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Sample records for hosts adaptations trade-offs

  1. Loss of adaptation following reversion suggests trade-offs in host use by a seed beetle.

    PubMed

    Messina, F J; Durham, S L

    2015-10-01

    Experimental evolution has provided little support for the hypothesis that the narrow diets of herbivorous insects reflect trade-offs in performance across hosts; selection lines can sometimes adapt to an inferior novel host without a decline in performance on the ancestral host. An alternative approach for detecting trade-offs would be to measure adaptation decay after selection is relaxed, that is, when populations newly adapted to a novel host are reverted to the ancestral one. Lines of the seed beetle Callosobruchus maculatus rapidly adapted to a poor host (lentil); survival in lentil seeds increased from 2% to > 90% in < 30 generations. After the lines had reached a plateau with respect to survival in lentil, sublines were reverted to the ancestral host, mung bean. Twelve generations of reversion had little effect on performance in lentil, but after 25-35 generations, the reverted lines exhibited lower survival, slower development and smaller size. The most divergent pair of lines was then assayed on both lentil and mung bean. Performance on lentil was again much poorer in the reverted line than in the nonreverted one, but the lines performed equally well on mung bean. Moreover, the performance of the nonreverted line on mung bean remained comparable to that of the original mung-bean population. Our results thus present a paradox: loss of adaptation to lentil following reversion implies a trade-off, but the continued strong performance of lentil-adapted lines on mung bean does not. Genomic comparisons of the reverted, nonreverted and ancestral lines may resolve this paradox and determine the importance of selection vs. drift in causing a loss of adaptation following reversion.

  2. West Nile virus adaptation to ixodid tick cells is associated with phenotypic trade-offs in primary hosts.

    PubMed

    Ciota, Alexander T; Payne, Anne F; Kramer, Laura D

    2015-08-01

    West Nile virus (WNV; Flaviviridae, Flavivirus) is the most geographically widespread arthropod-borne virus (arbovirus) in the world and is found in multiple ecologically distinct settings. Despite the likelihood of frequent exposure to novel hosts, studies evaluating the capacity and correlates of host range expansions or shifts of WNV and other arboviruses are generally lacking. We utilized experimental evolution of WNV in an Amblyomma americanum tick cell line to model an invertebrate host shift and evaluate the adaptive potential of WNV outside of its primary transmission cycle. Our results demonstrate that highly significant gains in replicative ability in ixodid tick cells are attainable for WNV but are also associated with widespread genetic change and significant phenotypic costs in vitro. Decreased fitness in primary hosts could represent a barrier to frequent exploitation of hard ticks by WNV in nature.

  3. West Nile virus adaptation to ixodid tick cells is associated with phenotypic trade-offs in primary hosts

    PubMed Central

    Ciota, Alexander T.; Payne, Anne F.; Kramer, Laura D.

    2015-01-01

    West Nile virus (WNV; Flaviviridae, Flavivirus) is the most geographically widespread arthropod-borne virus (arbovirus) in the world and is found in multiple ecologically distinct settings. Despite the likelihood of frequent exposure to novel hosts, studies evaluating the capacity and correlates of host range expansions or shifts of WNV and other arboviruses are generally lacking. We utilized experimental evolution of WNV in an Amblyomma americanum tick cell line to model an invertebrate host shift and evaluate the adaptive potential of WNV outside of its primary transmission cycle. Our results demonstrate that highly significant gains in replicative ability in ixodid tick cells are attainable for WNV but are also associated with widespread genetic change and significant phenotypic costs in vitro. Decreased fitness in primary hosts could represent a barrier to frequent exploitation of hard ticks by WNV in nature. PMID:25863877

  4. Reproduction-longevity trade-offs reflect diet, not adaptation.

    PubMed

    Attisano, A; Moore, A J; Moore, P J

    2012-05-01

    A tenet of life history evolution is that allocation of limited resources results in trade-offs, such as that between reproduction and lifespan. Reproduction and lifespan are also influenced proximately by differences in the availability of specific nutrients. What is unknown is how the evolution of the ability to use a nutritionally novel diet is reflected in this fundamental trade-off. Does the evolution of the ability to use a nutritionally novel food maintain the trade-off in reproduction and longevity, or do the proximate effects of nutrition alter the adapted trade-off? We tested this by measuring trade-offs in male milkweed bugs, Oncopeltus fasciatus, fed either an adapted diet of sunflower or the ancestral diet of milkweed. Sunflower-fed males lived longer but invested less in reproduction, both in mating and fertility. Milkweed-fed males invested in both mating and fertility at the expense of survival. The evolution of an expanded diet was not constrained by the existing trade-off, but instead was accompanied by a different trade-off between reproduction and longevity. We suggest that this occurs because diets differ in promoting germ line development or longevity.

  5. Genomic evidence that resource-based trade-offs limit host-range expansion in a seed beetle.

    PubMed

    Gompert, Zachariah; Messina, Frank J

    2016-06-01

    Trade-offs have often been invoked to explain the evolution of ecological specialization. Phytophagous insects have been especially well studied, but there has been little evidence that resource-based trade-offs contribute to the evolution of host specialization in this group. Here, we combine experimental evolution and partial genome resequencing of replicate seed beetle selection lines to test the trade-off hypothesis and measure the repeatability of evolution. Bayesian estimates of selection coefficients suggest that rapid adaptation to a poor host (lentil) was mediated by standing genetic variation at multiple genetic loci and involved many of the same variants in replicate lines. Sublines that were then switched back to the ancestral host (mung bean) showed a more gradual and variable (less repeatable) loss of adaptation to lentil. We were able to obtain estimates of variance effective population sizes from genome-wide differences in allele frequencies within and between lines. These estimates were relatively large, which suggests that the contribution of genetic drift to the loss of adaptation following reversion was small. Instead, we find that some alleles that were favored on lentil were selected against during reversion on mung bean, consistent with the genetic trade-off hypothesis.

  6. The adaptive trade-off between detection and discrimination in cortical representations and behavior.

    PubMed

    Ollerenshaw, Douglas R; Zheng, He J V; Millard, Daniel C; Wang, Qi; Stanley, Garrett B

    2014-03-05

    It has long been posited that detectability of sensory inputs can be sacrificed in favor of improved discriminability and that sensory adaptation may mediate this trade-off. The extent to which this trade-off exists behaviorally and the complete picture of the underlying neural representations that likely subserve the phenomenon remain unclear. In the rodent vibrissa system, an ideal observer analysis of cortical activity measured using voltage-sensitive dye imaging in anesthetized animals was combined with behavioral detection and discrimination tasks, thalamic recordings from awake animals, and computational modeling to show that spatial discrimination performance was improved following adaptation, but at the expense of the ability to detect weak stimuli. Together, these results provide direct behavioral evidence for the trade-off between detectability and discriminability, that this trade-off can be modulated through bottom-up sensory adaptation, and that these effects correspond to important changes in thalamocortical coding properties.

  7. Tests for host-associated fitness trade-offs in the milkweed-oleander aphid.

    PubMed

    Groeters, Francis R

    1993-03-01

    The milkweed-oleander aphid, Aphis nerii (Boyer de Fonscolombe) (Homoptera: Aphididae), feeds on different milkweed species in northern California than in Puerto Rico. The hosts vary, primarily between regions, for both identity and quantity of cardenolides that the aphid sequesters for its own defense. In tests for hostassociated fitness trade-offs only one case was found in which host plant and fitness corresponded, but the effect was not significant. However, power to detect fitness trade-offs was limited and the possibility of considerable differences in fitness on a particular host for aphids from different hosts cannot be excluded. On Californian host species, among which migration is common, generalized host use could result from selection for general-purpose genotypes. However, this explanation cannot apply to generalized host use of Californian and Puerto Rican milkweeds because the regions are isolated by distance. A cardenolide sequestration mechanism that is free of substantial energy costs could provide the basis for fitness homeostasis on variable host plants that makes trade-offs unlikely even on hosts from different regions.

  8. The emergence of performance trade-offs during local adaptation: insights from experimental evolution.

    PubMed

    Bono, Lisa M; Smith, Leno B; Pfennig, David W; Burch, Christina L

    2016-12-28

    Environmental heterogeneity is considered a general explanation for phenotypic diversification, particularly when heterogeneity causes populations to diverge via local adaptation. Performance trade-offs, such as those stemming from antagonistic pleiotropy, are thought to contribute to the maintenance of diversity in this scenario. Specifically, alleles that promote adaptation in one environment are expected to promote maladaptation in alternative environments. Contrary to this expectation, however, alleles that underlie locally adaptive traits often fail to exhibit fitness costs in alternative environments. Here, we attempt to explain this paradox by reviewing the results of experimental evolution studies, including a new one of our own, that examined the evolution of trade-offs during adaptation to homogeneous versus heterogeneous environments. We propose that when pleiotropic effects vary, whether or not trade-offs emerge among diverging populations will depend critically on ecology. For example, adaptation to a locally homogeneous environment is more likely to occur by alleles that are antagonistically pleiotropic than adaptation to a locally heterogeneous environment, simply because selection is blind to costs associated with environments that are not experienced locally. Our literature review confirmed the resulting prediction that performance trade-offs were more likely to evolve during selection in homogeneous than heterogeneous environments. The nature of the environmental heterogeneity (spatial versus temporal) and the length of the experiment also contributed in predictable ways to the likelihood that performance trade-offs evolved.

  9. Trade-offs in host choice of an herbivorous insect based on parasitism and larval performance.

    PubMed

    Murphy, Shannon M; Loewy, Katrina J

    2015-11-01

    Herbivore diet breadth is predicted to evolve in response to both bottom-up and top-down selective pressures, including host plant abundance, quality and natural enemy pressure. As the relative importance and strength of interactions change over an herbivore's geographic range, local patterns of host plant use should change in response, altering local diet breadths. Fall webworm (Hyphantria cunea) is a widespread, polyphagous moth species that feeds on hundreds of plant species worldwide. Populations of fall webworm in Colorado remain polyphagous, but their diet breadth is restricted compared to other populations and thus present an ideal opportunity to test the ecological drivers of host use by a polyphagous herbivore. We investigated how host abundance, larval performance, and parasitism affect host use for fall webworm to test how these selective pressures may act individually or in concert, as well as the role of any trade-offs among fitness components, to explain diet breadth and host use. We found that host abundance was a significant predictor of host use, which suggests a selective pressure to reduce search time for oviposition sites by adult females. We also detected an important trade-off between bottom-up and top-down selective pressures: higher quality host plants also had a greater proportion of larval mortality due to parasitism. Local patterns of host plant abundance appear to narrow the set of hosts used by fall webworms in Colorado, while the trade-off between host quality and risk of parasitism helps explain the maintenance of a generalized feeding strategy within this restricted set of hosts.

  10. Host-size mediated trade-off in a parasitoid Sclerodermus harmandi.

    PubMed

    Liu, Zhudong; Xu, Bingbing; Li, Li; Sun, Jianghua

    2011-01-01

    Optimality models of host-parasitoid relationships have traditionally assumed that host quality increases as a function of host size at parasitism. However, trade-offs may play a crucial role in species evolution and should be found in host-parasitoid interactions where the host quality may differ between different sizes. Here, we investigated the effects of host size differences of Monochamus alternatus larva on foraging decisions, parasitism and related fitness in a gregarious ectoparasitoid, Sclerodermus harmandi. Two-choice and non-choice experiments were conducted with M. alternatus larvae to evaluate preference and performance of S. harmandi, respectively. Results from two-choice test showed that adult females prefer to attack large larvae rather than small larvae. In no-choice tests, adult females needed more time to paralyze large larvae than small larvae before laying eggs on the body surface of M. alternatus larvae and had lower survival and parasitism rate on those large larvae. Foraging decisions of S. harmandi led to the selection of the most profitable host size for parasitoid development, which showed more offspring gained on large M. alternatus larvae than on small larvae and got higher body weight on those large hosts. This study demonstrates the existence of trade-off occurring during host-parasitoids interactions according to host size related quality.

  11. Host-Size Mediated Trade-Off in a Parasitoid Sclerodermus harmandi

    PubMed Central

    Liu, Zhudong; Xu, Bingbing; Li, Li; Sun, Jianghua

    2011-01-01

    Optimality models of host-parasitoid relationships have traditionally assumed that host quality increases as a function of host size at parasitism. However, trade-offs may play a crucial role in species evolution and should be found in host-parasitoid interactions where the host quality may differ between different sizes. Here, we investigated the effects of host size differences of Monochamus alternatus larva on foraging decisions, parasitism and related fitness in a gregarious ectoparasitoid, Sclerodermus harmandi. Two-choice and non-choice experiments were conducted with M. alternatus larvae to evaluate preference and performance of S. harmandi, respectively. Results from two-choice test showed that adult females prefer to attack large larvae rather than small larvae. In no-choice tests, adult females needed more time to paralyze large larvae than small larvae before laying eggs on the body surface of M. alternatus larvae and had lower survival and parasitism rate on those large larvae. Foraging decisions of S. harmandi led to the selection of the most profitable host size for parasitoid development, which showed more offspring gained on large M. alternatus larvae than on small larvae and got higher body weight on those large hosts. This study demonstrates the existence of trade-off occurring during host-parasitoids interactions according to host size related quality. PMID:21853096

  12. Spiders in Motion: Demonstrating Adaptation, Structure-Function Relationships, and Trade-Offs in Invertebrates

    ERIC Educational Resources Information Center

    Bowlin, Melissa S.; McLeer, Dorothy F.; Danielson-Francois, Anne M.

    2014-01-01

    Evolutionary history and structural considerations constrain all aspects of animal physiology. Constraints on invertebrate locomotion are especially straightforward for students to observe and understand. In this exercise, students use spiders to investigate the concepts of adaptation, structure-function relationships, and trade-offs. Students…

  13. Host-associated fitness trade-offs do not limit the evolution of diet breadth in the small milkweed bug Lygaeus kalmii (Hemiptera: Lygaeidae).

    PubMed

    Fox, Charles W; Caldwell, Roy L

    1994-04-01

    Theoretical models of evolution in a temporally variable environment predict that genotypes with low variance in fitness across generations will be favored. When host use varies temporally and fitness trade-offs exist among hosts, such that an increase in performance on one host results in a correlated decrease on the other, selection for low variance in fitness across generations will favor genotypes which are generalists. Before predictions such as this can be extended to natural herbivore populations, however, it is necessary to understand the extent to which performance trade-offs limit simultaneous adaptation to multiple hosts. The experiment reported here compares two populations of the common milkweed bug, Lygaeus kalmii (Hemiptera: Lygaeidae) which differ in patterns of host usage. One population is largely restricted to milkweed (Asclepias spp.) when milkweed seeds are available, but becomes a scavenger on a large assortment of available seeds when milkweed seeds are unavailable. The second population is restricted largely to dandelion (Taraxacum officinale), without access to milkweed. We examine these populations to test for host-associated genetic trade-offs between specialization on dandelion (Taraxacum) and two species of milkweed, Asclepias fascicularis, which is low in cardiac glycoside content, and A. speciosa, which is high in cardiac glycoside content. Despite the difference in patterns of host use of the two L. kalmii populations, the populations did not differ in their performance on any of the host plants. Within each population, bugs performed nearly as well on each host, except that bugs had significantly lower survivorship on dandelion than on either milkweed species. Trade-offs in performance among hosts were not present in either population: estimated genetic correlations across hosts were strongly positive. The inability of this study to detect host-associated fitness trade-offs is consistent with most published data on this topic.

  14. Phenotypic plasticity as an adaptation to a functional trade-off.

    PubMed

    Yi, Xiao; Dean, Antony M

    2016-10-03

    We report the evolution of a phenotypically plastic behavior that circumvents the hardwired trade-off that exists when resources are partitioned between growth and motility in Escherichia coli. We propagated cultures in a cyclical environment, alternating between growth up to carrying capacity and selection for chemotaxis. Initial adaptations boosted overall swimming speed at the expense of growth. The effect of the trade-off was subsequently eased through a change in behavior; while individual cells reduced motility during exponential growth, the faction of the population that was motile increased as the carrying capacity was approached. This plastic behavior was produced by a single amino acid replacement in FliA, a regulatory protein central to the chemotaxis network. Our results illustrate how phenotypic plasticity potentiates evolvability by opening up new regions of the adaptive landscape.

