortative mating by diet, color, size, and morphology but limited progress toward sympatric speciation in a classic example: Cameroon crater lake cichlids.

    PubMed

    Martin, Christopher H

    2013-07-01

    Models predict that sympatric speciation depends on restrictive parameter ranges, such as sufficiently strong disruptive selection and assortative mating, but compelling examples in nature have rarely been used to test these predictions. I measured the strength of assortative mating within a species complex of Tilapia in Lake Ejagham, Cameroon, a celebrated example of incipient sympatric adaptive radiation. This species complex is in the earliest stages of speciation: morphological and ecological divergence are incomplete, species differ primarily in breeding coloration, and introgression is common. I captured 27 mated pairs in situ and measured the diet, color, size, and morphology of each individual. I found strong assortative mating by color, size, head depth, and dietary source of benthic or pelagic prey along two independent dimensions of assortment. Thus, Ejagham Tilapia showed strong assortative mating most conducive to sympatric speciation. Nonetheless, in contrast to a morphologically bimodal Sarotherodon cichlid species pair in the lake, Ejagham Tilapia show more limited progress toward speciation, likely due to insufficient strength of disruptive selection on morphology estimated in a previous study (γ = 0.16). This supports the predicted dependence of sympatric speciation on strong assortment and strong disruptive selection by examining a potentially stalled example in nature. PMID:23815664

  20. Sympatric speciation of spiny mice, Acomys, unfolded transcriptomically at Evolution Canyon, Israel.

    PubMed

    Li, Kexin; Wang, Huihua; Cai, Zhenyuan; Wang, Liuyang; Xu, Qinqin; Lövy, Matěj; Wang, Zhenlong; Nevo, Eviatar

    2016-07-19

    Spiny mice, Acomys cahirinus, colonized Israel 30,000 y ago from dry tropical Africa and inhabited rocky habitats across Israel. Earlier, we had shown by mtDNA that A. cahirinus incipiently sympatrically speciates at Evolution Canyon I (EC I) in Mount Carmel, Israel because of microclimatic interslope divergence. The EC I microsite consists of a dry and hot savannoid "African" slope (AS) and an abutting humid and cool-forested "European" slope (ES). Here, we substantiate incipient SS in A. cahirinus at EC I based on the entire transcriptome, showing that multiple slope-specific adaptive complexes across the transcriptome result in two divergent clusters. Tajima's D distribution of the abutting Acomys interslope populations shows that the ES population is under stronger positive selection, whereas the AS population is under balancing selection, harboring higher genetic polymorphisms. Considerable sites of the two populations were differentiated with a coefficient of FST = 0.25-0.75. Remarkably, 24 and 37 putatively adaptively selected genes were detected in the AS and ES populations, respectively. The AS genes involved DNA repair, growth arrest, neural cell differentiation, and heat-shock proteins adapting to the local AS stresses of high solar radiation, drought, and high temperature. In contrast, the ES genes involved high ATP associated with energetics stress. The sharp ecological interslope divergence led to strong slope-specific selection overruling the interslope gene flow. Earlier tests suggested slope-specific mate choice. Habitat interslope-adaptive selection across the transcriptome and mate choice substantiate sympatric speciation (SS), suggesting its prevalence at EC I and commonality in nature. PMID:27370801

  1. Evidence for nonallopatric speciation among closely related sympatric Heliotropium species in the Atacama Desert.

    PubMed

    Luebert, Federico; Jacobs, Pit; Hilger, Hartmut H; Muller, Ludo A H

    2014-02-01

    The genetic structure of populations of closely related, sympatric species may hold the signature of the geographical mode of the speciation process. In fully allopatric speciation, it is expected that genetic differentiation between species is homogeneously distributed across the genome. In nonallopatric speciation, the genomes may remain undifferentiated to a large extent. In this article, we analyzed the genetic structure of five sympatric species from the plant genus Heliotropium in the Atacama Desert. We used amplified fragment length polymorphisms (AFLPs) to characterize the genetic structure of these species and evaluate their genetic differentiation as well as the number of loci subject to positive selection using divergence outlier analysis (DOA). The five species form distinguishable groups in the genetic space, with zones of overlap, indicating that they are possibly not completely isolated. Among-species differentiation accounts for 35% of the total genetic differentiation (F ST = 0.35), and F ST between species pairs is positively correlated with phylogenetic distance. DOA suggests that few loci are subject to positive selection, which is in line with a scenario of nonallopatric speciation. These results support the idea that sympatric species of Heliotropium sect. Cochranea are under an ongoing speciation process, characterized by a fluctuation of population ranges in response to pulses of arid and humid periods during Quaternary times. PMID:24558582

  2. Evidence for nonallopatric speciation among closely related sympatric Heliotropium species in the Atacama Desert

    PubMed Central

    Luebert, Federico; Jacobs, Pit; Hilger, Hartmut H; Muller, Ludo A H

    2014-01-01

    The genetic structure of populations of closely related, sympatric species may hold the signature of the geographical mode of the speciation process. In fully allopatric speciation, it is expected that genetic differentiation between species is homogeneously distributed across the genome. In nonallopatric speciation, the genomes may remain undifferentiated to a large extent. In this article, we analyzed the genetic structure of five sympatric species from the plant genus Heliotropium in the Atacama Desert. We used amplified fragment length polymorphisms (AFLPs) to characterize the genetic structure of these species and evaluate their genetic differentiation as well as the number of loci subject to positive selection using divergence outlier analysis (DOA). The five species form distinguishable groups in the genetic space, with zones of overlap, indicating that they are possibly not completely isolated. Among-species differentiation accounts for 35% of the total genetic differentiation (FST = 0.35), and FST between species pairs is positively correlated with phylogenetic distance. DOA suggests that few loci are subject to positive selection, which is in line with a scenario of nonallopatric speciation. These results support the idea that sympatric species of Heliotropium sect. Cochranea are under an ongoing speciation process, characterized by a fluctuation of population ranges in response to pulses of arid and humid periods during Quaternary times. PMID:24558582

  3. Adaptation and incipient sympatric speciation of Bacillus simplex under microclimatic contrast at “Evolution Canyons” I and II, Israel

    PubMed Central

    Sikorski, Johannes; Nevo, Eviatar

    2005-01-01

    The microevolutionary dynamics of prokaryotes in natural habitats, such as soil, is poorly understood in contrast to our increasing knowledge on their immense diversity. We performed microevolutionary analyses on 945 soil isolates of Bacillus simplex from “Evolution Canyons” I (Carmel, Israel) and II (Galilee, Israel). These canyons represent similar ecological replicates, separated by 40 km, with highly contrasting interslope abiotic and biotic conditions in each (within a distance of only 100–400 m). Strains representing genetic groups were identical in their 16S sequences, suggesting high genetic similarity and monophyletic origin. Parallel and nested phylogenetic structures correlated with ecological contrasts rather than geographical distance. Additionally, slope-specific populations differed substantially in their diversity. The levels of DNA repair (determined by UV sensitivity) and spontaneous mutation rate (resistance to rifampicin) relate to ecological stress and phylogeny. Altogether, the results suggest adaptive radiation at a microscale. We discuss the observed adaptive population structures in the context of incipient sympatric speciation in soil bacteria. We conclude that, despite different biology, prokaryotes, like sexually reproducing eukaryotes, may consist of true species and parallel ecological speciation in eukaryotes. PMID:16249328

  4. Multispecies Outcomes of Sympatric Speciation after Admixture with the Source Population in Two Radiations of Nicaraguan Crater Lake Cichlids.

    PubMed

    Kautt, Andreas F; Machado-Schiaffino, Gonzalo; Meyer, Axel

    2016-06-01

    The formation of species in the absence of geographic barriers (i.e. sympatric speciation) remains one of the most controversial topics in evolutionary biology. While theoretical models have shown that this most extreme case of primary divergence-with-gene-flow is possible, only a handful of accepted empirical examples exist. And even for the most convincing examples uncertainties remain; complex histories of isolation and secondary contact can make species falsely appear to have originated by sympatric speciation. This alternative scenario is notoriously difficult to rule out. Midas cichlids inhabiting small and remote crater lakes in Nicaragua are traditionally considered to be one of the best examples of sympatric speciation and lend themselves to test the different evolutionary scenarios that could lead to apparent sympatric speciation since the system is relatively small and the source populations known. Here we reconstruct the evolutionary history of two small-scale radiations of Midas cichlids inhabiting crater lakes Apoyo and Xiloá through a comprehensive genomic data set. We find no signs of differential admixture of any of the sympatric species in the respective radiations. Together with coalescent simulations of different demographic models our results support a scenario of speciation that was initiated in sympatry and does not result from secondary contact of already partly diverged populations. Furthermore, several species seem to have diverged simultaneously, making Midas cichlids an empirical example of multispecies outcomes of sympatric speciation. Importantly, however, the demographic models strongly support an admixture event from the source population into both crater lakes shortly before the onset of the radiations within the lakes. This opens the possibility that the formation of reproductive barriers involved in sympatric speciation was facilitated by genetic variants that evolved in a period of isolation between the initial founding

  5. Multispecies Outcomes of Sympatric Speciation after Admixture with the Source Population in Two Radiations of Nicaraguan Crater Lake Cichlids

    PubMed Central

    Kautt, Andreas F.; Machado-Schiaffino, Gonzalo; Meyer, Axel

    2016-01-01

    The formation of species in the absence of geographic barriers (i.e. sympatric speciation) remains one of the most controversial topics in evolutionary biology. While theoretical models have shown that this most extreme case of primary divergence-with-gene-flow is possible, only a handful of accepted empirical examples exist. And even for the most convincing examples uncertainties remain; complex histories of isolation and secondary contact can make species falsely appear to have originated by sympatric speciation. This alternative scenario is notoriously difficult to rule out. Midas cichlids inhabiting small and remote crater lakes in Nicaragua are traditionally considered to be one of the best examples of sympatric speciation and lend themselves to test the different evolutionary scenarios that could lead to apparent sympatric speciation since the system is relatively small and the source populations known. Here we reconstruct the evolutionary history of two small-scale radiations of Midas cichlids inhabiting crater lakes Apoyo and Xiloá through a comprehensive genomic data set. We find no signs of differential admixture of any of the sympatric species in the respective radiations. Together with coalescent simulations of different demographic models our results support a scenario of speciation that was initiated in sympatry and does not result from secondary contact of already partly diverged populations. Furthermore, several species seem to have diverged simultaneously, making Midas cichlids an empirical example of multispecies outcomes of sympatric speciation. Importantly, however, the demographic models strongly support an admixture event from the source population into both crater lakes shortly before the onset of the radiations within the lakes. This opens the possibility that the formation of reproductive barriers involved in sympatric speciation was facilitated by genetic variants that evolved in a period of isolation between the initial founding

  6. Stridulations Reveal Cryptic Speciation in Neotropical Sympatric Ants

    PubMed Central

    Ferreira, Ronara Souza; Poteaux, Chantal; Delabie, Jacques Hubert Charles; Fresneau, Dominique; Rybak, Fanny

    2010-01-01

    The taxonomic challenge posed by cryptic species underlines the importance of using multiple criteria in species delimitation. In the current paper we tested the use of acoustic analysis as a tool to assess the real diversity in a cryptic species complex of Neotropical ants. In order to understand the potential of acoustics and to improve consistency in the conclusions by comparing different approaches, phylogenetic relationships of all the morphs considered were assessed by the analysis of a fragment of the mitochondrial DNA cytochrome b. We observed that each of the cryptic morph studied presents a morphologically distinct stridulatory organ and that all sympatric morphs produce distinctive stridulations. This is the first evidence of such a degree of specialization in the acoustic organ and signals in ants, which suggests that stridulations may be among the cues used by these ants during inter-specific interactions. Mitochondrial DNA variation corroborated the acoustic differences observed, confirming acoustics as a helpful tool to determine cryptic species in this group of ants, and possibly in stridulating ants in general. Congruent morphological, acoustic and genetic results constitute sufficient evidence to propose each morph studied here as a valid new species, suggesting that P. apicalis is a complex of at least 6 to 9 species, even if they present different levels of divergence. Finally, our results highlight that ant stridulations may be much more informative than hitherto thought, as much for ant communication as for integrative taxonomists. PMID:21203529

  7. Genetic linkage of distinct adaptive traits in sympatrically speciating crater lake cichlid fish.

    PubMed

    Fruciano, Carmelo; Franchini, Paolo; Kovacova, Viera; Elmer, Kathryn R; Henning, Frederico; Meyer, Axel

    2016-01-01

    Our understanding of how biological diversity arises is limited, especially in the case of speciation in the face of gene flow. Here we investigate the genomic basis of adaptive traits, focusing on a sympatrically diverging species pair of crater lake cichlid fishes. We identify the main quantitative trait loci (QTL) for two eco-morphological traits: body shape and pharyngeal jaw morphology. These traits diverge in parallel between benthic and limnetic species in the repeated adaptive radiations of this and other fish lineages. Remarkably, a single chromosomal region contains the highest effect size QTL for both traits. Transcriptomic data show that the QTL regions contain genes putatively under selection. Independent population genomic data corroborate QTL regions as areas of high differentiation between the sympatric sister species. Our results provide empirical support for current theoretical models that emphasize the importance of genetic linkage and pleiotropy in facilitating rapid divergence in sympatry. PMID:27597183

  8. Mechanisms regulating proteostasis are involved in sympatric speciation of the blind mole rat, Spalax galili

    PubMed Central

    Rodriguez, Karl A.; Li, Kexin; Nevo, Eviatar; Buffenstein, Rochelle

    2016-01-01

    ABSTRACT Genome-wide analysis demonstrates extensive genomic adaptive complexes involved in sympatric speciation between blind mole rats (Spalax galili) in abutting populations living in basalt and chalk soils. Among the gene ontology (GO) enrichment, musculature and metabolism stood out in basalt dwellers while nutrition and neurogenetics were highlighted in chalk residents. Measurements of mechanisms regulating protein homeostasis inspired by these GO terms suggest that at the proteomic level there is also a habitat/soil-type driven divergence with the basalt residents exhibiting higher proteasome activity whereas elevated levels of markers of autophagy are evident in the chalk inhabitants. PMID:27050459

  9. Mechanisms regulating proteostasis are involved in sympatric speciation of the blind mole rat, Spalax galili.

    PubMed

    Rodriguez, Karl A; Li, Kexin; Nevo, Eviatar; Buffenstein, Rochelle

    2016-01-01

    Genome-wide analysis demonstrates extensive genomic adaptive complexes involved in sympatric speciation between blind mole rats (Spalax galili) in abutting populations living in basalt and chalk soils. Among the gene ontology (GO) enrichment, musculature and metabolism stood out in basalt dwellers while nutrition and neurogenetics were highlighted in chalk residents. Measurements of mechanisms regulating protein homeostasis inspired by these GO terms suggest that at the proteomic level there is also a habitat/soil-type driven divergence with the basalt residents exhibiting higher proteasome activity whereas elevated levels of markers of autophagy are evident in the chalk inhabitants. PMID:27050459

  10. [Sympatric Speciation of the Plague Microbe Yersinia pestis: Monohostal Specialization in the Host-Parasite Marmot-Flea (Marmota sibirica-Oropsylla silantiewi) System].

    PubMed

    Suntsov, V V

    2016-01-01

    An ecological scenario of the origin of the plague microbe that is interpreted in the light of modern Darwinism (synthetic theory of evolution) is presented. It is shown that the plague microbe emerged from a clone of the psychrophilic saprozoonotic pseudotuberculosis microbe Yersinia pseudotuberculosis O:1b in the mountain steppe landscapes of Central Asia in the Sartan time, 22000-15000 years ago, in the monohostal Mongolian marmot (Marmota sibirica)-flea (Oropsylla silantiewi) host-parasite system. It was noted that the evolutionary process described corresponds to the sympatric form of speciation by transition ofthe clone of migrant founders to a new, already-existing ecological niche. It was established that monohostal specialization of the plague microbe was made possible due to heterothermia (5-37 degrees C) of marmots in the hibernation period. The factors of the speciation process--isolation, the struggle for existence, and natural selection--were analyzed. PMID:27396172

  11. The geography and ecology of plant speciation: range overlap and niche divergence in sister species

    PubMed Central

    Anacker, Brian L.; Strauss, Sharon Y.

    2014-01-01

    A goal of evolutionary biology is to understand the roles of geography and ecology in speciation. The recent shared ancestry of sister species can leave a major imprint on their geographical and ecological attributes, possibly revealing processes involved in speciation. We examined how ecological similarity, range overlap and range asymmetry are related to time since divergence of 71 sister species pairs in the California Floristic Province (CFP). We found that plants exhibit strikingly different age-range correlation patterns from those found for animals; the latter broadly support allopatric speciation as the primary mode of speciation. By contrast, plant sisters in the CFP were sympatric in 80% of cases and range sizes of sisters differed by a mean of 10-fold. Range overlap and range asymmetry were greatest in younger sisters. These results suggest that speciation mechanisms broadly grouped under ‘budding’ speciation, in which a larger ranged progenitor gives rise to a smaller ranged derivative species, are probably common. The ecological and reproductive similarity of sisters was significantly greater than that of sister–non-sister congeners for every trait assessed. However, shifts in at least one trait were present in 93% of the sister pairs; habitat and soil shifts were especially common. Ecological divergence did not increase with range overlap contrary to expectations under character displacement in sympatry. Our results suggest that vicariant speciation is more ubiquitous in animals than plants, perhaps owing to the sensitivity of plants to fine-scale environmental heterogeneity. Despite high levels of range overlap, ecological shifts in the process of budding speciation may result in low rates of fine-scale spatial co-occurrence. These results have implications for ecological studies of trait evolution and community assembly; despite high levels of sympatry, sister taxa and potentially other close relatives, may be missing from local communities

  12. The behavioral ecology of sympatric African apes: implications for understanding fossil hominoid ecology.

    PubMed

    Stanford, Craig B

    2006-01-01

    The behavioral ecology of the great apes is key evidence used in the reconstruction of the behavior of extinct ape and hominid taxa. Chimpanzees and gorillas have been studied in detail in the wild, and some studies of their behavioral ecology in sympatry have also been been carried out. Although the two ape species have divergent behavior and ecology in important respects, recent studies have shown that the interspecific differences are not as stark as previously thought and subsequently urge new consideration of how they share forest resources when sympatric. These new data require re-examination of assumptions about key aspects of chimpanzee-gorilla ecological divergence, such as diet, ranging and nesting patterns, and the mating system. Diet is a key component of the species' adaptive complexes that facilitates avoidance of direct competition from the other. While the nutritional basis for chimpanzee food choice remains unclear and no doubt varies from site to site, this species is a ripe fruit specialist and ranges farther during periods of ripe fruit scarcity. Gorillas in the same habitat also feed on ripe fruit when widely available, but fall back onto fibrous plant foods during lean periods. The inclusion of animal protein in the diet of the chimpanzees and its absence in that of the gorillas also distinguish the species ecologically. It may also offer clues to aspects of ecological divergence among early members of the hominid phylogeny. The paper concludes by suggesting likely characteristics of sympatric associations of Pliocene hominids, based on field data from extant sympatric apes. PMID:16283423

  13. Ecological speciation in tropical reef fishes

    PubMed Central

    Rocha, Luiz A; Robertson, D. Ross; Roman, Joe; Bowen, Brian W

    2005-01-01

    The high biodiversity in tropical seas provides a long-standing challenge to allopatric speciation models. Physical barriers are few in the ocean and larval dispersal is often extensive, a combination that should reduce opportunities for speciation. Yet coral reefs are among the most species-rich habitats in the world, indicating evolutionary processes beyond conventional allopatry. In a survey of mtDNA sequences of five congeneric west Atlantic reef fishes (wrasses, genus Halichoeres) with similar dispersal potential, we observed phylogeographical patterns that contradict expectations of geographical isolation, and instead indicate a role for ecological speciation. In Halichoeres bivittatus and the species pair Halichoeres radiatus/brasiliensis, we observed strong partitions (3.4% and 2.3% divergence, respectively) between adjacent and ecologically distinct habitats, but high genetic connectivity between similar habitats separated by thousands of kilometres. This habitat partitioning is maintained even at a local scale where H. bivittatus lineages are segregated between cold- and warm-water habitats in both Bermuda and Florida. The concordance of evolutionary partitions with habitat types, rather than conventional biogeographical barriers, indicates parapatric ecological speciation, in which adaptation to alternative environmental conditions in adjacent locations overwhelms the homogenizing effect of dispersal. This mechanism can explain the long-standing enigma of high biodiversity in coral reef faunas. PMID:15817431

  14. Sampling genetic diversity in the sympatrically and allopatrically speciating Midas cichlid species complex over a 16 year time series

    PubMed Central

    Bunje, Paul ME; Barluenga, Marta; Meyer, Axel

    2007-01-01

    Background Speciation often occurs in complex or uncertain temporal and spatial contexts. Processes such as reinforcement, allopatric divergence, and assortative mating can proceed at different rates and with different strengths as populations diverge. The Central American Midas cichlid fish species complex is an important case study for understanding the processes of speciation. Previous analyses have demonstrated that allopatric processes led to species formation among the lakes of Nicaragua as well as sympatric speciation that is occurring within at least one crater lake. However, since speciation is an ongoing process and sampling genetic diversity of such lineages can be biased by collection scheme or random factors, it is important to evaluate the robustness of conclusions drawn on individual time samples. Results In order to assess the validity and reliability of inferences based on different genetic samples, we have analyzed fish from several lakes in Nicaragua sampled at three different times over 16 years. In addition, this time series allows us to analyze the population genetic changes that have occurred between lakes, where allopatric speciation has operated, as well as between different species within lakes, some of which have originated by sympatric speciation. Focusing on commonly used genetic markers, we have analyzed both DNA sequences from the complete mitochondrial control region as well as nuclear DNA variation at ten microsatellite loci from these populations, sampled thrice in a 16 year time period, to develop a robust estimate of the population genetic history of these diversifying lineages. Conclusion The conclusions from previous work are well supported by our comprehensive analysis. In particular, we find that the genetic diversity of derived crater lake populations is lower than that of the source population regardless of when and how each population was sampled. Furthermore, changes in various estimates of genetic diversity within lakes

  15. Receptor expression and sympatric speciation: unique olfactory receptor neuron responses in F1 hybrid Rhagoletis populations.

    PubMed

    Olsson, Shannon B; Linn, Charles E; Michel, Andrew; Dambroski, Hattie R; Berlocher, Stewart H; Feder, Jeffrey L; Roelofs, Wendell L

    2006-10-01

    The Rhagoletis pomonella species complex is one of the foremost examples supporting the occurrence of sympatric speciation. A recent study found that reciprocal F(1) hybrid offspring from different host plant-infesting populations in the complex displayed significantly reduced olfactory host preference in flight-tunnel assays. Behavioral and electrophysiological studies indicate that olfactory cues from host fruit are important chemosensory signals for flies to locate fruit for mating and oviposition. The reduced olfactory abilities of hybrids could therefore constitute a significant post-mating barrier to gene flow among fly populations. The present study investigated the source of changes in the hybrid olfactory system by examining peripheral chemoreception in F(1) hybrid flies, using behaviorally relevant volatiles from the parent host fruit. Single-sensillum electrophysiological analyses revealed significant changes in olfactory receptor neuron (ORN) response specificities in hybrid flies when compared to parent ORN responses. We report that flies from F(1) crosses of apple-, hawthorn- and flowering dogwood-origin populations of R. pomonella exhibited distinct ORN response profiles absent from any parent population. These peripheral alterations in ORN response profiles could result from misexpression of multiple receptors in hybrid neurons as a function of genomic incompatibilities in receptor-gene pathways in parent populations. We conclude that these changes in peripheral chemoreception could impact olfactory host preference and contribute directly to reproductive isolation in the Rhagoletis complex, or could be genetically coupled to other host-associated traits. PMID:16985190

  16. Influence of substrate and pH on the diversity of the aeroterrestrial alga Klebsormidium (Klebsormidiales, Streptophyta): a potentially important factor for sympatric speciation

    PubMed Central

    Ryšánek, David; Holzinger, Andreas; Škaloud, Pavel

    2016-01-01

    Our knowledge of the processes involved in speciation of microalgae remains highly limited. In the present study, we investigated a potential role of ecological speciation processes in diversification of the filamentous green alga Klebsormidium. We examined 12 strains representing four different genotypes. The strains were collected from sandstone and limestone rocks and were cultivated at five different pH levels ranging from pH 4 to pH 8. We determined the responses of the 12 strains to the experimental pH conditions by (1) measuring the effective quantum yield of photosystem II, and (2) determining the growth rates after cultivation at different pH levels. Strong differences were found between the results obtained by these two methods. Direct counting of cells revealed a strong ecological differentiation of strains of Klebsormidium isolated from different substrate types. Strains isolated from limestone showed the highest growth rates at higher pH levels; whereas, the strains isolated from sandstone exhibited two distinct growth responses with optima at pH 5 and 6, respectively. In contrast, the effective quantum yield of photosystem II was always down-regulated at lower pH values, probably due to dissolved inorganic carbon limitation. In general, we determined distinct ecophysiological differentiation among distantly and closely related lineages, thereby corroborating our hypothesis that the sympatric speciation of terrestrial algae is driven by ecological divergence. We clearly showed that pH is a critical ecological factor that influences the diversity of autotrophic protists in terrestrial habitats. PMID:27293301

  17. Linking emergence of fungal plant diseases and ecological speciation

    PubMed Central

    Giraud, Tatiana; Gladieux, Pierre; Gavrilets, Sergey

    2010-01-01

    Emerging diseases represent a growing worldwide problem accompanying global environmental changes, and there is tremendous interest in identifying the factors controlling the appearance and spread of these diseases. Here, we discuss emerging fungal plant diseases, and argue that they often result from host shift speciation, a particular case of ecological speciation. We consider the factors controlling local adaptation and ecological speciation and show that certain life-history traits of many fungal plant pathogens are conducive for rapid ecological speciation, thus favoring the emergence of novel pathogen species adapted to new hosts. We argue that placing the problem of emerging fungal diseases of plants within the context of ecological speciation can significantly improve our understanding of the biological mechanisms governing emergence of such diseases. PMID:20434790

  18. Ecological Impacts of Reverse Speciation in Threespine Stickleback.

    PubMed

    Rudman, Seth M; Schluter, Dolph

    2016-02-22

    Young species are highly prone to extinction via increased gene flow after human-caused environmental changes. This mechanism of biodiversity loss, often termed reverse speciation or introgressive extinction, is of exceptional interest because the parent species are typically highly differentiated ecologically. Reverse speciation events are potentially powerful case studies for the role of evolution in driving ecological changes, as the phenotypic shifts associated with introgressive extinction can be large and they occur over particularly short timescales. Furthermore, reverse speciation can lead to novel phenotypes, which may in turn produce novel ecological effects. Here we investigate the ecological shift associated with reverse speciation in threespine stickleback fish using a field study and a replicated experiment. We find that an instance of introgressive extinction had cascading ecological consequences that altered the abundance of both aquatic prey and the pupating aquatic insects that emerged into the terrestrial ecosystem. The community and ecosystem impacts of reverse speciation were novel, and yet they were also predictable based on ecological and morphological considerations. The study suggests that knowledge about the community ecology and changes in functional morphology of a dominant species may lead to some predictive power for the ecological effects of evolutionary change. Moreover, the rapid nature and resultant ecological impacts associated with reverse speciation demonstrates the interplay between biodiversity, evolutionary change, and ecosystem function. PMID:26804556

  19. Tracing the first step to speciation: ecological and genetic differentiation of a salamander population in a small forest.

    PubMed

    Steinfartz, Sebastian; Weitere, Markus; Tautz, Diethard

    2007-11-01

    Mechanisms and processes of ecologically driven adaptive speciation are best studied in natural situations where the splitting process is still occurring, i.e. before complete reproductive isolation is achieved. Here, we present a case of an early stage of adaptive differentiation under sympatric conditions in the fire salamander, Salamandra salamandra, that allows inferring the underlying processes for the split. Larvae of S. salamandra normally mature in small streams until metamorphosis, but in an old, continuous forest area near Bonn (the Kottenforst), we found salamander larvae not only in small streams but also in shallow ponds, which are ecologically very different from small streams. Common-environment experiments with larvae from both habitat types reveal specific adaptations to these different ecological conditions. Mitochondrial and microsatellite analyses show that the two ecologically differentiated groups also show signs of genetic differentiation. A parallel analysis of animals from a neighbouring much larger forest area (the Eifel), in which larvae mature only in streams, shows no signs of genetic differentiation, indicating that gene flow between ecologically similar types can occur over large distances. Hence, geographical factors cannot explain the differential larval habitat adaptations in the Kottenforst, in particular since adult life and mating of S. salamandra is strictly terrestrial and not associated with larval habitats. We propose therefore that the evolution of these adaptations was coupled with the evolution of cues for assortative mating which would be in line with models of sympatric speciation that suggest a co-evolution of habitat adaptations and associated mating signals. PMID:17877714

  20. The role of local ecology during hybridization at the initial stages of ecological speciation in a marine snail.

    PubMed

    Galindo, J; Martínez-Fernández, M; Rodríguez-Ramilo, S T; Rolán-Alvarez, E

    2013-07-01

    Hybrid zones of ecologically divergent populations are ideal systems to study the interaction between natural selection and gene flow during the initial stages of speciation. Here, we perform an amplified fragment length polymorphism (AFLP) genome scan in parallel hybrid zones between divergent ecotypes of the marine snail Littorina saxatilis, which is considered a model case for the study of ecological speciation. Ridged-Banded (RB) and Smooth-Unbanded (SU) ecotypes are adapted to different shore levels and microhabitats, although they present a sympatric distribution at the mid-shore where they meet and mate (partially assortatively). We used shell morphology, outlier and nonoutlier AFLP loci from RB, SU and hybrid specimens captured in sympatry to determine the level of phenotypic and genetic introgression. We found different levels of introgression at parallel hybrid zones and nonoutlier loci showed more gene flow with greater phenotypic introgression. These results were independent from the phylogeography of the studied populations, but not from the local ecological conditions. Genetic variation at outlier loci was highly correlated with phenotypic variation. In addition, we used the relationship between genetic and phenotypic variation to estimate the heritability of morphological traits and to identify potential Quantitative Trait Loci to be confirmed in future crosses. These results suggest that ecology (exogenous selection) plays an important role in this hybrid zone. Thus, ecologically based divergent natural selection is responsible, simultaneously, for both ecotype divergence and hybridization. On the other hand, genetic introgression occurs only at neutral loci (nonoutliers). In the future, genome-wide studies and controlled crosses would give more valuable information about this process of speciation in the face of gene flow. PMID:23663115

  1. Novel trophic niches drive variable progress towards ecological speciation within an adaptive radiation of pupfishes.

    PubMed

    Martin, Christopher H; Feinstein, Laura C

    2014-04-01

    Adaptive radiation is recognized by a rapid burst of phenotypic, ecological and species diversification. However, it is unknown whether different species within an adaptive radiation evolve reproductive isolation at different rates. We compared patterns of genetic differentiation between nascent species within an adaptive radiation of Cyprinodon pupfishes using genotyping by sequencing. Similar to classic adaptive radiations, this clade exhibits rapid morphological diversification rates and two species are novel trophic specialists, a scale-eater and hard-shelled prey specialist (durophage), yet the radiation is <10 000 years old. Both specialists and an abundant generalist species all coexist in the benthic zone of lakes on San Salvador Island, Bahamas. Based on 13 912 single-nucleotide polymorphisms (SNPs), we found consistent differences in genetic differentiation between each specialist species and the generalist across seven lakes. The scale-eater showed the greatest genetic differentiation and clustered by species across lakes, whereas durophage populations often clustered with sympatric generalist populations, consistent with parallel speciation across lakes. However, we found strong evidence of admixture between durophage populations in different lakes, supporting a single origin of this species and genome-wide introgression with sympatric generalist populations. We conclude that the scale-eater is further along the speciation-with-gene-flow continuum than the durophage and suggest that different adaptive landscapes underlying these two niche environments drive variable progress towards speciation within the same habitat. Our previous measurements of fitness surfaces in these lakes support this conclusion: the scale-eating fitness peak may be more distant than the durophage peak on the complex adaptive landscape driving adaptive radiation. PMID:24393262

  2. Postzygotic isolating factor in sympatric speciation in Rhagoletis flies: reduced response of hybrids to parental host-fruit odors.

    PubMed

    Linn, Charles E; Dambroski, Hattie R; Feder, Jeffrey L; Berlocher, Stewart H; Nojima, Satoshi; Roelofs, Wendell L

    2004-12-21

    Rhagoletis pomonella is a model for sympatric speciation (divergence without geographic isolation) by means of host-plant shifts. Many Rhagoletis species are known to use fruit odor as a key olfactory cue to distinguish among their respective host plants. Because Rhagoletis rendezvous on or near the unabscised fruit of their hosts to mate, behavioral preferences for fruit odor translate directly into premating reproductive isolation among flies. Here, we report that reciprocal F(1) hybrids between the apple and hawthorn host races of R. pomonella, as well as between the host races and an undescribed sibling species infesting Cornus florida (flowering dogwood) do not respond to host fruit volatiles in wind-tunnel assays at doses that elicit maximal directed flight in parental flies. The reduced ability of hybrids to orient to fruit volatiles could result from a conflict between neural pathways for preference and avoidance behaviors, and it suggests that hybrids might suffer a fitness disadvantage for finding fruit in nature. Therefore, host-specific mating may play a dual role as an important postzygotic as well as a premating reproductive barrier to isolate sympatric Rhagoletis flies. PMID:15591346

  3. The role of genome and gene regulatory network canalization in the evolution of multi-trait polymorphisms and sympatric speciation

    PubMed Central

    2009-01-01

    Background Sexual reproduction has classically been considered as a barrier to the buildup of discrete phenotypic differentiation. This notion has been confirmed by models of sympatric speciation in which a fixed genetic architecture and a linear genotype phenotype mapping were assumed. In this paper we study the influence of a flexible genetic architecture and non-linear genotype phenotype map on differentiation under sexual reproduction. We use an individual based model in which organisms have a genome containing genes and transcription factor binding sites. Mutations involve single genes or binding sites or stretches of genome. The genome codes for a regulatory network that determines the gene expression pattern and hence the phenotype of the organism, resulting in a non-linear genotype phenotype map. The organisms compete in a multi-niche environment, imposing selection for phenotypic differentiation. Results We find as a generic outcome the evolution of discrete clusters of organisms adapted to different niches, despite random mating. Organisms from different clusters are distinct on the genotypic, the network and the phenotypic level. However, the genome and network differences are constrained to a subset of the genome locations, a process we call genotypic canalization. We demonstrate how this canalization leads to an increased robustness to recombination and increasing hybrid fitness. Finally, in case of assortative mating, we explain how this canalization increases the effectiveness of assortativeness. Conclusion We conclude that in case of a flexible genetic architecture and a non-linear genotype phenotype mapping, sexual reproduction does not constrain phenotypic differentiation, but instead constrains the genotypic differences underlying it. We hypothesize that, as genotypic canalization enables differentiation despite random mating and increases the effectiveness of assortative mating, sympatric speciation is more likely than is commonly suggested

  4. Speciation, Ecological Opportunity, and Latitude (American Society of Naturalists Address).

    PubMed

    Schluter, Dolph

    2016-01-01

    Evolutionary hypotheses to explain the greater numbers of species in the tropics than the temperate zone include greater age and area, higher temperature and metabolic rates, and greater ecological opportunity. These ideas make contrasting predictions about the relationship between speciation processes and latitude, which I elaborate and evaluate. Available data suggest that per capita speciation rates are currently highest in the temperate zone and that diversification rates (speciation minus extinction) are similar between latitudes. In contrast, clades whose oldest analyzed dates precede the Eocene thermal maximum, when the extent of the tropics was much greater than today, tend to show highest speciation and diversification rates in the tropics. These findings are consistent with age and area, which is alone among hypotheses in predicting a time trend. Higher recent speciation rates in the temperate zone than the tropics suggest an additional response to high ecological opportunity associated with low species diversity. These broad patterns are compelling but provide limited insights into underlying mechanisms, arguing that studies of speciation processes along the latitudinal gradient will be vital. Using threespine stickleback in depauperate northern lakes as an example, I show how high ecological opportunity can lead to rapid speciation. The results support a role for ecological opportunity in speciation, but its importance in the evolution of the latitudinal gradient remains uncertain. I conclude that per capita evolutionary rates are no longer higher in the tropics than the temperate zone. Nevertheless, the vast numbers of species that have already accumulated in the tropics ensure that total rate of species production remains highest there. Thus, tropical evolutionary momentum helps to perpetuate the steep latitudinal biodiversity gradient. PMID:26814593

  5. Ecological niche modeling of sympatric krill predators around Marguerite Bay, Western Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Friedlaender, Ari S.; Johnston, David W.; Fraser, William R.; Burns, Jennifer; Halpin, Patrick N.; Costa, Daniel P.

    2011-07-01

    Adélie penguins ( Pygoscelis adeliae), carabeater seals ( Lobodon carcinophagus), humpback ( Megaptera novaeangliae), and minke whales ( Balaenoptera bonaernsis) are found in the waters surrounding the Western Antarctic Peninsula. Each species relies primarily on Antarctic krill ( Euphausia superba) and has physiological constraints and foraging behaviors that dictate their ecological niches. Understanding the degree of ecological overlap between sympatric krill predators is critical to understanding and predicting the impacts on climate-driven changes to the Antarctic marine ecosystem. To explore ecological relationships amongst sympatric krill predators, we developed ecological niche models using a maximum entropy modeling approach (Maxent) that allows the integration of data collected by a variety of means (e.g. satellite-based locations and visual observations). We created spatially explicit probability distributions for the four krill predators in fall 2001 and 2002 in conjunction with a suite of environmental variables. We find areas within Marguerite Bay with high krill predator occurrence rates or biological hot spots. We find the modeled ecological niches for Adélie penguins and crabeater seals may be affected by their physiological needs to haul-out on substrate. Thus, their distributions may be less dictated by proximity to prey and more so by physical features that over time provide adequate access to prey. Humpback and minke whales, being fully marine and having greater energetic demands, occupy ecological niches more directly proximate to prey. We also find evidence to suggest that the amount of overlap between modeled niches is relatively low, even for species with similar energetic requirements. In a rapidly changing and variable environment, our modeling work shows little indication that krill predators maintain similar ecological niches across years around Marguerite Bay. Given the amount of variability in the marine environment around the

  6. Tracking niche variation over millennial timescales in sympatric killer whale lineages

    PubMed Central

    Foote, Andrew D.; Newton, Jason; Ávila-Arcos, María C.; Kampmann, Marie-Louise; Samaniego, Jose A.; Post, Klaas; Rosing-Asvid, Aqqalu; Sinding, Mikkel-Holger S.; Gilbert, M. Thomas P.

    2013-01-01

    Niche variation owing to individual differences in ecology has been hypothesized to be an early stage of sympatric speciation. Yet to date, no study has tracked niche width over more than a few generations. In this study, we show the presence of isotopic niche variation over millennial timescales and investigate the evolutionary outcomes. Isotopic ratios were measured from tissue samples of sympatric killer whale Orcinus orca lineages from the North Sea, spanning over 10 000 years. Isotopic ratios spanned a range similar to the difference in isotopic values of two known prey items, herring Clupea harengus and harbour seal Phoca vitulina. Two proxies of the stage of speciation, lineage sorting of mitogenomes and genotypic clustering, were both weak to intermediate indicating that speciation has made little progress. Thus, our study confirms that even with the necessary ecological conditions, i.e. among-individual variation in ecology, it is difficult for sympatric speciation to progress in the face of gene flow. In contrast to some theoretical models, our empirical results suggest that sympatric speciation driven by among-individual differences in ecological niche is a slow process and may not reach completion. We argue that sympatric speciation is constrained in this system owing to the plastic nature of the behavioural traits under selection when hunting either mammals or fish. PMID:23945688

  7. Tracking niche variation over millennial timescales in sympatric killer whale lineages.

    PubMed

    Foote, Andrew D; Newton, Jason; Ávila-Arcos, María C; Kampmann, Marie-Louise; Samaniego, Jose A; Post, Klaas; Rosing-Asvid, Aqqalu; Sinding, Mikkel-Holger S; Gilbert, M Thomas P

    2013-10-01

    Niche variation owing to individual differences in ecology has been hypothesized to be an early stage of sympatric speciation. Yet to date, no study has tracked niche width over more than a few generations. In this study, we show the presence of isotopic niche variation over millennial timescales and investigate the evolutionary outcomes. Isotopic ratios were measured from tissue samples of sympatric killer whale Orcinus orca lineages from the North Sea, spanning over 10 000 years. Isotopic ratios spanned a range similar to the difference in isotopic values of two known prey items, herring Clupea harengus and harbour seal Phoca vitulina. Two proxies of the stage of speciation, lineage sorting of mitogenomes and genotypic clustering, were both weak to intermediate indicating that speciation has made little progress. Thus, our study confirms that even with the necessary ecological conditions, i.e. among-individual variation in ecology, it is difficult for sympatric speciation to progress in the face of gene flow. In contrast to some theoretical models, our empirical results suggest that sympatric speciation driven by among-individual differences in ecological niche is a slow process and may not reach completion. We argue that sympatric speciation is constrained in this system owing to the plastic nature of the behavioural traits under selection when hunting either mammals or fish. PMID:23945688

  8. The role of gene expression in ecological speciation

    PubMed Central

    Pavey, Scott A; Collin, Hélène; Nosil, Patrik; Rogers, Sean M

    2010-01-01

    Ecological speciation is the process by which barriers to gene flow between populations evolve due to adaptive divergence via natural selection. A relatively unexplored area in ecological speciation is the role of gene expression. Gene expression may be associated with ecologically important phenotypes not evident from morphology and play a role during colonization of new environments. Here we review two potential roles of gene expression in ecological speciation: (1) its indirect role in facilitating population persistence and (2) its direct role in contributing to genetically based reproductive isolation. We find indirect evidence that gene expression facilitates population persistence, but direct tests are lacking. We also find clear examples of gene expression having effects on phenotypic traits and adaptive genetic divergence, but links to the evolution of reproductive isolation itself remain indirect. Gene expression during adaptive divergence seems to often involve complex genetic architectures controlled by gene networks, regulatory regions, and “eQTL hotspots.” Nonetheless, we review how approaches for isolating the functional mutations contributing to adaptive divergence are proving to be successful. The study of gene expression has promise for increasing our understanding ecological speciation, particularly when integrative approaches are applied. PMID:20860685

  9. Ecological speciation in postglacial European whitefish: rapid adaptive radiations into the littoral, pelagic, and profundal lake habitats

    PubMed Central

    Præbel, Kim; Knudsen, Rune; Siwertsson, Anna; Karhunen, Markku; Kahilainen, Kimmo K; Ovaskainen, Otso; Østbye, Kjartan; Peruzzi, Stefano; Fevolden, Svein-Erik; Amundsen, Per-Arne

    2013-01-01

    Understanding how a monophyletic lineage of a species diverges into several adaptive forms has received increased attention in recent years, but the underlying mechanisms in this process are still under debate. Postglacial fishes are excellent model organisms for exploring this process, especially the initial stages of ecological speciation, as postglacial lakes represent replicated discrete environments with variation in available niches. Here, we combine data of niche utilization, trophic morphology, and 17 microsatellite loci to investigate the diversification process of three sympatric European whitefish morphs from three northern Fennoscandian lakes. The morphological divergence in the gill raker number among the whitefish morphs was related to the utilization of different trophic niches and was associated with reproductive isolation within and across lakes. The intralacustrine comparison of whitefish morphs showed that these systems represent two levels of adaptive divergence: (1) a consistent littoral–pelagic resource axis; and (2) a more variable littoral–profundal resource axis. The results also indicate that the profundal whitefish morph has diverged repeatedly from the ancestral littoral whitefish morph in sympatry in two different watercourses. In contrast, all the analyses performed revealed clustering of the pelagic whitefish morphs across lakes suggesting parallel postglacial immigration with the littoral whitefish morph into each lake. Finally, the analyses strongly suggested that the trophic adaptive trait, number of gill rakers, was under diversifying selection in the different whitefish morphs. Together, the results support a complex evolutionary scenario where ecological speciation acts, but where both allopatric (colonization history) and sympatric (within watercourse divergence) processes are involved. PMID:24455129

  10. Ecological speciation in postglacial European whitefish: rapid adaptive radiations into the littoral, pelagic, and profundal lake habitats.

    PubMed

    Præbel, Kim; Knudsen, Rune; Siwertsson, Anna; Karhunen, Markku; Kahilainen, Kimmo K; Ovaskainen, Otso; Ostbye, Kjartan; Peruzzi, Stefano; Fevolden, Svein-Erik; Amundsen, Per-Arne

    2013-12-01

    Understanding how a monophyletic lineage of a species diverges into several adaptive forms has received increased attention in recent years, but the underlying mechanisms in this process are still under debate. Postglacial fishes are excellent model organisms for exploring this process, especially the initial stages of ecological speciation, as postglacial lakes represent replicated discrete environments with variation in available niches. Here, we combine data of niche utilization, trophic morphology, and 17 microsatellite loci to investigate the diversification process of three sympatric European whitefish morphs from three northern Fennoscandian lakes. The morphological divergence in the gill raker number among the whitefish morphs was related to the utilization of different trophic niches and was associated with reproductive isolation within and across lakes. The intralacustrine comparison of whitefish morphs showed that these systems represent two levels of adaptive divergence: (1) a consistent littoral-pelagic resource axis; and (2) a more variable littoral-profundal resource axis. The results also indicate that the profundal whitefish morph has diverged repeatedly from the ancestral littoral whitefish morph in sympatry in two different watercourses. In contrast, all the analyses performed revealed clustering of the pelagic whitefish morphs across lakes suggesting parallel postglacial immigration with the littoral whitefish morph into each lake. Finally, the analyses strongly suggested that the trophic adaptive trait, number of gill rakers, was under diversifying selection in the different whitefish morphs. Together, the results support a complex evolutionary scenario where ecological speciation acts, but where both allopatric (colonization history) and sympatric (within watercourse divergence) processes are involved. PMID:24455129

  11. Ecology of Speciation in the Genus Bacillus

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Microbial ecologists and systematists are challenged to discover the early ecological changes that drive the splitting of one bacterial population into two ecologically distinct populations. We have aimed to identify newly divergent lineages (“ecotypes”) bearing the dynamic properties attributed to...

  12. Genomic Signatures of Speciation in Sympatric and Allopatric Hawaiian Picture-Winged Drosophila

    PubMed Central

    Kang, Lin; Settlage, Robert; McMahon, Wyatt; Michalak, Katarzyna; Tae, Hongseok; Garner, Harold R.; Stacy, Elizabeth A.; Price, Donald K.; Michalak, Pawel

    2016-01-01

    The Hawaiian archipelago provides a natural arena for understanding adaptive radiation and speciation. The Hawaiian Drosophila are one of the most diverse endemic groups in Hawaiì with up to 1,000 species. We sequenced and analyzed entire genomes of recently diverged species of Hawaiian picture-winged Drosophila, Drosophila silvestris and Drosophila heteroneura from Hawaiì Island, in comparison with Drosophila planitibia, their sister species from Maui, a neighboring island where a common ancestor of all three had likely occurred. Genome-wide single nucleotide polymorphism patterns suggest the more recent origin of D. silvestris and D. heteroneura, as well as a pervasive influence of positive selection on divergence of the three species, with the signatures of positive selection more prominent in sympatry than allopatry. Positively selected genes were significantly enriched for functional terms related to sensory detection and mating, suggesting that sexual selection played an important role in speciation of these species. In particular, sequence variation in Olfactory receptor and Gustatory receptor genes seems to play a major role in adaptive radiation in Hawaiian pictured-winged Drosophila. PMID:27189993

  13. Genomic Signatures of Speciation in Sympatric and Allopatric Hawaiian Picture-Winged Drosophila.

    PubMed

    Kang, Lin; Settlage, Robert; McMahon, Wyatt; Michalak, Katarzyna; Tae, Hongseok; Garner, Harold R; Stacy, Elizabeth A; Price, Donald K; Michalak, Pawel

    2016-01-01

    The Hawaiian archipelago provides a natural arena for understanding adaptive radiation and speciation. The Hawaiian Drosophila are one of the most diverse endemic groups in Hawaiì with up to 1,000 species. We sequenced and analyzed entire genomes of recently diverged species of Hawaiian picture-winged Drosophila, Drosophila silvestris and Drosophila heteroneura from Hawaiì Island, in comparison with Drosophila planitibia, their sister species from Maui, a neighboring island where a common ancestor of all three had likely occurred. Genome-wide single nucleotide polymorphism patterns suggest the more recent origin of D. silvestris and D. heteroneura, as well as a pervasive influence of positive selection on divergence of the three species, with the signatures of positive selection more prominent in sympatry than allopatry. Positively selected genes were significantly enriched for functional terms related to sensory detection and mating, suggesting that sexual selection played an important role in speciation of these species. In particular, sequence variation in Olfactory receptor and Gustatory receptor genes seems to play a major role in adaptive radiation in Hawaiian pictured-winged Drosophila. PMID:27189993

  14. A recombination suppressor contributes to ecological speciation in OSTRINIA moths.

    PubMed

    Wadsworth, C B; Li, X; Dopman, E B

    2015-06-01

    Despite unparalleled access to species' genomes in our post-genomic age, we often lack adequate biological explanations for a major hallmark of the speciation process-genetic divergence. In the presence of gene flow, chromosomal rearrangements such as inversions are thought to promote divergence and facilitate speciation by suppressing recombination. Using a combination of genetic crosses, phenotyping of a trait underlying ecological isolation, and population genetic analysis of wild populations, we set out to determine whether evidence supports a role for recombination suppressors during speciation between the Z and E strains of European corn borer moth (Ostrinia nubilalis). Our results are consistent with the presence of an inversion that has contributed to accumulation of ecologically adaptive alleles and genetic differentiation across roughly 20% of the Ostrinia sex chromosome (~4 Mb). Patterns in Ostrinia suggest that chromosomal divergence may involve two separate phases-one driving its transient origin through local adaptation and one determining its stable persistence through differential introgression. As the evolutionary rate of rearrangements in lepidopteran genomes appears to be one of the fastest among eukaryotes, structural mutations may have had a disproportionate role during adaptive divergence and speciation in Ostrinia and in other moths and butterflies. PMID:25626887

  15. A recombination suppressor contributes to ecological speciation in OSTRINIA moths

    PubMed Central

    Wadsworth, C B; Li, X; Dopman, E B

    2015-01-01

    Despite unparalleled access to species' genomes in our post-genomic age, we often lack adequate biological explanations for a major hallmark of the speciation process—genetic divergence. In the presence of gene flow, chromosomal rearrangements such as inversions are thought to promote divergence and facilitate speciation by suppressing recombination. Using a combination of genetic crosses, phenotyping of a trait underlying ecological isolation, and population genetic analysis of wild populations, we set out to determine whether evidence supports a role for recombination suppressors during speciation between the Z and E strains of European corn borer moth (Ostrinia nubilalis). Our results are consistent with the presence of an inversion that has contributed to accumulation of ecologically adaptive alleles and genetic differentiation across roughly 20% of the Ostrinia sex chromosome (~4 Mb). Patterns in Ostrinia suggest that chromosomal divergence may involve two separate phases—one driving its transient origin through local adaptation and one determining its stable persistence through differential introgression. As the evolutionary rate of rearrangements in lepidopteran genomes appears to be one of the fastest among eukaryotes, structural mutations may have had a disproportionate role during adaptive divergence and speciation in Ostrinia and in other moths and butterflies. PMID:25626887

  16. Case studies and mathematical models of ecological speciation. 4. Hybrid speciation in butterflies in a jungle.

    PubMed

    Duenez-Guzman, Edgar A; Mavárez, Jesus; Vose, Michael D; Gavrilets, Sergey

    2009-10-01

    We build a spatial individual-based multilocus model of homoploid hybrid speciation tailored for a tentative case of hybrid origin of Heliconius heurippa from H. melpomene and H. cydno in South America. Our model attempts to account for empirical patterns and data on genetic incompatibility, mating preferences and selection by predation (both based on coloration patterns), habitat preference, and local adaptation for all three Heliconius species. Using this model, we study the likelihood of recombinational speciation and identify the effects of various ecological and genetic parameters on the dynamics, patterns, and consequences of hybrid ecological speciation. Overall, our model supports the possibility of hybrid origin of H. heurippa under certain conditions. The most plausible scenario would include hybridization between H. melpomene and H. cydno in an area geographically isolated from the rest of both parental species with subsequent long-lasting geographic isolation of the new hybrid species, followed by changes in the species ranges, the secondary contact, and disappearance of H. melpomene-type ecomorph in the hybrid species. However, much more work (both empirical and theoretical) is necessary to be able to make more definite conclusions on the importance of homoploid hybrid speciation in animals. PMID:19545268

  17. Emergence of novel fungal pathogens by ecological speciation: importance of the reduced viability of immigrants.

    PubMed

    Gladieux, Pierre; Guérin, Fabien; Giraud, Tatiana; Caffier, Valérie; Lemaire, Christophe; Parisi, Luciana; Didelot, Frédérique; LE Cam, Bruno

    2011-11-01

    Expanding global trade and the domestication of ecosystems have greatly accelerated the rate of emerging infectious fungal diseases, and host-shift speciation appears to be a major route for disease emergence. There is therefore an increased interest in identifying the factors that drive the evolution of reproductive isolation between populations adapting to different hosts. Here, we used genetic markers and cross-inoculations to assess the level of gene flow and investigate barriers responsible for reproductive isolation between two sympatric populations of Venturia inaequalis, the fungal pathogen causing apple scab disease, one of the fungal populations causing a recent emerging disease on resistant varieties. Our results showed the maintenance over several years of strong and stable differentiation between the two populations in the same orchards, suggesting ongoing ecological divergence following a host shift. We identified strong selection against immigrants (i.e. host specificity) from different host varieties as the strongest and likely most efficient barrier to gene flow between local and emerging populations. Cross-variety disease transmission events were indeed rare in the field and cross-inoculation tests confirmed high host specificity. Because the fungus mates within its host after successful infection and because pathogenicity-related loci prevent infection of nonhost trees, adaptation to specific hosts may alone maintain both genetic differentiation between and adaptive allelic combinations within sympatric populations parasitizing different apple varieties, thus acting as a 'magic trait'. Additional intrinsic and extrinsic postzygotic barriers might complete reproductive isolation and explain why the rare migrants and F1 hybrids detected do not lead to pervasive gene flow across years. PMID:21967446

  18. Comparative Landscape Genetics of Three Closely Related Sympatric Hesperid Butterflies with Diverging Ecological Traits

    PubMed Central

    Engler, Jan O.; Balkenhol, Niko; Filz, Katharina J.; Habel, Jan C.; Rödder, Dennis

    2014-01-01

    To understand how landscape characteristics affect gene flow in species with diverging ecological traits, it is important to analyze taxonomically related sympatric species in the same landscape using identical methods. Here, we present such a comparative landscape genetic study involving three closely related Hesperid butterflies of the genus Thymelicus that represent a gradient of diverging ecological traits. We analyzed landscape effects on their gene flow by deriving inter-population connectivity estimates based on different species distribution models (SDMs), which were calculated from multiple landscape parameters. We then used SDM output maps to calculate circuit-theoretic connectivity estimates and statistically compared these estimates to actual genetic differentiation in each species. We based our inferences on two different analytical methods and two metrics of genetic differentiation. Results indicate that land use patterns influence population connectivity in the least mobile specialist T. acteon. In contrast, populations of the highly mobile generalist T. lineola were panmictic, lacking any landscape related effect on genetic differentiation. In the species with ecological traits in between those of the congeners, T. sylvestris, climate has a strong impact on inter-population connectivity. However, the relative importance of different landscape factors for connectivity varies when using different metrics of genetic differentiation in this species. Our results show that closely related species representing a gradient of ecological traits also show genetic structures and landscape genetic relationships that gradually change from a geographical macro- to micro-scale. Thus, the type and magnitude of landscape effects on gene flow can differ strongly even among closely related species inhabiting the same landscape, and depend on their relative degree of specialization. In addition, the use of different genetic differentiation metrics makes it possible to

  19. Habitat and Burrow System Characteristics of the Blind Mole Rat Spalax galili in an Area of Supposed Sympatric Speciation

    PubMed Central

    Lövy, Matěj; Šklíba, Jan; Hrouzková, Ema; Dvořáková, Veronika; Nevo, Eviatar; Šumbera, Radim

    2015-01-01

    A costly search for food in subterranean rodents resulted in various adaptations improving their foraging success under given ecological conditions. In Spalax ehrenbergi superspecies, adaptations to local ecological conditions can promote speciation, which was recently supposed to occur even in sympatry at sites where two soil types of contrasting characteristics abut each other. Quantitative description of ecological conditions in such a site has been, nevertheless, missing. We measured characteristics of food supply and soil within 16 home ranges of blind mole rats Spalax galili in an area subdivided into two parts formed by basaltic soil and pale rendzina. We also mapped nine complete mole rat burrow systems to compare burrowing patterns between the soil types. Basaltic soil had a higher food supply and was harder than rendzina even under higher moisture content and lower bulk density. Population density of mole rats was five-times lower in rendzina, possibly due to the lower food supply and higher cover of Sarcopoterium shrubs which seem to be avoided by mole rats. A combination of food supply and soil parameters probably influences burrowing patterns resulting in shorter and more complex burrow systems in basaltic soil. PMID:26192762

  20. Habitat and Burrow System Characteristics of the Blind Mole Rat Spalax galili in an Area of Supposed Sympatric Speciation.

    PubMed

    Lövy, Matěj; Šklíba, Jan; Hrouzková, Ema; Dvořáková, Veronika; Nevo, Eviatar; Šumbera, Radim

    2015-01-01

    A costly search for food in subterranean rodents resulted in various adaptations improving their foraging success under given ecological conditions. In Spalax ehrenbergi superspecies, adaptations to local ecological conditions can promote speciation, which was recently supposed to occur even in sympatry at sites where two soil types of contrasting characteristics abut each other. Quantitative description of ecological conditions in such a site has been, nevertheless, missing. We measured characteristics of food supply and soil within 16 home ranges of blind mole rats Spalax galili in an area subdivided into two parts formed by basaltic soil and pale rendzina. We also mapped nine complete mole rat burrow systems to compare burrowing patterns between the soil types. Basaltic soil had a higher food supply and was harder than rendzina even under higher moisture content and lower bulk density. Population density of mole rats was five-times lower in rendzina, possibly due to the lower food supply and higher cover of Sarcopoterium shrubs which seem to be avoided by mole rats. A combination of food supply and soil parameters probably influences burrowing patterns resulting in shorter and more complex burrow systems in basaltic soil. PMID:26192762

  1. Multigene analysis suggests ecological speciation in the fungal pathogen Claviceps purpurea

    PubMed Central

    DOUHAN, G. W.; SMITH, M. E.; HUYRN, K. L.; WESTBROOK, A.; Beerli, P.; FISHER, A. J.

    2008-01-01

    Claviceps purpurea is an important pathogen of grasses and source of novel chemical compounds. Three groups within this species (G1, G2, and G3) have been recognized based on habitat association, sclerotia and conidia morphology, and alkaloid production. These groups have further been supported by RAPD and AFLP markers, suggesting this species may be more accurately described as a species complex. However, all divergent ecotypes can coexist in sympatric populations with no obvious physical barriers to prevent gene flow. In this study, we used both phylogenetic and population genetic analyses to test for speciation within C. purpurea using DNA sequences from ITS, a RAS-like locus, and a portion of beta-tubulin. The G1 types are significantly divergent from the G2/G3 types based on each of the three loci and the combined dataset, whereas the G2/G3 types are more integrated with one another. Although the G2 and G3 lineages have not diverged as much as the G1 lineage based on DNA sequence data, the use of three DNA loci does reliably separate the G2 and G3 lineages. However, the population genetic analyses strongly suggest little to no gene flow occurring between the different ecotypes and we argue that this process is driven by adaptations to ecological habitats; G1 isolates are associated with terrestrial grasses, G2 isolates are found in wet and shady environments, and G3 isolates are found in salt marsh habitats. PMID:18373531

  2. Assortative flocking in crossbills and implications for ecological speciation

    PubMed Central

    Smith, Julie W.; Sjoberg, Stephanie M.; Mueller, Matthew C.; Benkman, Craig W.

    2012-01-01

    How reproductive isolation is related to divergent natural selection is a central question in speciation. Here, we focus on several ecologically specialized taxa or ‘call types’ of red crossbills (Loxia curvirostra complex), one of the few groups of birds providing much evidence for ecological speciation. Call types differ in bill sizes and feeding capabilities, and also differ in vocalizations, such that contact calls provide information on crossbill phenotype. We found that two call types of red crossbills were more likely to approach playbacks of their own call type than those of heterotypics, and that their propensity to approach heterotypics decreased with increasing divergence in bill size. Although call similarity also decreased with increasing divergence in bill size, comparisons of responses to familiar versus unfamiliar call types indicate that the decrease in the propensity to approach heterotypics with increasing divergence in bill size was a learned response, and not a by-product of calls diverging pleiotropically as bill size diverged. Because crossbills choose mates while in flocks, assortative flocking could lead indirectly to assortative mating as a by-product. These patterns of association therefore provide a mechanism by which increasing divergent selection can lead to increasing reproductive isolation. PMID:22915674

  3. Assortative flocking in crossbills and implications for ecological speciation.

    PubMed

    Smith, Julie W; Sjoberg, Stephanie M; Mueller, Matthew C; Benkman, Craig W

    2012-10-22

    How reproductive isolation is related to divergent natural selection is a central question in speciation. Here, we focus on several ecologically specialized taxa or 'call types' of red crossbills (Loxia curvirostra complex), one of the few groups of birds providing much evidence for ecological speciation. Call types differ in bill sizes and feeding capabilities, and also differ in vocalizations, such that contact calls provide information on crossbill phenotype. We found that two call types of red crossbills were more likely to approach playbacks of their own call type than those of heterotypics, and that their propensity to approach heterotypics decreased with increasing divergence in bill size. Although call similarity also decreased with increasing divergence in bill size, comparisons of responses to familiar versus unfamiliar call types indicate that the decrease in the propensity to approach heterotypics with increasing divergence in bill size was a learned response, and not a by-product of calls diverging pleiotropically as bill size diverged. Because crossbills choose mates while in flocks, assortative flocking could lead indirectly to assortative mating as a by-product. These patterns of association therefore provide a mechanism by which increasing divergent selection can lead to increasing reproductive isolation. PMID:22915674

  4. Ecological divergence of two sympatric lineages of Buggy Creek virus, an arbovirus associated with birds.

    PubMed

    Brown, Charles R; Padhi, Abinash; Moore, Amy T; Brown, Mary Bomberger; Foster, Jerome E; Pfeffer, Martin; O'Brien, Valerie A; Komar, Nicholas

    2009-11-01

    Most arthropod-borne viruses (arboviruses) show distinct serological subtypes or evolutionary lineages, with the evolution of different strains often assumed to reflect differences in ecological selection pressures. Buggy Creek virus (BCRV) is an unusual RNA virus (Togaviridae, Alphavirus) that is associated primarily with a cimicid swallow bug (Oeciacus vicarius) as its vector and the Cliff Swallow (Petrochelidon pyrrhonota) and the introduced House Sparrow (Passer domesticus) as its amplifying hosts. There are two sympatric lineages of BCRV (lineages A and B) that differ from each other by > 6% at the nucleotide level. Analysis of 385 BCRV isolates all collected from bug vectors at a study site in southwestern Nebraska, USA, showed that the lineages differed in their peak times of seasonal occurrence within a summer. Lineage A was more likely to be found at recently established colonies, at those in culverts (rather than on highway bridges), and at those with invasive House Sparrows, and in bugs on the outsides of nests. Genetic diversity of lineage A increased with bird colony size and at sites with House Sparrows, while that of lineage B decreased with colony size and was unaffected by House Sparrows. Lineage A was more cytopathic on mammalian cells than was lineage B. These two lineages have apparently diverged in their transmission dynamics, with lineage A possibly more dependent on birds and lineage B perhaps more a bug virus. The long-standing association between Cliff Swallows and BCRV may have selected for immunological resistance to the virus by swallows and thus promoted the evolution of the more bug-adapted lineage B. In contrast, the recent arrival of the introduced House Sparrow and its high competence as a BCRV amplifying host may be favoring the more bird-dependent lineage A. PMID:19967872

  5. On the scent of standing variation for speciation: behavioral evidence for native sympatric host races of Rhagoletis pomonella (Diptera: Tephritidae) in the southern United States.

    PubMed

    Powell, Thomas H Q; Cha, Dong H; Linn, Charles E; Feder, Jeffrey L

    2012-09-01

    Standing variation can be critical for speciation. Here, we investigate the origins of fruit odor discrimination for Rhagoletis pomonella underlying the fly's sympatric shift in the northeastern United States from downy hawthorn (Crataegus mollis) to apple (Malus domestica). Because R. pomonella mate on host fruit, preferences for natal fruit volatiles generate prezygotic isolation. Apples emit volatiles that appear to be missing from gas chromatography/electroantennographic detection profiles for flies infesting downy hawthorns, raising the question of how R. pomonella evolved a preference for apple. In the southern United States, R. pomonella attacks several native hawthorns. Behaviorally active volatile blends for R. pomonella infesting southern hawthorns contain the missing apple volatiles, potentially explaining why downy hawthorn flies could have evolved to be sensitive to a blend of apple volatiles. Flight tunnel assays imply that southern hawthorn populations were not the antecedent of a preassembled apple race, as southern flies were not attracted to the apple volatile blend. Instead, behavioral evidence was found for southern host races on native hawthorns, complementing the story of the historical sympatric shift to introduced apple in the North and illustrating how R. pomonella may evolve novel combinations of agonist and antagonist responses to volatiles to use new fruit resources. PMID:22946800

  6. Using Ecological Niche Models and Niche Analyses to Understand Speciation Patterns: The Case of Sister Neotropical Orchid Bees

    PubMed Central

    Silva, Daniel P.; Vilela, Bruno; De Marco, Paulo; Nemésio, André

    2014-01-01

    The role of past connections between the two major South American forested biomes on current species distribution has been recognized a long time ago. Climatic oscillations that further separated these biomes have promoted parapatric speciation, in which many species had their continuous distribution split, giving rise to different but related species (i.e., different potential distributions and realized niche features). The distribution of many sister species of orchid bees follow this pattern. Here, using ecological niche models and niche analyses, we (1) tested the role of ecological niche differentiation on the divergence between sister orchid-bees (genera Eulaema and Eufriesea) from the Amazon and Atlantic forests, and (2) highlighted interesting areas for new surveys. Amazonian species occupied different realized niches than their Atlantic sister species. Conversely, species of sympatric but distantly related Eulaema bees occupied similar realized niches. Amazonian species had a wide potential distribution in South America, whereas Atlantic Forest species were more limited to the eastern coast of the continent. Additionally, we identified several areas in need of future surveys. Our results show that the realized niche of Atlantic-Amazonian sister species of orchid bees, which have been previously treated as allopatric populations of three species, had limited niche overlap and similarity. These findings agree with their current taxonomy, which treats each of those populations as distinct valid species. PMID:25422941

  7. Coexistence of three sympatric cormorants (Phalacrocorax spp.); partitioning of time as an ecological resource

    PubMed Central

    Mahendiran, Mylswamy

    2016-01-01

    Resource partitioning is well known along food and habitat for reducing competition among sympatric species, yet a study on temporal partitioning as a viable basis for reducing resource competition is not empirically investigated. Here, I attempt to identify the mechanism of temporal partitioning by intra- and interspecific diving analyses of three sympatric cormorant species at different freshwater wetlands around the Delhi region. Diving results indicated that cormorants opted for a shallow diving; consequently, they did not face any physiological stress. Moreover, diving durations were linked with seasons, foraging time and foraging habitats. Intraspecific comparison suggested that cormorants spent a longer time underwater in early hours of the day. Therefore, time spent for dive was higher in the forenoon than late afternoon, and the interspecific analysis also yielded a similar result. When Phalacrocorax niger and Phalacrocorax fuscicollis shared the same foraging habitat, they tended to differ in their foraging time (forenoon/afternoon). However, when P. niger and Phalacrocorax carbo shared the same foraging time, they tended to use different foraging habitats (lentic/lotic) leading to a mechanism of resource partitioning. Thus, sympatric cormorants effectively use time as a resource to exploit the food resources and successful coexistence. PMID:27293799

  8. Coexistence of three sympatric cormorants (Phalacrocorax spp.); partitioning of time as an ecological resource.

    PubMed

    Mahendiran, Mylswamy

    2016-05-01

    Resource partitioning is well known along food and habitat for reducing competition among sympatric species, yet a study on temporal partitioning as a viable basis for reducing resource competition is not empirically investigated. Here, I attempt to identify the mechanism of temporal partitioning by intra- and interspecific diving analyses of three sympatric cormorant species at different freshwater wetlands around the Delhi region. Diving results indicated that cormorants opted for a shallow diving; consequently, they did not face any physiological stress. Moreover, diving durations were linked with seasons, foraging time and foraging habitats. Intraspecific comparison suggested that cormorants spent a longer time underwater in early hours of the day. Therefore, time spent for dive was higher in the forenoon than late afternoon, and the interspecific analysis also yielded a similar result. When Phalacrocorax niger and Phalacrocorax fuscicollis shared the same foraging habitat, they tended to differ in their foraging time (forenoon/afternoon). However, when P. niger and Phalacrocorax carbo shared the same foraging time, they tended to use different foraging habitats (lentic/lotic) leading to a mechanism of resource partitioning. Thus, sympatric cormorants effectively use time as a resource to exploit the food resources and successful coexistence. PMID:27293799

  9. Genomic consequences of ecological speciation in astyanax cavefish.

    PubMed

    Borowsky, Richard; Cohen, Dana

    2013-01-01

    The cave environment is consistently radically different than the surface environment because it lacks light, and animals adapting to cave life are subject to strong selective forces much different than those experienced by their ancestors who evolved in the presence of light. As such, their divergence from surface ancestors and eventual speciation is likely to be driven by the shift in ecology. We report here that hybrids between cave and surface Astyanax mexicanus fishes produce offspring with allelic frequencies that differ significantly from Mendelian expectations both for transmission ratios and for independent assortment of unlinked markers. Comparison of allelic content of DNA from fin clips and sperm pools show that the transmission ratio distortion likely occurs during spermatogenesis. Departures from expectations of independent assortment are essentially epistatic phenomena generating linkage disequilibrium. A novel analysis of the epistatic interactions reveals an apparent network of interactions among genes known or suspected to be involved in cave adaptation, implying that the epistasis arose as a "by product" of the divergence due to cave adaptation. PMID:24260315

  10. Niche dimensionality and the genetics of ecological speciation.

    PubMed

    Chevin, Luis-Miguel; Decorzent, Guillaume; Lenormand, Thomas

    2014-05-01

    Niche dimensionality is suggested to be a key determinant of ecological speciation ("multifarious selection" hypothesis), but genetic aspects of this process have not been investigated theoretically. We use Fisher's geometrical model to study how niche dimensionality influences the mean fitness of hybrids formed upon secondary contact between populations adapting in allopatry. Gaussian selection for an optimum generates two forms of reproductive isolation (RI): an extrinsic component due to maladaptation of the mean phenotype, and an intrinsic variance load resulting from what we term transgressive incompatibilities between mutations fixed in different populations. We show that after adaptation to a new environment, RI increases with (1) the mean initial maladaptation of diverging population, and (2) niche dimensionality, which increases the phenotypic variability of fixed mutations. Under mutation selection drift equilibrium in a constant environment, RI accumulates steadily with time, at a rate that also increases with niche dimensionality. A similar pattern can be produced by successive shifts in the optimum phenotype. Niche dimensionality thus has an effect per se on postzygotic isolation, beyond putative indirect effects (stronger selection, more genes). Our mechanism is consistent with empirical evidence about transgressive segregation in crosses between divergent populations, and with patterns of accumulation of RI with time in many taxa. PMID:24410181

  11. Ecological speciation in the tropics: insights from comparative genetic studies in Amazonia.

    PubMed

    Beheregaray, Luciano B; Cooke, Georgina M; Chao, Ning L; Landguth, Erin L

    2014-01-01

    Evolution creates and sustains biodiversity via adaptive changes in ecologically relevant traits. Ecologically mediated selection contributes to genetic divergence both in the presence or absence of geographic isolation between populations, and is considered an important driver of speciation. Indeed, the genetics of ecological speciation is becoming increasingly studied across a variety of taxa and environments. In this paper we review the literature of ecological speciation in the tropics. We report on low research productivity in tropical ecosystems and discuss reasons accounting for the rarity of studies. We argue for research programs that simultaneously address biogeographical and taxonomic questions in the tropics, while effectively assessing relationships between reproductive isolation and ecological divergence. To contribute toward this goal, we propose a new framework for ecological speciation that integrates information from phylogenetics, phylogeography, population genomics, and simulations in evolutionary landscape genetics (ELG). We introduce components of the framework, describe ELG simulations (a largely unexplored approach in ecological speciation), and discuss design and experimental feasibility within the context of tropical research. We then use published genetic datasets from populations of five codistributed Amazonian fish species to assess the performance of the framework in studies of tropical speciation. We suggest that these approaches can assist in distinguishing the relative contribution of natural selection from biogeographic history in the origin of biodiversity, even in complex ecosystems such as Amazonia. We also discuss on how to assess ecological speciation using ELG simulations that include selection. These integrative frameworks have considerable potential to enhance conservation management in biodiversity rich ecosystems and to complement historical biogeographic and evolutionary studies of tropical biotas. PMID:25653668

  12. Ecological speciation in the tropics: insights from comparative genetic studies in Amazonia

    PubMed Central

    Beheregaray, Luciano B.; Cooke, Georgina M.; Chao, Ning L.; Landguth, Erin L.