  15. Trade-offs and evolution of thermal adaptation in the Irish potato famine pathogen Phytophthora infestans.

    PubMed

    Yang, Li-Na; Zhu, Wen; Wu, E-Jiao; Yang, Ce; Thrall, Peter H; Burdon, Jeremy J; Jin, Li-Ping; Shang, Li-Ping; Zhan, Jiasui

    2016-08-01

    Temperature is one of the most important environmental parameters with crucial impacts on nearly all biological processes. Due to anthropogenic activity, average air temperatures are expected to increase by a few degrees in coming decades, accompanied by an increased occurrence of extreme temperature events. Such global trends are likely to have various major impacts on human society through their influence on natural ecosystems, food production and biotic interactions, including diseases. In this study, we used a combination of statistical genetics, experimental evolution and common garden experiments to investigate the evolutionary potential for thermal adaptation in the potato late blight pathogen, Phytophthora infestans, and infer its likely response to changing temperatures. We found a trade-off associated with thermal adaptation to heterogeneous environments in P. infestans, with the degree of the trade-off peaking approximately at the pathogen's optimum growth temperature. A genetic trade-off in thermal adaptation was also evidenced by the negative association between a strain's growth rate and its thermal range for growth, and warm climates selecting for a low pathogen growth rate. We also found a mirror effect of phenotypic plasticity and genetic adaptation on growth rate. At below the optimum, phenotypic plasticity enhances pathogen's growth rate but nature selects for slower growing genotypes when temperature increases. At above the optimum, phenotypic plasticity reduces pathogen's growth rate but natural selection favours for faster growing genotypes when temperature increases further. We conclude from these findings that the growth rate of P. infestans will only be marginally affected by global warming.

  16. Gene expression clines reveal local adaptation and associated trade-offs at a continental scale

    PubMed Central

    Porcelli, Damiano; Westram, Anja M.; Pascual, Marta; Gaston, Kevin J.; Butlin, Roger K.; Snook, Rhonda R.

    2016-01-01

    Local adaptation, where fitness in one environment comes at a cost in another, should lead to spatial variation in trade-offs between life history traits and may be critical for population persistence. Recent studies have sought genomic signals of local adaptation, but often have been limited to laboratory populations representing two environmentally different locations of a species’ distribution. We measured gene expression, as a proxy for fitness, in males of Drosophila subobscura, occupying a 20° latitudinal and 11 °C thermal range. Uniquely, we sampled six populations and studied both common garden and semi-natural responses to identify signals of local adaptation. We found contrasting patterns of investment: transcripts with expression positively correlated to latitude were enriched for metabolic processes, expressed across all tissues whereas negatively correlated transcripts were enriched for reproductive processes, expressed primarily in testes. When using only the end populations, to compare our results to previous studies, we found that locally adaptive patterns were obscured. While phenotypic trade-offs between metabolic and reproductive functions across widespread species are well-known, our results identify underlying genetic and tissue responses at a continental scale that may be responsible for this. This may contribute to understanding population persistence under environmental change. PMID:27599812

  17. Spiders in motion: demonstrating adaptation, structure-function relationships, and trade-offs in invertebrates.

    PubMed

    Bowlin, Melissa S; McLeer, Dorothy F; Danielson-Francois, Anne M

    2014-03-01

    Evolutionary history and structural considerations constrain all aspects of animal physiology. Constraints on invertebrate locomotion are especially straightforward for students to observe and understand. In this exercise, students use spiders to investigate the concepts of adaptation, structure-function relationships, and trade-offs. Students measure burst and endurance performance in several taxonomic families of spiders whose ecological niches have led to different locomotory adaptations. Based on observations of spiders in their natural habitat and prior background information, students make predictions about spider performance. Students then construct their own knowledge by performing a hands-on, inquiry-based scientific experiment where the results are not necessarily known. Depending on the specific families chosen, students can observe that web-dwelling spiders have more difficulty navigating complex terrestrial terrain than ground-dwelling spiders and that there is a trade-off between burst performance and endurance performance in spiders. Our inexpensive runway design allows for countless variations on this basic experiment; for example, we have successfully used runways to show students how the performance of heterothermic ectotherms varies with temperature. High levels of intra- and interindividual variation in performance underscore the importance of using multiple trials and statistical tests. Finally, this laboratory activity can be completely student driven or standardized, depending on the instructor's preference.

  18. Life-history trade-offs and the evolution of pathogen resistance: competition between host strains.

    PubMed

    Bowers, R G; Boots, M; Begon, M

    1994-09-22

    The dynamics of a 'resistant' and a 'susceptible' strain of a self-regulated host species, in the presence of a directly transmitted pathogen, is investigated. The two strains trade off differences in pathogen transmissibility (as an aspect of pathogen resistance) against differences in birth rate and/or resistance to crowding. Depending on parameter values, either strain may be eliminated, or the two may coexist (along with the pathogen). Coexistence (polymorphism), unsurprisingly, requires an appropriate balance between the different advantages possessed by the two strains. The probability of coexistence through such a balance, however, varies nonlinearly with the degree of difference between the strains: coexistence is least likely between two very similar strains. Resistance is most likely to evolve in hosts with the characteristics of many insect pests. Moreover, with highly pathogenic pathogens, a 'susceptible' strain may exclude a 'resistant' strain because its higher growth rate is more effective against the pathogen than reduced transmissibility. 'Resistance' can reside in parameters other than those directly associated with the pathogen. Although no cycles arise and no chaotic behaviour is found, an oscillatory approach to equilibrium is commonly observed, signalling the possibility of observable oscillations in strain frequency in the (more variable) real world.

  19. Adaptive trade-off in floral morphology mediates specialization for flowers pollinated by bats and hummingbirds.

    PubMed

    Muchhala, Nathan

    2007-04-01

    Evolution toward increased specificity in pollination systems is thought to have played a central role in the diversification of angiosperms. Theory predicts that the presence of trade-offs in adapting to different pollinator types will favor specialization, yet few studies have attempted to characterize such interactions in nature. I conducted flight cage experiments with bats, hummingbirds, and artificial flowers to examine effects of corolla width on pollination. I videotaped visits to analyze pollinator behavior and counted pollen grains transferred to stigmas. Results demonstrated that flower-pollinator fit is critical to effective pollination; wide corollas guided bat snouts better, and narrow corollas guided hummingbird bills better. Poor fit resulted in variable entry angles and decreased pollen transfer. A model using these results predicts that wide corollas will be selected for when bats make more than 44% of the visits and narrow corollas when they make fewer. Intermediate corollas are never favored (i.e., generalization is always suboptimal). This is the first study to clearly document a pollinator-mediated fitness trade-off in floral morphology.

  20. Power and Performance Trade-offs for Space Time Adaptive Processing

    SciTech Connect

    Gawande, Nitin A.; Manzano Franco, Joseph B.; Tumeo, Antonino; Tallent, Nathan R.; Kerbyson, Darren J.; Hoisie, Adolfy

    2015-07-27

    Computational efficiency – performance relative to power or energy – is one of the most important concerns when designing RADAR processing systems. This paper analyzes power and performance trade-offs for a typical Space Time Adaptive Processing (STAP) application. We study STAP implementations for CUDA and OpenMP on two computationally efficient architectures, Intel Haswell Core I7-4770TE and NVIDIA Kayla with a GK208 GPU. We analyze the power and performance of STAP’s computationally intensive kernels across the two hardware testbeds. We also show the impact and trade-offs of GPU optimization techniques. We show that data parallelism can be exploited for efficient implementation on the Haswell CPU architecture. The GPU architecture is able to process large size data sets without increase in power requirement. The use of shared memory has a significant impact on the power requirement for the GPU. A balance between the use of shared memory and main memory access leads to an improved performance in a typical STAP application.

  1. Trade-offs between solar radiation management, carbon dioxide removal, emissions mitigation and adaptation

    NASA Astrophysics Data System (ADS)

    Vaughan, Naomi; Lenton, Timothy

    2010-05-01

    The possible use of solar radiation control strategies to counteract global warming is explored through a number scenarios of different anthropogenic CO2 emission reduction pathways and carbon dioxide removal interventions. Using a simple Earth system model, we illustrate the trade-offs between CO2 emission reduction, the use of carbon dioxide removal geoengineering interventions (‘negative emissions') and solar radiation management (SRM). These relationships are illustrated over a multi-centennial timescale, allowing sufficient time for the carbon-cycle to respond to the anthropogenic perturbation. The anthropogenic CO2 emission scenarios (focussing on those from fossil fuel combustion) range from more to less stringent mitigation of emissions and includes the scenario assumed in our previous work on the maximum cooling potential of different geoengineering options. Results are presented in terms of transient atmospheric CO2 concentration and global mean temperature from year 1900 to year 2500. Implementation of solar radiation control strategies requires an understanding of the timing and effect of terminating such an intervention, a so called ‘exit strategy'. The results illustrate a number of considerations regarding exit strategies, including the inherent commitment to either carbon dioxide removal interventions, or the length of time the solar radiation control mechanism must be maintained for. The impacts of the various trade-offs are also discussed in the context of adaptation and adaptive resilience. The results have a bearing on policy and long term planning by illustrating some of the important assumptions regarding implementation of solar radiation management. These include baseline assumptions about emission mitigation efforts, timescale of intervention maintenance and impacts on adaptation.

  2. An innovative cross-sectoral method for implementation of trade-off adaptation strategy assessment under climate change

    NASA Astrophysics Data System (ADS)

    Tsao, Jung-Hsuan; Tung, Ching-Pin; Liu, Tzu-Ming

    2014-05-01

    Climate change will increase sharp risks to the water and food supply in coming decades. Although impact assessment and adaptation evaluation has been discussed a lot in recent years, the importance of adaptation implement should not be ignored. In Taiwan, and elsewhere, fallow is an option of adaptation strategy under climate change. Fallow would improve the water scarcity of domestic use, but the food security might be threatened. The trade-off effects of adaptation actions are just like the side effects of medicine which cannot be avoided. Thus, managing water resources with an integrated approach will be urgent. This study aims to establish a cross-sectoral framework for implementation the trade-off adaptation strategy. Not only fallow, but also other trade-off strategy like increasing the percentage of national grain self-sufficiency would be analyzed by a rational decision process. The recent percentage of grain self-sufficiency in Taiwan is around 32, which was decreasing from 53 thirty years ago. Yet, the goal of increasing grain self-sufficiency means much more water must be used in agriculture. In that way, domestic users may face the water shortage situation. Considering the conflicts between water supply and food security, the concepts from integrative negotiation are appropriate to apply. The implementation of trade-off adaptation strategies needs to start by quantifying the utility of water supply and food security were be quantified. Next, each side's bottom line can be found by BATNA (Best Alternative to a Negotiated Agreement) and ZOPA (Zone of Possible Agreement). ZOPA provides the entire possible outcomes, and BATNA ensures the efficiency of adaptation actions by moving along with Pareto frontier. Therefore, the optimal percentage of fallow and grain self-sufficiency can be determined. Furthermore, BATNA also provides the pathway step by step which can be a guideline of adaptation strategies. This framework allows analysts and stakeholder to

  3. The evolution of life history trade-offs in viruses.

    PubMed

    Goldhill, Daniel H; Turner, Paul E

    2014-10-01

    Viruses can suffer 'life-history' trade-offs that prevent simultaneous improvement in fitness traits, such as improved intrahost reproduction at the expense of reduced extrahost survival. Here we examine reproduction-survival trade-offs and other trait compromises, highlighting that experimental evolution can reveal trade-offs and their associated mechanisms. Whereas 'curse of the pharaoh' (high virulence with extreme stability) may generally apply for viruses of eukaryotes, we suggest phages are instead likely to suffer virulence/stability trade-offs. We examine how survival/reproduction trade-offs in viruses are affected by environmental stressors, proteins governing viral host range, and organization of the virus genome. Future studies incorporating comparative biology, experimental evolution, and structural biology, could thoroughly determine how viral trade-offs evolve, and whether they transiently or permanently constrain virus adaptation.

  4. Niche partitioning between close relatives suggests trade-offs between adaptation to local environments and competition

    PubMed Central

    Peterson, Megan L; Rice, Kevin J; Sexton, Jason P

    2013-01-01

    Niche partitioning among close relatives may reflect trade-offs underlying species divergence and coexistence (e.g., between stress tolerance and competitive ability). We quantified the effects of habitat and congeneric species interactions on fitness for two closely related herbaceous plant species, Mimulus guttatus and Mimulus laciniatus, in three common habitat types within their sympatric range. Drought stress strongly reduced survival of M. guttatus in fast-drying seeps occupied by M. laciniatus, suggesting that divergent habitat adaptation maintains this niche boundary. However, neither seedling performance nor congeneric competition explained the absence of M. laciniatus from shady streams where M. guttatus thrives. M. laciniatus may be excluded from this habitat by competition with other species in the community or mature M. guttatus. Species performance and competitive ability were similar in sympatric meadows where plant community stature and the growing season length are intermediate between seeps and streams. Stochastic effects (e.g., dispersal among habitats or temporal variation) may contribute to coexistence in this habitat. Habitat adaptation, species interactions, and stochastic mechanisms influence sympatric distributions for these recently diverged species. PMID:23531923

  5. Trade-Offs of Escherichia coli Adaptation to an Intracellular Lifestyle in Macrophages

    PubMed Central

    Thompson, J. A.; Proença, J. T.; Gordo, I.

    2016-01-01

    The bacterium Escherichia coli exhibits remarkable genomic and phenotypic variation, with some pathogenic strains having evolved to survive and even replicate in the harsh intra-macrophage environment. The rate and effects of mutations that can cause pathoadaptation are key determinants of the pace at which E. coli can colonize such niches and become pathogenic. We used experimental evolution to determine the speed and evolutionary paths undertaken by a commensal strain of E. coli when adapting to intracellular life. We estimated the acquisition of pathoadaptive mutations at a rate of 10−6 per genome per generation, resulting in the fixation of more virulent strains in less than a hundred generations. Whole genome sequencing of independently evolved clones showed that the main targets of intracellular adaptation involved loss of function mutations in genes implicated in the assembly of the lipopolysaccharide core, iron metabolism and di- and tri-peptide transport, namely rfaI, fhuA and tppB, respectively. We found a substantial amount of antagonistic pleiotropy in evolved populations, as well as metabolic trade-offs, commonly found in intracellular bacteria with reduced genome sizes. Overall, the low levels of clonal interference detected indicate that the first steps of the transition of a commensal E. coli into intracellular pathogens are dominated by a few pathoadaptive mutations with very strong effects. PMID:26752723

  6. Trade-Offs of Escherichia coli Adaptation to an Intracellular Lifestyle in Macrophages.

    PubMed

    Azevedo, M; Sousa, A; Moura de Sousa, J; Thompson, J A; Proença, J T; Gordo, I

    2016-01-01

    The bacterium Escherichia coli exhibits remarkable genomic and phenotypic variation, with some pathogenic strains having evolved to survive and even replicate in the harsh intra-macrophage environment. The rate and effects of mutations that can cause pathoadaptation are key determinants of the pace at which E. coli can colonize such niches and become pathogenic. We used experimental evolution to determine the speed and evolutionary paths undertaken by a commensal strain of E. coli when adapting to intracellular life. We estimated the acquisition of pathoadaptive mutations at a rate of 10-6 per genome per generation, resulting in the fixation of more virulent strains in less than a hundred generations. Whole genome sequencing of independently evolved clones showed that the main targets of intracellular adaptation involved loss of function mutations in genes implicated in the assembly of the lipopolysaccharide core, iron metabolism and di- and tri-peptide transport, namely rfaI, fhuA and tppB, respectively. We found a substantial amount of antagonistic pleiotropy in evolved populations, as well as metabolic trade-offs, commonly found in intracellular bacteria with reduced genome sizes. Overall, the low levels of clonal interference detected indicate that the first steps of the transition of a commensal E. coli into intracellular pathogens are dominated by a few pathoadaptive mutations with very strong effects.

  7. Reproductive trade-offs in extant hunter-gatherers suggest adaptive mechanism for the Neolithic expansion.

    PubMed

    Page, Abigail E; Viguier, Sylvain; Dyble, Mark; Smith, Daniel; Chaudhary, Nikhil; Salali, Gul Deniz; Thompson, James; Vinicius, Lucio; Mace, Ruth; Migliano, Andrea Bamberg

    2016-04-26

    The Neolithic demographic transition remains a paradox, because it is associated with both higher rates of population growth and increased morbidity and mortality rates. Here we reconcile the conflicting evidence by proposing that the spread of agriculture involved a life history quality-quantity trade-off whereby mothers traded offspring survival for increased fertility, achieving greater reproductive success despite deteriorating health. We test this hypothesis by investigating fertility, mortality, health, and overall reproductive success in Agta hunter-gatherers whose camps exhibit variable levels of sedentarization, mobility, and involvement in agricultural activities. We conducted blood composition tests in 345 Agta and found that viral and helminthic infections as well as child mortality rates were significantly increased with sedentarization. Nonetheless, both age-controlled fertility and overall reproductive success were positively affected by sedentarization and participation in cultivation. Thus, we provide the first empirical evidence, to our knowledge, of an adaptive mechanism in foragers that reconciles the decline in health and child survival with the observed demographic expansion during the Neolithic.