    2015-01-01

    Evolution creates and sustains biodiversity via adaptive changes in ecologically relevant traits. Ecologically mediated selection contributes to genetic divergence both in the presence or absence of geographic isolation between populations, and is considered an important driver of speciation. Indeed, the genetics of ecological speciation is becoming increasingly studied across a variety of taxa and environments. In this paper we review the literature of ecological speciation in the tropics. We report on low research productivity in tropical ecosystems and discuss reasons accounting for the rarity of studies. We argue for research programs that simultaneously address biogeographical and taxonomic questions in the tropics, while effectively assessing relationships between reproductive isolation and ecological divergence. To contribute toward this goal, we propose a new framework for ecological speciation that integrates information from phylogenetics, phylogeography, population genomics, and simulations in evolutionary landscape genetics (ELG). We introduce components of the framework, describe ELG simulations (a largely unexplored approach in ecological speciation), and discuss design and experimental feasibility within the context of tropical research. We then use published genetic datasets from populations of five codistributed Amazonian fish species to assess the performance of the framework in studies of tropical speciation. We suggest that these approaches can assist in distinguishing the relative contribution of natural selection from biogeographic history in the origin of biodiversity, even in complex ecosystems such as Amazonia. We also discuss on how to assess ecological speciation using ELG simulations that include selection. These integrative frameworks have considerable potential to enhance conservation management in biodiversity rich ecosystems and to complement historical biogeographic and evolutionary studies of tropical biotas. PMID:25653668

  13. Multivariate discrimination among cryptic mites of the genus Androlaelaps (Acari: Mesostigmata: Laelapidae) parasitic of sympatric akodontine rodents (Cricetidae: Sigmodontinae) in northeastern Argentina: possible evidence of host switch followed by speciation, with the description of two new species.

    PubMed

    Lareschi, Marcela; Galliari, Carlos

    2014-12-01

    Laelapids are among the most common ectoparasites of rodents. Currently, it is under discussion whether there is a single polixenous species that parasites a variety of hosts, or whether there are cryptic species highly host specific. Herein, multivariate morphometric analyses of cryptic sympatric laelapids of the genus Androlaelaps allowed us to identify different species. These species are specific of their akodontine hosts, Akodon montensis and Thaptomys nigrita, in localities situated in northeastern Argentina. In addition, we analyzed similar laelapids associated with the akodontines Deltamys kempi and Akodon cursor. Using principle component analyses we differentiated four laelapid species, each one host specific, independent of sympatry of the hosts, and without geographical variation. From these four species, we described two new species (Androlaelaps navonae n. sp. and Androlaelaps wingei n. sp.). We determined the four species based on a range of variations in several characters, mainly size. These four laelapid species belong to the Androlaelaps rotundus species group, specific to akodontines. These species are very similar among them but differ from the remainder species of the group by their small size, distance between j6 setae similar to the distance between the z5 setae, strong ventral setae, opisthogaster with 13 pairs of strong setae (one close to the distal margin of epigynal shield), and anal shield wider than long. Further studies will elucidate whether they constitute a new laelapid genus. Phylogenetic and ecological factors influencing host-specificity are discussed, and we propose that host colonization could have taken place by host switching of a single laelapid species among rodent species, followed by speciation. PMID:25039004

  14. Ecological comparison of sympatric populations of sand lizards (Cophosaurus texanus and Callisaurus draconoides)

    SciTech Connect

    Smith, D.D.; Medica, P.A.; Sanborn, S.R.

    1987-04-30

    Sympatric populations of Cophosaurus texanus and Callisaurus draconoides were periodically sampled from March 1973 through April 1974 at Burro Creek, Mohave County, Arizona. Callisaurus were also sampled at Rock Valley, Nye County, Nevada. Sex ratios were skewed in favor of males in the adult Cophosaurus but were equal in both adult populations of Callisaurus. Both species became sexually mature as yearlings. Mean clutch sizes were 3.55 (+/- 0.83) for Cophosaurus, and 4.25 (+/- 1.08) and 5.07 (+/- 1.33) for Callisaurus at Burro Creek and Rock Valley respectively. Evidence of multiple clutches was exhibited by both species. Egg weight/body weight ratios for both species and clutch weight/body weight ratios for Cophosaurus were notably smaller than previously reported. At Burro Creek both species were highly insectivorus, with orthopterans comprising the largest food group of each. Niche overlap for food was high at the ordinal level, but at the familial level it is apparent that Callisaurus probably fed in the more xeric areas of the riparian habitat. No differences were found in the temperature responses of these two lizards. However, minor temporal separations and substantial spatial partitioning were observed. Callisaurus preferred sandy open areas, while Cophosaurus preferred the presence of some rocks and boulders. 31 references, 2 figures, 8 tables.

  15. [Pollination ecology of three sympatric species of Oenocarpus (Arecaceae) in the Colombian Amazon].

    PubMed

    Núñez A, Luis Alberto; Isaza, Carolina; Galeano, Gloria

    2015-03-01

    The understanding of pollination mechanisms is vital for developing management and conservation actions of economically important species. In order to understand the pollination mechanisms of the promising palms in the genus Oenocarpus (Arecaceae), we studied floral morphology and biology, of three sympatric species in the Colombian Amazon: O. bataua, O. balickii and O. minor. During the period 2010-2012 we made direct and continuous observations of inflorescences (visitors, pollinators, and reproductive success) of the three species in every development phase. We determined the association of the palms with their floral visitors through a complex or interaction network, whereas specificity or preference of the insects for each individual palm was assessed through paired similarity analysis, similarity analysis (ANOSIM), and ordering analysis based on nonmetric multidimensional scaling (NMSD). The three species flowered throughout the year; their inflorescences have long rachillae that hang close to each other from a short rachis, and they bear flowers in dyads or triads. Inflorescences are protandrous, thermogenic; anthesis takes place during daytime but pollination is nocturnal. We recorded 79 species of insects, mainly beetles, 33 of which visited O. balickii, 63 visited O. bataua, and 33 visited 0. minor. Although they shared some visitors, their abundance during the pistillate phase, as well as their pollen loads showed that only a few species of Curculionidae and Nitidulidae are the principal pollinators of the three studied species. Differences in network structure between staminate and pistillate phases, as well as difference in abundance found with the ANOSIM and NMSD similarity tests, suggest a high specificity of pollinators, leading to reproductive isolation among.the three species. Because all pollinating beetles were found to develop their life cycles within the inflorescences, we hypothesize the occurrence of a specialized system of mutual dependence

  16. Behavioral adaptations imply a direct link between ecological specialization and reproductive isolation in a sympatrically diverging ground beetle.

    PubMed

    Van Belleghem, Steven M; De Wolf, Katrien; Hendrickx, Frederik

    2016-08-01

    Adaptation to a previously unoccupied niche within a single population is one of the most contentious topics in evolutionary biology as it assumes the simultaneous evolution of ecologically selected and preference traits. Here, we demonstrate behavioral adaptation to contrasting hydrological regimes in a sympatric mosaic of Pogonus chalceus beetle populations, and argue that this adaptation may result in nonrandom gene flow. When exposed to experimental inundations, individuals from tidal marshes, which are naturally subjected to frequent but short floods, showed a higher propensity to remain submerged compared to individuals from seasonal marshes that are inundated for several months. This adaptive behavior is expected to decrease the probability that individuals will settle in the alternative habitat, resulting in spatial sorting and reproductive isolation of both ecotypes. Additionally, we show that this difference in behavior is induced by the environmental conditions experienced by the beetles during their nondispersive larval stages. Hence, accidental or forced ovipositioning in the alternative habitat may induce both an increased performance and preference to the natal habitat type. Such plastic traits could play an important role in the most incipient stages of divergence with gene flow. PMID:27405686

  17. Pollinator-driven ecological speciation in plants: new evidence and future perspectives

    PubMed Central

    Van der Niet, Timotheüs; Peakall, Rod; Johnson, Steven D.

    2014-01-01

    Background The hypothesis that pollinators have been important drivers of angiosperm diversity dates back to Darwin, and remains an important research topic today. Mounting evidence indicates that pollinators have the potential to drive diversification at several different stages of the evolutionary process. Microevolutionary studies have provided evidence for pollinator-mediated floral adaptation, while macroevolutionary evidence supports a general pattern of pollinator-driven diversification of angiosperms. However, the overarching issue of whether, and how, shifts in pollination system drive plant speciation represents a critical gap in knowledge. Bridging this gap is crucial to fully understand whether pollinator-driven microevolution accounts for the observed macroevolutionary patterns. Testable predictions about pollinator-driven speciation can be derived from the theory of ecological speciation, according to which adaptation (microevolution) and speciation (macroevolution) are directly linked. This theory is a particularly suitable framework for evaluating evidence for the processes underlying shifts in pollination systems and their potential consequences for the evolution of reproductive isolation and speciation. Scope This Viewpoint paper focuses on evidence for the four components of ecological speciation in the context of plant-pollinator interactions, namely (1) the role of pollinators as selective agents, (2) floral trait divergence, including the evolution of ‘pollination ecotypes‘, (3) the geographical context of selection on floral traits, and (4) the role of pollinators in the evolution of reproductive isolation. This Viewpoint also serves as the introduction to a Special Issue on Pollinator-Driven Speciation in Plants. The 13 papers in this Special Issue range from microevolutionary studies of ecotypes to macroevolutionary studies of historical ecological shifts, and span a wide range of geographical areas and plant families. These studies

  18. Effects of Local Habitat Variation on the Behavioral Ecology of Two Sympatric Groups of Brown Howler Monkey (Alouatta clamitans)

    PubMed Central

    Grelle, Carlos E. V.; Strier, Karen B.; Boubli, Jean P.

    2015-01-01

    Although the brown howler monkey (Alouatta clamitans) is a relatively well-studied Neotropical primate, its behavioral and dietary flexibility at the intra-population level remains poorly documented. This study presents data collected on the behavior and ecology of two closely located groups of brown howlers during the same period at the RPPN Feliciano Miguel Abdala in southeastern Brazil. One group occupied a primary valley habitat, henceforth the Valley Group (VG), and the other group occupied a regenerating hillside habitat, the Hill Group (HG). We hypothesized differences in the behavior and ecological parameters between these sympatric groups due to the predicted harsher conditions on the hillside, compared to the valley. We measured several habitat parameters within the home range of both groups and collected data on the activity budget, diet and day range lengths, from August to November 2005, between dawn and dusk. In total, behavioral data were collected for 26 (318 h) and 28 (308 h) sampling days for VG and HG, respectively. As we predicted, HG spent significantly more time feeding and consumed less fruit and more leaves than VG, consistent with our finding that the hillside habitat was of lower quality. However, HG also spent less time resting and more time travelling than VG, suggesting that the monkeys had to expend more time and energy to obtain high-energy foods, such as fruits and flowers that were more widely spaced in their hill habitat. Our results revealed that different locations in this forest vary in quality and raise the question of how different groups secure their home ranges. Fine-grained comparisons such as this are important to prioritize conservation and management areas within a reserve. PMID:26147203

  19. Ecological Segregation in Space, Time and Trophic Niche of Sympatric Planktivorous Petrels

    PubMed Central

    Navarro, Joan; Votier, Stephen C.; Aguzzi, Jacopo; Chiesa, Juan J.; Forero, Manuela G.; Phillips, Richard A.

    2013-01-01

    The principle of competitive exclusion postulates that ecologically-similar species are expected to partition their use of resources, leading to niche divergence. The most likely mechanisms allowing such coexistence are considered to be segregation in a horizontal, vertical or temporal dimension, or, where these overlap, a difference in trophic niche. Here, by combining information obtained from tracking devices (geolocator-immersion and time depth recorders), stable isotope analyses of blood, and conventional morphometry, we provide a detailed investigation of the ecological mechanisms that explain the coexistence of four species of abundant, zooplanktivorous seabirds in Southern Ocean ecosystems (blue petrel Halobaena caerulea, Antarctic prion Pachyptila desolata, common diving petrel Pelecanoides urinatrix and South Georgian diving petrel P. georgicus). The results revealed a combination of horizontal, vertical and temporal foraging segregation during the breeding season. The stable isotope and morphological analyses reinforced this conclusion, indicating that each species occupied a distinct trophic space, and that this appears to reflect adaptations in terms of flight performance. In conclusion, the present study indicated that although there was a degree of overlap in some measures of foraging behaviour, overall the four taxa operated in very different ecological space despite breeding in close proximity. We therefore provide important insight into the mechanisms allowing these very large populations of ecologically-similar predators to coexist. PMID:23646155

  20. Ecological segregation in space, time and trophic niche of sympatric planktivorous petrels.

    PubMed

    Navarro, Joan; Votier, Stephen C; Aguzzi, Jacopo; Chiesa, Juan J; Forero, Manuela G; Phillips, Richard A

    2013-01-01

    The principle of competitive exclusion postulates that ecologically-similar species are expected to partition their use of resources, leading to niche divergence. The most likely mechanisms allowing such coexistence are considered to be segregation in a horizontal, vertical or temporal dimension, or, where these overlap, a difference in trophic niche. Here, by combining information obtained from tracking devices (geolocator-immersion and time depth recorders), stable isotope analyses of blood, and conventional morphometry, we provide a detailed investigation of the ecological mechanisms that explain the coexistence of four species of abundant, zooplanktivorous seabirds in Southern Ocean ecosystems (blue petrel Halobaena caerulea, Antarctic prion Pachyptila desolata, common diving petrel Pelecanoides urinatrix and South Georgian diving petrel P. georgicus). The results revealed a combination of horizontal, vertical and temporal foraging segregation during the breeding season. The stable isotope and morphological analyses reinforced this conclusion, indicating that each species occupied a distinct trophic space, and that this appears to reflect adaptations in terms of flight performance. In conclusion, the present study indicated that although there was a degree of overlap in some measures of foraging behaviour, overall the four taxa operated in very different ecological space despite breeding in close proximity. We therefore provide important insight into the mechanisms allowing these very large populations of ecologically-similar predators to coexist. PMID:23646155

  1. Incipient post-zygotic barrier in a model system of ecological speciation with gene flow.

    PubMed

    Sá-Pinto, A; Martínez-Fernández, M; López-Fernández, C; Ferreira, Z; Pereira, R; Gosálvez, J; Rolán-Alvarez, E

    2013-12-01

    The role of post-zygotic isolation in nonallopatric ecological speciation is still mostly unknown and information on the nature and strength of these barriers in well-known speciation models is essential for a deeper understanding of such processes. The Galician ecotypes of the marine snail Littorina saxatilis represent one of the best studied cases of nonallopatric ecological speciation. Here, we test the existence of incipient post-zygotic isolation by comparing the fertility of male hybrids with that of both pure forms [ridged and banded (RB) and smooth and unbanded (SU) ecotypes]. We analysed the degree of sperm DNA fragmentation (SDF) of individuals morphologically classified as RB, SU and hybrids, sampled from two locations. SDF analyses were chosen to study sperm quality because, in other animal species, SDF rates correlate with important parameters for speciation research, such as fertilization and abortion rates and viability of adult progeny. In the present work, hybrids showed significantly higher SDF rates than RB and SU males in one location and significantly higher variances in both locations. These results suggest the existence of an incipient post-zygotic barrier, the strength of which may vary across the Galician shore, and highlight the potential of SDF analyses for speciation research. PMID:24164692

  2. Genomic Heterogeneity and Ecological Speciation within One Subspecies of Bacillus subtilis

    PubMed Central

    Kopac, Sarah; Wang, Zhang; Wiedenbeck, Jane; Sherry, Jessica; Wu, Martin

    2014-01-01

    Closely related bacterial genomes usually differ in gene content, suggesting that nearly every strain in nature may be ecologically unique. We have tested this hypothesis by sequencing the genomes of extremely close relatives within a recognized taxon and analyzing the genomes for evidence of ecological distinctness. We compared the genomes of four Death Valley isolates plus the laboratory strain W23, all previously classified as Bacillus subtilis subsp. spizizenii and hypothesized through multilocus analysis to be members of the same ecotype (an ecologically homogeneous population), named putative ecotype 15 (PE15). These strains showed a history of positive selection on amino acid sequences in 38 genes. Each of the strains was under a different regimen of positive selection, suggesting that each strain is ecologically unique and represents a distinct ecological speciation event. The rate of speciation appears to be much faster than can be resolved with multilocus sequencing. Each PE15 strain contained unique genes known to confer a function for bacteria. Remarkably, no unique gene conferred a metabolic system or subsystem function that was not already present in all the PE15 strains sampled. Thus, the origin of ecotypes within this clade shows no evidence of qualitative divergence in the set of resources utilized. Ecotype formation within this clade is consistent with the nanoniche model of bacterial speciation, in which ecotypes use the same set of resources but in different proportions, and genetic cohesion extends beyond a single ecotype to the set of ecotypes utilizing the same resources. PMID:24907327

  3. Divergence in Sex Steroid Hormone Signaling between Sympatric Species of Japanese Threespine Stickleback

    PubMed Central

    Kitano, Jun; Kawagishi, Yui; Mori, Seiichi; Peichel, Catherine L.; Makino, Takashi; Kawata, Masakado; Kusakabe, Makoto

    2011-01-01

    Sex steroids mediate the expression of sexually dimorphic or sex-specific traits that are important both for mate choice within species and for behavioral isolation between species. We investigated divergence in sex steroid signaling between two sympatric species of threespine stickleback (Gasterosteus aculeatus): the Japan Sea form and the Pacific Ocean form. These sympatric forms diverge in both male display traits and female mate choice behaviors, which together contribute to asymmetric behavioral isolation in sympatry. Here, we found that plasma levels of testosterone and 17β-estradiol differed between spawning females of the two sympatric forms. Transcript levels of follicle-stimulating hormone-β (FSHβ) gene were also higher in the pituitary gland of spawning Japan Sea females than in the pituitary gland of spawning Pacific Ocean females. By contrast, none of the sex steroids examined were significantly different between nesting males of the two forms. However, combining the plasma sex steroid data with testis transcriptome data suggested that the efficiency of the conversion of testosterone into 11-ketotestosterone has likely diverged between forms. Within forms, plasma testosterone levels in males were significantly correlated with male body size, a trait important for female mate choice in the two sympatric species. These results demonstrate that substantial divergence in sex steroid signaling can occur between incipient sympatric species. We suggest that investigation of the genetic and ecological mechanisms underlying divergence in hormonal signaling between incipient sympatric species will provide a better understanding of the mechanisms of speciation in animals. PMID:22216225

  4. Does early learning drive ecological divergence during speciation processes in parasitoid wasps?

    PubMed Central

    König, Kerstin; Krimmer, Elena; Brose, Sören; Gantert, Cornelia; Buschlüter, Ines; König, Christian; Klopfstein, Seraina; Wendt, Ingo; Baur, Hannes; Krogmann, Lars; Steidle, Johannes L. M.

    2015-01-01

    Central to the concept of ecological speciation is the evolution of ecotypes, i.e. groups of individuals occupying different ecological niches. However, the mechanisms behind the first step of separation, the switch of individuals into new niches, are unclear. One long-standing hypothesis, which was proposed for insects but never tested, is that early learning causes new ecological preferences, leading to a switch into a new niche within one generation. Here, we show that a host switch occurred within a parasitoid wasp, which is associated with the ability for early learning and the splitting into separate lineages during speciation. Lariophagus distinguendus consists of two genetically distinct lineages, most likely representing different species. One attacks drugstore beetle larvae (Stegobium paniceum (L.)), which were probably the ancestral host of both lineages. The drugstore beetle lineage has an innate host preference that cannot be altered by experience. In contrast, the second lineage is found on Sitophilus weevils as hosts and changes its preference by early learning. We conclude that a host switch has occurred in the ancestor of the second lineage, which must have been enabled by early learning. Because early learning is widespread in insects, it might have facilitated ecological divergence and associated speciation in this hyperdiverse group. PMID:25621331

  5. Hybridization, ecological races and the nature of species: empirical evidence for the ease of speciation.

    PubMed

    Mallet, James

    2008-09-27

    Species are generally viewed by evolutionists as 'real' distinct entities in nature, making speciation appear difficult. Charles Darwin had originally promoted a very different uniformitarian view that biological species were continuous with 'varieties' below the level of species and became distinguishable from them only when divergent natural selection led to gaps in the distribution of morphology. This Darwinian view on species came under immediate attack, and the consensus among evolutionary biologists today appears to side more with the ideas of Ernst Mayr and Theodosius Dobzhansky, who argued 70 years ago that Darwin was wrong about species. Here, I show how recent genetic studies of supposedly well-behaved animals, such as insects and vertebrates, including our own species, have supported the existence of the Darwinian continuum between varieties and species. Below the level of species, there are well-defined ecological races, while above the level of species, hybridization still occurs, and may often lead to introgression and, sometimes, hybrid speciation. This continuum is evident, not only across vast geographical regions, but also locally in sympatry. The existence of this continuum provides good evidence for gradual evolution of species from ecological races and biotypes, to hybridizing species and, ultimately, to species that no longer cross. Continuity between varieties and species not only provides an excellent argument against creationism, but also gives insight into the process of speciation. The lack of a hiatus between species and ecological races suggests that speciation may occur, perhaps frequently, in sympatry, and the abundant intermediate stages suggest that it is happening all around us. Speciation is easy! PMID:18579473

  6. Comparative spring-staging ecology of sympatric arctic-nesting geese in south-central Nebraska

    USGS Publications Warehouse

    Pearse, Aaron T.; Krapu, Gary L.; Cox, Robert R., Jr.

    2013-01-01

    The Rainwater Basin in Nebraska has been a historic staging area for midcontinent greater white-fronted geese (Anser albifrons frontalis) since the 1950s and, in the mid-1990s, millions of midcontinent lesser snow geese (Chen caerulescens caerulescens) expanded their spring migration route to include this region. In response to speculation that snow geese may be in direct competition with white-fronted geese, we compared staging ecology by quantifying diet, habitat use, movement patterns, and time budgets during springs 1998–1999. Collected white-fronted geese (n  =  190) and snow geese (n  =  203) consumed primarily corn (Zea mays; 97–98% aggregate dry mass) while staging in Nebraska; thus, diet overlap was nearly complete. Both species used cornfields most frequently during the morning (54–55%) and wetlands more during the afternoon (51–65%). When found grouped together, snow goose abundance was greater than white-fronted goose abundance by an average of 57 times (se  =  11, n  =  131 groups) in crop fields and 28 times (se  =  9, n  =  84 groups) in wetlands. Snow geese and white-fronted geese flew similar distances between roosting and feeding sites, leaving and returning to wetland roost sties at similar times in mornings and afternoons. Overlap in habitat-specific time budgets was high; resting was the most common behavior on wetlands, and foraging was a common behavior in fields. We observed 111 interspecific agonistic interactions while observing white-fronted and snow geese. White-fronted geese initiated and dominated more interactions with other waterfowl species than did snow geese (32 vs. 14%). Certain aspects of spring-staging niches (i.e., diet, habitat use, movement patterns, and habitat-specific behavior) of white-fronted and snow geese overlapped greatly at this mid-latitude staging site, creating opportunity for potential food- and habitat-based competition between species. Snow geese did not consistently dominate

  7. Functional Ecology of the Ciliate Glaucomides bromelicola, and Comparison with the Sympatric Species Bromeliothrix metopoides

    PubMed Central

    Weisse, Thomas; Scheffel, Ulrike; Stadler, Peter; Foissner, Wilhelm

    2013-01-01

    We investigated the ecology and life strategy of Glaucomides bromelicola (family Bromeliophryidae), a very common ciliate in the reservoirs (tanks) of bromeliads, assessing its response to food quality and quantity and pH. Further, we conducted competition experiments with the frequently coexisting species Bromeliothrix metopoides (family Colpodidae). In contrast to B. metopoides and many other colpodean ciliates, G. bromelicola does not form resting cysts, which jeopardizes this ciliate when its small aquatic habitats dry out. Both species form bactivorous microstomes and flagellate-feeding macrostomes. However, only G. bromelicola has a low feeding threshold and is able to adapt to different protist food. The higher affinity to the local bacterial and flagellate food renders it the superior competitor relative to B. metopoides. Continuous encystment and excystment of the latter may enable stable coexistence of both species in their natural habitat. Both are tolerant to a wide range of pH (4–9). These ciliates appear to be limited to tank bromeliads because they either lack resting cysts and vectors for long distance dispersal (G. bromelicola) and/or have highly specific food requirements (primarily B. metopoides). PMID:23865693

  8. Functional ecology of the ciliate Glaucomides bromelicola, and comparison with the sympatric species Bromeliothrix metopoides.

    PubMed

    Weisse, Thomas; Scheffel, Ulrike; Stadler, Peter; Foissner, Wilhelm

    2013-01-01

    We investigated the ecology and life strategy of Glaucomides bromelicola (family Bromeliophryidae), a very common ciliate in the reservoirs (tanks) of bromeliads, assessing its response to food quality and quantity and pH. Further, we conducted competition experiments with the frequently coexisting species Bromeliothrix metopoides (family Colpodidae). In contrast to B. metopoides and many other colpodean ciliates, G. bromelicola does not form resting cysts, which jeopardizes this ciliate when its small aquatic habitats dry out. Both species form bactivorous microstomes and flagellate-feeding macrostomes. However, only G. bromelicola has a low feeding threshold and is able to adapt to different protist food. The higher affinity to the local bacterial and flagellate food renders it the superior competitor relative to B. metopoides. Continuous encystment and excystment of the latter may enable stable coexistence of both species in their natural habitat. Both are tolerant to a wide range of pH (4-9). These ciliates appear to be limited to tank bromeliads because they either lack resting cysts and vectors for long distance dispersal (G. bromelicola) and/or have highly specific food requirements (primarily B. metopoides). PMID:23865693

  9. Incipient sympatric speciation in Midas cichlid fish from the youngest and one of the smallest crater lakes in Nicaragua due to differential use of the benthic and limnetic habitats?

    PubMed

    Kautt, Andreas F; Machado-Schiaffino, Gonzalo; Torres-Dowdall, Julian; Meyer, Axel

    2016-08-01

    Understanding how speciation can occur without geographic isolation remains a central objective in evolutionary biology. Generally, some form of disruptive selection and assortative mating are necessary for sympatric speciation to occur. Disruptive selection can arise from intraspecific competition for resources. If this competition leads to the differential use of habitats and variation in relevant traits is genetically determined, then assortative mating can be an automatic consequence (i.e., habitat isolation). In this study, we caught Midas cichlid fish from the limnetic (middle of the lake) and benthic (shore) habitats of Crater Lake Asososca Managua to test whether some of the necessary conditions for sympatric speciation due to intraspecific competition and habitat isolation are given. Lake As. Managua is very small (<900 m in diameter), extremely young (maximally 1245 years of age), and completely isolated. It is inhabited by, probably, only a single endemic species of Midas cichlids, Amphilophus tolteca. We found that fish from the limnetic habitat were more elongated than fish collected from the benthic habitat, as would be predicted from ecomorphological considerations. Stable isotope analyses confirmed that the former also exhibit a more limnetic lifestyle than the latter. Furthermore, split-brood design experiments in the laboratory suggest that phenotypic plasticity is unlikely to explain much of the observed differences in body elongation that we observed in the field. Yet, neutral markers (microsatellites) did not reveal any genetic clustering in the population. Interestingly, demographic inferences based on RAD-seq data suggest that the apparent lack of genetic differentiation at neutral markers could simply be due to a lack of time, as intraspecific competition may only have begun a few hundred generations ago. PMID:27551387

  10. Local versus Generalized Phenotypes in Two Sympatric Aurelia Species: Understanding Jellyfish Ecology Using Genetics and Morphometrics.

    PubMed

    Chiaverano, Luciano M; Bayha, Keith W; Graham, William M

    2016-01-01

    .e., different selective pressures) and evolved different strategies to cope with environmental variation. This study highlights the importance of using genetics and morphometric data to understand jellyfish ecology, evolution and systematics. PMID:27332545

  11. Local versus Generalized Phenotypes in Two Sympatric Aurelia Species: Understanding Jellyfish Ecology Using Genetics and Morphometrics

    PubMed Central

    Chiaverano, Luciano M.; Bayha, Keith W.; Graham, William M.

    2016-01-01

    .e., different selective pressures) and evolved different strategies to cope with environmental variation. This study highlights the importance of using genetics and morphometric data to understand jellyfish ecology, evolution and systematics. PMID:27332545

  12. MHC class II variation in a rare and ecological specialist mouse lemur reveals lower allelic richness and contrasting selection patterns compared to a generalist and widespread sympatric congener.

    PubMed

    Pechouskova, Eva; Dammhahn, Melanie; Brameier, Markus; Fichtel, Claudia; Kappeler, Peter M; Huchard, Elise

    2015-04-01

    The polymorphism of immunogenes of the major histocompatibility complex (MHC) is thought to influence the functional plasticity of immune responses and, consequently, the fitness of populations facing heterogeneous pathogenic pressures. Here, we evaluated MHC variation (allelic richness and divergence) and patterns of selection acting on the two highly polymorphic MHC class II loci (DRB and DQB) in the endangered primate Madame Berthe's mouse lemur (Microcebus berthae). Using 454 pyrosequencing, we examined MHC variation in a total of 100 individuals sampled over 9 years in Kirindy Forest, Western Madagascar, and compared our findings with data obtained previously for its sympatric congener, the grey mouse lemur (Microcebus murinus). These species exhibit a contrasting ecology and demography that were expected to affect MHC variation and molecular signatures of selection. We found a lower allelic richness concordant with its low population density, but a similar level of allelic divergence and signals of historical selection in the rare feeding specialist M. berthae compared to the widespread generalist M. murinus. These findings suggest that demographic factors may exert a stronger influence than pathogen-driven selection on current levels of allelic richness in M. berthae. Despite a high sequence similarity between the two congeners, contrasting selection patterns detected at DQB suggest its potential functional divergence. This study represents a first step toward unravelling factors influencing the adaptive divergence of MHC genes between closely related but ecologically differentiated sympatric lemurs and opens new questions regarding potential functional discrepancy that would explain contrasting selection patterns detected at DQB. PMID:25687337

  13. The roles of time and ecology in the continental radiation of the Old World leaf warblers (Phylloscopus and Seicercus)

    PubMed Central

    Price, Trevor D.

    2010-01-01

    Many continental sister species are allopatric or parapatric, ecologically similar and long separated, of the order of millions of years. Sympatric, ecologically differentiated, species, are often even older. This raises the question of whether build-up of sympatric diversity generally follows a slow process of divergence in allopatry, initially without much ecological change. I review patterns of speciation among birds belonging to the continental Eurasian Old World leaf warblers (Phylloscopus and Seicercus). I consider speciation to be a three-stage process (range expansions, barriers to gene flow, reproductive isolation) and ask how ecological factors at each stage have contributed to speciation, both among allopatric/parapatric sister species and among those lineages that eventually led to currently sympatric species. I suggest that time is probably the critical factor that leads to reproductive isolation between sympatric species and that a strong connection between ecological divergence and reproductive isolation remains to be established. Besides reproductive isolation, ecological factors can affect range expansions (e.g. habitat tracking) and the formation of barriers (e.g. treeless areas are effective barriers for warblers). Ecological factors may often limit speciation on continents because range expansions are difficult in ‘ecologically full’ environments. PMID:20439279

  14. Mitochondrial capture misleads about ecological speciation in the Daphnia pulex complex.

    PubMed

    Marková, Silvia; Dufresne, France; Manca, Marina; Kotlík, Petr

    2013-01-01

    The North American ecological species Daphniapulicaria and Daphniapulex are thought to have diverged from a common ancestor by adaptation to sympatric but ecologically distinct lake and pond habitats respectively. Based on mtDNA relationships, European D. pulicaria is considered a different species only distantly related to its North American counterpart, but both species share a lactate dehydrogenase (Ldh) allele F supposedly involved in lake adaptation in North America, and the same allele is also carried by the related Holarctic Daphniatenebrosa. The correct inference of the species' ancestral relationships is therefore critical for understanding the origin of their adaptive divergence. Our species tree inferred from unlinked nuclear loci for D. pulicaria and D. pulex resolved the European and North American D. pulicaria as sister clades, and we argue that the discordant mtDNA gene tree is best explained by capture of D. pulex mtDNA by D. pulicaria in North America. The Ldh gene tree shows that F-class alleles in D. pulicaria and D. tenebrosa are due to common descent (as opposed to introgression), with D. tenebrosa alleles paraphyletic with respect to D. pulicaria alleles. That D. tenebrosa still segregates the ancestral and derived amino acids at the two sites distinguishing the pond and lake alleles suggests that D. pulicaria inherited the derived states from the D. tenebrosa ancestry. Our results suggest that some adaptations restricting the gene flow between D. pulicaria and D. pulex might have evolved in response to selection in ancestral environments rather than in the species' current sympatric habitats. The Arctic (D. tenebrosa) populations are likely to provide important clues about these issues. PMID:23869244

  15. Niche divergence builds the case for ecological speciation in skinks of the Plestiodon skiltonianus species complex

    USGS Publications Warehouse

    Wogan, Guinevere O.U.; Richmond, Jonathan Q.

    2015-01-01

    Adaptation to different thermal environments has the potential to cause evolutionary changes that are sufficient to drive ecological speciation. Here, we examine whether climate-based niche divergence in lizards of the Plestiodon skiltonianus species complex is consistent with the outcomes of such a process. Previous work on this group shows that a mechanical sexual barrier has evolved between species that differ mainly in body size and that the barrier may be a by-product of selection for increased body size in lineages that have invaded xeric environments; however, baseline information on niche divergence among members of the group is lacking. We quantified the climatic niche using mechanistic physiological and correlative niche models and then estimated niche differences among species using ordination techniques and tests of niche overlap and equivalency. Our results show that the thermal niches of size-divergent, reproductively isolated morphospecies are significantly differentiated and that precipitation may have been as important as temperature in causing increased shifts in body size in xeric habitats. While these findings alone do not demonstrate thermal adaptation or identify the cause of speciation, their integration with earlier genetic and behavioral studies provides a useful test of phenotype–environment associations that further support the case for ecological speciation in these lizards.

  16. Ecological speciation in an island snail: evidence for the parallel evolution of a novel ecotype and maintenance by ecologically dependent postzygotic isolation.

    PubMed

    Stankowski, Sean

    2013-05-01

    Speciation is the process by which reproductive isolation evolves between populations. Two general models of speciation have been proposed: ecological speciation, where reproductive barriers evolve due to ecologically based divergent selection, and mutation-order speciation, where populations fix different mutations as they adapt to similar selection pressures. I evaluate these alternative models and determine the progress of speciation in a diverse group of land snails, genus Rhagada, inhabiting Rosemary Island. A recently derived keeled-flat morphotype occupies two isolated rocky hills, while globose-shelled snails inhabit the surrounding plains. The study of one hill reveals that they are separated by a narrow hybrid zone. As predicted by ecological speciation theory, there are local and landscape level associations between shell shape and habitat, and the morphological transition coincides with a narrow ecotone between the two distinct environments. Microsatellite DNA revealed a cline of hybrid index scores much wider than the morphological cline, further supporting the ecological maintenance of the morphotypes. The hybrid zone does not run through an area of low population density, as is expected for mutation-order hybrid zones, and there is a unimodal distribution of phenotypes at the centre, suggesting that there is little or no prezygotic isolation. Instead, these data suggest that the ecotypes are maintained by ecologically dependent postzygotic isolation (i.e. ecological selection against hybrids). Mitochondrial and Microsatellite DNA indicate that the keeled-flat form evolved recently, and without major historical disruptions to gene flow. The data also suggest that the two keeled-flat populations, inhabiting similar rocky hills, have evolved in parallel. These snails provide a complex example of ecological speciation in its early stages. PMID:23506623

  17. Magadi tilapia ecological specialization: filling the early gap in the speciation continuum.

    PubMed

    Pinho, Catarina; Faria, Rui

    2016-04-01

    Cichlid fish are well known for their high speciation rates, which are usually accompanied by spectacular and rapid diversification in eco-morphological and secondary sexual traits. This is best illustrated by the famous repeated explosive radiations in the African Great Lakes Tanganyika, Malawi and Victoria, each lake harbouring several hundreds of mostly endemic species. Correspondingly, cichlids diversified very rapidly in many other lakes across their range. Although the larger radiations, unparalleled in vertebrates, are certainly the most intriguing, they are also the most intricate and difficult to address because of their complex nature. This is where smaller, simpler systems may prove to be the most useful. In this issue of Molecular Ecology, Kavembe et al. (2016) report very recent genetic diversification accompanied by ecological specialization in cichlids of the small and ecologically extreme Lake Magadi, in Kenya. Combining geometric morphometrics, stable isotope analysis, population genomics using RADSeq data and coalescent-based modelling techniques, the authors characterize the eco-morphological differences between genetically distinct populations of Magadi tilapia (Alcolapia grahami), which are consistent with the different environmental conditions they experience, and infer their history of divergence. The simplicity of the focal system and the use of a multidisciplinary approach make this work particularly important for our understanding of the early stages of speciation, in both cichlids and other organisms. PMID:27012820

  18. The genomic bases of morphological divergence and reproductive isolation driven by ecological speciation in Senecio (Asteraceae).

    PubMed

    Chapman, M A; Hiscock, S J; Filatov, D A

    2016-01-01

    Ecological speciation, driven by adaptation to contrasting environments, provides an attractive opportunity to study the formation of distinct species, and the role of selection and genomic divergence in this process. Here, we focus on a particularly clear-cut case of ecological speciation to reveal the genomic bases of reproductive isolation and morphological differences between closely related Senecio species, whose recent divergence within the last ~200,000 years was likely driven by the uplift of Mt. Etna (Sicily). These species form a hybrid zone, yet remain morphologically and ecologically distinct, despite active gene exchange. Here, we report a high-density genetic map of the Senecio genome and map hybrid breakdown to one large and several small quantitative trait loci (QTL). Loci under diversifying selection cluster in three 5 cM regions which are characterized by a significant increase in relative (F(ST)), but not absolute (d(XY)), interspecific differentiation. They also correspond to some of the regions of greatest marker density, possibly corresponding to 'cold-spots' of recombination, such as centromeres or chromosomal inversions. Morphological QTL for leaf and floral traits overlap these clusters. We also detected three genomic regions with significant transmission ratio distortion (TRD), possibly indicating accumulation of intrinsic genetic incompatibilities between these recently diverged species. One of the TRD regions overlapped with a cluster of high species differentiation, and another overlaps the large QTL for hybrid breakdown, indicating that divergence of these species may have occurred due to a complex interplay of ecological divergence and accumulation of intrinsic genetic incompatibilities. PMID:26414668

  19. Is ecological speciation a major trend in aphids? Insights from a molecular phylogeny of the conifer-feeding genus Cinara

    PubMed Central

    2013-01-01

    Introduction In the past decade ecological speciation has been recognized as having an important role in the diversification of plant-feeding insects. Aphids are host-specialised phytophagous insects that mate on their host plants and, as such, they are prone to experience reproductive isolation linked with host plant association that could ultimately lead to species formation. The generality of such a scenario remains to be tested through macroevolutionary studies. To explore the prevalence of host-driven speciation in the diversification of the aphid genus Cinara and to investigate alternative modes of speciation, we reconstructed a phylogeny of this genus based on mitochondrial, nuclear and Buchnera aphidicola DNA sequence fragments and applied a DNA-based method of species delimitation. Using a recent software (PhyloType), we explored evolutionary transitions in host-plant genera, feeding sites and geographic distributions in the diversification of Cinara and investigated how transitions in these characters have accompanied speciation events. Results The diversification of Cinara has been constrained by host fidelity to conifer genera sometimes followed by sequential colonization onto different host species and by feeding-site specialisation. Nevertheless, our analyses suggest that, at the most, only half of the speciation events were accompanied by ecological niche shifts. The contribution of geographical isolation in the speciation process is clearly apparent in the occurrence of species from two continents in the same clades in relatively terminal positions in our phylogeny. Furthermore, in agreement with predictions from scenarios in which geographic isolation accounts for speciation events, geographic overlap between species increased significantly with time elapsed since their separation. Conclusions The history of Cinara offers a different perspective on the mode of speciation of aphids than that provided by classic models such as the pea aphid. In this

  20. Competition–dispersal tradeoff ecologically differentiates recently speciated marine bacterioplankton populations

    PubMed Central

    Yawata, Yutaka; Cordero, Otto X.; Menolascina, Filippo; Hehemann, Jan-Hendrik; Polz, Martin F.; Stocker, Roman

    2014-01-01

    Although competition–dispersal tradeoffs are commonly invoked to explain species coexistence for animals and plants in spatially structured environments, such mechanisms for coexistence remain unknown for microorganisms. Here we show that two recently speciated marine bacterioplankton populations pursue different behavioral strategies to exploit nutrient particles in adaptation to the landscape of ephemeral nutrient patches characteristic of ocean water. These differences are mediated primarily by differential colonization of and dispersal among particles. Whereas one population is specialized to colonize particles by attaching and growing biofilms, the other is specialized to disperse among particles by rapidly detecting and swimming toward new particles, implying that it can better exploit short-lived patches. Because the two populations are very similar in their genomic composition, metabolic abilities, chemotactic sensitivity, and swimming speed, this fine-scale behavioral adaptation may have been responsible for the onset of the ecological differentiation between them. These results demonstrate that the principles of spatial ecology, traditionally applied at macroscales, can be extended to the ocean’s microscale to understand how the rich spatiotemporal structure of the resource landscape contributes to the fine-scale ecological differentiation and species coexistence among marine bacteria. PMID:24706766

  1. A continuum of genetic divergence from sympatric host races to species in the pea aphid complex

    PubMed Central

    Peccoud, Jean; Ollivier, Anthony; Plantegenest, Manuel; Simon, Jean-Christophe

    2009-01-01

    Sympatric populations of insects adapted to different host plants, i.e., host races, are good models to investigate how natural selection can promote speciation in the face of ongoing gene flow. However, host races are documented in very few model systems and their gradual evolution into good species, as assumed under a Darwinian view of species formation, lacks strong empirical support. We aim at resolving this uncertainty by investigating host specialization and gene flow among populations of the pea aphid complex, Acyrthosiphon pisum. Genetic markers and tests of host plant specificity indicate the existence of at least 11 well-distinguished sympatric populations associated with different host plants in Western Europe. Population assignment tests show variable migration and hybridization rates among sympatric populations, delineating 8 host races and 3 possible species. Notably, hybridization correlates negatively with genetic differentiation, forming a continuum of population divergence toward virtually complete speciation. The pea aphid complex thus illustrates how ecological divergence can be sustained among many hybridizing populations and how insect host races blend into species by gradual reduction of gene flow. PMID:19380742

  2. [Characteristics of speciation and evaluation of ecological risk of heavy metals in sewage sludge of Guangzhou].

    PubMed

    Guo, Peng-Ran; Lei, Yong-Qian; Cai, Da-Chuan; Zhang, Tao; Wu, Rui; Pan, Jia-Chuan

    2014-02-01

    Contents of heavy metals in different sewage sludges were analyzed and the speciation distribution and bioavailability of heavy metals were investigated, and the risk assessment code (RAC) and toxicity characteristic leaching procedure for solid waste were used to evaluate the potential ecological risk and leaching toxicity risk of heavy metals in sludge samples, respectively. The results showed that contents of Cu, Cr, Pb and Zn were high and presented a great difference by different sources in sewage sludges. Most of heavy metals existed in non-residual fractions and percentages of the mobile fraction (acid soluble fraction) of heavy metals in acidic sludge were higher. According to the results of single extraction, 1 mol x L(-1) NaOAc solution (pH 5.0) and 0.02 mol x L(-1) EDTA + 0.5 mol x L(-1) NH4OAc solution (pH 4.6) were suitable for evaluating bioavailable heavy metals in acidic and alkaline sludge, respectively. Percentages of bioavailable heavy metals were higher with the stronger of sludge acidity. The mobile ability of heavy metals resulted in the high ecological risk of sludge samples, and the bioavailability of heavy metals caused acidic sludges with a very high ecological risk but alkaline sludges with the middle ecological risk. Leaching toxicity risk was very high in sludge samples except domestic sewage sludge. After the removal of bioavailable heavy metals, leaching toxicity risk of sludge samples was still high in spite of its decrease; however, part type of sludges could be implemented landfill disposal. PMID:24812965

  3. Ongoing ecological speciation in Cotesia sesamiae, a biological control agent of cereal stem borers

    PubMed Central

    Kaiser, Laure; Le Ru, Bruno Pierre; Kaoula, Ferial; Paillusson, Corentin; Capdevielle-Dulac, Claire; Obonyo, Julius Ochieng; Herniou, Elisabeth A; Jancek, Severine; Branca, Antoine; Calatayud, Paul-André; Silvain, Jean-François; Dupas, Stephane

    2015-01-01

    To develop efficient and safe biological control, we need to reliably identify natural enemy species, determine their host range, and understand the mechanisms that drive host range evolution. We investigated these points in Cotesia sesamiae, an African parasitic wasp of cereal stem borers. Phylogenetic analyses of 74 individual wasps, based on six mitochondrial and nuclear genes, revealed three lineages. We then investigated the ecological status (host plant and host insect ranges in the field, and host insect suitability tests) and the biological status (cross-mating tests) of the three lineages. We found that one highly supported lineage showed all the hallmarks of a cryptic species. It is associated with one host insect, Sesamia nonagrioides, and is reproductively isolated from the other two lineages by pre- and postmating barriers. The other two lineages had a more variable phylogenetic support, depending on the set of genes; they exhibited an overlapping and diversified range of host species and are not reproductively isolated from one another. We discuss the ecological conditions and mechanisms that likely generated this ongoing speciation and the relevance of this new specialist taxon in the genus Cotesia for biological control. PMID:26366198

  4. Phenotypic and genetic evidence for ecological speciation of Aquilegia japonica and A. oxysepala.

    PubMed

    Li, Lin-Feng; Wang, Hua-Ying; Pang, Di; Liu, Ying; Liu, Bao; Xiao, Hong-Xing

    2014-12-01

    Natural selection is thought to be a driving force that can cause the evolution of reproductive isolation. The genus Aquilegia is a model system to address how natural selection promotes the process of speciation. Morphological differences between A. oxysepala, A. japonica and their hybrids were quantified for two vegetative (plant height and leaf area) and three floral morphological (sepal area, corolla length and diameter) traits. We also evaluated the genetic variability of the two species and their hybrids based on two chloroplast (1225 bp), four nuclear (5811 bp) genes and 15 microsatellites. Our results revealed that differentiation of A. japonica and A. oxysepala at the ecological and morphological levels also involved divergence at the genetic level. In addition, the analysis of nucleotide variation patterns showed that the two species possessed numerous fixation sites at nuclear genes gAA4, gA7 and gAA12. Furthermore, we found that all of the phenotypic hybrids also showed a genetically admixed ancestry. These findings suggest that natural selection has indeed facilitated the formation of distinct genetic variation patterns in the two Aquilegia species and habitat adaptation has been driving the ecologically based evolution of reproductive isolation. PMID:25117915

  5. Ecological Speciation in Nolina parviflora (Asparagaceae): Lacking Spatial Connectivity along of the Trans-Mexican Volcanic Belt

    PubMed Central

    Ruiz-Sanchez, Eduardo; Specht, Chelsea D.

    2014-01-01

    The hypothesis of ecological speciation states that as populations diverge in different niches, reproductive isolation evolves as a by-product of adaptation to these different environments. In this context, we used Nolina parviflora as a model to test if this species evolved via ecological speciation and to explore current and historical gene flow among its populations. Nolina parviflora is a montane species endemic to Mexico with its geographical distribution restricted largely to the Trans-Mexican Volcanic Belt. This mountain range is one of the most complex geological regions in Mexico, having undergone volcanism from the mid-Miocene to the present. Ecologically, the Trans-Mexican Volcanic Belt possesses different types of vegetation, including tropical dry forest; oak, pine, pine-oak, and pine-juniper forests; and xerophytic scrub - all of which maintain populations of N. parviflora. Using species distribution models, climatic analyses, spatial connectivity and morphological comparisons, we found significant differences in climatic and morphological variables between populations of N. parviflora in two distinct Trans-Mexican Volcanic Belt regions (east vs. west). This could mean that the geographically isolated populations diverged from one another via niche divergence, indicating ecological speciation. Spatial connectivity analysis revealed no connectivity between these regions under the present or last glacial maximum climate models, indicating a lack of gene flow between the populations of the two regions. The results imply that these populations may encompass more than a single species. PMID:24905911

  6. Recent Speciation in Three Closely Related Sympatric Specialists: Inferences Using Multi-Locus Sequence, Post-Mating Isolation and Endosymbiont Data

    PubMed Central

    Xue, Huai-Jun; Li, Wen-Zhu; Nie, Rui-E; Yang, Xing-Ke

    2011-01-01

    Shifting between unrelated host plants is relatively rare for phytophagous insects, and distinct host specificity may play crucial roles in reproductive isolation. However, the isolation status and the relationship between parental divergence and post-mating isolation among closely related sympatric specialists are still poorly understood. Here, multi-locus sequence were used to estimate the relationship among three host plant–specific closely related flea beetles, Altica cirsicola, A. fragariae and A. viridicyanea (abbreviated as AC, AF and AV respectively). The tree topologies were inconsistent using different gene or different combinations of gene fragments. The relationship of AF+(AC+AV) was supported, however, by both gene tree and species tree based on concatenated data. Post-mating reproductive data on the results of crossing these three species are best interpreted in the light of a well established phylogeny. Nuclear-induced but not Wolbachia-induced unidirectional cytoplasmic incompatibility, which was detected in AC-AF and AF-AV but not in AC-AV, may also suggest more close genetic affinity between AC and AV. Prevalence of Wolbachia in these three beetles, and the endosymbiont in most individuals of AV and AC sharing a same wsp haplotype may give another evidence of AF+(AC+AV). Our study also suggested that these three flea beetles diverged in a relative short time (0.94 My), which may be the result of shifting between unrelated host plants and distinct host specificity. Incomplete post-mating isolation while almost complete lineage sorting indicated that effective pre-mating isolation among these three species should have evolved. PMID:22110767

  7. Non-breeding habitat preference affects ecological speciation in migratory waders

    PubMed Central

    2007-01-01

    Models of ecological speciation predict that certain types of habitat should be more conducive to species diversification than others. In this study, I test this hypothesis in waders of the sub-order Charadrii using the number of morphological sub-species per species as an index of diversity. I classified all members of this clade as spending the non-breeding season either coastally or inland and argue that these represent fundamentally different environments. Coastal mudflats are characterised by high predictability and patchy worldwide distribution, whilst inland wetlands are widespread but unpredictable. The results show that migratory species that winter coastally are sub-divided into more sub-species than those that winter inland. This was not the case for non-migratory species. I argue that coastal environments select for more rigid migratory pathways, whilst inland wetlands favour more flexible movement patterns. Population sub-division could then result from the passive segregation of breeding sites or from the active selection for assortative mating of ecomorphs. PMID:18087687

  8. Ecology and conservation of the crowned lemur, Lemur coronatus, at Ankarana, n. Madagascar. With notes on Sanford's lemur, other sympatrics and subfossil lemurs.

    PubMed

    Wilson, J M; Stewart, P D; Ramangason, G S; Denning, A M; Hutchings, M S

    1989-01-01

    Forests of Ankarana limestone massif in northern Madagascar support one of the largest and least disturbed populations of Crowned Lemurs, Lemur coronatus. This paper reports a preliminary study of the ecology of this species in the Ankarana Special Reserve conducted at the end of the dry season in 1986, with additional information collected a year later. Crowned Lemurs occur in very high densities in the semi-deciduous canopy forest and this probably represents a dry season refuge for the species. They also use more open habitats, including sparsely vegetated limestone and degraded forest. Sanford's Lemur, Lemur fulvus sanfordi, also inhabits the Ankarana forests but is most abundant in degraded habitats. Crowned and Sanford's Lemurs had similar patterns of activity, which included nocturnal travelling and feeding bouts. Crowned Lemurs proved to be unusual among Lemur species in displaying low spatial troop cohesion and a lack of obvious troop hierarchy. Stronglyoides-like enteric helminths infested about one third of Crowned Lemurs but were apparently not causing disease. Crowned Lemurs fall prey to the Fosa, Cryptoprocta ferox, and the young possibly also to the largest raptors. A total of seven living lemur species (including the very rare Propithecus diadema perrieri and Daubentonia madagascariensis) were confirmed at Ankarana by the authors, and three further species have been reported by other observers. In addition to these ten extant lemurs, four subfossil species have been discovered: three of them (Hapalemur simus, Palaeopropithecus and Mesopropithecus) by the authors. The possibility that all 14 lemurs were once sympatric is discussed. For the present, the lemurs of Ankarana are protected from hunting by local taboo. Nevertheless they are under severe threat from habitat destruction, despite Ankarana's Special Reserve status. Given the very restricted distributions of Crowned and Sanford's Lemurs, both must be considered as threatened with extinction

  9. Colour pattern as a single trait driving speciation in Hypoplectrus coral reef fishes?

    PubMed Central

    Puebla, Oscar; Bermingham, Eldredge; Guichard, Frédéric; Whiteman, Elizabeth

    2007-01-01

    Theory shows that speciation in the presence of gene flow occurs only under narrow conditions. One of the most favourable scenarios for speciation with gene flow is established when a single trait is both under disruptive natural selection and used to cue assortative mating. Here, we demonstrate the potential for a single trait, colour pattern, to drive incipient speciation in the genus Hypoplectrus (Serranidae), coral reef fishes known for their striking colour polymorphism. We provide data demonstrating that sympatric Hypoplectrus colour morphs mate assortatively and are genetically distinct. Furthermore, we identify ecological conditions conducive to disruptive selection on colour pattern by presenting behavioural evidence of aggressive mimicry, whereby predatory Hypoplectrus colour morphs mimic the colour patterns of non-predatory reef fish species to increase their success approaching and attacking prey. We propose that colour-based assortative mating, combined with disruptive selection on colour pattern, is driving speciation in Hypoplectrus coral reef fishes. PMID:17360287

  10. On the ecology of two sympatric flounders of the genus Paralichthys in the Bay of Coquimbo, Chile

    NASA Astrophysics Data System (ADS)

    Acuña, Enzo; Cid, Luis

    The ecology of two flounders belonging to the genus Paralichthys was studied in the Bay of Coquimbo (29°57'S), Chile. P. adspersus grows larger than P. microps. In both species, the females were significantly larger than the males. The species differed in their reproductive cycles as revealed by their gonadosomatic indices. This difference was also reflected in larval abundance and spatial distribution of the species. No significant changes were found in the abundances of juveniles and adults in the Bay of Coquimbo either throughout the year or interannually. However, when the analysis included the proportion of specimens between the two species and sex by season, the differences were apparent in most cases. The results show that the environmental characteristics of the marine system which the Bay of Coquimbo is a part of provide good feeding, spawning and nursery grounds for these two species of flounder.

  11. Experimental evidence of genome-wide impact of ecological selection during early stages of speciation-with-gene-flow.

    PubMed

    Egan, Scott P; Ragland, Gregory J; Assour, Lauren; Powell, Thomas H Q; Hood, Glen R; Emrich, Scott; Nosil, Patrik; Feder, Jeffrey L

    2015-08-01

    Theory predicts that speciation-with-gene-flow is more likely when the consequences of selection for population divergence transitions from mainly direct effects of selection acting on individual genes to a collective property of all selected genes in the genome. Thus, understanding the direct impacts of ecologically based selection, as well as the indirect effects due to correlations among loci, is critical to understanding speciation. Here, we measure the genome-wide impacts of host-associated selection between hawthorn and apple host races of Rhagoletis pomonella (Diptera: Tephritidae), a model for contemporary speciation-with-gene-flow. Allele frequency shifts of 32 455 SNPs induced in a selection experiment based on host phenology were genome wide and highly concordant with genetic divergence between co-occurring apple and hawthorn flies in nature. This striking genome-wide similarity between experimental and natural populations of R. pomonella underscores the importance of ecological selection at early stages of divergence and calls for further integration of studies of eco-evolutionary dynamics and genome divergence. PMID:26077935

  12. Erosive processes after tectonic uplift stimulate vicariant and adaptive speciation: evolution in an Afrotemperate-endemic paper daisy genus

    PubMed Central

    2014-01-01

    Background The role of tectonic uplift in stimulating speciation in South Africa’s only alpine zone, the Drakensberg, has not been explicitly examined. Tectonic processes may influence speciation both through the creation of novel habitats and by physically isolating plant populations. We use the Afrotemperate endemic daisy genus Macowania to explore the timing and mode (geographic versus adaptive) of speciation in this region. Between sister species pairs we expect high morphological divergence where speciation has happened in sympatry (adaptive) while with geographic (vicariant) speciation we may expect to find less morphological divergence and a greater degree of allopatry. A dated molecular phylogenetic hypothesis for Macowania elucidates species’ relationships and is used to address the potential impact of uplift on diversification. Morphological divergence of a small sample of reproductive and vegetative characters, used as a proxy for adaptive divergence, is measured against species’ range distributions to estimate mode of speciation across two subclades in the genus. Results The Macowania crown age is consistent with the hypothesis of post-uplift diversification, and we find evidence for both vicariant and adaptive speciation between the two subclades within Macowania. Both subclades exhibit strong signals of range allopatry, suggesting that geographic isolation was important in speciation. One subclade, associated with dry, rocky environments at high altitudes, shows very little morphological and ecological differentiation but high range allopatry. The other subclade occupies a greater variety of habitats and exhibits far greater morphological differentiation, but contains species with overlapping distribution ranges. Conclusions Species in Macowania are likely to have diversified in response to tectonic uplift, and we invoke uplift and uplift-mediated erosion as the main drivers of speciation. The greater relative morphological divergence in

  13. Selenium Distribution and Speciation in the Hyperaccumulator Astragalus bisulcatus and Associated Ecological Partners1[W][OA

    PubMed Central

    Valdez Barillas, José R.; Quinn, Colin F.; Freeman, John L.; Lindblom, Stormy D.; Fakra, Sirine C.; Marcus, Matthew A.; Gilligan, Todd M.; Alford, Élan R.; Wangeline, Ami L.; Pilon-Smits, Elizabeth A.H.

    2012-01-01

    The goal of this study was to investigate how plant selenium (Se) hyperaccumulation may affect ecological interactions and whether associated partners may affect Se hyperaccumulation. The Se hyperaccumulator Astragalus bisulcatus was collected in its natural seleniferous habitat, and x-ray fluorescence mapping and x-ray absorption near-edge structure spectroscopy were used to characterize Se distribution and speciation in all organs as well as in encountered microbial symbionts and herbivores. Se was present at high levels (704–4,661 mg kg−1 dry weight) in all organs, mainly as organic C-Se-C compounds (i.e. Se bonded to two carbon atoms, e.g. methylselenocysteine). In nodule, root, and stem, up to 34% of Se was found as elemental Se, which was potentially due to microbial activity. In addition to a nitrogen-fixing symbiont, the plants harbored an endophytic fungus that produced elemental Se. Furthermore, two Se-resistant herbivorous moths were discovered on A. bisulcatus, one of which was parasitized by a wasp. Adult moths, larvae, and wasps all accumulated predominantly C-Se-C compounds. In conclusion, hyperaccumulators live in association with a variety of Se-resistant ecological partners. Among these partners, microbial endosymbionts may affect Se speciation in hyperaccumulators. Hyperaccumulators have been shown earlier to negatively affect Se-sensitive ecological partners while apparently offering a niche for Se-resistant partners. Through their positive and negative effects on different ecological partners, hyperaccumulators may influence species composition and Se cycling in seleniferous ecosystems. PMID:22645068

  14. Weak crossability barrier but strong juvenile selection supports ecological speciation of the hybrid pine Pinus densata on the Tibetan plateau.

    PubMed

    Zhao, Wei; Meng, Jingxiang; Wang, Baosheng; Zhang, Lisha; Xu, Yulan; Zeng, Qing-Yin; Li, Yue; Mao, Jian-Feng; Wang, Xiao-Ru

    2014-11-01

    Determining how a new hybrid lineage can achieve reproductive isolation is a key to understanding the process and mechanisms of homoploid hybrid speciation. Here, we evaluated the degree and nature of reproductive isolation between the ecologically successful hybrid species Pinus densata and its parental species P. tabuliformis and P. yunnanensis. We performed interspecific crosses among the three species to assess their crossability. We then conducted reciprocal transplantation experiments to evaluate their fitness differentiation, and to examine how natural populations representing different directions of introgression differ in adaptation. The crossing experiments revealed weak genetic barriers among the species. The transplantation trials showed manifest evidence of local adaptation as the three species all performed best in their native habitats. Pinus densata populations from the western edge of its distribution have evolved a strong local adaptation to the specific habitat in that range; populations representing different directions of introgressants with the two parental species all showed fitness disadvantages in this P. densata habitat. These observations illustrate that premating isolation through selection against immigrants from other habitat types or postzygotic isolation through selection against backcrosses between the three species is strong. Thus, ecological selection in combination with endogenous components and geographic isolation has likely played a significant role in the speciation of P. densata. PMID:25065387

  15. Arabidopsis hybrid speciation processes

    PubMed Central

    Schmickl, Roswitha; Koch, Marcus A.

    2011-01-01

    The genus Arabidopsis provides a unique opportunity to study fundamental biological questions in plant sciences using the diploid model species Arabidopsis thaliana and Arabidopsis lyrata. However, only a few studies have focused on introgression and hybrid speciation in Arabidopsis, although polyploidy is a common phenomenon within this genus. More recently, there is growing evidence of significant gene flow between the various Arabidopsis species. So far, we know Arabidopsis suecica and Arabidopsis kamchatica as fully stabilized allopolyploid species. Both species evolved during Pleistocene glaciation and deglaciation cycles in Fennoscandinavia and the amphi-Beringian region, respectively. These hybrid studies were conducted either on a phylogeographic scale or reconstructed experimentally in the laboratory. In our study we focus at a regional and population level. Our research area is located in the foothills of the eastern Austrian Alps, where two Arabidopsis species, Arabidopsis arenosa and A. lyrata ssp. petraea, are sympatrically distributed. Our hypothesis of genetic introgression, migration, and adaptation to the changing environment during the Pleistocene has been confirmed: We observed significant, mainly unidirectional gene flow between the two species, which has given rise to the tetraploid A. lyrata. This cytotype was able to escape from the narrow ecological niche occupied by diploid A. lyrata ssp. petraea on limestone outcrops by migrating northward into siliceous areas, leaving behind a trail of genetic differentiation. PMID:21825128

  16. Evidence of sympatric speciation of elderberry carlaviruses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Five new carlavirus species infecting elderberry were characterized and tentatively named as elderberry virus A-E (EVA-EVE). The genome organization of the viruses ranges between 8,540-8,628 nucleotides, excluding the polyadenylated tail. EVA, EVB and EVD share a common ancestor as do EVC and EVE, i...

  17. Riverscape genetics identifies replicated ecological divergence across an Amazonian ecotone.

    PubMed

    Cooke, Georgina M; Landguth, Erin L; Beheregaray, Luciano B

    2014-07-01

    Ecological speciation involves the evolution of reproductive isolation and niche divergence in the absence of a physical barrier to gene flow. The process is one of the most controversial topics of the speciation debate, particularly in tropical regions. Here, we investigate ecologically based divergence across an Amazonian ecotone in the electric fish, Steatogenys elegans. We combine phylogenetics, genome scans, and population genetics with a recently developed individual-based evolutionary landscape genetics approach that incorporates selection. This framework is used to assess the relative contributions of geography and divergent natural selection between environments as biodiversity drivers. We report on two closely related and sympatric lineages that exemplify how divergent selection across a major Amazonian aquatic ecotone (i.e., between rivers with markedly different hydrochemical properties) may result in replicated ecologically mediated speciation. The results link selection across an ecological gradient with reproductive isolation and we propose that assortative mating based on water color may be driving the divergence. Divergence resulting from ecologically driven selection highlights the importance of considering environmental heterogeneity in studies of speciation in tropical regions. Furthermore, we show that framing ecological speciation in a spatially explicit evolutionary landscape genetics framework provides an important first step in exploring a wide range of the potential effects of spatial dependence in natural selection. PMID:24641091

  18. Host shift and speciation in a coral-feeding nudibranch.

    PubMed

    Faucci, Anuschka; Toonen, Robert J; Hadfield, Michael G

    2007-01-01

    While the role of host preference in ecological speciation has been investigated extensively in terrestrial systems, very little is known in marine environments. Host preference combined with mate choice on the preferred host can lead to population subdivision and adaptation leading to host shifts. We use a phylogenetic approach based on two mitochondrial genetic markers to disentangle the taxonomic status and to investigate the role of host specificity in the speciation of the nudibranch genus Phestilla (Gastropoda, Opisthobranchia) from Guam, Palau and Hawaii. Species of the genus Phestilla complete their life cycle almost entirely on their specific host coral (species of Porites, Goniopora and Tubastrea). They reproduce on their host coral and their planktonic larvae require a host-specific chemical cue to metamorphose and settle onto their host. The phylogenetic trees of the combined cytochrome oxidase I and ribosomal 16S gene sequences clarify the relationship among species of Phestilla identifying most of the nominal species as monophyletic clades. We found a possible case of host shift from Porites to Goniopora and Tubastrea in sympatric Phestilla spp. This represents one of the first documented cases of host shift as a mechanism underlying speciation in a marine invertebrate. Furthermore, we found highly divergent clades within Phestilla sp. 1 and Phestilla minor (8.1-11.1%), suggesting cryptic speciation. The presence of a strong phylogenetic signal for the coral host confirms that the tight link between species of Phestilla and their host coral probably played an important role in speciation within this genus. PMID:17134995

  19. Habitat selection and ecological speciation in Galápagos warbler finches (Certhidea olivacea and Certhidea fusca).

    PubMed

    Tonnis, Brandon; Grant, Peter R; Grant, B Rosemary; Petren, Kenneth

    2005-04-22

    We investigated phylogeographic divergence among populations of Galápagos warble finches. Their broad distribution, lack of phenotypic differentiation and low levels of genetic divergence make warbler finches an appropriate model to study speciation in allopatry. A positive relationship between genetic and geographical distance is expected for island taxa. Warbler finches actually showed a negative isolation by distance relationship, causing us to reject the hypothesis of distance-limited dispersal. An alternative hypothesis, that dispersal is limited by habitat similarity, was supported. We found a positive correlation between genetic distances and differences in maximum elevation among islands, which is an indicator of ecological similarity. MtDNA sequence variation revealed monophyletic support for two distinct species. Certhidea olivacea have recently dispersed among larger central islands, while some Certhidea fusca have recently dispersed to small islands at opposite ends of the archipelago. We conclude that females have chosen to breed on islands with habitats similar to their natal environment. Habitat selection is implicated as an important component of speciation of warbler finches, which is the earliest known divergence of the adaptive radiation of Darwin's finches. These results suggest that small populations can harbour cryptic but biologically meaningful variation that may affect longer term evolutionary processes. PMID:15940826

  20. Radiating on Oceanic Islands: Patterns and Processes of Speciation in the Land Snail Genus Theba (Risso 1826)

    PubMed Central

    Greve, Carola; Gimnich, France; Hutterer, Rainer; Misof, Bernhard; Haase, Martin

    2012-01-01

    Island radiations have played a major role in shaping our current understanding of allopatric, sympatric and parapatric speciation. However, the fact that species divergence correlates with island size emphasizes the importance of geographic isolation (allopatry) in speciation. Based on molecular and morphological data, we investigated the diversification of the land snail genus Theba on the two Canary Islands of Lanzarote and Fuerteventura. Due to the geological history of both islands, this study system provides ideal conditions to investigate the interplay of biogeography, dispersal ability and differentiation in generating species diversity. Our analyses demonstrated extensive cryptic diversification of Theba on these islands, probably driven mainly by non-adaptive allopatric differentiation and secondary gene flow. In a few cases, we observed a complete absence of gene flow among sympatrically distributed forms suggesting an advanced stage of speciation. On the Jandía peninsula genome scans suggested genotype-environment associations and potentially adaptive diversification of two closely related Theba species to different ecological environments. We found support for the idea that genetic differentiation was enhanced by divergent selection in different environments. The diversification of Theba on both islands is therefore best explained by a mixture of non-adaptive and adaptive speciation, promoted by ecological and geomorphological factors. PMID:22493687

  1. Edaphic and light conditions of sympatric plant morphotypes in western Amazonia

    PubMed Central

    2014-01-01

    Abstract Here I present a dataset of edaphic and light conditions associated with the occurrence of sympatric morphotypes of Geonoma macrostachys (Arecaceae/Palmae), a candidate case study from Amazonia hypothesized to have evolved under ecological speciation. Transects were established in three lowland rainforests in Peru, and the abundance of each local morphotype of this species was recorded in a total area of 4.95 hectares. Composite soil samples and hemispherical photographs were taken along the transects were the species occurred to obtain information on soil nutrients, soil texture, and indirect measurements of light availability. The raw and summary tables disclose the characteristics of each study site and habitats within them, which could be useful to soil scientists, ecologists, and conservationists engaged in similar research activities or meta-analyses in Amazonia. PMID:24891831

  2. Molecular phylogeny of grunts (Teleostei, Haemulidae), with an emphasis on the ecology, evolution, and speciation history of New World species

    PubMed Central

    2012-01-01

    Background The fish family Haemulidae is divided in two subfamilies, Haemulinae and Plectorhynchinae (sweetlips), including approximately 17 genera and 145 species. The family has a broad geographic distribution that encompasses contrasting ecological habitats resulting in a unique potential for evolutionary hypotheses testing. In the present work we have examined the phylogenetic relationships of the family using selected representatives of additional Percomorpha based on Bayesian and Maximum likelihood methods by means of three mitochondrial genes. We also developed a phylogenetic hypothesis of the New World species based on five molecular markers (three mitochondrial and two nuclear) as a framework to evaluate the evolutionary history, the ecological diversification and speciation patterns of this group. Results Mitochondrial genes and different reconstruction methods consistently recovered a monophyletic Haemulidae with the Sillaginidae as its sister clade (although with low support values). Previous studies proposed different relationships that were not recovered in this analysis. We also present a robust molecular phylogeny of Haemulinae based on the combined data of two nuclear and three mitochondrial genes. All topologies support the monophyly of both sub-families (Haemulinae, Plectorhinchinae). The genus Pomadasys was shown to be polyphyletic and Haemulon, Anisotremus, and Plectorhinchus were found to be paraphyletic. Four of seven presumed geminate pairs were indeed found to be sister species, however our data did not support a contemporaneous divergence. Analyses also revealed that differential use of habitat might have played an important role in the speciation dynamics of this group of fishes, in particular among New World species where extensive sample coverage was available. Conclusions This study provides a new hypothesis for the sister clade of Hamulidae and a robust phylogeny of the latter. The presence of para- and polyphyletic genera underscores

  3. Recent advances in ecological genomics: from phenotypic plasticity to convergent and adaptive evolution and speciation.