  8. Reproductive trade-offs in extant hunter-gatherers suggest adaptive mechanism for the Neolithic expansion

    PubMed Central

    Viguier, Sylvain; Dyble, Mark; Smith, Daniel; Salali, Gul Deniz; Thompson, James; Vinicius, Lucio; Migliano, Andrea Bamberg

    2016-01-01

    The Neolithic demographic transition remains a paradox, because it is associated with both higher rates of population growth and increased morbidity and mortality rates. Here we reconcile the conflicting evidence by proposing that the spread of agriculture involved a life history quality–quantity trade-off whereby mothers traded offspring survival for increased fertility, achieving greater reproductive success despite deteriorating health. We test this hypothesis by investigating fertility, mortality, health, and overall reproductive success in Agta hunter-gatherers whose camps exhibit variable levels of sedentarization, mobility, and involvement in agricultural activities. We conducted blood composition tests in 345 Agta and found that viral and helminthic infections as well as child mortality rates were significantly increased with sedentarization. Nonetheless, both age-controlled fertility and overall reproductive success were positively affected by sedentarization and participation in cultivation. Thus, we provide the first empirical evidence, to our knowledge, of an adaptive mechanism in foragers that reconciles the decline in health and child survival with the observed demographic expansion during the Neolithic. PMID:27071109

  9. Specialization-generalization trade-off in a Bradyrhizobium symbiosis with wild legume hosts

    PubMed Central

    2014-01-01

    Background Specialized interactions help structure communities, but persistence of specialized organisms is puzzling because a generalist can occupy more environments and partake in more beneficial interactions. The “Jack-of-all-trades is a master of none” hypothesis asserts that specialists persist because the fitness of a generalist utilizing a particular habitat is lower than that of a specialist adapted to that habitat. Yet, there are many reasons to expect that mutualists will generalize on partners. Plant-soil feedbacks help to structure plant and microbial communities, but how frequently are soil-based symbiotic mutualistic interactions sufficiently specialized to influence species distributions and community composition? To address this question, we quantified realized partner richness and phylogenetic breadth of four wild-grown native legumes (Lupinus bicolor, L. arboreus, Acmispon strigosus and A. heermannii) and performed inoculation trials to test the ability of two hosts (L. bicolor and A. strigosus) to nodulate (fundamental partner richness), benefit from (response specificity), and provide benefit to (effect specificity) 31 Bradyrhizobium genotypes. Results In the wild, each Lupinus species hosted a broader genetic range of Bradyrhizobium than did either Acmispon species, suggesting that Acmispon species are more specialized. In the greenhouse, however, L. bicolor and A. strigosus did not differ in fundamental association specificity: all inoculated genotypes nodulated both hosts. Nevertheless, A. strigosus exhibited more specificity, i.e., greater variation in its response to, and effect on, Bradyrhizobium genotypes. Lupinus bicolor benefited from a broader range of genotypes but averaged less benefit from each. Both hosts obtained more fitness benefit from symbionts isolated from conspecific hosts; those symbionts in turn gained greater fitness benefit from hosts of the same species from which they were isolated. Conclusions This study affirmed

  10. Thermotolerant Yeast Strains Adapted by Laboratory Evolution Show Trade-Off at Ancestral Temperatures and Preadaptation to Other Stresses

    PubMed Central

    Nielsen, Jens

    2015-01-01

    ABSTRACT A major challenge for the production of ethanol from biomass-derived feedstocks is to develop yeasts that can sustain growth under the variety of inhibitory conditions present in the production process, e.g., high osmolality, high ethanol titers, and/or elevated temperatures (≥40°C). Using adaptive laboratory evolution, we previously isolated seven Saccharomyces cerevisiae strains with improved growth at 40°C. Here, we show that genetic adaptations to high temperature caused a growth trade-off at ancestral temperatures, reduced cellular functions, and improved tolerance of other stresses. Thermotolerant yeast strains showed horizontal displacement of their thermal reaction norms to higher temperatures. Hence, their optimal and maximum growth temperatures increased by about 3°C, whereas they showed a growth trade-off at temperatures below 34°C. Computational analysis of the physical properties of proteins showed that the lethal temperature for yeast is around 49°C, as a large fraction of the yeast proteins denature above this temperature. Our analysis also indicated that the number of functions involved in controlling the growth rate decreased in the thermotolerant strains compared with the number in the ancestral strain. The latter is an advantageous attribute for acquiring thermotolerance and correlates with the reduction of yeast functions associated with loss of respiration capacity. This trait caused glycerol overproduction that was associated with the growth trade-off at ancestral temperatures. In combination with altered sterol composition of cellular membranes, glycerol overproduction was also associated with yeast osmotolerance and improved tolerance of high concentrations of glucose and ethanol. Our study shows that thermal adaptation of yeast is suitable for improving yeast resistance to inhibitory conditions found in industrial ethanol production processes. PMID:26199325

  11. Computational and Functional Analysis of the Virus-Receptor Interface Reveals Host Range Trade-Offs in New World Arenaviruses

    PubMed Central

    Kerr, Scott A.; Jackson, Eleisha L.; Lungu, Oana I.; Meyer, Austin G.; Demogines, Ann; Ellington, Andrew D.; Georgiou, George

    2015-01-01

    ABSTRACT Animal viruses frequently cause zoonotic disease in humans. As these viruses are highly diverse, evaluating the threat that they pose remains a major challenge, and efficient approaches are needed to rapidly predict virus-host compatibility. Here, we develop a combined computational and experimental approach to assess the compatibility of New World arenaviruses, endemic in rodents, with the host TfR1 entry receptors of different potential new host species. Using signatures of positive selection, we identify a small motif on rodent TfR1 that conveys species specificity to the entry of viruses into cells. However, we show that mutations in this region affect the entry of each arenavirus differently. For example, a human single nucleotide polymorphism (SNP) in this region, L212V, makes human TfR1 a weaker receptor for one arenavirus, Machupo virus, but a stronger receptor for two other arenaviruses, Junin and Sabia viruses. Collectively, these findings set the stage for potential evolutionary trade-offs, where natural selection for resistance to one virus may make humans or rodents susceptible to other arenavirus species. Given the complexity of this host-virus interplay, we propose a computational method to predict these interactions, based on homology modeling and computational docking of the virus-receptor protein-protein interaction. We demonstrate the utility of this model for Machupo virus, for which a suitable cocrystal structural template exists. Our model effectively predicts whether the TfR1 receptors of different species will be functional receptors for Machupo virus entry. Approaches such at this could provide a first step toward computationally predicting the “host jumping” potential of a virus into a new host species. IMPORTANCE We demonstrate how evolutionary trade-offs may exist in the dynamic evolutionary interplay between viruses and their hosts, where natural selection for resistance to one virus could make humans or rodents susceptible

  12. Trading-off tolerable risk with climate change adaptation costs in water supply systems

    NASA Astrophysics Data System (ADS)

    Borgomeo, Edoardo; Mortazavi-Naeini, Mohammad; Hall, Jim W.; O'Sullivan, Michael J.; Watson, Tim

    2016-02-01

    Choosing secure water resource management plans inevitably requires trade-offs between risks (for a variety of stakeholders), costs, and other impacts. We have previously argued that water resources planning should focus upon metrics of risk of water restrictions, accompanied by extensive simulation and scenario-based exploration of uncertainty. However, the results of optimization subject to risk constraints can be sensitive to the specification of tolerable risk, which may not be precisely or consistently defined by different stakeholders. In this paper, we recast the water resources planning problem as a multiobjective optimization problem to identify least cost schemes that satisfy a set of criteria for tolerable risk, where tolerable risk is defined in terms of the frequency of water use restrictions of different levels of severity. Our proposed method links a very large ensemble of climate model projections to a water resource system model and a multiobjective optimization algorithm to identify a Pareto optimal set of water resource management plans across a 25 years planning period. In a case study application to the London water supply system, we identify water resources management plans that, for a given financial cost, maximize performance with respect to one or more probabilistic criteria. This illustrates trade-offs between financial costs of plans and risk, and between risk criteria for four different severities of water use restrictions. Graphical representation of alternative sequences of investments in the Pareto set helps to identify water management options for which there is a robust case for including them in the plan.

  13. Trade-offs of host use between generalist and specialist Helicoverpa sibling species: adult oviposition and larval performance.

    PubMed

    Liu, Zhudong; Scheirs, Jan; Heckel, David G

    2012-02-01

    Much attention has been paid to the question of the relative importance of female behaviour versus larval feeding capacities in determining the host range of herbivorous insects. Host-use trade-offs displayed by generalist and specialist sister species of the genus Helicoverpa were evaluated to examine the relationship between maternal choice and offspring performance. The prediction of optimal oviposition theory, that females will choose to lay eggs on plants on which their offspring perform best as larvae, was tested by measuring oviposition preference and larval performance of Helicoverpa armigera and H. assulta on tobacco, sunflower, and hot pepper. These two measures were more highly correlated in the specialist H. assulta. Both species exhibited the same oviposition preference ranking: tobacco > sunflower > hot pepper. H. armigera larvae preferred sunflower, followed by tobacco and hot pepper; while H. assulta larvae preferred tobacco to sunflower and hot pepper, consistent with their mothers' oviposition preference. Duration of the total period from egg to adult emergence for each species was significantly shorter on the host plant preferred by the larvae. H. assulta had shorter larval duration and higher relative growth rate than H. armigera on tobacco and hot pepper, and vice versa for sunflower, indicating species differences in host utilization. Thus, while only the specialist H. assulta displayed the predicted optimal oviposition pattern, females of both species show the least preference for the plant on which their offspring perform worst. Selection for optimal oviposition may be stronger on the specialist, which has fewer choices and lower lifetime fecundity than the generalist.

  14. Heterogeneity-mediated cellular adaptation and its trade-off: searching for the general principles of diseases.

    PubMed

    Heng, Henry H

    2016-07-15

    Big-data-omics have promised the success of precision medicine. However, most common diseases belong to adaptive systems where the precision is all but difficult to achieve. In this commentary, I propose a heterogeneity-mediated cellular adaptive model to search for the general model of diseases, which also illustrates why in most non-infectious non-Mendelian diseases the involvement of cellular evolution is less predictable when gene profiles are used. This synthesis is based on the following new observations/concepts: 1) the gene only codes "parts inheritance" while the genome codes "system inheritance" or the entire blueprint; 2) the nature of somatic genetic coding is fuzzy rather than precise, and genetic alterations are not just the results of genetic error but are in fact generated from internal adaptive mechanisms in response to environmental dynamics; 3) stress-response is less specific within cellular evolutionary context when compared to known biochemical specificities; and 4) most medical interventions have their unavoidable uncertainties and often can function as negative harmful stresses as trade-offs. The acknowledgment of diseases as adaptive systems calls for the action to integrate genome- (not simply individual gene-) mediated cellular evolution into molecular medicine.

  15. The lag-phase during diauxic growth is a trade-off between fast adaptation and high growth rate

    NASA Astrophysics Data System (ADS)

    Chu, Dominique; Barnes, David J.

    2016-04-01

    Bi-phasic or diauxic growth is often observed when microbes are grown in a chemically defined medium containing two sugars (for example glucose and lactose). Typically, the two growth stages are separated by an often lengthy phase of arrested growth, the so-called lag-phase. Diauxic growth is usually interpreted as an adaptation to maximise population growth in multi-nutrient environments. However, the lag-phase implies a substantial loss of growth during the switch-over. It therefore remains unexplained why the lag-phase is adaptive. Here we show by means of a stochastic simulation model based on the bacterial PTS system that it is not possible to shorten the lag-phase without incurring a permanent growth-penalty. Mechanistically, this is due to the inherent and well established limitations of biological sensors to operate efficiently at a given resource cost. Hence, there is a trade-off between lost growth during the diauxic switch and the long-term growth potential of the cell. Using simulated evolution we predict that the lag-phase will evolve depending on the distribution of conditions experienced during adaptation. In environments where switching is less frequently required, the lag-phase will evolve to be longer whereas, in frequently changing environments, the lag-phase will evolve to be shorter.

  16. Evaluating Trade-Offs of Human Involvement in Self-Adaptive Systems

    DTIC Science & Technology

    2015-05-14

    react in a timely manner when situations that demand changes to the system at runtime arise. In contrast, approaches developed over the last decade...Other approaches in self-adaptation that rely on selection of adaptation strategies defined by a designer at development time [4, 12] are also able to...tuples adjacent to tree branches indicate aggregate impact corresponding to the child sub-tree (including adjustments due to branch proba- bilities). Once

  17. Reliable Adaptive Data Aggregation Route Strategy for a Trade-off between Energy and Lifetime in WSNs

    PubMed Central

    Guo, Wenzhong; Hong, Wei; Zhang, Bin; Chen, Yuzhong; Xiong, Naixue

    2014-01-01

    Mobile security is one of the most fundamental problems in Wireless Sensor Networks (WSNs). The data transmission path will be compromised for some disabled nodes. To construct a secure and reliable network, designing an adaptive route strategy which optimizes energy consumption and network lifetime of the aggregation cost is of great importance. In this paper, we address the reliable data aggregation route problem for WSNs. Firstly, to ensure nodes work properly, we propose a data aggregation route algorithm which improves the energy efficiency in the WSN. The construction process achieved through discrete particle swarm optimization (DPSO) saves node energy costs. Then, to balance the network load and establish a reliable network, an adaptive route algorithm with the minimal energy and the maximum lifetime is proposed. Since it is a non-linear constrained multi-objective optimization problem, in this paper we propose a DPSO with the multi-objective fitness function combined with the phenotype sharing function and penalty function to find available routes. Experimental results show that compared with other tree routing algorithms our algorithm can effectively reduce energy consumption and trade off energy consumption and network lifetime. PMID:25215944

  18. Trade-offs, geography, and limits to thermal adaptation in a tide pool copepod.

    PubMed

    Kelly, Morgan W; Grosberg, Richard K; Sanford, Eric

    2013-06-01

    Antagonistic correlations among traits may slow the rate of adaptation to a changing environment. The tide pool copepod Tigriopus californicus is locally adapted to temperature, but within populations, the response to selection for increased heat tolerance plateaus rapidly, suggesting either limited variation within populations or costs of increased tolerance. To measure possible costs of thermal tolerance, we selected for increased upper lethal limits for 10 generations in 22 lines of T. californicus from six populations. Then, for each line, we measured six fitness-related traits. Selected lines showed an overall increase in male and female body sizes, fecundity, and starvation resistance, suggesting a small benefit from (rather than costs of) increased tolerance. The effect of selection on correlated traits also varied significantly by population for five traits, indicating that the genetic basis for the selection response differed among populations. Our results suggest that adaptation was limited by the presence of variation within isolated populations rather than by costs of increased tolerance.

  19. Forest management under climatic and social uncertainty: trade-offs between reducing climate change impacts and fostering adaptive capacity.

    PubMed

    Seidl, Rupert; Lexer, Manfred J

    2013-01-15

    The unabated continuation of anthropogenic greenhouse gas emissions and the lack of an international consensus on a stringent climate change mitigation policy underscore the importance of adaptation for coping with the all but inevitable changes in the climate system. Adaptation measures in forestry have particularly long lead times. A timely implementation is thus crucial for reducing the considerable climate vulnerability of forest ecosystems. However, since future environmental conditions as well as future societal demands on forests are inherently uncertain, a core requirement for adaptation is robustness to a wide variety of possible futures. Here we explicitly address the roles of climatic and social uncertainty in forest management, and tackle the question of robustness of adaptation measures in the context of multi-objective sustainable forest management (SFM). We used the Austrian Federal Forests (AFF) as a case study, and employed a comprehensive vulnerability assessment framework based on ecosystem modeling, multi-criteria decision analysis, and practitioner participation. We explicitly considered climate uncertainty by means of three climate change scenarios, and accounted for uncertainty in future social demands by means of three societal preference scenarios regarding SFM indicators. We found that the effects of climatic and social uncertainty on the projected performance of management were in the same order of magnitude, underlining the notion that climate change adaptation requires an integrated social-ecological perspective. Furthermore, our analysis of adaptation measures revealed considerable trade-offs between reducing adverse impacts of climate change and facilitating adaptive capacity. This finding implies that prioritization between these two general aims of adaptation is necessary in management planning, which we suggest can draw on uncertainty analysis: Where the variation induced by social-ecological uncertainty renders measures aiming to

  20. Pupil diameter predicts changes in the exploration-exploitation trade-off: evidence for the adaptive gain theory.

    PubMed

    Jepma, Marieke; Nieuwenhuis, Sander

    2011-07-01

    The adaptive regulation of the balance between exploitation and exploration is critical for the optimization of behavioral performance. Animal research and computational modeling have suggested that changes in exploitative versus exploratory control state in response to changes in task utility are mediated by the neuromodulatory locus coeruleus-norepinephrine (LC-NE) system. Recent studies have suggested that utility-driven changes in control state correlate with pupil diameter, and that pupil diameter can be used as an indirect marker of LC activity. We measured participants' pupil diameter while they performed a gambling task with a gradually changing payoff structure. Each choice in this task can be classified as exploitative or exploratory using a computational model of reinforcement learning. We examined the relationship between pupil diameter, task utility, and choice strategy (exploitation vs. exploration), and found that (i) exploratory choices were preceded by a larger baseline pupil diameter than exploitative choices; (ii) individual differences in baseline pupil diameter were predictive of an individual's tendency to explore; and (iii) changes in pupil diameter surrounding the transition between exploitative and exploratory choices correlated with changes in task utility. These findings provide novel evidence that pupil diameter correlates closely with control state, and are consistent with a role for the LC-NE system in the regulation of the exploration-exploitation trade-off in humans.