    PubMed

    Landry, Christian R; Aubin-Horth, Nadia

    2014-01-01

    Biological diversity emerges from the interaction between genomes and their environment. Recent conceptual and technological developments allow dissecting these interactions over short and long time-scales. The 16 contributions to this book by leaders in the field cover major recent progresses in the field of Ecological Genomics. Altogether, they illustrate the interplay between the life-history and genomic architecture of organisms, how the interaction of the environment and the genome is shaping phenotypic variation through phenotypic plasticity, how the process of adaptation may be constrained and fueled by internal and external features of organisms and finally, how species formation is the result of intricate interactions between genomes and the ecological conditions. These contributions also show how fundamental questions in biology transcend the boundaries of kingdoms, species and environments and illustrate how integrative approaches are powerful means to answer the most important and challenging questions in ecology and evolution. PMID:24277292

  4. Speciation dynamics and biogeography of Neotropical spiral gingers (Costaceae).

    PubMed

    André, Thiago; Salzman, Shayla; Wendt, Tânia; Specht, Chelsea D

    2016-10-01

    Species can arise via the divisive effects of allopatry as well as due to ecological and/or reproductive character displacement within sympatric populations. Two separate lineages of Costaceae are native to the Neotropics; an early-diverging clade endemic to South America (consisting of ca. 16 species in the genera Monocostus, Dimerocostus and Chamaecostus); and the Neotropical Costus clade (ca. 50 species), a diverse assemblage of understory herbs comprising nearly half of total familial species richness. We use a robust dated molecular phylogeny containing most of currently known species to inform macroevolutionary reconstructions, enabling us to examine the context of speciation in Neotropical lineages. Analyses of speciation rate revealed a significant variation among clades, with a rate shift at the most recent common ancestor of the Neotropical Costus clade. There is an overall predominance of allopatric speciation in the South American clade, as most species display little range overlap. In contrast, sympatry is much higher within the Neotropical Costus clade, independent of node age. Our results show that speciation dynamics during the history of Costaceae is strongly heterogeneous, and we suggest that the Costus radiation in the Neotropics arose at varied geographic contexts. PMID:27400627

  5. Temporal, spatial and ecological dynamics of speciation among amphi-Beringian small mammals

    USGS Publications Warehouse

    Hope, Andrew G.; Takebayashi, Naoki; Galbreath, Kurt E.; Talbot, Sandra L.; Cook, Joseph A.

    2013-01-01

    Quaternary climate cycles played an important role in promoting diversification across the Northern Hemisphere, although details of the mechanisms driving evolutionary change are still poorly resolved. In a comparative phylogeographical framework, we investigate temporal, spatial and ecological components of evolution within a suite of Holarctic small mammals. We test a hypothesis of simultaneous divergence among multiple taxon pairs, investigating time to coalescence and demographic change for each taxon in response to a combination of climate and geography.

  6. Widespread horizontal genomic exchange does not erode species barriers among sympatric ducks

    PubMed Central

    2012-01-01

    Background The study of speciation and maintenance of species barriers is at the core of evolutionary biology. During speciation the genome of one population becomes separated from other populations of the same species, which may lead to genomic incompatibility with time. This separation is complete when no fertile offspring is produced from inter-population matings, which is the basis of the biological species concept. Birds, in particular ducks, are recognised as a challenging and illustrative group of higher vertebrates for speciation studies. There are many sympatric and ecologically similar duck species, among which fertile hybrids occur relatively frequently in nature, yet these species remain distinct. Results We show that the degree of shared single nucleotide polymorphisms (SNPs) between five species of dabbling ducks (genus Anas) is an order of magnitude higher than that previously reported between any pair of eukaryotic species with comparable evolutionary distances. We demonstrate that hybridisation has led to sustained exchange of genetic material between duck species on an evolutionary time scale without disintegrating species boundaries. Even though behavioural, genetic and ecological factors uphold species boundaries in ducks, we detect opposing forces allowing for viable interspecific hybrids, with long-term evolutionary implications. Based on the superspecies concept we here introduce the novel term "supra-population" to explain the persistence of SNPs identical by descent within the studied ducks despite their history as distinct species dating back millions of years. Conclusions By reviewing evidence from speciation theory, palaeogeography and palaeontology we propose a fundamentally new model of speciation to accommodate our genetic findings in dabbling ducks. This model, we argue, may also shed light on longstanding unresolved general speciation and hybridisation patterns in higher organisms, e.g. in other bird groups with unusually high

  7. Floral traits and pollination ecology of European Arum hybrids.

    PubMed

    Chartier, Marion; Liagre, Suzanne; Weiss-Schneeweiss, Hanna; Kolano, Bozena; Bessière, Jean-Marie; Schönenberger, Jürg; Gibernau, Marc

    2016-02-01

    Hybridisation is common in plants and can affect the genetic diversity and ecology of sympatric parental populations. Hybrids may resemble the parental species in their ecology, leading to competition and/or gene introgression; alternatively, they may diverge from the parental phenotypes, possibly leading to the colonisation of new ecological niches and to speciation. Here, we describe inflorescence morphology, ploidy levels, pollinator attractive scents, and pollinator guilds of natural hybrids of Arum italicum and A. maculatum (Araceae) from a site with sympatric parental populations in southern France to determine how these traits affect the hybrid pollination ecology. Hybrids were characterised by inflorescences with a size and a number of flowers more similar to A. italicum than to A. maculatum. In most cases, hybrid stamens were purple, as in A. maculatum, and spadix appendices yellow, as in A. italicum. Hybrid floral scent was closer to that of A. italicum, but shared some compounds with A. maculatum and comprised unique compounds. Also, the pollinator guild of the hybrids was similar to that of A. italicum. Nevertheless, the hybrids attracted a high proportion of individuals of the main pollinator of A. maculatum. We discuss the effects of hybridisation in sympatric parental zones in which hybrids exhibit low levels of reproductive success, the establishment of reproductive barriers between parental species, the role of the composition of floral attractive scents in the differential attraction of pollinators and in the competition between hybrids and their parental species, and the potential of hybridisation to give rise to new independent lineages. PMID:26552380

  8. From Local Adaptation to Ecological Speciation in Copepod Populations from Neighboring Lakes

    PubMed Central

    Barrera-Moreno, Omar Alfredo; Ciros-Pérez, Jorge; Ortega-Mayagoitia, Elizabeth; Alcántara-Rodríguez, José Arturo; Piedra-Ibarra, Elías

    2015-01-01

    Continental copepods have been derived from several independent invasive events from the sea, but the subsequent evolutionary processes that account for the current diversity in lacustrine environments are virtually unknown. Salinity is highly variable among lakes and constitutes a source of divergent selection driving potential reproductive isolation. We studied four populations of the calanoid copepod Leptodiaptomus cf. sicilis inhabiting four neighboring lakes with a common history (since the Late Pleistocene) located in the Oriental Basin, Mexico; one lake is shallow and varies in salinity periodically (1.4–10 g L-1), while three are deep and permanent, with constant salinity (0.5, 1.1 and 6.5 g L-1, respectively). We hypothesized that (1) these populations belong to a different species than L. sicilis sensu stricto and (2) are experiencing ecologically based divergence due to salinity differences. We assessed morphological and molecular (mtDNA) COI variation, as well as fitness differences and tests of reproductive isolation. Although relationships of the Mexican populations with L. sicilis s.s. could not be elucidated, we identified a clear pattern of divergent selection driven by salinity conditions. The four populations can still be considered a single biological species (sexual recognition and hybridization are still possible in laboratory conditions), but they have diverged into at least three different phenotypes: two locally adapted, specialized in the lakes of constant salinity (saline vs. freshwater), and an intermediate generalist phenotype inhabiting the temporary lake with fluctuating salinity. The specialized phenotypes are poorly suited as migrants, so prezygotic isolation due to immigrant inviability is highly probable. This implication was supported by molecular evidence that showed restricted gene flow, persistence of founder events, and a pattern of allopatric fragmentation. This study showed how ecologically based divergent selection may

  9. From local adaptation to ecological speciation in copepod populations from neighboring lakes.

    PubMed

    Barrera-Moreno, Omar Alfredo; Ciros-Pérez, Jorge; Ortega-Mayagoitia, Elizabeth; Alcántara-Rodríguez, José Arturo; Piedra-Ibarra, Elías

    2015-01-01

    Continental copepods have been derived from several independent invasive events from the sea, but the subsequent evolutionary processes that account for the current diversity in lacustrine environments are virtually unknown. Salinity is highly variable among lakes and constitutes a source of divergent selection driving potential reproductive isolation. We studied four populations of the calanoid copepod Leptodiaptomus cf. sicilis inhabiting four neighboring lakes with a common history (since the Late Pleistocene) located in the Oriental Basin, Mexico; one lake is shallow and varies in salinity periodically (1.4-10 g L(-1)), while three are deep and permanent, with constant salinity (0.5, 1.1 and 6.5 g L(-1), respectively). We hypothesized that (1) these populations belong to a different species than L. sicilis sensu stricto and (2) are experiencing ecologically based divergence due to salinity differences. We assessed morphological and molecular (mtDNA) COI variation, as well as fitness differences and tests of reproductive isolation. Although relationships of the Mexican populations with L. sicilis s.s. could not be elucidated, we identified a clear pattern of divergent selection driven by salinity conditions. The four populations can still be considered a single biological species (sexual recognition and hybridization are still possible in laboratory conditions), but they have diverged into at least three different phenotypes: two locally adapted, specialized in the lakes of constant salinity (saline vs. freshwater), and an intermediate generalist phenotype inhabiting the temporary lake with fluctuating salinity. The specialized phenotypes are poorly suited as migrants, so prezygotic isolation due to immigrant inviability is highly probable. This implication was supported by molecular evidence that showed restricted gene flow, persistence of founder events, and a pattern of allopatric fragmentation. This study showed how ecologically based divergent selection may

  10. Speciation reversal and biodiversity dynamics with hybridization in changing environments.

    PubMed

    Seehausen, Ole; Takimoto, Gaku; Roy, Denis; Jokela, Jukka

    2008-01-01

    A considerable fraction of the world's biodiversity is of recent evolutionary origin and has evolved as a by-product of, and is maintained by, divergent adaptation in heterogeneous environments. Conservationists have paid attention to genetic homogenization caused by human-induced translocations (e.g. biological invasions and stocking), and to the importance of environmental heterogeneity for the ecological coexistence of species. However, far less attention has been paid to the consequences of loss of environmental heterogeneity to the genetic coexistence of sympatric species. Our review of empirical observations and our theoretical considerations on the causes and consequences of interspecific hybridization suggest that a loss of environmental heterogeneity causes a loss of biodiversity through increased genetic admixture, effectively reversing speciation. Loss of heterogeneity relaxes divergent selection and removes ecological barriers to gene flow between divergently adapted species, promoting interspecific introgressive hybridization. Since heterogeneity of natural environments is rapidly deteriorating in most biomes, the evolutionary ecology of speciation reversal ought to be fully integrated into conservation biology. PMID:18034800

  11. Low levels of hybridization between sympatric Arctic char (Salvelinus alpinus) and Dolly Varden char (Salvelinus malma) highlights their genetic distinctiveness and ecological segregation

    PubMed Central

    May-McNally, Shannan L; Quinn, Thomas P; Taylor, Eric B

    2015-01-01

    Understanding the extent of interspecific hybridization and how ecological segregation may influence hybridization requires comprehensively sampling different habitats over a range of life history stages. Arctic char (Salvelinus alpinus) and Dolly Varden (S. malma) are recently diverged salmonid fishes that come into contact in several areas of the North Pacific where they occasionally hybridize. To better quantify the degree of hybridization and ecological segregation between these taxa, we sampled over 700 fish from multiple lake (littoral and profundal) and stream sites in two large, interconnected southwestern Alaskan lakes. Individuals were genotyped at 12 microsatellite markers, and genetic admixture (Q) values generated through Bayesian-based clustering revealed hybridization levels generally lower than reported in a previous study (<0.6% to 5% of samples classified as late-generation hybrids). Dolly Varden and Arctic char tended to make different use of stream habitats with the latter apparently abandoning streams for lake habitats after 2–3 years of age. Our results support the distinct biological species status of Dolly Varden and Arctic char and suggest that ecological segregation may be an important factor limiting opportunities for hybridization and/or the ecological performance of hybrid char. PMID:26356310

  12. Comparison of the reproductive ecology of two sympatric blacktip sharks (Carcharhinus limbatus and Carcharhinus tilstoni) off north-eastern Australia with species identification inferred from vertebral counts.

    PubMed

    Harry, A V; Morgan, J A T; Ovenden, J R; Tobin, A J; Welch, D J; Simpfendorfer, C A

    2012-09-01

    Precaudal vertebral counts were used to distinguish between 237 morphologically similar Carcharhinus limbatus and Carcharhinus tilstoni and were congruent with differences in reproductive ecology between the species. In addition to differing lengths at maturity and adult body size, the two species had asynchronous parturition, were born at different sizes and the relative frequencies of neonates differed in two coastal nursery areas. Despite evidence that hybridization can occur, these differences suggest the species are largely reproductively isolated. PMID:22957866

  13. Habitat preference and the marine-speciation paradox.

    PubMed Central

    Bierne, Nicolas; Bonhomme, François; David, Patrice

    2003-01-01

    Marine organisms challenge the classical theories of local adaptation and speciation because their planktonic larvae have the potential to maintain high gene flow. The marine-speciation paradox is illustrated by contact zones between incipient species that are so large that allopatric divergence seems unlikely. For this reason any mechanism preventing sympatric larvae of two incipient species from coexisting in the same habitats can be a powerful promoter of speciation. The contact zone between two hybridizing taxa of mussel, Mytilus edulis and M. galloprovincialis, in Europe provides an excellent example. Although the zone itself extends over thousands of kilometres, the opportunities for interbreeding are considerably reduced by the small-scale mosaic structure of the zone, where local patches of each taxon alternate at scales of kilometres or less, in response to locally variable ecological factors. Habitat choice by settling larvae would be a less costly mechanism than post-settlement selection to maintain such a mosaic structure. Unfortunately the role of selective settlement has remained hypothetical because larvae could not be scored by classical genetic markers. PCR markers allowed us to study larvae and settlement in ecologically contrasting sites within the zone. We show that only a subset of the genotypes present in the plankton settle in some sites, and that the adults on these sites show the same genetic bias. Genetically based variation in pre-settlement processes therefore accounts for the ecological segregation observed, though it is not the only factor involved in limiting successful interbreeding. The present dataset also supports previous reports of partial spawning asynchrony. PMID:12965032

  14. A high frequency of allopolyploid speciation in the gymnospermous genus Ephedra and its possible association with some biological and ecological features.

    PubMed

    Wu, Hui; Ma, Zhen; Wang, Ming-Ming; Qin, Ai-Li; Ran, Jin-Hua; Wang, Xiao-Quan

    2016-03-01

    The origin and evolution of polyploids have been studied extensively in angiosperms and ferns but very rarely in gymnosperms. With the exception of three species of conifers, all natural polyploid species of gymnosperms belong to Ephedra, in which more than half of the species show polyploid cytotypes. Here, we investigated the origin and evolution of polyploids of Ephedra distributed in the Qinghai-Tibetan Plateau (QTP) and neighbouring areas. Flow cytometry (FCM) was used to measure the ploidy levels of the sampled species that are represented by multiple individuals from different populations, and then, two single-copy nuclear genes (LFY and DDB2) and two chloroplast DNA fragments were used to unravel the possible origins and maternal donors of the polyploids. The results indicate that the studied polyploid species are allopolyploids, and suggest that allotetraploidy is a dominant mode of speciation in Ephedra. The high percentage of polyploids in the genus could be related to some of its biological attributes such as vegetative propagation, a relatively high rate of unreduced gamete formation, and a small genome size relative to most other gymnosperms. Significant ecological divergences between allotetraploids and their putative progenitors were detected by PCAs and anova and Tukey's tests, with the exception of E. saxatilis. The overlap of geographical distributions and ecological niches of some diploid species could have provided opportunities for interspecific hybridization and allopolyploid speciation. PMID:26800145

  15. The behavioural ecology of two sympatric talitrid species, Talitrus saltator (Montagu) and Orchestia gammarellus (Pallas) on a Tyrrhenian sandy beach dune system

    NASA Astrophysics Data System (ADS)

    Colombini, Isabella; Fallaci, Mario; Gagnarli, Elena; Rossano, Claudia; Scapini, Felicita; Chelazzi, Lorenzo

    2013-01-01

    The behavioural ecology of a sub-population of Talitrus saltator living on the sandy shore of the Maremma Regional Park (Italy) was compared with that of Orchestia gammarellus inhabiting the retrodunal dune slack area. Monthly monitoring over a year determined the mean distribution patterns, their changes and whether these overlapped. Standard pitfall traps were placed along transects across the beach-dune-dune slack area. Experiments analysed the diel activity rhythms during spring and the activity patterns of the different age classes and the two sexes were compared within and between species. Local environmental conditions were registered with a microclimatic station. During May and September, plant hummocks were monitored to see whether surface movements of O. gammarellus could be restricted to certain periods of the year and to estimate densities within the vegetation. The plant biomass and moisture conditions within the hummocks were also recorded and substratum samples were collected at the base of the shrubs for laboratory analysis. To test for visual cues, orientation experiments with and without landscape view were carried out on the beach during morning and afternoon hours and contemporaneously for each species. Experiments to test the diel variation of scototaxis to a black shape were also performed over a 24 h period of time under controlled conditions. There was a spatial partitioning of the two species, with T. saltator moving along a sea-land axis according to diel and seasonal changes and with some individuals reaching the back of the dune in particular environmental conditions. No spatial overlap with the zonation patterns of O. gammarellus was observed, which was restricted to the dune slack area. Nocturnal surface activity was observed for both species with juveniles peaking at dawn and with O. gammarellus being strictly more nocturnal than T. saltator. Orientation experiments showed a higher ability of T. saltator to orient towards the

  16. Individual-based modeling of ecological and evolutionary processes

    USGS Publications Warehouse

    DeAngelis, Donald L.; Mooij, Wolf M.

    2005-01-01

    Individual-based models (IBMs) allow the explicit inclusion of individual variation in greater detail than do classical differential-equation and difference-equation models. Inclusion of such variation is important for continued progress in ecological and evolutionary theory. We provide a conceptual basis for IBMs by describing five major types of individual variation in IBMs: spatial, ontogenetic, phenotypic, cognitive, and genetic. IBMs are now used in almost all subfields of ecology and evolutionary biology. We map those subfields and look more closely at selected key papers on fish recruitment, forest dynamics, sympatric speciation, metapopulation dynamics, maintenance of diversity, and species conservation. Theorists are currently divided on whether IBMs represent only a practical tool for extending classical theory to more complex situations, or whether individual-based theory represents a radically new research program. We feel that the tension between these two poles of thinking can be a source of creativity in ecology and evolutionary theory.

  17. Population differentiation without speciation

    PubMed Central

    Magurran, A. E.

    1998-01-01

    Population differentiation is often viewed as an important step towards speciation, and part of the rationale for conserving variation at the intraspecific level is that the potential to generate more biological diversity should be retained. Yet, speciation is not an inevitable consequence of population divergence. This paper reviews recent work on the Trinidadian guppy, Poecilia reticulata, a species that is renowned for its capacity for population differentiation. Guppy populations evolve rapidly, within 101 to 102 generations, as a response to changes in selection exerted by predators. The rates of evolution involved can be up to seven orders of magnitude greater than those seen in the fossil record. Sexual selection, particuarly female choice, appears to reinforce the divergence that natural selection has generated. Perplexingly, however, there is no reproductive isolation (either prezygotic or postzygotic) between populations, even those that have been separated for at least 106 generations. Sexual conflict may be the key to explaining this absence of speciation. Male reproductive behaviour, particularly the high incidence of sneaky mating, may be instrumental in producing sufficient gene flow to prevent reproductive isolation. Sneaky mating has the potential to undermine female choice, and is known to be an important means of sperm transfer in wild populations. Sexual dimorphism, also a result of sexual conflict in guppies, may inhibit speciation in another way. Morphological differences between the sexes, that have arisen for reproductive reasons, mean that males and females are pre-adapted for different foraging niches. This, in turn, reduces the opportunity for the development of feeding polymorphisms, a mechanism that seems to have been important in the sympatric speciation of other fish species.

  18. Low reproductive isolation and highly variable levels of gene flow reveal limited progress towards speciation between European river and brook lampreys.

    PubMed

    Rougemont, Q; Gaigher, A; Lasne, E; Côte, J; Coke, M; Besnard, A-L; Launey, S; Evanno, G

    2015-12-01

    Ecologically based divergent selection is a factor that could drive reproductive isolation even in the presence of gene flow. Population pairs arrayed along a continuum of divergence provide a good opportunity to address this issue. Here, we used a combination of mating trials, experimental crosses and population genetic analyses to investigate the evolution of reproductive isolation between two closely related species of lampreys with distinct life histories. We used microsatellite markers to genotype over 1000 individuals of the migratory parasitic river lamprey (Lampetra fluviatilis) and freshwater-resident nonparasitic brook lamprey (Lampetra planeri) distributed in 10 sympatric and parapatric population pairs in France. Mating trials, parentage analyses and artificial fertilizations demonstrated a low level of reproductive isolation between species even though size-assortative mating may contribute to isolation. Most parapatric population pairs were strongly differentiated due to the joint effects of geographic distance and barriers to migration. In contrast, we found variable levels of gene flow between sympatric populations ranging from panmixia to moderate differentiation, which indicates a gradient of divergence with some population pairs that may correspond to alternative morphs or ecotypes of a single species and others that remain partially isolated. Ecologically based divergent selection may explain these variable levels of divergence among sympatric population pairs, but incomplete genome swamping following secondary contact could have also played a role. Overall, this study illustrates how highly differentiated phenotypes can be maintained despite high levels of gene flow that limit the progress towards speciation. PMID:26348652

  19. 'Becoming a species by becoming a pest' or how two maize pests of the genus Ostrinia possibly evolved through parallel ecological speciation events.

    PubMed

    Bourguet, Denis; Ponsard, Sergine; Streiff, Rejane; Meusnier, Serge; Audiot, Philippe; Li, Jing; Wang, Zhen-Ying

    2014-02-01

    New agricultural pest species attacking introduced crops may evolve from pre-existing local herbivores by ecological speciation, thereby becoming a species by becoming a pest. We compare the evolutionary pathways by which two maize pests (the Asian and the European corn borers, ACB and ECB) in the genus Ostrinia (Lepidoptera, Crambidae) probably diverged from an ancestral species close to the current Adzuki bean borer (ABB). We typed larval Ostrinia populations collected on maize and dicotyledons across China and eastern Siberia, at microsatellite and mitochondrial loci. We found only two clusters: one on maize (as expected) and a single one on dicotyledons despite differences in male mid-tibia morphology, suggesting that all individuals from dicotyledons belonged to the ABB. We found evidence for migrants and hybrids on both host plant types. Hybrids suggest that field reproductive isolation is incomplete between ACB and ABB. Interestingly, a few individuals with an 'ABB-like' microsatellite profile collected on dicotyledons had 'ACB' mtDNA rather than 'ABB-like' mtDNA, whereas the reverse was never found on maize. This suggests asymmetrical gene flow directed from the ACB towards the ABB. Hybrids and backcrosses in all directions were obtained in no-choice tests. In laboratory conditions, they survived as well as parental strain individuals. In Xinjiang, we found ACB and ECB in sympatry, but no hybrids. Altogether, our results suggest that reproductive isolation between ACB and ABB is incomplete and mostly prezygotic. This points to ecological speciation as a possible evolutionary scenario, as previously found for ECB and ABB in Europe. PMID:24289254

  20. Evidence for Divergent Evolution of Growth Temperature Preference in Sympatric Saccharomyces Species

    PubMed Central

    Gonçalves, Paula; Valério, Elisabete; Correia, Cláudia; de Almeida, João M. G. C. F.; Sampaio, José Paulo

    2011-01-01

    The genus Saccharomyces currently includes eight species in addition to the model yeast Saccharomyces cerevisiae, most of which can be consistently isolated from tree bark and soil. We recently found sympatric pairs of Saccharomyces species, composed of one cryotolerant and one thermotolerant species in oak bark samples of various geographic origins. In order to contribute to explain the occurrence in sympatry of Saccharomyces species, we screened Saccharomyces genomic data for protein divergence that might be correlated to distinct growth temperature preferences of the species, using the dN/dS ratio as a measure of protein evolution rates and pair-wise species comparisons. In addition to proteins previously implicated in growth at suboptimal temperatures, we found that glycolytic enzymes were among the proteins exhibiting higher than expected divergence when one cryotolerant and one thermotolerant species are compared. By measuring glycolytic fluxes and glycolytic enzymatic activities in different species and at different temperatures, we subsequently show that the unusual divergence of glycolytic genes may be related to divergent evolution of the glycolytic pathway aligning its performance to the growth temperature profiles of the different species. In general, our results support the view that growth temperature preference is a trait that may have undergone divergent selection in the course of ecological speciation in Saccharomyces. PMID:21674061

  1. Geochemical speciation and ecological risk assessment of selected metals in the surface sediments of the northern Persian Gulf.

    PubMed

    Neyestani, Mahmoud Reza; Bastami, Kazem Darvish; Esmaeilzadeh, Marjan; Shemirani, Farzaneh; Khazaali, Aida; Molamohyeddin, Neda; Afkhami, Majid; Nourbakhsh, Shahram; Dehghani, Mohsen; Aghaei, Sina; Firouzbakht, Mohammad

    2016-08-15

    The present study aimed to geochemical speciation of metals in the surface sediments of the northern Persian Gulf. Metal contents in the sediment were observed in the order: Al>Fe>Cr>Ni>V>Zn>Cu>Co>As>Pb>Cd. The results of sequential extraction procedure revealed that all metals were predominantly associated with the residual fraction. Among the metals, Cu and As exhibited higher bioavailability. The risk assessment code (RAC) indicated that Cu, As and Cd had medium environmental risk at some sampling sites. Based on enrichment factor (EF), Cd and As had moderate to significant enrichment. PMID:27210564

  2. Hawthorn-infesting populations of Rhagoletis pomonella in Mexico and speciation mode plurality.

    PubMed

    Xie, Xianfa; Rull, Juan; Michel, Andrew P; Velez, Sebastian; Forbes, Andrew A; Lobo, Neil F; Aluja, Martin; Feder, Jeffrey L

    2007-05-01

    species. For R. pomonella in the United States, the proximate selection pressures triggering race formation and speciation stem from sympatric host shifts. However, some of the phenological variation contributing to host-related ecological adaptation and reproductive isolation in sympatry at the present time appears to have an older history, having originated and become packaged into inversion polymorphism in allopatry. PMID:17492964

  3. What Is Speciation?

    PubMed

    Shapiro, B Jesse; Leducq, Jean-Baptiste; Mallet, James

    2016-03-01

    Concepts and definitions of species have been debated by generations of biologists and remain controversial. Microbes pose a particular challenge because of their genetic diversity, asexual reproduction, and often promiscuous horizontal gene transfer (HGT). However, microbes also present an opportunity to study and understand speciation because of their rapid evolution, both in nature and in the lab, and small, easily sequenced genomes. Here, we review how microbial population genomics has enabled us to catch speciation "in the act" and how the results have challenged and enriched our concepts of species, with implications for all domains of life. We describe how recombination (including HGT and introgression) has shaped the genomes of nascent microbial, animal, and plant species and argue for a prominent role of natural selection in initiating and maintaining speciation. We ask how universal is the process of speciation across the tree of life, and what lessons can be drawn from microbes? Comparative genomics showing the extent of HGT in natural populations certainly jeopardizes the relevance of vertical descent (i.e., the species tree) in speciation. Nevertheless, we conclude that species do indeed exist as clusters of genetic and ecological similarity and that speciation is driven primarily by natural selection, regardless of the balance between horizontal and vertical descent. PMID:27030977

  4. What Is Speciation?

    PubMed Central

    Shapiro, B. Jesse; Leducq, Jean-Baptiste; Mallet, James

    2016-01-01

    Concepts and definitions of species have been debated by generations of biologists and remain controversial. Microbes pose a particular challenge because of their genetic diversity, asexual reproduction, and often promiscuous horizontal gene transfer (HGT). However, microbes also present an opportunity to study and understand speciation because of their rapid evolution, both in nature and in the lab, and small, easily sequenced genomes. Here, we review how microbial population genomics has enabled us to catch speciation “in the act” and how the results have challenged and enriched our concepts of species, with implications for all domains of life. We describe how recombination (including HGT and introgression) has shaped the genomes of nascent microbial, animal, and plant species and argue for a prominent role of natural selection in initiating and maintaining speciation. We ask how universal is the process of speciation across the tree of life, and what lessons can be drawn from microbes? Comparative genomics showing the extent of HGT in natural populations certainly jeopardizes the relevance of vertical descent (i.e., the species tree) in speciation. Nevertheless, we conclude that species do indeed exist as clusters of genetic and ecological similarity and that speciation is driven primarily by natural selection, regardless of the balance between horizontal and vertical descent. PMID:27030977

  5. Geographic mode of speciation in a mountain specialist Avian family endemic to the Palearctic

    PubMed Central

    Drovetski, Sergei V; Semenov, Georgy; Drovetskaya, Sofya S; Fadeev, Igor V; Red'kin, Yaroslav A; Voelker, Gary

    2013-01-01

    Mountains host greater avian diversity than lowlands at the same latitude due to their greater diversity of habitats stratified along an elevation gradient. Here we test whether this greater ecological heterogeneity promotes sympatric speciation. We selected accentors (Prunellidae), an avian family associated with mountains of the Palearctic, as a model system. Accentors differ in their habitat/elevation preferences and south-central Siberia and Himalayan regions each host 6 of the 13 species in the family. We used sequences of the mtDNA ND2 gene and the intron 9 of the Z chromosome specific ACO1 gene to reconstruct a complete species-level phylogeny of Prunellidae. The tree based on joint analysis of both loci was used to reconstruct the family's biogeographic history and to date the diversification events. We also analyzed the relationship between the node age and sympatry, to determine the geographic mode of speciation in Prunellidae. Our data suggest a Miocene origin of Prunellidae in the Himalayan region. The major division between alpine species (subgenus Laiscopus) and species associated with shrubs (subgenus Prunella) and initial diversification events within the latter happened within the Himalayan region in the Miocene and Pliocene. Accentors colonized other parts of the Palearctic during the Pliocene-Pleistocene transition. This spread across the Palearctic resulted in rapid diversification of accentors. With only a single exception dating to 0.91 Ma, lineages younger than 1.5 Ma are allopatric. In contrast, sympatry values for older nodes are >0. There was no relationship between node age and range symmetry. Allopatric speciation (not to include peripatric) is the predominant geographic mode of speciation in Prunellidae despite the favorable conditions for ecological diversification in the mountains and range overlaps among species. PMID:23789064

  6. Heavy metals in estuarine surface sediments of the Hai River Basin, variation characteristics, chemical speciation and ecological risk.

    PubMed

    Lei, Pei; Zhang, Hong; Shan, Baoqing; Lv, Shucong; Tang, Wenzhong

    2016-04-01

    The Hai River Basin (HRB) is considered to be one of the most polluted areas in China due to the high regional population density and rapid economic development. The estuaries of the HRB, which receive pollutants from terrestrial rivers, may subsequently suffer potential pollution and result in ecological risk of heavy metals. Six heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) were measured in estuarine surface sediments from 10 estuaries of the HRB to investigate their variation characteristics and ecological risks. The spatial difference of Cr, Ni, Pb, and Zn in sediments was higher than that of the rest two elements. The Yongdingxin Estuary (YDX) and Ziyaxin Estuary (ZYX) in the Northern Hai River System (NHRS) were the most severe in terms of heavy metal contamination. According to the Risk Assessment Code (RAC) classification, Cd associated with the exchangeable and carbonate fraction (the average of 21.3 %) indicated medium risk to high risk. More than 50 % of Cr, Cu, Ni, and Zn on average were associated with the residual fraction. Based on the sum of the first three fractions (exchangeable and carbonate + reducible + oxidizable), the mobility order of these heavy metals was Cd >Pb > Zn ≈ Cu > Ni > Cr. Compared to the background values of cinnamon soil, the potential ecological risk index (RI) values ranged from 25.6 to 168, with an average of 91.2, indicating a low ecological risk in estuarine sites of the HRB. Cd and Pb were the dominant contributors to the toxic-response factor (45.8 and 25.5 %, respectively). The results give insight into the different control measures pertaining to heavy metal pollution and risk for both relatively clean estuaries and urban seriously polluted areas, respectively, for the formation of protect strategies of aquatic environment in the HRB. PMID:26758307

  7. Chromosome speciation: Humans, Drosophila, and mosquitoes

    PubMed Central

    Ayala, Francisco J.; Coluzzi, Mario

    2005-01-01

    Chromosome rearrangements (such as inversions, fusions, and fissions) may play significant roles in the speciation between parapatric (contiguous) or partly sympatric (geographically overlapping) populations. According to the “hybrid-dysfunction” model, speciation occurs because hybrids with heterozygous chromosome rearrangements produce dysfunctional gametes and thus have low reproductive fitness. Natural selection will, therefore, promote mutations that reduce the probability of intercrossing between populations carrying different rearrangements and thus promote their reproductive isolation. This model encounters a disabling difficulty: namely, how to account for the spread in a population of a chromosome rearrangement after it first arises as a mutation in a single individual. The “suppressed-recombination” model of speciation points out that chromosome rearrangements act as a genetic filter between populations. Mutations associated with the rearranged chromosomes cannot flow from one to another population, whereas genetic exchange will freely occur between colinear chromosomes. Mutations adaptive to local conditions will, therefore, accumulate differentially in the protected chromosome regions so that parapatric or partially sympatric populations will genetically differentiate, eventually evolving into different species. The speciation model of suppressed recombination has recently been tested by gene and DNA sequence comparisons between humans and chimpanzees, between Drosophila species, and between species related to Anopheles gambiae, the vector of malignant malaria in Africa. PMID:15851677

  8. Genetic isolation between two sympatric host-plant races of the European corn borer, Ostrinia nubilalis Hübner. I. Sex pheromone, moth emergence timing, and parasitism.

    PubMed

    Thomas, Yan; Bethenod, Marie-Thérèse; Pelozuelo, Laurent; Frérot, Brigitte; Bourguet, Denis

    2003-02-01

    Adaptation to different environments may be a powerful source of genetic differentiation between populations. The biological traits selected in each environment can pleiotropically induce assortative mating between individuals of these genetically differentiated populations. This situation may facilitate sympatric speciation. Successful host shifts in phytophagous insects provide some of the best evidence for the ecological speciation that occurs, or has occurred, in sympatry. The European corn borer, Ostrinia nubilalis (Lepidoptera: Crambidae), colonized maize after its introduction into Europe by humans about 500 years ago. In northern France, two sympatric host races feed on maize (Zea mays) and mugwort (Artemisia vulgaris), respectively. We investigated the factors involved in the genetic isolation of these two races at a field site near Paris, France. We identified two biological differences that might make a significant contribution to the genetic divergence between sympatric populations feeding on the two host plants. First, assortative mating may be due to differences in the moth emergence pattern between the two races: mugwort-race moths emerged on average 10 days earlier than maize-race moths. In addition, the males emerged earlier than females in both races. Hence, the likelihood of mating between maize-race males and mugwort-race females was higher than that of mating between mugwort-race males and maize-race females. Second, the females feeding on mugwort and maize produced sex pheromones with different E/Z isomeric ratios of delta-11-tetradecenyl acetate. This difference in mate recognition systems reinforces the potential for assortative mating in the two races. During the experiment, overwintering mortality was much lower on maize than on mugwort. This difference was due to a braconid parasitoid wasp, Macrocentrus cingulum, that killed more than 50% of the larvae overwintering on mugwort but did not infest larvae diapausing on maize. Hence, by

  9. On the origin of species: insights from the ecological genomics of lake whitefish.

    PubMed

    Bernatchez, Louis; Renaut, Sébastien; Whiteley, Andrew R; Derome, Nicolas; Jeukens, Julie; Landry, Lysandre; Lu, Guoqing; Nolte, Arne W; Ostbye, Kjartan; Rogers, Sean M; St-Cyr, Jérôme

    2010-06-12

    In contrast to the large amount of ecological information supporting the role of natural selection as a main cause of population divergence and speciation, an understanding of the genomic basis underlying those processes is in its infancy. In this paper, we review the main findings of a long-term research programme that we have been conducting on the ecological genomics of sympatric forms of whitefish (Coregonus spp.) engaged in the process of speciation. We present this system as an example of how applying a combination of approaches under the conceptual framework of the theory of adaptive radiation has yielded substantial insight into evolutionary processes in a non-model species. We also discuss how the joint use of recent biotechnological developments will provide a powerful means to address issues raised by observations made to date. Namely, we present data illustrating the potential offered by combining next generation sequencing technologies with other genomic approaches to reveal the genomic bases of adaptive divergence and reproductive isolation. Given increasing access to these new genomic tools, we argue that non-model species studied in their ecological context such as whitefish will play an increasingly important role in generalizing knowledge of speciation. PMID:20439281

  10. On the origin of species: insights from the ecological genomics of lake whitefish

    PubMed Central

    Bernatchez, Louis; Renaut, Sébastien; Whiteley, Andrew R.; Derome, Nicolas; Jeukens, Julie; Landry, Lysandre; Lu, Guoqing; Nolte, Arne W.; Østbye, Kjartan; Rogers, Sean M.; St-Cyr, Jérôme

    2010-01-01

    In contrast to the large amount of ecological information supporting the role of natural selection as a main cause of population divergence and speciation, an understanding of the genomic basis underlying those processes is in its infancy. In this paper, we review the main findings of a long-term research programme that we have been conducting on the ecological genomics of sympatric forms of whitefish (Coregonus spp.) engaged in the process of speciation. We present this system as an example of how applying a combination of approaches under the conceptual framework of the theory of adaptive radiation has yielded substantial insight into evolutionary processes in a non-model species. We also discuss how the joint use of recent biotechnological developments will provide a powerful means to address issues raised by observations made to date. Namely, we present data illustrating the potential offered by combining next generation sequencing technologies with other genomic approaches to reveal the genomic bases of adaptive divergence and reproductive isolation. Given increasing access to these new genomic tools, we argue that non-model species studied in their ecological context such as whitefish will play an increasingly important role in generalizing knowledge of speciation. PMID:20439281

  11. Interspecific resource partitioning in sympatric ursids

    USGS Publications Warehouse

    Belant, J.L.; Kielland, K.; Follmann, E.H.; Adams, L.G.

    2006-01-01

    The fundamental niche of a species is rarely if ever realized because the presence of other species restricts it to a narrower range of ecological conditions. The effects of this narrower range of conditions define how resources are partitioned. Resource partitioning has been inferred but not demonstrated previously for sympatric ursids. We estimated assimilated diet in relation to body condition (body fat and lean and total body mass) and reproduction for sympatric brown bears (Ursus arctos) and American black bears (U. americanus) in southcentral Alaska, 1998-2000. Based on isotopic analysis of blood and keratin in claws, salmon (Oncorhynchus spp.) predominated in brown bear diets (>53% annually) whereas black bears assimilated 0-25% salmon annually. Black bears did not exploit salmon during a year with below average spawning numbers, probably because brown bears deterred black bear access to salmon. Proportion of salmon in assimilated diet was consistent across years for brown bears and represented the major portion of their diet. Body size of brown bears in the study area approached mean body size of several coastal brown bear populations, demonstrating the importance of salmon availability to body condition. Black bears occurred at a comparable density (mass:mass), but body condition varied and was related directly to the amount of salmon assimilated in their diet. Both species gained most lean body mass during spring and all body fat during summer when salmon were present. Improved body condition (i.e., increased percentage body fat) from salmon consumption reduced catabolism of lean body mass during hibernation, resulting in better body condition the following spring. Further, black bear reproduction was directly related to body condition; reproductive rates were reduced when body condition was lower. High body fat content across years for brown bears was reflected in consistently high reproductive levels. We suggest that the fundamental niche of black bears

  12. The role of ecologic diversification in sibling speciation of Empidonax flycatchers (Tyrannidae): multigene evidence from mtDNA.

    PubMed

    Johnson, N K; Cicero, C

    2002-10-01

    Avian genera characterized by sibling species with distinctive habitat preferences present an evolutionary enigma in view of the more commonplace occurrence of syntopic congeners that differ strikingly in colour and pattern. No existing theory has explained the evolutionary background that led to these differences. Here we propose that great phenotypic similarity among some groups of sibling species limits their coexistence and that clues to their radiation can be seen in patterns of geographical occurrence. To illustrate our thesis we focused on the New World flycatcher genus Empidonax, a group of 15 species notorious for their great phenotypic similarity. Using 3069 base pairs of mitochondrial DNA from four genes, we produced a complete molecular phylogeny that identified four clades, three of which represent close relatives. The fourth clade includes only E. virescens, which apparently has no close living relatives. The majority of species, including many distant relatives, are completely (58.1%) or essentially (6.7%) allopatric in breeding distribution and exhibit striking ecological segregation into distinctive climate-vegetation zones. Even where ranges overlap, occupancy of the same habitat by different species is rare. Phylogenetic and distributional patterns in Empidonax suggest a peripatric model of stepwise colonization and then range expansion of small groups of pioneers during glacial periods into initially enlarging, distinctive habitats destined to be widespread during interglacials. Vicariance is not indicated in the absence of barriers of appropriate age and geographical position. Rapoport's rule that northern species have larger ranges than southern species is strongly supported. PMID:12296949

  13. Host fidelity is an effective premating barrier between sympatric races of the apple maggot fly.

    PubMed

    Feder, J L; Opp, S B; Wlazlo, B; Reynolds, K; Go, W; Spisak, S

    1994-08-16

    Models of sympatric speciation for phytophagous insects posit a central role for host plant-associated mating as a premating isolating mechanism in lieu of geographic barriers to gene flow. Here, by means of three mark-and-recapture studies, we confirm that host fidelity (i.e., the tendency of an insect to reproduce on the same host species that it used in earlier life-history stages) restricts gene flow between sympatric apple- and hawthorn-infesting races of Rhagoletis pomonella (Diptera: Tephritidae) to approximately 6% per generation. Genetically based differences in host preference, adult eclosion under the "correct" host species, and allochronic isolation contribute to host fidelity in various degrees in the races. The results verify that host-associated adaptation can produce reproductive isolation as a correlated character (a key premise of sympatric speciation). The study also represents one of the few or perhaps only example in animals where the intra-specific isolating effects of specific phenotypes have been quantified in nature. PMID:11607491

  14. Evidence for Cryptic Speciation in Directly Transmitted Gyrodactylid Parasites of Trinidadian Guppies

    PubMed Central

    Xavier, Raquel; Faria, Patricia J.; Paladini, Giuseppe; van Oosterhout, Cock; Johnson, Mireille; Cable, Jo

    2015-01-01

    Cryptic species complexes are common among parasites, which tend to have large populations and are subject to rapid evolution. Such complexes may arise through host-parasite co-evolution and/or host switching. For parasites that reproduce directly on their host, there might be increased opportunities for sympatric speciation, either by exploiting different hosts or different micro-habitats within the same host. The genus Gyrodactylus is a specious group of viviparous monogeneans. These ectoparasites transfer between teleosts during social contact and cause significant host mortality. Their impact on the guppy (Poecilia reticulata), an iconic evolutionary and ecological model species, is well established and yet the population genetics and phylogenetics of these parasites remains understudied. Using mtDNA sequencing of the host and its parasites, we provide evidence of cryptic speciation in Gyrodactylus bullatarudis, G. poeciliae and G. turnbulli. For the COII gene, genetic divergence of lineages within each parasite species ranged between 5.7 and 17.2%, which is typical of the divergence observed between described species in this genus. Different lineages of G. turnbulli and G. poeciliae appear geographically isolated, which could imply allopatric speciation. In addition, for G. poeciliae, co-evolution with a different host species cannot be discarded due to its host range. This parasite was originally described on P. caucana, but for the first time here it is also recorded on the guppy. The two cryptic lineages of G. bullatarudis showed considerable geographic overlap. G. bullatarudis has a known wide host range and it can also utilize a killifish (Anablepsoides hartii) as a temporary host. This killifish is capable of migrating overland and it could act as a transmission vector between otherwise isolated populations. Additional genetic markers are needed to confirm the presence of these cryptic Gyrodactylus species complexes, potentially leading to more in

  15. Support for a 'Center of Origin' in the Coral Triangle: cryptic diversity, recent speciation, and local endemism in a diverse lineage of reef fishes (Gobiidae: Eviota).

    PubMed

    Tornabene, Luke; Valdez, Samantha; Erdmann, Mark; Pezold, Frank

    2015-01-01

    The Coral Triangle is widely regarded as the richest marine biodiversity hot-spot in the world. One factor that has been proposed to explain elevated species-richness within the Coral Triangle is a high rate of in situ speciation within the region itself. Dwarfgobies (Gobiidae: Eviota) are a diverse genus of diminutive cryptobenthic reef fishes with limited dispersal ability, and life histories and ecologies that increase potential for speciation. We use molecular phylogenetic and biogeographic data from two clades of Eviota species to examine patterns, processes and timing associated with species origination within the Coral Triangle. Sequence data from mitochondrial and nuclear DNA were used to generate molecular phylogenies and median-joining haplotype networks for the genus Eviota, with emphasis on the E. nigriventris and E. bifasciata complexes - two species groups with distributions centered in the Coral Triangle. The E. nigriventris and E. bifasciata complexes both contain multiple genetically distinct, geographically restricted color morphs indicative of recently-diverged species originating within the Coral Triangle. Relaxed molecular-clock dating estimates indicate that most speciation events occurred within the Pleistocene, and the geographic pattern of genetic breaks between species corresponds well with similar breaks in other marine fishes and sessile invertebrates. Regional isolation due to sea-level fluctuations may explain some speciation events in these species groups, yet other species formed with no evidence of physical isolation. The timing of diversification events and present day distributions of Eviota species within the Coral Triangle suggest that both allopatric speciation (driven by ephemeral and/or 'soft' physical barriers to gene flow) and sympatric speciation (driven by niche partitioning and assortative mating) may be driving diversification at local scales within the Coral Triangle. The presence of multiple young, highly

  16. Mitogenomics reveals high synteny and long evolutionary histories of sympatric cryptic nematode species.

    PubMed

    Grosemans, Tara; Morris, Krystalynne; Thomas, William Kelley; Rigaux, Annelien; Moens, Tom; Derycke, Sofie

    2016-03-01

    Species with seemingly identical morphology but with distinct genetic differences are abundant in the marine environment and frequently co-occur in the same habitat. Such cryptic species are typically delineated using a limited number of mitochondrial and/or nuclear marker genes, which do not yield information on gene order and gene content of the genomes under consideration. We used next-generation sequencing to study the composition of the mitochondrial genomes of four sympatrically distributed cryptic species of the Litoditis marina species complex (PmI, PmII, PmIII, and PmIV). The ecology, biology, and natural occurrence of these four species are well known, but the evolutionary processes behind this cryptic speciation remain largely unknown. The gene order of the mitochondrial genomes of the four species was conserved, but differences in genome length, gene length, and codon usage were observed. The atp8 gene was lacking in all four species. Phylogenetic analyses confirm that PmI and PmIV are sister species and that PmIII diverged earliest. The most recent common ancestor of the four cryptic species was estimated to have diverged 16 MYA. Synonymous mutations outnumbered nonsynonymous changes in all protein-encoding genes, with the Complex IV genes (coxI-III) experiencing the strongest purifying selection. Our mitogenomic results show that morphologically similar species can have long evolutionary histories and that PmIII has several differences in genetic makeup compared to the three other species, which may explain why it is better adapted to higher temperatures than the other species. PMID:26933490

  17. Kin discrimination between sympatric Bacillus subtilis isolates.

    PubMed

    Stefanic, Polonca; Kraigher, Barbara; Lyons, Nicholas Anthony; Kolter, Roberto; Mandic-Mulec, Ines

    2015-11-10

    Kin discrimination, broadly defined as differential treatment of conspecifics according to their relatedness, could help biological systems direct cooperative behavior toward their relatives. Here we investigated the ability of the soil bacterium Bacillus subtilis to discriminate kin from nonkin in the context of swarming, a cooperative multicellular behavior. We tested a collection of sympatric conspecifics from soil in pairwise combinations and found that despite their history of coexistence, the vast majority formed distinct boundaries when the swarms met. Some swarms did merge, and most interestingly, this behavior was only seen in the most highly related strain pairs. Overall the swarm interaction phenotype strongly correlated with phylogenetic relatedness, indicative of kin discrimination. Using a subset of strains, we examined cocolonization patterns on plant roots. Pairs of kin strains were able to cocolonize roots and formed a mixed-strain biofilm. In contrast, inoculating roots with pairs of nonkin strains resulted in biofilms consisting primarily of one strain, suggestive of an antagonistic interaction among nonkin strains. This study firmly establishes kin discrimination in a bacterial multicellular setting and suggests its potential effect on ecological interactions. PMID:26438858

  18. Ecological character displacement in the face of gene flow: Evidence from two species of nightingales

    PubMed Central

    2011-01-01

    Background Ecological character displacement is a process of phenotypic differentiation of sympatric populations caused by interspecific competition. Such differentiation could facilitate speciation by enhancing reproductive isolation between incipient species, although empirical evidence for it at early stages of divergence when gene flow still occurs between the species is relatively scarce. Here we studied patterns of morphological variation in sympatric and allopatric populations of two hybridizing species of birds, the Common Nightingale (Luscinia megarhynchos) and the Thrush Nightingale (L. luscinia). Results We conducted principal component (PC) analysis of morphological traits and found that nightingale species converged in overall body size (PC1) and diverged in relative bill size (PC3) in sympatry. Closer analysis of morphological variation along geographical gradients revealed that the convergence in body size can be attributed largely to increasing body size with increasing latitude, a phenomenon known as Bergmann's rule. In contrast, interspecific interactions contributed significantly to the observed divergence in relative bill size, even after controlling for the effects of geographical gradients. We suggest that the divergence in bill size most likely reflects segregation of feeding niches between the species in sympatry. Conclusions Our results suggest that interspecific competition for food resources can drive species divergence even in the face of ongoing hybridization. Such divergence may enhance reproductive isolation between the species and thus contribute to speciation. PMID:21609448

  19. Genomics of adaptation and speciation in cichlid fishes: recent advances and analyses in African and Neotropical lineages

    PubMed Central

    Fan, Shaohua; Elmer, Kathryn R.; Meyer, Axel

    2012-01-01

    Cichlid fishes are remarkably phenotypically diverse and species-rich. Therefore, they provide an exciting opportunity for the study of the genetics of adaptation and speciation by natural and sexual selection. Here, we review advances in the genomics and transcriptomics of cichlids, particularly regarding ecologically relevant differences in body shape, trophic apparatus, coloration and patterning, and sex determination. Research conducted so far has focused almost exclusively on African cichlids. To analyse genomic diversity and selection in a Neotropical radiation, we conducted a comparative transcriptomic analysis between sympatric, ecologically divergent crater-lake Midas cichlids (Lake Xiloá Amphilophus amarillo and Amphilophus sagittae). We pyrosequenced (Roche 454) expressed sequence tag (EST) libraries and generated more than 178 000 000 ESTs and identified nine ESTs under positive selection between these sister species (Ka/Ks > 1). None of these ESTs were found to be under selection in African cichlids. Of 11 candidate genes for ecomorphological differentiation in African cichlids, none showed signs of selection between A. amarillo and A. sagittae. Although more population-level studies are now needed to thoroughly document patterns of divergence during speciation of cichlids, available information so far suggests that adaptive phenotypic diversification in Neotropical and African cichlids may be evolving through non-parallel genetic bases. PMID:22201168

  20. Interspecific resource partitioning in sympatric ursids.

    PubMed

    Belant, Jerrold L; Kielland, Knut; Follmann, Erich H; Adams, Layne G

    2006-12-01

    The fundamental niche of a species is rarely if ever realized because the presence of other species restricts it to a narrower range of ecological conditions. The effects of this narrower range of conditions define how resources are partitioned. Resource partitioning has been inferred but not demonstrated previously for sympatric ursids. We estimated assimilated diet in relation to body condition (body fat and lean and total body mass) and reproduction for sympatric brown bears (Ursus arctos) and American black bears (U. americanus) in south-central Alaska, 1998-2000. Based on isotopic analysis of blood and keratin in claws, salmon (Oncorhynchus spp.) predominated in brown bear diets (> 53% annually) whereas black bears assimilated 0-25% salmon annually. Black bears did not exploit salmon during a year with below average spawning numbers, probably because brown bears deterred black bear access to salmon. Proportion of salmon in assimilated diet was consistent across years for brown bears and represented the major portion of their diet. Body size of brown bears in the study area approached mean body size of several coastal brown bear populations, demonstrating the importance of salmon availability to body condition. Black bears occurred at a comparable density (mass:mass), but body condition varied and was related directly to the amount of salmon assimilated in their diet. Both species gained most lean body mass during spring and all body fat during summer when salmon were present. Improved body condition (i.e., increased percentage body fat) from salmon consumption reduced catabolism of lean body mass during hibernation, resulting in better body condition the following spring. Further, black bear reproduction was directly related to body condition; reproductive rates were reduced when body condition was lower. High body fat content across years for brown bears was reflected in consistently high reproductive levels. We suggest that the fundamental niche of black

  1. Divergence in the calling songs between sympatric and allopatric populations of the southern wood cricket Gryllus fultoni (Orthoptera: Gryllidae).

    PubMed

    Jang, Y; Gerhardt, H C

    2006-03-01

    In the eastern United States the wood cricket Gryllus fultoni (Orthoptera: Gryllidae) occurs in sympatry with G. vernalis in an area between eastern Kansas and west of the Appalachian Mountains. Calling songs were recorded from 13 sympatric and allopatric localities. Both field and laboratory recordings showed that chirp rate (CR) and pulse rate (PR) overlapped extensively between allopatric populations of G. fultoni and sympatric populations of G. vernalis; by contrast, there was little or no overlap in these variables between sympatric populations of these two species. Divergence in PR and CR between the two species was thus greater in areas of sympatry than in areas of allopatry. Our field and laboratory studies of G. fultoni calling songs thus demonstrate the pattern expected of character displacement and support the genetic assumptions of this hypothesis. Other possible explanations for the sympatric divergence such as ecological character displacement and clinal variation are discussed. PMID:16599922

  2. Sympatric genetic differentiation of a generalist pathogenic fungus, Botrytis cinerea, on two different host plants, grapevine and bramble.

    PubMed

    Fournier, E; Giraud, T

    2008-01-01

    Prime candidates for sympatric ecological divergence include parasites that differentiate via host shifts, because different host species exert strong disruptive selection and because both hosts and parasites are continually co-evolving. Sympatric divergence may be fostered even more strongly in phytopathogenic fungi, in particular those where sex must occur on the host, which allows adaptation alone to restrict gene flow between populations developing on different hosts. We sampled populations of Botrytis cinerea, a generalist ascomycete fungus, on sympatric grapes and brambles in six regions in France. Microsatellite data were analyzed using standard population genetics, a population graph analysis and a Bayesian approach. In addition to confirming that B. cinerea reproduces sexually, our results showed that the fungal populations on the two hosts were significantly differentiated, indicating restricted gene flow, even in sympatry. In contrast, only weak geographical differentiation could be detected. These results support the possibility of sympatric divergence associated with host use in generalist parasites. PMID:18028352

  3. Integrative analyses unveil speciation linked to host plant shift in Spialia butterflies.

    PubMed

    Hernández-Roldán, Juan L; Dapporto, Leonardo; Dincă, Vlad; Vicente, Juan C; Hornett, Emily A; Šíchová, Jindra; Lukhtanov, Vladimir A; Talavera, Gerard; Vila, Roger

    2016-09-01

    Discovering cryptic species in well-studied areas and taxonomic groups can have profound implications in understanding eco-evolutionary processes and in nature conservation because such groups often involve research models and act as flagship taxa for nature management. In this study, we use an array of techniques to study the butterflies in the Spialia sertorius species group (Lepidoptera, Hesperiidae). The integration of genetic, chemical, cytogenetic, morphological, ecological and microbiological data indicates that the sertorius species complex includes at least five species that differentiated during the last three million years. As a result, we propose the restitution of the species status for two taxa often treated as subspecies, Spialia ali (Oberthür, 1881) stat. rest. and Spialia therapne (Rambur, 1832) stat. rest., and describe a new cryptic species Spialia rosae Hernández-Roldán, Dapporto, Dincă, Vicente & Vila sp. nov. Spialia sertorius (Hoffmannsegg, 1804) and S. rosae are sympatric and synmorphic, but show constant differences in mitochondrial DNA, chemical profiles and ecology, suggesting that S. rosae represents a case of ecological speciation involving larval host plant and altitudinal shift, and apparently associated with Wolbachia infection. This study exemplifies how a multidisciplinary approach can reveal elusive cases of hidden diversity. PMID:27393640

  4. Tempo and mode of speciation in Holacanthus angelfishes based on RADseq markers.

    PubMed

    Tariel, Juliette; Longo, Gary C; Bernardi, Giacomo

    2016-05-01

    In this study we estimated the timing of speciation events in a group of angelfishes using 1186 RADseq markers corresponding to 94,880 base pairs. The genus Holacanthus comprises seven species, including two clades of Panama trans-Isthmian geminates, which diverged approximately 3-3.5Mya. These clades diversified within the Tropical Eastern Pacific (TEP, three species) and Tropical Western Atlantic (TWA, two species) which our data suggest to have occurred within the past 1.5My in both ocean basins, but may have proceeded via different mechanisms. In the TEP, speciation is likely to have followed a peripatric pathway, while in the TWA, sister species are currently partially sympatric, thus raising the possibility of sympatric speciation. This study highlights the use of RADseq markers for estimating both divergence times and modes of speciation at a 1-3My timescale. PMID:26876637

  5. Special Speciation

    ERIC Educational Resources Information Center

    Countryman, Lyn L.; Maroo, Jill D.

    2015-01-01

    Considerable anecdotal evidence indicates that some of the most difficult concepts that both high school and undergraduate elementary-education students struggle with are those surrounding evolutionary principles, especially speciation. It's no wonder that entry-level biology students are confused, when biologists have multiple definitions of…

  6. Genome differentiation in a species pair of coregonine fishes: an extremely rapid speciation driven by stress-activated retrotransposons mediating extensive ribosomal DNA multiplications

    PubMed Central

    2013-01-01

    Background Sympatric species pairs are particularly common in freshwater fishes associated with postglacial lakes in northern temperate environments. The nature of divergences between co-occurring sympatric species, factors contributing to reproductive isolation and modes of genome evolution is a much debated topic in evolutionary biology addressed by various experimental tools. To the best of our knowledge, nobody approached this field using molecular cytogenetics. We examined chromosomes and genomes of one postglacial species pair, sympatric European winter-spawning Coregonus albula and the local endemic dwarf-sized spring-spawning C. fontanae, both originating in Lake Stechlin. We have employed molecular cytogenetic tools to identify the genomic differences between the two species of the sympatric pair on the sub-chromosomal level of resolution. Results Fluorescence in situ hybridization (FISH) experiments consistently revealed a distinct variation in the copy number of loci of the major ribosomal DNA (the 45S unit) between C. albula and C. fontanae genomes. In C. fontanae, up to 40 chromosomes were identified to bear a part of the major ribosomal DNA, while in C. albula only 8–10 chromosomes possessed these genes. To determine mechanisms how such extensive genome alternation might have arisen, a PCR screening for retrotransposons from genomic DNA of both species was performed. The amplified retrotransposon Rex1 was used as a probe for FISH mapping onto chromosomes of both species. These experiments showed a clear co-localization of the ribosomal DNA and the retrotransposon Rex1 in a pericentromeric region of one or two acrocentric chromosomes in both species. Conclusion We demonstrated genomic consequences of a rapid ecological speciation on the level undetectable by neither sequence nor karyotype analysis. We provide indirect evidence that ribosomal DNA probably utilized the spreading mechanism of retrotransposons subsequently affecting recombination rates

  7. Ecology.

    ERIC Educational Resources Information Center

    National Audubon Society, New York, NY.

    This set of teaching aids consists of nine Audubon Nature Bulletins, providing teachers and students with informational reading on various ecological topics. The bulletins have these titles: Schoolyard Laboratories, Owls and Predators, The Forest Community, Life in Freshwater Marshes, Camouflage in the Animal World, Life in the Desert, The…

  8. Niche differentiation and dietary seasonality among sympatric gorillas and chimpanzees in Loango National Park (Gabon) revealed by stable isotope analysis.

    PubMed

    Oelze, Vicky M; Head, Josephine S; Robbins, Martha M; Richards, Michael; Boesch, Christophe

    2014-01-01

    The feeding ecology of sympatric great ape species yields valuable information for palaeodietary reconstructions in sympatric early hominin species. However, no isotopic references on sympatrically living apes and their feeding ecology are currently available. Here we present the first isotopic study on sympatric great apes, namely western lowland gorillas (Gorilla gorilla gorilla) and central chimpanzees (Pan troglodytes troglodytes) from Loango National Park, Gabon. We successfully analyzed the stable carbon and nitrogen isotope ratios in a selection of food plants (n = 31) and hair samples (n = 30) retrieved from sleeping nests to test whether niche partitioning among sympatric chimpanzees and gorillas is detectable using isotope analysis of hair. Ape hair strands with roots were sectioned into sequential segments (n = 100) to investigate temporal isotopic variation related to seasonal variations in food resources. We found significant δ(13)C differences between herbaceous plants and fruits, most likely due to canopy effects. While the δ(13)C values of chimpanzees indicate the consumption of fruit, the low δ(13)C values in gorilla hair indicate folivory, most likely the consumption of (13)C-depleted herbaceous vegetation. Our isotopic data also confirmed dietary overlap between chimpanzees and gorillas, which varied by season. Gorillas showed significant variation in δ(13)C values in response to season due to shifting proportions of herbaceous plants versus fruits. In chimpanzees, significant seasonal variation in δ(15)N was likely related to the seasonal availability of fruit species with particularly high δ(15)N values. In summary, we found isotopic evidence for niche partitioning and seasonal dietary variation among sympatric great apes at Loango. These findings provide a valuable reference for palaeodietary research on fossil hominins using δ(13)C analyses, particularly for studies focusing on sympatric taxa and on temporal isotopic variation

  9. Ecological adaptation and reproductive isolation in sympatry: genetic and phenotypic evidence for native host races of Rhagoletis pomonella.

    PubMed

    Powell, Thomas H Q; Forbes, Andrew A; Hood, Glen R; Feder, Jeffrey L

    2014-02-01

    Ecological speciation with gene flow may be an important mode of diversification for phytophagous insects. The recent shift of Rhagoletis pomonella from its native host downy hawthorn (Crataegus mollis) to introduced apple (Malus domestica) in the northeastern United States is a classic example of sympatric host race formation. Here, we test whether R. pomonella has similarly formed host races on four native Crataegus species in the southern United States: western mayhaw (C. opaca), blueberry hawthorn (C. brachyacantha), southern red hawthorn (C. mollis var. texana) and green hawthorn (C. viridis). These four southern hosts differ from each other in their fruiting phenology and in the volatile compounds emitted from the surface of their fruits. These two traits form the basis of ecological reproductive isolation between downy hawthorn and apple flies in the north. We report evidence from microsatellite population surveys and eclosion studies supporting the existence of genetically differentiated and partially reproductively isolated host races of southern hawthorn flies. The results provide an example of host shifting and ecological divergence involving native plants and imply that speciation with gene flow may be commonly initiated in Rhagoletis when ecological opportunity presents itself. PMID:24351094

  10. Geographic variation in advertisement calls of a Microhylid frog - testing the role of drift and ecology.

    PubMed

    Lee, Ko-Huan; Shaner, Pei-Jen L; Lin, Yen-Po; Lin, Si-Min

    2016-05-01

    Acoustic signals for mating are important traits that could drive population differentiation and speciation. Ecology may play a role in acoustic divergence through direct selection (e.g., local adaptation to abiotic environment), constraint of correlated traits (e.g., acoustic traits linked to another trait under selection), and/or interspecific competition (e.g., character displacement). However, genetic drift alone can also drive acoustic divergence. It is not always easy to differentiate the role of ecology versus drift in acoustic divergence. In this study, we tested the role of ecology and drift in shaping geographic variation in the advertisement calls of Microhyla fissipes. We examined three predictions based on ecological processes: (1) the correlation between temperature and call properties across M. fissipes populations; (2) the correlation between call properties and body size across M. fissipes populations; and (3) reproductive character displacement (RCD) in call properties between M. fissipes populations that are sympatric with and allopatric to a congener M. heymonsi. To test genetic drift, we examined correlations among call divergence, geographic distance, and genetic distance across M. fissipes populations. We recorded the advertisement calls from 11 populations of M. fissipes in Taiwan, five of which are sympatrically distributed with M. heymonsi. We found geographic variation in both temporal and spectral properties of the advertisement calls of M. fissipes. However, the call properties were not correlated with local temperature or the callers' body size. Furthermore, we did not detect RCD. By contrast, call divergence, geographic distance, and genetic distance between M. fissipes populations were all positively correlated. The comparisons between phenotypic Q st (P st) and F st values did not show significant differences, suggesting a role of drift. We concluded that genetic drift, rather than ecological processes, is the more likely

  11. Separation in flowering time contributes to the maintenance of sympatric cryptic plant lineages

    PubMed Central

    Michalski, Stefan G; Durka, Walter

    2015-01-01

    Sympatric cryptic lineages are a challenge for the understanding of species coexistence and lineage diversification as well as for management, conservation, and utilization of plant genetic resources. In higher plants studies providing insights into the mechanisms creating and maintaining sympatric cryptic lineages are rare. Here, using microsatellites and chloroplast sequence data, morphometric analyses, and phenological observations, we ask whether sympatrically coexisting lineages in the common wetland plant Juncus effusus are ecologically differentiated and reproductively isolated. Our results show two genetically highly differentiated, homoploid lineages within J. effusus that are morphologically cryptic and have similar preference for soil moisture content. However, flowering time differed significantly between the lineages contributing to reproductive isolation and the maintenance of these lineages. Furthermore, the later flowering lineage suffered less from predispersal seed predation by a Coleophora moth species. Still, we detected viable and reproducing hybrids between both lineages and the earlier flowering lineage and J. conglomeratus, a coexisting close relative. Flowering time differentiation between the lineages can be explained by neutral divergence alone and together with a lack of postzygotic isolation mechanisms; the sympatric coexistence of these lineages is most likely the result of an allopatric origin with secondary contact. PMID:26078854

  12. Evolution and Ecophysiology of the Industrial Producer Hypocrea jecorina (Anamorph Trichoderma reesei) and a New Sympatric Agamospecies Related to It

    PubMed Central

    Druzhinina, Irina S.; Komoń-Zelazowska, Monika; Atanasova, Lea; Seidl, Verena; Kubicek, Christian P.

    2010-01-01

    Background Trichoderma reesei, a mitosporic green mould, was recognized during the WW II based on a single isolate from the Solomon Islands and since then used in industry for production of cellulases. It is believed to be an anamorph (asexual stage) of the common pantropical ascomycete Hypocrea jecorina. Methodology/Principal Findings We combined molecular evolutionary analysis and multiple methods of phenotype profiling in order to reveal the genetic relationship of T. reesei to H. jecorina. The resulting data show that the isolates which were previously identified as H. jecorina by means of morphophysiology and ITS1 and 2 (rRNA gene cluster) barcode in fact comprise several species: i) H. jecorina/T. reesei sensu stricto which contains most of the teleomorphs (sexual stages) found on dead wood and the wild-type strain of T. reesei QM 6a; ii) T. parareesei nom. prov., which contains all strains isolated as anamorphs from soil; iii) and two other hypothetical new species for which only one or two isolates are available. In silico tests for recombination and in vitro mating experiments revealed a history of sexual reproduction for H. jecorina and confirmed clonality for T. parareesei nom. prov. Isolates of both species were consistently found worldwide in pantropical climatic zone. Ecophysiological comparison of H. jecorina and T. parareesei nom. prov. revealed striking differences in carbon source utilization, conidiation intensity, photosensitivity and mycoparasitism, thus suggesting adaptation to different ecological niches with the high opportunistic potential for T. parareesei nom. prov. Conclusions Our data prove that T. reesei belongs to a holomorph H. jecorina and displays a history of worldwide gene flow. We also show that its nearest genetic neighbour - T. parareesei nom. prov., is a cryptic phylogenetic agamospecies which inhabits the same biogeographic zone. These two species thus provide a so far rare example of sympatric speciation within saprotrophic

  13. Speciation genetics: current status and evolving approaches

    PubMed Central

    Wolf, Jochen B. W.; Lindell, Johan; Backström, Niclas

    2010-01-01

    The view of species as entities subjected to natural selection and amenable to change put forth by Charles Darwin and Alfred Wallace laid the conceptual foundation for understanding speciation. Initially marred by a rudimental understanding of hereditary principles, evolutionists gained appreciation of the mechanistic underpinnings of speciation following the merger of Mendelian genetic principles with Darwinian evolution. Only recently have we entered an era where deciphering the molecular basis of speciation is within reach. Much focus has been devoted to the genetic basis of intrinsic postzygotic isolation in model organisms and several hybrid incompatibility genes have been successfully identified. However, concomitant with the recent technological advancements in genome analysis and a newfound interest in the role of ecology in the differentiation process, speciation genetic research is becoming increasingly open to non-model organisms. This development will expand speciation research beyond the traditional boundaries and unveil the genetic basis of speciation from manifold perspectives and at various stages of the splitting process. This review aims at providing an extensive overview of speciation genetics. Starting from key historical developments and core concepts of speciation genetics, we focus much of our attention on evolving approaches and introduce promising methodological approaches for future research venues. PMID:20439277

  14. Do specialized flowers promote reproductive isolation? Realized pollination accuracy of three sympatric Pedicularis species

    PubMed Central

    Armbruster, W. Scott; Shi, Xiao-Qing; Huang, Shuang-Quan

    2014-01-01

    Background and Aims Interest in pollinator-mediated evolutionary divergence of flower phenotype and speciation in plants has been at the core of plant evolutionary studies since Darwin. Specialized pollination is predicted to lead to reproductive isolation and promote speciation among sympatric species by promoting partitioning of (1) the species of pollinators used, (2) when pollinators are used, or (3) the sites of pollen placement. Here this last mechanism is investigated by observing the pollination accuracy of sympatric Pedicularis species (Orobanchacae). Methods Pollinator behaviour was observed on three species of Pedicularis (P. densispica, P. tricolor and P. dichotoma) in the Hengduan Mountains, south-west China. Using fluorescent powder and dyed pollen, the accuracy was assessed of stigma contact with, and pollen deposition on, pollinating bumble-bees, respectively. Key Results All three species of Pedicularis were pollinated by bumble-bees. It was found that the adaptive accuracy of female function was much higher than that of male function in all three flower species. Although peak pollen deposition corresponded to the optimal location on the pollinator (i.e. the site of stigma contact) for each species, substantial amounts of pollen were scattered over much of the bees' bodies. Conclusions The Pedicularis species studied in the eastern Himalayan region did not conform with Grant's ‘Pedicularis Model’ of mechanical reproductive isolation. The specialized flowers of this diverse group of plants seem unlikely to have increased the potential for reproductive isolation or influenced rates of speciation. It is suggested instead that the extreme species richness of the Pedicularis clade was generated in other ways and that specialized flowers and substantial pollination accuracy evolved as a response to selection generated by the diversity of co-occurring congeners. PMID:24047714

  15. Selective maintenance of allozyme differences among sympatric host races of the apple maggot fly.

    PubMed

    Feder, J L; Roethele, J B; Wlazlo, B; Berlocher, S H

    1997-10-14

    Whether phytophagous insects can speciate in sympatry when they shift and adapt to new host plants is a controversial question. One essential requirement for sympatric speciation is that disruptive selection outweighs gene flow between insect populations using different host plants. Empirical support for host-related selection (i.e., fitness trade-offs) is scant, however. Here, we test for host-dependent selection acting on apple (Malus pumila)- and hawthorn (Crataegus spp.)-infesting races of Rhagoletis pomonella (Diptera: Tephritidae). In particular, we examine whether the earlier fruiting phenology of apple trees favors pupae in deeper states of diapause (or with slower metabolisms/development rates) in the apple fly race. By experimentally lengthening the time period preceding winter, we exposed hawthorn race pupae to environmental conditions typically faced by apple flies. This exposure induced a significant genetic response at six allozyme loci in surviving hawthorn fly adults toward allele frequencies found in the apple race. The sensitivity of hawthorn fly pupae to extended periods of warm weather therefore selects against hawthorn flies that infest apples and helps to maintain the genetic integrity of the apple race by counteracting gene flow from sympatric hawthorn populations. Our findings confirm that postzygotic reproductive isolation can evolve as a pleiotropic consequence of host-associated adaptation, a central tenet of nonallopatric speciation. They also suggest that one reason for the paucity of reported fitness trade-offs is a failure to consider adequately costs associated with coordinating an insect's life cycle with the phenology of its host plant. PMID:11038585

  16. Australasian sky islands act as a diversity pump facilitating peripheral speciation and complex reversal from narrow endemic to widespread ecological supertramp

    PubMed Central

    Toussaint, Emmanuel F A; Sagata, Katayo; Surbakti, Suriani; Hendrich, Lars; Balke, Michael

    2013-01-01

    The Australasian archipelago is biologically extremely diverse as a result of a highly puzzling geological and biological evolution. Unveiling the underlying mechanisms has never been more attainable as molecular phylogenetic and geological methods improve, and has become a research priority considering increasing human-mediated loss of biodiversity. However, studies of finer scaled evolutionary patterns remain rare particularly for megadiverse Melanesian biota. While oceanic islands have received some attention in the region, likewise insular mountain blocks that serve as species pumps remain understudied, even though Australasia, for example, features some of the most spectacular tropical alpine habitats in the World. Here, we sequenced almost 2 kb of mitochondrial DNA from the widespread diving beetle Rhantus suturalis from across Australasia and the Indomalayan Archipelago, including remote New Guinean highlands. Based on expert taxonomy with a multigene phylogenetic backbone study, and combining molecular phylogenetics, phylogeography, divergence time estimation, and historical demography, we recover comparably low geographic signal, but complex phylogenetic relationships and population structure within R. suturalis. Four narrowly endemic New Guinea highland species are subordinated and two populations (New Guinea, New Zealand) seem to constitute cases of ongoing speciation. We reveal repeated colonization of remote mountain chains where haplotypes out of a core clade of very widespread haplotypes syntopically might occur with well-isolated ones. These results are corroborated by a Pleistocene origin approximately 2.4 Ma ago, followed by a sudden demographic expansion 600,000 years ago that may have been initiated through climatic adaptations. This study is a snapshot of the early stages of lineage diversification by peripatric speciation in Australasia, and supports New Guinea sky islands as cradles of evolution, in line with geological evidence suggesting

  17. Incipient ring speciation revealed by a migratory divide.

    PubMed

    Irwin, Darren E

    2009-07-01

    Ever since Ernst Mayr (1942) called ring species the 'perfect demonstration of speciation', they have attracted much interest from researchers examining how two species evolve from one. In a ring species, two sympatric and reproductively isolated forms are connected by a long chain of intermediate populations that encircle a geographic barrier. Ring species have the potential to demonstrate that speciation can occur without complete geographic isolation, in contrast to the classic model of allopatric speciation. They also allow researchers to examine the causes of reproductive isolation in the contact zone and to use spatial variation to infer the steps by which speciation occurs. According to the classical definition, a ring species must have (i) gradual variation through a chain of populations connecting two divergent and sympatric forms, and (ii) complete or nearly complete reproductive isolation between the terminal forms. But evolutionary biologists now recognize that the process of speciation might often occur with some periods of geographic contact and hybridization between diverging forms; during these phases, even partial reproductive isolation can limit gene flow and permit further divergence to occur. In this issue Bensch et al. (2009) make an exciting and important contribution by extending the ring species concept to a case in which the divergence is much younger and not yet advanced to full reproductive isolation. Their study of geographic variation in willow warblers (Phylloscopus trochilus; Fig. 1) provides a beautiful example of gradual variation through a ring of populations connecting two forms that are partially reproductively isolated where they meet, possibly due to divergent migratory behaviours of the terminal forms. PMID:19457189

  18. Competitive speciation in quantitative genetic models.

    PubMed

    Drossel, B; Mckane, A

    2000-06-01

    We study sympatric speciation due to competition in an environment with a broad distribution of resources. We assume that the trait under selection is a quantitative trait, and that mating is assortative with respect to this trait. Our model alternates selection according to Lotka-Volterra-type competition equations, with reproduction using the ideas of quantitative genetics. The recurrence relations defined by these equations are studied numerically and analytically. We find that when a population enters a new environment, with a broad distribution of unexploited food sources, the population distribution broadens under a variety of conditions, with peaks at the edge of the distribution indicating the formation of subpopulations. After a long enough time period, the population can split into several subpopulations with little gene flow between them. PMID:10816369

  19. Ecological opportunity and the evolution of habitat preferences in an arid-zone bird: implications for speciation in a climate-modified landscape

    PubMed Central

    Norman, Janette A.; Christidis, Les

    2016-01-01

    Bioclimatic models are widely used to investigate the impacts of climate change on species distributions. Range shifts are expected to occur as species track their current climate niche yet the potential for exploitation of new ecological opportunities that may arise as ecosystems and communities remodel is rarely considered. Here we show that grasswrens of the Amytornis textilis-modestus complex responded to new ecological opportunities in Australia’s arid biome through shifts in habitat preference following the development of chenopod shrublands during the late Plio-Pleistocene. We find evidence of spatially explicit responses to climatically driven landscape changes including changes in niche width and patterns of population growth. Conservation of structural and functional aspects of the ancestral niche appear to have facilitated recent habitat shifts, while demographic responses to late Pleistocene climate change provide evidence for the greater resilience of populations inhabiting the recently evolved chenopod shrubland communities. Similar responses could occur under future climate change in species exposed to novel ecological conditions, or those already occupying spatially heterogeneous landscapes. Mechanistic models that consider structural and functional aspects of the niche along with regional hydro-dynamics may be better predictors of future climate responses in Australia’s arid biome than bioclimatic models alone. PMID:26787111

  20. Ecological opportunity and the evolution of habitat preferences in an arid-zone bird: implications for speciation in a climate-modified landscape.

    PubMed

    Norman, Janette A; Christidis, Les

    2016-01-01

    Bioclimatic models are widely used to investigate the impacts of climate change on species distributions. Range shifts are expected to occur as species track their current climate niche yet the potential for exploitation of new ecological opportunities that may arise as ecosystems and communities remodel is rarely considered. Here we show that grasswrens of the Amytornis textilis-modestus complex responded to new ecological opportunities in Australia's arid biome through shifts in habitat preference following the development of chenopod shrublands during the late Plio-Pleistocene. We find evidence of spatially explicit responses to climatically driven landscape changes including changes in niche width and patterns of population growth. Conservation of structural and functional aspects of the ancestral niche appear to have facilitated recent habitat shifts, while demographic responses to late Pleistocene climate change provide evidence for the greater resilience of populations inhabiting the recently evolved chenopod shrubland communities. Similar responses could occur under future climate change in species exposed to novel ecological conditions, or those already occupying spatially heterogeneous landscapes. Mechanistic models that consider structural and functional aspects of the niche along with regional hydro-dynamics may be better predictors of future climate responses in Australia's arid biome than bioclimatic models alone. PMID:26787111

  1. Reproductive isolation and introgression between sympatric Mimulus species.

    PubMed

    Kenney, Amanda M; Sweigart, Andrea L

    2016-06-01

    Incompletely isolated species provide an opportunity to investigate the genetic mechanisms and evolutionary forces that maintain distinct species in the face of ongoing gene flow. Here, we use field surveys and reduced representation sequencing to characterize the patterns of reproductive isolation, admixture and genomic divergence between populations of the outcrossing wildflower Mimulus guttatus and selfing M. nasutus. Focusing on a single site where these two species have come into secondary contact, we find that phenological isolation is strong, although incomplete, and is likely driven by divergence in response to photoperiod. In contrast to previous field studies, which have suggested that F1 -hybrid formation might be rare, we discover patterns of genomic variation consistent with ongoing introgression. Strikingly, admixed individuals vary continuously from highly admixed to nearly pure M. guttatus, demonstrating ongoing hybridization and asymmetric introgression from M. nasutus into M. guttatus. Patterns of admixture and divergence across the genome show that levels of introgression are more variable than expected by chance. Some genomic regions show a reduced introgression, including one region that overlaps a critical photoperiod QTL, whereas other regions show elevated levels of interspecific gene flow. In addition, we observe a genome-wide negative relationship between absolute divergence and the local recombination rate, potentially indicating natural selection against M. nasutus ancestry in M. guttatus genetic backgrounds. Together, our results suggest that Mimulus speciation is both ongoing and dynamic and that a combination of divergence in phenology and mating system, as well as selection against interspecific alleles, likely maintains these sympatric species. PMID:27038381

  2. Daily Rhythm of Mutualistic Pollinator Activity and Scent Emission in Ficus septica: Ecological Differentiation between Co-Occurring Pollinators and Potential Consequences for Chemical Communication and Facilitation of Host Speciation

    PubMed Central

    Conchou, Lucie; Cabioch, Léa; Rodriguez, Lillian J. V.; Kjellberg, Finn

    2014-01-01

    The mutualistic interaction between Ficus and their pollinating agaonid wasps constitutes an extreme example of plant-insect co-diversification. Most Ficus species are locally associated with a single specific agaonid wasp species. Specificity is ensured by each fig species emitting a distinctive attractive scent. However, cases of widespread coexistence of two agaonid wasp species on the same Ficus species are documented. Here we document the coexistence of two agaonid wasp species in Ficus septica: one yellow-colored and one black-colored. Our results suggest that their coexistence is facilitated by divergent ecological traits. The black species is longer-lived (a few more hours) and is hence active until later in the afternoon. Some traits of the yellow species must compensate for this advantage for their coexistence to be stable. In addition, we show that the composition of the scent emitted by receptive figs changes between sunrise and noon. The two species may therefore be exposed to somewhat different ranges of receptive fig scent composition and may consequently diverge in the way they perceive and/or respond to scents. Whether such situations may lead to host plant speciation is an open question. PMID:25105796

  3. SPECIATE - EPA'S DATABASE OF SPECIATED EMISSION PROFILES

    EPA Science Inventory

    SPECIATE is the U.S. Environmental Protection Agency's (EPA) repository of total organic compound (TOC) and particulate matter (PM) speciation profiles for emissions from air pollution sources. The data base has recently been updated and an associated report has recently been re...

  4. High inbreeding, limited recombination and divergent evolutionary patterns between two sympatric morel species in China

    PubMed Central

    Du, Xi-Hui; Zhao, Qi; Xu, Jianping; Yang, Zhu L.

    2016-01-01

    As highly prized, popular mushrooms, morels are widely distributed in the northern hemisphere, with China as a modern centre of speciation and diversity. Overharvesting of morels has caused concern over how to effectively preserve their biological and genetic diversity. However, little is known about their population biology and life cycle. In this study, we selected two sympatric phylogenetic species, Mel-13 (124 collections from 11 geographical locations) and Morchella eohespera (156 collections from 14 geographical locations), using fragments of 4 DNA sequences, to analyse their genetic structure. Our results indicated significant differentiation among geographic locations in both species, whereas no obvious correlation between genetic and geographic distance was identified in either species. M. eohespera exhibited a predominantly clonal population structure with limited recombination detected in only 1 of the 14 geographic locations. In contrast, relatively frequent recombination was identified in 6 of the 11 geographic locations of Mel-13. Our analysis indicated that the sympatric species Mel-13 and M. eohespera might have divergent evolutionary patterns, with the former showing signatures of recent population expansion and the latter being relatively stable. Interestingly, we found no heterozygosity but strong evidence for genealogical incongruence, indicating a high level of inbreeding and hybridisation among morel species. PMID:26928176

  5. Deep sympatric mtDNA divergence in the autumnal moth (Epirrita autumnata)

    PubMed Central

    Kvie, Kjersti S; Hogner, Silje; Aarvik, Leif; Lifjeld, Jan T; Johnsen, Arild

    2013-01-01

    Deep sympatric intraspecific divergence in mtDNA may reflect cryptic species or formerly distinct lineages in the process of remerging. Preliminary results from DNA barcoding of Scandinavian butterflies and moths showed high intraspecific sequence variation in the autumnal moth, Epirrita autumnata. In this study, specimens from different localities in Norway and some samples from Finland and Scotland, with two congeneric species as outgroups, were sequenced with mitochondrial and nuclear markers to resolve the discrepancy found between mtDNA divergence and present species-level taxonomy. We found five COI sub-clades within the E. autumnata complex, most of which were sympatric and with little geographic structure. Nuclear markers (ITS2 and Wingless) showed little variation and gave no indications that E. autumnata comprises more than one species. The samples were screened with primers for Wolbachia outer surface gene (wsp) and 12% of the samples tested positive. Two Wolbachia strains were associated with different mtDNA sub-clades within E. autumnata, which may indicate indirect selection/selective sweeps on haplotypes. Our results demonstrate that deep mtDNA divergences are not synonymous with cryptic speciation and this has important implications for the use of mtDNA in species delimitation, like in DNA barcoding. PMID:23404314

  6. Female preference for sympatric vs. allopatric male throat color morphs in the mesquite lizard (Sceloporus grammicus) species complex.

    PubMed

    Bastiaans, Elizabeth; Bastiaans, Mary Jane; Morinaga, Gen; Castañeda Gaytán, José Gamaliel; Marshall, Jonathon C; Bane, Brendan; de la Cruz, Fausto Méndez; Sinervo, Barry

    2014-01-01

    Color polymorphic sexual signals are often associated with alternative reproductive behaviors within populations, and the number, frequency, or type of morphs present often vary among populations. When these differences lead to assortative mating by population, the study of such polymorphic taxa may shed light on speciation mechanisms. We studied two populations of a lizard with polymorphic throat color, an important sexual signal. Males in one population exhibit orange, yellow, or blue throats; whereas males in the other exhibit orange, yellow, or white throats. We assessed female behavior when choosing between allopatric and sympatric males. We asked whether females discriminated more when the allopatric male was of an unfamiliar morph than when the allopatric male was similar in coloration to the sympatric male. We found that female rejection of allopatric males relative to sympatric males was more pronounced when males in a pair were more different in throat color. Our findings may help illuminate how behavioral responses to color morph differences between populations with polymorphic sexual signals contribute to reproductive isolation. PMID:24718297

  7. Female Preference for Sympatric vs. Allopatric Male Throat Color Morphs in the Mesquite Lizard (Sceloporus grammicus) Species Complex

    PubMed Central

    Bastiaans, Elizabeth; Bastiaans, Mary Jane; Morinaga, Gen; Castañeda Gaytán, José Gamaliel; Marshall, Jonathon C.; Bane, Brendan; de la Cruz, Fausto Méndez; Sinervo, Barry

    2014-01-01

    Color polymorphic sexual signals are often associated with alternative reproductive behaviors within populations, and the number, frequency, or type of morphs present often vary among populations. When these differences lead to assortative mating by population, the study of such polymorphic taxa may shed light on speciation mechanisms. We studied two populations of a lizard with polymorphic throat color, an important sexual signal. Males in one population exhibit orange, yellow, or blue throats; whereas males in the other exhibit orange, yellow, or white throats. We assessed female behavior when choosing between allopatric and sympatric males. We asked whether females discriminated more when the allopatric male was of an unfamiliar morph than when the allopatric male was similar in coloration to the sympatric male. We found that female rejection of allopatric males relative to sympatric males was more pronounced when males in a pair were more different in throat color. Our findings may help illuminate how behavioral responses to color morph differences between populations with polymorphic sexual signals contribute to reproductive isolation. PMID:24718297

  8. Dualism and conflicts in understanding speciation.

    PubMed

    Schilthuizen, M

    2000-12-01

    Speciation is a central but elusive issue in evolutionary biology. Over the past sixty years, the subject has been studied within a framework conceived by Ernst Mayr and Theodosius Dobzhansky and subsequently developed further by numerous other workers. In this "isolation" theory, the evolution of reproductive isolation is a key element of speciation; natural selection is given only secondary importance while gene flow is considered prohibitive to the process. In this paper, I argue that certain elements in this approach have produced confusion and irreconcilability among students of speciation. The more prominent debates in speciation (i.e., the species definition, sympatry/allopatry, and the role of reinforcement) all derive from an inherent conflict between the "isolation" theory and Darwin's "selection" view on species and speciation (in which disruptive selection is crucial). New data, mainly from field ecology, molecular population genetics, laboratory studies with Drosophila and computer analysis, all suggest that the isolation theory may no longer be the most desirable vantage point from which to explore speciation. Instead, environmental selection in large populations, often unimpeded by ongoing gene flow, appears to be the decisive element. The traditional preoccupation with reproductive isolation has created gaps in our knowledge of several crucial issues, mainly regarding the role of environmental selection and its connection with mate selection. PMID:11084629

  9. [Study on Speciation Analysis and Ecological Risk Assessment of Heavy Metals in Surface Sediments in Gansu, Ningxia and Inner Mongolia Sections of the Yellow River in Wet Season with HR-ICP-MS].

    PubMed

    Ma, Xiao-ling; Liu, Jing-jun; Zuo, Hang; Huang, Fang; Liu, Ying

    2015-04-01

    In order to continuously study the contents, pollution condition and potential ecological risk of heavy metals in surface sediments in Gansu, Ningxia and Inner Mongolia sections of the Yellow River in wet seasons in different years, the speciation analysis of 9 kinds of heavy metals including Cd, Pb, Cr, Ni, Cu, V, Co, Zn and Mn, pollution condition and potential ecological risk of heavy metals in surface sediments from 10 sampling sites like Baotoufuqiao (S2), Shizuishantaolezhen (S6) and Wujinxia (S9) in Gansu, Ningxia and Inner Mongolia sections of the Yellow River in 2012 wet season were studied with BCR sequential extraction and high resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS) based on our previous works. The results implied that the order of heavy metals average contents in the 10 sediment samples were the same: Mn>V> Zn>Cr>Cu>Ni>Pb>Co>Cd. In the sediments, heavy metals mainly existed in the form of residual fraction, which indicated that the bioavailability or environmental impact was low. Results of geo-accumulation indices (Igeo) showed that Igeo(CD), was the largest among the heavy metals with the strongest pollution, while IGEO(Mn)was the smallest. Enrichment factor (EF) indicated that only Cd and Cu were enriched at some sampling sites. In S5, because EFcd reached 4. 69, Cd was affected by human activities obviously and the result was consistent with I. Potential ecological risk index (RI) implied that the RI values in S1, S2 and S5 were between 150 and 300, which belonged to moderate polluting degree, while others were less than 150, belonging to light pollution degree. The results of this paper could not only provide reliable experimental data and theoretical basis for the relevant departments, but also supply the technical support for constructing mathematics model of sediments-pollutants transport, systematically researching the migration and transformation rule of persistent toxic substances and environmental assessment in

  10. The genetic basis for fruit odor discrimination in Rhagoletis flies and its significance for sympatric host shifts.

    PubMed

    Dambroski, Hattie R; Linn, Charles; Berlocher, Stewart H; Forbes, Andrew A; Roelofs, Wendell; Feder, Jeffrey L

    2005-09-01

    Rhagoletis pomonella (Diptera: Tephritidae) use volatile compounds emitted from the surface of ripening fruit as important chemosensory cues for recognizing and distinguishing among alternative host plants. Host choice is of evolutionary significance in Rhagoletis because these flies mate on or near the fruit of their respective host plants. Differences in host choice based on fruit odor discrimination therefore result in differential mate choice and prezygotic reproductive isolation, facilitating sympatric speciation in the absence of geographic isolation. We test for a genetic basis for host fruit odor discrimination through an analysis of F2 and backcross hybrids constructed between apple-, hawthorn-, and flowering dogwood-infesting Rhagoletis flies. We recovered a significant proportion (30-65%) of parental apple, hawthorn, and dogwood fly response phenotypes in F2 hybrids, despite the general failure of F1 hybrids to reach odor source spheres. Segregation patterns in F2 and backcross hybrids suggest that only a modest number of allelic differences at a few loci may underlie host fruit odor discrimination. In addition, a strong bias was observed for F2 and backcross flies to orient to the natal fruit blend of their maternal grandmother, implying the existence of cytonuclear gene interactions. We explore the implications of our findings for the evolutionary dynamics of sympatric host race formation and speciation. PMID:16261733

  11. Population genetics of ecological communities with DNA barcodes: An example from New Guinea Lepidoptera

    PubMed Central

    Craft, Kathleen J.; Pauls, Steffen U.; Darrow, Karolyn; Miller, Scott E.; Hebert, Paul D. N.; Helgen, Lauren E.; Novotny, Vojtech; Weiblen, George D.

    2010-01-01

    Comparative population genetics of ecological guilds can reveal generalities in patterns of differentiation bearing on hypotheses regarding the origin and maintenance of community diversity. Contradictory estimates of host specificity and beta diversity in tropical Lepidoptera (moths and butterflies) from New Guinea and the Americas have sparked debate on the role of host-associated divergence and geographic isolation in explaining latitudinal diversity gradients. We sampled haplotypes of mitochondrial cytochrome c oxidase I from 28 Lepidoptera species and 1,359 individuals across four host plant genera and eight sites in New Guinea to estimate population divergence in relation to host specificity and geography. Analyses of molecular variance and haplotype networks indicate varying patterns of genetic structure among ecologically similar sympatric species. One-quarter lacked evidence of isolation by distance or host-associated differentiation, whereas 21% exhibited both. Fourteen percent of the species exhibited host-associated differentiation without geographic isolation, 18% showed the opposite, and 21% were equivocal, insofar as analyses of molecular variance and haplotype networks yielded incongruent patterns. Variation in dietary breadth among community members suggests that speciation by specialization is an important, but not universal, mechanism for diversification of tropical Lepidoptera. Geographically widespread haplotypes challenge predictions of vicariance biogeography. Dispersal is important, and Lepidoptera communities appear to be highly dynamic according to the various phylogeographic histories of component species. Population genetic comparisons among herbivores of major tropical and temperate regions are needed to test predictions of ecological theory and evaluate global patterns of biodiversity. PMID:20202924

  12. Aggression and Food Resource Competition between Sympatric Hermit Crab Species

    PubMed Central

    Tran, Mark V.; O’Grady, Matthew; Colborn, Jeremiah; Van Ness, Kimberly; Hill, Richard W.

    2014-01-01

    The vertical zonation patterns of intertidal organisms have been topics of interest to marine ecologists for many years, with interspecific food competition being implicated as a contributing factor to intertidal community organization. In this study, we used behavioral bioassays to examine the potential roles that interspecific aggression and food competition have on the structuring of intertidal hermit crab assemblages. We studied two ecologically similar, sympatric hermit crab species, Clibanarius digueti [1] and Paguristes perrieri [2], which occupy adjacent zones within the intertidal region of the Gulf of California. During the search phase of foraging, C. digueti showed higher frequencies of aggressive behaviors than P. perrieri. In competition assays, C. digueti gained increased access to food resources compared to P. perrieri. The results suggest that food competition may play an important role in structuring intertidal hermit crab assemblages, and that the zonation patterns of Gulf of California hermit crab species may be the result of geographical displacement by the dominant food competitor (C. digueti). PMID:24632897

  13. Sub-Decadal Resolution in Sediments of Late Miocene Lake Pannon Reveals Speciation of Cyprideis (Crustacea, Ostracoda)

    PubMed Central

    Gross, Martin; Piller, Werner E.

    2015-01-01

    Late Miocene "Lake Pannon" (~11.3 Ma) was a remnant of the Central Paratethyan Sea. Successive freshening and constantly changing environmental conditions, like oxygenation, nutrition and substrate led to a well-documented radiation in molluscs and ostracods. Among ostracods (small crustaceans), Cyprideis is one of the most common genera in "Lake Pannon", as well as in several other ancient lakes, showing numerous adaptations and speciations. Here, we present high-resolution data from an early transgression of "Lake Pannon" in the Eastern Styrian Basin (SE Austria). Mataschen clay pit is in the focus of geologic and paleontologic research since 20 years and its geologic and paleoecologic evolution is well-documented. We drilled five cores covering a ~2.3 m long section and completely sampled it in 5-mm thick intervals to reconstruct minute changes in the ostracod fauna over a transgression of a brackish water body. The dominant genus, Cyprideis, is represented by three species C. mataschensis, C. kapfensteinensis and C. ex gr. pannonica. Through morphometric analyses we highlight the variance of each taxon and suggest that there is no direct ecologic control on size or shape. Furthermore, we found a second, co-occurring morphotype of C. kapfensteinensis which is directly related to an elevation of salinities above 13 psu. The presence of two intermediate specimens between the two morphotypes in the sample directly below the first appearance of C. kapfensteinensis B leads us to the conclusion that we are facing a speciation event leading to four sympatric species of Cyprideis. PMID:25902063

  14. Geographic variation in animal colour polymorphisms and its role in speciation.

    PubMed

    McLean, Claire A; Stuart-Fox, Devi

    2014-11-01

    Polymorphic species, in which multiple variants coexist within a population, are often used as model systems in evolutionary biology. Recent research has been dominated by the hypothesis that polymorphism can be a precursor to speciation. To date, the majority of research regarding polymorphism and speciation has focused on whether polymorphism is maintained within a population or whether morphs within populations may diverge to form separate species (sympatric speciation); however, the geographical context of speciation in polymorphic systems is likely to be both diverse and complex. In this review, we draw attention to the geographic variation in morph composition and frequencies that characterises many, if not most polymorphic species. Recent theoretical and empirical developments suggest that such variation in the number, type and frequency of morphs present among populations can increase the probability of speciation. Thus, the geographical context of a polymorphism requires a greater research focus. Here, we review the prevalence, causes and evolutionary consequences of geographic variation in polymorphism in colour-polymorphic animal species. The prevalence and nature of geographic variation in polymorphism suggests that polymorphism may be a precursor to and facilitate speciation more commonly than appreciated previously. We argue that a better understanding of the processes generating geographic variation in polymorphism is vital to understanding how polymorphism can promote speciation. PMID:24528520

  15. Evolutionary animation: how do molecular phylogenies compare to Mayr's reconstruction of speciation patterns in the sea?

    PubMed

    Palumbi, Stephen R; Lessios, H A

    2005-05-01

    Ernst Mayr used the geography of closely related species in various stages of increasing divergence to "animate" the process of geographic, or allopatric, speciation. This approach was applied to a wide set of taxa, and a seminal paper by Mayr used it to explore speciation patterns in tropical sea urchins. Since then, taxonomic information in several of these genera has been augmented by detailed molecular phylogenies. We compare Mayr's animation with the phylogenies of eight sea urchin genera placed by Mayr into four speciation groups. True to Mayr's predictions, early-stage genera have on average lower species divergence and more polytypic species than genera in later stages. For six of these genera, we also have information about the evolution of the gamete recognition protein bindin, which is critical to reproductive isolation. These comparisons show that later-stage genera with many sympatric species tend to be those with rapid bindin evolution. By contrast, early-stage genera with few sympatric species are not necessarily earlier in the divergence process; they happen to be those with slow rates of bindin evolution. These results show that the rate of speciation in sea urchins does not only depend on the steady accumulation of genome divergence over time, but also on the rate of evolution of gamete recognition proteins. The animation method used by Mayr is generally supported by molecular phylogenies. However, the existence of multiple rates in the acquisition of reproductive isolation complicates placement of different genera in an evolutionary series. PMID:15851681

  16. Sympatric inhibition and niche differentiation suggest alternative coevolutionary trajectories among Streptomycetes

    PubMed Central

    Kinkel, Linda L; Schlatter, Daniel C; Xiao, Kun; Baines, Anita D

    2014-01-01

    Soil bacteria produce a diverse array of antibiotics, yet our understanding of the specific roles of antibiotics in the ecological and evolutionary dynamics of microbial interactions in natural habitats remains limited. Here, we show a significant role for antibiotics in mediating antagonistic interactions and nutrient competition among locally coexisting Streptomycete populations from soil. We found that antibiotic inhibition is significantly more intense among sympatric than allopatric Streptomycete populations, indicating local selection for inhibitory phenotypes. For sympatric but not allopatric populations, antibiotic inhibition is significantly positively correlated with niche overlap, indicating that inhibition is targeted toward bacteria that pose the greatest competitive threat. Our results support the hypothesis that antibiotics serve as weapons in mediating local microbial interactions in soil and suggest that coevolutionary niche displacement may reduce the likelihood of an antibiotic arms race. Further insight into the diverse roles of antibiotics in microbial ecology and evolution has significant implications for understanding the persistence of antibiotic inhibitory and resistance phenotypes in environmental microbes, optimizing antibiotic drug discovery and developing strategies for managing microbial coevolutionary dynamics to enhance inhibitory phenotypes. PMID:24152720

  17. Killer whale call frequency is similar across the oceans, but varies across sympatric ecotypes.

    PubMed

    Filatova, Olga A; Miller, Patrick J O; Yurk, Harald; Samarra, Filipa I P; Hoyt, Erich; Ford, John K B; Matkin, Craig O; Barrett-Lennard, Lance G

    2015-07-01

    Killer whale populations may differ in genetics, morphology, ecology, and behavior. In the North Pacific, two sympatric populations ("resident" and "transient") specialize on different prey (fish and marine mammals) and retain reproductive isolation. In the eastern North Atlantic, whales from the same populations have been observed feeding on both fish and marine mammals. Fish-eating North Pacific "residents" are more genetically related to eastern North Atlantic killer whales than to sympatric mammal-eating "transients." In this paper, a comparison of frequency variables in killer whale calls recorded from four North Pacific resident, two North Pacific transient, and two eastern North Atlantic populations is reported to assess which factors drive the large-scale changes in call structure. Both low-frequency and high-frequency components of North Pacific transient killer whale calls have significantly lower frequencies than those of the North Pacific resident and North Atlantic populations. The difference in frequencies could be related to ecological specialization or to the phylogenetic history of these populations. North Pacific transient killer whales may have genetically inherited predisposition toward lower frequencies that may shape their learned repertoires. PMID:26233024

  18. The coexistence of seven sympatric fulvettas in Ailao Mountains, Ejia Town, Yunnan Province

    PubMed Central

    XIA, Ji; WU, Fei; HU, Wan-Zhao; FANG, Jian-Ling; YANG, Xiao-Jun

    2015-01-01

    The coexistence of ecologically similar species sharing sympatric areas is a central issue of community ecology. Niche differentiation is required at least in one dimension to avoid competitive exclusion. From 2012-2014, by adopting the methods of mist-nets and point counts to evaluate spatial niche partitioning and morphological differentiations, we explored the coexistence mechanisms of seven sympatric fulvettas in Ailao Mountains, Ejia town, Yunnan Province, China. The microhabitats of these seven fulvettas were significantly different in elevation, roost site height and vegetation coverage, indicating a spatial niche segregation in different levels. Approximately, 90.30% of the samples were correctly classified by linear discriminant analysis (LDA) with correct rates at 91.20%-100%, except the White-browed fulvetta (Alcippe vinipectus) (65.4%) and the Streak-throated fulvetta (A. cinereiceps) (74.6%). The seven fulvettas were classified into four guilds based on their specific morphological characters, suggesting that the species in each guild use their unique feeding ways to realize resource partitioning in the overlapped areas. These finding indicate that through multi-dimensional spatial niche segregation and divergence in resource utilizing, the inter-specific competition among these seven fulvettas is minimized, whereas, coexistence is promoted. PMID:25730457

  19. The coexistence of seven sympatric fulvettas in Ailao Mountains, Ejia Town, Yunnan Province.

    PubMed

    Xia, Ji; Wu, Fei; Hu, Wan-Zhao; Fang, Jian-Ling; Yang, Xiao-Jun

    2015-01-18

    The coexistence of ecologically similar species sharing sympatric areas is a central issue of community ecology. Niche differentiation is required at least in one dimension to avoid competitive exclusion. From 2012-2014, by adopting the methods of mist-nets and point counts to evaluate spatial niche partitioning and morphological differentiations, we explored the coexistence mechanisms of seven sympatric fulvettas in Ailao Mountains, Ejia town, Yunnan Province, China. The microhabitats of these seven fulvettas were significantly different in elevation, roost site height and vegetation coverage, indicating a spatial niche segregation in different levels. Approximately, 90.30% of the samples were correctly classified by linear discriminant analysis (LDA) with correct rates at 91.20%-100%, except the White-browed fulvetta (Alcippe vinipectus) (65.4%) and the Streak-throated fulvetta (A. cinereiceps) (74.6%). The seven fulvettas were classified into four guilds based on their specific morphological characters, suggesting that the species in each guild use their unique feeding ways to realize resource partitioning in the overlapped areas. These finding indicate that through multi-dimensional spatial niche segregation and divergence in resource utilizing, the inter-specific competition among these seven fulvettas is minimized, whereas, coexistence is promoted. PMID:25730457

  20. Speciation without Pre-Defined Fitness Functions

    PubMed Central

    Gras, Robin; Golestani, Abbas; Hendry, Andrew P.; Cristescu, Melania E.

    2015-01-01

    The forces promoting and constraining speciation are often studied in theoretical models because the process is hard to observe, replicate, and manipulate in real organisms. Most models analyzed to date include pre-defined functions influencing fitness, leaving open the question of how speciation might proceed without these built-in determinants. To consider the process of speciation without pre-defined functions, we employ the individual-based ecosystem simulation platform EcoSim. The environment is initially uniform across space, and an evolving behavioural model then determines how prey consume resources and how predators consume prey. Simulations including natural selection (i.e., an evolving behavioural model that influences survival and reproduction) frequently led to strong and distinct phenotypic/genotypic clusters between which hybridization was low. This speciation was the result of divergence between spatially-localized clusters in the behavioural model, an emergent property of evolving ecological interactions. By contrast, simulations without natural selection (i.e., behavioural model turned off) but with spatial isolation (i.e., limited dispersal) produced weaker and overlapping clusters. Simulations without natural selection or spatial isolation (i.e., behaviour model turned off and high dispersal) did not generate clusters. These results confirm the role of natural selection in speciation by showing its importance even in the absence of pre-defined fitness functions. PMID:26372462

  1. Identity of two sympatric species of Orius (Heteroptera: Anthocoridae)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The two minute pirate bugs, Orius insidiosus (Say) (Heteroptera: Anthocoridae) and Orius pumilio (Champion) (Heteroptera: Anthocoridae), are closely related and sympatric in north Florida. Interspecific matings between the two species did not result in viable progeny. Although the morphological stru...

  2. Determinants of the Sympatric Host-Pathogen Relationship in Tuberculosis

    PubMed Central

    David, Susana; Mateus, A. R. A.; Duarte, Elsa L.; Albuquerque, José; Portugal, Clara; Sancho, Luísa; Lavinha, João; Gonçalves, Guilherme

    2015-01-01

    Major contributions from pathogen genome analysis and host genetics have equated the possibility of Mycobacterium tuberculosis co-evolution with its human host leading to more stable sympatric host–pathogen relationships. However, the attribution to either sympatric or allopatric categories depends on the resolution or grain of genotypic characterization. We explored the influence on the sympatric host-pathogen relationship of clinical (HIV infection and multidrug-resistant tuberculosis [MDRTB]) and demographic (gender and age) factors in regards to the genotypic grain by using spacer oligonucleotide typing (spoligotyping) for classification of M. tuberculosis strains within the Euro-American lineage. We analyzed a total of 547 tuberculosis (TB) cases, from six year consecutive sampling in a setting with high TB-HIV coinfection (32.0%). Of these, 62.0% were caused by major circulating pathogen genotypes. The sympatric relationship was defined according to spoligotype in comparison to the international spoligotype database SpolDB4. While no significant association with Euro-American lineage was observed with any of the factors analyzed, increasing the resolution with spoligotyping evidenced a significant association of MDRTB with sympatric strains, regardless of the HIV status. Furthermore, distribution curves of the prevalence of sympatric and allopatric TB in relation to patients’ age showed an accentuation of the relevance of the age of onset in the allopatric relationship, as reflected in the trimodal distribution. On the contrary, sympatric TB was characterized by the tendency towards a typical (standard) distribution curve. Our results suggest that within the Euro-American lineage a greater degree of genotyping fine-tuning is necessary in modeling the biological processes behind the host-pathogen interplay. Furthermore, prevalence distribution of sympatric TB to age was suggestive of host genetic determinisms driven by more common variants. PMID:26529092

  3. SPECIATE 4.2: speciation Database Development Documentation

    EPA Science Inventory

    SPECIATE is the U.S. Environmental Protection Agency's (EPA) repository of volatile organic gas and particulate matter (PM) speciation profiles of air pollution sources. Among the many uses of speciation data, these source profiles are used to: (1) create speciated emissions inve...

  4. Population genomics of local adaptation versus speciation in coral reef fishes (Hypoplectrus spp, Serranidae).

    PubMed

    Picq, Sophie; McMillan, W Owen; Puebla, Oscar

    2016-04-01

    Are the population genomic patterns underlying local adaptation and the early stages of speciation similar? Addressing this question requires a system in which (i) local adaptation and the early stages of speciation can be clearly identified and distinguished, (ii) the amount of genetic divergence driven by the two processes is similar, and (iii) comparisons can be repeated both taxonomically (for local adaptation) and geographically (for speciation). Here, we report just such a situation in the hamlets (Hypoplectrus spp), brightly colored reef fishes from the wider Caribbean. Close to 100,000 SNPs genotyped in 126 individuals from three sympatric species sampled in three repeated populations provide genome-wide levels of divergence that are comparable among allopatric populations (F st estimate = 0.0042) and sympatric species (F st estimate = 0.0038). Population genetic, clustering, and phylogenetic analyses reveal very similar patterns for local adaptation and speciation, with a large fraction of the genome undifferentiated (F st estimate ≈ 0), a very small proportion of F st outlier loci (0.05-0.07%), and remarkably few repeated outliers (1-3). Nevertheless, different loci appear to be involved in the two processes in Hypoplectrus, with only 7% of the most differentiated SNPs and outliers shared between populations and species comparisons. In particular, a tropomyosin (Tpm4) and a previously identified hox (HoxCa) locus emerge as candidate loci (repeated outliers) for local adaptation and speciation, respectively. We conclude that marine populations may be locally adapted notwithstanding shallow levels of genetic divergence, and that from a population genomic perspective, this process does not appear to differ fundamentally from the early stages of speciation. PMID:27099711

  5. Speciation reversal in European whitefish (Coregonus lavaretus (L.)) caused by competitor invasion.

    PubMed

    Bhat, Shripathi; Amundsen, Per-Arne; Knudsen, Rune; Gjelland, Karl Øystein; Fevolden, Svein-Erik; Bernatchez, Louis; Præbel, Kim

    2014-01-01

    Invasion of exotic species has caused the loss of biodiversity and imparts evolutionary and ecological changes in the introduced systems. In northern Fennoscandia, European whitefish (Coregonus lavaretus (L.)) is a highly polymorphic species displaying adaptive radiations into partially reproductively isolated and thus genetically differentiated sympatric morphs utilizing the planktivorous and benthivorous food niche in many lakes. In 1993, Lake Skrukkebukta was invaded by vendace (Coregonus albula (L.)) which is a zooplanktivorous specialist. The vendace displaced the densely rakered whitefish from its preferred pelagic niche to the benthic habitat harbouring the large sparsely rakered whitefish. In this study, we investigate the potential influence of the vendace invasion on the breakdown of reproductive isolation between the two whitefish morphs. We inferred the genotypic and phenotypic differentiation between the two morphs collected at the arrival (1993) and 15 years after (2008) the vendace invasion using 16 microsatellite loci and gill raker numbers, the most distinctive adaptive phenotypic trait between them. The comparison of gill raker number distributions revealed two modes growing closer over 15 years following the invasion. Bayesian analyses of genotypes revealed that the two genetically distinct whitefish morphs that existed in 1993 had collapsed into a single population in 2008. The decline in association between the gill raker numbers and admixture values over 15 years corroborates the findings from the Bayesian analysis. Our study thus suggests an apparent decrease of reproductive isolation in a morph-pair of European whitefish within 15 years (≃ 3 generations) following the invasion of a superior trophic competitor (vendace) in a subarctic lake, reflecting a situation of "speciation in reverse". PMID:24626131

  6. Speciation Reversal in European Whitefish (Coregonus lavaretus (L.)) Caused by Competitor Invasion

    PubMed Central

    Bhat, Shripathi; Amundsen, Per-Arne; Knudsen, Rune; Gjelland, Karl Øystein; Fevolden, Svein-Erik; Bernatchez, Louis; Præbel, Kim

    2014-01-01

    Invasion of exotic species has caused the loss of biodiversity and imparts evolutionary and ecological changes in the introduced systems. In northern Fennoscandia, European whitefish (Coregonus lavaretus (L.)) is a highly polymorphic species displaying adaptive radiations into partially reproductively isolated and thus genetically differentiated sympatric morphs utilizing the planktivorous and benthivorous food niche in many lakes. In 1993, Lake Skrukkebukta was invaded by vendace (Coregonus albula (L.)) which is a zooplanktivorous specialist. The vendace displaced the densely rakered whitefish from its preferred pelagic niche to the benthic habitat harbouring the large sparsely rakered whitefish. In this study, we investigate the potential influence of the vendace invasion on the breakdown of reproductive isolation between the two whitefish morphs. We inferred the genotypic and phenotypic differentiation between the two morphs collected at the arrival (1993) and 15 years after (2008) the vendace invasion using 16 microsatellite loci and gill raker numbers, the most distinctive adaptive phenotypic trait between them. The comparison of gill raker number distributions revealed two modes growing closer over 15 years following the invasion. Bayesian analyses of genotypes revealed that the two genetically distinct whitefish morphs that existed in 1993 had collapsed into a single population in 2008. The decline in association between the gill raker numbers and admixture values over 15 years corroborates the findings from the Bayesian analysis. Our study thus suggests an apparent decrease of reproductive isolation in a morph-pair of European whitefish within 15 years (≃ 3 generations) following the invasion of a superior trophic competitor (vendace) in a subarctic lake, reflecting a situation of “speciation in reverse”. PMID:24626131

  7. Evidence for gene flow between two sympatric mealybug species (Insecta; Coccoidea; Pseudococcidae).

    PubMed

    Kol-Maimon, Hofit; Ghanim, Murad; Franco, José Carlos; Mendel, Zvi

    2014-01-01

    Occurrence of inter-species hybrids in natural populations might be evidence of gene flow between species. In the present study we found evidence of gene flow between two sympatric, genetically related scale insect species--the citrus mealybug Planococcus citri (Risso) and the vine mealybug Planococcus ficus (Signoret). These species can be distinguished by morphological, behavioral, and molecular traits. We employed the sex pheromones of the two respective species to study their different patterns of male attraction. We also used nuclear ITS2 (internal transcribed spacer 2) and mitochondrial COI (Cytochrome c oxidase sub unit 1) DNA sequences to characterize populations of the two species, in order to demonstrate the outcome of a possible gene flow between feral populations of the two species. Our results showed attraction to P. ficus pheromones of all tested populations of P. citri males but not vice versa. Furthermore, ITS2 sequences revealed the presence of 'hybrid females' among P. citri populations but not among those of P. ficus. 'hybrid females' from P. citri populations identified as P. citri females according to COI sequences. We offer two hypotheses for these results. 1) The occurrence of phenotypic and genotypic traits of P. ficus in P. citri populations may be attributed to both ancient and contemporary gene flow between their populations; and 2) we cannot rule out that an ancient sympatric speciation by which P. ficus emerged from P. citri might have led to the present situation of shared traits between these species. In light of these findings we also discuss the origin of the studied species and the importance of the pherotype phenomenon as a tool with which to study genetic relationships between congener scale insects. PMID:24523894

  8. Evidence for Gene Flow between Two Sympatric Mealybug Species (Insecta; Coccoidea; Pseudococcidae)

    PubMed Central

    Kol-Maimon, Hofit; Ghanim, Murad; Franco, José Carlos; Mendel, Zvi

    2014-01-01

    Occurrence of inter-species hybrids in natural populations might be evidence of gene flow between species. In the present study we found evidence of gene flow between two sympatric, genetically related scale insect species – the citrus mealybug Planococcus citri (Risso) and the vine mealybug Planococcus ficus (Signoret). These species can be distinguished by morphological, behavioral, and molecular traits. We employed the sex pheromones of the two respective species to study their different patterns of male attraction. We also used nuclear ITS2 (internal transcribed spacer 2) and mitochondrial COI (Cytochrome c oxidase sub unit 1) DNA sequences to characterize populations of the two species, in order to demonstrate the outcome of a possible gene flow between feral populations of the two species. Our results showed attraction to P. ficus pheromones of all tested populations of P. citri males but not vice versa. Furthermore, ITS2 sequences revealed the presence of ‘hybrid females’ among P. citri populations but not among those of P. ficus. ‘hybrid females’ from P. citri populations identified as P. citri females according to COI sequences. We offer two hypotheses for these results. 1) The occurrence of phenotypic and genotypic traits of P. ficus in P. citri populations may be attributed to both ancient and contemporary gene flow between their populations; and 2) we cannot rule out that an ancient sympatric speciation by which P. ficus emerged from P. citri might have led to the present situation of shared traits between these species. In light of these findings we also discuss the origin of the studied species and the importance of the pherotype phenomenon as a tool with which to study genetic relationships between congener scale insects. PMID:24523894

  9. SPECIATE 4.3: Addendum to SPECIATE 4.2--Speciation database development documentation

    EPA Science Inventory

    SPECIATE is the U.S. Environmental Protection Agency's (EPA) repository of volatile organic gas and particulate matter (PM) speciation profiles of air pollution sources. Among the many uses of speciation data, these source profiles are used to: (1) create speciated emissions inve...

  10. Mitonuclear Ecology

    PubMed Central

    Hill, Geoffrey E.

    2015-01-01

    Eukaryotes were born of a chimeric union between two prokaryotes—the progenitors of the mitochondrial and nuclear genomes. Early in eukaryote evolution, most mitochondrial genes were lost or transferred to the nucleus, but a core set of genes that code exclusively for products associated with the electron transport system remained in the mitochondrion. The products of these mitochondrial genes work in intimate association with the products of nuclear genes to enable oxidative phosphorylation and core energy production. The need for coadaptation, the challenge of cotransmission, and the possibility of genomic conflict between mitochondrial and nuclear genes have profound consequences for the ecology and evolution of eukaryotic life. An emerging interdisciplinary field that I call “mitonuclear ecology” is reassessing core concepts in evolutionary ecology including sexual reproduction, two sexes, sexual selection, adaptation, and speciation in light of the interactions of mitochondrial and nuclear genomes. PMID:25931514

  11. Concerted genetic, morphological and ecological diversification in Nacella limpets in the Magellanic Province.

    PubMed

    González-Wevar, C A; Nakano, T; Cañete, J I; Poulin, E

    2011-05-01

    Common inhabitants of Antarctic and Subantarctic rocky shores, the limpet genus Nacella, includes 15 nominal species distributed in different provinces of the Southern Ocean. The Magellanic Province represents the area with the highest diversity of the genus. Phylogenetic reconstructions showed an absence of reciprocal monophyly and high levels of genetic identity among nominal species in this Province and therefore imply a recent diversification in southern South America. Because most of these taxa coexist along their distribution range with clear differences in their habitat preferences, Nacella is a suitable model to explore diversification mechanisms in an area highly affected by recurrent Pleistocene continental ice cap advances and retreats. Here, we present genetic and morphological comparisons among sympatric Magellanic nominal species of Nacella. We amplified a fragment of the COI gene for 208 individuals belonging to seven sympatric nominal species and performed geometric morphometric analyses of their shells. We detected a complete congruence between genetic and morphological results, leading us to suggest four groups of Nacella among seven analysed nominal species. Congruently, each of these groups was related to different habitat preferences such as bathymetric range and substrate type. A plausible explanation for these results includes an ecologically based allopatric speciation process in Nacella. Major climatic changes during the Plio-Pleistocene glacial cycles may have enhanced differentiation processes. Finally, our results indicate that the systematics of the group requires a deep revision to re-evaluate the taxonomy of Nacella and to further understand the Pleistocene legacy of the glacial cycles in the southern tip of South America. PMID:21418364

  12. Can Newts Cope with the Heat? Disparate Thermoregulatory Strategies of Two Sympatric Species in Water

    PubMed Central

    Balogová, Monika; Gvoždík, Lumír

    2015-01-01

    Many ectotherms effectively reduce their exposure to low or high environmental temperatures using behavioral thermoregulation. In terrestrial ectotherms, thermoregulatory strategies range from accurate thermoregulation to thermoconformity according to the costs and limits of thermoregulation, while in aquatic taxa the quantification of behavioral thermoregulation have received limited attention. We examined thermoregulation in two sympatric newt species, Ichthyosaura alpestris and Lissotriton vulgaris, exposed to elevated water temperatures under semi-natural conditions. According to a recent theory, we predicted that species for which elevated water temperatures pose a lower thermal quality habitat, would thermoregulate more effectively than species in thermally benign conditions. In the laboratory thermal gradient, L. vulgaris maintained higher body temperatures than I. alpestris. Semi-natural thermal conditions provided better thermal quality of habitat for L. vulgaris than for I. alpestris. Thermoregulatory indices indicated that I. alpestris actively thermoregulated its body temperature, whereas L. vulgaris remained passive to the thermal heterogeneity of aquatic environment. In the face of elevated water temperatures, sympatric newt species employed disparate thermoregulatory strategies according to the species-specific quality of the thermal habitat. Both strategies reduced newt exposure to suboptimal water temperatures with the same accuracy but with or without the costs of thermoregulation. The quantification of behavioral thermoregulation proves to be an important conceptual and methodological tool for thermal ecology studies not only in terrestrial but also in aquatic ectotherms. PMID:25993482

  13. Can newts cope with the heat? Disparate thermoregulatory strategies of two sympatric species in water.

    PubMed

    Balogová, Monika; Gvoždík, Lumír

    2015-01-01

    Many ectotherms effectively reduce their exposure to low or high environmental temperatures using behavioral thermoregulation. In terrestrial ectotherms, thermoregulatory strategies range from accurate thermoregulation to thermoconformity according to the costs and limits of thermoregulation, while in aquatic taxa the quantification of behavioral thermoregulation have received limited attention. We examined thermoregulation in two sympatric newt species, Ichthyosaura alpestris and Lissotriton vulgaris, exposed to elevated water temperatures under semi-natural conditions. According to a recent theory, we predicted that species for which elevated water temperatures pose a lower thermal quality habitat, would thermoregulate more effectively than species in thermally benign conditions. In the laboratory thermal gradient, L. vulgaris maintained higher body temperatures than I. alpestris. Semi-natural thermal conditions provided better thermal quality of habitat for L. vulgaris than for I. alpestris. Thermoregulatory indices indicated that I. alpestris actively thermoregulated its body temperature, whereas L. vulgaris remained passive to the thermal heterogeneity of aquatic environment. In the face of elevated water temperatures, sympatric newt species employed disparate thermoregulatory strategies according to the species-specific quality of the thermal habitat. Both strategies reduced newt exposure to suboptimal water temperatures with the same accuracy but with or without the costs of thermoregulation. The quantification of behavioral thermoregulation proves to be an important conceptual and methodological tool for thermal ecology studies not only in terrestrial but also in aquatic ectotherms. PMID:25993482

  14. Comparative phylogeography of two sympatric beeches in subtropical China: Species-specific geographic mosaic of lineages.

    PubMed

    Zhang, Zhi-Yong; Wu, Rong; Wang, Qun; Zhang, Zhi-Rong; López-Pujol, Jordi; Fan, Deng-Mei; Li, De-Zhu

    2013-11-01

    In subtropical China, large-scale phylogeographic comparisons among multiple sympatric plants with similar ecological preferences are scarce, making generalizations about common response to historical events necessarily tentative. A phylogeographic comparison of two sympatric Chinese beeches (Fagus lucida and F. longipetiolata, 21 and 28 populations, respectively) was conducted to test whether they have responded to historical events in a concerted fashion and to determine whether their phylogeographic structure is exclusively due to Quaternary events or it is also associated with pre-Quaternary events. Twenty-three haplotypes were recovered for F. lucida and F. longipetiolata (14 each one and five shared). Both species exhibited a species-specific mosaic distribution of haplotypes, with many of them being range-restricted and even private to populations. The two beeches had comparable total haplotype diversity but F. lucida had much higher within-population diversity than F. longipetiolata. Molecular dating showed that the time to most recent common ancestor of all haplotypes was 6.36 Ma, with most haplotypes differentiating during the Quaternary. [Correction added on 14 October 2013, after first online publication: the timeunit has been corrected to '6.36'.] Our results support a late Miocene origin and southwards colonization of Chinese beeches when the aridity in Central Asia intensified and the monsoon climate began to dominate the East Asia. During the Quaternary, long-term isolation in subtropical mountains of China coupled with limited gene flow would have lead to the current species-specific mosaic distribution of lineages. PMID:24340187

  15. Interploidy hybridization in sympatric zones: the formation of Epidendrum fulgens × E. puniceoluteum hybrids (Epidendroideae, Orchidaceae)

    PubMed Central

    Moraes, Ana P; Chinaglia, Mariana; Palma-Silva, Clarisse; Pinheiro, Fábio

    2013-01-01

    Interspecific hybridization is a primary cause of extensive morphological and chromosomal variation and plays an important role in plant species diversification. However, the role of interploidal hybridization in the formation of hybrid swarms is less clear. Epidendrum encompasses wide variation in chromosome number and lacks strong premating barriers, making the genus a good model for clarifying the role of chromosomes in postzygotic barriers in interploidal hybrids. In this sense, hybrids from the interploidal sympatric zone between E. fulgens (2n = 2x = 24) and E. puniceoluteum (2n = 4x = 56) were analyzed using cytogenetic techniques to elucidate the formation and establishment of interploidal hybrids. Hybrids were not a uniform group: two chromosome numbers were observed, with the variation being a consequence of severe hybrid meiotic abnormalities and backcrossing with E. puniceoluteum. The hybrids were triploids (2n = 3x = 38 and 40) and despite the occurrence of enormous meiotic problems associated with triploidy, the hybrids were able to backcross, producing successful hybrid individuals with broad ecological distributions. In spite of the nonpolyploidization of the hybrid, its formation is a long-term evolutionary process rather than a product of a recent disturbance, and considering other sympatric zones in Epidendrum, these events could be recurrent. PMID:24198942

  16. DNA metabarcoding diet analysis for species with parapatric vs sympatric distribution: a case study on subterranean rodents

    PubMed Central

    Lopes, C M; De Barba, M; Boyer, F; Mercier, C; da Silva Filho, P J S; Heidtmann, L M; Galiano, D; Kubiak, B B; Langone, P; Garcias, F M; Gielly, L; Coissac, E; de Freitas, T R O; Taberlet, P

    2015-01-01

    Closely related sympatric species commonly develop different ecological strategies to avoid competition. Ctenomys minutus and C. flamarioni are subterranean rodents parapatrically distributed in the southern Brazilian coastal plain, showing a narrow sympatric zone. To gain understanding on food preferences and possible competition for food resources, we evaluated their diet composition performing DNA metabarcoding analyzes of 67 C. minutus and 100 C. flamarioni scat samples, collected along the species geographical ranges. Thirteen plant families, mainly represented by Poaceae, Araliaceae, Asteraceae and Fabaceae, were identified in the diet of C. minutus. For C. flamarioni, 10 families were recovered, with a predominance of Poaceae, Araliaceae and Asteraceae. A significant correlation between diet composition and geographical distance was detected in C. minutus, whereas the diet of C. flamarioni was quite homogeneous throughout its geographical distribution. No significant differences were observed between males and females of each species. However, differences in diet composition between species were evident according to multivariate analysis. Our results suggest some level of diet partitioning between C. flamarioni and C. minutus in the sympatric region. While the first species is more specialized on few plant items, the second showed a more varied and heterogeneous diet pattern among individuals. These differences might have been developed to avoid competition in the region of co-occurrence. Resource availability in the environment also seems to influence food choices. Our data indicate that C. minutus and C. flamarioni are generalist species, but that some preference for Poaceae, Asteraceae and Araliaceae families can be suggested for both rodents. PMID:25649502

  17. Male competition fitness landscapes predict both forward and reverse speciation.

    PubMed

    Keagy, Jason; Lettieri, Liliana; Boughman, Janette W

    2016-01-01

    Speciation is facilitated when selection generates a rugged fitness landscape such that populations occupy different peaks separated by valleys. Competition for food resources is a strong ecological force that can generate such divergent selection. However, it is unclear whether intrasexual competition over resources that provide mating opportunities can generate rugged fitness landscapes that foster speciation. Here we use highly variable male F2 hybrids of benthic and limnetic threespine sticklebacks, Gasterosteus aculeatus Linnaeus, 1758, to quantify the male competition fitness landscape. We find that disruptive sexual selection generates two fitness peaks corresponding closely to the male phenotypes of the two parental species, favouring divergence. Most surprisingly, an additional region of high fitness favours novel hybrid phenotypes that correspond to those observed in a recent case of reverse speciation after anthropogenic disturbance. Our results reveal that sexual selection through male competition plays an integral role in both forward and reverse speciation. PMID:26612568

  18. Mutation-order divergence by sexual selection: diversification of sexual signals in similar environments as a first step in speciation.

    PubMed

    Mendelson, Tamra C; Martin, Michael D; Flaxman, Samuel M

    2014-09-01

    The origin of species remains a central question, and recent research focuses on the role of ecological differences in promoting speciation. Ecological differences create opportunities for divergent selection (i.e. 'ecological' speciation), a Darwinian hypothesis that hardly requires justification. In contrast, 'mutation-order' speciation proposes that, instead of adapting to different environments, populations find different ways to adapt to similar environments, implying that speciation does not require ecological differences. This distinction is critical as it provides an alternative hypothesis to the prevailing view that ecological differences drive speciation. Speciation by sexual selection lies at the centre of debates about the importance of ecological differences in promoting speciation; here, we present verbal and mathematical models of mutation-order divergence by sexual selection. We develop three general cases and provide a two-locus population genetic model for each. Results indicate that alternative secondary sexual traits can fix in populations that initially experience similar natural and sexual selection and that divergent traits and preferences can remain stable in the face of low gene flow. This stable divergence can facilitate subsequent divergence that completes or reinforces speciation. We argue that a mutation-order process could explain widespread diversity in secondary sexual traits among closely related, allopatric species. PMID:24943881

  19. Speciation driven by hybridization and chromosomal plasticity in a wild yeast.

    PubMed

    Leducq, Jean-Baptiste; Nielly-Thibault, Lou; Charron, Guillaume; Eberlein, Chris; Verta, Jukka-Pekka; Samani, Pedram; Sylvester, Kayla; Hittinger, Chris Todd; Bell, Graham; Landry, Christian R

    2016-01-01

    Hybridization is recognized as a powerful mechanism of speciation and a driving force in generating biodiversity. However, only few multicellular species, limited to a handful of plants and animals, have been shown to fulfil all the criteria of homoploid hybrid speciation. This lack of evidence could lead to the interpretation that speciation by hybridization has a limited role in eukaryotes, particularly in single-celled organisms. Laboratory experiments have revealed that fungi such as budding yeasts can rapidly develop reproductive isolation and novel phenotypes through hybridization, showing that in principle homoploid speciation could occur in nature. Here, we report a case of homoploid hybrid speciation in natural populations of the budding yeast Saccharomyces paradoxus inhabiting the North American forests. We show that the rapid evolution of chromosome architecture and an ecological context that led to secondary contact between nascent species drove the formation of an incipient hybrid species with a potentially unique ecological niche. PMID:27571751

  20. Contrasting phylogeographic histories between broadly sympatric topminnows in the Fundulus notatus species complex.

    PubMed

    Duvernell, David D; Meier, Stephanie L; Schaefer, Jacob F; Kreiser, Brian R

    2013-12-01

    Sympatrically distributed closely related species provide opportunities for studying evolutionary patterns of diversification. Such studies must account for historical contingencies in interpreting contemporary patterns of variation. Topminnows in the Fundulus notatus species complex are distributed sympatrically across much of the southern and Midwestern United States. Throughout most of their ranges F. olivaceus is often found in headwater stream habitats, and F. notatus is more typically distributed along the margins of larger river habitats. However, in some drainages, ecological associations of the respective species are reversed, with F. notatus populations isolated in headwater streams and F. olivaceus in downstream river habitats. Phylogeographic analyses of AFLP marker and multi-locus sequence data detected historical isolation in F. notatus consistent with pre-Pleistocene drainage patterns. Four F. notatus clades corresponded to (i) the Western Gulf Slope, (ii) the southwestern Ouachita Highlands, (iii) the Mobile Basin, and (iv) central Coastal Plain and Mississippi River Basin. In contrast, a relative lack of range-wide geographic structure in F. olivaceus is consistent with recent range expansion over much of the same geographic area. The southwestern Ouachita Highlands and Mobile Basin F. notatus clades corresponded to regions where ecological associations between the two species are reversed, providing evidence of the independent evolution of variation in contemporary habitat associations. Fundulus olivaceus from several drainages demonstrated introgression of mitochondrial DNA from F. notatus, but none of the sites in this study included individuals with hybrid ancestry in their nuclear genome. Phylogenetic analyses that included only nuclear loci supported the reciprocal monophyly of F. notatus, F. olivaceus and a third narrowly endemic species, Fundulus euryzonus, and supported a sister relationship between F. olivaceus and F. euryzonus. PMID

  1. Choice matters: incipient speciation in Gyrodactylus corydori (Monogenoidea: Gyrodactylidae).

    PubMed

    Bueno-Silva, Marlus; Boeger, Walter A; Pie, Marcio R

    2011-05-01

    We investigated how Gyrodactylus corydoriBueno-Silva and Boeger, 2009 exploits two sympatric host species, Corydoras paleatus (Jenyns, 1842) and Corydoras ehrhardti Steindachner, 1910. Specimens of G. corydori were collected from the Piraquara and Miringuava Rivers, State of Paraná, Brazil, between 2005 and 2006. A total of 167 parasites was measured from both host species. Nine morphometric features of the haptoral sclerites were measured and analyzed by discriminant analysis, cluster analysis and multivariate analysis of variance. A fragment of the mitochondrial cytochrome oxidase I gene (COI) (∼740 bp) and the rDNA internal transcribed spacers (ITS) (∼1200 bp) of G. corydori were sequenced. Bayesian and parsimony analyses of COI recognized two genetically structured clades of G. corydori, which corresponded closely with the two species of Corydoras. Twenty-eight haplotypes were detected (18 were exclusive to C. ehrhardti and seven were exclusive to C. paleatus). The same general pattern between parasites and host species was observed in the morphometric analyses. Nevertheless, poor correlation of genetic and morphometric variation strongly supports the plastic nature of the morphological variation of haptoral sclerites. The existence of two clades with limited gene flow would suggest that G. corydori already represents two cryptic species. However, the morphometric and molecular data showed that there is insufficient evidence to support two valid species. The low COI (0.1-6.2%) and ITS (0.09-3.5%) divergence within G. corydori suggest a recent separation of the lineages between distinct host species (less than 1 million years). As the hypothesis of secondary contact of the parasite demographic history was rejected, our results point to the possibility of sympatric incipient ongoing speciation of G. corydori to form distinct parasite lineages adapted to C. ehrhardti and C. paleatus. This may be a common event within the Gyrodactylidae, adding a yet

  2. Role of demographic stochasticity in a speciation model with sexual reproduction

    NASA Astrophysics Data System (ADS)

    Lafuerza, Luis F.; McKane, Alan J.

    2016-03-01

    Recent theoretical studies have shown that demographic stochasticity can greatly increase the tendency of asexually reproducing phenotypically diverse organisms to spontaneously evolve into localized clusters, suggesting a simple mechanism for sympatric speciation. Here we study the role of demographic stochasticity in a model of competing organisms subject to assortative mating. We find that in models with sexual reproduction, noise can also lead to the formation of phenotypic clusters in parameter ranges where deterministic models would lead to a homogeneous distribution. In some cases, noise can have a sizable effect, rendering the deterministic modeling insufficient to understand the phenotypic distribution.

  3. Sympatric divergence and clinal variation in multiple coloration traits of Ficedula flycatchers.

    PubMed

    Laaksonen, T; Sirkiä, P M; Calhim, S; Brommer, J E; Leskinen, P K; Primmer, C R; Adamík, P; Artemyev, A V; Belskii, E; Both, C; Bureš, S; Burgess, M D; Doligez, B; Forsman, J T; Grinkov, V; Hoffmann, U; Ivankina, E; Král, M; Krams, I; Lampe, H M; Moreno, J; Mägi, M; Nord, A; Potti, J; Ravussin, P-A; Sokolov, L

    2015-04-01

    Geographic variation in phenotypes plays a key role in fundamental evolutionary processes such as local adaptation, population differentiation and speciation, but the selective forces behind it are rarely known. We found support for the hypothesis that geographic variation in plumage traits of the pied flycatcher Ficedula hypoleuca is explained by character displacement with the collared flycatcher Ficedula albicollis in the contact zone. The plumage traits of the pied flycatcher differed strongly from the more conspicuous collared flycatcher in a sympatric area but increased in conspicuousness with increasing distance to there. Phenotypic differentiation (PST ) was higher than that in neutral genetic markers (FST ), and the effect of geographic distance remained when statistically controlling for neutral genetic differentiation. This suggests that a cline created by character displacement and gene flow explains phenotypic variation across the distribution of this species. The different plumage traits of the pied flycatcher are strongly to moderately correlated, indicating that they evolve non-independently from each other. The flycatchers provide an example of plumage patterns diverging in two species that differ in several aspects of appearance. The divergence in sympatry and convergence in allopatry in these birds provide a possibility to study the evolutionary mechanisms behind the highly divergent avian plumage patterns. PMID:25683091

  4. Resolving lost herbivore community structure using coprolites of four sympatric moa species (Aves: Dinornithiformes)

    PubMed Central

    Wood, Jamie R.; Wilmshurst, Janet M.; Richardson, Sarah J.; Rawlence, Nicolas J.; Wagstaff, Steven J.; Worthy, Trevor H.; Cooper, Alan

    2013-01-01

    Knowledge of extinct herbivore community structuring is essential for assessing the wider ecological impacts of Quaternary extinctions and determining appropriate taxon substitutes for rewilding. Here, we demonstrate the potential for coprolite studies to progress beyond single-species diet reconstructions to resolving community-level detail. The moa (Aves: Dinornithiformes) of New Zealand are an intensively studied group of nine extinct herbivore species, yet many details of their diets and community structuring remain unresolved. We provide unique insights into these aspects of moa biology through analyses of a multispecies coprolite assemblage from a rock overhang in a montane river valley in southern New Zealand. Using ancient DNA (aDNA), we identified 51 coprolites, which included specimens from four sympatric moa species. Pollen, plant macrofossils, and plant aDNA from the coprolites chronicle the diets and habitat preferences of these large avian herbivores during the 400 y before their extinction (∼1450 AD). We use the coprolite data to develop a paleoecological niche model in which moa species were partitioned based on both habitat (forest and valley-floor herbfield) and dietary preferences, the latter reflecting allometric relationships between body size, digestive efficiency, and nutritional requirements. Broad ecological niches occupied by South Island giant moa (Dinornis robustus) and upland moa (Megalapteryx didinus) may reflect sexual segregation and seasonal variation in habitat use, respectively. Our results show that moa lack extant ecological analogs, and their extinction represents an irreplaceable loss of function from New Zealand’s terrestrial ecosystems. PMID:24082104

  5. Resolving lost herbivore community structure using coprolites of four sympatric moa species (Aves: Dinornithiformes).

    PubMed

    Wood, Jamie R; Wilmshurst, Janet M; Richardson, Sarah J; Rawlence, Nicolas J; Wagstaff, Steven J; Worthy, Trevor H; Cooper, Alan

    2013-10-15

    Knowledge of extinct herbivore community structuring is essential for assessing the wider ecological impacts of Quaternary extinctions and determining appropriate taxon substitutes for rewilding. Here, we demonstrate the potential for coprolite studies to progress beyond single-species diet reconstructions to resolving community-level detail. The moa (Aves: Dinornithiformes) of New Zealand are an intensively studied group of nine extinct herbivore species, yet many details of their diets and community structuring remain unresolved. We provide unique insights into these aspects of moa biology through analyses of a multispecies coprolite assemblage from a rock overhang in a montane river valley in southern New Zealand. Using ancient DNA (aDNA), we identified 51 coprolites, which included specimens from four sympatric moa species. Pollen, plant macrofossils, and plant aDNA from the coprolites chronicle the diets and habitat preferences of these large avian herbivores during the 400 y before their extinction (∼1450 AD). We use the coprolite data to develop a paleoecological niche model in which moa species were partitioned based on both habitat (forest and valley-floor herbfield) and dietary preferences, the latter reflecting allometric relationships between body size, digestive efficiency, and nutritional requirements. Broad ecological niches occupied by South Island giant moa (Dinornis robustus) and upland moa (Megalapteryx didinus) may reflect sexual segregation and seasonal variation in habitat use, respectively. Our results show that moa lack extant ecological analogs, and their extinction represents an irreplaceable loss of function from New Zealand's terrestrial ecosystems. PMID:24082104

  6. Speciation in birds: Genes, geography, and sexual selection

    PubMed Central

    Edwards, Scott V.; Kingan, Sarah B.; Calkins, Jennifer D.; Balakrishnan, Christopher N.; Jennings, W. Bryan; Swanson, Willie J.; Sorenson, Michael D.