  1. The adaptive nature of eye movements in linguistic tasks: how payoff and architecture shape speed-accuracy trade-offs.

    PubMed

    Lewis, Richard L; Shvartsman, Michael; Singh, Satinder

    2013-07-01

    We explore the idea that eye-movement strategies in reading are precisely adapted to the joint constraints of task structure, task payoff, and processing architecture. We present a model of saccadic control that separates a parametric control policy space from a parametric machine architecture, the latter based on a small set of assumptions derived from research on eye movements in reading (Engbert, Nuthmann, Richter, & Kliegl, 2005; Reichle, Warren, & McConnell, 2009). The eye-control model is embedded in a decision architecture (a machine and policy space) that is capable of performing a simple linguistic task integrating information across saccades. Model predictions are derived by jointly optimizing the control of eye movements and task decisions under payoffs that quantitatively express different desired speed-accuracy trade-offs. The model yields distinct eye-movement predictions for the same task under different payoffs, including single-fixation durations, frequency effects, accuracy effects, and list position effects, and their modulation by task payoff. The predictions are compared to-and found to accord with-eye-movement data obtained from human participants performing the same task under the same payoffs, but they are found not to accord as well when the assumptions concerning payoff optimization and processing architecture are varied. These results extend work on rational analysis of oculomotor control and adaptation of reading strategy (Bicknell & Levy, ; McConkie, Rayner, & Wilson, 1973; Norris, 2009; Wotschack, 2009) by providing evidence for adaptation at low levels of saccadic control that is shaped by quantitatively varying task demands and the dynamics of processing architecture.

  2. Host plant preference and performance of the sibling species of butterflies Leptidea sinapis and Leptidea reali: a test of the trade-off hypothesis for food specialisation.

    PubMed

    Friberg, Magne; Wiklund, Christer

    2009-02-01

    A large proportion of phytophagous insect species are specialised on one or a few host plants, and female host plant preference is predicted to be tightly linked to high larval survival and performance on the preferred plant(s). Specialisation is likely favoured by selection under stable circumstances, since different host plant species are likely to differ in suitability-a pattern usually explained by the "trade-off hypothesis", which posits that increased performance on a given plant comes at a cost of decreased performance on other plants. Host plant specialisation is also ascribed an important role in host shift speciation, where different incipient species specialise on different host plants. Hence, it is important to determine the role of host plants when studying species divergence and niche partitioning between closely related species, such as the butterfly species pair Leptidea sinapis and Leptidea reali. In Sweden, Leptidea sinapis is a habitat generalist, appearing in both forests and meadows, whereas Leptidea reali is specialised on meadows. Here, we study the female preference and larval survival and performance in terms of growth rate, pupal weight and development time on the seven most-utilised host plants. Both species showed similar host plant rank orders, and larvae survived and performed equally well on most plants with the exceptions of two rarely utilised forest plants. We therefore conclude that differences in preference or performance on plants from the two habitats do not drive, or maintain, niche separation, and we argue that the results of this study do not support the trade-off hypothesis for host plant specialisation, since the host plant generalist Leptidea sinapis survived and performed as well on the most preferred meadow host plant Lathyrus pratensis as did Leptidea reali although the generalist species also includes other plants in its host range.

  3. Adaptive trade-offs in juvenile salmonid metabolism associated with habitat partitioning between coho salmon and steelhead trout in coastal streams.

    PubMed

    Van Leeuwen, Travis E; Rosenfeld, Jordan S; Richards, Jeffrey G

    2011-09-01

    1. Adaptive trade-offs are fundamental to the evolution of diversity and the coexistence of similar taxa and occur when complimentary combinations of traits maximize efficiency of resource exploitation or survival at different points on environmental gradients. 2. Standard metabolic rate (SMR) is a key physiological trait that reflects adaptations to baseline metabolic performance, whereas active metabolism reflects adaptations to variable metabolic output associated with performance related to foraging, predator avoidance, aggressive interactions or migratory movements. Benefits of high SMR and active metabolism may change along a resource (productivity) gradient, indicating that a trade-off exists among active metabolism, resting metabolism and energy intake. 3. We measured and compared SMR, maximal metabolic rate (MMR), aerobic scope (AS), swim performance (UCrit) and growth of juvenile hatchery and wild steelhead and coho salmon held on high- and low-food rations in order to better understand the potential significance of variation in SMR to growth, differentiation between species, and patterns of habitat use along a productivity gradient. 4. We found that differences in SMR, MMR, AS, swim performance and growth rate between steelhead trout and coho salmon were reduced in hatchery-reared fish compared with wild fish. Wild steelhead had a higher MMR, AS, swim performance and growth rate than wild coho, but adaptations between species do not appear to involve differences in SMR or to trade-off increased growth rate against lower swim performance, as commonly observed for high-growth strains. Instead, we hypothesize that wild steelhead may be trading off higher growth rate for lower food consumption efficiency, similar to strategies adopted by anadromous vs. resident brook trout and Atlantic salmon vs. brook trout. This highlights potential differences in food consumption and digestion strategies as cryptic adaptations ecologically differentiating salmonid species

  4. Maintenance of brucellosis in Yellowstone bison: linking seasonal food resources, host-pathogen interaction, and life-history trade-offs.

    PubMed

    Treanor, John J; Geremia, Chris; Ballou, Michael A; Keisler, Duane H; White, Patrick J; Cox, John J; Crowley, Philip H

    2015-09-01

    The seasonal availability of food resources is an important factor shaping the life-history strategies of organisms. During times of nutritional restriction, physiological trade-offs can induce periods of immune suppression, thereby increasing susceptibility to infectious disease. Our goal was to provide a conceptual framework describing how the endemic level bovine brucellosis (Brucella abortus) may be maintained in Yellowstone bison based on the seasonality of food resources and the life-history strategies of the host and pathogen. Our analysis was based on active B. abortus infection (measured via bacterial culture), nutritional indicators (measured as metabolites and hormones in plasma), and carcass measurements of 402 slaughtered bison. Data from Yellowstone bison were used to investigate (1) whether seasonal changes in diet quality affect nutritional condition and coincide with the reproductive needs of female bison; (2) whether active B. abortus infection and infection intensities vary with host nutrition and nutritional condition; and (3) the evidence for seasonal changes in immune responses, which may offer protection against B. abortus, in relation to nutritional condition. Female bison experienced a decline in nutritional condition during winter as reproductive demands of late gestation increased while forage quality and availability declined. Active B. abortus infection was negatively associated with bison age and nutritional condition, with the intensity of infection negatively associated with indicators of nutrition (e.g., dietary protein and energy) and body weight. Data suggest that protective cell-mediated immune responses may be reduced during the B. abortus transmission period, which coincides with nutritional insufficiencies and elevated reproductive demands during spring. Our results illustrate how seasonal food restriction can drive physiological trade-offs that suppress immune function and create infection and transmission opportunities

  5. Balancing competing motives: adaptive trade-offs are necessary to satisfy disease avoidance and interpersonal affiliation goals.

    PubMed

    Sacco, Donald F; Young, Steven G; Hugenberg, Kurt

    2014-12-01

    The current research provides novel evidence for motivational trade-offs between the two fundamental human goals of pursuing social affiliation and avoiding disease. In Study 1, participants completed a writing prime that manipulated inclusionary status and found that socially excluded participants indicated lower feelings of current disease susceptibility compared with control and socially included participants. In Study 2, participants were included or excluded via Cyberball and then indicated their preferences for symmetrical versus asymmetrical faces. Socially excluded participants displayed lower preferences for symmetrical faces--a cue associated with greater disease resistance. Finally, in Study 3, participants were primed with either disease threat or a general negative affective state and then indicated their current affiliation interest. Activated disease concerns uniquely led participants to display less interest in social affiliation. Taken together, affiliation needs result in disease avoidance down-regulation to aid reaffiliation, whereas disease concerns result in affiliation down-regulation to facilitate pathogen avoidance.

  6. Towards adaptive management of the natural capital: Disentangling trade-offs among marine activities and seagrass meadows.

    PubMed

    Bas Ventín, Leticia; de Souza Troncoso, Jesús; Villasante, Sebastián

    2015-12-15

    This paper investigates the ecological, social and institutional dimensions of the synergies and trade-offs between seagrasses and human activities operating in the Natura 2000 protected site of San Simón Bay (Galicia, NW Spain). By means of a multidisciplinary approach that brings together the development of a biological inventory combined with participatory mapping processes we get key spatial and contextual understanding regarding how, where and why marine users interact with seagrasses and how seagrasses are considered in policy making. The results highlight the fisheries' reliance on seagrass meadows and the controversial links with shellfisheries. The study also reveals unresolved conflicts among those management plans that promote the protection of natural values and those responsible for the exploitation of marine resources. We conclude that the adoption of pre-planning bottom-up participatory processes is crucial for the design of realistic strategies where both seagrasses and human activities were considered as a couple system.

  7. Constraints on adaptive evolution: the functional trade-off between reproduction and fast-start swimming performance in the Trinidadian guppy (Poecilia reticulata).

    PubMed

    Ghalambor, Cameron K; Reznick, David N; Walker, Jeffrey A

    2004-07-01

    The empirical study of natural selection reveals that adaptations often involve trade-offs between competing functions. Because natural selection acts on whole organisms rather than isolated traits, adaptive evolution may be constrained by the interaction between traits that are functionally integrated. Yet, few attempts have been made to characterize how and when such constraints are manifested or whether they limit the adaptive divergence of populations. Here we examine the consequences of adaptive life-history evolution on locomotor performance in the live-bearing guppy. In response to increased predation from piscivorous fish, Trinidadian guppies evolve an increased allocation of resources toward reproduction. These populations are also under strong selection for rapid fast-start swimming performance to evade predators. Because embryo development increases a female's wet mass as she approaches parturition, an increased investment in reproductive allocation should impede fast-start performance. We find evidence for adaptive but constrained evolution of fast-start swimming performance in laboratory trials conducted on second-generation lab-reared fish. Female guppies from high-predation localities attain a faster acceleration and velocity and travel a greater distance during fast-start swimming trials. However, velocity and distance traveled decline more rapidly over the course of pregnancy in these same females, thus reducing the magnitude of divergence in swimming performance between high- and low-predation populations. This functional trade-off between reproduction and swimming performance reveals how different aspects of the phenotype are integrated and highlights the complexity of adaptation at the whole-organism level.

  8. Graphical analysis of evolutionary trade-off in sylvatic Trypanosoma cruzi transmission modes.

    PubMed

    Kribs-Zaleta, Christopher M

    2014-07-21

    The notion of evolutionary trade-off (one attribute increasing at the expense of another) is central to the evolution of traits, well-studied especially in life-history theory, where a framework first developed by Levins illustrates how internal (genetics) and external (fitness landscapes) forces interact to shape an organism׳s ongoing adaptation. This manuscript extends this framework to the context of vector-borne pathogens, with the example of Trypanosoma cruzi (the etiological agent of Chagas׳ disease) adapting via trade-off among three different infection routes to hosts-stercorarian, vertical, and oral-in response to an epidemiological landscape that involves both hosts and vectors (where, in particular, parasite evolution depends not on parasite density but on relative host and vector densities). Using a fitness measure derived from an invasion reproductive number, this study analyzes several different trade-off scenarios in cycles involving raccoons or woodrats, including a proper three-way trade-off (two independent parameters). Results indicate that selection favors oral transmission to raccoons but classical stercorarian transmission to woodrats even under the same predation rate, with vertical (congenital) transmission favored only when aligned with dominant oral transmission or (at trace levels) under a weak (convex) trade-off.

  9. Evolution, the loss of diversity and the role of trade-offs.

    PubMed

    Best, Alex; Bowers, Roger; White, Andy

    2015-06-01

    We investigate how the loss of previously evolved diversity in host resistance to disease is dependent on the complexity of the underlying evolutionary trade-off. Working within the adaptive dynamics framework, using graphical tools (pairwise invasion plots, PIPs; trait evolution plots, TEPs) and algebraic analysis we consider polynomial trade-offs of increasing degree. Our focus is on the evolutionary trajectory of the dimorphic population after it has been attracted to an evolutionary branching point. We show that for sufficiently complex trade-offs (here, polynomials of degree three or higher) the resulting invasion boundaries can form closed 'oval' areas of invadability and strategy coexistence. If no attracting singular strategies exist within this region, then the population is destined to evolve outside of the region of coexistence, resulting in the loss of one strain. In particular, the loss of diversity in this model always occurs in such a way that the remaining strain is not attracted back to the branching point but to an extreme of the trade-off, meaning the diversity is lost forever. We also show similar results for a non-polynomial but complex trade-off, and for a different eco-evolutionary model. Our work further highlights the importance of trade-offs to evolutionary behaviour.

  10. Trade-offs between light interception and leaf water shedding: a comparison of shade- and sun-adapted species in a subtropical rainforest.

    PubMed

    Meng, Fengqun; Cao, Rui; Yang, Dongmei; Niklas, Karl J; Sun, Shucun

    2014-01-01

    Species in high-rainfall regions have two major alternative approaches to quickly drain off water, i.e., increasing leaf inclination angles relative to the horizontal plane, or developing long leaf drip tips. We hypothesized that shade-adapted species will have more pronounced leaf drip tips but not greater inclination angles (which can reduce the ability to intercept light) compared to sun-adapted species and that length of leaf drip tips will be negatively correlated with photosynthetic capacity [characterized by light-saturated net photosynthetic rates (Amax), associated light compensation points (LCP), and light saturation points (LSP)]. We tested this hypothesis by measuring morphological and physiological traits that are associated with light-interception and water shedding for seven shade-adapted shrub species, ten sun-adapted understory shrub species, and 15 sun-adapted tree species in a subtropical Chinese rainforest, where mean annual precipitation is around 1,600 mm. Shade-adapted understory species had lower LMA, Amax, LSP, and LCP compared to understory or canopy sun-adapted species; their leaf and twig inclination angles were significantly smaller and leaf drip tips were significantly longer than those in sun-adapted species. This suggests that shade-adapted understory species tend to develop pronounced leaf drip tips but not large leaf inclination angles to shed water. The length of leaf drip tips was negatively correlated with leaf inclination angles and photosynthetic capacity. These relationships were consistent between ordinary regression and phylogenetic generalized least squares analyses. Our study illustrates the trade-offs between light interception and leaf water shedding and indicates that length of leaf drip tips can be used as an indicator of adaptation to shady conditions and overall photosynthetic performance of shrub species in subtropical rainforests.

  11. Valuing the recreational benefits of wetland adaptation to climate change: a trade-off between species' abundance and diversity.

    PubMed

    Faccioli, Michela; Riera Font, Antoni; Torres Figuerola, Catalina M

    2015-03-01

    Climate change will further exacerbate wetland deterioration, especially in the Mediterranean region. On the one side, it will accelerate the decline in the populations and species of plants and animals, this resulting in an impoverishment of biological abundance. On the other one, it will also promote biotic homogenization, resulting in a loss of species' diversity. In this context, different climate change adaptation policies can be designed: those oriented to recovering species' abundance and those aimed at restoring species' diversity. Based on the awareness that knowledge about visitors' preferences is crucial to better inform policy makers and secure wetlands' public use and conservation, this paper assesses the recreational benefits of different adaptation options through a choice experiment study carried out in S'Albufera wetland (Mallorca). Results show that visitors display positive preferences for an increase in both species' abundance and diversity, although they assign a higher value to the latter, thus suggesting a higher social acceptability of policies pursuing wetlands' differentiation. This finding acquires special relevance not only for adaptation management in wetlands but also for tourism planning, as most visitors to S'Albufera are tourists. Thus, given the growing competition to attract visitors and the increasing demand for high environmental quality and unique experiences, promoting wetlands' differentiation could be a good strategy to gain competitive advantage over other wetland areas and tourism destinations.

  12. Valuing the Recreational Benefits of Wetland Adaptation to Climate Change: A Trade-off Between Species' Abundance and Diversity

    NASA Astrophysics Data System (ADS)

    Faccioli, Michela; Riera Font, Antoni; Torres Figuerola, Catalina M.

    2015-03-01

    Climate change will further exacerbate wetland deterioration, especially in the Mediterranean region. On the one side, it will accelerate the decline in the populations and species of plants and animals, this resulting in an impoverishment of biological abundance. On the other one, it will also promote biotic homogenization, resulting in a loss of species' diversity. In this context, different climate change adaptation policies can be designed: those oriented to recovering species' abundance and those aimed at restoring species' diversity. Based on the awareness that knowledge about visitors' preferences is crucial to better inform policy makers and secure wetlands' public use and conservation, this paper assesses the recreational benefits of different adaptation options through a choice experiment study carried out in S'Albufera wetland (Mallorca). Results show that visitors display positive preferences for an increase in both species' abundance and diversity, although they assign a higher value to the latter, thus suggesting a higher social acceptability of policies pursuing wetlands' differentiation. This finding acquires special relevance not only for adaptation management in wetlands but also for tourism planning, as most visitors to S'Albufera are tourists. Thus, given the growing competition to attract visitors and the increasing demand for high environmental quality and unique experiences, promoting wetlands' differentiation could be a good strategy to gain competitive advantage over other wetland areas and tourism destinations.