    2005-01-01

    Molecular studies of speciation in birds over the last three decades have been dominated by a focus on the geography, ecology, and timing of speciation, a tradition traceable to Mayr's Systematics and the Origin of Species. However, in the recent years, interest in the behavioral and molecular mechanisms of speciation in birds has increased, building in part on the older traditions and observations from domesticated species. The result is that many of the same mechanisms proffered for model lineages such as Drosophila—mechanisms such as genetic incompatibilities, reinforcement, and sexual selection—are now being seriously entertained for birds, albeit with much lower resolution. The recent completion of a draft sequence of the chicken genome, and an abundance of single-nucleotide polymorphisms on the autosomes and sex chromosomes, will dramatically accelerate research on the molecular mechanisms of avian speciation over the next few years. The challenge for ornithologists is now to inform well studied examples of speciation in nature with increased molecular resolution—to clone speciation genes if they exist—and thereby evaluate the relative roles of extrinsic, intrinsic, deterministic, and stochastic causes for avian diversification. PMID:15851678

  7. Microbial ecology of an Antarctic hypersaline lake: genomic assessment of ecophysiology among dominant haloarchaea

    PubMed Central

    Williams, Timothy J; Allen, Michelle A; DeMaere, Matthew Z; Kyrpides, Nikos C; Tringe, Susannah G; Woyke, Tanja; Cavicchioli, Ricardo

    2014-01-01

    Deep Lake in Antarctica is a cold, hypersaline system where four types of haloarchaea representing distinct genera comprise >70% of the lake community: strain tADL ∼44%, strain DL31 ∼18%, Halorubrum lacusprofundi ∼10% and strain DL1 ∼0.3%. By performing comparative genomics, growth substrate assays, and analyses of distribution by lake depth, size partitioning and lake nutrient composition, we were able to infer important metabolic traits and ecophysiological characteristics of the four Antarctic haloarchaea that contribute to their hierarchical persistence and coexistence in Deep Lake. tADL is characterized by a capacity for motility via flagella (archaella) and gas vesicles, a highly saccharolytic metabolism, a preference for glycerol, and photoheterotrophic growth. In contrast, DL31 has a metabolism specialized in processing proteins and peptides, and appears to prefer an association with particulate organic matter, while lacking the genomic potential for motility. H. lacusprofundi is the least specialized, displaying a genomic potential for the utilization of diverse organic substrates. The least abundant species, DL1, is characterized by a preference for catabolism of amino acids, and is the only one species that lacks genes needed for glycerol degradation. Despite the four haloarchaea being distributed throughout the water column, our analyses describe a range of distinctive features, including preferences for substrates that are indicative of ecological niche partitioning. The individual characteristics could be responsible for shaping the composition of the haloarchaeal community throughout the lake by enabling selection of ecotypes and maintaining sympatric speciation. PMID:24553470

  8. ORGANIC SPECIATION SAMPLING ARTIFACTS

    EPA Science Inventory

    Sampling artifacts for molecular markers from organic speciation of particulate matter were investigated by analyzing forty-one samples collected in Philadelphia as a part of the Northeast Oxidant and Particulate Study (NEOPS). Samples were collected using a high volume sampler ...

  9. Hybrid speciation and independent evolution in lineages of alpine butterflies.

    PubMed

    Nice, Chris C; Gompert, Zachariah; Fordyce, James A; Forister, Matthew L; Lucas, Lauren K; Buerkle, C Alex

    2013-04-01

    The power of hybridization between species to generate variation and fuel adaptation is poorly understood despite long-standing interest. There is, however, increasing evidence that hybridization often generates biodiversity, including via hybrid speciation. We tested the hypothesis of hybrid speciation in butterflies occupying extreme, high-altitude habitats in four mountain ranges in western North America with an explicit, probabilistic model, and genome-wide DNA sequence data. Using this approach, in concert with ecological experiments and observations and morphological data, we document three lineages of hybrid origin. These lineages have different genome admixture proportions and distinctive trait combinations that suggest unique and independent evolutionary histories. PMID:23550755

  10. Parallel speciation in Astyanax cave fish (Teleostei) in Northern Mexico.

    PubMed

    Strecker, Ulrike; Hausdorf, Bernhard; Wilkens, Horst

    2012-01-01

    We investigated differentiation processes in the Neotropical fish Astyanax that represents a model system for examining adaptation to caves, including regressive evolution. In particular, we analyzed microsatellite and mitochondrial data of seven cave and seven surface populations from Mexico to test whether the evolution of the cave fish represents a case of parallel evolution. Our data revealed that Astyanax invaded northern Mexico across the Trans-Mexican Volcanic Belt at least three times and that populations of all three invasions adapted to subterranean habitats. Significant differentiation was found between the cave and surface populations. We did not observe gene flow between the strongly eye and pigment reduced old cave populations (Sabinos, Tinaja, Pachon) and the surface fish, even when syntopically occurring like in Yerbaniz cave. Little gene flow, if any, was found between cave populations, which are variable in eye and pigmentation (Micos, Chica, Caballo Moro caves), and surface fish. This suggests that the variability is due to their more recent origin rather than to hybridization. Finally, admixture of the young Chica cave fish population with nuclear markers from older cave fish demonstrates that gene flow between populations that independently colonized caves occurs. Thus, all criteria of parallel speciation are fulfilled. Moreover, the microsatellite data provide evidence that two co-occurring groups with small sunken eyes and externally visible eyes, respectively, differentiated within the partly lightened Caballo Moro karst window cave and might represent an example for incipient sympatric speciation. PMID:21963344

  11. Dietary response of sympatric deer to fire using stable isotope analysis of liver tissue

    USGS Publications Warehouse

    Walter, W. David; Zimmerman, T.J.; Leslie, David M., Jr.; Jenks, J.A.

    2009-01-01

    Carbon (??13C) and nitrogen (??15N) isotopes in biological samples from large herbivores identify photosynthetic pathways (C3 vs. C4) of plants they consumed and can elucidate potential nutritional characteristics of dietary selection. Because large herbivores consume a diversity of forage types, ??13C and ??15N in their tissue can index ingested and assimilated diets through time. We assessed ??13C and ??15N in metabolically active liver tissue of sympatric mule deer (Odocoileus hemionus) and white-tailed deer (O. virginianus) to identify dietary disparity resulting from use of burned and unburned areas in a largely forested landscape. Interspecific variation in dietary disparity of deer was documented 2-3 years post-fire in response to lag-time effects of vegetative response to burning and seasonal (i.e., summer, winter) differences in forage type. Liver ??13C for mule deer were lower during winter and higher during summer 2 years post-fire on burned habitat compared to unburned habitat suggesting different forages were consumed by mule deer in response to fire. Liver ??15N for both species were higher on burned than unburned habitat during winter and summer suggesting deer consumed more nutritious forage on burned habitat during both seasons 2 and 3 years post-fire. Unlike traditional methods of dietary assessment that do not measure uptake of carbon and nitrogen from dietary components, analyses of stable isotopes in liver or similar tissue elucidated ??13C and ??15N assimilation from seasonal dietary components and resulting differences in the foraging ecology of sympatric species in response to fire.

  12. Darwin's finches and their diet niches: the sympatric coexistence of imperfect generalists.

    PubMed

    De León, L F; Podos, J; Gardezi, T; Herrel, A; Hendry, A P

    2014-06-01

    Adaptive radiation can be strongly influenced by interspecific competition for resources, which can lead to diverse outcomes ranging from competitive exclusion to character displacement. In each case, sympatric species are expected to evolve into distinct ecological niches, such as different food types, yet this expectation is not always met when such species are examined in nature. The most common hypotheses to account for the coexistence of species with substantial diet overlap rest on temporal variation in niches (often diets). Yet spatial variation in niche overlap might also be important, pointing to the need for spatiotemporal analyses of diet and diet overlap between closely related species persisting in sympatry. We here perform such an analysis by characterizing the diets of, and diet overlap among, four sympatric Darwin's ground finch species at three sites and over 5 years on a single Galápagos island (Santa Cruz). We find that the different species have broadly similar and overlapping diets - they are to some extent generalists and opportunists - yet we also find that each species retains some 'private' resources for which their morphologies are best suited. Importantly, use of these private resources increased considerably, and diet overlap decreased accordingly, when the availability of preferred shared foods, such as arthropods, was reduced during drought conditions. Spatial variation in food resources was also important. These results together suggest that the ground finches are 'imperfect generalists' that use overlapping resources under benign conditions (in space or time), but then retreat to resources for which they are best adapted during periods of food limitation. These conditions likely promote local and regional coexistence. PMID:24750315

  13. Adaptive divergence with gene flow in incipient speciation of Miscanthus floridulus/sinensis complex (Poaceae).

    PubMed

    Huang, Chao-Li; Ho, Chuan-Wen; Chiang, Yu-Chung; Shigemoto, Yasumasa; Hsu, Tsai-Wen; Hwang, Chi-Chuan; Ge, Xue-Jun; Chen, Charles; Wu, Tai-Han; Chou, Chang-Hung; Huang, Hao-Jen; Gojobori, Takashi; Osada, Naoki; Chiang, Tzen-Yuh

    2014-12-01

    Young incipient species provide ideal materials for untangling the process of ecological speciation in the presence of gene flow. The Miscanthus floridulus/sinensis complex exhibits diverse phenotypic and ecological differences despite recent divergence (approximately 1.59 million years ago). To elucidate the process of genetic differentiation during early stages of ecological speciation, we analyzed genomic divergence in the Miscanthus complex using 72 randomly selected genes from a newly assembled transcriptome. In this study, rampant gene flow was detected between species, estimated as M = 3.36 × 10(-9) to 1.20 × 10(-6) , resulting in contradicting phylogenies across loci. Nevertheless, beast analyses revealed the species identity and the effects of extrinsic cohesive forces that counteracted the non-stop introgression. As expected, early in speciation with gene flow, only 3-13 loci were highly diverged; two to five outliers (approximately 2.78-6.94% of the genome) were characterized by strong linkage disequilibrium, and asymmetrically distributed among ecotypes, indicating footprints of diversifying selection. In conclusion, ecological speciation of incipient species of Miscanthus probably followed the parapatric model, whereas allopatric speciation cannot be completely ruled out, especially between the geographically isolated northern and southern M. sinensis, for which no significant gene flow across oceanic barriers was detected. Divergence between local ecotypes in early-stage speciation began at a few genomic regions under the influence of natural selection and divergence hitchhiking that overcame gene flow. PMID:25237766

  14. The evolutionary genetics of speciation.

    PubMed Central

    Coyne, J A; Orr, H A

    1998-01-01

    The last decade has brought renewed interest in the genetics of speciation, yielding a number of new models and empirical results. Defining speciation as 'the origin of reproductive isolation between two taxa', we review recent theoretical studies and relevant data, emphasizing the regular patterns seen among genetic analyses. Finally, we point out some important and tractable questions about speciation that have been neglected. PMID:9533126

  15. Socially segregated, sympatric sperm whale clans in the Atlantic Ocean.

    PubMed

    Gero, Shane; Bøttcher, Anne; Whitehead, Hal; Madsen, Peter Teglberg

    2016-06-01

    Sperm whales (Physeter macrocephalus) are unusual in that there is good evidence for sympatric populations with distinct culturally determined behaviour, including potential acoustic markers of the population division. In the Pacific, socially segregated, vocal clans with distinct dialects coexist; by contrast, geographical variation in vocal repertoire in the Atlantic has been attributed to drift. We examine networks of acoustic repertoire similarity and social interactions for 11 social units in the Eastern Caribbean. We find the presence of two socially segregated, sympatric vocal clans whose dialects differ significantly both in terms of categorical coda types produced by each clan (Mantel test between clans: matrix correlation = 0.256; p ≤ 0.001) and when using classification-free similarity which ignores defined types (Mantel test between clans: matrix correlation = 0.180; p ≤ 0.001). The more common of the two clans makes a characteristic 1 + 1 + 3 coda, while the other less often sighted clan makes predominantly regular codas. Units were only observed associating with other units within their vocal clan. This study demonstrates that sympatric vocal clans do exist in the Atlantic, that they define a higher order level of social organization as they do in the Pacific, and suggests that cultural identity at the clan level is probably important in this species worldwide. PMID:27429766

  16. Socially segregated, sympatric sperm whale clans in the Atlantic Ocean

    PubMed Central

    Bøttcher, Anne; Whitehead, Hal

    2016-01-01

    Sperm whales (Physeter macrocephalus) are unusual in that there is good evidence for sympatric populations with distinct culturally determined behaviour, including potential acoustic markers of the population division. In the Pacific, socially segregated, vocal clans with distinct dialects coexist; by contrast, geographical variation in vocal repertoire in the Atlantic has been attributed to drift. We examine networks of acoustic repertoire similarity and social interactions for 11 social units in the Eastern Caribbean. We find the presence of two socially segregated, sympatric vocal clans whose dialects differ significantly both in terms of categorical coda types produced by each clan (Mantel test between clans: matrix correlation = 0.256; p ≤ 0.001) and when using classification-free similarity which ignores defined types (Mantel test between clans: matrix correlation = 0.180; p ≤ 0.001). The more common of the two clans makes a characteristic 1 + 1 + 3 coda, while the other less often sighted clan makes predominantly regular codas. Units were only observed associating with other units within their vocal clan. This study demonstrates that sympatric vocal clans do exist in the Atlantic, that they define a higher order level of social organization as they do in the Pacific, and suggests that cultural identity at the clan level is probably important in this species worldwide. PMID:27429766

  17. Sympatric Masticophis flagellum and Coluber constrictor select vertebrate prey at different levels of taxonomy

    USGS Publications Warehouse

    Halstead, B.J.; Mushinsky, H.R.; McCoy, E.D.

    2008-01-01

    Masticophis flagellum (Coachwhip) and Coluber constrictor (Eastern Racer) are widespread North American snakes with similar foraging modes and habits. Little is known about the selection of prey by either species, and despite their apparently similar foraging habits, comparative studies of the foraging ecology of sympatric M. flagellum and C. constrictor are lacking. We examined the foraging ecology and prey selection of these actively foraging snakes in xeric, open-canopied Florida scrub habitat by defining prey availability separately for each snake to elucidate mechanisms underlying geographic, temporal, and interspecific variation in predator diets. Nineteen percent of M. flagellum and 28% of C. constrictor contained stomach contents, and most snakes contained only one prey item. Mean relative prey mass for both species was less than 10%. Larger C. constrictor consumed larger prey than small individuals, but this relationship disappeared when prey size was scaled to snake size. Masticophis flagellum was selective at the prey category level, and positively selected lizards and mammals; however, within these categories it consumed prey species in proportion to their availability. In contrast, C. constrictor preyed upon prey categories opportunistically, but was selective with regard to species. Specifically, C. constrictor positively selected Hyla femoralis (Pine Woods Treefrog) and negatively selected Bufo querclcus (Oak Toad), B. terrestris (Southern Toad), and Gastrophryne carolinensis (Eastern Narrowmouth Toad). Thus, despite their similar foraging habits, M. flagellum and C. constrictor select different prey and are selective of prey at different levels of taxonomy. ?? 2008 by the American Society of Ichthyologists and Herpetologists.

  18. Evidence of unique and generalist microbes in distantly related sympatric intertidal marine sponges (Porifera: Demospongiae).

    PubMed

    Alex, Anoop; Silva, Vitor; Vasconcelos, Vitor; Antunes, Agostinho

    2013-01-01

    The diversity and specificity of microbial communities in marine environments is a key aspect of the ecology and evolution of both the eukaryotic hosts and their associated prokaryotes. Marine sponges harbor phylogenetically diverse and complex microbial lineages. Here, we investigated the sponge bacterial community and distribution patterns of microbes in three sympatric intertidal marine demosponges, Hymeniacidon perlevis, Ophlitaspongia papilla and Polymastia penicillus, from the Atlantic coast of Portugal using classical isolation techniques and 16S rRNA gene clone libraries. Microbial composition assessment, with nearly full-length 16S rRNA gene sequences (ca. 1400 bp) from the isolates (n = 31) and partial sequences (ca. 280 bp) from clone libraries (n = 349), revealed diverse bacterial communities and other sponge-associated microbes. The majority of the bacterial isolates were members of the order Vibrionales and other symbiotic bacteria like Pseudovibrio ascidiaceiocola, Roseobacter sp., Hahellaceae sp. and Cobetia sp. Extended analyses using ecological metrics comprising 142 OTUs supported the clear differentiation of bacterial community profiles among the sponge hosts and their ambient seawater. Phylogenetic analyses were insightful in defining clades representing shared bacterial communities, particularly between H. perlevis and the geographically distantly-related H. heliophila, but also among other sponges. Furthermore, we also observed three distinct and unique bacterial groups, Betaproteobactria (~81%), Spirochaetes (~7%) and Chloroflexi (~3%), which are strictly maintained in low-microbial-abundance host species O. papilla and P. penicillus. Our study revealed the largely generalist nature of microbial associations among these co-occurring intertidal marine sponges. PMID:24265835

  19. Arsenic Speciation in Groundwater: Role of Thioanions

    EPA Science Inventory

    The behavior of arsenic in groundwater environments is fundamentally linked to its speciation. Understanding arsenic speciation is important because chemical speciation impacts reactivity, bioavailability, toxicity, and transport and fate processes. In aerobic environments arsen...

  20. Speciation and Introgression between Mimulus nasutus and Mimulus guttatus

    PubMed Central

    Flagel, Lex; Coop, Graham; Sweigart, Andrea L.

    2014-01-01

    Mimulus guttatus and M. nasutus are an evolutionary and ecological model sister species pair differentiated by ecology, mating system, and partial reproductive isolation. Despite extensive research on this system, the history of divergence and differentiation in this sister pair is unclear. We present and analyze a population genomic data set which shows that M. nasutus budded from a central Californian M. guttatus population within the last 200 to 500 thousand years. In this time, the M. nasutus genome has accrued genomic signatures of the transition to predominant selfing, including an elevated proportion of nonsynonymous variants, an accumulation of premature stop codons, and extended levels of linkage disequilibrium. Despite clear biological differentiation, we document genomic signatures of ongoing, bidirectional introgression. We observe a negative relationship between the recombination rate and divergence between M. nasutus and sympatric M. guttatus samples, suggesting that selection acts against M. nasutus ancestry in M. guttatus. PMID:24967630

  1. SPECIATE--EPA'S DATABASE OF SPECIATED EMISSION PROFILES

    EPA Science Inventory

    SPECIATE is EPA's repository of Total Organic Compound and Particulate Matter speciated profiles for a wide variety of sources. The profiles in this system are provided for air quality dispersion modeling and as a library for source-receptor and source apportionment type models. ...

  2. Speciation with gene flow on Lord Howe Island

    PubMed Central

    Papadopulos, Alexander S. T.; Baker, William J.; Crayn, Darren; Butlin, Roger K.; Kynast, Ralf G.; Hutton, Ian; Savolainen, Vincent

    2011-01-01

    Understanding the processes underlying the origin of species is a fundamental goal of biology. It is widely accepted that speciation requires an interruption of gene flow between populations: ongoing gene exchange is considered a major hindrance to population divergence and, ultimately, to the evolution of new species. Where a geographic barrier to reproductive isolation is lacking, a biological mechanism for speciation is required to counterbalance the homogenizing effect of gene flow. Speciation with initially strong gene flow is thought to be extremely rare, and few convincing empirical examples have been published. However, using phylogenetic, karyological, and ecological data for the flora of a minute oceanic island (Lord Howe Island, LHI), we demonstrate that speciation with gene flow may, in fact, be frequent in some instances and could account for one in five of the endemic plant species of LHI. We present 11 potential instances of species divergence with gene flow, including an in situ radiation of five species of Coprosma (Rubiaceae, the coffee family). These results, together with the speciation of Howea palms on LHI, challenge current views on the origin of species diversity. PMID:21730151

  3. Latitude, elevational climatic zonation and speciation in New World vertebrates.

    PubMed

    Cadena, Carlos Daniel; Kozak, Kenneth H; Gómez, Juan Pablo; Parra, Juan Luis; McCain, Christy M; Bowie, Rauri C K; Carnaval, Ana C; Moritz, Craig; Rahbek, Carsten; Roberts, Trina E; Sanders, Nathan J; Schneider, Christopher J; VanDerWal, Jeremy; Zamudio, Kelly R; Graham, Catherine H

    2012-01-01

    Many biodiversity hotspots are located in montane regions, especially in the tropics. A possible explanation for this pattern is that the narrow thermal tolerances of tropical species and greater climatic stratification of tropical mountains create more opportunities for climate-associated parapatric or allopatric speciation in the tropics relative to the temperate zone. However, it is unclear whether a general relationship exists among latitude, climatic zonation and the ecology of speciation. Recent taxon-specific studies obtained different results regarding the role of climate in speciation in tropical versus temperate areas. Here, we quantify overlap in the climatic distributions of 93 pairs of sister species of mammals, birds, amphibians and reptiles restricted to either the New World tropics or to the Northern temperate zone. We show that elevational ranges of tropical- and temperate-zone species do not differ from one another, yet the temperature range experienced by species in the temperate zone is greater than for those in the tropics. Moreover, tropical sister species tend to exhibit greater similarity in their climatic distributions than temperate sister species. This pattern suggests that evolutionary conservatism in the thermal niches of tropical taxa, coupled with the greater thermal zonation of tropical mountains, may result in increased opportunities for allopatric isolation, speciation and the accumulation of species in tropical montane regions. Our study exemplifies the power of combining phylogenetic and spatial datasets of global climatic variation to explore evolutionary (rather than purely ecological) explanations for the high biodiversity of tropical montane regions. PMID:21632626

  4. Deep sympatric mitochondrial divergence without reproductive isolation in the common redstart Phoenicurus phoenicurus.

    PubMed

    Hogner, Silje; Laskemoen, Terje; Lifjeld, Jan T; Porkert, Jiri; Kleven, Oddmund; Albayrak, Tamer; Kabasakal, Bekir; Johnsen, Arild

    2012-12-01

    Mitochondrial DNA usually shows low sequence variation within and high sequence divergence among species, which makes it a useful marker for phylogenetic inference and DNA barcoding. A previous study on the common redstart (Phoenicurus phoenicurus) revealed two very different mtDNA haplogroups (5% K2P distance). This divergence is comparable to that among many sister species; however, both haplogroups coexist and interbreed in Europe today. Herein, we describe the phylogeographic pattern of these lineages and test hypotheses for how such high diversity in mtDNA has evolved. We found no evidence for mitochondrial pseudogenes confirming that both haplotypes are of mitochondrial origin. When testing for possible reproductive barriers, we found no evidence for lineage-specific assortative mating and no difference in sperm morphology, indicating that they are not examples of cryptic species, nor likely to reflect the early stages of speciation. A gene tree based on a short fragment of cytochrome c oxidase subunit 1 from the common redstart and 10 other Phoenicurus species, showed no introgression from any of the extant congenerics. However, introgression from an extinct congeneric cannot be excluded. Sequences from two nuclear introns did not show a similar differentiation into two distinct groups. Mismatch distributions indicated that the lineages have undergone similar demographic changes. Taken together, these results confirm that deeply divergent mitochondrial lineages can coexist in biological species. Sympatric mtDNA divergences are relatively rare in birds, but the fact that they occur argues against the use of threshold mtDNA divergences in species delineation. PMID:23301165

  5. Deep sympatric mitochondrial divergence without reproductive isolation in the common redstart Phoenicurus phoenicurus

    PubMed Central

    Hogner, Silje; Laskemoen, Terje; Lifjeld, Jan T; Porkert, Jiri; Kleven, Oddmund; Albayrak, Tamer; Kabasakal, Bekir; Johnsen, Arild

    2012-01-01

    Mitochondrial DNA usually shows low sequence variation within and high sequence divergence among species, which makes it a useful marker for phylogenetic inference and DNA barcoding. A previous study on the common redstart (Phoenicurus phoenicurus) revealed two very different mtDNA haplogroups (5% K2P distance). This divergence is comparable to that among many sister species; however, both haplogroups coexist and interbreed in Europe today. Herein, we describe the phylogeographic pattern of these lineages and test hypotheses for how such high diversity in mtDNA has evolved. We found no evidence for mitochondrial pseudogenes confirming that both haplotypes are of mitochondrial origin. When testing for possible reproductive barriers, we found no evidence for lineage-specific assortative mating and no difference in sperm morphology, indicating that they are not examples of cryptic species, nor likely to reflect the early stages of speciation. A gene tree based on a short fragment of cytochrome c oxidase subunit 1 from the common redstart and 10 other Phoenicurus species, showed no introgression from any of the extant congenerics. However, introgression from an extinct congeneric cannot be excluded. Sequences from two nuclear introns did not show a similar differentiation into two distinct groups. Mismatch distributions indicated that the lineages have undergone similar demographic changes. Taken together, these results confirm that deeply divergent mitochondrial lineages can coexist in biological species. Sympatric mtDNA divergences are relatively rare in birds, but the fact that they occur argues against the use of threshold mtDNA divergences in species delineation. PMID:23301165

  6. Spatial Niche Segregation of Sympatric Stone Marten and Pine Marten--Avoidance of Competition or Selection of Optimal Habitat?

    PubMed

    Wereszczuk, Anna; Zalewski, Andrzej

    2015-01-01

    Coexistence of ecologically similar species relies on differences in one or more dimensions of their ecological niches, such as space, time and resources in diel and/or seasonal scales. However, niche differentiation may result from other mechanisms such as avoidance of high predation pressure, different adaptations or requirements of ecologically similar species. Stone marten (Martes foina) and pine marten (Martes martes) occur sympatrically over a large area in Central Europe and utilize similar habitats and food, therefore it is expected that their coexistence requires differentiation in at least one of their niche dimensions or the mechanisms through which these dimensions are used. To test this hypothesis, we used differences in the species activity patterns and habitat selection, estimated with a resource selection function (RSF), to predict the relative probability of occurrence of the two species within a large forest complex in the northern geographic range of the stone marten. Stone martens were significantly heavier, have a longer body and a better body condition than pine martens. We found weak evidence for temporal niche segregation between the species. Stone and pine martens were both primarily nocturnal, but pine martens were active more frequently during the day and significantly reduced the duration of activity during autumn-winter. Stone and pine martens utilized different habitats and almost completely separated their habitat niches. Stone marten strongly preferred developed areas and avoided meadows and coniferous or deciduous forests. Pine marten preferred deciduous forest and small patches covered by trees, and avoided developed areas and meadows. We conclude that complete habitat segregation of the two marten species facilitates sympatric coexistence in this area. However, spatial niche segregation between these species was more likely due to differences in adaptation to cold climate, avoidance of high predator pressure and/or food

  7. Spatial Niche Segregation of Sympatric Stone Marten and Pine Marten – Avoidance of Competition or Selection of Optimal Habitat?

    PubMed Central

    Wereszczuk, Anna; Zalewski, Andrzej

    2015-01-01

    Coexistence of ecologically similar species relies on differences in one or more dimensions of their ecological niches, such as space, time and resources in diel and/or seasonal scales. However, niche differentiation may result from other mechanisms such as avoidance of high predation pressure, different adaptations or requirements of ecologically similar species. Stone marten (Martes foina) and pine marten (Martes martes) occur sympatrically over a large area in Central Europe and utilize similar habitats and food, therefore it is expected that their coexistence requires differentiation in at least one of their niche dimensions or the mechanisms through which these dimensions are used. To test this hypothesis, we used differences in the species activity patterns and habitat selection, estimated with a resource selection function (RSF), to predict the relative probability of occurrence of the two species within a large forest complex in the northern geographic range of the stone marten. Stone martens were significantly heavier, have a longer body and a better body condition than pine martens. We found weak evidence for temporal niche segregation between the species. Stone and pine martens were both primarily nocturnal, but pine martens were active more frequently during the day and significantly reduced the duration of activity during autumn-winter. Stone and pine martens utilized different habitats and almost completely separated their habitat niches. Stone marten strongly preferred developed areas and avoided meadows and coniferous or deciduous forests. Pine marten preferred deciduous forest and small patches covered by trees, and avoided developed areas and meadows. We conclude that complete habitat segregation of the two marten species facilitates sympatric coexistence in this area. However, spatial niche segregation between these species was more likely due to differences in adaptation to cold climate, avoidance of high predator pressure and/or food

  8. The drivers of tropical speciation.

    PubMed

    Smith, Brian Tilston; McCormack, John E; Cuervo, Andrés M; Hickerson, Michael J; Aleixo, Alexandre; Cadena, Carlos Daniel; Pérez-Emán, Jorge; Burney, Curtis W; Xie, Xiaoou; Harvey, Michael G; Faircloth, Brant C; Glenn, Travis C; Derryberry, Elizabeth P; Prejean, Jesse; Fields, Samantha; Brumfield, Robb T

    2014-11-20

    Since the recognition that allopatric speciation can be induced by large-scale reconfigurations of the landscape that isolate formerly continuous populations, such as the separation of continents by plate tectonics, the uplift of mountains or the formation of large rivers, landscape change has been viewed as a primary driver of biological diversification. This process is referred to in biogeography as vicariance. In the most species-rich region of the world, the Neotropics, the sundering of populations associated with the Andean uplift is ascribed this principal role in speciation. An alternative model posits that rather than being directly linked to landscape change, allopatric speciation is initiated to a greater extent by dispersal events, with the principal drivers of speciation being organism-specific abilities to persist and disperse in the landscape. Landscape change is not a necessity for speciation in this model. Here we show that spatial and temporal patterns of genetic differentiation in Neotropical birds are highly discordant across lineages and are not reconcilable with a model linking speciation solely to landscape change. Instead, the strongest predictors of speciation are the amount of time a lineage has persisted in the landscape and the ability of birds to move through the landscape matrix. These results, augmented by the observation that most species-level diversity originated after episodes of major Andean uplift in the Neogene period, suggest that dispersal and differentiation on a matrix previously shaped by large-scale landscape events was a major driver of avian speciation in lowland Neotropical rainforests. PMID:25209666

  9. Genome-wide evidence for speciation with gene flow in Heliconius butterflies

    PubMed Central

    Martin, Simon H.; Dasmahapatra, Kanchon K.; Nadeau, Nicola J.; Salazar, Camilo; Walters, James R.; Simpson, Fraser; Blaxter, Mark; Manica, Andrea; Mallet, James; Jiggins, Chris D.

    2013-01-01

    Most speciation events probably occur gradually, without complete and immediate reproductive isolation, but the full extent of gene flow between diverging species has rarely been characterized on a genome-wide scale. Documenting the extent and timing of admixture between diverging species can clarify the role of geographic isolation in speciation. Here we use new methodology to quantify admixture at different stages of divergence in Heliconius butterflies, based on whole-genome sequences of 31 individuals. Comparisons between sympatric and allopatric populations of H. melpomene, H. cydno, and H. timareta revealed a genome-wide trend of increased shared variation in sympatry, indicative of pervasive interspecific gene flow. Up to 40% of 100-kb genomic windows clustered by geography rather than by species, demonstrating that a very substantial fraction of the genome has been shared between sympatric species. Analyses of genetic variation shared over different time intervals suggested that admixture between these species has continued since early in speciation. Alleles shared between species during recent time intervals displayed higher levels of linkage disequilibrium than those shared over longer time intervals, suggesting that this admixture took place at multiple points during divergence and is probably ongoing. The signal of admixture was significantly reduced around loci controlling divergent wing patterns, as well as throughout the Z chromosome, consistent with strong selection for Müllerian mimicry and with known Z-linked hybrid incompatibility. Overall these results show that species divergence can occur in the face of persistent and genome-wide admixture over long periods of time. PMID:24045163

  10. SPECIATE 4.0: SPECIATION DATABASE DEVELOPMENT DOCUMENTATION--FINAL REPORT

    EPA Science Inventory

    SPECIATE is the U.S. EPA's repository of total organic compounds (TOC) and particulate matter (PM) speciation profiles of air pollution sources. This report documents how EPA developed the SPECIATE 4.0 database that replaces the prior version, SPECIATE 3.2. SPECIATE 4.0 includes ...

  11. Environmental speciation of actinides.

    PubMed

    Maher, Kate; Bargar, John R; Brown, Gordon E

    2013-04-01

    Although minor in abundance in Earth's crust (U, 2-4 ppm; Th, 10-15 ppm) and in seawater (U, 0.003 ppm; Th, 0.0007 ppm), light actinides (Th, Pa, U, Np, Pu, Am, and Cm) are important environmental contaminants associated with anthropogenic activities such as the mining and milling of uranium ores, generation of nuclear energy, and storage of legacy waste resulting from the manufacturing and testing of nuclear weapons. In this review, we discuss the abundance, production, and environmental sources of naturally occurring and some man-made light actinides. As is the case with other environmental contaminants, the solubility, transport properties, bioavailability, and toxicity of actinides are dependent on their speciation (composition, oxidation state, molecular-level structure, and nature of the phase in which the contaminant element or molecule occurs). We review the aqueous speciation of U, Np, and Pu as a function of pH and Eh, their interaction with common inorganic and organic ligands in natural waters, and some of the common U-containing minerals. We also discuss the interaction of U, Np, Pu, and Am solution complexes with common Earth materials, including minerals, colloids, gels, natural organic matter (NOM), and microbial organisms, based on simplified model system studies. These surface interactions can inhibit (e.g., sorption to mineral surfaces, formation of insoluble biominerals) or enhance (e.g., colloid-facilitated transport) the dispersal of light actinides in the biosphere and in some cases (e.g., interaction with dissimilatory metal-reducing bacteria, NOM, or Mn- and Fe-containing minerals) can modify the oxidation states and, consequently, the behavior of redox-sensitive light actinides (U, Np, and Pu). Finally, we review the speciation of U and Pu, their chemical transformations, and cleanup histories at several U.S. Department of Energy field sites that have been used to mill U ores, produce fissile materials for reactors and weapons, and store

  12. Global patterns of speciation and diversity.

    PubMed

    de Aguiar, M A M; Baranger, M; Baptestini, E M; Kaufman, L; Bar-Yam, Y

    2009-07-16

    In recent years, strikingly consistent patterns of biodiversity have been identified over space, time, organism type and geographical region. A neutral theory (assuming no environmental selection or organismal interactions) has been shown to predict many patterns of ecological biodiversity. This theory is based on a mechanism by which new species arise similarly to point mutations in a population without sexual reproduction. Here we report the simulation of populations with sexual reproduction, mutation and dispersal. We found simulated time dependence of speciation rates, species-area relationships and species abundance distributions consistent with the behaviours found in nature. From our results, we predict steady speciation rates, more species in one-dimensional environments than two-dimensional environments, three scaling regimes of species-area relationships and lognormal distributions of species abundance with an excess of rare species and a tail that may be approximated by Fisher's logarithmic series. These are consistent with dependences reported for, among others, global birds and flowering plants, marine invertebrate fossils, ray-finned fishes, British birds and moths, North American songbirds, mammal fossils from Kansas and Panamanian shrubs. Quantitative comparisons of specific cases are remarkably successful. Our biodiversity results provide additional evidence that species diversity arises without specific physical barriers. This is similar to heavy traffic flows, where traffic jams can form even without accidents or barriers. PMID:19606148

  13. Pleistocene Speciation in the Genus Populus (Salicaceae)

    PubMed Central

    Levsen, Nicholas D.; Tiffin, Peter; Olson, Matthew S.

    2012-01-01

    The macroevolutionary consequences of recent climate change remain controversial, and there is little paleobotanical or morphological evidence that Pleistocene (1.8–0.12 Ma) glacial cycles acted as drivers of speciation, especially among lineages with long generation times, such as trees. We combined genetic and ecogeographic data from 2 closely related North American tree species, Populus balsamifera and P. trichocarpa (Salicacaeae), to determine if their divergence coincided with and was possibly caused by Pleistocene climatic events. We analyzed 32 nuclear loci from individuals of P. balsamifera and P. trichocarpa to produce coalescent-based estimates of the divergence time between the 2 species. We coupled the coalescent analyses with paleodistribution models to assess the influence of climate change on species' range. Furthermore, measures of niche overlap were used to investigate patterns of ecological differentiation between species. We estimated the divergence date of P. balsamifera and P. trichocarpa at approximately 75 Ka, which corresponds closely with the onset of Marine Isotope Stage 4 (∼76 Ka) and a rapid increase in global ice volume. Significance tests of niche overlap, in conjunction with genetic estimates of migration, suggested that speciation occurred in allopatry, possibly resulting from the environmental effects of Pleistocene glacial cycles. Our results indicate that the divergence of keystone tree species, which have shaped community diversity in northern North American ecosystems, was recent and may have been a consequence of Pleistocene-era glaciation and climate change. PMID:22213709

  14. Host-specific microbial communities in three sympatric North Sea sponges.

    PubMed

    Naim, Mohd Azrul; Morillo, Jose A; Sørensen, Søren J; Waleed, Abu Al-Soud; Smidt, Hauke; Sipkema, Detmer

    2014-11-01

    The establishment of next-generation technology sequencing has deepened our knowledge of marine sponge-associated microbiota with the identification of at least 32 phyla of Bacteria and Archaea from a large number of sponge species. In this study, we assessed the diversity of the microbial communities hosted by three sympatric sponges living in a semi-enclosed North Sea environment using pyrosequencing of bacterial and archaeal 16S ribosomal RNA gene fragments. The three sponges harbor species-specific communities each dominated by a different class of Proteobacteria. An α-proteobacterial Rhodobacter-like phylotype was confirmed as the predominant symbiont of Halichondria panicea. The microbial communities of Haliclona xena and H. oculata are described for the first time in this study and are dominated by Gammaproteobacteria and Betaproteobacteria, respectively. Several common phylotypes belonging to Chlamydiae, TM6, Actinobacteria, and Betaproteobacteria were detected in all sponge samples. A number of phylotypes of the phylum Chlamydiae were present at an unprecedentedly high relative abundance of up to 14.4 ± 1.4% of the total reads, which suggests an important ecological role in North Sea sponges. These Chlamydiae-affiliated operational taxonomic units may represent novel lineages at least at the genus level as they are only 86-92% similar to known sequences. PMID:25088929

  15. Does population size affect genetic diversity? A test with sympatric lizard species.

    PubMed

    Hague, M T J; Routman, E J

    2016-01-01

    Genetic diversity is a fundamental requirement for evolution and adaptation. Nonetheless, the forces that maintain patterns of genetic variation in wild populations are not completely understood. Neutral theory posits that genetic diversity will increase with a larger effective population size and the decreasing effects of drift. However, the lack of compelling evidence for a relationship between genetic diversity and population size in comparative studies has generated some skepticism over the degree that neutral sequence evolution drives overall patterns of diversity. The goal of this study was to measure genetic diversity among sympatric populations of related lizard species that differ in population size and other ecological factors. By sampling related species from a single geographic location, we aimed to reduce nuisance variance in genetic diversity owing to species differences, for example, in mutation rates or historical biogeography. We compared populations of zebra-tailed lizards and western banded geckos, which are abundant and short-lived, to chuckwallas and desert iguanas, which are less common and long-lived. We assessed population genetic diversity at three protein-coding loci for each species. Our results were consistent with the predictions of neutral theory, as the abundant species almost always had higher levels of haplotype diversity than the less common species. Higher population genetic diversity in the abundant species is likely due to a combination of demographic factors, including larger local population sizes (and presumably effective population sizes), faster generation times and high rates of gene flow with other populations. PMID:26306730

  16. Species identification refined by molecular scatology in a community of sympatric carnivores in Xinjiang, China

    PubMed Central

    LAGUARDIA, Alice; WANG, Jun; SHI, Fang-Lei; SHI, Kun; RIORDAN, Philip

    2015-01-01

    Many ecological studies and conservation management plans employ noninvasive scat sampling based on the assumption that species’ scats can be correctly identified in the field. However, in habitats with sympatric similarly sized carnivores, misidentification of scats is frequent and can lead to bias in research results. To address the scat identification dilemma, molecular scatology techniques have been developed to extract DNA from the donor cells present on the outer lining of the scat samples. A total of 100 samples were collected in the winter of 2009 and 2011 in Taxkorgan region of Xinjiang, China. DNA was extracted successfully from 88% of samples and genetic species identification showed that more than half the scats identified in the field as snow leopard (Panthera uncia) actually belonged to fox (Vulpes vulpes). Correlation between scat characteristics and species were investigated, showing that diameter and dry weight of the scat were significantly different between the species. However it was not possible to define a precise range of values for each species because of extensive overlap between the morphological values. This preliminary study confirms that identification of snow leopard feces in the field is misleading. Research that relies upon scat samples to assess distribution or diet of the snow leopard should therefore employ molecular scatology techniques. These methods are financially accessible and employ relatively simple laboratory procedures that can give an indisputable response to species identification from scats. PMID:25855225

  17. Contrasting energy allocation strategies of two sympatric Merluccius species in an upwelling system.

    PubMed

    Rey, J; Fernandez-Peralta, L; Quintanilla, L F; Hidalgo, M; Presas, C; Salmeron, F; Puerto, M A

    2015-03-01

    This study investigated the somatic growth and energy allocation strategy of two sympatric hake species (Merluccius polli and Merluccius senegalensis), coexisting under the strong influence of the Mauritanian upwelling. The results revealed that ontogeny, bathymetry, geography and reproduction shaped the differences found between the condition dynamics of the two species. Aside from species-specific differences, individuals were observed in better condition in the northernmost area (more influenced by the permanent upwelling) and in the deepest waters, probably the most favourable habitat for Merluccius spp. Both species also displayed contrasting trade-offs in energy allocation probably due to the dissimilarity of their habitats, which favours the existence of divergent adaptive strategies in response to different ontogenic requirements. It was hypothesized that M. polli invests in mass and energy reserves while sacrificing growth, as larger sizes may not provide an ecological advantage in a deeper and more stable environment. Moreover, M. senegalensis capitalizes on a steady growth without major disruptions, enabling earlier spawning at the expense of a lower somatic mass, which is fitting to a less stable shallower environment. This study sheds new light on differences in the biological traits and life strategies of Merluccius spp., which permit their overlap in a complex upwelling system and may contribute to the long-lasting scientific-based management of these species. PMID:25641504

  18. Contrasting population genetic patterns and evolutionary histories among sympatric Sonoran Desert cactophilic Drosophila.

    PubMed

    Hurtado, L A; Erez, T; Castrezana, S; Markow, T A

    2004-06-01

    We studied population genetic differentiation in the sympatric Sonoran Desert cactophilic flies Drosophila pachea, D. mettleri and D. nigrospiracula across their continental and peninsular ranges. These flies show marked differences in ecology and behaviour including dispersal distances and host cactus specialization. Examination of a fragment of the mitochondrial cytochrome oxidase subunit I gene (mtCOI) reveals that the Sea of Cortez has constituted an effective dispersal barrier for D. pachea, leading to significant genetic differentiation between the continental and peninsular ranges of this species. No genetic differentiation was detected, however, within its continental and peninsular ranges. In contrast, our mtCOI-based results for D. mettleri and D. nigrospiracula are consistent with a previous allozyme-based study that showed no significant genetic differentiation between continental and peninsular ranges of these two species. For D. mettleri, we also found that the insular population from Santa Catalina Island, California, is genetically differentiated with respect to continental and peninsular localities. We discuss how differences in the genetic structure patterns of D. pachea, D. mettleri and D. nigrospiracula may correspond to differences in their dispersal abilities, host preferences and behaviour. PMID:15140083

  19. Spawning segregation and philopatry are major prezygotic barriers in sympatric cryptic Mugil cephalus species.

    PubMed

    Shen, Kang-Ning; Chang, Chih-Wei; Durand, Jean-Dominique

    2015-12-01

    The flathead mullet, Mugil cephalus, is a commercially vital fish in fisheries and aquaculture worldwide. Genetic analyses have recently revealed three cryptic species of M. cephalus in the Northwest Pacific. These species are sympatric in Taiwanese waters and specific reproductive behaviors have been suggested to be a major prezygotic barrier. Species composition was evaluated in samples of M. cephalus at different growth stages collected from various habitats (offshore spawning ground, estuarine nursery and feeding areas) over several months or years. The gonadosomatic index of adults and the body length of juveniles were recorded to determine the reproductive season and recruitment periods in estuaries. The results revealed partially temporal spawning isolation between species pairs, spatial segregation on specific spawning grounds and strong philopatry preclude hybridization. Thus, the results imply that traditional fisheries of mature fish in the Taiwan Strait target only one species, whereas aquaculture in Taiwan contain juveniles of all three species collected in estuaries. The ecological niche and demography of these species must be investigated further to estimate the impact of juvenile sources on aquaculture. PMID:26563557

  20. CORRELATING METAL SPECIATION IN SOILS

    EPA Science Inventory

    Understanding bioavailability of metals from exposure to contaminated soils is a challenging aspect of environmental research. This presentation will examine three areas of research with respect to metal speciation in soils as it relates to bioavailability: 1) Pb immobilization a...

  1. Coevolution is linked with phenotypic diversification but not speciation in avian brood parasites.

    PubMed

    Medina, Iliana; Langmore, Naomi E

    2015-12-22

    Coevolution is often invoked as an engine of biological diversity. Avian brood parasites and their hosts provide one of the best-known examples of coevolution. Brood parasites lay their eggs in the nests of other species, selecting for host defences and reciprocal counteradaptations in parasites. In theory, this arms race should promote increased rates of speciation and phenotypic evolution. Here, we use recently developed methods to test whether the three largest avian brood parasitic lineages show changes in rates of phenotypic diversity and speciation relative to non-parasitic lineages. Our results challenge the accepted paradigm, and show that there is little consistent evidence that lineages of brood parasites have higher speciation or extinction rates than non-parasitic species. However, we provide the first evidence that the evolution of brood parasitic behaviour may affect rates of evolution in morphological traits associated with parasitism. Specifically, egg size and the colour and pattern of plumage have evolved up to nine times faster in parasitic than in non-parasitic cuckoos. Moreover, cuckoo clades of parasitic species that are sympatric (and share similar host genera) exhibit higher rates of phenotypic evolution. This supports the idea that competition for hosts may be linked to the high phenotypic diversity found in parasitic cuckoos. PMID:26702044

  2. Phylogeny and evolution of the Sulidae (Aves:Pelecaniformes): a test of alternative modes of speciation.

    PubMed

    Friesen, V L; Anderson, D J

    1997-04-01

    Although the allopatric model of speciation is widely accepted, it does not provide a satisfactory explanation for many evolutionary phenomena. Several alternative models exist, but they remain largely untested for vertebrate animals. In the present paper, a molecular phylogeny was used to test competing models of speciation in a seabird family, the Sulidae. A segment including 807 base pairs of the mitochondrial cytochrome b gene was sequenced from all extant sulid species, and phylogenetic methods were used to test model-specific predictions regarding tree topologies, distributions of sister taxa, timing of vicariant events, and comparative biology. Both the neighbor-joining and parsimony analyses placed sequences of gannets (Morus spp.) and boobies of the genus Sula in separate, monophyletic lineages. Sequences of Cape (M. capensis) and Australasian (M. serrator) gannets clustered together, and the sequence of Abbott's booby (Papasula abbotti) was basal to those of the gannets. Sequences of blue-footed (S. nebouxii) and Peruvian (S. variegata) boobies were sisters and formed a monophyletic group with the masked booby (S. dactylatra). The red-footed booby (S. sula) sequence was the most divergent of the Sula boobies. All relationships received strong support from standard-error tests and bootstrap analysis. Substitution rates were similar to those suggested for mammals and suggested that most lineages arose within the last 3 million years. Lineage divergence events for which the mode of speciation could be deduced did not fit the predictions of either allopatric or sympatric models, but apparently involved either peripatric or parapatric processes. PMID:9126567

  3. Regional, seasonal and interspecific variation in 15N and 13C in sympatric mouse lemurs

    NASA Astrophysics Data System (ADS)

    Rakotondranary, S. Jacques; Struck, Ulrich; Knoblauch, Christian; Ganzhorn, Jörg U.

    2011-11-01

    Madagascar provides some of the rare examples where two or more primate species of the same genus and with seemingly identical niche requirements occur in sympatry. If congeneric primate species co-occur in other parts of the world, they differ in size in a way that is consistent with Hutchinson's rule for coexisting species, or they occupy different ecological niches. In some areas of Madagascar, mouse lemurs do not follow these "rules" and thus seem to violate one of the principles of community ecology. In order to understand the mechanisms that allow coexistence of sympatric congeneric species without obvious niche differentiation, we studied food composition of two identical sized omnivorous mouse lemur species, Microcebus griseorufus and M. murinus with the help of stable isotope analyses ( δ 15N and δ 13C). The two species are closely related sister species. During the rich season, when food seems abundant, the two species do not differ in their nitrogen isotope composition, indicating that the two species occupy the same trophic level. But they differ in their δ 13C values, indicating that M. griseorufus feeds more on C4 and CAM (Crassulacean-acid-metabolism) plants than M. murinus. During the lean season, M. murinus has lower δ 15N values, indicating that the two species feed at different trophic levels during times of food shortage. Hybrids between the two species showed intermediate food composition. The results reflect subtle differences in foraging or metabolic adaptations that are difficult to quantify by traditional observations but that represent possibilities to allow coexistence of species.

  4. Evidence of Unique and Generalist Microbes in Distantly Related Sympatric Intertidal Marine Sponges (Porifera: Demospongiae)

    PubMed Central

    Alex, Anoop; Silva, Vitor; Vasconcelos, Vitor; Antunes, Agostinho

    2013-01-01

    The diversity and specificity of microbial communities in marine environments is a key aspect of the ecology and evolution of both the eukaryotic hosts and their associated prokaryotes. Marine sponges harbor phylogenetically diverse and complex microbial lineages. Here, we investigated the sponge bacterial community and distribution patterns of microbes in three sympatric intertidal marine demosponges, Hymeniacidon perlevis, Ophlitaspongia papilla and Polymastia penicillus, from the Atlantic coast of Portugal using classical isolation techniques and 16S rRNA gene clone libraries. Microbial composition assessment, with nearly full-length 16S rRNA gene sequences (ca. 1400 bp) from the isolates (n = 31) and partial sequences (ca. 280 bp) from clone libraries (n = 349), revealed diverse bacterial communities and other sponge-associated microbes. The majority of the bacterial isolates were members of the order Vibrionales and other symbiotic bacteria like Pseudovibrio ascidiaceiocola, Roseobacter sp., Hahellaceae sp. and Cobetia sp. Extended analyses using ecological metrics comprising 142 OTUs supported the clear differentiation of bacterial community profiles among the sponge hosts and their ambient seawater. Phylogenetic analyses were insightful in defining clades representing shared bacterial communities, particularly between H. perlevis and the geographically distantly-related H. heliophila, but also among other sponges. Furthermore, we also observed three distinct and unique bacterial groups, Betaproteobactria (∼81%), Spirochaetes (∼7%) and Chloroflexi (∼3%), which are strictly maintained in low-microbial-abundance host species O. papilla and P. penicillus. Our study revealed the largely generalist nature of microbial associations among these co-occurring intertidal marine sponges. PMID:24265835

  5. Model inadequacy and mistaken inferences of trait-dependent speciation.

    PubMed

    Rabosky, Daniel L; Goldberg, Emma E

    2015-03-01

    Species richness varies widely across the tree of life, and there is great interest in identifying ecological, geographic, and other factors that affect rates of species proliferation. Recent methods for explicitly modeling the relationships among character states, speciation rates, and extinction rates on phylogenetic trees- BiSSE, QuaSSE, GeoSSE, and related models-have been widely used to test hypotheses about character state-dependent diversification rates. Here, we document the disconcerting ease with which neutral traits are inferred to have statistically significant associations with speciation rate. We first demonstrate this unfortunate effect for a known model assumption violation: shifts in speciation rate associated with a character not included in the model. We further show that for many empirical phylogenies, characters simulated in the absence of state-dependent diversification exhibit an even higher Type I error rate, indicating that the method is susceptible to additional, unknown model inadequacies. For traits that evolve slowly, the root cause appears to be a statistical framework that does not require replicated shifts in character state and diversification. However, spurious associations between character state and speciation rate arise even for traits that lack phylogenetic signal, suggesting that phylogenetic pseudoreplication alone cannot fully explain the problem. The surprising severity of this phenomenon suggests that many trait-diversification relationships reported in the literature may not be real. More generally, we highlight the need for diagnosing and understanding the consequences of model inadequacy in phylogenetic comparative methods. PMID:25601943

  6. Density-dependent speciation alters the structure and dynamics of neutral communities.

    PubMed

    Wang, Shaopeng; Chen, Anping; Pacala, Stephen W; Fang, Jingyun

    2015-05-01

    The neutral theory of biodiversity (NTB) provides an individual-based modeling framework to study eco-evolutionary dynamics. Previous NTB models usually assumed the same per capita rate of speciation across lineages. However, population dynamics may induce macroevolutionary feedbacks that can result in variable per capita speciation rates across lineages. In this paper, with analytical and simulation approaches, we explore how different scenarios of density-dependent speciation may impact the diversity and phylogenetic patterns of neutral communities, and compare the results to predictions of the original NTB model with an invariant speciation rate. Our results show that positive per capita speciation rate-abundance relationships could result in higher species richness and evenness, enhanced stability (evidenced by higher post-disturbance recovery rates and lower temporal variability in species diversity), and higher imbalance in phylogenetic trees. The opposite patterns are predicted when per capita speciation rates decrease with abundance. Particularly, strong negative speciation rate-abundance relationships can generate a positive correlation between phylogenetic age and abundance, which has been observed in Panamanian tree species. Our findings demonstrate the importance of eco-evolutionary feedbacks for understanding long-term diversity and phylogenetic patterns in ecological communities. PMID:25701450

  7. The genomics of an adaptive radiation: insights across the Heliconius speciation continuum.

    PubMed

    Supple, Megan; Papa, Riccardo; Counterman, Brian; McMillan, W Owen

    2014-01-01

    Fueled by new technologies that allow rapid and inexpensive assessment of fine scale individual genomic variation, researchers are making transformational discoveries at the interface between genomes and biological complexity. Here we review genomic research in Heliconius butterflies - a radiation characterized by extraordinary phenotypic diversity in warningly colored wing patterns and composed of a continuum of taxa across the stages of speciation. These characteristics, coupled with a 50-year legacy of ecological and behavioral research, offer exceptional prospects for genomic studies into the nature of adaptive differences and the formation of new species. Research in Heliconius provides clear connections between genotype, phenotype, and fitness of wing color patterns shown to underlie adaptation and speciation. This research is challenging our perceptions about how speciation occurs in the presence of gene flow and the role of hybridization in generating adaptive novelty. With the release of the first Heliconius genome assembly, emerging genomic studies are painting a dynamic picture of the evolving species boundary. As the field of speciation genomics moves beyond describing patterns, towards a more integrated understanding of the process of speciation, groups such as Heliconius, where there is a clear speciation continuum and the traits underlying adaptation and speciation are known, will provide a roadmap for identifying variation crucial in the origins of biodiversity. PMID:24277304

  8. Conflict between nuclear and mitochondrial DNA phylogenies of a recent species radiation: what mtDNA reveals and conceals about modes of speciation in Hawaiian crickets.

    PubMed

    Shaw, Kerry L

    2002-12-10

    It has been asserted that recent mtDNA phylogenies support the plausibility of sympatric speciation, long considered a controversial mechanism of the origin of species. If such inferences are reliable, mtDNA phylogenies should be congruent with phylogenies based on other data. In previous work, a mtDNA phylogeny suggested that diversification of the Hawaiian cricket genus Laupala was initiated by single invasions into each of several Hawaiian islands, followed by multiple sympatric divergences within each island. In contrast, a systematic hypothesis based on morphology argues that speciation in Laupala has occurred primarily in allopatry, with two independent species radiations diversifying across the archipelago. In this study, I analyze nuclear DNA (nDNA) sequences from Laupala to compare with sequences from the mtDNA. The nDNA phylogeny corroborates the hypothesis of allopatric divergence and multiple invasions, and when compared with mtDNA patterns, suggests that interspecific hybridization is a persistent feature of the history of Laupala. The discrepancy between mtDNA and nDNA phylogenies reveals that speciation histories based on mtDNA alone can be extensively misleading. PMID:12451181

  9. Thermoregulation of two sympatric species of horned lizards in the Chihuahuan Desert and their local extinction risk.

    PubMed

    Lara-Reséndiz, Rafael A; Gadsden, Héctor; Rosen, Philip C; Sinervo, Barry; Méndez-De la Cruz, Fausto R

    2015-02-01

    Thermoregulatory studies of ectothermic organisms are an important tool for ecological physiology, evolutionary ecology and behavior, and recently have become central for evaluating and predicting global climate change impacts. Here, we present a novel combination of field, laboratory, and modeling approaches to examine body temperature regulation, habitat thermal quality, and hours of thermal restriction on the activity of two sympatric, aridlands horned lizards (Phrynosoma cornutum and Phrynosoma modestum) at three contrasting Chihuahuan Desert sites in Mexico. Using these physiological data, we estimate local extinction risk under predicted climate change within their current geographical distribution. We followed the Hertz et al. (1993, Am. Nat., 142, 796-818) protocol for evaluating thermoregulation and the Sinervo et al. (2010, Science, 328, 894-899) eco-physiological model of extinction under climatic warming. Thermoregulatory indices suggest that both species thermoregulate effectively despite living in habitats of low thermal quality, although high environmental temperatures restrict the activity period of both species. Based on our measurements, if air temperature rises as predicted by climate models, the extinction model projects that P. cornutum will become locally extinct at 6% of sites by 2050 and 18% by 2080 and P. modestum will become extinct at 32% of sites by 2050 and 60% by 2080. The method we apply, using widely available or readily acquired thermal data, along with the modeling, appeared to identify several unique ecological traits that seemingly exacerbate climate sensitivity of P. modestum. PMID:25660624

  10. Sexual conflict and speciation.

    PubMed Central

    Parker, G A; Partridge, L

    1998-01-01

    We review the significance of two forms of sexual conflict (different evolutionary interests of the two sexes) for genetic differentiation of populations and the evolution of reproductive isolation. Conflicting selection on the alleles at a single locus can occur in males and females if the sexes have different optima for a trait, and there are pleiotropic genetic correlations between the sexes for it. There will then be selection for sex limitation and hence sexual dimorphism. This sex limitation could break down in hybrids and reduce their fitness. Pleiotropic genetic correlations between the sexes could also affect the likelihood of mating in interpopulation encounters. Conflict can also occur between (sex-limited) loci that determine behaviour in males and those that determine behaviour in females. Reproductive isolation may occur by rapid coevolution of male trait and female mating preference. This would tend to generate assortative mating on secondary contact, hence promoting speciation. Sexual conflict resulting from sensory exploitation, polyspermy and the cost of mating could result in high levels of interpopulation mating. If females evolve resistance to make pre- and postmating manipulation, males from one population could be more successful with females from the other, because females would have evolved resistance to their own (but not to the allopatric) males. Between-locus sexual conflict could also occur as a result of conflict between males and females of different populations over the production of unfit hybrids. We develop models which show that females are in general selected to resist such matings and males to persist, and this could have a bearing on both the initial level of interpopulation matings and the likelihood that reinforcement will occur. In effect, selection on males usually acts to promote gene flow and to restrict premating isolation, whereas selection on females usually acts in the reverse direction. We review theoretical models

  11. To speciate, or not to speciate? Resource heterogeneity, the subjectivity of similarity, and the macroevolutionary consequences of niche-width shifts in plant-feeding insects.

    PubMed

    Nyman, Tommi

    2010-05-01

    Coevolutionary studies on plants and plant-feeding insects have significantly improved our understanding of the role of niche shifts in the generation of new species. Evolving plant lineages essentially constitute moving islands and archipelagoes in resource space, and host shifts by insects are usually preceded by colonizations of novel resources. Critical to hypotheses concerning ecological speciation is what happens immediately before and after colonization attempts: if an available plant is too similar to the current host(s), it simply will be incorporated into the existing diet, but if it is too different, it will not be colonized in the first place. It thus seems that the probability of speciation is maximized when alternative hosts are at an 'intermediate' distance in resource space. In this review, I wish to highlight the possibility that resource similarity and, thus, the definition of 'intermediate', are subjective concepts that depend on the herbivore lineage's tolerance to dietary variation. This subjectivity of similarity means that changes in tolerance can either decrease or increase speciation probabilities depending on the distribution of plants in resource space: insect lineages with narrow tolerances are likely to speciate by 'island-hopping' on young, species-rich plant groups, whereas more generalized lineages could speciate by shifting among resource archipelagoes formed by higher plant taxa. Repeated and convergent origins of traits known to broaden or to restrict host-plant use in multiple different insect groups provide opportunities for studying how tolerance and resource heterogeneity may interact to determine speciation rates. PMID:20002390

  12. Genomic studies on the nature of species: adaptation and speciation in Mimulus.

    PubMed

    Twyford, Alex D; Streisfeld, Matthew A; Lowry, David B; Friedman, Jannice

    2015-06-01

    Evolutionary biology is in an exciting era, in which powerful genomic tools make the answers accessible to long-standing questions about variation, adaptation and speciation. The availability of a suite of genomic resources, a shared knowledge base and a long history of study have made the phenotypically diverse plant genus Mimulus an important system for understanding ecological and evolutionary processes. An international Mimulus Research Meeting was held at Duke University in June 2014 to discuss developments in ecological and evolutionary genetic studies in Mimulus. Here, we report major recent discoveries presented at the meeting that use genomic approaches to advance our understanding of three major themes: the parallel genetic basis of adaptation; the ecological genomics of speciation; and the evolutionary significance of structural genetic variation. We also suggest future research directions for studies of Mimulus and highlight challenges faced when developing new ecological and evolutionary model systems. PMID:25856725

  13. Incipient allochronic speciation in the pine processionary moth (Thaumetopoea pityocampa, Lepidoptera, Notodontidae).

    PubMed

    Santos, H; Burban, C; Rousselet, J; Rossi, J-P; Branco, M; Kerdelhué, C

    2011-01-01

    A plausible case of allochronic differentiation, where barrier to gene flow is primarily attributable to a phenological shift, was recently discovered in Portugal for the pine processionary moth Thaumetopoea pityocampa. Previous results suggested that the observed 'summer population' (SP) originated from the sympatric winter population (WP). Our objectives were to finely analyse these patterns and test their stability in time, through field monitoring and genetic analyses of larvae and adults across different years. Reproductive activity never overlapped between SP and WP. Microsatellites showed a clear differentiation of the SP, consistent with a strong reduction in gene flow owing to the phenological shift. Assignment tests suggested that some individuals shift from the SP to the WP phenology, causing some hybridization. We discuss these patterns and their maintenance over time. This could be a first stage of allochronic speciation, and SP should be considered as a distinct phenological race. PMID:20964783

  14. Toward a theory of topopatric speciation: The role of genetic assortative mating

    NASA Astrophysics Data System (ADS)

    Schneider, David M.; do Carmo, Eduardo; Martins, Ayana B.; de Aguiar, Marcus A. M.

    2014-09-01

    We discuss a minimalist model of assortative mating for sexually reproducing haploid individuals with two biallelic loci. Assortativeness is introduced in the model by preventing mating between individuals whose alleles differ at both loci. Using methods of dynamical systems and population genetics we provide a full description of the evolution of the system for the case of very large populations. We derive the equations governing the evolution of haplotype frequencies and study the equilibrium solutions, stability, and speed of convergence to equilibrium. We find a constant of motion which allows us to introduce a geometrical construction that makes it straightforward to predict the fate of initial conditions. Finally, we discuss the consequences of this class of assortative mating models, including their possible extensions and implications for sympatric and topopatric speciation.

  15. Iron Speciation in Urban Dust

    SciTech Connect

    E Elzinga; Y Gao; J Fitts; R Tappero

    2011-12-31

    An improved understanding of anthropogenic impacts on ocean fertility requires knowledge of anthropogenic dust mineralogy and associated Fe speciation as a critical step toward developing Fe solubility models constrained by mineralogical composition. This study explored the utility of micro-focused X-ray absorption spectroscopy ({mu}-XAS) in characterizing the speciation of Fe in urban dust samples. A micro-focused beam of 10 x 7 {micro}m made possible the measurement of the Fe K edge XAS spectra of individual dust particles in the PM5.6 size fraction collected in Newark, New Jersey, USA. Spectral analysis indicated the presence of mixtures of Fe-containing minerals within individual dust particles; we observed significant magnetite content along with other Fe(III)-(hydr)oxide minerals which could not be conclusively identified. Our data indicate that detailed quantitative determination of Fe speciation requires extended energy scans to constrain the types and relative abundance of Fe species present. We observe heterogeneity in Fe speciation at the dust particle level, which underscores the importance of analyzing a statistically adequate number of particles within each dust sample. Where possible, {mu}-XAS measurements should be complemented with additional characterization techniques such as {mu}-XRD and bulk XAS to obtain a comprehensive picture of the Fe speciation in dust materials. X-ray microprobes should be used to complement bulk methods used to determine particle composition, methods that fail to record particle heterogeneity.

  16. AN ASSESSMENT OF THERMODYNAMIC REACTION CONSTANTS FOR SIMULATING AQUEOUS ENVIRONMENTAL MONOMETHYLMERCURY SPECIATION

    EPA Science Inventory

    Monomethylmercury (CH3Hg+) is both the most ecologically significant and the least well characterized species of mercury in environmental settings. Our understanding of the environmental speciation behavior of this compound is limited both as the result of lesser available labor...

  17. [Speciation and Risk Characteristics of Heavy Metals in the Sediments of the Yangtze Estuary].

    PubMed

    Yin, Su; Feng, Cheng-hong; Li, Yang-yang; Yin, Li-feng; Shen, Zhen-yao

    2016-03-15

    Based on the investigation on the distribution of total contents and speciation of 8 heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, Zn) in the surface sediments at 14 typical sites of the Yangtze Estuary during three hydrological seasons ( wet, normal, and dry seasons) , this study applied equilibrium partitioning approach to build the sediment quality guidelines (SQGs) of the Yangtze Estuary, and assessed ecological risks of the heavy metals. The relationship between ecological risk and speciation of heavy metals was also revealed. The results showed that, except for Cd, the residual fraction was the main speciation of heavy metals, especially for As, Cr and Hg, their residual fraction proportions were all over 90%. The sediment quality guidelines of the Yangtze Estuary for As, Cd, Cr, Cu, Hg, Ni, Pb, Zn were 43.29, 0.672, 79.65, 19.08, 0.569, 339.09, 30.87, 411.36 µg · g⁻¹, respectively. Cu had the highest ecological risk to aquatic organisms. The upstream of Yangtze Estuary was mainly affected by Yangtze River runoff, where the risks were relatively high in wet season and relatively low in normal and dry seasons. However, the downstream of the estuary was mainly affected by municipal sewage of cities like Shanghai, where the risks were relatively high, especially in normal and dry seasons. There were three different relationships between the ecological risks and speciation of the eight heavy metals. PMID:27337882

  18. Cancer: beyond speciation.

    PubMed

    Vincent, Mark D

    2011-01-01

    A good account of the nature of cancer should provide not only a description of its consistent features, but also how they arise, how they are maintained, why conventional chemotherapy succeeds, and fails, and where to look for better targets. Cancer was once regarded as enigmatic and inexplicable; more recently, the "mutation theory," based on random alterations in a relatively small set of proto-oncogenes and tumor suppressor genes, has enjoyed widespread acceptance. The "mutation theory," however, is noticeable for its failure to explain the basis of differential chemosensitivity, for providing a paucity of targets, especially druggable ones, and for justifying the development of targeted therapies with, in general, disappointingly abbreviated clinical benefit. Furthermore, this theory has mistakenly predicted a widespread commonality of consistent genetic abnormalities across the range of cancers, whereas the opposite, that is, roiling macrogenomic instability, is generally the rule. In contrast, concerning what actually is consistent, that is, the suite of metabolic derangements common to virtually all, especially aggressive, cancers, the "Mutation Theory" has nothing to say. Other hypotheses merit serious consideration "aneuploidy theories" posit whole-genome instability and imbalance as causally responsible for the propagation of the tumor. Another approach, that is, "derepression atavism," suggests cancer results from the release of an ancient survival program, characterized by the emergence of remarkably primitive features such as unicellularity, fermentation, and immortality; existential goals are served by heuristic genomic instability coupled with host-to-tumor biomass interconversion, mediated by the Warburg effect, a major component of the program. Carcinogenesis is here seen as a process of de-speciation; however, genomic nonrestabilization raises issues as to where on the tree of life cancers belong, as a genuinely alternative modus vivendi

  19. Comparative reproductive biology of sympatric species: nest and chick survival of American avocets and black-necked stilts

    USGS Publications Warehouse

    Ackerman, Joshua T.; Herzog, Mark P.; Takekawa, John Y.; Hartman, Christopher A.

    2014-01-01

    Identifying differences in reproductive success rates of closely related and sympatrically breeding species can be useful for understanding limitations to population growth. We simultaneously examined the reproductive ecology of American avocets Recurvirostra americana and black-necked stilts Himantopus mexicanus using 1274 monitored nests and 240 radio-marked chicks in San Francisco Bay, California. Although there were 1.8 times more avocet nests than stilt nests, stilts nonetheless fledged 3.3 times more chicks. Greater production by stilts than avocets was the result of greater chick survival from hatching to fledging (avocet: 6%; stilt: 40%), and not because of differences in clutch size (avocet: 3.84; stilt: 3.77), nest survival (avocet: 44%; stilt: 35%), or egg hatching success (avocet: 90%; stilt: 92%). We reviewed the literature and confirmed that nest survival and hatching success are generally similar when avocets and stilts breed sympatrically. In addition to species, chick survival was strongly influenced by age, site, and year. In particular, daily survival rates increased rapidly with chick age, with 70% of mortalities occurring ≤ 1 week after hatch. California gulls Larus californicus caused 55% of avocet, but only 15% of stilt, chick deaths. Differential use of micro-habitats likely reduced stilt chick’s vulnerability to gull predation, particularly during the first week after hatch, because stilts nested in vegetation 2.7 times more often than avocets and vegetation height was 65% taller at stilt nests compared with avocet nests. Our results demonstrate that two co-occurring and closely related species with similar life history strategies can differ markedly in reproductive success, and simultaneous studies of such species can identify differences that limit productivity.

  20. Understanding host switching through ecological fitting

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Despite the fact that parasites are highly specialized to their hosts, extensive empirical evidence demonstrates that host switching rather than co-speciation is the most important factor influencing the origin of host-parasite associations. Ecological fitting in sloppy fitness space has been propos...

  1. Contrasting patterns of structural host specificity of two species of Heligmosomoides nematodes in sympatric rodents.

    PubMed

    Clough, Dagmar; Råberg, Lars

    2014-12-01

    Host specificity is a fundamental property of parasites. Whereas most studies focus on measures of specificity on host range, only few studies have considered quantitative aspects such as infection intensity or prevalence. The relative importance of these quantitative aspects is still unclear, mainly because of methodological constraints, yet central to a precise assessment of host specificity. Here, we assessed simultaneously two quantitative measures of host specificity of Heligmosomoides glareoli and Heligmosomoides polygyrus polygyrus infections in sympatric rodent hosts. We used standard morphological techniques as well as real-time quantitative PCR and sequencing of the rDNA ITS2 fragment to analyse parasite infection via faecal sample remains. Although both parasite species are thought to be strictly species-specific, we found morphologically and molecularly validated co- and cross-infections. We also detected contrasting patterns within and between host species with regard to specificity for prevalence and intensity of infection. H. glareoli intensities were twofold higher in bank voles than in yellow-necked mice, but prevalence did not differ significantly between species (33 vs. 18%). We found the opposite pattern in H. polygyrus infections with similar intensity levels between host species but significantly higher prevalence in mouse hosts (56 vs. 10%). Detection rates were higher with molecular tools than morphological methods. Our results emphasize the necessity to consider quantitative aspects of specificity for a full view of a parasites' capacity to replicate and transmit in hosts and present a worked example of how modern molecular tools help to advance our understanding of selective forces in host-parasite ecology and evolution. PMID:25273630

  2. Maintenance of strong morphological differentiation despite ongoing natural hybridization between sympatric species of Lomatia (Proteaceae)

    PubMed Central

    McIntosh, Emma J.; Rossetto, Maurizio; Weston, Peter H.; Wardle, Glenda M.

    2014-01-01

    Background and Aims When species cohesion is maintained despite ongoing natural hybridization, many questions are raised about the evolutionary processes operating in the species complex. This study examined the extensive natural hybridization between the Australian native shrubs Lomatia myricoides and L. silaifolia (Proteaceae). These species exhibit striking differences in morphology and ecological preferences, exceeding those found in most studies of hybridization to date. Methods Nuclear microsatellite markers (nSSRs), genotyping methods and morphometric analyses were used to uncover patterns of hybridization and the role of gene flow in morphological differentiation between sympatric species. Key Results The complexity of hybridization patterns differed markedly between sites, however, signals of introgression were present at all sites. One site provided evidence of a large hybrid swarm and the likely presence of multiple hybrid generations and backcrosses, another site a handful of early generational hybrids and a third site only traces of admixture from a past hybridization event. The presence of cryptic hybrids and a pattern of morphological bimodality amongst hybrids often disguised the extent of underlying genetic admixture. Conclusions Distinct parental habitats and phenotypes are expected to form barriers that contribute to the rapid reversion of hybrid populations to their parental character state, due to limited opportunities for hybrid/intermediate advantage. Furthermore, strong genomic filters may facilitate continued gene flow between species without the danger of assimilation. Stochastic fire events facilitate temporal phenological isolation between species and may partly explain the bi-directional and site-specific patterns of hybridization observed. Furthermore, the findings suggest that F1 hybrids are rare, and backcrosses may occur rapidly following these initial hybridization events. PMID:24489011

  3. Alpine Crossroads or Origin of Genetic Diversity? Comparative Phylogeography of Two Sympatric Microgastropod Species

    PubMed Central

    Weigand, Alexander M.; Pfenninger, Markus; Jochum, Adrienne; Klussmann-Kolb, Annette

    2012-01-01

    The Alpine Region, constituting the Alps and the Dinaric Alps, has played a major role in the formation of current patterns of biodiversity either as a contact zone of postglacial expanding lineages or as the origin of genetic diversity. In our study, we tested these hypotheses for two widespread, sympatric microgastropod taxa – Carychium minimum O.F. Müller, 1774 and Carychium tridentatum (Risso, 1826) (Gastropoda, Eupulmonata, Carychiidae) – by using COI sequence data and species potential distribution models analyzed in a statistical phylogeographical framework. Additionally, we examined disjunct transatlantic populations of those taxa from the Azores and North America. In general, both Carychium taxa demonstrate a genetic structure composed of several differentiated haplotype lineages most likely resulting from allopatric diversification in isolated refugial areas during the Pleistocene glacial periods. However, the genetic structure of Carychium minimum is more pronounced, which can be attributed to ecological constraints relating to habitat proximity to permanent bodies of water. For most of the Carychium lineages, the broader Alpine Region was identified as the likely origin of genetic diversity. Several lineages are endemic to the broader Alpine Region whereas a single lineage per species underwent a postglacial expansion to (re)colonize previously unsuitable habitats, e.g. in Northern Europe. The source populations of those expanding lineages can be traced back to the Eastern and Western Alps. Consequently, we identify the Alpine Region as a significant ‘hot-spot’ for the formation of genetic diversity within European Carychium lineages. Passive dispersal via anthropogenic means best explains the presence of transatlantic European Carychium populations on the Azores and in North America. We conclude that passive (anthropogenic) transport could mislead the interpretation of observed phylogeographical patterns in general. PMID:22606334

  4. On the sympatric evolution and evolutionary stability of coexistence by relative nonlinearity of competition.

    PubMed

    Hartig, Florian; Münkemüller, Tamara; Johst, Karin; Dieckmann, Ulf

    2014-01-01

    If two species exhibit different nonlinear responses to a single shared resource, and if each species modifies the resource dynamics such that this favors its competitor, they may stably coexist. This coexistence mechanism, known as relative nonlinearity of competition, is well understood theoretically, but less is known about its evolutionary properties and its prevalence in real communities. We address this challenge by using adaptive dynamics theory and individual-based simulations to compare community stabilization and evolutionary stability of species that coexist by relative nonlinearity. In our analysis, evolution operates on the species' density-compensation strategies, and we consider a trade-off between population growth rates at high and low resource availability. We confirm previous findings that, irrespective of the particular model of density dependence, there are many combinations of overcompensating and undercompensating density-compensation strategies that allow stable coexistence by relative nonlinearity. However, our analysis also shows that most of these strategy combinations are not evolutionarily stable and will be outcompeted by an intermediate density-compensation strategy. Only very specific trade-offs lead to evolutionarily stable coexistence by relative nonlinearity. As we find no reason why these particular trade-offs should be common in nature, we conclude that the sympatric evolution and evolutionary stability of relative nonlinearity, while possible in principle, seems rather unlikely. We speculate that this may, at least in part, explain why empirical demonstrations of this coexistence mechanism are rare, noting, however, that the difficulty to detect relative nonlinearity in the field is an equally likely explanation for the current lack of empirical observations, and that our results are limited to communities with non-overlapping generations and constant resource supply. Our study highlights the need for combining ecological and

  5. How could sympatric megaherbivores coexist? Example of niche partitioning within a proboscidean community from the Miocene of Europe

    NASA Astrophysics Data System (ADS)

    Calandra, Ivan; Göhlich, Ursula B.; Merceron, Gildas

    2008-09-01

    Although low in diversity, megaherbivores (mammals weighting over 103 kg) and especially proboscideans have a powerful impact on the structure and dynamics of present-day ecosystems. During the Neogene (23 to 2.6 Ma) of Europe, the diversity and geographic distribution of these megaherbivores was much greater. Nonetheless, their role in past ecosystems is unclear. Nutrition is one of the main bonds between organisms and their environment. Therefore, the ecology of organisms can be inferred from their dietary habits. The present study is aimed at characterizing the feeding habits of diverse megaherbivores through dental microwear analyses. This method was applied on cheek teeth of three sympatric species of proboscideans from the middle/late Miocene of the Molasse Basin in Southern Germany: Gomphotherium subtapiroideum, Gomphotherium steinheimense, and Deinotherium giganteum. The microwear signatures are significantly different between these taxa, suggesting differences in feeding habits and ecological niches within a woodland environment. D. giganteum probably browsed on dicotyledonous foliages whereas the two species of gomphotheres were neither strict grazers nor strict browsers and instead probably fed on a large spectrum of vegetal resources. The differences of occlusal molar morphology between the two gomphotheres are supported by the dental microwear pattern. Indeed, G. subtapiroideum probably ingested more abrasive material than G. steinheimense. Thus, our results suggest that these proboscideans did not compete for food resources.

  6. Molecular Differentiation of the African Yellow Fever Vector Aedes bromeliae (Diptera: Culicidae) from Its Sympatric Non-vector Sister Species, Aedes lilii

    PubMed Central

    Bennett, Kelly Louise; Linton, Yvonne-Marie; Shija, Fortunate; Kaddumukasa, Martha; Djouaka, Rousseau; Misinzo, Gerald; Lutwama, Julius; Huang, Yiau-Min; Mitchell, Luke B.; Richards, Miriam; Tossou, Eric; Walton, Catherine

    2015-01-01

    Introduction Yellow fever continues to be a problem in sub-Saharan Africa with repeated epidemics occurring. The mosquito Aedes bromeliae is a major vector of yellow fever, but it cannot be readily differentiated from its non-vector zoophilic sister species Ae. lilii using morphological characters. Genetic differences have been reported between anthropophilic Ae. bromeliae and zoophilic Ae. lilii and between forest and domestic populations. However, due to the application of different molecular markers and non-overlapping populations employed in previous studies, interpretation of species delimitation is unclear. Methodology/Principle Findings DNA sequences were generated from specimens of Ae. simpsoni s.l. from the Republic of Benin, Tanzania and Uganda for two nuclear genes apolipophorin 2 (apoLp2) and cytochrome p450 (CYPJ92), the ribosomal internal transcribed spacer region (ITS) and the mitochondrial cytochrome c oxidase (COI) barcoding region. Nuclear genes apoLp2 and CYPJ92 were unable to differentiate between species Ae. bromeliae and Ae. lilii due to ancestral lineage sorting, while ITS sequence data provided clear topological separation on a phylogeny. The standard COI barcoding region was shown to be subject to species introgression and unable to clearly distinguish the two taxa. Here we present a reliable direct PCR-based method for differentiation of the vector species Ae. bromeliae from its isomorphic, sympatric and non-biomedically important sister taxon, Ae. lilii, based on the ITS region. Using molecular species verification, we describe novel immature habitats for Ae. lilii and report both sympatric and allopatric populations. Whereas only Ae. lilii is found in the Republic of Benin and only Ae. bromeliae in Tanzania, both species are sympatric in Uganda. Conclusions/Significance Our accurate identification method will allow informed distribution and detailed ecological studies that will facilitate assessment of arboviral disease risk and

  7. PASSENGER CAR HYDROCARBON EMISSIONS SPECIATION

    EPA Science Inventory

    Emission factors for over 60 individual hydrocarbon compounds were determined for four passenger cars. The cars included a 1963 Chevrolet, a 1977 Mustang, and 1978 Monarch, and 1979 LTD II. The speciation data is reported for both tailpipe and evaporative emissions. The tailpipe ...

  8. A PERSONAL PARTICLE SPECIATION SAMPLER

    EPA Science Inventory

    Dr. Susanne Hering of Aerosol Dynamics Inc and her colleagues expect to design and validate a personal monitoring sampler for particles smaller than 2.5 µm (PM2.5) that is suitable for subsequent chemical speciation work. The investigators believe the result will be a...

  9. Dynamics of evolutionary radiation under ecological neutrality.

    PubMed

    Suzuki, Takanori Mizuno; Chiba, Satoshi

    2016-10-01

    The most spectacular phenomenon of evolutionary biota is the explosive radiation that occurs in depauperate environments in which there are fewer competitors and predators, such as oceanic islands and crater lakes. Adaptation to divergent niches has been proposed as a major cause for this accelerated speciation. Here, we show that neutral mutation, genetic drift, and neutral community dynamics are sufficient to lead to radiation. In addition, these processes yield overshooting dynamics with a decline in species richness in the later stages of radiation. We constructed an ecologically neutral model for a community on an island with a uniform environment. For the speciation process, we introduced a null model with minimal assumptions in which the incompatibilities between alleles in different lineages evolve by a random accumulation of mutations via genetic drift. Our simulations showed that the speciation rate, extinction rate and genetic variation of the species colonizing the island rapidly increased to a sharp peak followed by a decrease that approached zero. Because the extinction rate reached a peak later than the speciation rate, the species richness initially increased, but declined in the later stage, exhibiting "overshooting". The highest species richness was found for the largest island at the largest initial population size. Accordingly, speciation is accelerated by the large population size of depauperate biota, whereas it is decelerated with increasing species richness from the decreasing population size. Explosive radiation without ecological divergence can occur in depauperate environments via neutral stochastic processes. PMID:27297287

  10. Iron speciation and its biological availability in seawater: A workshop

    SciTech Connect

    Wells, M.L.; Bruland, K.W.

    1995-09-08

    This workshop brought together marine chemists with expertise in iron chemistry and biologists with expertise in the role of iron in phytoplankton production to discuss controversies regarding the role of iron in oceanic primary productivity and global climatic change. A new paradigm for marine iron biogeochemistry was generated. The five major new items within this paradigm included (1) the nature of iron inputs to the sea, (2) chemical speciation of iron in seawater, (3) relationships between iron chemistry and marine microbial community dynamics, (4) adaptations of marine microbes to iron input, and (5) ecological and biogeochemical implications of changes in iron supply to the sea.

  11. Molecular characterization of iridoviruses isolated from sympatric amphibians and fish

    USGS Publications Warehouse

    Mao, J.; Green, D.E.; Fellers, G.; Chinchar, V.G.

    1999-01-01

    Iridoviruses infect invertebrates (primarily insects and crustaceans) and ectothermic vertebrates (fish, amphibians, and reptiles). Identical, or nearly identical viruses, have been isolated from different animals within the same taxonomic class, indicating that infection by a given virus is not limited to a single species. Although inter-class infections have been documented following experimental infection with vertebrate iridoviruses, it is not clear whether such infections occur in nature. Here we report the isolation of apparently identical iridoviruses from wild sympatric fish (the threespine stickleback, Gasterostelus aculeatus) and amphibians (the red-legged frog, Rana aurora). Viruses isolated from sticklebacks (stickleback virus, SBV) and from a red-legged frog tadpole (tadpole virus 2, TV2) replicated in fathead minnow (FHM) cells and synthesized proteins which co-migrated with those of frog virus 3 (FV3). Following restriction endonuclease digestion of viral DNA with Hind III and Xba I, gel analysis showed that the profiles of SBV and TV2 were identical to each other and distinct from FV3. Using oligonucleotide primers specific for a highly conserved region of the iridovirus major capsid protein, an not, vert, ~500 nucleotide DNA fragment was amplified from SBV and TV2. Sequence analysis showed that within this 500 nucleotide region SBV and TV2 were identical to each other and to FV3. Taken together these results provide the first evidence that iridoviruses naturally infect animals belonging to different taxonomic classes, and strengthen the suggestion that fish may serve as a reservoir for amphibian viruses or vice versa.

  12. Drastic growth effect may explain sympatric cannibalistic polymorphism.

    PubMed

    Wakano, Joe Yuichiro

    2004-01-01

    Cannibalistic polyphenism is observed in many fishes and amphibians. In the case of amphibian larvae, cannibal morph and typical morph coexist. Benefits and costs of the cannibal morph have been studied empirically but the mechanism of the maintenance of polymorphism is not well known. Here, we construct a game model of typical and cannibal morph strategies to obtain the condition of stable coexistence. Generally, once an individual succeeds in cannibalism, it grows very quickly, which facilitates the next cannibalism. In a model without this 'drastic growth effect', stable coexistence cannot occur. To represent drastic growth effect, it is assumed that cannibal/typical morph stage is followed by giant/normal stage. A cannibal morph that performs cannibalism in the first stage can become a 'giant' in the next stage. This model allows stable coexistence of cannibal and typical morphs. The condition for coexistence is that payoff of a giant is two times larger than normal individuals. As long as direct consumption of victim's body is considered as reward for successful cannibalism, coexistence cannot be explained. When the reward is considered as social standing of being outstanding size in a population, sympatric cannibalistic polymorphism is possible, without regard to the initial size variation or resource shortage. PMID:14637056

  13. Tree of Life Reveals Clock-Like Speciation and Diversification

    PubMed Central

    Hedges, S. Blair; Marin, Julie; Suleski, Michael; Paymer, Madeline; Kumar, Sudhir

    2015-01-01

    Genomic data are rapidly resolving the tree of living species calibrated to time, the timetree of life, which will provide a framework for research in diverse fields of science. Previous analyses of taxonomically restricted timetrees have found a decline in the rate of diversification in many groups of organisms, often attributed to ecological interactions among species. Here, we have synthesized a global timetree of life from 2,274 studies representing 50,632 species and examined the pattern and rate of diversification as well as the timing of speciation. We found that species diversity has been mostly expanding overall and in many smaller groups of species, and that the rate of diversification in eukaryotes has been mostly constant. We also identified, and avoided, potential biases that may have influenced previous analyses of diversification including low levels of taxon sampling, small clade size, and the inclusion of stem branches in clade analyses. We found consistency in time-to-speciation among plants and animals, ∼2 My, as measured by intervals of crown and stem species times. Together, this clock-like change at different levels suggests that speciation and diversification are processes dominated by random events and that adaptive change is largely a separate process. PMID:25739733

  14. Speciation with gene flow and the genetics of habitat transitions.

    PubMed

    Cristescu, Melania E; Constantin, Anna; Bock, Dan G; Cáceres, Carla E; Crease, Teresa J

    2012-03-01

    Whether speciation can advance to completion in the face of initially high levels of gene flow is a very controversial topic in evolutionary biology. Extensive gene exchange is generally considered to homogenize populations and counteract divergence. Moreover, the role of introgressive hybridization in evolution remains largely unexplored in animals, particularly in freshwater zooplankton in which allopatric speciation is considered to be the norm. Our work investigates the genetic structure of two young ecological species: the pond species, Daphnia pulex and the lake species, Daphnia pulicaria. Phylogenetic and population genetics analyses were conducted on mitochondrial NADH dehydrogenase 5 (ND5) gene, the nuclear Lactate dehydrogenase (Ldh) gene and 21 nuclear microsatellite markers in 416 individuals from habitats with various degrees of permanence. The strong and consistent phylogenetic discordance between nuclear and mitochondrial markers suggests a complex evolutionary history of multiple independent habitat transition events that involved hybridization and introgression between lake and pond Daphnia. On the other hand, the low level of contemporary gene flow between adjacent populations indicates the presence of effective habitat isolating barriers. The Daphnia system provides strong evidence for a divergence-with-gene flow speciation model that involves multiple habitat transition events. PMID:22269101

  15. Pathogen exposure varies widely among sympatric populations of wild and domestic felids across the United States

    USGS Publications Warehouse

    Carver, Scott; Bevins, Sarah N.; Lappin, Michael R.; Boydston, Erin E.; Lyren, Lisa M.; Alldredge, Mathew W.; Logan, Kenneth A.; Sweanor, Linda L.; Riley, Seth P.D.; Serieys, Laurel E.K.; Fisher, Robert N.; Vickers, T. Winston; Boyce, Walter M.; McBride, Roy; Cunnigham, Mark C.; Jennings, Megan; Lewis, Jesse S.; Lunn, Tamika; Crooks, Kevin R.; VandeWoude, Sue

    2016-01-01

    Understanding how landscape, host, and pathogen traits contribute to disease exposure requires systematic evaluations of pathogens within and among host species and geographic regions. The relative importance of these attributes is critical for management of wildlife and mitigating domestic animal and human disease, particularly given rapid ecological changes, such as urbanization. We screened >1,000 samples from sympatric populations of puma (Puma concolor), bobcat (Lynx rufus) and domestic cat (Felis catus) across urban gradients in six sites, representing three regions, in North America for exposure to a representative suite of bacterial, protozoal and viral pathogens (Bartonella sp., Toxoplasma gondii, feline herpesvirus-1, feline panleukopenea virus, feline calicivirus, feline immunodeficiency virus). We evaluated prevalence within each species, and examined host trait and land cover determinants of exposure-providing an unprecedented analysis of factors relating to potential for infections in domesticated and wild felids. Prevalence differed among host species (highest for puma and lowest for domestic cat) and was greater for indirectly transmitted pathogens. Sex was inconsistently predictive of exposure to directly transmitted pathogens only, and age infrequently predictive of both direct and indirectly transmitted pathogens. Determinants of pathogen exposure were widely divergent between the wild felid species. For puma, suburban landuse predicted increased exposure to Bartonella sp. in southern California, and FHV-1 exposure increased near urban edges in Florida. This may suggest inter-specific transmission with domestic cats via flea vectors (California) and direct contact (Florida) around urban boundaries. Bobcats captured near urban areas had increased exposure to T. gondii in Florida, suggesting an urban source of prey. Bobcats captured near urban areas in Colorado and Florida had higher FIV exposure, possibly suggesting increased intra

  16. Pathogen exposure varies widely among sympatric populations of wild and domestic felids across the United States.

    PubMed

    Carver, Scott; Bevins, Sarah N; Lappin, Michael R; Boydston, Erin E; Lyren, Lisa M; Alldredge, Mathew; Logan, Kenneth A; Sweanor, Linda L; Riley, Seth P D; Serieys, Laurel E K; Fisher, Robert N; Vickers, T Winston; Boyce, Walter; Mcbride, Roy; Cunningham, Mark C; Jennings, Megan; Lewis, Jesse; Lunn, Tamika; Crooks, Kevin R; Vandewoude, Sue

    2016-03-01

    Understanding how landscape, host, and pathogen traits contribute to disease exposure requires systematic evaluations of pathogens within and among host species and geographic regions. The relative importance of these attributes is critical for management of wildlife and mitigating domestic animal and human disease, particularly given rapid ecological changes, such as urbanization. We screened > 1000 samples from sympatric populations of puma (Puma concolor), bobcat (Lynx rufus), and domestic cat (Felis catus) across urban gradients in six sites, representing three regions, in North America for exposure to a representative suite of bacterial, protozoal, and viral pathogens (Bartonella sp., Toxoplasma gondii, feline herpesvirus-1, feline panleukopenea virus, feline calicivirus, and feline immunodeficiency virus). We evaluated prevalence within each species, and examined host trait and land cover determinants of exposure; providing an unprecedented analysis of factors relating to potential for infections in domesticated and wild felids. Prevalence differed among host species (highest for puma and lowest for domestic cat) and was greater for indirectly transmitted pathogens. Sex was inconsistently predictive of exposure to directly transmitted pathogens only, and age infrequently predictive of both direct and indirectly transmitted pathogens. Determinants of pathogen exposure were widely divergent between the wild felid species. For puma, suburban land use predicted increased exposure to Bartonella sp. in southern California, and FHV-1 exposure increased near urban edges in Florida. This may suggest interspecific transmission with domestic cats via flea vectors (California) and direct contact (Florida) around urban boundaries. Bobcats captured near urban areas had increased exposure to T. gondii in Florida, suggesting an urban source of prey Bobcats captured near urban areas in Colorado and Florida had higher FIV exposure, possibly suggesting increased intraspecific

  17. Administrative Ecology

    ERIC Educational Resources Information Center

    McGarity, Augustus C., III; Maulding, Wanda

    2007-01-01

    This article discusses how all four facets of administrative ecology help dispel the claims about the "impossibility" of the superintendency. These are personal ecology, professional ecology, organizational ecology, and community ecology. Using today's superintendency as an administrative platform, current literature describes a preponderance of…

  18. Difference in flowering time can initiate speciation of nocturnally flowering species.

    PubMed

    Matsumoto, Tomotaka; Yasumoto, Akiko A; Nitta, Kozue; Hirota, Shun K; Yahara, Tetsukazu; Tachida, Hidenori

    2015-04-01

    Isolation mechanisms that prevent gene flow between populations prezygotically play important roles in achieving speciation. In flowering plants, the nighttime flowering system provides a mechanism for isolation from diurnally flowering species. Although this system has long been of interest in evolutionary biology, the evolutionary process leading to this system has yet to be elucidated because of the lack of good model species. However, the genetic mechanisms underlying the differences in flowering times and the traits that attract pollinators between a pair of diurnally and nocturnally flowering species have recently been identified in a few cases. This identification enables us to build a realistic model for theoretically studying the evolution of a nocturnally flowering species. In this study, based on previous experimental data, we assumed a model in which two loci control the flowering time and one locus determines a trait that attracts pollinators. Using this model, we evaluated the possibility of the evolution of a nocturnally flowering species from a diurnally flowering ancestor through simulations. We found that a newly emerging nighttime flowering flower exhibited a sufficiently high fitness, and the evolution of a nocturnally flowering species from a diurnally flowering species could be achieved when hybrid viability was intermediate to low, even in a completely sympatric situation. Our results suggest that the difference in flowering time can act as a magic trait that induces both natural selection and assortative mating and would play an important role in speciation between diurnally and nocturnally flowering species pairs. PMID:25665720

  19. Contrasting activity patterns of sympatric and allopatric black and grizzly bears

    USGS Publications Warehouse

    Schwartz, C.C.; Cain, S.L.; Podruzny, S.; Cherry, S.; Frattaroli, L.

    2010-01-01

    The distribution of grizzly (Ursus arctos) and American black bears (U. americanus) overlaps in western North America. Few studies have detailed activity patterns where the species are sympatric and no studies contrasted patterns where populations are both sympatric and allopatric. We contrasted activity patterns for sympatric black and grizzly bears and for black bears allopatric to grizzly bears, how human influences altered patterns, and rates of grizzlyblack bear predation. Activity patterns differed between black bear populations, with those sympatric to grizzly bears more day-active. Activity patterns of black bears allopatric with grizzly bears were similar to those of female grizzly bears; both were crepuscular and day-active. Male grizzly bears were crepuscular and night-active. Both species were more night-active and less day-active when ???1 km from roads or developments. In our sympatric study area, 2 of 4 black bear mortalities were due to grizzly bear predation. Our results suggested patterns of activity that allowed for intra- and inter-species avoidance. National park management often results in convergence of locally high human densities in quality bear habitat. Our data provide additional understanding into how bears alter their activity patterns in response to other bears and humans and should help park managers minimize undesirable bearhuman encounters when considering needs for temporal and spatial management of humans and human developments in bear habitats. ?? 2010 The Wildlife Society.

  20. Formation of a fluvial non-parasitic population of Lethenteron camtschaticum as the first step in petromyzontid speciation.

    PubMed

    Yamazaki, Y; Yokoyama, R; Nagai, T; Goto, A

    2011-12-01

    To elucidate the petromyzontid speciation process, the genetic independence of the fluvial non-parasitic populations within the anadromous parasitic Lethenteron camtschaticum was estimated by using polymorphic microsatellite loci. Abundant gene flow was revealed in multitemporal scales between potentially sympatric populations, suggesting ongoing gene flow resulting from imperfect size-assortative mating between them and plastic determination of life histories. On the contrary, landlocked fluvial non-parasitic populations in the upper region of dams were genetically divergent from anadromous parasitic populations. The temporal heterogeneity of gene flow, i.e. contemporary little gene flow but significant gene flow over the long-term between the landlocked fluvial non-parasitic and anadromous parasitic populations was elucidated. In addition, the divergence time of isolation of the landlocked populations from the ancestral anadromous parasitic population was estimated to have occurred 17.9-428.2 years ago, which includes the construction times of an initial dam c. 90 years ago. These instances indicate that the landlocked populations should have very recently been established, and subsequent accumulation of divergence and development of reproductive isolation are predicted. The present landlocked fluvial non-parasitic populations should be analogous to the founder populations in terms of petromyzontid speciation. The data also strongly support the hypothesis of multitemporal and multispatial speciation in the petromyzontid stem-satellite species complex. PMID:22141904

  1. Helminth infracommunity structure of the sympatric garter snakes Thamnophis eques and Thamnophis melanogaster from the Mesa Central of Mexico.

    PubMed

    Jiménez-Ruiz, F Agustin; García-Prieto, Luis; Pérez-Ponce de León, Gerardo

    2002-06-01

    Seventy-two Mexican garter snakes (Thamnophis eques) and 126 black-bellied garter snakes (T. melanogaster) were collected from 4 localities of the Mesa Central of Mexico between July 1996 and February 1998 and examined for helminths. Both species of garter snakes occurred sympatrically in every locality except in Lake Cuitzeo. Both species of snakes shared 9 helminth species, and in general, T. melanogaster hosted a larger number of species than T. eques. In each locality, a different helminth species showed the highest levels of prevalence and abundance (Spiroxys susanae in Ciénaga de Lerma, Telorchis corti in Lago de Pátzcuaro, Proteocephalus variabilis in Lago de Cuitzeo, and Contracaecum sp. in Lago de Chapala). Helminth communities in garter snakes of the Mesa Central are depauperate and dominated by a single parasite species. In those localities where the snakes occurred in sympatry, helminth communities were, in general, more diverse and species-rich in T. melanogaster. Differences in the ecology and physiology of these species of garter snakes may explain this pattern because black-bellied garter snakes (T. melanogaster) are more aquatic than Mexican garter snakes (T. eques) and primarily eat aquatic prey, potentially exposing themselves to a larger number of helminths transmitted by predator-prey infection. The helminth infracommunities of garter snakes in the Mesa Central of Mexico show a strong Nearctic influence because most of the species infecting these hosts have been recorded in other Nearctic colubrid snakes. However, the helminth infracommunities of these garter snakes are less species-rich and less diverse than those in colubrid snakes in more temperate latitudes. The widespread ecological perturbation of sampling sites in the Mesa Central because of human activity, and geographic differences in foraging ecology of the hosts and, thus, exposure to parasites transmitted by intermediate hosts may help to explain these patterns. PMID:12099411

  2. MODELING MONOMETHYLMERCURY AND TRIBUTYLTIN SPECIATION WITH EPA'S GEOCHEMICAL SPECIATION MODEL MINTEQA2

    EPA Science Inventory

    Given the complexity of the various, simultaneous (and competing) equilibrium reactions governing the speciation of ionic species in aquatic systems, EPA has developed and distributed the geochemical speciation model MINTEQA2 (Brown and Allison, 1987, Allison et al., 1991; Hydrog...

  3. Ecological Schoolyards.

    ERIC Educational Resources Information Center

    Danks, Sharon Gamson

    2000-01-01

    Presents design guidelines and organizational and site principles for creating schoolyards where students can learn about ecology. Principles for building schoolyard ecological systems are described. (GR)

  4. Identity of two sympatric species of Orius (Hemiptera: Heteroptera: Anthocoridae).

    PubMed

    Shapiro, Jeffrey P; Shirk, Paul D; Kelley, Karen; Lewis, Tamera M; Horton, David R

    2010-01-01

    The minute pirate bugs, Orius insidiosus (Say) and Orius pumilio (Champion) (Hemiptera: Heteroptera: Anthocoridae), are closely related species known to be sympatric in north Florida. Here, male and female genitalia, DNA sequences, and the effects of within- and between-species pairings on egg production and egg development were examined to develop a better understanding of the relationship between these two species. Interspecific matings between the two species did not result in viable progeny. Although there were gross similarities in the morphology of the male parameres (external genitalia) between the two species, the cone in O. pumilio was much broader with a greater spiral twist and the flagellum was longer than in O. insidiosus. Correspondingly, there were differences in the morphology of the copulatory tubes of the females of the two species. In O. insidiosus, the organ was somewhat longer than in O. pumilio and oriented parallel to the abdominal midline, while the copulatory tube in O. pumilio tilted slightly towards the midline. Additionally, the copulatory tube for O. pumilio included a sclerotized basal mound that was not present in O. insidiosus. These morphological differences suggest that successful copulation between these species could be difficult. In contrast to conspecific matings, interspecific matings resulted in few or no eggs laid over a period of two weeks and no viable progeny. Comparison of the 18S ribosomal gene ITS-1 sequences between the two species demonstrated only 91% homology. When yolk protein contents were examined to determine whether reproductive physiology had shifted to full egg production, interspecifically mated females contained amounts of yolk protein comparable to that in fed, but unmated females; this was less than 10% of the yolk protein previously found in fed and conspecifically mated females. These findings together confirm that O. insidiosus and O. pumilio are indeed two separate species. PMID:21265614

  5. Foraging Behaviour Patterns of Four Sympatric Demersal Fishes

    NASA Astrophysics Data System (ADS)

    Labropoulou, M.; Papadopoulou-Smith, K.-N.

    1999-08-01

    The trophic relationships of four sympatric demersal fish species (Mullus barbatus, Mullus surmuletus, Pagrus pagrus and Gobius niger) which dominate the shallow coastal areas (25-30 m) of Iraklion Bay (S Aegean, NE Mediterranean) were investigated from samples collected on a monthly basis (August 1990-August 1992). Stomach content analysis revealed that all four species were carnivorous, feeding mainly on benthic invertebrates. Although these species displayed different feeding modes based on principal prey type utilization, they all consumed a considerable number of polychaetes. In order to understand any underlying patterns of predation on polychaetes, prey items were identified to the lowest possible taxonomic level. The polychaete species were further classified into groups according to their microhabitat (surface or burrowing) and feeding (feeding mode, motility and morphology) guilds. Comparisons of the feeding habits were made using the percentage contribution by number of each prey species in the diet of the predators. Similarities in the diets between the fish species were calculated and cluster analysis was used to describe interspecific variations in food selection, concerning polychaetes. The predatory preferences of each fish species were related to the microhabitat distribution of prey species in the sediment. The differential exploitation of polychaete species was a good indicator of disparate foraging behaviour among the fish species examined, since it reflects a transition from a non-selective to a specialized feeding method. The effects of predator size and morphology of feeding apparatus and the availability of polychaete species in the environment are also discussed to explain the differential exploitation of polychaetes exhibited by the fish.

  6. Arsenic Speciation of Terrestrial Invertebrates

    SciTech Connect

    Moriarty, M.M.; Koch, I.; Gordon, R.A.; Reimer, K.J. ); )

    2009-07-01

    The distribution and chemical form (speciation) of arsenic in terrestrial food chains determines both the amount of arsenic available to higher organisms, and the toxicity of this metalloid in affected ecosystems. Invertebrates are part of complex terrestrial food webs. This paper provides arsenic concentrations and arsenic speciation profiles for eight orders of terrestrial invertebrates collected at three historical gold mine sites and one background site in Nova Scotia, Canada. Total arsenic concentrations, determined by inductively coupled plasma mass spectrometry (ICP-MS), were dependent upon the classification of invertebrate. Arsenic species were determined by high-performance liquid chromatography (HPLC) ICP-MS and X-ray absorption spectroscopy (XAS). Invertebrates were found by HPLC ICP-MS to contain predominantly arsenite and arsenate in methanol/water extracts, while XAS revealed that most arsenic is bound to sulfur in vivo. Examination of the spatial distribution of arsenic within an ant tissue highlighted the differences between exogenous and endogenous arsenic, as well as the extent to which arsenic is transformed upon ingestion. Similar arsenic speciation patterns for invertebrate groups were observed across sites. Trace amounts of arsenobetaine and arsenocholine were identified in slugs, ants, and spiders.

  7. Rates of speciation and morphological evolution are correlated across the largest vertebrate radiation.

    PubMed

    Rabosky, Daniel L; Santini, Francesco; Eastman, Jonathan; Smith, Stephen A; Sidlauskas, Brian; Chang, Jonathan; Alfaro, Michael E

    2013-01-01

    Several evolutionary theories predict that rates of morphological change should be positively associated with the rate at which new species arise. For example, the theory of punctuated equilibrium proposes that phenotypic change typically occurs in rapid bursts associated with speciation events. However, recent phylogenetic studies have found little evidence linking these processes in nature. Here we demonstrate that rates of species diversification are highly correlated with the rate of body size evolution across the 30,000+ living species of ray-finned fishes that comprise the majority of vertebrate biological diversity. This coupling is a general feature of fish evolution and transcends vast differences in ecology and body-plan organization. Our results may reflect a widespread speciational mode of character change in living fishes. Alternatively, these findings are consistent with the hypothesis that phenotypic 'evolvability'-the capacity of organisms to evolve-shapes the dynamics of speciation through time at the largest phylogenetic scales. PMID:23739623

  8. Breakdown in the Process of Incipient Speciation in Anopheles gambiae

    PubMed Central

    Nwakanma, Davis C.; Neafsey, Daniel E.; Jawara, Musa; Adiamoh, Majidah; Lund, Emily; Rodrigues, Amabelia; Loua, Kovana M.; Konate, Lassana; Sy, Ngayo; Dia, Ibrahima; Awolola, T. Samson; Muskavitch, Marc A. T.; Conway, David J.

    2013-01-01

    Understanding genetic causes and effects of speciation in sympatric populations of sexually reproducing eukaryotes is challenging, controversial, and of practical importance for controlling rapidly evolving pests and pathogens. The major African malaria vector mosquito Anopheles gambiae sensu stricto (s.s.) is considered to contain two incipient species with strong reproductive isolation, hybrids between the M and S molecular forms being very rare. Following recent observations of higher proportions of hybrid forms at a few sites in West Africa, we conducted new surveys of 12 sites in four contiguous countries (The Gambia, Senegal, Guinea-Bissau, and Republic of Guinea). Identification and genotyping of 3499 A. gambiae s.s. revealed high frequencies of M/S hybrid forms at each site, ranging from 5 to 42%, and a large spectrum of inbreeding coefficient values from 0.11 to 0.76, spanning most of the range expected between the alternative extremes of panmixia and assortative mating. Year-round sampling over 2 years at one of the sites in The Gambia showed that M/S hybrid forms had similar relative frequencies throughout periods of marked seasonal variation in mosquito breeding and abundance. Genome-wide scans with an Affymetrix high-density single-nucleotide polymorphism (SNP) microarray enabled replicate comparisons of pools of different molecular forms, in three separate populations. These showed strong differentiation between M and S forms only in the pericentromeric region of the X chromosome that contains the molecular form-specific marker locus, with only a few other loci showing minor differences. In the X chromosome, the M/S hybrid forms were more differentiated from M than from S forms, supporting a hypothesis of asymmetric introgression and backcrossing. PMID:23335339

  9. [Caucasian cryptic species of rodents as models for studying the problem of species and speciation].

    PubMed

    Baskevich, M I; Potapov, S G; Mironova, T A

    2015-01-01

    The problem of species and speciation is considered using as a model the cryptic species of rodents inhabiting the Caucasus, the mountain chain with prominent altitude environmental gradient and insular pattern of mountain habitats. These circumstances open additional possibilities for the choice of species conception (biological or phylogenetic), exploration of ancestry pathways (sympatric or allopatric speciation) of model cryptic species groups, and testing the 'refuge' hypothesis. As model species, sibling-species Sicista from the group 'caucasica' (a group of unstriped birch mice) and representatives of the vole subspecies Terricola (Microtus, Arvicolinae) were used. Based on the new data on karyology, nucleotide sequences of mitochondrial gene cytb, multivariate statistical analysis of odontologic traits, and biogeography of sibling-species Sicista from the group 'caucasica' and voles from subspecies Terricola (Microtus, Arvicolinae), their evolutionary history is reconstructed and applicable species concepts are examined. For the present sibling-species Sicista from the group 'caucasica' the allopatric dispersion is typical, which agrees with the hypothesis of speciation in refuges. The sympatry of Terricola sibling-species in the Caucasus is considered as being secondary, and their phenotypic likeness--as an adaptation to similar environmental conditions. Affirmed coexistence of sibling-species Microtus (Terricola) majori and Microtus (Terricola) daghestanicus in the Caucasus (without their hybridization) supports the biological conception of species. The existence of Sicista allospecies from the group of Caucasian unstriped birch mice is best conformed to the phylogenetic conception. However, the high level of chromosomal differences between sibling-species and, in particular, between extreme variants of common evolutionary line (Sicista kazbegica, Sicista kluchorica) does not contradict the biological conception of species. PMID:26353399

  10. Ecological opportunity and the adaptive diversification of lineages.

    PubMed

    Wellborn, Gary A; Langerhans, R Brian

    2015-01-01

    The tenet that ecological opportunity drives adaptive diversification has been central to theories of speciation since Darwin, yet no widely accepted definition or mechanistic framework for the concept currently exists. We propose a definition for ecological opportunity that provides an explicit mechanism for its action. In our formulation, ecological opportunity refers to environmental conditions that both permit the persistence of a lineage within a community, as well as generate divergent natural selection within that lineage. Thus, ecological opportunity arises from two fundamental elements: (1) niche availability, the ability of a population with a phenotype previously absent from a community to persist within that community and (2) niche discordance, the diversifying selection generated by the adaptive mismatch between a population's niche-related traits and the newly encountered ecological conditions. Evolutionary response to ecological opportunity is primarily governed by (1) spatiotemporal structure of ecological opportunity, which influences dynamics of selection and development of reproductive isolation and (2) diversification potential, the biological properties of a lineage that determine its capacity to diversify. Diversification under ecological opportunity proceeds as an increase in niche breadth, development of intraspecific ecotypes, speciation, and additional cycles of diversification that may themselves be triggered by speciation. Extensive ecological opportunity may exist in depauperate communities, but it is unclear whether ecological opportunity abates in species-rich communities. Because ecological opportunity should generally increase during times of rapid and multifarious environmental change, human activities may currently be generating elevated ecological opportunity - but so far little work has directly addressed this topic. Our framework highlights the need for greater synthesis of community ecology and evolutionary biology, unifying

  11. Ecological opportunity and the adaptive diversification of lineages

    PubMed Central

    Wellborn, Gary A; Langerhans, R Brian

    2015-01-01

    The tenet that ecological opportunity drives adaptive diversification has been central to theories of speciation since Darwin, yet no widely accepted definition or mechanistic framework for the concept currently exists. We propose a definition for ecological opportunity that provides an explicit mechanism for its action. In our formulation, ecological opportunity refers to environmental conditions that both permit the persistence of a lineage within a community, as well as generate divergent natural selection within that lineage. Thus, ecological opportunity arises from two fundamental elements: (1) niche availability, the ability of a population with a phenotype previously absent from a community to persist within that community and (2) niche discordance, the diversifying selection generated by the adaptive mismatch between a population's niche-related traits and the newly encountered ecological conditions. Evolutionary response to ecological opportunity is primarily governed by (1) spatiotemporal structure of ecological opportunity, which influences dynamics of selection and development of reproductive isolation and (2) diversification potential, the biological properties of a lineage that determine its capacity to diversify. Diversification under ecological opportunity proceeds as an increase in niche breadth, development of intraspecific ecotypes, speciation, and additional cycles of diversification that may themselves be triggered by speciation. Extensive ecological opportunity may exist in depauperate communities, but it is unclear whether ecological opportunity abates in species-rich communities. Because ecological opportunity should generally increase during times of rapid and multifarious environmental change, human activities may currently be generating elevated ecological opportunity – but so far little work has directly addressed this topic. Our framework highlights the need for greater synthesis of community ecology and evolutionary biology, unifying

  12. Absence of a prezygotic behavioural barrier to gene flow between the two sympatric morphs of the squat lobster Munida gregaria (Fabricius, 1793) (Decapoda: Anomura: Galatheidae)

    NASA Astrophysics Data System (ADS)

    Pérez-Barros, Patricia; Calcagno, Javier A.; Lovrich, Gustavo A.

    2011-12-01

    Munida gregaria and M. subrugosa have been considered two different species for more than a century; however, after a recent molecular phylogenetic study, they are considered a single polymorphic species. Yet, the use of markers to diagnose species may be misleading when divergence between species is recent, since a speciation event may be obscured by the retention and stochastic sorting of ancestral polymorphisms. The morphs gregaria and subrugosa of Munida gregaria constitute an interesting case for the study of behavioural isolation since they are sympatric, breed at the same time of the year, and might have experienced a recent speciation. Mating behaviour observations and mate choice mating trials were conducted in order to investigate the potential existence of a behavioural prezygotic barrier to gene flow between these two morphs. Since factors involved in mate choice in galatheids are unknown, the four possible combinations of the two different morphs in trios were used to test for the existence of mate choice. Video recordings of all the possible trio combinations revealed that there was cross-attraction between males and females of different morphs. Females bearing partial broods participated in encounters as well as non-ovigerous females. The frequency and duration of homo- and heterotypic encounters were registered, and a reproductive isolation index was calculated for each variable for each trio. The isolation indexes calculated were not different from zero indicating random mating, and were not affected by the composition of the trio or the partial ovigerous condition of females. These results provided evidence of the absence of behavioural prezygotic barriers to gene flow between the morphs gregaria and subrugosa of M. gregaria.

  13. Reticulate Speciation and Barriers to Introgression in the Anopheles gambiae Species Complex.

    PubMed

    Crawford, Jacob E; Riehle, Michelle M; Guelbeogo, Wamdaogo M; Gneme, Awa; Sagnon, N'Fale; Vernick, Kenneth D; Nielsen, Rasmus; Lazzaro, Brian P

    2015-11-01

    Speciation as a process remains a central focus of evolutionary biology, but our understanding of the genomic architecture and prevalence of speciation in the face of gene flow remains incomplete. The Anopheles gambiae species complex of malaria mosquitoes is a radiation of ecologically diverse taxa. This complex is well-suited for testing for evidence of a speciation continuum and genomic barriers to introgression because its members exhibit partially overlapping geographic distributions as well as varying levels of divergence and reproductive isolation. We sequenced 20 genomes from wild A. gambiae s.s., Anopheles coluzzii, Anopheles arabiensis, and compared these with 12 genomes from the "GOUNDRY" subgroup of A. gambiae s.l. Amidst a backdrop of strong reproductive isolation, we find strong evidence for a speciation continuum with introgression of autosomal chromosomal regions among species and subgroups. The X chromosome, however, is strongly differentiated among all taxa, pointing to a disproportionately large effect of X chromosome genes in driving speciation among anophelines. Strikingly, we find that autosomal introgression has occurred from contemporary hybridization between A. gambiae and A. arabiensis despite strong divergence (∼5× higher than autosomal divergence) and isolation on the X chromosome. In addition to the X, we find strong evidence that lowly recombining autosomal regions, especially pericentromeric regions, serve as barriers to introgression secondarily to the X. We show that speciation with gene flow results in genomic mosaicism of divergence and introgression. Such a reticulate gene pool connecting vector taxa across the speciation continuum has important implications for malaria control efforts. PMID:26615027

  14. Reticulate Speciation and Barriers to Introgression in the Anopheles gambiae Species Complex

    PubMed Central

    Crawford, Jacob E.; Riehle, Michelle M.; Guelbeogo, Wamdaogo M.; Gneme, Awa; Sagnon, N'Fale; Vernick, Kenneth D.; Nielsen, Rasmus; Lazzaro, Brian P.

    2015-01-01

    Speciation as a process remains a central focus of evolutionary biology, but our understanding of the genomic architecture and prevalence of speciation in the face of gene flow remains incomplete. The Anopheles gambiae species complex of malaria mosquitoes is a radiation of ecologically diverse taxa. This complex is well-suited for testing for evidence of a speciation continuum and genomic barriers to introgression because its members exhibit partially overlapping geographic distributions as well as varying levels of divergence and reproductive isolation. We sequenced 20 genomes from wild A. gambiae s.s., Anopheles coluzzii, Anopheles arabiensis, and compared these with 12 genomes from the “GOUNDRY” subgroup of A. gambiae s.l. Amidst a backdrop of strong reproductive isolation, we find strong evidence for a speciation continuum with introgression of autosomal chromosomal regions among species and subgroups. The X chromosome, however, is strongly differentiated among all taxa, pointing to a disproportionately large effect of X chromosome genes in driving speciation among anophelines. Strikingly, we find that autosomal introgression has occurred from contemporary hybridization between A. gambiae and A. arabiensis despite strong divergence (∼5× higher than autosomal divergence) and isolation on the X chromosome. In addition to the X, we find strong evidence that lowly recombining autosomal regions, especially pericentromeric regions, serve as barriers to introgression secondarily to the X. We show that speciation with gene flow results in genomic mosaicism of divergence and introgression. Such a reticulate gene pool connecting vector taxa across the speciation continuum has important implications for malaria control efforts. PMID:26615027

  15. Increased Noise Levels Have Different Impacts on the Anti-Predator Behaviour of Two Sympatric Fish Species

    PubMed Central

    Voellmy, Irene K.; Purser, Julia; Simpson, Stephen D.; Radford, Andrew N.

    2014-01-01

    Animals must avoid predation to survive and reproduce, and there is increasing evidence that man-made (anthropogenic) factors can influence predator−prey relationships. Anthropogenic noise has been shown to have a variety of effects on many species, but work investigating the impact on anti-predator behaviour is rare. In this laboratory study, we examined how additional noise (playback of field recordings of a ship passing through a harbour), compared with control conditions (playback of recordings from the same harbours without ship noise), affected responses to a visual predatory stimulus. We compared the anti-predator behaviour of two sympatric fish species, the three-spined stickleback (Gasterosteus aculeatus) and the European minnow (Phoxinus phoxinus), which share similar feeding and predator ecologies, but differ in their body armour. Effects of additional-noise playbacks differed between species: sticklebacks responded significantly more quickly to the visual predatory stimulus during additional-noise playbacks than during control conditions, while minnows exhibited no significant change in their response latency. Our results suggest that elevated noise levels have the potential to affect anti-predator behaviour of different species in different ways. Future field-based experiments are needed to confirm whether this effect and the interspecific difference exist in relation to real-world noise sources, and to determine survival and population consequences. PMID:25058618

  16. Morphology, molecular genetics, and bioacoustics support two new sympatric Xenophrys toads (Amphibia: Anura: Megophryidae) in southeast China.

    PubMed

    Wang, Yingyong; Zhao, Jian; Yang, Jianhuan; Zhou, Zhixin; Chen, Guoling; Liu, Yang

    2014-01-01

    Given their recent worldwide declines and extinctions, characterization of species-level diversity is of critical importance for large-scale biodiversity assessments and conservation of amphibians. This task is made difficult by the existence of cryptic species complexes, species groups comprising closely related and morphologically analogous species. The combination of morphology, genetic, and bioacoustic analyses permits robust and accurate species identification. Using these methods, we discovered two undescribed Xenophrys species, namely Xenophrys lini sp. nov. and Xenophrys cheni sp. nov. from the middle range of Luoxiao Mountains, southeast China. These two new species can be reliably distinguished from other known congeners by morphological and morphometric differences, distinctness in male advertisement calls, and substantial genetic distances (>3.6%) based on the mitochondrial 16s and 12s rRNA genes. The two new species, together with X. jinggangensis, are sympatric in the middle range of Luoxiao Mountains but may be isolated altitudinally and ecologically. Our study provides a first step to help resolve previously unrecognized cryptic biodiversity and provides insights into the understanding of Xenophrys diversification in the mountain complexes of southeast China. PMID:24714161

  17. HABITAT-SPECIFIC FORAGING AND SEX DETERMINE MERCURY CONCENTRATIONS IN SYMPATRIC BENTHIC AND LIMNETIC ECOTYPES OF THE THREESPINE STICKLEBACK

    PubMed Central

    Willacker, James J.; Von Hippel, Frank A.; Ackerly, Kerri L.; O’Hara, Todd M.

    2013-01-01

    Mercury (Hg) is a widespread environmental contaminant known for the neurotoxicity of its methylated forms, especially monomethylmercury, which bioaccumulates and biomagnifies in aquatic food webs. Mercury bioaccumulation and biomagnification rates are known to vary among species utilizing different food webs (benthic vs limnetic) within and between systems. The authors assessed whether carbon and nitrogen stable isotope values and total Hg (THg) concentrations differed between sympatric benthic and limnetic ecotypes and sexes of threespine stickleback fish (Gasterosteus aculeatus) from Benka Lake, Alaska, USA. The mean THg concentration in the limnetic ecotype was significantly higher (26 mg/kg dry wt, 16.1%) than that of the benthic ecotype. Trophic position and benthic carbon percentage utilized were both important determinants of THg concentration; however, the 2 variables were of approximately equal importance in females, whereas trophic position clearly explained more of the variance than benthic carbon percentage in males. Additionally, strong sex effects (45 mg/kg dry wt, 29.4%) were observed in both ecotypes, with female fish having lower THg concentrations than males. These results indicate that trophic ecology and sex are both important determinants of Hg contamination even within a single species and lake and likely play a role in governing Hg concentrations in higher trophic levels. PMID:23456641

  18. An integrative approach to detect subtle trophic niche differentiation in the sympatric trawling bat species Myotis dasycneme and Myotis daubentonii.

    PubMed

    Krüger, F; Clare, E L; Greif, S; Siemers, B M; Symondson, W O C; Sommer, R S

    2014-08-01

    Bats are well known for species richness and ecological diversity, and thus, they provide a good opportunity to study relationships and interaction between species. To assess interactions, we consider distinct traits that are probably to be triggered by niche shape and evolutionary processes. We present data on the trophic niche differentiation between two sympatric European trawling bat species, Myotis dasycneme and Myotis daubentonii, incorporating a wide spectrum of methodological approaches. We measure morphological traits involved in foraging and prey handling performance including bite force, weightlifting capacity and wing morphology. We then measure resulting prey consumption using both morphological and molecular diet analyses. These species closely resemble each other in morphological traits, however, subtle but significant differences were apparent in bite force and lift capacity, which are related to differences in basic body and head size. Both morphological and molecular diet analyses show strong niche overlap. We detected subtle differences in less frequent prey items, as well as differences in the exploitation of terrestrial and aquatic-based prey groups. Myotis dasycneme feeds more on aquatic prey, like Chironomidae and their pupal stages, or on the aquatic moth Acentria ephemerella. Myotis daubentonii feeds more on terrestrial prey, like Brachycera, or Coleoptera. This suggests that these bats use different microhabitats within the habitat where they co-occur. PMID:24164379

  19. Validation of three sympatric Thoracophelia species (Annelida: Opheliidae) from Dillon Beach, California using mitochondrial and nuclear DNA sequence data.

    PubMed

    Law, Chris J; Dorgan, Kelly M; Rouse, Greg W

    2013-01-01

    Thoracophelia (Annelida, Opheliidae) are burrowing deposit feeders generally found in the mid- to upper intertidal areas of sandy beaches. Thoracophelia mucronata (Treadwell, 1914) is found along the west coast of North America, including at Dillon Beach, CA. Two additional species, Thoracophelia dillonensis (Hartman, 1938) and T. williamsi (Hartman, 1938) were also described from this beach. These three sympatric species have been primarily distinguished by branchial morphology, and efforts to determine the validity of the species have been based on morphological, reproductive and ecological studies. Here we demonstrate using mitochondrial and nuclear DNA sequence data that these three species are valid. Mitochondrial Cytochrome c subunit 1 (COI) sequences show uncorrected interspecific distances of ~9-13%. We found no inter-specific differences in body color or in hemoglobin concentration, but found that reproductive males were pinkish-red in color and had lower hemoglobin concentrations than purplish-red reproductive females. PMID:24614448

  20. Morphology, Molecular Genetics, and Bioacoustics Support Two New Sympatric Xenophrys Toads (Amphibia: Anura: Megophryidae) in Southeast China

    PubMed Central

    Wang, Yingyong; Zhao, Jian; Yang, Jianhuan; Zhou, Zhixin; Chen, Guoling; Liu, Yang

    2014-01-01

    Given their recent worldwide declines and extinctions, characterization of species-level diversity is of critical importance for large-scale biodiversity assessments and conservation of amphibians. This task is made difficult by the existence of cryptic species complexes, species groups comprising closely related and morphologically analogous species. The combination of morphology, genetic, and bioacoustic analyses permits robust and accurate species identification. Using these methods, we discovered two undescribed Xenophrys species, namely Xenophrys lini sp. nov. and Xenophrys cheni sp. nov. from the middle range of Luoxiao Mountains, southeast China. These two new species can be reliably distinguished from other known congeners by morphological and morphometric differences, distinctness in male advertisement calls, and substantial genetic distances (>3.6%) based on the mitochondrial 16s and 12s rRNA genes. The two new species, together with X. jinggangensis, are sympatric in the middle range of Luoxiao Mountains but may be isolated altitudinally and ecologically. Our study provides a first step to help resolve previously unrecognized cryptic biodiversity and provides insights into the understanding of Xenophrys diversification in the mountain complexes of southeast China. PMID:24714161

  1. Demography and Life Histories of Sympatric Patas Monkeys, Erythrocebus patas, and Vervets, Cercopithecus aethiops, in Laikipia, Kenya

    PubMed Central

    Young, Truman P.; Jaffe, Karin Enstam; Carlson, Anne A.; Chancellor, Rebecca L.

    2009-01-01

    Mortality patterns are thought to be strong selective forces on life history traits, with high adult mortality and low immature mortality favoring early and rapid reproduction. Patas monkeys (Erythrocebus patas) have the highest potential rates of population increase for their body size of any haplorhine primate because they reproduce both earlier and more often. We report here 10 yr of comparative demographic data on a population of patas monkeys and a sympatric population of vervet monkeys (Cercopithecus aethiops), a closely related species differing in aspects of social system, ecology, and life history. The data reveal that 1) adult female patas monkeys have significantly higher mortality than adult female vervets; 2) infant mortality in patas monkeys is relatively low compared to the norm for mammals because it is not significantly different from that of adult female patas monkeys; and 3) infant mortality is significantly higher than adult female mortality in vervets. For both species, much of the mortality could be attributed to predation. An epidemic illness was also a major contributor to the mortality of adult female patas monkeys whereas chronic exposure to pathogens in a cold and damp microenvironment may have contributed to the mortality of infant vervets. Both populations experienced large fluctuations during the study period. Our results support the prediction from demographic models of life history evolution that high adult mortality relative to immature mortality selects for early maturation. PMID:20976285

  2. Noninvasive molecular methods to identify live scarab larvae: an example of sympatric pest and nonpest species in New Zealand.

    PubMed

    Lefort, M-C; Boyer, S; Worner, S P; Armstrong, K

    2012-05-01

    Despite the negative impact that many scarab larvae have on agro-ecosystems, very little attention has been paid to their taxonomy. Their often extremely similar morphological characteristics have probably contributed to this impediment, which has also meant that they are very difficult to identify in the field. Molecular methods can overcome this challenge and are particularly useful for the identification of larvae to enable management of pest species occurring sympatrically with nonpest species. However, the invasive collection of DNA samples for such molecular methods is not compatible with subsequent behavioural, developmental or fitness studies. Two noninvasive DNA sampling and DNA analysis methods suitable for the identification of larvae from closely related scarab species were developed here. Using the frass and larval exuviae as sources of DNA, field-collected larvae of Costelytra zealandica (White) and Costelytra brunneum (Broun) (Scarabaeidae: Melolonthinae) were identified by multiplex PCR based on the difference in size of the resulting PCR products. This study also showed that small quantities of frass can be used reliably even 7 days after excretion. This stability of the DNA is of major importance in ecological studies where timeframes rarely allow daily monitoring. The approach developed here is readily transferable to the study of any holometabolous insect species for which morphological identification of larval stages is difficult. PMID:22189059

  3. Equilibrium speciation dynamics in a model adaptive radiation of island lizards

    PubMed Central

    Rabosky, Daniel L.; Glor, Richard E.

    2010-01-01

    The relative importance of equilibrium and nonequilibrium processes in shaping patterns of species richness is one of the most fundamental questions in biodiversity studies. If equilibrium processes predominate, then ecological interactions presumably limit species diversity, potentially through diversity dependence of immigration, speciation, and extinction rates. Alternatively, species richness may be limited by the rate at which diversity arises or by the amount of time available for diversification. These latter explanations constitute nonequilibrium processes and can apply only to biotas that are unsaturated or far from diversity equilibria. Recent studies have challenged whether equilibrium models apply to biotas assembled through in situ speciation, as this process may be too slow to achieve steady-state diversities. Here we demonstrate that speciation rates in replicate Caribbean lizard radiations have undergone parallel declines to equilibrium conditions on three of four major islands. Our results suggest that feedback between total island diversity and per-capita speciation rates scales inversely with island area, with proportionately greater declines occurring on smaller islands. These results are consistent with strong ecological controls on species richness and suggest that the iconic adaptive radiation of Caribbean anoles may have reached an endpoint. PMID:21135239

  4. Climate change exacerbates interspecific interactions in sympatric coastal fishes.

    PubMed

    Milazzo, Marco; Mirto, Simone; Domenici, Paolo; Gristina, Michele

    2013-03-01

    Biological responses to warming are presently based on the assumption that species will remain within their bioclimatic envelope as environmental conditions change. As a result, changes in the relative abundance of several marine species have been documented over the last decades. This suggests that warming may drive novel interspecific interactions to occur (i.e. invasive vs. native species) or may intensify the strength of pre-existing ones (i.e. warm vs. cold adapted). For mobile species, habitat relocation is a viable solution to track tolerable conditions and reduce competitive costs, resulting in 'winner' species dominating the best quality habitat at the expense of 'loser' species. Here, we focus on the importance of warming in exacerbating interspecific interactions between two sympatric fishes. We assessed the relocation response of the cool-water fish Coris julis (a potential 'loser' species in warming scenarios) at increasing relative dominance of the warm-water fish Thalassoma pavo (a 'winner' species). These wrasses are widespread in the Mediterranean nearshore waters. C. julis tolerates cooler waters and is found throughout the basin. T. pavo is common along southern coasts, although the species range is expanding northwards as the Mediterranean warms. We surveyed habitat patterns along a thermo-latitudinal gradient in the Western Mediterranean Sea and manipulated seawater temperature under two scenarios (present day vs. projected) in outdoor arenas. Our results show that the cool-water species relocates to a less-preferred seagrass habitat and undergoes lower behavioural performance in warmer environments, provided the relative dominance of its warm-water antagonist is high. The results suggest that expected warming will act synergistically with increased relative dominance of a warm-water species to cause a cool-water fish to relocate in a less-preferred habitat within the same thermal environment. Our study highlights the complexity of climate

  5. Contrasting patterns of gene flow between sister plant species in the understorey of African moist forests - the case of sympatric and parapatric Marantaceae species.

    PubMed

    Ley, A C; Hardy, O J

    2014-08-01

    Gene flow within and between species is a fundamental process shaping the evolutionary history of taxa. However, the extent of hybridization and reinforcement is little documented in the tropics. Here we explore the pattern of gene flow between three sister species from the herbaceous genus Marantochloa (Marantaceae), sympatrically distributed in the understorey of the African rainforest, using data from the chloroplast and nuclear genomes (DNA sequences and AFLP). We found highly contrasting patterns: while there was no evidence of gene flow between M. congensis and M. monophylla, species identity between M. monophylla and M. incertifolia was maintained despite considerable gene flow. We hypothesize that M. incertifolia originated from an ancient hybridization event between M. congensis and M. monophylla, considering the current absence of hybridization between the two assumed parent species, the rare presence of shared haplotypes between all three species and the high percentage of haplotypes shared by M. incertifolia with each of the two parent species. This example is contrasted with two parapatrically distributed species from the same family in the genus Haumania forming a hybrid zone restricted to the area of overlap. This work illustrates the diversity of speciation/introgression patterns that can potentially occur in the flora of tropical Africa. PMID:24792083

  6. SPECIATION OF ELEMENTS IN INCINERATION RESIDUES

    EPA Science Inventory

    Knowledge as to the speciation of elements in incineration residues is important for the successful management and utilization of the residues and for modelling and predicting their leaching behavior. s part of a larger research effort on speciation in combustion residues, ESP as...

  7. Rapid speciation and chromosomal evolution in mammals.

    PubMed Central

    Bush, G L; Case, S M; Wilson, A C; Patton, J L

    1977-01-01

    To test the hypothesis that population subdivision into small demes promotes both rapid speciation and evolutionary changes in gene arrangement by inbreeding and drift, we estimated rates of speciation and rates of chromosomal evolution in 225 genera of vertebrates. Rates of speciation were estimated by considering the number of living species in each genus and the fossil record of each genus as well as information about extinction rates. Speciation rate was strongly correlated with rate of chromosomal evolution and average rates of speciation in lower vertebrate genera were one-fifth those in mammalian genera. Genera with high karyotypic diversity and rapid speciation rates may generally have small effective population size (Ne), whereas large Ne values may be associated with karyotypically uniform genera and slow rates of speciation. Speciation and chromosomal evolution seem fastest in those genera with species organized into clans or harems (e.g., some primates and horses) or with limited adult vagility and juvenile dispersal, patchy distribution, and strong individual territoriality (e.g., some rodents). This is consistent with the above hypothesis regarding the evolutionary importance of demes. PMID:269445

  8. Speciation in fungal and oomycete plant pathogens

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The process of speciation by definition involves evolution of one or more reproductive isolating mechanisms that split a single species into two that can no longer interbreed. Determination of which processes are responsible for speciation is important yet challenging. Several studies have proposed ...

  9. Juxtaposition between host population structures: implications for disease transmission in a sympatric cervid community

    PubMed Central

    Vander Wal, Eric; Edye, Iain; Paquet, Paul C; Coltman, David W; Bayne, Erin; Brook, Ryan K; Andrés, José A

    2013-01-01

    Sympatric populations of phylogenetically related species are often vulnerable to similar communicable diseases. Although some host populations may exhibit spatial structure, other hosts within the community may have unstructured populations. Thus, individuals from unstructured host populations may act as interspecific vectors among discrete subpopulations of sympatric alternate hosts. We used a cervid-bovine tuberculosis (Mycobacterium bovis) system to investigate the landscape-scale potential for bovine tuberculosis transmission within a nonmigratory white-tailed deer (Odocoileus virginianus) and elk (Cervus canadensis) community. Using landscape population genetics, we tested for genetic and spatial structure in white-tailed deer. We then compared these findings with the sympatric elk population that is structured and which has structure that correlates spatially and genetically to physiognomic landscape features. Despite genetic structure that indicates the white-tailed deer population forms three sympatric clusters, the absence of spatial structure suggested that intraspecific pathogen transmission is not likely to be limited by physiognomic landscape features. The potential for intraspecific transmission among subpopulations of elk is low due to spatial population structure. Given that white-tailed deer are abundant, widely distributed, and exhibit a distinct lack of spatial population structure, white-tailed deer likely pose a greater threat as bovine tuberculosis vectors among elk subpopulations than elk. PMID:24187583

  10. The Shared Preference Niche of Sympatric Asiatic Black Bears and Sun Bears in a Tropical Forest Mosaic

    PubMed Central

    Steinmetz, Robert; Garshelis, David L.; Chutipong, Wanlop; Seuaturien, Naret

    2011-01-01

    Background Ecologically similar species often coexist by partitioning use of habitats or resources. Such partitioning can occur through divergent or shared niches. We investigated overlap in habitat use and spatial co-occurrence by sympatric Asiatic black bears and sun bears in three habitats in Thailand, and thereby assessed which niche model best accounts for their coexistence. Methods/Principal Findings We used density of species-specific signs to assess habitat use. Signs of both bear species occurred in all three habitats, and on >60% of sampling transects. Both species fed mostly on fruit; insect feeding signs were uncommon, and were mostly from sun bears. Significant differences in habitat use occurred only in montane forest, the habitat in which fruit was most abundant; incidence of black bear sign there was six times higher than that of sun bears. Habitat use was similar between the two species in the other habitats, which comprised 85% of the area. Of 10 habitat attributes examined, fruiting tree density was the best predictor of occurrence for both species. Models that included interspecific competition (fresh foraging activity of the other species) were less supported than the top models without competition. Conclusions/Significance Bear species co-occurrence at both coarse and fine spatial scales and use of the same resources (fruit trees) indicated common niche preferences. However, their habitat use differed in ways expected from their physical differences: larger black bears dominated in the most fruit-rich habitat, and smaller sun bears used less-preferred insects. These results indicate broadly overlapping fundamental niches combined with asymmetric competition—features consistent with the concept of shared preference niches. This model of the niche has received little attention in ecology, but appears to be relatively common in nature. PMID:21283792

  11. Molecular characterization of cryptic and sympatric lymnaeid species from the Galba/Fossaria group in Mendoza Province, Northern Patagonia, Argentina

    PubMed Central

    2013-01-01

    Background Freshwater lymnaeid snails can act as the intermediate hosts for trematode parasites such as the liver fluke Fasciola hepatica, that cause significant economic and biomedical burden worldwide, particularly through bovine fascioliasis. Transmission potential is tightly coupled to local compatibility with snail hosts, so accurate identification of lymnaeid species is crucial for understanding disease risk, especially when invasive species are encountered. Mendoza Province, in Argentina, is a center of livestock production and also an area of endemic fascioliasis transmission. However, the distribution of lymnaeid species in the region is not well known. Methods This study examined lymnaeid snails from seven localities in the Department of Malarguë, Mendoza Province, using morphological and molecular analyses and also describing ecological variables associated with snail presence. Results While morphological characters identified two species of lymnaeid, Galba truncatula and G. viatrix, molecular data revealed a third, cryptic species, G. neotropica, which was sympatric with G. viatrix. G. truncatula was exclusively found in high altitude (>1900 meters above sea level [masl]) sites, whereas mixed G. neotropica/G. viatrix localities were at middle elevations (1300–1900 masl), and G. viatrix was found alone at the lowest altitude sites (<1300 masl). Phylogenetic analysis using two mitochondrial markers revealed G. neotropica and G. viatrix to be closely related, and given their morphological similarities, their validities as separate taxonomic entities should be questioned. Conclusions This study highlights the need of a robust taxonomic framework for the identification of lymnaeid snails, incorporating molecular, morphological and ecological variables while avoiding nomenclature redundancy. As the three species observed here, including one alien invasive species, are considered hosts of varying susceptibility to Fasciola parasites, and given the economic

  12. Coexistence of sympatric carnivores in relatively homogeneous Mediterranean landscapes: functional importance of habitat segregation at the fine-scale level.

    PubMed

    Soto, Carolina; Palomares, Francisco

    2015-09-01

    One of the main objectives of community ecology is to understand the conditions allowing species to coexist. However, few studies have investigated the role of fine-scale habitat use segregation in the functioning of guild communities in relatively homogeneous landscapes where opportunities for coexistence are likely to be the most restrictive. We investigate how the process of habitat use differentiation at the home range level according to the degree of specialism/generalism of species can lead to coexistence between guild species. We examine differences in fine-scale habitat use and niche separation as potential mechanisms explaining the coexistence of five sympatric carnivore species that differ in life history traits (Iberian lynx, Eurasian badger, Egyptian mongoose, common genet and red fox) by collecting data from systematic track censuses in a relatively homogeneous Mediterranean landscape. We found that a higher degree of specialism determines the segregation of species among the fine-scale ecological niche dimensions defined using quantitative elements associated with vegetation, landscape, prey availability and human disturbance. The species with the lowest total performance over the set of variables did not exhibit segregation in the use of habitat at this level. Our study indicates that in relatively homogeneous landscapes, there exist subtle patterns of habitat partitioning over small-scale gradients of habitat determinants as a function of the degree of specialism of carnivore species within a guild. Our results also suggest that coexistence between generalist species may be permitted by fine-scale spatial-temporal segregation of activity patterns or trophic resource consumption, but not fine-scale habitat use differentiation. PMID:25933639

  13. Rates of speciation in the fossil record

    NASA Technical Reports Server (NTRS)

    Sepkoski, J. J. Jr; Sepkoski JJ, J. r. (Principal Investigator)

    1998-01-01

    Data from palaeontology and biodiversity suggest that the global biota should produce an average of three new species per year. However, the fossil record shows large variation around this mean. Rates of origination have declined through the Phanerozoic. This appears to have been largely a function of sorting among higher taxa (especially classes), which exhibit characteristic rates of speciation (and extinction) that differ among them by nearly an order of magnitude. Secular decline of origination rates is hardly constant, however; many positive deviations reflect accelerated speciation during rebounds from mass extinctions. There has also been general decline in rates of speciation within major taxa through their histories, although rates have tended to remain higher among members in tropical regions. Finally, pulses of speciation appear sometimes to be associated with climate change, although moderate oscillations of climate do not necessarily promote speciation despite forcing changes in species' geographical ranges.

  14. The speciation of behavior analysis

    PubMed Central

    Rider, David P.

    1991-01-01

    The relationship between the Experimental Analysis of Behavior (EAB) and Applied Behavior Analysis (ABA) has been the subject of several editorials and commentaries in recent years. Various authors have argued that researchers in these two fields (a) have become isolated from each other, (b) face different requirements for survival in their respective fields, and (c) possess different skills to meet those requirements. The present paper provides an allegory for the relationship between EAB and ABA in terms of biological speciation. The conditions that have changed the relationship between EAB and ABA are parallel to those responsible for biological speciation: (a) isolation of some members of a species from the rest of the population, (b) different contingencies of survival for members of the two separate groups, and (c) divergence in the adaptive characteristics displayed by the two groups. When members of two different groups, descendants of common ancestors, no longer are capable of producing viable offspring by interbreeding, the different groups then represent different species. To the extent that members of the EAB group and members of the ABA group interact with each other only trivially, they each represent allegorically different species. Changes in the relationship between EAB and ABA are part of a natural process that takes place in many other sciences, and the course of that process can hardly be reversed by us. PMID:22478096

  15. Ecological Misconceptions.

    ERIC Educational Resources Information Center

    Munson, Bruce H.