  13. No adaptation of a herbivore to a novel host but loss of adaptation to its native host

    PubMed Central

    Grosman, Amir H.; Molina-Rugama, Adrián J.; Mendes-Dias, Rondinelli; Sabelis, Maurice W.; Menken, Steph B.J.; Pallini, Angelo; Breeuwer, Johannes A.J.; Janssen, Arne

    2015-01-01

    Most herbivorous arthropods are host specialists and the question is which mechanisms drive the evolution of such specialization. The theory of antagonistic pleiotropy suggests that there is a trade-off between adaptation of herbivores to a novel host and their native host. The mutation accumulation hypothesis proposes that herbivores on a novel host lose their adaptation to the native host through the accumulation of mutations with negligible effects on performance on the novel host. Experimental evidence for either of the two hypotheses is scarce. We compared the fitness of two sympatric moth strains from an introduced host and a native host. The strain from the novel host did not perform better on this host than the strain from the native host. The strain from the novel host performed less well on the native host than did the strain from the native host. Hence, selection on the novel host did not result in noticeable gain in performance, but adaptation to the native host was lost. These results are more readily explained by the mutation-accumulation hypothesis than by the trade-off hypothesis. PMID:26577696

  14. Effects of parasite pressure on parasite mortality and reproductive output in a rodent-flea system: inferring host defense trade-offs.

    PubMed

    Warburton, Elizabeth M; Kam, Michael; Bar-Shira, Enav; Friedman, Aharon; Khokhlova, Irina S; Koren, Lee; Asfur, Mustafa; Geffen, Eli; Kiefer, Daniel; Krasnov, Boris R; Degen, A Allan

    2016-09-01

    Evaluating host resistance via parasite fitness helps place host-parasite relationships within evolutionary and ecological contexts; however, few studies consider both these processes simultaneously. We investigated how different levels of parasite pressure affect parasite mortality and reproductive success in relationship to host defense efforts, using the rodent Gerbillus nanus and the flea Xenopsylla conformis as a host-parasite system. Fifteen immune-naïve male rodents were infested with 20, 50, or 100 fleas for four weeks. During this time number of new imagoes produced per adult flea (our flea reproductive output metric), flea mortality, and change in circulating anti-flea immunoglobulin G (our measure of adaptive immune defense) were monitored. Three hypotheses guided this work: (1) increasing parasite pressure would heighten host defenses; (2) parasite mortality would increase and parasite reproductive output would decrease with increasing investment in host defense; and (3) hosts under high parasite pressure could invest in behavioral and/or immune responses. We predicted that at high infestation levels (a) parasite mortality would increase; (b) flea reproductive output per individual would decrease; and (c) host circulating anti-flea antibody levels would increase. The hypotheses were partially supported. Flea mortality significantly increased and flea reproductive output significantly decreased as flea pressure increased. Host adaptive immune defense did not significantly change with increasing flea pressure. Therefore, we inferred that investment in host behavioral defense, either alone or in combination with density-dependent effects, may be more efficient at increasing flea mortality and decreasing flea reproductive output than antibody production during initial infestation in this system.

  15. Host plant adaptation in Drosophila mettleri populations.

    PubMed

    Castrezana, Sergio; Bono, Jeremy M

    2012-01-01

    The process of local adaptation creates diversity among allopatric populations, and may eventually lead to speciation. Plant-feeding insect populations that specialize on different host species provide an excellent opportunity to evaluate the causes of ecological specialization and the subsequent consequences for diversity. In this study, we used geographically separated Drosophila mettleri populations that specialize on different host cacti to examine oviposition preference for and larval performance on an array of natural and non-natural hosts (eight total). We found evidence of local adaptation in performance on saguaro cactus (Carnegiea gigantea) for populations that are typically associated with this host, and to chemically divergent prickly pear species (Opuntia spp.) in a genetically isolated population on Santa Catalina Island. Moreover, each population exhibited reduced performance on the alternative host. This finding is consistent with trade-offs associated with adaptation to these chemically divergent hosts, although we also discuss alternative explanations for this pattern. For oviposition preference, Santa Catalina Island flies were more likely to oviposit on some prickly pear species, but all populations readily laid eggs on saguaro. Experiments with non-natural hosts suggest that factors such as ecological opportunity may play a more important role than host plant chemistry in explaining the lack of natural associations with some hosts.

  16. Host Plant Adaptation in Drosophila mettleri Populations

    PubMed Central

    Castrezana, Sergio; Bono, Jeremy M.

    2012-01-01

    The process of local adaptation creates diversity among allopatric populations, and may eventually lead to speciation. Plant-feeding insect populations that specialize on different host species provide an excellent opportunity to evaluate the causes of ecological specialization and the subsequent consequences for diversity. In this study, we used geographically separated Drosophila mettleri populations that specialize on different host cacti to examine oviposition preference for and larval performance on an array of natural and non-natural hosts (eight total). We found evidence of local adaptation in performance on saguaro cactus (Carnegiea gigantea) for populations that are typically associated with this host, and to chemically divergent prickly pear species (Opuntia spp.) in a genetically isolated population on Santa Catalina Island. Moreover, each population exhibited reduced performance on the alternative host. This finding is consistent with trade-offs associated with adaptation to these chemically divergent hosts, although we also discuss alternative explanations for this pattern. For oviposition preference, Santa Catalina Island flies were more likely to oviposit on some prickly pear species, but all populations readily laid eggs on saguaro. Experiments with non-natural hosts suggest that factors such as ecological opportunity may play a more important role than host plant chemistry in explaining the lack of natural associations with some hosts. PMID:22493678

  17. Adaptive Significance of Quorum Sensing-Dependent Regulation of Rhamnolipids by Integration of Growth Rate in Burkholderia glumae: A Trade-Off between Survival and Efficiency

    PubMed Central

    Nickzad, Arvin; Déziel, Eric

    2016-01-01

    motility, thus promoting the chances of survival, even if the cell density might not be high enough for an otherwise efficient production of rhamnolipids. In conclusion, we propose that the adaptive significance of growth rate-dependent functionality of QS in biosynthesis of costly public goods lies within providing a regulatory mechanism for selecting the optimal trade-off between survival and efficiency. PMID:27540372

  18. Trade-off Mechanisms Shaping the Diversity of Bacteria.

    PubMed

    Ferenci, Thomas

    2016-03-01

    Strain-to-strain variations in bacterial biofilm formation, metabolism, motility, virulence, evolvability, DNA repair and resistance (to phage, antibiotics, or environmental stresses) each contribute to bacterial diversity. Microbiologists should be aware that all of these traits are subject to constraints imposed by trade-offs, so adaptations improving one trait may be at the cost of another. A deeper appreciation of trade-offs is thus crucial for assessing the mechanistic limits on important bacterial characteristics. Studies of the negative correlations between various traits have revealed three molecular mechanisms, namely, trade-offs involving resource allocation, design constraint, and information processing. This review further discusses why these trade-off mechanisms are important in the establishment of models capable of predicting bacterial competition, coexistence, and sources of diversity.

  19. Constraints, Trade-offs and the Currency of Fitness.

    PubMed

    Acerenza, Luis

    2016-03-01

    Understanding evolutionary trajectories remains a difficult task. This is because natural evolutionary processes are simultaneously affected by various types of constraints acting at the different levels of biological organization. Of particular importance are constraints where correlated changes occur in opposite directions, called trade-offs. Here we review and classify the main evolutionary constraints and trade-offs, operating at all levels of trait hierarchy. Special attention is given to life history trade-offs and the conflict between the survival and reproduction components of fitness. Cellular mechanisms underlying fitness trade-offs are described. At the metabolic level, a linear trade-off between growth and flux variability was found, employing bacterial genome-scale metabolic reconstructions. Its analysis indicates that flux variability can be considered as the currency of fitness. This currency is used for fitness transfer between fitness components during adaptations. Finally, a discussion is made regarding the constraints which limit the increase in the amount of fitness currency during evolution, suggesting that occupancy constraints are probably the main restrictions.

  20. Phylogenetic analysis reveals positive correlations between adaptations to diverse hosts in a group of pathogen-like herbivores.

    PubMed

    Peterson, Daniel A; Hardy, Nate B; Morse, Geoffrey E; Stocks, Ian C; Okusu, Akiko; Normark, Benjamin B

    2015-10-01

    A jack of all trades can be master of none-this intuitive idea underlies most theoretical models of host-use evolution in plant-feeding insects, yet empirical support for trade-offs in performance on distinct host plants is weak. Trade-offs may influence the long-term evolution of host use while being difficult to detect in extant populations, but host-use evolution may also be driven by adaptations for generalism. Here we used host-use data from insect collection records to parameterize a phylogenetic model of host-use evolution in armored scale insects, a large family of plant-feeding insects with a simple, pathogen-like life history. We found that a model incorporating positive correlations between evolutionary changes in host performance best fit the observed patterns of diaspidid presence and absence on nearly all focal host taxa, suggesting that adaptations to particular hosts also enhance performance on other hosts. In contrast to the widely invoked trade-off model, we advocate a "toolbox" model of host-use evolution in which armored scale insects accumulate a set of independent genetic tools, each of which is under selection for a single function but may be useful on multiple hosts.

  1. Unintended consequences and trade-offs of fish passage

    USGS Publications Warehouse

    8. McLaughlin, Robert L.; Smyth, Eric R.; Castro-Santos, Theodore; Jones, Michael L.; Koops, Marten A.; Pratt, Thomas C.; Vélez-Espino, Luis-Antonio

    2012-01-01

    We synthesized evidence for unintended consequences and trade-offs associated with the passage of fishes. Provisioning of fish passageways at dams and dam removals are being carried out increasingly as resource managers seek ways to reduce fragmentation of migratory fish populations and restore biodiversity and nature-like ecosystem services in tributaries altered by dams. The benefits of provisioning upstream passage are highlighted widely. Possible unwanted consequences and trade-offs of upstream passage are coming to light, but remain poorly examined and underappreciated. Unintended consequences arise when passage of native and desirable introduced fishes is delayed, undone (fallback), results in patterns of movement and habitat use that reduce Darwinian fitness (e.g. ecological traps), or is highly selective taxonomically and numerically. Trade-offs arise when passage decisions intended to benefit native species interfere with management decisions intended to control the unwanted spread of non-native fishes and aquatic invertebrates, or genes, diseases and contaminants carried by hatchery and wild fishes. These consequences and trade-offs will vary in importance from system to system and can result in large economic and environmental costs. For some river systems, decisions about how to manage fish passage involve substantial risks and could benefit from use of a formal, structured process that allows transparent, objective and, where possible, quantitative evaluation of these risks. Such a process can also facilitate the design of an adaptive framework that provides valuable insights into future decisions.

  2. Gcn4p and the Crabtree effect of yeast: drawing the causal model of the Crabtree effect in Saccharomyces cerevisiae and explaining evolutionary trade-offs of adaptation to galactose through systems biology.

    PubMed

    Martínez, José L; Bordel, Sergio; Hong, KuFk-Ki; Nielsen, Jens

    2014-06-01

    By performing an integrated comparative analysis on the physiology and transcriptome of four different S. cerevisiae strains growing on galactose and glucose, it was inferred that the transcription factors Bas1p, Pho2p, and Gcn4p play a central role in the regulatory events causing the Crabtree effect in S. cerevisiae. The analysis also revealed that a point mutation in the RAS2 observed in a galactose-adapted strain causes a lower Crabtree effect and growth rate on glucose by decreasing the activity of Gcn4p while at the same time is at the origin of higher growth rate on galactose due to a lower activity of the transcriptional repressor Sok2p. The role of Gcn4p on the trade-off effect observed on glucose was confirmed experimentally. This was done by showing that the point mutation in RAS2 does not result in a lower growth rate on glucose if it is introduced in a GCN4-negative background.

  3. Lack of Physiological Depth Patterns in Conspecifics of Endemic Antarctic Brown Algae: A Trade-Off between UV Stress Tolerance and Shade Adaptation?

    PubMed Central

    Gómez, Iván; Huovinen, Pirjo

    2015-01-01

    A striking characteristic of endemic Antarctic brown algae is their broad vertical distribution. This feature is largely determined by the shade adaptation in order to cope with the seasonal variation in light availability. However, during spring-summer months, when light penetrates deep in the water column these organisms have to withstand high levels of solar radiation, including UV. In the present study we examine the light use characteristics in parallel to a potential for UV tolerance (measured as content of phenolic compounds, antioxidant activity and maximum quantum yield of fluorescence) in conspecific populations of four Antarctic brown algae (Ascoseira mirabilis, Desmarestia menziesii, D. anceps and Himantothallus grandifolius) distributed over a depth gradient between 5 and 30 m. The main results indicated that a) photosynthetic efficiency was uniform along the depth gradient in all the studied species, and b) short-term (6 h) exposure to UV radiation revealed a high tolerance measured as chlorophyll fluorescence, phlorotannin content and antioxidant capacity. Multivariate analysis of similarity indicated that light requirements for photosynthesis, soluble phlorotannins and antioxidant capacity are the variables determining the responses along the depth gradient in all the studied species. The suite of physiological responses of algae with a shallower distribution (A. mirabilis and D. menziesii) differed from those with deeper vertical range (D. anceps and H. grandifolius). These patterns are consistent with the underwater light penetration that defines two zones: 0–15 m, with influence of UV radiation (1% of UV-B and UV-A at 9 m and 15 m respectively) and a zone below 15 m marked by PAR incidence (1% up to 30 m). These results support the prediction that algae show a UV stress tolerance capacity along a broad depth range according to their marked shade adaptation. The high contents of phlorotannins and antioxidant potential appear to be strongly

  4. Lack of Physiological Depth Patterns in Conspecifics of Endemic Antarctic Brown Algae: A Trade-Off between UV Stress Tolerance and Shade Adaptation?

    PubMed

    Gómez, Iván; Huovinen, Pirjo

    2015-01-01

    A striking characteristic of endemic Antarctic brown algae is their broad vertical distribution. This feature is largely determined by the shade adaptation in order to cope with the seasonal variation in light availability. However, during spring-summer months, when light penetrates deep in the water column these organisms have to withstand high levels of solar radiation, including UV. In the present study we examine the light use characteristics in parallel to a potential for UV tolerance (measured as content of phenolic compounds, antioxidant activity and maximum quantum yield of fluorescence) in conspecific populations of four Antarctic brown algae (Ascoseira mirabilis, Desmarestia menziesii, D. anceps and Himantothallus grandifolius) distributed over a depth gradient between 5 and 30 m. The main results indicated that a) photosynthetic efficiency was uniform along the depth gradient in all the studied species, and b) short-term (6 h) exposure to UV radiation revealed a high tolerance measured as chlorophyll fluorescence, phlorotannin content and antioxidant capacity. Multivariate analysis of similarity indicated that light requirements for photosynthesis, soluble phlorotannins and antioxidant capacity are the variables determining the responses along the depth gradient in all the studied species. The suite of physiological responses of algae with a shallower distribution (A. mirabilis and D. menziesii) differed from those with deeper vertical range (D. anceps and H. grandifolius). These patterns are consistent with the underwater light penetration that defines two zones: 0-15 m, with influence of UV radiation (1% of UV-B and UV-A at 9 m and 15 m respectively) and a zone below 15 m marked by PAR incidence (1% up to 30 m). These results support the prediction that algae show a UV stress tolerance capacity along a broad depth range according to their marked shade adaptation. The high contents of phlorotannins and antioxidant potential appear to be strongly

  5. Trade-offs in Our Energy Future.

    ERIC Educational Resources Information Center

    Canipe, Stephen L.

    The purpose of this activity is to make students aware that there is no free energy source for the present or the future and that all technologies are potential threats to the environment. The activity consists of a short reading (discussing basic trade-offs, issues, and decisions related to petroleum, coal, and nuclear energy sources) and student…

  6. Does the niche breadth or trade-off hypothesis explain the abundance-occupancy relationship in avian Haemosporidia?

    PubMed

    Drovetski, Sergei V; Aghayan, Sargis A; Mata, Vanessa A; Lopes, Ricardo J; Mode, Nicolle A; Harvey, Johanna A; Voelker, Gary

    2014-07-01

    Two hypotheses have been proposed to explain the abundance-occupancy relationship (AOR) in parasites. The niche breadth hypothesis suggests that host generalists are more abundant and efficient at colonizing different host communities than specialists. The trade-off hypothesis argues that host specialists achieve high density across their hosts' ranges, whereas generalists incur the high cost of adaptation to diverse immuno-defence systems. We tested these hypotheses using 386 haemosporidian cytochrome-b lineages (1894 sequences) recovered from 2318 birds of 103 species sampled in NW Africa, NW Iberia, W Greater Caucasus and Transcaucasia. The number of regions occupied by lineages was associated with their frequency suggesting the presence of AOR in avian Haemosporidia. However, neither hypothesis provided a better explanation for the AOR. Although the host generalist Plasmodium SGS1 was over three times more abundant than other widespread lineages, both host specialists and generalists were successful in colonizing all study regions and achieved high overall prevalence.