    1994-01-01

    Presents a summary of the research literature on students' ecological conceptions and the implications of misconceptions. Topics include food webs, ecological adaptation, carrying capacity, ecosystem, and niche. (Contains 35 references.) (MKR)

  16. US EPA's SPECIATE 4.4 Database: Development and Uses

    EPA Science Inventory

    SPECIATE is the U.S. Environmental Protection Agency’s (EPA) repository of volatile organic gas and particulate matter (PM) speciation profiles of air pollution sources. EPA released SPECIATE 4.4 in early 2014 and, in total, the SPECIATE 4.4 database includes 5,728 PM, vola...

  17. US EPA's SPECIATE 4.4 Database: Development and Uses

    EPA Science Inventory

    SPECIATE is the U.S. Environmental Protection Agency’s (EPA) repository of volatile organic gas and particulate matter (PM) speciation profiles of air pollution sources. EPA released SPECIATE 4.4 in early 2014 and, in total, the SPECIATE 4.4 database includes 5,728 PM, volatile o...

  18. Backyard Ecology.

    ERIC Educational Resources Information Center

    Elser, Monica; Musheno, Birgit; Saltz, Charlene

    2003-01-01

    Describes the Ecology Explorers, the community education component of Arizona State University's Central Arizona Phoenix Long-Term Ecological Research project, which offers teacher internship programs that link university researchers, K-12 teachers, and students in studying urban ecology. Explains that student neighborhoods are dynamic ecosystems…

  19. Genomic divergence during speciation: causes and consequences

    PubMed Central

    Nosil, Patrik; Feder, Jeffrey L.

    2012-01-01

    Speciation is a fundamental process responsible for the diversity of life. Progress has been made in detecting individual ‘speciation genes’ that cause reproductive isolation. In contrast, until recently, less attention has been given to genome-wide patterns of divergence during speciation. Thus, major questions remain concerning how individual speciation genes are arrayed within the genome, and how this affects speciation. This theme issue is dedicated to exploring this genomic perspective of speciation. Given recent sequencing and computational advances that now allow genomic analyses in most organisms, the goal is to help move the field towards a more integrative approach. This issue draws upon empirical studies in plants and animals, and theoretical work, to review and further document patterns of genomic divergence. In turn, these studies begin to disentangle the role that different processes, such as natural selection, gene flow and recombination rate, play in generating observed patterns. These factors are considered in the context of how genomes diverge as speciation unfolds, from beginning to end. The collective results point to how experimental work is now required, in conjunction with theory and sequencing studies, to move the field from descriptive studies of patterns of divergence towards a predictive framework that tackles the causes and consequences of genome-wide patterns. PMID:22201163

  20. Disruptive ecological selection on a mating cue.

    PubMed

    Merrill, Richard M; Wallbank, Richard W R; Bull, Vanessa; Salazar, Patricio C A; Mallet, James; Stevens, Martin; Jiggins, Chris D

    2012-12-22

    Adaptation to divergent ecological niches can result in speciation. Traits subject to disruptive selection that also contribute to non-random mating will facilitate speciation with gene flow. Such 'magic' or 'multiple-effect' traits may be widespread and important for generating biodiversity, but strong empirical evidence is still lacking. Although there is evidence that putative ecological traits are indeed involved in assortative mating, evidence that these same traits are under divergent selection is considerably weaker. Heliconius butterfly wing patterns are subject to positive frequency-dependent selection by predators, owing to aposematism and Müllerian mimicry, and divergent colour patterns are used by closely related species to recognize potential mates. The amenability of colour patterns to experimental manipulation, independent of other traits, presents an excellent opportunity to test their role during speciation. We conducted field experiments with artificial butterflies, designed to match natural butterflies with respect to avian vision. These were complemented with enclosure trials with live birds and real butterflies. Our experiments showed that hybrid colour-pattern phenotypes are attacked more frequently than parental forms. For the first time, we demonstrate disruptive ecological selection on a trait that also acts as a mating cue. PMID:23075843

  1. Rapid biological speciation driven by tectonic evolution in New Zealand

    NASA Astrophysics Data System (ADS)

    Craw, Dave; Upton, Phaedra; Burridge, Christopher P.; Wallis, Graham P.; Waters, Jonathan M.

    2016-02-01

    Collisions between tectonic plates lead to the rise of new mountain ranges that can separate biological populations and ultimately result in new species. However, the identification of links between tectonic mountain-building and biological speciation is confounded by environmental and ecological factors. Thus, there are surprisingly few well-documented examples of direct tectonic controls on terrestrial biological speciation. Here we present examples from New Zealand, where the rapid evolution of 18 species of freshwater fishes has resulted from parallel tectonic landscape evolution. We use numerical models to reconstruct changes in the deep crustal structure and surface drainage catchments of the southern island of New Zealand over the past 25 million years. We show that the island and mountain topography evolved in six principal tectonic zones, which have distinct drainage catchments that separated fish populations. We use new and existing phylogenetic analyses of freshwater fish populations, based on over 1,000 specimens from more than 400 localities, to show that fish genomes can retain evidence of this tectonic landscape development, with a clear correlation between geologic age and extent of DNA sequence divergence. We conclude that landscape evolution has controlled on-going biological diversification over the past 25 million years.

  2. Niche partitioning in a sympatric cryptic species complex.

    PubMed

    Scriven, Jessica J; Whitehorn, Penelope R; Goulson, Dave; Tinsley, Matthew C

    2016-03-01

    Competition theory states that multiple species should not be able to occupy the same niche indefinitely. Morphologically, similar species are expected to be ecologically alike and exhibit little niche differentiation, which makes it difficult to explain the co-occurrence of cryptic species. Here, we investigated interspecific niche differentiation within a complex of cryptic bumblebee species that co-occur extensively in the United Kingdom. We compared the interspecific variation along different niche dimensions, to determine how they partition a niche to avoid competitive exclusion. We studied the species B. cryptarum, B. lucorum, and B. magnus at a single location in the northwest of Scotland throughout the flight season. Using mitochondrial DNA for species identification, we investigated differences in phenology, response to weather variables and forage use. We also estimated niche region and niche overlap between different castes of the three species. Our results show varying levels of niche partitioning between the bumblebee species along three niche dimensions. The species had contrasting phenologies: The phenology of B. magnus was delayed relative to the other two species, while B. cryptarum had a relatively extended phenology, with workers and males more common than B. lucorum early and late in the season. We found divergent thermal specialisation: In contrast to B. cryptarum and B. magnus, B. lucorum worker activity was skewed toward warmer, sunnier conditions, leading to interspecific temporal variation. Furthermore, the three species differentially exploited the available forage plants: In particular, unlike the other two species, B. magnus fed predominantly on species of heather. The results suggest that ecological divergence in different niche dimensions and spatio-temporal heterogeneity in the environment may contribute to the persistence of cryptic species in sympatry. Furthermore, our study suggests that cryptic species provide distinct

  3. Oxidation-state speciation of

    PubMed

    Hu; Heineman

    2000-06-01

    The analytical utility of chemically modified microelectrodes for oxidation-state speciation of redox couples by cyclic voltammetry has been explored. [Re(I)(DMPE)3]+/[Re(II)(DMPE)3]2+, where DMPE = 1,2-bis(dimethylphosphino)ethane, was studied at carbon-fiber microelectrodes of approximately 5 microm in radius coated with Nafion-entrapped solgel-derived silica (Nafion-silica) composite. The results are compared with cyclic voltammetry of [Fe(CN)6]3-/[Fe(CN)6]4- at bare carbon-fiber microelectrodes. At both microelectrodes, the cathodic and anodic limiting currents are linearly proportional to the concentrations of the reducible and oxidizable species of a redox couple, respectively. The shape of the cyclic voltammogram and the magnitude of the steady-state limiting current are not affected by the potential at which the scan starts. Speciation of both forms of a redox couple could be achieved voltammetrically at the microelectrodes. However, a considerably slower scan rate was required to achieve steady state at the modified electrode because of the smaller diffusion coefficients of [Re(I)(DMPE)3]+ and [Re(II)(DMPE)3]2+ in the Nafion-silica composite. The detection limit at the modified electrode was considerably lower (5 x 10(-9) M for [Re(I)(DMPE)3]+) than at the bare electrode (6 x 10(-5) M for [Fe(CN)6]3- and [Fe(CN)6]4-) because of the substantial preconcentration of [Re(I)(DMPE)3]+ by the Nafion-silica composite. PMID:10857611

  4. Chromosomes, conflict, and epigenetics: chromosomal speciation revisited.

    PubMed

    Brown, Judith D; O'Neill, Rachel J

    2010-01-01

    Since Darwin first noted that the process of speciation was indeed the "mystery of mysteries," scientists have tried to develop testable models for the development of reproductive incompatibilities-the first step in the formation of a new species. Early theorists proposed that chromosome rearrangements were implicated in the process of reproductive isolation; however, the chromosomal speciation model has recently been questioned. In addition, recent data from hybrid model systems indicates that simple epistatic interactions, the Dobzhansky-Muller incompatibilities, are more complex. In fact, incompatibilities are quite broad, including interactions among heterochromatin, small RNAs, and distinct, epigenetically defined genomic regions such as the centromere. In this review, we will examine both classical and current models of chromosomal speciation and describe the "evolving" theory of genetic conflict, epigenetics, and chromosomal speciation. PMID:20438362

  5. CORRELATING METAL SPECIATION IN SOILS TO RISK

    EPA Science Inventory

    Understanding bioavailability of metals from exposure to contaminated soils is a challenging aspect of environmental research. This presentation will examine three areas of research with respect to metal speciation in soils as it relates to bioavailability: 1) Pb immobilization a...

  6. Progenitor–derivative speciation in Pozoa (Apiaceae, Azorelloideae) of the southern Andes

    PubMed Central

    López, Patricio; Tremetsberger, Karin; Kohl, Gudrun; Stuessy, Tod

    2012-01-01

    Background and Aims Studies examining patterns and processes of speciation in South America are fewer than in North America and Europe. One of the least well documented processes has been progenitor–derivative speciation. A particularly instructive example occurs in the southern Andes in the genus Pozoa (Apiaceae, Azorelloideae), which consists of only two diploid outcrossing species, the widespread P. coriacea and the geographically and ecologically restricted P. volcanica. This paper tests the hypothesis that the latter species originated from the former through local geographical and ecological isolation by progenitor–derivative speciation. Methods DNA sequences were analysed from Pozoa and the related South American genera Asteriscium, Eremocharis and Gymnophyton from non-coding regions of the plastid genome, ndhF-rpl32 and rpl32-trnL, plus incorporation of previously reported rpl16 intron and trnD-trnT intergenic spacer sequences. Amplified fragment length polymorphism (AFLP) data from 105 individuals in 21 populations throughout the entire range of distribution of the genus were used for estimation of genetic diversity, divergence and SplitsTree network analysis. Ecological factors, including habitat and associated species, were also examined. Key Results Pozoa coriacea is more similar genetically to the outgroup genera, Asteriscium and Eremocharis, than is P. volcanica. At the population level, only P. volcanica is monophyletic, whereas P. coriacea is paraphyletic. Analyses of genetic differentiation among populations and genetic divergence and diversity of the species show highest values in P. coriacea and clear reductions in P. volcanica. Pozoa coriacea occurs in several types of high elevation habitats, whereas P. volcanica is found only in newly formed open volcanic ash zones. Conclusions All facts support that Pozoa represents a good example of progenitor–derivative speciation in the Andes of southern South America. PMID:22112441

  7. Metabolic ecology.

    PubMed

    Humphries, Murray M; McCann, Kevin S

    2014-01-01

    Ecological theory that is grounded in metabolic currencies and constraints offers the potential to link ecological outcomes to biophysical processes across multiple scales of organization. The metabolic theory of ecology (MTE) has emphasized the potential for metabolism to serve as a unified theory of ecology, while focusing primarily on the size and temperature dependence of whole-organism metabolic rates. Generalizing metabolic ecology requires extending beyond prediction and application of standardized metabolic rates to theory focused on how energy moves through ecological systems. A bibliometric and network analysis of recent metabolic ecology literature reveals a research network characterized by major clusters focused on MTE, foraging theory, bioenergetics, trophic status, and generalized patterns and predictions. This generalized research network, which we refer to as metabolic ecology, can be considered to include the scaling, temperature and stoichiometric models forming the core of MTE, as well as bioenergetic equations, foraging theory, life-history allocation models, consumer-resource equations, food web theory and energy-based macroecology models that are frequently employed in ecological literature. We conclude with six points we believe to be important to the advancement and integration of metabolic ecology, including nomination of a second fundamental equation, complementary to the first fundamental equation offered by the MTE. PMID:24028511

  8. The ecological and evolutionary stability of interspecific territoriality.

    PubMed

    Losin, Neil; Drury, Jonathan P; Peiman, Kathryn S; Storch, Chaya; Grether, Gregory F

    2016-03-01

    Interspecific territoriality may play an important role in structuring ecological communities, but the causes of this widespread form of interference competition remain poorly understood. Here, we investigate the phenotypic, ecological and phylogenetic correlates of interspecific territoriality in wood warblers (Parulidae). Interspecifically territorial species have more recent common ancestors and are more similar phenotypically, and are more likely to hybridise, than sympatric, non-interspecifically territorial species. After phylogenetic corrections, however, similarity in plumage and territorial song are the only significant predictors of interspecific territoriality besides syntopy (fine-scale geographic overlap). Our results do not support the long-standing hypothesis that interspecific territoriality occurs only under circumstances in which niche divergence is restricted, which combined with the high incidence of interspecific territoriality in wood warblers (39% of species), suggests that this interspecific interaction is more stable, ecologically and evolutionarily, than commonly assumed. PMID:26757047

  9. Genomic Divergence during Speciation Driven by Adaptation to Altitude

    PubMed Central

    Chapman, Mark A.; Hiscock, Simon J.; Filatov, Dmitry A.

    2013-01-01

    Even though Darwin’s “On the Origin of Species” implied selection being the main driver of species formation, the role of natural selection in speciation remains poorly understood. In particular, it remains unclear how selection at a few genes can lead to genomewide divergence and the formation of distinct species. We used a particularly attractive clear-cut case of recent plant ecological speciation to investigate the demography and genomic bases of species formation driven by adaptation to contrasting conditions. High-altitude Senecio aethnensis and low-altitude S. chrysanthemifolius live at the extremes of a mountain slope on Mt. Etna, Sicily, and form a hybrid zone at intermediate altitudes but remain morphologically distinct. Genetic differentiation of these species was analyzed at the DNA polymorphism and gene expression levels by high-throughput sequencing of transcriptomes from multiple individuals. Out of ∼18,000 genes analyzed, only a small number (90) displayed differential expression between the two species. These genes showed significantly elevated species differentiation (FST and Dxy), consistent with diversifying selection acting on these genes. Genomewide genetic differentiation of the species is surprisingly low (FST = 0.19), while ∼200 genes showed significantly higher (false discovery rate < 1%; mean outlier FST > 0.6) interspecific differentiation and evidence for local adaptation. Diversifying selection at only a handful of loci may be enough for the formation and maintenance of taxonomically well-defined species, despite ongoing gene flow. This provides an explanation of why many closely related species (in plants, in particular) remain phenotypically and ecologically distinct despite ongoing hybridization, a question that has long puzzled naturalists and geneticists alike. PMID:24077768

  10. Reactions by army ant workers to nestmates having had contact with sympatric ant species.

    PubMed

    Dejean, Alain; Corbara, Bruno

    2014-11-01

    It was recently shown that Pheidole megacephala colonies (an invasive species originating from Africa) counterattack when raided by the army ant, Eciton burchellii. The subsequent contact permits Pheidole cuticular compounds (that constitute the "colony odour") to be transferred onto the raiding Eciton, which are then not recognised by their colony-mates and killed. Using a simple method for transferring cuticular compounds, we tested if this phenomenon occurs for Neotropical ants. Eciton workers rubbed with ants from four sympatric species were released among their colony-mates. Individuals rubbed with Solenopsis saevissima or Camponotus blandus workers were attacked, but not those rubbed with Atta sexdens, Pheidole fallax or with colony-mates (control lot). So, the chemicals of certain sympatric ant species, but not others, trigger intra-colonial aggressiveness in Eciton. We conclude that prey-ant chemicals might have played a role in the evolution of army ant predatory behaviour, likely influencing prey specialization in certain cases. PMID:25444708

  11. Breeding habitat use by sympatric and allopatric populations of Wilson's Warblers and Yellow Warblers

    USGS Publications Warehouse

    Ruth, J.M.; Stanley, T.R.

    2002-01-01

    We studied Wilson's Warbler (Wilsonia pusilla) and Yellow Warbler (Dendroica petechia) habitat use in allopatric and sympatric populations in the Rocky Mountains of northern Colorado and southeastern Wyoming in order to better understand the different habitat needs and interactions of these two species. Foraging Wilson's Warblers and Yellow Warblers used very similar habitat, both selecting larger, more open shrubs. In spite of similar foraging habitat, comparisons of habitat use by the two species at the sympatric sites yielded no evidence of foraging habitat partitioning or exclusion. There was evidence of nesting habitat partitioning. Wilson's Warblers nested on the ground, with some evidence that they used smaller, more densely stemmed shrubs under which to nest. Yellow Warblers are shrub nesters and selected larger, more open shrubs in which to nest. Results provide no evidence that Yellow Warblers can be blamed for population declines in Wilson's Warblers.

  12. Taxonomic consequences of cryptic speciation in the Golden Whistler Pachycephala pectoralis complex in mainland southern Australia.

    PubMed

    Joseph, Leo; Nyári, Árpád S; Andersen, Michael J

    2014-01-01

    The Golden Whistler (Aves: Passeriformes: Pachycephalidae) Pachycephala pectoralis sensu lato has long played a key role in the development of the theory of allopatric speciation (Mayr 1932a, b; Mayr 1942; Galbraith 1956). The P. pectoralis species complex formerly comprised 60-70 nominal subspecies and so had a distribution spanning the Indo-Pacific (Boles 2007). More recent taxonomic treatments consider the complex as multiple species-level taxa largely circumscribed by geography (Dickinson and Christidis 2014; Gill and Donsker 2014). In Australia, the endemic species P. pectoralis sensu stricto is sympatric with the closely related Mangrove Golden Whistler P. melanura. However, as the latter's English name suggests, P. melanura is closely tied to mangroves in Australia, southeast New Guinea, and islets in the Bismarck Archipelago. Diagnostic plumage traits separating the two species are subtle: males of P. melanura have more extensively black tails and a greyer upper surface to the remiges, and females are usually yellower ventrally. All Pachycephala species, especially those in the P. pectoralis-melanura species complex, have recently become the focus of DNA sequence-based studies (Jønsson et al. 2008, 2014; Andersen et al. 2014). Data from most populations have now been analysed phylogenetically to better understand relationships and thus the history of evolution and speciation processes within and between both species. This has also been used in studies of the group's historical biogeography to provide information as to the age of taxa and their spread across oceanic archipelagos and continents (Jønsson et al. 2014). Here we discuss the taxonomic implications of a result that has emerged consistently and independently in these studies, concerning the systematics of the southern Australian populations in south-eastern and south-western Australia, both of which have been ascribed to P. p. fuliginosa since Galbraith (1956), and we show that the name P

  13. Demographic history of speciation in a Senecio altitudinal hybrid zone on Mt. Etna.

    PubMed

    Filatov, Dmitry A; Osborne, Owen G; Papadopulos, Alexander S T

    2016-06-01

    Hybrid zones typically form as a result of species coming into secondary contact, but can also be established in situ as an ecotonal hybrid zone, a situation which has been reported far less frequently. An altitudinal hybrid zone on Mount Etna between two ragwort species (the low elevation Senecio chrysanthemifolius and high elevation S. aethnensis) could potentially represent either of these possibilities. However, a scenario of secondary contact vs. speciation with gene flow has not been explicitly tested. Here, we test these alternatives and demonstrate that the data do not support secondary contact. Furthermore, we report that the previous analyses of speciation history of these species were based on admixed populations, which has led to inflated estimates of ongoing, interspecific gene flow. Our new analyses, based on 'pure' S. aethnensis and S. chrysanthemifolius populations, reveal gene exchange of less than one effective migrant per generation, a level low enough to allow the species to accumulate neutral, genomewide differences. Overall, our results are consistent with a scenario of speciation with gene flow and a divergence time which coincides with the rise of Mt. Etna to altitudes above 2000 m (~150 KY). Further work to quantify the role of adaptation to contrasting environments of high and low altitudes will be needed to support the scenario of recent ecological speciation in this system. PMID:26994342

  14. Mimetic Divergence and the Speciation Continuum in the Mimic Poison Frog Ranitomeya imitator.

    PubMed

    Twomey, Evan; Vestergaard, Jacob S; Venegas, Pablo J; Summers, Kyle

    2016-02-01

    While divergent ecological adaptation can drive speciation, understanding the factors that facilitate or constrain this process remains a major goal in speciation research. Here, we study two mimetic transition zones in the poison frog Ranitomeya imitator, a species that has undergone a Müllerian mimetic radiation to establish four morphs in Peru. We find that mimetic morphs are strongly phenotypically differentiated, producing geographic clines with varying widths. However, distinct morphs show little neutral genetic divergence, and landscape genetic analyses implicate isolation by distance as the primary determinant of among-population genetic differentiation. Mate choice experiments suggest random mating at the transition zones, although certain allopatric populations show a preference for their own morph. We present evidence that this preference may be mediated by color pattern specifically. These results contrast with an earlier study of a third transition zone, in which a mimetic shift was associated with reproductive isolation. Overall, our results suggest that the three known mimetic transition zones in R. imitator reflect a speciation continuum, which we have characterized at the geographic, phenotypic, behavioral, and genetic levels. We discuss possible explanations for variable progress toward speciation, suggesting that multifarious selection on both mimetic color pattern and body size may be responsible for generating reproductive isolation. PMID:26807748

  15. What mechanism of niche segregation allows the coexistence of sympatric sibling rhinolophid bats?

    PubMed Central

    2012-01-01

    Introduction Our purpose was to assess how pairs of sibling horseshoe bats coexists when their morphology and echolocation are almost identical. We collected data on echolocation, wing morphology, diet, and habitat use of sympatric Rhinolophus mehelyi and R. euryale. We compared our results with literature data collected in allopatry with similar protocols and at the same time of the year (breeding season). Results Echolocation frequencies recorded in sympatry for R. mehelyi (mean = 106.8 kHz) and R. euryale (105.1 kHz) were similar to those reported in allopatry (R. mehelyi 105–111 kHz; R. euryale 101–109 kHz). Wing parameters were larger in R. mehelyi than R. euryale for both sympatric and allopatric conditions. Moths constitute the bulk of the diet of both species in sympatry and allopatry, with minor variation in the amounts of other prey. There were no inter-specific differences in the use of foraging habitats in allopatry in terms of structural complexity, however we found inter-specific differences between sympatric populations: R. mehelyi foraged in less complex habitats. The subtle inter-specific differences in echolocation frequency seems to be unlikely to facilitate dietary niche partitioning; overall divergences observed in diet may be explained as a consequence of differential prey availability among foraging habitats. Inter-specific differences in the use of foraging habitats in sympatry seems to be the main dimension for niche partitioning between R. mehelyi and R. euryale, probably due to letter differences in wing morphology. Conclusions Coexistence between sympatric sibling horseshoe bats is likely allowed by a displacement in spatial niche dimension, presumably due to the wing morphology of each species, and shifts the niche domains that minimise competition. Effective measures for conservation of sibling/similar horseshoe bats should guarantee structural diversity of foraging habitats. PMID:23148596

  16. Niche partitioning between sympatric rhesus macaques and Yunnan snub-nosed monkeys at Baimaxueshan Nature Reserve, China.

    PubMed

    Grueter, Cyril C; Li, Da-Yong; Feng, Shun-Kai; Ren, Bao-Ping

    2010-10-01

    Here we provide a preliminary assessment of dietary and habitat requirements of two sympatric primate taxa, a "simple-stomached" and "complex-stomached" species (Rhinopithecus bieti Colobinae vs. Macaca mulatta Cercopithecinae), as a basis for illuminating how the two coexist. Of ca. 22 plant food species consumed by the macaques, at least 16 were also eaten by the snub-nosed monkeys. Both species showed a preference for fruits. While the snub-nosed monkeys did not utilize any resources associated with human communities, rhesus macaques did occasionally raid agricultural crops. The mean elevation of the snub-nosed monkey group was 3,218 m, while the mean elevation of the macaque group was 2,995 m. Macaques were also spotted on meadows whereas snub-nosed monkeys evidently avoided these. For both species, mixed deciduous broadleaf/conifer forest was the most frequently used ecotype, but whereas evergreen broadleaf forest (Cyclobalanopsis community) accounted for only 3% of the location records of the snub-nosed monkeys, it accounted for 36% of the location records of the macaques. Groups of the two species usually kept a considerable spatial distance from one another (mean 2.4 km). One close encounter and confrontation between groups of the two species resulted in the macaque group moving away. Our findings suggest that the coexistence of the two taxa is facilitated via differential macrohabitat use and spatial avoidance. Although divergent habitat-use strategies may reflect interspecific competition, they may also merely reflect different physiological or ecological requirements. PMID:20979254

  17. Trophic niches of sympatric tropical tuna in the Western Indian Ocean inferred by stable isotopes and neutral fatty acids

    NASA Astrophysics Data System (ADS)

    Sardenne, Fany; Bodin, Nathalie; Chassot, Emmanuel; Amiel, Aurélien; Fouché, Edwin; Degroote, Maxime; Hollanda, Stéphanie; Pethybridge, Heidi; Lebreton, Benoit; Guillou, Gaël; Ménard, Frédéric

    2016-08-01

    This study examined the trophic ecology of three sympatric tropical tuna species (bigeye BET, skipjack SKJ, and yellowfin YFT) sampled in the Western Indian Ocean throughout 2013. Specifically we explored inter-specific resource partitioning and ontogenetic variability using neutral fatty acids and stable isotope analysis of liver and muscle from small (⩽100 cm fork length, FL) and large (>100 cm FL) tuna collected in mixed schools at the surface by purse-seine. Both biochemical tracers were used to calculate trophic niche indices that collectively revealed high potential for resource overlap, especially among small tuna. Resource overlap appeared strongest between BET and YFT, with SKJ tissues having high carbon isotope (δ13C) values (-17 ± 0.3‰), lower nitrogen isotope (δ15N) values (11.4 ± 0.6‰), and higher relative proportion of poly-unsaturated fatty acids (PUFA) than the two other species, indicating a different diet. Size was found to be a strong predictor for most biochemical tracers in the three species with δ13C, δ15N and total lipid content in the liver. In the larger species (YFT and BET), proportions of mono-unsaturated fatty acids typically increased with size, while quantities of PUFA decreased. In addition to ontogenetic variability, trophic markers were shown to vary between sampling area and season: higher lipid reserves and δ15N values, and lower δ13C values occurred during monsoon periods around Seychelles than in the Mozambique Channel (parted from about 1500 km). Our multi-tracer approach reveals the magnitude of potential competitive interactions in mixed tropical tuna schools at both small and large sizes and demonstrates that ontogenetic niche differentiation acts as a major factor of coexistence in tropical tuna.

  18. Phenotypic Plasticity of the Introduced New Zealand Mud Snail, Potamopyrgus antipodarum, Compared to Sympatric Native Snails

    PubMed Central

    Levri, Edward P.; Krist, Amy C.; Bilka, Rachel; Dybdahl, Mark F.

    2014-01-01

    Phenotypic plasticity is likely to be important in determining the invasive potential of a species, especially if invasive species show greater plasticity or tolerance compared to sympatric native species. Here in two separate experiments we compare reaction norms in response to two environmental variables of two clones of the New Zealand mud snail, Potamopyrgus antipodarum, isolated from the United States, (one invasive and one not yet invasive) with those of two species of native snails that are sympatric with the invader, Fossaria bulimoides group and Physella gyrina group. We placed juvenile snails in environments with high and low conductivity (300 and 800 mS) in one experiment, and raised them at two different temperatures (16°C and 22°C) in a second experiment. Growth rate and mortality were measured over the course of 8 weeks. Mortality rates were higher in the native snails compared to P. antipodarum across all treatments, and variation in conductivity influenced mortality. In both experiments, reaction norms did not vary significantly between species. There was little evidence that the success of the introduced species is a result of greater phenotypic plasticity to these variables compared to the sympatric native species. PMID:24699685

  19. Pollination patterns limit hybridization between two sympatric species of Narcissus (Amaryllidaceae).

    PubMed

    Marques, Isabel; Rosselló-Graell, Antònia; Draper, David; Iriondo, José M

    2007-08-01

    Natural hybrids between rare and common sympatric species are commonly eradicated to avoid the potential extinction of the rare species, although there is currently no clear predictive framework to quantify this risk. As hybrids can have intrinsic value as new evolutionary pathways, further knowledge on the factors controlling hybridization is needed. In this study we evaluated the role of pollination patterns in hybridization events in two sympatric populations of Narcissus cavanillesii and N. serotinus in Portugal. Narcissus cavanillesii is a rare species, while N. serotinus is widely distributed across the Mediterranean. The hybrid, N. ×perezlarae, is quite frequent in southeastern Spain but is scarce in Portugal. Reciprocal manual crossings confirmed compatibility between the two species, although hybridization was more successful when N. cavanillesii participated as female. Narcissus cavanillesii and N. serotinus only shared one pollinator, Megachile sp. (Hymenoptera), which had low visitation rates and high flower constancy. No single isolation mechanism was fully effective in preventing hybridization. Temporal displacement of flowering peaks, strong pollinator specificity, and high flower constancy in the shared pollinator all contributed to limiting hybridization in this site. In other sympatric occurrences, different phenological windows and pollination assemblages may allow greater frequency of the hybrid. PMID:21636503

  20. Increasing evidence of the role of gene flow in animal evolution: hybrid speciation in the yellow-rumped warbler complex.

    PubMed

    Jacobsen, Frode; Omland, Kevin E

    2011-06-01

    In this issue of Molecular Ecology, Brelsford et al. (2011) present strong evidence for a case of hybrid speciation within the yellow-rumped warbler complex. Although homoploid hybrid speciation has now been documented in many animals (Mallet 2007), it seems rare in tetrapods (Mavárez & Linares 2008) and it has barely even been mentioned in birds (Price 2008). Brelsford and colleagues thus present the first detailed molecular evidence suggesting that hybrid speciation can occur in birds. Brelsford et al. (2011) posit that Audubon's warbler (Dendroica auduboni) constitutes a hybrid species originating from the admixture of two distinct parental lineages, represented today by myrtle warbler (D. coronata) and black-fronted warbler (D. nigrifrons). The authors present three major lines of molecular evidence suggesting that this is not simply a case of a hybrid swarm or limited introgression. PMID:21739625

  1. Learning to speciate: The biased learning of mate preferences promotes adaptive radiation.

    PubMed

    Gilman, R Tucker; Kozak, Genevieve M

    2015-11-01

    Bursts of rapid repeated speciation called adaptive radiations have generated much of Earth's biodiversity and fascinated biologists since Darwin, but we still do not know why some lineages radiate and others do not. Understanding what causes assortative mating to evolve rapidly and repeatedly in the same lineage is key to understanding adaptive radiation. Many species that have undergone adaptive radiations exhibit mate preference learning, where individuals acquire mate preferences by observing the phenotypes of other members of their populations. Mate preference learning can be biased if individuals also learn phenotypes to avoid in mates, and shift their preferences away from these avoided phenotypes. We used individual-based computational simulations to study whether biased and unbiased mate preference learning promotes ecological speciation and adaptive radiation. We found that ecological speciation can be rapid and repeated when mate preferences are biased, but is inhibited when mate preferences are learned without bias. Our results suggest that biased mate preference learning may play an important role in generating animal biodiversity through adaptive radiation. PMID:26459795

  2. The Genome of the "Great Speciator" Provides Insights into Bird Diversification.

    PubMed

    Cornetti, Luca; Valente, Luis M; Dunning, Luke T; Quan, Xueping; Black, Richard A; Hébert, Olivier; Savolainen, Vincent

    2015-09-01

    Among birds, white-eyes (genus Zosterops) have diversified so extensively that Jared Diamond and Ernst Mayr referred to them as the "great speciator." The Zosterops lineage exhibits some of the fastest rates of species diversification among vertebrates, and its members are the most prolific passerine island colonizers. We present a high-quality genome assembly for the silvereye (Zosterops lateralis), a white-eye species consisting of several subspecies distributed across multiple islands. We investigate the genetic basis of rapid diversification in white-eyes by conducting genomic analyses at varying taxonomic levels. First, we compare the silvereye genome with those of birds from different families and searched for genomic features that may be unique to Zosterops. Second, we compare the genomes of different species of white-eyes from Lifou island (South Pacific), using whole genome resequencing and restriction site associated DNA. Third, we contrast the genomes of two subspecies of silvereye that differ in plumage color. In accordance with theory, we show that white-eyes have high rates of substitutions, gene duplication, and positive selection relative to other birds. Below genus level, we find that genomic differentiation accumulates rapidly and reveals contrasting demographic histories between sympatric species on Lifou, indicative of past interspecific interactions. Finally, we highlight genes possibly involved in color polymorphism between the subspecies of silvereye. By providing the first whole-genome sequence resources for white-eyes and by conducting analyses at different taxonomic levels, we provide genomic evidence underpinning this extraordinary bird radiation. PMID:26338191

  3. Ecological Consultancy

    ERIC Educational Resources Information Center

    Wilson, Scott McG.; Tattersfield, Peter

    2004-01-01

    This is the first of a new regular feature on careers, designed to provide those who teach biology with some inspiration when advising their students. In this issue, two consultant ecologists explain how their career paths developed. It is a misconception that there are few jobs in ecology. Over the past 20 or 30 years ecological consultancy has…

  4. Differences in trophic position among sympatric sea urchin species

    NASA Astrophysics Data System (ADS)

    Vanderklift, Mathew A.; Kendrick, Gary A.; Smit, Albertus J.

    2006-01-01

    Three species of sea urchin regularly co-occur in high abundances on subtidal rocky reefs in south-western Australia. We used two lines of evidence (stable isotope analysis and gut contents analysis), to test whether these species occupy different trophic positions. We looked at five discrete populations to test whether patterns were consistent. The gut contents of Heliocidaris erythrogramma contained almost exclusively fragments of macroalgae, and the δ15N of muscle was consistent with that expected for a herbivore. In contrast, the gut contents of Phyllacanthus irregularis and Centrostephanus tenuispinus contained a greater proportion of animal tissue, and the δ15N of muscle suggested that animal tissue was an important source of nutrition. Of the three co-occurring sea urchin species, one ( H. erythrogramma) was ecologically dissimilar to the others and occupied a lower trophic position. This pattern was consistent among populations separated by up to 270 km in south-western Australia. Food resource partitioning might be one way in which these species are able to coexist.

  5. A species pair of Bivesicula Yamaguti, 1934 (Trematoda: Bivesiculidae) in unrelated Great Barrier Reef fishes: implications for the basis of speciation in coral reef fish trematodes.

    PubMed

    Trieu, Nancy; Cutmore, Scott C; Miller, Terrence L; Cribb, Thomas H

    2015-07-01

    Combined morphological and molecular analysis shows that a species of Bivesicula Yamaguti, 1934 from four species of Apogonidae Günther [Nectamia fusca (Quoy & Gaimard), Ostorhinchus angustatus (Smith & Radcliffe), O. cookii (Macleay) and Taeniamia fucata (Cantor)] on the Great Barrier Reef is morphologically similar to, but clearly distinct from B. unexpecta Cribb, Bray & Barker, 1994 which infects a sympatric pomacentrid, Acanthochromis polyacanthus (Bleeker). Bivesicula neglecta n. sp. is proposed for the form from apogonids. Novel ITS2 rDNA sequences generated for the two species differ at just one consistent base position, implying that the two species are closely related. The combination of their close relationship, high but distinct specificity and co-occurrence suggests that speciation was driven by a recent host switching event enabled by similar dietary ecomorphology. PMID:26063300

  6. The ecology of sexual conflict: ecologically dependent parallel evolution of male harm and female resistance in Drosophila melanogaster.

    PubMed

    Arbuthnott, Devin; Dutton, Emily M; Agrawal, Aneil F; Rundle, Howard D

    2014-02-01

    The prevalence of sexual conflict in nature, along with the potentially stochastic nature of the resulting coevolutionary trajectories, makes it an important driver of phenotypic divergence and speciation that can operate even in the absence of environmental differences. The majority of empirical work investigating sexual conflict's role in population divergence/speciation has therefore been done in uniform environments and any role of ecology has largely been ignored. However, theory suggests that natural selection can constrain phenotypes influenced by sexual conflict. We use replicate populations of Drosophila melanogaster adapted to alternative environments to test how ecology influences the evolution of male effects on female longevity. The extent to which males reduce female longevity, as well as female resistance to such harm, both evolved in association with adaptation to the different environments. Our results demonstrate that ecology plays a central role in shaping patterns of population divergence in traits under sexual conflict. PMID:24215269

  7. Speciation, Divergence, and the Origin of Gryllus rubens: Behavior, Morphology, and Molecules

    PubMed Central

    Gray, David A.

    2011-01-01

    The last 25 years or so has seen a huge resurgence of interest in speciation research. This has coincided with the development and widespread use of new tools in molecular genetics, especially DNA sequencing, to inform ecological and evolutionary questions. Here I review about a decade of work on the sister species of field crickets Gryllus texensis and G. rubens. This work has included analysis of morphology, behavior, and the mitochondrial DNA molecule. The molecular work in particular has dramatically re-shaped my interpretation of the speciational history of these taxa, suggesting that rather than ‘sister’ species we should consider these taxa as ‘mother-daughter’ species with G. rubens derived from within a subset of ancestral G. texensis. PMID:26467622

  8. Speciation by Symbiosis: the Microbiome and Behavior

    PubMed Central

    Shropshire, J. Dylan

    2016-01-01

    ABSTRACT Species are fundamental units of comparison in biology. The newly discovered importance and ubiquity of host-associated microorganisms are now stimulating work on the roles that microbes can play in animal speciation. We previously synthesized the literature and advanced concepts of speciation by symbiosis with notable attention to hybrid sterility and lethality. Here, we review recent studies and relevant data on microbes as players in host behavior and behavioral isolation, emphasizing the patterns seen in these analyses and highlighting areas worthy of additional exploration. We conclude that the role of microbial symbionts in behavior and speciation is gaining exciting traction and that the holobiont and hologenome concepts afford an evolving intellectual framework to promote research and intellectual exchange between disciplines such as behavior, microbiology, genetics, symbiosis, and speciation. Given the increasing centrality of microbiology in macroscopic life, microbial symbiosis is arguably the most neglected aspect of animal and plant speciation, and studying it should yield a better understanding of the origin of species. PMID:27034284

  9. Speciation by Symbiosis: the Microbiome and Behavior.

    PubMed

    Shropshire, J Dylan; Bordenstein, Seth R

    2016-01-01

    Species are fundamental units of comparison in biology. The newly discovered importance and ubiquity of host-associated microorganisms are now stimulating work on the roles that microbes can play in animal speciation. We previously synthesized the literature and advanced concepts of speciation by symbiosis with notable attention to hybrid sterility and lethality. Here, we review recent studies and relevant data on microbes as players in host behavior and behavioral isolation, emphasizing the patterns seen in these analyses and highlighting areas worthy of additional exploration. We conclude that the role of microbial symbionts in behavior and speciation is gaining exciting traction and that the holobiont and hologenome concepts afford an evolving intellectual framework to promote research and intellectual exchange between disciplines such as behavior, microbiology, genetics, symbiosis, and speciation. Given the increasing centrality of microbiology in macroscopic life, microbial symbiosis is arguably the most neglected aspect of animal and plant speciation, and studying it should yield a better understanding of the origin of species. PMID:27034284

  10. Historical biogeography and speciation in the reef fish genus Haemulon (Teleostei: Haemulidae).

    PubMed

    Rocha, Luiz A; Lindeman, Kenyon C; Rocha, Claudia R; Lessios, H A

    2008-09-01

    The high biodiversity of tropical marine hotspots has long intrigued evolutionary biologists and biogeographers. The genus Haemulon (grunts) is one of the most important (numerically, ecologically, and economically) reef fish groups in the New World and an excellent candidate to test hypotheses of speciation and diversity generation in the Greater Caribbean, the richest Atlantic biodiversity hotspot, as well as the eastern Pacific. To elucidate the phylogenetic relationships among the species of Haemulon, we obtained a combined total of 2639 base pairs from two mitochondrial genes (cytochrome b and cytochrome oxidase I), and two nuclear genes (TMO-4C4 and RAG2) from all nominal species. Parsimony, Maximum likelihood, and Bayesian analyses resulted in a well-resolved phylogeny with almost identical topologies. Previous phylogenetic hypotheses based on adult morphology, such as the close relationship among H. aurolineatum, H. boschmae, and H. striatum were not supported, whereas others using developmental characters, such as the relationship between H. plumieri and H. sciurus, were confirmed. Our data also indicate that the populations of the nominal H. steindachneri from the two sides of the Isthmus of Panama are genetically divergent at the species level in each ocean, and that the boga, Inermia vittata (family Inermiidae), belongs in the genus Haemulon. This evidence implies that there are 21 valid species of Haemulon, two more than previously recognized. The Amazon barrier and the Isthmus of Panama seem to have played roles in allopatric speciation of Haemulon. However, the majority of sister species pairs have completely overlapping distributions, indicating that vicariance is not the only process driving speciation in this genus. We conclude that both vicariance between biogeographic provinces, and ecological mechanisms of speciation within provinces contribute to species richness in the genus Haemulon. PMID:18599320

  11. Hydroxyl speciation in felsic magmas

    NASA Astrophysics Data System (ADS)

    Malfait, Wim J.; Xue, Xianyu

    2014-09-01

    The hydroxyl speciation of hydrous, metaluminous potassium and calcium aluminosilicate glasses was investigated by 27Al-1H cross polarization and quantitative 1H MAS NMR spectroscopy. Al-OH is present in both the potassium and the calcium aluminosilicate glasses and its 1H NMR partial spectrum was derived from the 27Al-1H cross polarization data. For the calcium aluminosilicate glasses, the abundance of Al-OH could not be determined because of the low spectral resolution. For the potassium aluminosilicate glasses, the fraction of Al-OH was quantified by fitting its partial spectrum to the quantitative 1H NMR spectra. The degree of aluminum avoidance and the relative tendency for Si-O-Si, Si-O-Al and Al-O-Al bonds to hydrolyze were derived from the measured species abundances. Compared to the sodium, lithium and calcium systems, potassium aluminosilicate glasses display a much stronger degree of aluminum avoidance and a stronger tendency for the Al-O-Al linkages to hydrolyze. Combining our results with those for sodium aluminosilicate glasses (Malfait and Xue, 2010a), we predict that the hydroxyl groups in rhyolitic and phonolitic magmas are predominantly present as Si-OH (84-89% and 68-78%, respectively), but with a significant fraction of Al-OH (11-16% and 22-32%, respectively). For both rhyolitic and phonolitic melts, the AlOH/(AlOH + SiOH) ratio is likely smaller than the Al/(Al + Si) ratio for the lower end of the natural temperature range but may approach the Al/(Al + Si) ratio at higher temperatures.

  12. Ecological Inference

    NASA Astrophysics Data System (ADS)

    King, Gary; Rosen, Ori; Tanner, Martin A.

    2004-09-01

    This collection of essays brings together a diverse group of scholars to survey the latest strategies for solving ecological inference problems in various fields. The last half-decade has witnessed an explosion of research in ecological inference--the process of trying to infer individual behavior from aggregate data. Although uncertainties and information lost in aggregation make ecological inference one of the most problematic types of research to rely on, these inferences are required in many academic fields, as well as by legislatures and the Courts in redistricting, by business in marketing research, and by governments in policy analysis.

  13. Complex speciation of humans and chimpanzees.

    PubMed

    Wakeley, John

    2008-03-13

    Genetic data from two or more species provide information about the process of speciation. In their analysis of DNA from humans, chimpanzees, gorillas, orangutans and macaques (HCGOM), Patterson et al. suggest that the apparently short divergence time between humans and chimpanzees on the X chromosome is explained by a massive interspecific hybridization event in the ancestry of these two species. However, Patterson et al. do not statistically test their own null model of simple speciation before concluding that speciation was complex, and--even if the null model could be rejected--they do not consider other explanations of a short divergence time on the X chromosome. These include natural selection on the X chromosome in the common ancestor of humans and chimpanzees, changes in the ratio of male-to-female mutation rates over time, and less extreme versions of divergence with gene flow (see ref. 2, for example). I therefore believe that their claim of hybridization is unwarranted. PMID:18337768

  14. Monte Carlo simulations of parapatric speciation

    NASA Astrophysics Data System (ADS)

    Schwämmle, V.; Sousa, A. O.; de Oliveira, S. M.

    2006-06-01

    Parapatric speciation is studied using an individual-based model with sexual reproduction. We combine the theory of mutation accumulation for biological ageing with an environmental selection pressure that varies according to the individuals geographical positions and phenotypic traits. Fluctuations and genetic diversity of large populations are crucial ingredients to model the features of evolutionary branching and are intrinsic properties of the model. Its implementation on a spatial lattice gives interesting insights into the population dynamics of speciation on a geographical landscape and the disruptive selection that leads to the divergence of phenotypes. Our results suggest that assortative mating is not an obligatory ingredient to obtain speciation in large populations at low gene flow.

  15. SPECIATE Version 4.4 Database Development Documentation

    EPA Science Inventory

    SPECIATE is the U.S. Environmental Protection Agency’s (EPA) repository of volatile organic gas and particulate matter (PM) speciation profiles of air pollution sources. Some of the many uses of these source profiles include: (1) creating speciated emissions inventories for regi...

  16. EPAs SPECIATE 4.4 Database: Development and Uses

    EPA Science Inventory

    SPECIATE is the U.S. Environmental Protection Agency’s (EPA) repository of source category-specific particulate matter (PM), volatile organic gas, and other gas speciation profiles of air pollutant emissions. Abt Associates, Inc. developed SPECIATE 4.4 through a collaborat...

  17. Chemical Speciation and Quantitative Evaluation of Heavy Metal Pollution Hazards in Two Army Shooting Range Backstop Soils.

    PubMed

    Islam, Mohammad Nazrul; Nguyen, Xuan Phuc; Jung, Ho-Young; Park, Jeong-Hun

    2016-02-01

    The chemical speciation and ecological risk assessment of heavy metals in two shooting range backstop soils in Korea were studied. Both soils were highly contaminated with Cd, Cu, Pb, and Sb. The chemical speciation of heavy metals reflected the present status of contamination, which could help in promoting management practices. We-rye soil had a higher proportion of exchangeable and carbonate bound metals and water-extractable Cd and Sb than the Cho-do soil. Bioavailable Pb represented 42 % of the total Pb content in both soils. A significant amount of Sb was found in the two most bioavailable fractions, amounting to ~32 % in the soil samples, in good agreement with the batch leaching test using water. Based on the values of ecological risk indices, both soils showed extremely high potential risk and may represent serious environmental problems. PMID:26546228

  18. Boechera, a model system for ecological genomics

    PubMed Central

    Rushworth, Catherine A.; Song, Bao-Hua; Lee, Cheng-Ruei; Mitchell-Olds, Thomas

    2011-01-01

    The selection and development of a study system for evolutionary and ecological functional genomics (EEFG) depends on a variety of factors. Here we present the genus Boechera as an exemplary system with which to address ecological and evolutionary questions. Our focus on Boechera is based on several characteristics: 1) native populations in undisturbed habitats where current environments reflect historical conditions over several thousand years; 2) functional genomics benefitting from its close relationship to Arabidopsis thaliana; 3) inbreeding tolerance enabling development of recombinant inbred lines, near-isogenic lines, and positional cloning; 4) interspecific crosses permitting mapping for genetic analysis of speciation; 5) apomixis (asexual reproduction by seeds) in a genetically tractable diploid; and 6) broad geographic distribution in North America, permitting ecological genetics for a large research community. These characteristics, along with the current sequencing of three Boechera species by the Joint Genome Institute, position Boechera as a rapidly advancing system for EEFG studies. PMID:22059452

  19. Boechera, a model system for ecological genomics.

    PubMed

    Rushworth, Catherine A; Song, Bao-Hua; Lee, Cheng-Ruei; Mitchell-Olds, Thomas

    2011-12-01

    The selection and development of a study system for evolutionary and ecological functional genomics (EEFG) depend on a variety of factors. Here, we present the genus Boechera as an exemplary system with which to address ecological and evolutionary questions. Our focus on Boechera is based on several characteristics as follows: (i) native populations in undisturbed habitats where current environments reflect historical conditions over several thousand years; (ii) functional genomics benefitting from its close relationship to Arabidopsis thaliana; (iii) inbreeding tolerance enabling development of recombinant inbred lines, near-isogenic lines and positional cloning; (iv) interspecific crosses permitting mapping for genetic analysis of speciation; (v) apomixis (asexual reproduction by seeds) in a genetically tractable diploid; and (vi) broad geographic distribution in North America, permitting ecological genetics for a large research community. These characteristics, along with the current sequencing of three Boechera species by the Joint Genome Institute, position Boechera as a rapidly advancing system for EEFG studies. PMID:22059452

  20. The species concept in phytoplankton ecology

    SciTech Connect

    Wood, A.M.; Leatham, T. )

    1992-12-01

    The authors discuss the broad aspects and difficulties of phytoplankton species identification. Phytoplankton ecology relies heavily on the use of taxon-insensitive indicies like chlorophyll a concentration, [sup 14]C incubations, and light-dark bottles for measurement of abundance and productivity. Numerous excellent studies have been done in comparative algal physiology, but none of them actually demonstrate species level differences in the traits of interest. Many of the studies underestimate genetic diversity within taxa because they rely on genotypes that can be cultured and maintained in the laboratory. Significant interclonal variablity is found every time that strains from the same putative taxon are compared, and the magnitude of these differences is not trivial. The authors follow this discussion by detailing several specific ways of approaching speciation in phytoplankton including identifying the ecological significance of morphological traits and ecologically important traits consistently correlated with mprphological features used to distinguish among speiceis or sub-species. 82 refs., 2 figs., 1 tab.

  1. Arsenic speciation in manufactured seafood products.

    PubMed

    Vélez, D; Montoro, R

    1998-09-01

    The literature on the speciation of arsenic (As) in seafoods was critically reviewed. Most research has been directed toward fresh seafood products with few papers dealing with As speciation in manufactured seafoods. Predictions concerning As species made on the basis of fresh seafood products cannot be extrapolated to manufactured seafoods. Therefore, due to the numerous species of As, the scarcity of data concerning their presence in foods, the transformations each species may undergo during industrial processing and cooking, and the lack of legislation on permitted As levels in seafood products, As species in manufactured seafood products need to be determined and quantified. PMID:9766084

  2. Instrumentation for Aerosol and Gas Speciation

    NASA Technical Reports Server (NTRS)

    Coggiola, Michael J.

    1998-01-01

    Using support from NASA Grant No. NAG 2-963, SRI International successfully completed the project, entitled, 'Instrumentation for Aerosol and Gas Speciation.' This effort (SRI Project 7383) covered the design, fabrication, testing, and deployment of a real-time aerosol speciation instrument in NASA's DC-8 aircraft during the Spring 1996 SUbsonic aircraft: Contrail and Cloud Effects Special Study (SUCCESS) mission. This final technical report describes the pertinent details of the instrument design, its abilities, its deployment during SUCCESS and the data acquired from the mission, and the post-mission calibration, data reduction, and analysis.

  3. Plasmodium vivax Populations Are More Genetically Diverse and Less Structured than Sympatric Plasmodium falciparum Populations

    PubMed Central

    Jennison, Charlie; Arnott, Alicia; Tessier, Natacha; Tavul, Livingstone; Koepfli, Cristian; Felger, Ingrid; Siba, Peter M.; Reeder, John C.; Bahlo, Melanie; Mueller, Ivo; Barry, Alyssa E.

    2015-01-01

    Introduction The human malaria parasite, Plasmodium vivax, is proving more difficult to control and eliminate than Plasmodium falciparum in areas of co-transmission. Comparisons of the genetic structure of sympatric parasite populations may provide insight into the mechanisms underlying the resilience of P. vivax and can help guide malaria control programs. Methodology/Principle findings P. vivax isolates representing the parasite populations of four areas on the north coast of Papua New Guinea (PNG) were genotyped using microsatellite markers and compared with previously published microsatellite data from sympatric P. falciparum isolates. The genetic diversity of P. vivax (He = 0.83–0.85) was higher than that of P. falciparum (He = 0.64–0.77) in all four populations. Moderate levels of genetic differentiation were found between P. falciparum populations, even over relatively short distances (less than 50 km), with 21–28% private alleles and clear geospatial genetic clustering. Conversely, very low population differentiation was found between P. vivax catchments, with less than 5% private alleles and no genetic clustering observed. In addition, the effective population size of P. vivax (30353; 13043–69142) was larger than that of P. falciparum (18871; 8109–42986). Conclusions/Significance Despite comparably high prevalence, P. vivax had higher diversity and a panmictic population structure compared to sympatric P. falciparum populations, which were fragmented into subpopulations. The results suggest that in comparison to P. falciparum, P. vivax has had a long-term large effective population size, consistent with more intense and stable transmission, and limited impact of past control and elimination efforts. This underlines suggestions that more intensive and sustained interventions will be needed to control and eventually eliminate P. vivax. This research clearly demonstrates how population genetic analyses can reveal deeper insight into transmission

  4. Satellite Tracking of Sympatric Marine Megafauna Can Inform the Biological Basis for Species Co-Management

    PubMed Central

    Gredzens, Christian; Marsh, Helene; Fuentes, Mariana M. P. B.; Limpus, Colin J.; Shimada, Takahiro; Hamann, Mark

    2014-01-01

    Context Systematic conservation planning is increasingly used to identify priority areas for protection in marine systems. However, ecosystem-based approaches typically use density estimates as surrogates for animal presence and spatial modeling to identify areas for protection and may not take into account daily or seasonal movements of animals. Additionally, sympatric and inter-related species are often managed separately, which may not be cost-effective. This study aims to demonstrate an evidence-based method to inform the biological basis for co-management of two sympatric species, dugongs and green sea turtles. This approach can then be used in conservation planning to delineate areas to maximize species protection. Methodology/Results Fast-acquisition satellite telemetry was used to track eleven dugongs and ten green turtles at two geographically distinct foraging locations in Queensland, Australia to evaluate the inter- and intra-species spatial relationships and assess the efficacy of existing protection zones. Home-range analysis and bathymetric modeling were used to determine spatial use and compared with existing protection areas using GIS. Dugong and green turtle home-ranges significantly overlapped in both locations. However, both species used different core areas and differences existed between regions in depth zone use and home-range size, especially for dugongs. Both species used existing protection areas in Shoalwater Bay, but only a single tracked dugong used the existing protection area in Torres Strait. Conclusions/Significance: Fast-acquisition satellite telemetry can provide evidence-based information on individual animal movements to delineate relationships between dugongs and green turtles in regions where they co-occur. This information can be used to increase the efficacy of conservation planning and complement more broadly based survey information. These species also use similar habitats, making complimentary co-management possible, but

  5. Gene Flow between Sympatric Life History Forms of Oncorhynchus mykiss Located above and below Migratory Barriers

    PubMed Central

    Van Doornik, Donald M.; Berejikian, Barry A.; Campbell, Lance A.

    2013-01-01

    Oncorhynchus mykiss have a diverse array of life history types, and understanding the relationship among types is important for management of the species. Patterns of gene flow between sympatric freshwater resident O. mykiss, commonly known as rainbow trout, and anadromous O. mykiss, commonly known as steelhead, populations are complex and poorly understood. In this study, we attempt to determine the occurrence and pathways of gene flow and the degree of genetic similarity between sympatric resident and anadromous O. mykiss in three river systems, and investigate whether resident O. mykiss are producing anadromous offspring in these rivers, two of which have complete barriers to upstream migration. We found that the population structure of the O. mykiss in these rivers appears to be influenced more by the presence of a barrier to upstream migration than by life history type. The sex ratio of resident O. mykiss located above a barrier, and smolts captured in screw traps was significantly skewed in favor of females, whereas the reverse was true below the barriers, suggesting that male resident O. mykiss readily migrate downstream over the barrier, and that precocious male maturation may be occurring in the anadromous populations. Through paternity analyses, we also provide direct confirmation that resident O. mykiss can produce offspring that become anadromous. Most (89%) of the resident O. mykiss that produced anadromous offspring were males. Our results add to the growing body of evidence that shows that gene flow does readily occur between sympatric resident and anadromous O. mykiss life history types, and indicates that resident O. mykiss populations may be a potential repository of genes for the anadromous life history type. PMID:24224023

  6. Toxicity, bioavailability and metal speciation.

    PubMed

    Jonnalagadda, S B; Rao, P V

    1993-11-01

    1. Environmental toxicology emphasizes the difference from traditional toxicology in which pure compounds of interest are added to purified diets, or injected into the test animals. When the objective is to study the fate and effects of trace elements in the environment, knowledge of the speciation of the elements and their physico-chemical forms is important. 2. Cadmium salts such as the sulfides, carbonates or oxides, are practically insoluble in water. However, these can be converted to water-soluble salts in nature under the influence of oxygen and acids. Chronic exposure to Cd is associated with renal toxicity in humans once a critical body burden is reached. 3. The solubility of As(III) oxide in water is fairly low, but high in either acid or alkali. In water, arsenic is usually in the form of the arsenate or arsenite. As(III) is systemically more poisonous than the As(V), and As(V) is reduced to the As(III) form before exerting any toxic effects. Organic arsenicals also exert their toxic effects in vivo in animals by first metabolizing to the trivalent arsenoxide form. Some methyl arsenic compounds, such as di- and trimethylarsines, occur naturally as a consequence of biological activity. The toxic effect of arsenite can be potentiated by dithiols, while As has a protective effect against the toxicity of a variety of forms of Se in several species. 4. Selenium occurs in several oxidation states and many selenium analogues of organic sulfur compounds exist in nature. Selenium in selenate form occurs in alkaline soils, where it is soluble and easily available to plants. Selenite binds tightly to iron and aluminum oxides and thus is quite insoluble in soils. Hydrogen selenide is a very toxic gas at room temperature. The methylated forms of Se are much less toxic for the organism than selenite. However, the methylated Se derivatives have strong synergistic toxicity with other minerals such as arsenic. 5. Aquatic organisms absorb and retain Hg in the tissues, as

  7. A field observation on color selection by New World sympatric primates, Pithecia pithecia and Alouatta seniculus.

    PubMed

    Urbani, Bernardo

    2002-04-01

    This work characterizes differences in selection of Talisia retusa fruits by two sympatric Neotropical primates, Pithecia pithecia (white-faced sakis) and Alouatta seniculus (red howlers). Color appears to be the criterion by which fruits were selected. Greenish fruits were mainly eaten by Pithecia, while yellowish fruits by Alouatta. The characteristics of these primates in relation to seed predation and seed dispersal are discussed in the context of the Talisia retusa fruit color spectrum. Furthermore, a possible differential acquisition of chemical components, like tannins, is hypothetically treated considering the variation in fruit color. PMID:12082298

  8. NICKEL SPECIATION OF RESIDUAL OIL ASH

    EPA Science Inventory

    EPA GRANT NUMBER: R827649C002
    Title: Nickel Speciation Of Residual Oil Ash
    Investigators: Kevin C. Galbreath, John Won, Frank E. Huggins, Gerald P. Huffman, Christopher J. Zygarlicke, Donald L. Toman
    Institution: University of North Dakota<...

  9. Speciation: Genomic Archipelagos in a Crater Lake.

    PubMed

    Ronco, Fabrizia; Salzburger, Walter

    2016-03-01

    The opening stages of speciation remain poorly understood, especially from a genomic perspective. The genomes of newly discovered crater-lake cichlid fish shed light on the early phases of diversification and suggest that selection acts on multiple genomic regions. PMID:26954438

  10. Biosensor for metal analysis and speciation

    DOEpatents

    Aiken, Abigail M.; Peyton, Brent M.; Apel, William A.; Petersen, James N.

    2007-01-30

    A biosensor for metal analysis and speciation is disclosed. The biosensor comprises an electron carrier immobilized to a surface of an electrode and a layer of an immobilized enzyme adjacent to the electrode. The immobilized enzyme comprises an enzyme having biological activity inhibited by a metal to be detected by the biosensor.

  11. Speciation of VOCs from Animal Feeding Operations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Environmental Pollution Agency (EPA) air consent agreement with animal feeding operations (AFO) specifies the use of EPA TO-15 for the speciation of volatile organic compounds (VOC) emitted from these facilities. However, compounds emitted from AFO are often both volatile and highly polar chara...

  12. Characterization of Technetium Speciation in Cast Stone

    SciTech Connect

    Um, Wooyong; Jung, Hun Bok; Wang, Guohui; Westsik, Joseph H.; Peterson, Reid A.

    2013-11-11

    This report describes the results from laboratory tests performed at Pacific Northwest National Laboratory (PNNL) for the U.S. Department of Energy (DOE) EM-31 Support Program (EMSP) subtask, “Production and Long-Term Performance of Low Temperature Waste Forms” to provide additional information on technetium (Tc) speciation characterization in the Cast Stone waste form. To support the use of Cast Stone as an alternative to vitrification for solidifying low-activity waste (LAW) and as the current baseline waste form for secondary waste streams at the Hanford Site, additional understanding of Tc speciation in Cast Stone is needed to predict the long-term Tc leachability from Cast Stone and to meet the regulatory disposal-facility performance requirements for the Integrated Disposal Facility (IDF). Characterizations of the Tc speciation within the Cast Stone after leaching under various conditions provide insights into how the Tc is retained and released. The data generated by the laboratory tests described in this report provide both empirical and more scientific information to increase our understanding of Tc speciation in Cast Stone and its release mechanism under relevant leaching processes for the purpose of filling data gaps and to support the long-term risk and performance assessments of Cast Stone in the IDF at the Hanford Site.

  13. ELEMENTAL SPECIATION IN ENVIRONMENTAL EXPOSURE ASSESSMENT MATRICES

    EPA Science Inventory

    Arsenic and tin are two trace metals where exposure assessments have moved towards a speciation based approach because the toxicity is very chemical form dependent. This toxicity difference can be one of many factors which influence the formulation of certain regulations. For a...

  14. Heavy metal speciation in the composting process.

    PubMed

    Greenway, Gillian M; Song, Qi Jun

    2002-04-01

    Composting is one of the more efficient and environment friendly methods of solid waste disposal and has many advantages when compared with landfill disposal on which the UK and Ireland are currently heavily dependent. Composting is a very complicated process involving intensive microbial activity and the detailed mechanisms of the process have yet to be fully understood. Metal speciation information can provide an insight into the metal-microbial interaction and would help in the evaluation of the quality of compost. This would facilitate the exploitation of composts in remediation of heavy metal contaminated land. In this work a systematic approach to metal speciation in compost has been taken by applying the three-step method for operationally defined metal speciation of soils and sediments, developed by the European Commission's Standards, Measurement and Testing Programme to monitor the change in metal speciation with time (up to 106 days) for four different waste composting processes. The results have shown that in general metals become less available for the first extraction step as the composting process proceeds. This implies that composting tends to redistribute the metals from more labile forms to more fixed forms which may explain why the application of composts could be useful for with heavy metal contaminated land. There are exceptions to this trend and in some cases, certain metals appear to behave differently depending on the source of the compost. PMID:11993774

  15. EFFECT OF SCR CATALYST ON MERCURY SPECIATION

    EPA Science Inventory

    A pilot-scale research study was conducted to investigate the effect of selective catalytic reduction (SCR) on elemental mercury speciation in bituminous and subbituminous coal combustion flue gases. Three different Illinois bituminous coals and one Powder River Basin (PRB) coal...

  16. ARSENIC SPECIATION ANALYSIS IN HUMAN SALIVA

    EPA Science Inventory

    Background: Determination of arsenic species in human saliva is potentially useful for biomonitoring of human exposure to arsenic and for studying arsenic metabolism. However, there is no report on the speciation analysis of arsenic in saliva. Methods: Arsenic species in saliva ...

  17. 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

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

    PubMed

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

    2011-09-01

    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

  19. Both Geography and Ecology Contribute to Mating Isolation in Guppies

    PubMed Central

    Schwartz, Amy K.; Weese, Dylan J.; Bentzen, Paul; Kinnison, Michael T.; Hendry, Andrew P.

    2010-01-01

    Local adaptation to different environments can promote mating isolation – either as an incidental by-product of trait divergence, or as a result of selection to avoid maladaptive mating. Numerous recent empirical examples point to the common influence of divergent natural selection on speciation based largely on evidence of strong pre-mating isolation between populations from different habitat types. Accumulating evidence for natural selection's influence on speciation is therefore no longer a challenge. The difficulty, rather, is in determining the mechanisms involved in the progress of adaptive divergence to speciation once barriers to gene flow are already present. Here, we present results of both laboratory and field experiments with Trinidadian guppies (Poecilia reticulata) from different environments, who do not show complete reproductive isolation despite adaptive divergence. We investigate patterns of mating isolation between populations that do and do not exchange migrants and show evidence for both by-product and reinforcement mechanisms depending on female ecology. Specifically, low-predation females discriminate against all high-predation males thus implying a by-product mechanism, whereas high-predation females only discriminate against low-predation males from further upstream in the same river, implying selection to avoid maladaptive mating. Our study thus confirms that mechanisms of adaptive speciation are not necessarily mutually exclusive and uncovers the complex ecology-geography interactions that underlie the evolution of mating isolation in nature. PMID:21179541

  20. Adding to the Mercury Speciation Toolbox

    NASA Astrophysics Data System (ADS)

    Fitts, J. P.; Northrup, P. A.; Chidambaram, D.; Kalb, P. D.

    2007-12-01

    Mercury was used to separate lithium-6 isotope for weapons production at the Y-12 Plant in Oak Ridge, TN in the 1950s and 1960s. A large portion of the waste Hg entered the environment and continues to move throughout the sub-surface and surface waters in the area. Environmental management of Hg contamination within this complex hydrologic system, where Hg speciation and the mobile fraction have been found to vary widely, will require ongoing characterization and predictive modeling of Hg speciation. State-of-the-art spectroscopic tools that can directly probe Hg speciation in preserved aqueous and sediment samples with greater sensitivity, however, are required to determine rates and mechanisms of biogeochemical reactions. We will present the first results demonstrating the use of x-ray absorption spectroscopy (XAS) at the Hg M5 edge (2295 eV) to fingerprint Hg species. Heavy-metal M5 absorption edges can have very sharp features due to local electron transitions, and therefore, we are developing this edge as a tool for quantitative measurement of Hg species. In addition, sulfur speciation using the sulfur K absorption edge, which is at a similar energy (2472 eV), can be measured in the same scan as the Hg M5 edge. Potentially important organic and inorganic sulfur species (sulfide, disulfide, elemental sulfur, sulfite and sulfate) are readily differentiated, and thereby, provides an independent method for monitoring the redox state of the system along with changes in S-Hg bonding. We will also present x-ray microprobe 2-D concentration maps of Hg and other elements at the grain and pore scales to identify its microscopic distribution and chemical associations. When used in combination with established sequential extraction and direct spectroscopic methods, the addition of XAS at the Hg M5 edge should provide a significant advancement in the determination of Hg speciation in complex biogeochemical environments.

  1. Genetic structure and hybridization in the species group of Ficus auriculata: can closely related sympatric Ficus species retain their genetic identity while sharing pollinators?

    PubMed

    Wei, Z-D; Kobmoo, N; Cruaud, A; Kjellberg, F

    2014-07-01

    Obligate mutualistic nursery pollination systems between insects and plants have led to substantial codiversification involving at least some parallel cladogenesis, as documented in Yucca, Ficus and Phyllanthaceae. In such systems, pollinators are generally species specific thus limiting hybridization and introgression among interfertile host species. Nevertheless, in the three systems, cases of one insect pollinating several plant species are reported. In most cases, host plants sharing pollinators are allopatric. However, in the case of the species group of Ficus auriculata, forms may co-occur over large parts of their range. We show here that the species group of F. auriculata is constituted by four well-defined genetic entities that share pollinators. We detected hybrids in nature mainly when both parental forms were growing nearby. Controlled crosses showed that F1 offspring could be successfully backcrossed. Hence, despite sharing pollinators and despite hybrid viability, the different forms have preserved their genetic and morphological identity. We propose that ecological differentiation among forms coupled with limited overlap of reproductive season has facilitated the maintenance of these interfertile forms. As such, establishment of pollinator host specificity may not be a prerequisite for sympatric diversification in Ficus. PMID:24938182

  2. Pollinator sharing and gene flow among closely related sympatric dioecious fig taxa.

    PubMed

    Wang, Gang; Cannon, Charles H; Chen, Jin

    2016-04-13

    Hybridization and insect pollination are widely believed to increase rates of plant diversification. The extreme diversity of figs (Ficus) and their obligate pollinators, fig wasps (Agaonidae), provides an opportunity to examine the possible role of pollinator-mediated hybridization in plant diversification. Increasing evidence suggests that pollinator sharing and hybridization occurs among fig taxa, despite relatively strict coevolution with the pollinating wasp. Using five sympatric dioecious fig taxa and their pollinators, we examine the degree of pollinator sharing and inter-taxa gene flow. We experimentally test pollinator preference for floral volatiles, the main host recognition signal, from different figs. All five fig taxa shared pollinators with other taxa, and gene flow occurred between fig taxa within and between sections. Floral volatiles of each taxon attracted more than one pollinator species. Floral volatiles were more similar between closely related figs, which experienced higher levels of pollinator sharing and inter-taxa gene flow. This study demonstrates that pollinator sharing and inter-taxa gene flow occurs among closely related sympatric dioecious fig taxa and that pollinators choose the floral volatiles of multiple fig taxa. The implications of pollinator sharing and inter-taxa gene flow on diversification, occurring even in this highly specialized obligate pollination system, require further study. PMID:27075252

  3. Reproductive isolation is mediated by pollen incompatibility in sympatric populations of two Arnebia species.

    PubMed

    Wang, Lin-Lin; Zhang, Chan; Tian, Bin; Sun, Xu-Dong; Guo, Wen; Zhang, Ting-Feng; Yang, Yong-Ping; Duan, Yuan-Wen

    2015-12-01

    To explore uncertain aspects of the processes that maintain species boundaries, we evaluated contributions of pre- and postpollination reproductive isolation mechanisms in sympatric populations of Arnebia guttata and A. szechenyi. For this, we investigated their phylogenetic relationships, traits, microenvironments, pollinator visits, action of natural selection on floral traits, and the outcome of hand pollination between the two species. Phylogenetic analysis indicates that A. szechenyi is a derived species that could be closely related to A. guttata, and both could be diploid species. Arnebia guttata flowers have larger parts than A. szechenyi flowers, but smaller nectar guides. Soil supporting A. szechenyi had higher water contents than soil supporting neighboring populations of A. guttata (in accordance with their geographical distributions). The pollinators shared by the two species preferred A. szechenyi flowers, but interspecific visitations were frequent. We found evidence of conflicting selection pressures on floral tube length, flower diameter and nectar guide size mediated via male fitness, and on flower diameter and floral tube diameter via female fitness. Hand-pollination experiments indicate complete pollen incompatibility between the two species. Our results suggest that postpollination prezygotic mechanisms are largely responsible for reproductive isolation of sympatric populations of the two Arnebia species. PMID:26811758

  4. Sympatric wolf and coyote populations of the western Great Lakes region are reproductively isolated.

    PubMed

    Wheeldon, Tyler J; Patterson, Brent R; White, Bradley N

    2010-10-01

    Interpretation of the genetic composition and taxonomic history of wolves in the western Great Lakes region (WGLR) of the United States has long been debated and has become more important to their conservation given the recent changes in their status under the Endangered Species Act. Currently, the two competing hypotheses on WGLR wolves are that they resulted from hybridization between (i) grey wolves (Canis lupus) and western coyotes (C. latrans) or (ii) between grey wolves and eastern wolves (C. lycaon). We performed a genetic analysis of sympatric wolves and coyotes from the region to assess the degree of reproductive isolation between them and to clarify the taxonomic status of WGLR wolves. Based on data from maternal, paternal and bi-parental genetic markers, we demonstrate a clear genetic distinction between sympatric wolves and coyotes and conclude that they are reproductively isolated and that wolf-coyote hybridization in the WGLR is uncommon. The data reject the hypothesis that wolves in the WGLR derive from hybridization between grey wolves and western coyotes, and we conclude that the extant WGLR wolf population is derived from hybridization between grey wolves and eastern wolves. Grey-eastern wolf hybrids (C. lupus × lycaon) comprise a substantial population that extends across Michigan, Wisconsin, Minnesota and western Ontario. These findings have important implications for the conservation and management of wolves in North America, specifically concerning the overestimation of grey wolf numbers in the United States and the need to address policies for hybrids. PMID:20854277

  5. Floral biology and reproductive isolation by floral scent in three sympatric aroid species in French Guiana.

    PubMed

    Hentrich, H; Kaiser, R; Gottsberger, G

    2010-07-01

    We studied the reproductive biology of three sympatric Araceae species, Anthurium sagittatum, A. thrinax and Spathiphyllum humboldtii in French Guiana. The plants flowered simultaneously and were visited by scent-collecting male euglossine bees, which were apparently their major pollinators. In total, each species was visited by 3-7 euglossine species, and 2-3 euglossine species accounted for at least 80% of all flower visits, with visits being plant species-specific. Floral scent consisted of 6-10 main compounds, which made up 76-94% of the total amount of volatiles and were specific in these high amounts to each plant species. We suggest that the different floral scents lead to clear separation of the main pollinating euglossine species, providing a directed and efficient intraspecific pollen flow that results in high reproductive success. Since the simple floral (inflorescence) morphology of the studied plants does not support any morphological mechanisms to exclude visitors, as for example in euglossine-pollinated perfume orchids, floral scent might be of major importance for the reproductive isolation and sympatric occurrence of these plants. PMID:20636901

  6. Dietary partitioning by five sympatric species of stingray (Dasyatidae) on coral reefs.

    PubMed

    O'Shea, O R; Thums, M; van Keulen, M; Kempster, R M; Meekan, M G

    2013-06-01

    Dietary characteristics and the degree of dietary partitioning by five species of sympatric stingray were assessed using stomach content and sediment analyses within a coral reef lagoon at Ningaloo Reef, Western Australia (the cowtail Pastinachus atrus, blue-spotted fantail Taeniura lymma, blue-spotted mask Neotrygon kuhlii, porcupine Urogymnus asperrimus rays and the reticulate whipray Himantura uarnak). A total of 2804 items were recovered from the stomachs of 170 rays and 3215 individual taxa from the environment, which were used in selectivity analyses. Twenty-four prey taxa were identified from stomach contents and pooled into 10 taxonomic categories for analysis, of which annelids, prawns, brachyurans and bivalves were the most abundant, together accounting for 96% of the diet. Himantura uarnak had the greatest interspecific dissimilarity in diet, consuming a larger proportion of crustaceans, notably penaeids (41% of total diet) than the other four species of rays, all of which had diets dominated by annelids (71-82% of total diet). Crustacean specialization by H. uarnak may exist to maximize resources and reduce competition among sympatric species. The remaining species may partition resources on the basis of space, rather than diet. PMID:23731138

  7. Reduction of potential food interference in two sympatric carnivores by sequential use of shared resources

    NASA Astrophysics Data System (ADS)

    Barrientos, Rafael; Virgós, Emilio

    2006-07-01

    The common genet ( Genetta genetta) and the stone marten ( Martes foina) are two species that overlap extensively in their distribution ranges in southwest Europe. Available diet data from these species allow us to predict some interference competition for food resources in sympatric populations. We checked the food interference hypothesis in a sympatric population. The diet of both predators was analyzed through scat collection. Seasonal differences in biomass consumption were compared between both species in those items considered as key resources according to biomass consumption. Strawberry tree fruits can be considered as key resource exclusively for genets whereas fungi, blackberries and rabbits are keys for stone martens only. For other key resources consumed by both species (wood mouse and figs) we suggest that a possible mechanism to reduce diet overlap could be the sequential use of these resources: no intensive exploitation by both species of the same key resource during the same season was detected. Figs and wood mouse were used alternatively. Although strawberry tree fruits and blackberry are exclusive key resources of one of the species, their consumptions showed the same pattern. Diet niche overlap in our study is low compared with other carnivore communities suggesting that exclusive use of some key resources and sequential use of shared ones is an optimal scenario to reduce overall competition for food resources.

  8. Dietary separation of sympatric carnivores identified by molecular analysis of scats.

    PubMed

    Farrell, L E; Roman, J; Sunquist, M E

    2000-10-01

    We studied the diets of four sympatric carnivores in the flooding savannas of western Venezuela by analysing predator DNA and prey remains in faeces. DNA was isolated and a portion of the cytochrome b gene of the mitochondrial genome amplified and sequenced from 20 of 34 scats. Species were diagnosed by comparing the resulting sequences to reference sequences generated from the blood of puma (Puma concolor), jaguar (Panthera onca), ocelot (Leopardus pardalus) and crab-eating fox (Cerdocyon thous). Scat size has previously been used to identify predators, but DNA data show that puma and jaguar scats overlap in size, as do those of puma, ocelot and fox. Prey-content analysis suggests minimal prey partitioning between pumas and jaguars. In field testing this technique for large carnivores, two potential limitations emerged: locating intact faecal samples and recovering DNA sequences from samples obtained in the wet season. Nonetheless, this study illustrates the tremendous potential of DNA faecal studies. The presence of domestic dog (Canis familiaris) in one puma scat and of wild pig (Sus scrofa), set as bait, in one jaguar sample exemplifies the forensic possibilities of this noninvasive analysis. In addition to defining the dietary habits of similar size sympatric mammals, DNA identifications from faeces allow wildlife managers to detect the presence of endangered taxa and manage prey for their conservation. PMID:11050553

  9. Ecological niche

    SciTech Connect

    Shugart, H.H.

    1980-01-01

    The ecological niche of an organism is the set of environmental conditions under which the particular functions of the organism could be expected to assure its survival. It comprises both the set of conditions where the organism lives (often termed the habitat of the organism) and the functional role of the organism in the ecosystem. Recent works in niche theory have enabled ecologists to develop predictions and actual applications. The history of the niche concept, applications of niche theory, and ecological differences between similar species are discussed.

  10. ECOLOGICAL DETERMINANTS OF POPULATION STRUCTURE AND GENE FLOW BETWEEN SYMPATRIC FUNGAL SPECIES IN THE GENUS COLLEOTRICHUM FROM DIVERSE GRASS COMMUNITIES

    EPA Science Inventory

    This comparative analysis will allow us to detect historical events of interest such as population fragmentations, range expansions, and colonization in the Colletotrichum species that inhabit pooid grasses. What is learned from C. cereale populations in agro...

  11. Elevational speciation in action? Restricted gene flow associated with adaptive divergence across an altitudinal gradient.

    PubMed

    Funk, W C; Murphy, M A; Hoke, K L; Muths, E; Amburgey, S M; Lemmon, E M; Lemmon, A R

    2016-02-01

    Evolutionary theory predicts that divergent selection pressures across elevational gradients could cause adaptive divergence and reproductive isolation in the process of ecological speciation. Although there is substantial evidence for adaptive divergence across elevation, there is less evidence that this restricts gene flow. Previous work in the boreal chorus frog (Pseudacris maculata) has demonstrated adaptive divergence in morphological, life history and physiological traits across an elevational gradient from approximately 1500-3000 m in the Colorado Front Range, USA. We tested whether this adaptive divergence is associated with restricted gene flow across elevation - as would be expected if incipient speciation were occurring - and, if so, whether behavioural isolation contributes to reproductive isolation. Our analysis of 12 microsatellite loci in 797 frogs from 53 populations revealed restricted gene flow across elevation, even after controlling for geographic distance and topography. Calls also varied significantly across elevation in dominant frequency, pulse number and pulse duration, which was partly, but not entirely, due to variation in body size and temperature across elevation. However, call variation did not result in strong behavioural isolation: in phonotaxis experiments, low-elevation females tended to prefer an average low-elevation call over a high-elevation call, and vice versa for high-elevation females, but this trend was not statistically significant. In summary, our results show that adaptive divergence across elevation restricts gene flow in P. maculata, but the mechanisms for this potential incipient speciation remain open. PMID:26363130

  12. Speciation, Diversification, and Coexistence of Sessile Species That Compete for Space

    PubMed Central

    Mitarai, Namiko; Heinsalu, Els; Sneppen, Kim

    2014-01-01

    Speciation, diversification, and competition between species challenge the stability of complex ecosystems. Laboratory experiments often focus on one or two species competing under conditions where they may grow exponentially. Field studies, in contrast, emphasize multi-species communities characterized by many types of ecological interactions. A general problem is to understand conditions that support a dynamically maintained coexistence of many species in an ecosystem over a long time span. In the present paper we propose a lattice model of multiple competing and evolving sessile species. When allowing the interspecies interactions to mutate, we obtain coexistence of many species in a complex ecosystem, provided that there is a cost for each interaction. The diversity reached by the model incorporating speciation is found to be substantially higher than in the case when entirely new species appear due to immigration from outside of the considered ecosystem. The species self-organize their spatial distribution through competitive interactions to create many patches, implicitly protecting each other from competitively superior species, and speciation in each patch leads the system to high diversity. We also show that species that exist a long time tend to have a relatively small population, as this allows them to avoid encounter with competitive invaders. PMID:24819515

  13. Speciation, diversification, and coexistence of sessile species that compete for space.

    PubMed

    Mitarai, Namiko; Heinsalu, Els; Sneppen, Kim

    2014-01-01

    Speciation, diversification, and competition between species challenge the stability of complex ecosystems. Laboratory experiments often focus on one or two species competing under conditions where they may grow exponentially. Field studies, in contrast, emphasize multi-species communities characterized by many types of ecological interactions. A general problem is to understand conditions that support a dynamically maintained coexistence of many species in an ecosystem over a long time span. In the present paper we propose a lattice model of multiple competing and evolving sessile species. When allowing the interspecies interactions to mutate, we obtain coexistence of many species in a complex ecosystem, provided that there is a cost for each interaction. The diversity reached by the model incorporating speciation is found to be substantially higher than in the case when entirely new species appear due to immigration from outside of the considered ecosystem. The species self-organize their spatial distribution through competitive interactions to create many patches, implicitly protecting each other from competitively superior species, and speciation in each patch leads the system to high diversity. We also show that species that exist a long time tend to have a relatively small population, as this allows them to avoid encounter with competitive invaders. PMID:24819515

  14. Elevational speciation in action? Restricted gene flow associated with adaptive divergence across an altitudinal gradient

    USGS Publications Warehouse

    Funk, W. C.; Murphy, M.A.; Hoke, K. L.; Muths, Erin L.; Amburgey, Staci M.; Lemmon, Emily M.; Lemmon, A. R.

    2016-01-01

    Evolutionary theory predicts that divergent selection pressures across elevational gradients could cause adaptive divergence and reproductive isolation in the process of ecological speciation. Although there is substantial evidence for adaptive divergence across elevation, there is less evidence that this restricts gene flow. Previous work in the boreal chorus frog (Pseudacris maculata) has demonstrated adaptive divergence in morphological, life history and physiological traits across an elevational gradient from approximately 1500–3000 m in the Colorado Front Range, USA. We tested whether this adaptive divergence is associated with restricted gene flow across elevation – as would be expected if incipient speciation were occurring – and, if so, whether behavioural isolation contributes to reproductive isolation. Our analysis of 12 microsatellite loci in 797 frogs from 53 populations revealed restricted gene flow across elevation, even after controlling for geographic distance and topography. Calls also varied significantly across elevation in dominant frequency, pulse number and pulse duration, which was partly, but not entirely, due to variation in body size and temperature across elevation. However, call variation did not result in strong behavioural isolation: in phonotaxis experiments, low-elevation females tended to prefer an average low-elevation call over a high-elevation call, and vice versa for high-elevation females, but this trend was not statistically significant. In summary, our results show that adaptive divergence across elevation restricts gene flow in P. maculata, but the mechanisms for this potential incipient speciation remain open.

  15. Defending Ecology.

    ERIC Educational Resources Information Center

    Margolis, Brian

    2000-01-01

    Explains how non-native species' problems in the ecosystem can introduce fundamental ecological principles in the classroom. Provides background information on damages caused by non-native species. Discusses how educators can use this environmental issue in the classroom and gives the example of zebra mussels. Lists instructional strategies for…

  16. Ecology, Microbial

    SciTech Connect

    Konopka, Allan

    2009-03-19

    Microbial ecology is a relatively young discipline within the field of microbiology. Its modern history spans just the past 60 years, and the field is defined by its emphasis on understanding the interactions of microbes with their environment, rather than their behavior under artificial laboratory conditions. Because microbes are ubiquitous, microbial ecologists study a broad diversity of habitats that range from aquatic to terrestrial to plant- or animal-associated. This has made it a challenge to identify unifying principles within the field. One approach is to recognize that although the activity of microbes in nature have effects at the macroscale, they interact with their physical, chemical and biological milieu at a scale of micrometers. At this scale, several different microbial ecosystems can be defined, based upon association with particles, the presence of environmental gradients and the continuous availability of water. Principles applicable to microbial ecology reflect not only their population ecology and physiological ecology, but also their broad versatility and quantitative importance in the biosphere as biogeochemical catalysts and capacity for rapid physiological and evolutionary responses.

  17. Trash Ecology

    ERIC Educational Resources Information Center

    Lind, Georgia J.

    2004-01-01

    A hands on activity involving density, frequency and biomass using transects, quadrats and a local good deed by cleaning up the neighborhood while practicing important techniques in ecology is detailed. The activity is designed for KCC-STEP, whose primary goal is to expand the scientific knowledge and research experiences of their students, who…

  18. Ecology, Microbial

    SciTech Connect

    Konopka, Allan

    2009-05-15

    Microbial ecology is a relatively young discipline within the field of microbiology. Its modern history spans just the past 60 years, and the field is defined by its emphasis on understanding the interactions of microbes with their environment, rather than their behavior under artificial laboratory conditions. Because microbes are ubiquitous, microbial ecologists study a broad diversity of habitats that range from aquatic to terrestrial to plant- or animal-associated. This has made it a challenge to identify unifying principles within the field. One approach is to recognize that although the activity of microbes in nature have effects at the macroscale, they interact with their physical, chemical and biological milieu at a scale of micrometers. At this scale, several different microbial ecosystems can be defined, based upon association with particles, the presence of environmental gradients and the continuous availability of water. Principles applicable to microbial ecology reflect not only their population ecology and physiological ecology, but also their broad versatility and quantitative importance in the biosphere as biogeochemical catalysts and capacity for rapid physiological and evolutionary responses.

  19. Behavioral evidence for fruit odor discrimination and sympatric host races of Rhagoletis pomonella flies in the western United States

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The recent shift of Rhagoletis pomonella (Diptera: Tephritidae) from its native host downy hawthorn, Crataegus mollis, to introduced domesticated apple, Malus domestica, in the eastern U.S. is a model for sympatric host race formation. However, the fly is also present in the western U.S. where it ma...

  20. Uncovering tropical diversity: six sympatric cryptic species of Blepharoneura (Diptera: Tephritidae) in flowers of Gurania spinulosa (Cucurbitaceae) in eastern Ecuador

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Diversification of phytophagous insects is often associated with changes in the use of host taxa and host parts. We focus on a group of newly discovered neotropical tephritids in the genus Blepharoneura, and report the discovery of an extraordinary number of sympatric, morphologically cryptic specie...

  1. Hybridization and Introgression in a Sympatric Pair of Oak Species (Fagaceae) Studied with Morphology and Chloroplast and Nuclear SSR Markers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Chloroplast and nuclear SSR markers and morphology were used to study hybridization and introgression between Quercus douglasii and Q. lobata, two sympatric oak species native to California. Chloroplast SSR markers provided strong evidence of gene exchange via ongoing introgression between these sp...

  2. Pervasive recombination and sympatric genome diversification driven by frequency-dependent selection in Borrelia burgdorferi, the Lyme disease bacterium.

    PubMed

    Haven, James; Vargas, Levy C; Mongodin, Emmanuel F; Xue, Vincent; Hernandez, Yozen; Pagan, Pedro; Fraser-Liggett, Claire M; Schutzer, Steven E; Luft, Benjamin J; Casjens, Sherwood R; Qiu, Wei-Gang

    2011-11-01

    How genomic diversity within bacterial populations originates and is maintained in the presence of frequent recombination is a central problem in understanding bacterial evolution. Natural populations of Borrelia burgdorferi, the bacterial agent of Lyme disease, consist of diverse genomic groups co-infecting single individual vertebrate hosts and tick vectors. To understand mechanisms of sympatric genome differentiation in B. burgdorferi, we sequenced and compared 23 genomes representing major genomic groups in North America and Europe. Linkage analysis of >13,500 single-nucleotide polymorphisms revealed pervasive horizontal DNA exchanges. Although three times more frequent than point mutation, recombination is localized and weakly affects genome-wide linkage disequilibrium. We show by computer simulations that, while enhancing population fitness, recombination constrains neutral and adaptive divergence among sympatric genomes through periodic selective sweeps. In contrast, simulations of frequency-dependent selection with recombination produced the observed pattern of a large number of sympatric genomic groups associated with major sequence variations at the selected locus. We conclude that negative frequency-dependent selection targeting a small number of surface-antigen loci (ospC in particular) sufficiently explains the maintenance of sympatric genome diversity in B. burgdorferi without adaptive divergence. We suggest that pervasive recombination makes it less likely for local B. burgdorferi genomic groups to achieve host specialization. B. burgdorferi genomic groups in the northeastern United States are thus best viewed as constituting a single bacterial species, whose generalist nature is a key to its rapid spread and human virulence. PMID:21890743

  3. Highly variable patterns of antimicrobial resistance in commensal Escherichia coli isolates from pigs, sympatric rodents, and flies.

    PubMed

    Literak, Ivan; Dolejska, Monika; Rybarikova, Jana; Cizek, Alois; Strejckova, Pavla; Vyskocilova, Martina; Friedman, Miroslava; Klimes, Jiri

    2009-09-01

    Antimicrobial-resistant Escherichia coli strains from pigs, sympatric rodents, and flies from two large farms in the Czech Republic with different antibiotic exposure histories were characterized based on antimicrobial resistance genes, integrons, and macrorestriction DNA profiles. Isolates of E. coli were tested for susceptibility to 12 antimicrobial agents according to the standard disk diffusion method. In resistant isolates, polymerase chain reaction was used to detect antibiotic resistance genes, integrase genes, and gene cassettes. Pulsed-field gel electrophoresis (PFGE) was used for molecular subtyping of E. coli. In farm A (long-term use of amoxicillin only), 75% (n = 198), 65% (n = 49), 11% (n = 139), and 82% (n = 177) of E. coli isolates from piglets, sows, sympatric rodents, and flies, respectively, were antibiotic resistant. In farm B (various antibiotics commonly used), 53% (n = 154), 69% (n = 98), and 54% (n = 74) of E. coli isolates from piglets, sows, and sympatric rodents, respectively, were antibiotic resistant. In both farms, the highest resistance prevalence was to tetracycline, and resistance patterns of isolates were greatly variable. Isolates with the same resistance phenotype, genes, and PFGE profile were found in pigs and flies. Isolates from rodents showed unique PFGE profiles. Close contact of sympatric rodents and flies with pigs or their products was associated with colonization of rodents and flies with resistant bacteria or transfer of resistance genes found in pig intestinal flora. PMID:19728783

  4. Using Next-Generation Sequencing to Contrast the Diet and Explore Pest-Reduction Services of Sympatric Bird Species in Macadamia Orchards in Australia

    PubMed Central

    Crisol-Martínez, Eduardo; Moreno-Moyano, Laura T.; Wormington, Kevin R.; Brown, Philip H.; Stanley, Dragana

    2016-01-01

    Worldwide, avian communities inhabiting agro-ecosystems are threatened as a consequence of agricultural intensification. Unravelling their ecological role is essential to focus conservation efforts. Dietary analysis can elucidate bird-insect interactions and expose avian pest-reduction services, thus supporting avian conservation. In this study, we used next-generation sequencing to analyse the dietary arthropod contents of 11 sympatric bird species foraging in macadamia orchards in eastern Australia. Across all species and based on arthropod DNA sequence similarities ≥98% with records in the Barcode of Life Database, 257 operational taxonomy units were assigned to 8 orders, 40 families, 90 genera and 89 species. These taxa included 15 insect pests, 5 of which were macadamia pests. Among the latter group, Nezara viridula (Pentatomidae; green vegetable bug), considered a major pest, was present in 23% of all faecal samples collected. Results also showed that resource partitioning in this system is low, as most bird species shared large proportion of their diets by feeding primarily on lepidopteran, dipteran and arachnids. Dietary composition differed between some species, most likely because of differences in foraging behaviour. Overall, this study reached a level of taxonomic resolution never achieved before in the studied species, thus contributing to a significant improvement in the avian ecological knowledge. Our results showed that bird communities prey upon economically important pests in macadamia orchards. This study set a precedent by exploring avian pest-reduction services using next-generation sequencing, which could contribute to the conservation of avian communities and their natural habitats in agricultural systems. PMID:26930484

  5. Using Next-Generation Sequencing to Contrast the Diet and Explore Pest-Reduction Services of Sympatric Bird Species in Macadamia Orchards in Australia.

    PubMed

    Crisol-Martínez, Eduardo; Moreno-Moyano, Laura T; Wormington, Kevin R; Brown, Philip H; Stanley, Dragana

    2016-01-01

    Worldwide, avian communities inhabiting agro-ecosystems are threatened as a consequence of agricultural intensification. Unravelling their ecological role is essential to focus conservation efforts. Dietary analysis can elucidate bird-insect interactions and expose avian pest-reduction services, thus supporting avian conservation. In this study, we used next-generation sequencing to analyse the dietary arthropod contents of 11 sympatric bird species foraging in macadamia orchards in eastern Australia. Across all species and based on arthropod DNA sequence similarities ≥98% with records in the Barcode of Life Database, 257 operational taxonomy units were assigned to 8 orders, 40 families, 90 genera and 89 species. These taxa included 15 insect pests, 5 of which were macadamia pests. Among the latter group, Nezara viridula (Pentatomidae; green vegetable bug), considered a major pest, was present in 23% of all faecal samples collected. Results also showed that resource partitioning in this system is low, as most bird species shared large proportion of their diets by feeding primarily on lepidopteran, dipteran and arachnids. Dietary composition differed between some species, most likely because of differences in foraging behaviour. Overall, this study reached a level of taxonomic resolution never achieved before in the studied species, thus contributing to a significant improvement in the avian ecological knowledge. Our results showed that bird communities prey upon economically important pests in macadamia orchards. This study set a precedent by exploring avian pest-reduction services using next-generation sequencing, which could contribute to the conservation of avian communities and their natural habitats in agricultural systems. PMID:26930484

  6. Morphological features of larvae of Drusus plicatus Radovanović (Insecta, Trichoptera) from the Republic of Macedonia with molecular, ecological, ethological, and distributional notes

    PubMed Central

    Kučinić, Mladen; Previšić, Ana; Mihoci, Iva; Krpač, Vladimir; Živić, Ivana; Stojanović, Katarina; Vojvoda, Ana Mrnjavčić; Katušić, Luka

    2016-01-01

    Abstract A description of the larva of Drusus plicatus Radovanović is given for the first time. The most important diagnostic characters enabling separation from larvae of the other Drusinae from the southeast Europe are listed. Molecular, ecological, and ethological features and distribution patterns of the species are given. Additionally, information on the sympatric caddisfly species of the three springs where larvae and adults of Drusus plicatus were found and presented. PMID:27408591

  7. Incipient speciation with gene flow on a continental island: Species delimitation of the Hainan Hwamei (Leucodioptron canorum owstoni, Passeriformes, Aves).

    PubMed

    Wang, Ning; Liang, Bin; Wang, Jichao; Yeh, Chia-Fen; Liu, Yang; Liu, Yanlin; Liang, Wei; Yao, Cheng-Te; Li, Shou-Hsien

    2016-09-01

    Because of their isolation, continental islands (e.g., Madagascar) are often thought of as ideal systems to study allopatric speciation. However, many such islands have been connected intermittently to their neighboring continent during recent periods of glaciation, which may cause frequent contact between the diverging populations on the island and continent. As a result, the speciation processes on continental islands may not meet the prerequisites for strictly allopatric speciation. We used multiple lines of evidence to re-evaluate the taxonomic status of the Hainan Hwamei (Leucodioptron canorum owstoni), which is endemic to Hainan, the largest continental island in the South China Sea. Our analysis of mitochondrial DNA and twelve nuclear loci suggests that the Hainan Hwamei can be regarded as an independent species (L. owstoni); the morphological traits of the Hainan Hwamei also showed significant divergence from those of their mainland sister taxon, the Chinese Hwamei (L. canorum). We also inferred the divergence history of the Hainan and Chinese Hwamei to see whether their divergence was consistent with a strictly allopatric model. Our results suggest that the two Hwameis split only 0.2 million years ago with limited asymmetrical post-divergence gene flow. This implies that the Hainan Hwamei is an incipient species and that speciation occurred through ecologically divergent selection and/or assortative mating rather than a strictly allopatric process. PMID:27233437

  8. Speciation in aqueous solutions of nitric acid.

    PubMed

    Hlushak, S; Simonin, J P; De Sio, S; Bernard, O; Ruas, A; Pochon, P; Jan, S; Moisy, P

    2013-02-28

    In this study, speciation in aqueous solutions of nitric acid at 25 °C was assessed in two independent ways. First, Raman experiments were carried out and interpreted in terms of free nitrate ions, ion pairs and neutral HNO(3) molecules. In parallel, a model was developed to account for the formation of these two kinds of pairs. It was based on an extension of the binding mean spherical approximation (BiMSA), or associative MSA (AMSA), in which the size and the charge of the ions in the chemical pair may differ from those of the free ions. A simultaneous fit of the osmotic coefficient and of the proportion of free ions (obtained from Raman spectroscopy experiments) led to an estimation of the speciation in nitric acid solutions. The result obtained using this procedure was compared with the estimation obtained from the Raman experiments. PMID:23258765

  9. Travel, sex, and food: what's speciation got to do with it?

    PubMed

    Souza, Valeria; Eguiarte, Luis E; Travisano, Michael; Elser, James J; Rooks, Christine; Siefert, Janet L

    2012-07-01

    We discuss the potential interactions among travel (dispersal and gene flow), bacterial "sex" (mainly as horizontal gene transfer), and food (metabolic plasticity and responses to nutrient availability) in shaping microbial communities. With regard to our work at a unique desert oasis, the Cuatro Ciénegas Basin in Coahuila, Mexico, we propose that diversification and low phosphorus availability, in combination with mechanisms for nutrient recycling and community cohesion, result in enhanced speciation through reproductive as well as geographic isolation. We also discuss these mechanisms in the broader sense of ecology and evolution. Of special relevance to astrobiology and central to evolutionary biology, we ask why there are so many species on Earth and provide a working hypothesis and a conceptual framework within which to consider the question. Key Words: Microbial ecology-Microbial mats-Evolution-Horizontal gene transfer-Metabolism. PMID:22920513

  10. Boron uptake, localization, and speciation in marine brown algae.

    PubMed

    Miller, Eric P; Wu, Youxian; Carrano, Carl J

    2016-02-01

    In contrast to the generally boron-poor terrestrial environment, the concentration of boron in the marine environment is relatively high (0.4 mM) and while there has been extensive interest in its use as a surrogate of pH in paleoclimate studies in the context of climate change-related questions, the relatively depth independent, and the generally non-nutrient-like concentration profile of this element have led to boron being neglected as a potentially biologically relevant element in the ocean. Among the marine plant-like organisms the brown algae (Phaeophyta) are one of only five lineages of photosynthetic eukaryotes to have evolved complex multicellularity. Many of unusual and often unique features of brown algae are attributable to this singular evolutionary history. These adaptations are a reflection of the marine coastal environment which brown algae dominate in terms of biomass. Consequently, brown algae are of fundamental importance to oceanic ecology, geochemistry, and coastal industry. Our results indicate that boron is taken up by a facilitated diffusion mechanism against a considerable concentration gradient. Furthermore, in both Ectocarpus and Macrocystis some boron is most likely bound to cell wall constituent alginate and the photoassimilate mannitol located in sieve cells. Herein, we describe boron uptake, speciation, localization and possible biological function in two species of brown algae, Macrocystis pyrifera and Ectocarpus siliculosus. PMID:26679972

  11. Floral symmetry affects speciation rates in angiosperms.

    PubMed Central

    Sargent, Risa D.

    2004-01-01

    Despite much recent activity in the field of pollination biology, the extent to which animal pollinators drive the formation of new angiosperm species remains unresolved. One problem has been identifying floral adaptations that promote reproductive isolation. The evolution of a bilaterally symmetrical corolla restricts the direction of approach and movement of pollinators on and between flowers. Restricting pollinators to approaching a flower from a single direction facilitates specific placement of pollen on the pollinator. When coupled with pollinator constancy, precise pollen placement can increase the probability that pollen grains reach a compatible stigma. This has the potential to generate reproductive isolation between species, because mutations that cause changes in the placement of pollen on the pollinator may decrease gene flow between incipient species. I predict that animal-pollinated lineages that possess bilaterally symmetrical flowers should have higher speciation rates than lineages possessing radially symmetrical flowers. Using sister-group comparisons I demonstrate that bilaterally symmetric lineages tend to be more species rich than their radially symmetrical sister lineages. This study supports an important role for pollinator-mediated speciation and demonstrates that floral morphology plays a key role in angiosperm speciation. PMID:15156918

  12. Chiral Speciation in Terrestrial Pulmonate Snails

    PubMed Central

    Gittenberger, Edmund; Hamann, Thomas D.; Asami, Takahiro

    2012-01-01

    On the basis of data in the literature, the percentages of dextral versus sinistral species of snails have been calculated for western Europe, Turkey, North America (north of Mexico), and Japan. When the family of Clausiliidae is represented, about a quarter of all snail species may be sinistral, whereas less than one per cent of the species may be sinistral where that family does not occur. The number of single-gene speciation events on the basis of chirality, resulting in the origin of mirror image species, is not closely linked to the percentage of sinistral versus dextral species in a particular region. Turkey is nevertheless exceptional by both a high percentage of sinistral species and a high number of speciation events resulting in mirror image species. Shell morphology and genetic background may influence the ease of chirality-linked speciation, whereas sinistrality may additionally be selected against by internal selection. For the Clausiliidae, the fossil record and the recent fauna suggest that successful reversals in coiling direction occurred with a frequency of once every three to four million years. PMID:22532825

  13. Gastropod diversification and community structuring processes in ancient Lake Ohrid: a metacommunity speciation perspective

    NASA Astrophysics Data System (ADS)

    Hauffe, T.; Albrecht, C.; Wilke, T.

    2015-09-01

    The Balkan Lake Ohrid is the oldest and most speciose freshwater lacustrine system in Europe. However, it remains unclear whether the diversification of its endemic taxa is mainly driven by neutral processes, environmental factors, or species interactions. This calls for a holistic perspective involving both evolutionary processes and ecological dynamics. Such a unifying framework - the metacommunity speciation model - considers how community assembly affects diversification and vice versa by assessing the relative contribution of the three main community assembly processes, dispersal limitation, environmental filtering, and species interaction. The current study therefore used the species-rich model taxon Gastropoda to assess how extant communities in Lake Ohrid are structured by performing process based metacommunity analyses. Specifically, the study aimed at (i) identifying the relative importance of the three community assembly processes and (ii) to test whether the importance of these individual processes changes gradually with lake depth or whether they are distinctively related to eco-zones. Based on specific simulation steps for each of the three processes, it could be demonstrated that dispersal limitation had the strongest influence on gastropod community structures in Lake Ohrid. However, it was not the exclusive assembly process but acted together with the other two processes - environmental filtering, and species interaction. In fact, the relative importance of the three community assembly processes varied both with lake depth and eco-zones, though the processes were better predicted by the latter. The study thus corroborated the high importance of dispersal limitation for both maintaining species richness in Lake Ohrid (through its impact on community structure) and generating endemic biodiversity (via its influence on diversification processes). However, according to the metacommunity speciation model, the inferred importance of environmental

  14. A novel preference for an invasive plant as a mechanism for animal hybrid speciation.

    PubMed

    Schwarz, Dietmar; Shoemaker, Katrina D; Botteri, Nicole L; McPheron, Bruce A

    2007-02-01

    Homoploid hybrid speciation--speciation via hybridization without a change in chromosome number--is rarely documented and poorly understood in animals. In particular, the mechanisms by which animal homoploid hybrid species become ecologically and reproductively isolated from their parents are hypothetical and remain largely untested by experiments. For the many host-specific parasites that mate on their host, choosing the right host is the most important ecological and reproductive barrier between these species. One example of a host-specific parasite is the Lonicera fly, a population of tephritid fruit flies that evolved within the last 250 years likely by hybridization between two native Rhagoletis species following a host shift to invasive honeysuckle. We studied the host preference of the Lonicera fly and its putative parent species in laboratory experiments. The Lonicera fly prefers its new host, introduced honeysuckle, over the hosts of both parental species, demonstrating the rapid acquisition of preference for a new host as a means of behavioral isolation from the parent species. The parent taxa discriminate against each other's native hosts, but both accept honeysuckle fruit, leaving the potential for asymmetric gene flow from the parent species. Importantly, this pattern allows us to formulate hypotheses about the initial formation of the Lonicera fly. As mating partners from the two parent taxa are more likely to meet on invasive honeysuckle than on their respective native hosts, independent acceptance of honeysuckle by both parents likely preceded hybridization. We propose that invasive honeysuckle served as a catalyst for the local breakdown of reproductive isolation between the native parent species, a novel consequence of the introduction of an exotic weed. We describe behavioral mechanisms that explain the initial hybridization and subsequent reproductive isolation of the hybrid Lonicera fly. These results provide experimental support for a

  15. Beringian origins and cryptic speciation events in the fly agaric (Amanita muscaria).

    PubMed

    Geml, J; Laursen, G A; O'neill, K; Nusbaum, H C; Taylor, D L

    2006-01-01

    Amanita muscaria sensu lato has a wide geographic distribution, occurring in Europe, Asia, Africa, Australia, New Zealand, and North, Central and South America. Previous phylogenetic work by others indicates three geographic clades (i.e. 'Eurasian', 'Eurasian-alpine' and 'North American' groups) within A. muscaria. However, the historical dispersal patterns of A. muscaria remained unclear. In our project, we collected specimens from arctic, boreal and humid temperate regions in Alaska, and generated DNA sequence data from the protein-coding beta-tubulin gene and the internal transcribed spacer (ITS) and large subunit (LSU) regions of the ribosomal DNA repeat. Homologous sequences from additional A. muscaria isolates were downloaded from GenBank. We conducted phylogenetic and nested clade analyses (NCA) to reveal the phylogeographic history of the species complex. Although phylogenetic analyses confirmed the existence of the three above-mentioned clades, representatives of all three groups were found to occur sympatrically in Alaska, suggesting that they represent cryptic phylogenetic species with partially overlapping geographic distributions rather than being allopatric populations. All phylogenetic species share at least two morphological varieties with other species, suggesting ancestral polymorphism in pileus and wart colour pre-dating their speciations. The ancestral population of A. muscaria likely evolved in the Siberian-Beringian region and underwent fragmentation as inferred from NCA and the coalescent analyses. The data suggest that these populations later evolved into species, expanded their range in North America and Eurasia. In addition to range expansions, populations of all three species remained in Beringia and adapted to the cooling climate. PMID:16367842

  16. A linkage disequilibrium perspective on the genetic mosaic of speciation in two hybridizing Mediterranean white oaks

    PubMed Central

    Goicoechea, P G; Herrán, A; Durand, J; Bodénès, C; Plomion, C; Kremer, A

    2015-01-01

    We analyzed the genetic mosaic of speciation in two hybridizing Mediterranean white oaks from the Iberian Peninsula (Quercus faginea Lamb. and Quercus pyrenaica Willd.). The two species show ecological divergence in flowering phenology, leaf morphology and composition, and in their basic or acidic soil preferences. Ninety expressed sequence tag-simple sequence repeats (EST-SSRs) and eight nuclear SSRs were genotyped in 96 trees from each species. Genotyping was designed in two steps. First, we used 69 markers evenly distributed over the 12 linkage groups (LGs) of the oak linkage map to confirm the species genetic identity of the sampled genotypes, and searched for differentiation outliers. Then, we genotyped 29 additional markers from the chromosome bins containing the outliers and repeated the multilocus scans. We found one or two additional outliers within four saturated bins, thus confirming that outliers are organized into clusters. Linkage disequilibrium (LD) was extensive; even for loosely linked and for independent markers. Consequently, score tests for association between two-marker haplotypes and the ‘species trait' showed a broad genomic divergence, although substantial variation across the genome and within LGs was also observed. We discuss the influence of several confounding effects on neutrality tests and review the evolutionary processes leading to extensive LD. Finally, we examine how LD analyses within regions that contain outlier clusters and quantitative trait loci can help to identify regions of divergence and/or genomic hitchhiking in the light of predictions from ecological speciation theory. PMID:25515016

  17. Survival and band recovery rates of sympatric American black ducks and mallards

    USGS Publications Warehouse

    Nichols, J.D.; Obrecht, H.H., III; Hines, J.E.

    1987-01-01

    Banding and recovery data from American black ducks (Anas rubripes) and mallards (A. platyrhynchos) banded in the same breeding or wintering areas over the same time periods were used to estimate annual survival and band recovery rates. Recovery rates, based on preseason bandings, were very similar for sympatric black ducks and mallards and exhibited similar patterns of year-to-year variation for the 2 species. Tests for differences between the species in annual survival rates yielded equivocal results. We tentatively conclude that annual survival rates of mallards generally were not higher than those of black ducks banded in the same areas. The apparent difference in population status between black ducks and eastern mallards does not seem to result from differences in mortality rate. Nevertheless, we should attempt to identify management practices that might increase survival probabilities of black ducks.

  18. The Aquatic Communities Inhabiting Internodes of Two Sympatric Bamboos in Argentinean Subtropical Forest

    PubMed Central

    Campos, Raúl E.

    2013-01-01

    In order to determine if phytotelmata in sympatric bamboos of the genus Guadua might be colonized by different types of arthropods and contain communities of different complexities, the following objectives were formulated: (1) to analyze the structure and species richness of the aquatic macroinvertebrate communities, (2) to comparatively analyze co-occurrences; and (3) to identify the main predators. Field studies were conducted in a subtropical forest in Argentina, where 80 water-filled bamboo internodes of Guadua chacoensis (Rojas Acosta) Londoño and Peterson (Poales: Poaceae) and G. trinii (Nees) Nees and Rupr. were sampled. Morphological measurements indicated that G. chacoensis held more fluid than G. trinii. The communities differed between Guadua species, but many macroinvertebrate species used both bamboo species. The phytotelmata were mainly colonized by Diptera of the families Culicidae and Ceratopogonidae. PMID:24224775

  19. Red colobus as prey: the leaping habits of five sympatric Old World monkeys.

    PubMed

    Stern, Michael; Goldstone, Rebecca

    2005-01-01

    This study explored the leaping habits of five sympatric Old World monkeys (Colobus badius, Colobus guereza, Cercopithecus ascanius, Cercopithecus mitis and Cercocebus albigena) in an attempt to determine why chimpanzees prefer to hunt red colobus. We videotaped the leaps of the monkeys for 3 months in Uganda's Kibale National Park. Data were collected on leap preparation time as well as several other variables of the leaps. The leap preparation time of red colobus was found to be about double that of the other species studied. This difference is a likely reason why red colobus represent the preferred prey of chimpanzees. The hypothesis that red colobus spend more time in isolated trees than do other species was not supported. PMID:15775681

  20. Survival and band recovery rates of sympatric grey ducks and mallards in New Zealand

    USGS Publications Warehouse

    Caithness, T.; Williams, M.; Nichols, J.D.

    1991-01-01

    We used band recovery data from grey ducks (Anas superciliosa) and mallards. (A. platyrhynchos) banded sympatrically during 1957-74 to estimate annual survival and recovery rates. Young birds tended to have higher recovery rates and lower survival rates than adults for both species. Both species showed strong evidence of year-to-year variation in annual survival rates. Survival rates of male mallards were higher than those in females, as is typical for this species in North America, but there was no evidence of sex-specific survival differences in grey ducks. Recovery rate estimates for grey ducks were high and were significantly higher than those for mallards. However, survival rates did not differ significantly between the 2 species within any age-sex class. The similar survival rates, when mallard populations were increasing and grey ducks were decreasing, suggest that mallard reproductive rates have been greater than those of grey ducks.

  1. The aquatic communities inhabiting internodes of two sympatric bamboos in Argentinean subtropical forest.

    PubMed

    Campos, Raúl E

    2013-01-01

    In order to determine if phytotelmata in sympatric bamboos of the genus Guadua might be colonized by different types of arthropods and contain communities of different complexities, the following objectives were formulated: (1) to analyze the structure and species richness of the aquatic macroinvertebrate communities, (2) to comparatively analyze co-occurrences; and (3) to identify the main predators. Field studies were conducted in a subtropical forest in Argentina, where 80 water-filled bamboo internodes of Guadua chacoensis (Rojas Acosta) Londoño and Peterson (Poales: Poaceae) and G. trinii (Nees) Nees and Rupr. were sampled. Morphological measurements indicated that G. chacoensis held more fluid than G. trinii. The communities differed between Guadua species, but many macroinvertebrate species used both bamboo species. The phytotelmata were mainly colonized by Diptera of the families Culicidae and Ceratopogonidae. PMID:24224775

  2. Did pollination shifts drive diversification in southern African Gladiolus? Evaluating the model of pollinator-driven speciation.

    PubMed

    Valente, Luis M; Manning, John C; Goldblatt, Peter; Vargas, Pablo

    2012-07-01

    The pollinator-driven ecological speciation model has frequently been invoked to explain plant richness in biodiversity hotspots. Here, by focusing on Gladiolus (260 species), a flagship example of a clade with diverse pollination biology, we test the hypothesis that high species diversity in southern Africa, one of the world's most floristically rich regions, has primarily been driven by ecological shifts in pollination systems. We use phylogenetic methods to estimate rates of transition between the seven highly specialized pollination strategies in Gladiolus. We find that pollination systems have evolved multiple times and that some pollination strategies arose by a variety of evolutionary pathways. Pollination shifts account for up to one-third of all lineage splitting events in the genus, providing partial support for the pollinator-driven speciation model. Transitions from the ancestral pollination mode to derived systems have also resulted in increased rates of diversification, suggesting that certain pollination systems may speed up speciation processes, independently of pollination shifts per se. This study suggests that frequent pollination shifts have played a role in driving high phenotypic and species diversity but indicates that additional factors need to be invoked to account for the spectacular diversification in southern African Gladiolus. PMID:22673653

  3. Sex-pairing pheromones and reproductive isolation in three sympatric Cornitermes species (Isoptera, Termitidae, Syntermitinae).

    PubMed

    Bordereau, Christian; Cancello, Eliana M; Sillam-Dussès, David; Sémon, Etienne

    2011-04-01

    The species-specificity of pairing has been studied in three sympatric Neotropical termites: Cornitermes bequaerti, Cornitermes cumulans and Cornitermes silvestrii (Termitidae, Syntermitinae). Bioassays showed that sex attraction was highly species-specific between C. bequaerti and C. cumulans but not between C. cumulans and C. silvestrii. The sex-pairing pheromone of the three species is secreted by the tergal glands of female alates. It consists of a common compound (3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol. In C. bequaerti, this polyunsaturated alcohol is the only compound of the sex-pairing pheromone, whereas it is associated with the oxygenated sesquiterpene (E)-nerolidol in C. cumulans, and with (E)-nerolidol and (Z)-dodec-3-en-1-ol in C. silvestrii. (3Z,6Z,8E)-Dodeca-3,6,8-trien-1-ol is responsible for sexual attraction, whereas (E)-nerolidol, which is inactive in eliciting attraction of male alates, is responsible for the species-specificity of the attraction. This is the first time that a multicomponent sex-pairing pheromone has been identified in termites. The role of (Z)-dodec-3-en-1-ol present on the surface of the tergal glands of the female alates of C. silvestrii could not be definitively determined, but it is suggested that this compound could be involved in the species-specificity of sex attraction with other sympatric species of Cornitermes. Our study shows that the reproductive isolation in termites is due to a succession of factors, as the chronology of dispersal flights, the species-specificity of sex-pairing pheromones and the species-specific recognition. PMID:21277310

  4. Home Bodies and Wanderers: Sympatric Lineages of the Deep-Sea Black Coral Leiopathes glaberrima

    PubMed Central

    Ruiz-Ramos, Dannise V.; Saunders, Miles; Fisher, Charles R.; Baums, Iliana B.

    2015-01-01

    Colonial corals occur in a wide range of marine benthic habitats from the shallows to the deep ocean, often defining the structure of their local community. The black coral Leiopathes glaberrima is a long-lived foundation species occurring on carbonate outcrops in the Northern Gulf of Mexico (GoM). Multiple color morphs of L. glaberrima grow sympatrically in the region. Morphological, mitochondrial and nuclear ribosomal markers supported the hypothesis that color morphs constituted a single biological species and that colonies, regardless of color, were somewhat genetically differentiated east and west of the Mississippi Canyon. Ten microsatellite loci were used to determine finer-scale population genetic structure and reproductive characteristics. Gene flow was disrupted between and within two nearby (distance = 36.4 km) hardground sites and two sympatric microsatellite lineages, which might constitute cryptic species, were recovered. Lineage one was outbred and found in all sampled locations (N = 5) across 765.6 km in the Northern Gulf of Mexico. Lineage two was inbred, reproducing predominantly by fragmentation, and restricted to sites around Viosca Knoll. In these sites the lineages and the color phenotypes occurred in different microhabitats, and models of maximum entropy suggested that depth and slope influence the distribution of the color phenotypes within the Vioska Knolls. We conclude that L. glaberrima is phenotypically plastic with a mixed reproductive strategy in the Northern GoM. Such strategy might enable this long-lived species to balance local recruitment with occasional long-distance dispersal to colonize new sites in an environment where habitat is limited. PMID:26488161

  5. Relationship between Spatial Working Memory Performance and Diet Specialization in Two Sympatric Nectar Bats

    PubMed Central

    Henry, Mickaël; Stoner, Kathryn E.

    2011-01-01

    Behavioural ecologists increasingly recognise spatial memory as one the most influential cognitive traits involved in evolutionary processes. In particular, spatial working memory (SWM), i.e. the ability of animals to store temporarily useful information for current foraging tasks, determines the foraging efficiency of individuals. As a consequence, SWM also has the potential to influence competitive abilities and to affect patterns of sympatric occurrence among closely related species. The present study aims at comparing the efficiency of SWM between generalist (Glossophaga soricina) and specialist (Leptonycteris yerbabuenae) nectarivorous bats at flowering patches. The two species differ in diet – the generalist diet including seasonally fruits and insects with nectar and pollen while the specialist diet is dominated by nectar and pollen yearlong – and in some morphological traits – the specialist being heavier and with proportionally longer rostrum than the generalist. These bats are found sympatrically within part of their range in the Neotropics. We habituated captive individuals to feed on artificial flower patches and we used infrared video recordings to monitor their ability to remember and avoid the spatial location of flowers they emptied in previous visits in the course of 15-min foraging sequences. Experiments revealed that both species rely on SWM as their foraging success attained significantly greater values than random expectations. However, the nectar specialist L. yerbabuenae was significantly more efficient at extracting nectar (+28% in foraging success), and sustained longer foraging bouts (+27% in length of efficient foraging sequences) than the generalist G. soricina. These contrasting SWM performances are discussed in relation to diet specialization and other life history traits. PMID:21931612

  6. Sympatric species distribution, genetic diversity and population structure of Haemonchus isolates from domestic ruminants in Pakistan.

    PubMed

    Hussain, Tanveer; Periasamy, Kathiravan; Nadeem, Asif; Babar, Masroor Ellahi; Pichler, Rudolf; Diallo, Adama

    2014-12-15

    Haemonchus species are major gastro-intestinal parasites affecting ruminants across the world. The present study aimed to assess the sympatric species distribution, genetic diversity, population structure and frequency of β-tubulin isotype 1 alleles associated with benzimidazole resistance. Internal transcribed spacer 2 (ITS2) sequences revealed three sympatric species of Haemonchus, H. contortus, H. placei and H. longistipes with 12 distinct genotypes circulating among ruminant hosts in Pakistan. High genetic variability was observed in Pakistani Haemonchus isolates at nicotine amide dehydrogenase subunit 4 (ND4) and cytochrome oxidase subunit 1 (COI) gene loci. Intra-population diversity parameters were higher in H. contortus isolates than H. placei. Phylogenetic analysis of ND4 and COI sequences did not reveal clustering of haplotypes originating from a particular host indicating high rate of gene flow among Haemonchus parasites infecting sheep, goat and cattle in Pakistan. ND4 and COI haplotypes from Pakistan were compared to sequences of Haemonchus isolates from 11 countries to elucidate the population structure. Multidimensional scaling (MDS) plot of pairwise FST derived from 531 ND4 haplotypes revealed clustering together of H. contortus from Pakistan, China, Malaysia and Italy while the isolates from Yemen and United States were found to be genetically distinct. With respect to H. placei, isolates from Pakistan were found to be genetically differentiated from isolates of other countries. The tests for selective neutrality revealed negative D statistics and did not reveal significant deviations in Pakistani Haemonchus populations while significant deviation (P < 0.05) was observed in Brazilian and Chinese H. contortus populations. Median Joining (MJ) network of ND4 haplotypes revealed Yemenese H. contortus being closer to H. placei cluster. β-tubulin isotype 1 genotyping revealed 7.86% frequency of Y allele associated with benzimidazole resistance at F200Y

  7. Causes and consequences of contrasting genetic structure in sympatrically growing and closely related species

    PubMed Central

    Radosavljević, Ivan; Satovic, Zlatko; Liber, Zlatko

    2015-01-01

    Gene flow, natural selection and genetic drift are processes that play a major role in shaping the genetic structure of natural populations. In addition, genetic structures of individual populations are strongly correlated with their geographical position within the species distribution area. The highest levels of genetic variation are usually found in the centre of a species' distribution and tend to decrease beyond that point. Additionally, narrowly endemic taxa are expected to be characterized by lower levels of genetic variation than their widespread congeners. To understand the historical circumstances that shape populations of sympatric and closely related taxa, microsatellite markers were used, while populations of the three closely related and sympatric Mediterranean Salvia species (S. officinalis L., S. fruticosa Mill. and S. brachyodon Vandas) served as a study model. In the populations of widespread S. officinalis, located in the central parts of this species' distribution area, no population genetic disturbances were detected. The narrow endemic S. brachyodon showed heterozygote excess, clonal reproduction and a genetic bottleneck. Because the genetic bottleneck was likely caused by the disappearance of suitable open-type habitats, the recent wildfire that cleared the terrain probably saved the S. brachyodon population from gradual deterioration and extinction. At the same time, clonal reproduction could serve as a valuable mechanism in the preservation of genetic variability. The results of the disjunct S. fruticosa population indicated heterozygote deficiency, inbreeding, hybridization with S. officinalis and population expansion. The hybridization with S. officinalis along with the abandonment of the agro-pastoral system are likely the main drivers of the strong expansion of S. fruticosa in the studied location. As many relevant findings and conclusions regarding historical and contemporary demography of individual populations or species can be

  8. Evaluation of Regenerated Catalyst for Mercury Speciation

    SciTech Connect

    Dennis Laudal

    2007-06-01

    In March of 2005, U.S. Environmental Protection Agency (EPA) promulgated the Clean Air Mercury Rule (CAMR). Mercury from coal-fired power plants was to be reduced from the current 48 to 38 tons/yr by 2010 and then 15 tons/yr by 2018. It is expected that the first phase reduction of {approx}21% will be achieved by cobenefits that will occur as a result of installing additional selective catalytic reduction (SCR) and flue gas desulfurization (FGD) systems to meet the new Clean Air Interstate Rule (CAIR). Detroit Edison (DTE) is installing SCR at all four units at its Monroe Station and will eventually install wet-FGD systems. As such, the Electric Power Research Institute (EPRI), the U.S. Department of Energy (DOE), and DTE have contracted with the Energy & Environmental Research Center (EERC) to determine the extent of mercury oxidation that occurs at Monroe Station. The EERC originally did mercury speciation sampling at Monroe Station in 2004 and then went back in 2005 to determine if any changes occurred as a result of catalyst aging. During the second test, in addition to measuring the mercury speciation at the inlet and outlet of the SCR, the EERC also completed sampling at a location between the catalyst layers. The results are shown in Table 1. In Table 1, the results show that {approx}40% of the Hg was in oxidized form (Hg{sup 2+}) at the inlet and nearly 100% Hg{sup 2+} at the outlet. The results at the midpoint were between 40% and 100%. As part of their overall strategy to reduce SCR costs, utilities and SCR vendors are attempting to regenerate catalyst layers that have degenerated over time. If these regenerated catalysts are used, the question remains as to the effect this process will have on the ability of these catalysts to oxidize mercury as well as reduce NO{sub x}. The current project is designed to measure the Hg speciation across an SCR using a regenerated catalyst. The results were compared to previous results to determine what, if any, changes

  9. Industrial ecology.

    PubMed

    Patel, C K

    1992-02-01

    Industrial ecology addresses issues that will impact future production, use, and disposal technologies; proper use of the concept should reduce significantly the resources devoted to potential remediation in the future. This cradle-to-reincarnation production philosophy includes industrial processes that are environmentally sound and products that are environmentally safe during use and economically recyclable after use without adverse impact on the environment or on the net cost to society. This will require an industry-university-government round table to set the strategy and agenda for progress. PMID:11607254

  10. Ecological Economics

    NASA Astrophysics Data System (ADS)

    Common, Michael; Stagl, Sigrid

    2005-10-01

    Taking as its starting point the interdependence of the economy and the natural environment, this book provides a comprehensive introduction to the emerging field of ecological economics. The authors, who have written extensively on the economics of sustainability, build on insights from both mainstream economics and ecological sciences. Part I explores the interdependence of the modern economy and its environment, while Part II focuses mainly on the economy and on economics. Part III looks at how national governments set policy targets and the instruments used to pursue those targets. Part IV examines international trade and institutions, and two major global threats to sustainability - climate change and biodiversity loss. Assuming no prior knowledge of economics, this textbook is well suited for use on interdisciplinary environmental science and management courses. It has extensive student-friendly features including discussion questions and exercises, keyword highlighting, real-world illustrations, further reading and website addresses. A comprehensive introduction to a developing field which will interest students from science, economics and management backgrounds A global approach to the problems of sustainability and sustainable development, issues which are increasingly prominent in political debate and policy making Filled with student-friendly features including focus areas for each chapter, keyword highlighting, real-world illustrations, discussion questions and exercises, further reading and website addresses

  11. Assembly processes of gastropod community change with horizontal and vertical zonation in ancient Lake Ohrid: a metacommunity speciation perspective

    NASA Astrophysics Data System (ADS)

    Hauffe, Torsten; Albrecht, Christian; Wilke, Thomas

    2016-05-01

    The Balkan Lake Ohrid is the oldest and most diverse freshwater lacustrine system in Europe. However, it remains unclear whether species community composition, as well as the diversification of its endemic taxa, is mainly driven by dispersal limitation, environmental filtering, or species interaction. This calls for a holistic perspective involving both evolutionary processes and ecological dynamics, as provided by the unifying framework of the "metacommunity speciation model".The current study used the species-rich model taxon Gastropoda to assess how extant communities in Lake Ohrid are structured by performing process-based metacommunity analyses. Specifically, the study aimed (1) to identifying the relative importance of the three community assembly processes and (2) to test whether the importance of these individual processes changes gradually with lake depth or discontinuously with eco-zone shifts.Based on automated eco-zone detection and process-specific simulation steps, we demonstrated that dispersal limitation had the strongest influence on gastropod community composition. However, it was not the exclusive assembly process, but acted together with the other two processes - environmental filtering and species interaction. The relative importance of the community assembly processes varied both with lake depth and eco-zones, though the processes were better predicted by the latter.This suggests that environmental characteristics have a pronounced effect on shaping gastropod communities via assembly processes. Moreover, the study corroborated the high importance of dispersal limitation for both maintaining species richness in Lake Ohrid (through its impact on community composition) and generating endemic biodiversity (via its influence on diversification processes). However, according to the metacommunity speciation model, the inferred importance of environmental filtering and biotic interaction also suggests a small but significant influence of ecological

  12. Assessing models of speciation under different biogeographic scenarios; An empirical study using multi-locus and RNA-seq analyses

    USGS Publications Warehouse

    Edwards, Taylor; Tollis, Marc; Hsieh, PingHsun; Gutenkunst, Ryan N.; Liu, Zhen; Kusumi, Kenro; Culver, Melanie; Murphy, Robert W.

    2016-01-01

    Evolutionary biology often seeks to decipher the drivers of speciation, and much debate persists over the relative importance of isolation and gene flow in the formation of new species. Genetic studies of closely related species can assess if gene flow was present during speciation, because signatures of past introgression often persist in the genome. We test hypotheses on which mechanisms of speciation drove diversity among three distinct lineages of desert tortoise in the genus Gopherus. These lineages offer a powerful system to study speciation, because different biogeographic patterns (physical vs. ecological segregation) are observed at opposing ends of their distributions. We use 82 samples collected from 38 sites, representing the entire species' distribution and generate sequence data for mtDNA and four nuclear loci. A multilocus phylogenetic analysis in *BEAST estimates the species tree. RNA-seq data yield 20,126 synonymous variants from 7665 contigs from two individuals of each of the three lineages. Analyses of these data using the demographic inference package ∂a∂i serve to test the null hypothesis of no gene flow during divergence. The best-fit demographic model for the three taxa is concordant with the *BEAST species tree, and the ∂a∂i analysis does not indicate gene flow among any of the three lineages during their divergence. These analyses suggest that divergence among the lineages occurred in the absence of gene flow and in this scenario the genetic signature of ecological isolation (parapatric model) cannot be differentiated from geographic isolation (allopatric model).

  13. Mercury speciation analysis in terrestrial animal tissues.

    PubMed

    Berzas Nevado, J J; Rodríguez Martín-Doimeadios, R C; Guzmán Bernardo, F J; Rodríguez Fariñas, N; Patiño Ropero, M J

    2012-09-15

    No previous analytical procedures are available and validated for mercury speciation analysis in terrestrial animal tissues. This analysis is a difficult task both because the expected concentrations are low, since important accumulation process are not likely to occur, and also because there are not commercially available certified reference material. Thus, an analytical methodology has been developed and validated for mercury speciation for the specific case of terrestrial animal tissues. The proposed method is based on the quantitative extraction of the species by closed-vessel microwave assisted heating with an alkaline reagent, followed by ethylation. The ethylated derivatives were then submitted to head-space solid phase microextraction with a 100 μm polidimethylsiloxane-coated fiber, and desorbed onto a gas chromatograph coupled to atomic fluorescence detection via pyrolysis unit (HS-SPME-GC-pyro-AFS). Procedural detection limits were 31.8 ng g(-1) and 52.5 ng g(-1) for CH(3)Hg(+) and Hg(2+), respectively, for liver and 35.3 ng g(-1) and 58.1 ng g(-1) for CH(3)Hg(+) and Hg(2+), respectively, for kidney. These limits of detection are 5.5 and 6 times better than the obtained without solid phase microextraction for CH(3)Hg(+) and Hg(2+), respectively. The methodology was found linear up to 120 μg L(-1) and reproducible from one day to the following. It was validated with certified reference materials NCS ZC 71001 (beef liver) and BCR No 186 (pig kidney) for total mercury, calculated as the sum of species, and with spiked red deer liver and kidney for speciation. Finally, it was applied to the analysis of samples of red deer liver, red deer kidney and wild boar kidney coming from the Almadén's mercury mining area (Ciudad Real, Spain), the longest and largest producer of mercury in the world until its closure in 2002. PMID:22967634

  14. Complementary arsenic speciation methods: A review

    NASA Astrophysics Data System (ADS)

    Nearing, Michelle M.; Koch, Iris; Reimer, Kenneth J.

    2014-09-01

    The toxicity of arsenic greatly depends on its chemical form and oxidation state (speciation) and therefore accurate determination of arsenic speciation is a crucial step in understanding its chemistry and potential risk. High performance liquid chromatography with inductively coupled mass spectrometry (HPLC-ICP-MS) is the most common analysis used for arsenic speciation but it has two major limitations: it relies on an extraction step (usually from a solid sample) that can be incomplete or alter the arsenic compounds; and it provides no structural information, relying on matching sample peaks to standard peaks. The use of additional analytical methods in a complementary manner introduces the ability to address these disadvantages. The use of X-ray absorption spectroscopy (XAS) with HPLC-ICP-MS can be used to identify compounds not extracted for HPLC-ICP-MS and provide minimal processing steps for solid state analysis that may help preserve labile compounds such as those containing arsenicsbnd sulfur bonds, which can degrade under chromatographic conditions. On the other hand, HPLC-ICP-MS is essential in confirming organoarsenic compounds with similar white line energies seen by using XAS, and identifying trace arsenic compounds that are too low to be detected by XAS. The complementary use of electrospray mass spectrometry (ESI-MS) with HPLC-ICP-MS provides confirmation of arsenic compounds identified during the HPLC-ICP-MS analysis, identification of unknown compounds observed during the HPLC-ICP-MS analysis and further resolves HPLC-ICP-MS by identifying co-eluting compounds. In the complementary use of HPLC-ICP-MS and ESI-MS, HPLC-ICP-MS helps to focus the ESI-MS selection of ions. Numerous studies have shown that the information obtained from HPLC-ICP-MS analysis can be greatly enhanced by complementary approaches.

  15. Speciation and release kinetics of zinc in contaminated paddy soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Zinc is an important nutrient for plants, but it can be toxic at high concentrations. The solubility and speciation of Zn is controlled by many factors, especially soil pH and Eh, which can vary in lowland rice culture. This study determined Zn speciation and release kinetics in Cd-Zn co-contamina...

  16. The Development and Uses of EPA's SPECIATE Database

    EPA Science Inventory

    SPECIATE is the U.S. Environmental Protection Agency's (EPA) repository of volatile organic compounds (VOC) and particulate matter (PM) speciation profiles of air pollution sources. These source profiles can be used to (l) provide input to chemical mass balance (CMB) receptor mod...

  17. Passenger car hydrocarbon emissions speciation. Final report

    SciTech Connect

    Black, F.; High, L.

    1980-05-01

    Emission factors for over 60 individual hydrocarbon compounds were determined for four passenger cars. The cars included a 1963 Chevrolet, a 1977 Mustang, and 1978 Monarch, and 1979 LTD II. The speciation data is reported for both tailpipe and evaporative emissions. The tailpipe emissions were for the urban driving conditions of the Federal Test Procedure used in motor vehicle certification. The evaporative emissions were for both diurnal and hot soak conditions, also prescribed in the Federal Test Procedure for certification. The vehicle tests involved four gasoline fuels of varying composition.

  18. Plutonium Speciation, Solubilization and Migration in Soils

    SciTech Connect

    Neu, M.; Runde, W.

    1999-06-01

    This report summarizes research completed in the first half of a three-year project. As outlined in the authors' proposal they are focusing on (1) characterizing the plutonium at an actinide contaminated site, RFETS, including determining the origin, dispersion, and speciation of the plutonium, (2) studying environmentally important plutonium complexes, primarily hydroxides and carbonates, and (3) examining the interactions of plutonium species with manganese minerals. In the first year the authors focused on site based studies. This year they continue to characterize samples from the RFETS, study the formation and structural and spectroscopic features of environmentally relevant Pu species, and begin modeling the environmental behavior of plutonium.

  19. Arsenic speciation in natural sulfidic geothermal waters

    NASA Astrophysics Data System (ADS)

    Keller, Nicole S.; Stefánsson, Andri; Sigfússon, Bergur

    2014-10-01

    The speciation of arsenic in natural sulfidic geothermal waters was studied using chemical analyses and thermodynamic aqueous speciation calculations. Samples were collected in three geothermal systems in Iceland, having contrasting H2S concentrations in the reservoir (high vs. low). The sampled waters contained 7-116 ppb As and <0.01-77.6 ppm H2S with pH of 8.56-9.60. The analytical setup used for the determination of arsenic species (Ion Chromatography-Hydride Generation Atomic Fluorescence Spectrometry, IC-HG-AFS) was field-deployed and the samples analyzed within ∼5 min of sampling in order to prevent changes upon storage, which were shown to be considerable regardless of the sample storage method used. Nine aqueous arsenic species were detected, among others arsenite (HnAsO3n-3), thioarsenite (HnAsS3n-3), arsenate (HnAsO4n-3), monothioarsenate (HnAsSO3n-3), dithioarsenate (HnAsS2O2n-3), trithioarsenate (HnAsS3O) and tetrathioarsenate (HnAsS4n-3). The results of the measured aqueous arsenic speciation in the natural geothermal waters and comparison with thermodynamic calculations reveal that the predominant factors determining the species distribution are sulfide concentration and pH. In alkaline waters with low sulfide concentrations the predominant species are AsIII oxyanions. This can be seen in samples from a liquid-only well, tapping water that is H2S-poor and free of oxygen. At intermediate sulfide concentration AsIII and AsV thio species become important and predominate at high sulfide concentration, as seen in two-phase well waters, which have high H2S concentrations in the reservoir. Upon oxidation, for instance due to mixing of the reservoir fluid with oxygenated water upon ascent to the surface, AsV oxyanions form, as well as AsV thio complexes if the sulfide concentration is intermediate to high. This oxidation process can be seen in samples from hot springs in the Geysir geothermal area. While the thermodynamic modeling allows for a first

  20. Chemoselective Boronic Ester Synthesis by Controlled Speciation**

    PubMed Central

    Fyfe, James W B; Seath, Ciaran P; Watson, Allan J B

    2014-01-01

    Control of boronic acid solution speciation is presented as a new strategy for the chemoselective synthesis of boronic esters. Manipulation of the solution equilibria within a cross-coupling milieu enables the formal homologation of aryl and alkenyl boronic acid pinacol esters. The generation of a new, reactive boronic ester in the presence of an active palladium catalyst also facilitates streamlined iterative catalytic C=C bond formation and provides a method for the controlled oligomerization of sp2-hybridized boronic esters. PMID:25267096

  1. Epidemiological characteristics of an invading parasite: Dicrocoelium dendriticum in sympatric wapiti and beef cattle in southern Alberta, Canada.

    PubMed

    Goater, Cameron P; Colwell, Douglas D

    2007-06-01

    Previous surveys of wild ungulates indicate that the liver fluke, Dicrocoelium dendriticum, was rare in the Cypress Hills area of southeastern Alberta. However, 41 of 59 wapiti (Cervus elaphus) sampled during the 2003 and 2004 hunting seasons from this region were infected, with 7 hosts containing >1,000 worms. Prevalence and mean intensity were similarly high in sympatric beef cattle and mule deer. Worm abundance in wapiti was age related, with calves containing significantly higher numbers of worms (mean +/- SD abundance = 825 +/- 1098) than adults (107 +/- 259). This pattern with host age was not evident in beef cattle, although the smaller sample sizes may be a contributing factor. These results indicate that D. dendriticum is now well established in Cypress Hills Park, circulating between at least 3 species of sympatric ungulates, including beef cattle. PMID:17626339

  2. Oligotyping reveals differences between gut microbiomes of free-ranging sympatric Namibian carnivores (Acinonyx jubatus, Canis mesomelas) on a bacterial species-like level

    PubMed Central

    Menke, Sebastian; Wasimuddin; Meier, Matthias; Melzheimer, Jörg; Mfune, John K. E.; Heinrich, Sonja; Thalwitzer, Susanne; Wachter, Bettina; Sommer, Simone

    2014-01-01

    Recent gut microbiome studies in model organisms emphasize the effects of intrinsic and extrinsic factors on the variation of the bacterial composition and its impact on the overall health status of the host. Species occurring in the same habitat might share a similar microbiome, especially if they overlap in ecological and behavioral traits. So far, the natural variation in microbiomes of free-ranging wildlife species has not been thoroughly investigated. The few existing studies exploring microbiomes through 16S rRNA gene reads clustered sequencing reads into operational taxonomic units (OTUs) based on a similarity threshold (e.g., 97%). This approach, in combination with the low resolution of target databases, generally limits the level of taxonomic assignments to the genus level. However, distinguishing natural variation of microbiomes in healthy individuals from “abnormal” microbial compositions that affect host health requires knowledge of the “normal” microbial flora at a high taxonomic resolution. This gap can now be addressed using the recently published oligotyping approach, which can resolve closely related organisms into distinct oligotypes by utilizing subtle nucleotide variation. Here, we used Illumina MiSeq to sequence amplicons generated from the V4 region of the 16S rRNA gene to investigate the gut microbiome of two free-ranging sympatric Namibian carnivore species, the cheetah (Acinonyx jubatus) and the black-backed jackal (Canis mesomelas). Bacterial phyla with proportions >0.2% were identical for both species and included Firmicutes, Fusobacteria, Bacteroidetes, Proteobacteria and Actinobacteria. At a finer taxonomic resolution, black-backed jackals exhibited 69 bacterial taxa with proportions ≥0.1%, whereas cheetahs had only 42. Finally, oligotyping revealed that shared bacterial taxa consisted of distinct oligotype profiles. Thus, in contrast to 3% OTUs, oligotyping can detect fine-scale taxonomic differences between microbiomes

  3. Oligotyping reveals differences between gut microbiomes of free-ranging sympatric Namibian carnivores (Acinonyx jubatus, Canis mesomelas) on a bacterial species-like level.

    PubMed

    Menke, Sebastian; Wasimuddin; Meier, Matthias; Melzheimer, Jörg; Mfune, John K E; Heinrich, Sonja; Thalwitzer, Susanne; Wachter, Bettina; Sommer, Simone

    2014-01-01

    Recent gut microbiome studies in model organisms emphasize the effects of intrinsic and extrinsic factors on the variation of the bacterial composition and its impact on the overall health status of the host. Species occurring in the same habitat might share a similar microbiome, especially if they overlap in ecological and behavioral traits. So far, the natural variation in microbiomes of free-ranging wildlife species has not been thoroughly investigated. The few existing studies exploring microbiomes through 16S rRNA gene reads clustered sequencing reads into operational taxonomic units (OTUs) based on a similarity threshold (e.g., 97%). This approach, in combination with the low resolution of target databases, generally limits the level of taxonomic assignments to the genus level. However, distinguishing natural variation of microbiomes in healthy individuals from "abnormal" microbial compositions that affect host health requires knowledge of the "normal" microbial flora at a high taxonomic resolution. This gap can now be addressed using the recently published oligotyping approach, which can resolve closely related