  7. REMBASS Commandability. Trade Off Analysis (TOA)/Trade Off Determination (TOD)

    DTIC Science & Technology

    1977-12-15

    vantage to crystal control operation is the very low power drain associated with this concept. Proposed duty cycles, and the use of improved front end ...SUMMARY This trade-off analysis (TOA) and trade-off deter- mination (TOD) was used to analyze and rank various system- level and contract end item...The sensor uses the invisible frequency spectrum contiguous to the red end of the visible spectrum for detecting targets. The sensor processes the

  8. Temporal trade-offs in psychophysics.

    PubMed

    Barack, David L; Gold, Joshua I

    2016-04-01

    Psychophysical techniques typically assume straightforward relationships between manipulations of real-world events, their effects on the brain, and behavioral reports of those effects. However, these relationships can be influenced by many complex, strategic factors that contribute to task performance. Here we discuss several of these factors that share two key features. First, they involve subjects making flexible use of time to process information. Second, this flexibility can reflect the rational regulation of information-processing trade-offs that can play prominent roles in particular temporal epochs: sensitivity to stability versus change for past information, speed versus accuracy for current information, and exploitation versus exploration for future goals. Understanding how subjects manage these trade-offs can be used to help design and interpret psychophysical studies.

  9. A trade-off between quantity and quality of offspring in haematophagous ectoparasites: the effect of the level of specialization.

    PubMed

    Khokhlova, Irina S; Pilosof, Shai; Fielden, Laura J; Degen, A Allan; Krasnov, Boris R

    2014-03-01

    Theory predicts an adaptive trade-off between quantity and quality of offspring if mothers can reliably predict the offspring environment. We studied egg production and quality of offspring in two flea species (host-specialist Parapulex chephrenis and host-generalist Xenopsylla ramesis) exploiting eight rodent species. We evaluated quality of new imagoes via their developmental time, size (length of a femur as a proxy) and resistance to starvation without a blood meal. We predicted that the offspring quality would increase with (i) a decrease in the number of eggs produced by mothers and (ii) an increase in phylogenetic distance between maternal host and principal host of a flea. We also predicted that negative relationships between offspring quality and either maternal egg production effort or phylogenetic distance between maternal host and the principal host or both would be manifested stronger in host-opportunistic than in host-specific fleas. The highest number of eggs produced per female flea was accompanied by the longest duration of development and the smallest offspring in X. ramesis, while P. chephrenis that hatched from larger clutches survived for less time under starvation. Although there was no significant effect of host species on any dependent variable, association between offspring quality and phylogenetic distance of the maternal host from the principal host of a flea was found in X. ramesis (but not P. chephrenis) with new imagoes being larger if their maternal hosts were phylogenetically distant from the principal host. Our results demonstrated stronger trade-off between quantity and quality of offspring in a generalist than in a specialist flea, supporting the association between life-history plasticity and generalist feeding strategy.

  10. Design trade-offs for homing missiles

    NASA Astrophysics Data System (ADS)

    Spencer, Allen; Moore, William

    1992-05-01

    Major design considerations, trade-offs and technology issues for future hypervelocity, anti-missile interceptors are presented in an overview format. Two classes of interceptors are considered: a low altitude interceptor using an active radar seeker for defense against tactical ballistic missiles (TBMs) and a higher altitude interceptor using a passive infra-red seeker for defense against ICBMs. Considerations are presented in the areas of mission requirements, seeker selection, aerodynamic and aerothermal environments, control systems, and guidance performance.

  11. Cancer: A disease at the crossroads of trade-offs.

    PubMed

    Jacqueline, Camille; Biro, Peter A; Beckmann, Christa; Moller, Anders Pape; Renaud, François; Sorci, Gabriele; Tasiemski, Aurélie; Ujvari, Beata; Thomas, Frédéric

    2017-03-01

    Central to evolutionary theory is the idea that living organisms face phenotypic and/or genetic trade-offs when allocating resources to competing life-history demands, such as growth, survival, and reproduction. These trade-offs are increasingly considered to be crucial to further our understanding of cancer. First, evidences suggest that neoplastic cells, as any living entities subject to natural selection, are governed by trade-offs such as between survival and proliferation. Second, selection might also have shaped trade-offs at the organismal level, especially regarding protective mechanisms against cancer. Cancer can also emerge as a consequence of additional trade-offs in organisms (e.g., eco-immunological trade-offs). Here, we review the wide range of trade-offs that occur at different scales and their relevance for understanding cancer dynamics. We also discuss how acknowledging these phenomena, in light of human evolutionary history, may suggest new guidelines for preventive and therapeutic strategies.

  12. Fitness trade-offs in pest management and intercropping with colour: an evolutionary framework and potential application

    PubMed Central

    Farkas, Timothy E

    2015-01-01

    An important modern goal of plant science research is to develop tools for agriculturalists effective at curbing yield losses to insect herbivores, but resistance evolution continuously threatens the efficacy of pest management strategies. The high-dose/refuge strategy has been employed with some success to curb pest adaptation, and has been shown to be most effective when fitness costs (fitness trade-offs) of resistance are high. Here, I use eco-evolutionary reasoning to demonstrate the general importance of fitness trade-offs for pest control, showing that strong fitness trade-offs mitigate the threat of pest adaptation, even if adaptation were to occur. I argue that novel pest management strategies evoking strong fitness trade-offs are the most likely to persist in the face of unbridled pest adaptation, and offer the manipulation of crop colours as a worked example of one potentially effective strategy against insect herbivores. PMID:26495038

  13. Fitness trade-offs in pest management and intercropping with colour: an evolutionary framework and potential application.

    PubMed

    Farkas, Timothy E

    2015-10-01

    An important modern goal of plant science research is to develop tools for agriculturalists effective at curbing yield losses to insect herbivores, but resistance evolution continuously threatens the efficacy of pest management strategies. The high-dose/refuge strategy has been employed with some success to curb pest adaptation, and has been shown to be most effective when fitness costs (fitness trade-offs) of resistance are high. Here, I use eco-evolutionary reasoning to demonstrate the general importance of fitness trade-offs for pest control, showing that strong fitness trade-offs mitigate the threat of pest adaptation, even if adaptation were to occur. I argue that novel pest management strategies evoking strong fitness trade-offs are the most likely to persist in the face of unbridled pest adaptation, and offer the manipulation of crop colours as a worked example of one potentially effective strategy against insect herbivores.

  14. The virulence–transmission trade-off in vector-borne plant viruses: a review of (non-)existing studies

    PubMed Central

    Froissart, R.; Doumayrou, J.; Vuillaume, F.; Alizon, S.; Michalakis, Y.

    2010-01-01

    The adaptive hypothesis invoked to explain why parasites harm their hosts is known as the trade-off hypothesis, which states that increased parasite transmission comes at the cost of shorter infection duration. This correlation arises because both transmission and disease-induced mortality (i.e. virulence) are increasing functions of parasite within-host density. There is, however, a glaring lack of empirical data to support this hypothesis. Here, we review empirical investigations reporting to what extent within-host viral accumulation determines the transmission rate and the virulence of vector-borne plant viruses. Studies suggest that the correlation between within-plant viral accumulation and transmission rate of natural isolates is positive. Unfortunately, results on the correlation between viral accumulation and virulence are very scarce. We found only very few appropriate studies testing such a correlation, themselves limited by the fact that they use symptoms as a proxy for virulence and are based on very few viral genotypes. Overall, the available evidence does not allow us to confirm or refute the existence of a transmission–virulence trade-off for vector-borne plant viruses. We discuss the type of data that should be collected and how theoretical models can help us refine testable predictions of virulence evolution. PMID:20478886

  15. Evolution of dispersal under a fecundity-dispersal trade-off.

    PubMed

    Weigang, Helene C; Kisdi, Éva

    2015-04-21

    Resources invested in dispersal structures as well as time and energy spent during transfer may often decrease fecundity. Here we analyse an extended version of the Hamilton-May model of dispersal evolution, where we include a fecundity-dispersal trade-off and also mortality between competition and reproduction. With adaptive dynamics and critical function analysis we investigate the evolution of dispersal strategies and ask whether adaptive diversification is possible. We exclude evolutionary branching for concave trade-offs and show that for convex trade-offs diversification is promoted in a narrow parameter range. We provide theoretical evidence that dispersal strategies can monotonically decrease with increasing survival during dispersal. Moreover, we illustrate the existence of two alternative attracting dispersal strategies. The model exhibits fold bifurcation points where slight changes in survival can lead to evolutionary catastrophes.

  16. Guidance Trade-off for Aerocapture Missions

    NASA Astrophysics Data System (ADS)

    Vernis, P.; Gelly, G.; Ferreira, E.; da Costa, R.; Ortega, G.

    In the very late 90's, EADS-ST began home funded studies on aerocapture problems. The objectives of these studies were at that time to prepare a possible cooperation within the NASA/Cnes MSR-Orbiter program by investigating this new orbital insertion technique studying different algorithmic solutions from a guidance point of view. According to these preliminary studies, EADS-ST was retained in 2002 by ESA to study insertion techniques such as aerocapture, aero-gravity assist or aerobraking techniques within the frame of Technological Research Program able to bring solutions to Aurora program. In the frame of the ATPE (Aeroassist Technologies for Planetary Exploration) TRP program, EADS-ST, led by Astrium-Gmbh (now part of EADS-ST), developed and implemented an efficient and simple guidance scheme able to cope with mission requirements for aerocapture on Mars, Venus or the Earth: the Feedback Trajectory Control, or FTC. The development of this guidance scheme was made according to a preliminary trade-off analysis using different guidance schemes. Among those ones was an original predictor-corrector guidance scheme, already analyzed within the frame of the MSR-O mission. But, the FTC algoritm was prefered because of its good results and high simplicity. This paper presents an upgrade of the original Apoapsis Predictor, or AP, with the improvement of its robustness woth respect to off-nomonal flight conditions and its process simplification. A new trade-off analysis is then detailed on a Mars Sample return mission.

  17. Trade-offs in an ant-plant-fungus mutualism.

    PubMed

    Orivel, Jérôme; Malé, Pierre-Jean; Lauth, Jérémie; Roux, Olivier; Petitclerc, Frédéric; Dejean, Alain; Leroy, Céline

    2017-03-15

    Species engaged in multiple, simultaneous mutualisms are subject to trade-offs in their mutualistic investment if the traits involved in each interaction are overlapping, which can lead to conflicts and affect the longevity of these associations. We investigate this issue via a tripartite mutualism involving an ant plant, two competing ant species and a fungus the ants cultivate to build galleries under the stems of their host plant to capture insect prey. The use of the galleries represents an innovative prey capture strategy compared with the more typical strategy of foraging on leaves. However, because of a limited worker force in their colonies, the prey capture behaviour of the ants results in a trade-off between plant protection (i.e. the ants patrol the foliage and attack intruders including herbivores) and ambushing prey in the galleries, which has a cascading effect on the fitness of all of the partners. The quantification of partners' traits and effects showed that the two ant species differed in their mutualistic investment. Less investment in the galleries (i.e. in fungal cultivation) translated into more benefits for the plant in terms of less herbivory and higher growth rates and vice versa. However, the greater vegetative growth of the plants did not produce a positive fitness effect for the better mutualistic ant species in terms of colony size and production of sexuals nor was the mutualist compensated by the wider dispersal of its queens. As a consequence, although the better ant mutualist is the one that provides more benefits to its host plant, its lower host-plant exploitation does not give this ant species a competitive advantage. The local coexistence of the ant species is thus fleeting and should eventually lead to the exclusion of the less competitive species.

  18. Oxidative Stress: A Master Regulator of Plant Trade-Offs?

    PubMed

    Morales, Melanie; Munné-Bosch, Sergi

    2016-12-01

    Trade-offs between growth, reproduction, and defence have been documented. Oxidative stress is one of the physiological mechanisms that underlie trade-offs at the cellular and organ levels. The diversity of plant life forms and the complexity of scaling up limit our knowledge of oxidative stress as a universal mediator of life-history trade-offs at the organism level. Joint efforts by plant physiologists and ecologists will undoubtedly provide novel insights into this topic in the near future.

  19. Global agriculture and carbon trade-offs

    PubMed Central

    Johnson, Justin Andrew; Runge, Carlisle Ford; Senauer, Benjamin; Foley, Jonathan; Polasky, Stephen

    2014-01-01

    Feeding a growing and increasingly affluent world will require expanded agricultural production, which may require converting grasslands and forests into cropland. Such conversions can reduce carbon storage, habitat provision, and other ecosystem services, presenting difficult societal trade-offs. In this paper, we use spatially explicit data on agricultural productivity and carbon storage in a global analysis to find where agricultural extensification should occur to meet growing demand while minimizing carbon emissions from land use change. Selective extensification saves ∼6 billion metric tons of carbon compared with a business-as-usual approach, with a value of approximately $1 trillion (2012 US dollars) using recent estimates of the social cost of carbon. This type of spatially explicit geospatial analysis can be expanded to include other ecosystem services and other industries to analyze how to minimize conflicts between economic development and environmental sustainability. PMID:25114254

  20. Taxonomic, phylogenetic, and environmental trade-offs between leaf productivity and persistence.

    PubMed

    He, Jin-Sheng; Wang, Xiangping; Flynn, Dan F B; Wang, Liang; Schmid, Bernhard; Fang, Jingyun

    2009-10-01

    Assessing the influence of climate, soil fertility, and species identity on leaf trait relationships is crucial for understanding the adaptations of plants to their environment and for interpreting leaf trait relationships across spatial scales. In a comparative field study of 171 plant species in 174 grassland sites across China, we examined the trade-offs, defined as negative covariance between two traits, between leaf persistence (leaf mass per area, LMA) and leaf productivity (mass-based photosynthetic rate, Amass, N and P content, and photosynthetic N use efficiency, PNUE). We asked to which extent these trade-offs were influenced by: (1) variation among sites within species, decomposed into variation due to climatic and soil variables; (2) variation among species within sites, decomposed into variation among taxonomic, functional, or phylogenetic groups; and (3) the joint contribution of variation among species and sites. We used mixed-model analysis of covariance to partition bivariate relationships between leaf traits into trade-off components. We found significant mass-based persistence-productivity trade-offs of LMA-Amass, LMA-N, LMA-P, and LMA-PNUE consistent with previous broadscale findings. Overall, (1) variation among sites within species explained 14-23%, (2) variation among species within sites explained 20-34%, and (3) the two together explained 42-63% of the total covariance between leaf traits. Interspecific trade-offs of LMA-Amass, LMA-N, and LMA-P were stronger than inter-site ones. A relatively low amount of covariance was explained by climatic and soil variables. However, we found the trade-offs were stronger for LMA-N and LMA-P at higher precipitation and for LMA-PNUE at greater soil fertility, if displayed by major axis regression, which combined both intra- and interspecific variation. Residual trade-offs within species and sites were weak, suggesting that intraspecific, intra-site variation in physiology was less important than variation

  1. Life history trade-offs and relaxed selection can decrease bacterial virulence in environmental reservoirs.

    PubMed

    Mikonranta, Lauri; Friman, Ville-Petri; Laakso, Jouni

    2012-01-01

    Pathogen virulence is usually thought to evolve in reciprocal selection with the host. While this might be true for obligate pathogens, the life histories of opportunistic pathogens typically alternate between within-host and outside-host environments during the infection-transmission cycle. As a result, opportunistic pathogens are likely to experience conflicting selection pressures across different environments, and this could affect their virulence through life-history trait correlations. We studied these correlations experimentally by exposing an opportunistic bacterial pathogen Serratia marcescens to its natural protist predator Tetrahymena thermophila for 13 weeks, after which we measured changes in bacterial traits related to both anti-predator defence and virulence. We found that anti-predator adaptation (producing predator-resistant biofilm) caused a correlative attenuation in virulence. Even though the direct mechanism was not found, reduction in virulence was most clearly connected to a predator-driven loss of a red bacterial pigment, prodigiosin. Moreover, life-history trait evolution was more divergent among replicate populations in the absence of predation, leading also to lowered virulence in some of the 'predator absent' selection lines. Together these findings suggest that the virulence of non-obligatory, opportunistic bacterial pathogens can decrease in environmental reservoirs through life history trade-offs, or random accumulation of mutations that impair virulence traits under relaxed selection.

  2. Conceptualising and managing trade-offs in sustainability assessment

    SciTech Connect

    Morrison-Saunders, Angus; Pope, Jenny

    2013-01-15

    One of the defining characteristics of sustainability assessment as a form of impact assessment is that it provides a forum for the explicit consideration of the trade-offs that are inherent in complex decision-making processes. Few sustainability assessments have achieved this goal though, and none has considered trade-offs in a holistic fashion throughout the process. Recent contributions such as the Gibson trade-off rules have significantly progressed thinking in this area by suggesting appropriate acceptability criteria for evaluating substantive trade-offs arising from proposed development, as well as process rules for how evaluations of acceptability should occur. However, there has been negligible uptake of these rules in practice. Overall, we argue that there is inadequate consideration of trade-offs, both process and substantive, throughout the sustainability assessment process, and insufficient considerations of how process decisions and compromises influence substantive outcomes. This paper presents a framework for understanding and managing both process and substantive trade-offs within each step of a typical sustainability assessment process. The framework draws together previously published literature and offers case studies that illustrate aspects of the practical application of the framework. The framing and design of sustainability assessment are vitally important, as process compromises or trade-offs can have substantive consequences in terms of sustainability outcomes delivered, with the choice of alternatives considered being a particularly significant determinant of substantive outcomes. The demarcation of acceptable from unacceptable impacts is a key aspect of managing trade-offs. Offsets can be considered as a form of trade-off within a category of sustainability that are utilised to enhance preferred alternatives once conditions of impact acceptability have been met. In this way they may enable net gains to be delivered; another imperative

  3. Reproduction-Immunity Trade-Offs in Insects.

    PubMed

    Schwenke, Robin A; Lazzaro, Brian P; Wolfner, Mariana F

    2016-01-01

    Immune defense and reproduction are physiologically and energetically demanding processes and have been observed to trade off in a diversity of female insects. Increased reproductive effort results in reduced immunity, and reciprocally, infection and activation of the immune system reduce reproductive output. This trade-off can manifest at the physiological level (within an individual) and at the evolutionary level (genetic distinction among individuals in a population). The resource allocation model posits that the trade-off arises because of competition for one or more limiting resources, and we hypothesize that pleiotropic signaling mechanisms regulate allocation of that resource between reproductive and immune processes. We examine the role of juvenile hormone, 20-hydroxyecdysone, and insulin/insulin-like growth factor-like signaling in regulating both oogenesis and immune system activity, and propose a signaling network that may mechanistically regulate the trade-off. Finally, we discuss implications of the trade-off in an ecological and evolutionary context.

  4. Reproduction–Immunity Trade-Offs in Insects

    PubMed Central

    Schwenke, Robin A.; Lazzaro, Brian P.; Wolfner, Mariana F.

    2017-01-01

    Immune defense and reproduction are physiologically and energetically demanding processes and have been observed to trade off in a diversity of female insects. Increased reproductive effort results in reduced immunity, and reciprocally, infection and activation of the immune system reduce reproductive output. This trade-off can manifest at the physiological level (within an individual) and at the evolutionary level (genetic distinction among individuals in a population). The resource allocation model posits that the trade-off arises because of competition for one or more limiting resources, and we hypothesize that pleiotropic signaling mechanisms regulate allocation of that resource between reproductive and immune processes. We examine the role of juvenile hormone, 20-hydroxyecdysone, and insulin/insulin-like growth factor-like signaling in regulating both oogenesis and immune system activity, and propose a signaling network that may mechanistically regulate the trade-off. Finally, we discuss implications of the trade-off in an ecological and evolutionary context. PMID:26667271

  5. Multihost experimental evolution of a plant RNA virus reveals local adaptation and host-specific mutations.

    PubMed

    Bedhomme, Stéphanie; Lafforgue, Guillaume; Elena, Santiago F

    2012-05-01

    For multihost pathogens, adaptation to multiple hosts has important implications for both applied and basic research. At the applied level, it is one of the main factors determining the probability and the severity of emerging disease outbreaks. At the basic level, it is thought to be a key mechanism for the maintenance of genetic diversity both in host and pathogen species. Using Tobacco etch potyvirus (TEV) and four natural hosts, we have designed an evolution experiment whose strength and novelty are the use of complex multicellular host organism as hosts and a high level of replication of different evolutionary histories and lineages. A pattern of local adaptation, characterized by a higher infectivity and virulence on host(s) encountered during the experimental evolution was found. Local adaptation only had a cost in terms of performance on other hosts in some cases. We could not verify the existence of a cost for generalists, as expected to arise from antagonistic pleiotropy and other genetic mechanisms generating a fitness trade-off between hosts. This observation confirms that this classical theoretical prediction lacks empirical support. We discuss the reasons for this discrepancy between theory and experiment in the light of our results. The analysis of full genome consensus sequences of the evolved lineages established that all mutations shared between lineages were host specific. A low degree of parallel evolution was observed, possibly reflecting the various adaptive pathways available for TEV in each host. Altogether, these results reveal a strong adaptive potential of TEV to new hosts without severe evolutionary constraints.

  6. Life history trade-offs imposed by dragline use in two money spiders.

    PubMed

    Bonte, Dries; Verduyn, Lieselot; Braeckman, Bart P

    2016-01-01

    Trade-offs among life history traits are central to understanding the limits of adaptations to stress. In animals, virtually all decisions taken during life are expected to have downstream consequences. To what degree rare, but energy-demanding, decisions carry over to individual performance is rarely studied in arthropods. We used spiders as a model system to test how single investments in silk use - for dispersal or predator escape - affect individual performance. Silk produced for safe lines and as threads for ballooning is of the strongest kind and is energetically costly, especially when resources are limited. We induced dragline spinning in two species of money spider at similar quantities to that under natural conditions and tested trade-offs with lifespan and egg sac production under unlimited prey availability and a dietary restriction treatment. We demonstrate strong trade-offs between dragline spinning and survival and fecundity. Survival trade-offs were additive to those imposed by the dietary treatment, but a reduction in eggs produced after silk use was only prevalent under conditions where food was restricted during the spider's life. Because draglines are not recycled after their use for dispersal or predator escape, their spinning incurs substantial fitness costs in dispersal, especially in environments with prey limitation. Rare but energetically costly decisions related to dispersal or predator escape may thus carry over to adult performance and explain phenotypic heterogeneity in natural populations.

  7. Sex Allocation in California Oaks: Trade-Offs or Resource Tracking?

    PubMed Central

    Knops, Johannes M. H.; Koenig, Walter D.

    2012-01-01

    Trade-offs in sex resource allocation are commonly inferred from a negative correlation between male and female reproduction. We found that for three California oak species, aboveground annual net productivity (ANP) differences among individuals were primarily correlated with water availability and soil fertility. Reproductive biomass increased with ANP, but the relative allocation to reproduction was constant, indicating that reproduction tracked productivity, which in turn tracked site quality. Although there was a negative correlation between male and female reproduction, this was not the result of a resource investment trade-off, but rather a byproduct of the positive correlation between female reproductive biomass and ANP combined with the greater overall resource allocation to female, compared to male, function. Thus, we reject the hypothesis of a trade-off between these key life-history components within individuals of these species. For long-lived individuals, a plastic resource tracking response to environmental fluctuations may be more adaptive than directly linking life-history traits through trade-offs. PMID:22952692

  8. Parasitism and Physiological Trade-Offs in Stressed Capybaras

    PubMed Central

    Eberhardt, Ayelen T.; Costa, Sebastián A.; Marini, M. Rocío; Racca, Andrea; Baldi, Cecilia J.; Robles, M. Rosario; Moreno, Pablo G.; Beldomenico, Pablo M.

    2013-01-01

    Parasites play a key role in regulating wildlife population dynamics, but their impact on the host appears to be context-dependent. Evidence indicates that a synergistic interaction between stress, host condition and parasites is implicated in this phenomenon, but more studies are needed to better understand this context-dependency. With the goal to assess the net effect of two types of chronic stress on various host-parasite interactions, we conducted an experiment in capybaras to evaluate the impact of food restriction and physical restraint on the infection intensity of specific gastrointestinal nematodes and coccidia, and how these stressors affected the growth, body condition, and some immuno-physiological parameters. Our hypothesis was that both forms of stress would result in an alteration in the host-parasite interactions, with deteriorated condition and reduced immunological investment leading to high parasite burdens and vice versa. Stressed capybaras had significantly higher coccidia infection intensities; but among individuals that were smaller, those stressed consistently showed lower helminth burdens than controls. Both stress treatments had a marked negative impact on growth and body condition, but concomitantly they had a significant positive effect on some components of the immune system. Our results suggest, on the one hand, that during prolonged periods of stress capybaras preventatively invest in some components of their immunity, such as innate humoural defenses and cells that combat helminths, which could be considered a stress-dependent prophylaxis. On the other hand, stress was found to cause greater infection intensities of protozoans but lower burdens of nematodes, indicating that the relationship between stress, physiological trade-offs and infection depends on the type of parasite in question. Moreover, both findings might be related in a causal way, as one of the immunological parameters enhanced in stressed capybaras is associated with

  9. Trade-offs across space, time, and ecosystem services

    USGS Publications Warehouse

    Rodriguez, J.P.; Beard, T.D.; Bennett, E.M.; Cumming, Graeme S.; Cork, S.J.; Agard, J.; Dobson, A.P.; Peterson, G.D.

    2006-01-01

    Ecosystem service (ES) trade-offs arise from management choices made by humans, which can change the type, magnitude, and relative mix of services provided by ecosystems. Trade-offs occur when the provision of one ES is reduced as a consequence of increased use of another ES. In some cases, a trade-off may be an explicit choice; but in others, trade-offs arise without premeditation or even awareness that they are taking place. Trade-offs in ES can be classified along three axes: spatial scale, temporal scale, and reversibility. Spatial scale refers to whether the effects of the trade-off are felt locally or at a distant location. Temporal scale refers to whether the effects take place relatively rapidly or slowly. Reversibility expresses the likelihood that the perturbed ES may return to its original state if the perturbation ceases. Across all four Millennium Ecosystem Assessment scenarios and selected case study examples, trade-off decisions show a preference for provisioning, regulating, or cultural services (in that order). Supporting services are more likely to be "taken for granted." Cultural ES are almost entirely unquantified in scenario modeling; therefore, the calculated model results do not fully capture losses of these services that occur in the scenarios. The quantitative scenario models primarily capture the services that are perceived by society as more important - provisioning and regulating ecosystem services - and thus do not fully capture trade-offs of cultural and supporting services. Successful management policies will be those that incorporate lessons learned from prior decisions into future management actions. Managers should complement their actions with monitoring programs that, in addition to monitoring the short-term provisions of services, also monitor the long-term evolution of slowly changing variables. Policies can then be developed to take into account ES trade-offs at multiple spatial and temporal scales. Successful strategies will

  10. Emotion-induced trade-offs in spatiotemporal vision.

    PubMed

    Bocanegra, Bruno R; Zeelenberg, René

    2011-05-01

    It is generally assumed that emotion facilitates human vision in order to promote adaptive responses to a potential threat in the environment. Surprisingly, we recently found that emotion in some cases impairs the perception of elementary visual features (Bocanegra & Zeelenberg, 2009b). Here, we demonstrate that emotion improves fast temporal vision at the expense of fine-grained spatial vision. We tested participants' threshold resolution with Landolt circles containing a small spatial or brief temporal discontinuity. The prior presentation of a fearful face cue, compared with a neutral face cue, impaired spatial resolution but improved temporal resolution. In addition, we show that these benefits and deficits were triggered selectively by the global configural properties of the faces, which were transmitted only through low spatial frequencies. Critically, the common locus of these opposite effects suggests a trade-off between magno- and parvocellular-type visual channels, which contradicts the common assumption that emotion invariably improves vision. We show that, rather than being a general "boost" for all visual features, affective neural circuits sacrifice the slower processing of small details for a coarser but faster visual signal.

  11. Acknowledging conservation trade-offs and embracing complexity.

    PubMed

    Hirsch, Paul D; Adams, William M; Brosius, J Peter; Zia, Asim; Bariola, Nino; Dammert, Juan Luis

    2011-04-01

    There is a growing recognition that conservation often entails trade-offs. A focus on trade-offs can open the way to more complete consideration of the variety of positive and negative effects associated with conservation initiatives. In analyzing and working through conservation trade-offs, however, it is important to embrace the complexities inherent in the social context of conservation. In particular, it is important to recognize that the consequences of conservation activities are experienced, perceived, and understood differently from different perspectives, and that these perspectives are embedded in social systems and preexisting power relations. We illustrate the role of trade-offs in conservation and the complexities involved in understanding them with recent debates surrounding REDD (Reducing Emissions from Deforestation and Degradation), a global conservation policy designed to create incentives to reduce tropical deforestation. Often portrayed in terms of the multiple benefits it may provide: poverty alleviation, biodiversity conservation, and climate-change mitigation; REDD may involve substantial trade-offs. The gains of REDD may be associated with a reduction in incentives for industrialized countries to decrease carbon emissions; relocation of deforestation to places unaffected by REDD; increased inequality in places where people who make their livelihood from forests have insecure land tenure; loss of biological and cultural diversity that does not directly align with REDD measurement schemes; and erosion of community-based means of protecting forests. We believe it is important to acknowledge the potential trade-offs involved in conservation initiatives such as REDD and to examine these trade-offs in an open and integrative way that includes a variety of tools, methods, and points of view.

  12. A Resource Allocation Trade-Off between Virulence and Proliferation Drives Metabolic Versatility in the Plant Pathogen Ralstonia solanacearum

    PubMed Central

    Marmiesse, Lucas; Gouzy, Jérôme

    2016-01-01

    Bacterial pathogenicity relies on a proficient metabolism and there is increasing evidence that metabolic adaptation to exploit host resources is a key property of infectious organisms. In many cases, colonization by the pathogen also implies an intensive multiplication and the necessity to produce a large array of virulence factors, which may represent a significant cost for the pathogen. We describe here the existence of a resource allocation trade-off mechanism in the plant pathogen R. solanacearum. We generated a genome-scale reconstruction of the metabolic network of R. solanacearum, together with a macromolecule network module accounting for the production and secretion of hundreds of virulence determinants. By using a combination of constraint-based modeling and metabolic flux analyses, we quantified the metabolic cost for production of exopolysaccharides, which are critical for disease symptom production, and other virulence factors. We demonstrated that this trade-off between virulence factor production and bacterial proliferation is controlled by the quorum-sensing-dependent regulatory protein PhcA. A phcA mutant is avirulent but has a better growth rate than the wild-type strain. Moreover, a phcA mutant has an expanded metabolic versatility, being able to metabolize 17 substrates more than the wild-type. Model predictions indicate that metabolic pathways are optimally oriented towards proliferation in a phcA mutant and we show that this enhanced metabolic versatility in phcA mutants is to a large extent a consequence of not paying the cost for virulence. This analysis allowed identifying candidate metabolic substrates having a substantial impact on bacterial growth during infection. Interestingly, the substrates supporting well both production of virulence factors and growth are those found in higher amount within the plant host. These findings also provide an explanatory basis to the well-known emergence of avirulent variants in R. solanacearum

  13. Are there genetic trade-offs between immune and reproductive investments in Tribolium castaneum?

    PubMed

    Hangartner, Sandra; Sbilordo, Sonja H; Michalczyk, Łukasz; Gage, Matthew J G; Martin, Oliver Y

    2013-10-01

    Parasites impose strong selection on hosts to defend themselves, which is expected to result in trade-offs with other fitness traits such as reproduction. Here we test for genetic trade-offs between reproductive traits and immunity using Tribolium castaneum lines that were subject to experimental evolution. The lines have been exposed to contrasting sexual selection intensities via different sex ratios (female-biased, equal and male-biased). After 56 generations, the lines have significantly diverged and those experiencing high sexual selection have evolved males who are superior competitors for reproductive success, and females who are more resistant to multiple mating. All selected lines were assessed for both an immune measurement (phenoloxidase (PO) activity) and host resistance to the microsporidian Nosema whitei after two generations of relaxed selection. In contrast to our expectations we did not find any evidence for a genetic trade-off between investment in reproduction and immunity. Both PO and Nosema resistance did not differ between lines, despite their divergences in reproductive investment due to variation in sexual selection and conflict. Nevertheless, overall we found that females had higher PO activities and in the Nosema free control treatment survived longer than males, suggesting that females generally invest more in PO and survival under control conditions than males. This result fits the Bateman's principle, which states that females gain fitness through increased immunity and longevity, while males gain fitness through increased mating success.

  14. Quantum trade-off coding for bosonic communication

    NASA Astrophysics Data System (ADS)

    Wilde, Mark M.; Hayden, Patrick; Guha, Saikat

    2012-12-01

    The trade-off capacity region of a quantum channel characterizes the optimal net rates at which a sender can communicate classical, quantum, and entangled bits to a receiver by exploiting many independent uses of the channel, along with the help of the same resources. Similarly, one can consider a trade-off capacity region when the noiseless resources are public, private, and secret-key bits. We identified [see Wilde, Hayden, and Guha, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.108.140501 108, 140501 (2012)] these trade-off rate regions for the pure-loss bosonic channel and proved that they are optimal provided that a long-standing minimum-output entropy conjecture is true. Additionally, we showed that the performance gains of a trade-off coding strategy when compared to a time-sharing strategy can be quite significant. In this paper, we provide detailed derivations of the results announced there, and we extend the application of these ideas to thermal-noise and amplifying bosonic channels. We also derive a “rule of thumb” for trade-off coding, which determines how to allocate photons in a coding strategy if a large mean photon number is available at the channel input. Our results on the amplifying bosonic channel also apply to the “Unruh channel” considered in the context of relativistic quantum information theory.

  15. A Trade-Off Study Revealing Nested Timescales of Constraint

    PubMed Central

    Wijnants, M. L.; Cox, R. F. A.; Hasselman, F.; Bosman, A. M. T.; Van Orden, G.

    2012-01-01

    This study investigates human performance in a cyclic Fitts task at three different scales of observation, either in the presence (difficult condition) or in the absence (easy condition) of a speed–accuracy trade-off. At the fastest scale, the harmonicity of the back and forth movements, which reflects the dissipation of mechanical energy, was measured within the timeframe of single trials. At an intermediate scale, speed and accuracy measures were determined over a trial. The slowest scale pertains to the temporal structure of movement variability, which evolves over multiple trials. In the difficult condition, reliable correlations across each of the measures corroborated a coupling of nested scales of performance. Participants who predominantly emphasized the speed-side of the trade-off (despite the instruction to be both fast and accurate) produced more harmonic movements and clearer 1/f scaling in the produced movement time series, but were less accurate and produced more random variability in the produced movement amplitudes (vice versa for more accurate participants). This implied that speed–accuracy trade-off was accompanied by a trade-off between temporal and spatial streams of 1/f scaling, as confirmed by entropy measures. In the easy condition, however, no trade-offs nor couplings among scales of performance were observed. Together, these results suggest that 1/f scaling is more than just a byproduct of cognition. These findings rather support the claim that interaction-dominant dynamics constitute a coordinative basis for goal-directed behavior. PMID:22654760

  16. Generalist–specialist trade-off during thermal acclimation

    PubMed Central

    Seebacher, Frank; Ducret, Varlérie; Little, Alexander G.; Adriaenssens, Bart

    2015-01-01

    The shape of performance curves and their plasticity define how individuals and populations respond to environmental variability. In theory, maximum performance decreases with an increase in performance breadth. However, reversible acclimation may counteract this generalist–specialist trade-off, because performance optima track environmental conditions so that there is no benefit of generalist phenotypes. We tested this hypothesis by acclimating individual mosquitofish (Gambusia holbrooki) to cool and warm temperatures consecutively and measuring performance curves of swimming performance after each acclimation treatment. Individuals from the same population differed significantly in performance maxima, performance breadth and the capacity for acclimation. As predicted, acclimation resulted in a shift of the temperature at which maximal performance occurred. Within acclimation treatments, there was a significant generalist–specialist trade-off in responses to acute temperature change. Surprisingly, however, there was also a trade-off across acclimation treatments, and animals with greater capacity for cold acclimation had lower performance maxima under warm conditions. Hence, cold acclimation may be viewed as a generalist strategy that extends performance breadth at the colder seasons, but comes at the cost of reduced performance at the warmer time of year. Acclimation therefore does not counteract a generalist–specialist trade-off and, at least in mosquitofish, the trade-off seems to be a system property that persists despite phenotypic plasticity. PMID:26064581

  17. Adaptation to a novel host by a seed beetle (Coleoptera: Chrysomelidae: Bruchinae): effect of source population.

    PubMed

    Messina, Frank J; Durham, Susan L

    2013-08-01

    Geographic populations of a widespread species can differ in their ability to adapt to a novel environment because they possess different amounts of the requisite genetic variation. We compared responses to the same novel host in ecologically and genetically divergent populations of the seed beetle Callosobruchus maculatus (F.). Populations from Africa and Asia had been derived from and maintained on different legume hosts. In preselection assays, both populations exhibited lower survival, slower development, and smaller size on a third host (adzuki bean), and the difference in performance between the ancestral and novel hosts was especially high for the African population. Replicate lines of each population were switched to adzuki bean or maintained on the ancestral host, and beetle performance was measured on both hosts after 12 generations. Survival on adzuki bean increased substantially in the adzuki-bean lines of the African population, but improved only slightly in the Asian lines. Similarly, only the African adzuki-bean lines exhibited significantly faster development on adzuki bean. Improved performance on adzuki bean did not simultaneously reduce performance on the ancestral host. Together with previous studies, these results confirm that populations of C. maculatus often possess sufficient standing genetic variation for rapid adaptation to a novel host, but the magnitude of the response may depend on the source population. Although international trade in grain legumes can expand beetle host ranges and produce unusual biotypes, the consistent absence of strong genetic trade-offs in larval performance or adult oviposition across hosts makes it unlikely that this insect would form distinct host races.

  18. Analysis of self-overlap reveals trade-offs in plankton swimming trajectories.

    PubMed

    Bianco, Giuseppe; Mariani, Patrizio; Visser, Andre W; Mazzocchi, Maria Grazia; Pigolotti, Simone

    2014-07-06

    Movement is a fundamental behaviour of organisms that not only brings about beneficial encounters with resources and mates, but also at the same time exposes the organism to dangerous encounters with predators. The movement patterns adopted by organisms should reflect a balance between these contrasting processes. This trade-off can be hypothesized as being evident in the behaviour of plankton, which inhabit a dilute three-dimensional environment with few refuges or orienting landmarks. We present an analysis of the swimming path geometries based on a volumetric Monte Carlo sampling approach, which is particularly adept at revealing such trade-offs by measuring the self-overlap of the trajectories. Application of this method to experimentally measured trajectories reveals that swimming patterns in copepods are shaped to efficiently explore volumes at small scales, while achieving a large overlap at larger scales. Regularities in the observed trajectories make the transition between these two regimes always sharper than in randomized trajectories or as predicted by random walk theory. Thus, real trajectories present a stronger separation between exploration for food and exposure to predators. The specific scale and features of this transition depend on species, gender and local environmental conditions, pointing at adaptation to state and stage-dependent evolutionary trade-offs.

  19. Analysis of self-overlap reveals trade-offs in plankton swimming trajectories

    PubMed Central

    Bianco, Giuseppe; Mariani, Patrizio; Visser, Andre W.; Mazzocchi, Maria Grazia; Pigolotti, Simone

    2014-01-01

    Movement is a fundamental behaviour of organisms that not only brings about beneficial encounters with resources and mates, but also at the same time exposes the organism to dangerous encounters with predators. The movement patterns adopted by organisms should reflect a balance between these contrasting processes. This trade-off can be hypothesized as being evident in the behaviour of plankton, which inhabit a dilute three-dimensional environment with few refuges or orienting landmarks. We present an analysis of the swimming path geometries based on a volumetric Monte Carlo sampling approach, which is particularly adept at revealing such trade-offs by measuring the self-overlap of the trajectories. Application of this method to experimentally measured trajectories reveals that swimming patterns in copepods are shaped to efficiently explore volumes at small scales, while achieving a large overlap at larger scales. Regularities in the observed trajectories make the transition between these two regimes always sharper than in randomized trajectories or as predicted by random walk theory. Thus, real trajectories present a stronger separation between exploration for food and exposure to predators. The specific scale and features of this transition depend on species, gender and local environmental conditions, pointing at adaptation to state and stage-dependent evolutionary trade-offs. PMID:24789560

  20. Size evolution in microorganisms masks trade-offs predicted by the growth rate hypothesis.

    PubMed

    Gounand, Isabelle; Daufresne, Tanguy; Gravel, Dominique; Bouvier, Corinne; Bouvier, Thierry; Combe, Marine; Gougat-Barbera, Claire; Poly, Franck; Torres-Barceló, Clara; Mouquet, Nicolas

    2016-12-28

    Adaptation to local resource availability depends on responses in growth rate and nutrient acquisition. The growth rate hypothesis (GRH) suggests that growing fast should impair competitive abilities for phosphorus and nitrogen due to high demand for biosynthesis. However, in microorganisms, size influences both growth and uptake rates, which may mask trade-offs and instead generate a positive relationship between these traits (size hypothesis, SH). Here, we evolved a gradient of maximum growth rate (μmax) from a single bacterium ancestor to test the relationship among μmax, competitive ability for nutrients and cell size, while controlling for evolutionary history. We found a strong positive correlation between μmax and competitive ability for phosphorus, associated with a trade-off between μmax and cell size: strains selected for high μmax were smaller and better competitors for phosphorus. Our results strongly support the SH, while the trade-offs expected under GRH were not apparent. Beyond plasticity, unicellular populations can respond rapidly to selection pressure through joint evolution of their size and maximum growth rate. Our study stresses that physiological links between these traits tightly shape the evolution of competitive strategies.

  1. Information trade-offs for optical quantum communication.

    PubMed

    Wilde, Mark M; Hayden, Patrick; Guha, Saikat

    2012-04-06

    Recent work has precisely characterized the achievable trade-offs between three key information processing tasks-classical communication (generation or consumption), quantum communication (generation or consumption), and shared entanglement (distribution or consumption), measured in bits, qubits, and ebits per channel use, respectively. Slices and corner points of this three-dimensional region reduce to well-known protocols for quantum channels. A trade-off coding technique can attain any point in the region and can outperform time sharing between the best-known protocols for accomplishing each information processing task by itself. Previously, the benefits of trade-off coding that had been found were too small to be of practical value (viz., for the dephasing and the universal cloning machine channels). In this Letter, we demonstrate that the associated performance gains are in fact remarkably high for several physically relevant bosonic channels that model free-space or fiber-optic links, thermal-noise channels, and amplifiers. We show that significant performance gains from trade-off coding also apply when trading photon-number resources between transmitting public and private classical information simultaneously over secret-key-assisted bosonic channels.

  2. Information Trade-Offs for Optical Quantum Communication

    NASA Astrophysics Data System (ADS)

    Wilde, Mark M.; Hayden, Patrick; Guha, Saikat

    2012-04-01

    Recent work has precisely characterized the achievable trade-offs between three key information processing tasks—classical communication (generation or consumption), quantum communication (generation or consumption), and shared entanglement (distribution or consumption), measured in bits, qubits, and ebits per channel use, respectively. Slices and corner points of this three-dimensional region reduce to well-known protocols for quantum channels. A trade-off coding technique can attain any point in the region and can outperform time sharing between the best-known protocols for accomplishing each information processing task by itself. Previously, the benefits of trade-off coding that had been found were too small to be of practical value (viz., for the dephasing and the universal cloning machine channels). In this Letter, we demonstrate that the associated performance gains are in fact remarkably high for several physically relevant bosonic channels that model free-space or fiber-optic links, thermal-noise channels, and amplifiers. We show that significant performance gains from trade-off coding also apply when trading photon-number resources between transmitting public and private classical information simultaneously over secret-key-assisted bosonic channels.

  3. Thermal performance trade-offs for point focusing solar collectors

    NASA Technical Reports Server (NTRS)

    Wen, L.

    1978-01-01

    Solar thermal conversion performance is assessed in this paper for representative point focusing distributed systems. Trade-off comparisons are made in terms of concentrator quality, solar receiver operating temperature, and power conversion efficiency. Normalized system performance is presented on a unit concentrator area basis for integrated annual electric energy production.

  4. Immune function trade-offs in response to parasite threats.

    PubMed

    Kirschman, Lucas J; Quade, Adam H; Zera, Anthony J; Warne, Robin W

    2017-04-01

    Immune function is often involved in physiological trade-offs because of the energetic costs of maintaining constitutive immunity and mounting responses to infection. However, immune function is a collection of discrete immunity factors and animals should allocate towards factors that combat the parasite threat with the highest fitness cost. For example, animals on dispersal fronts of expanding population may be released from density-dependent diseases. The costs of immunity, however, and life history trade-offs in general, are often context dependent. Trade-offs are often most apparent under conditions of unusually limited resources or when animals are particularly stressed, because the stress response can shift priorities. In this study we tested how humoral and cellular immune factors vary between phenotypes of a wing dimorphic cricket and how physiological stress influences these immune factors. We measured constitutive lysozyme activity, a humoral immune factor, and encapsulation response, a cellular immune factor. We also stressed the crickets with a sham predator in a full factorial design. We found that immune strategy could be explained by the selective pressures encountered by each morph and that stress decreased encapsulation, but not lysozyme activity. These results suggest a possible trade-off between humoral and cellular immunity. Given limited resources and the expense of immune factors, parasite pressures could play a key factor in maintaining insect polyphenism via disruptive selection.

  5. A Human Trade-off for Word Processing Specialists

    ERIC Educational Resources Information Center

    Morrison, James L.

    1974-01-01

    Business educators must make students aware of the pitfalls in the current move toward office specialization in the word processing movement. The adoption of technological methodology can cause a human trade-off in which people become mere agents of machines. Business educators must begin to emphasize the needs of individuals. (SC)

  6. QTL analysis of root morphology, flowering time, and yield reveals trade-offs in response to drought in Brassica napus.

    PubMed

    Fletcher, Richard S; Mullen, Jack L; Heiliger, Annie; McKay, John K

    2015-01-01

    Drought escape and dehydration avoidance represent alternative strategies for drought adaptation in annual crops. The mechanisms underlying these two strategies are reported to have a negative correlation, suggesting a trade-off. We conducted a quantitative trait locus (QTL) analysis of flowering time and root mass, traits representing each strategy, in Brassica napus to understand if a trade-off exists and what the genetic basis might be. Our field experiment used a genotyped population of doubled haploid lines and included both irrigated and rainfed treatments, allowing analysis of plasticity in each trait. We found strong genetic correlations among all traits, suggesting a trade-off among traits may exist. Summing across traits and treatments we found 20 QTLs, but many of these co-localized to two major QTLs, providing evidence that the trade-off is genetically constrained. To understand the mechanistic relationship between root mass, flowering time, and QTLs, we analysed the data by conditioning upon correlated traits. Our results suggest a causal model where such QTLs affect root mass directly as well as through their impacts on flowering time. Additionally, we used draft Brassica genomes to identify orthologues of well characterized Arabidopsis thaliana flowering time genes as candidate genes. This research provides valuable clues to breeding for drought adaptation as it is the first to analyse the inheritance of the root system in B. napus in relation to drought.

  7. Defying the activity-stability trade-off in enzymes: taking advantage of entropy to enhance activity and thermostability.

    PubMed

    Siddiqui, Khawar Sohail

    2017-05-01

    The biotechnological applications of enzymes are limited due to the activity-stability trade-off, which implies that an increase in activity is accompanied by a concomitant decrease in protein stability. This premise is based on thermally adapted homologous enzymes where cold-adapted enzymes show high intrinsic activity linked to enhanced thermolability. In contrast, thermophilic enzymes show low activity around ambient temperatures. Nevertheless, genetically and chemically modified enzymes are beginning to show that the activity-stability trade-off can be overcome. In this review, the origin of the activity-stability trade-off, the thermodynamic basis for enhanced activity and stability, and various approaches for escaping the activity-stability trade-off are discussed. The role of entropy in enhancing both the activity and the stability of enzymes is highlighted with a special emphasis placed on the involvement of solvent water molecules. This review is concluded with suggestions for further research, which underscores the implications of these findings in the context of productivity curves, the Daniel-Danson equilibrium model, catalytic antibodies, and life on cold planets.

  8. QTL analysis of root morphology, flowering time, and yield reveals trade-offs in response to drought in Brassica napus

    PubMed Central

    Fletcher, Richard S.; Mullen, Jack L.; Heiliger, Annie; McKay, John K.

    2015-01-01

    Drought escape and dehydration avoidance represent alternative strategies for drought adaptation in annual crops. The mechanisms underlying these two strategies are reported to have a negative correlation, suggesting a trade-off. We conducted a quantitative trait locus (QTL) analysis of flowering time and root mass, traits representing each strategy, in Brassica napus to understand if a trade-off exists and what the genetic basis might be. Our field experiment used a genotyped population of doubled haploid lines and included both irrigated and rainfed treatments, allowing analysis of plasticity in each trait. We found strong genetic correlations among all traits, suggesting a trade-off among traits may exist. Summing across traits and treatments we found 20 QTLs, but many of these co-localized to two major QTLs, providing evidence that the trade-off is genetically constrained. To understand the mechanistic relationship between root mass, flowering time, and QTLs, we analysed the data by conditioning upon correlated traits. Our results suggest a causal model where such QTLs affect root mass directly as well as through their impacts on flowering time. Additionally, we used draft Brassica genomes to identify orthologues of well characterized Arabidopsis thaliana flowering time genes as candidate genes. This research provides valuable clues to breeding for drought adaptation as it is the first to analyse the inheritance of the root system in B. napus in relation to drought. PMID:25371500

  9. Evolution of complex life cycles in trophically transmitted helminths. II. How do life-history stages adapt to their hosts?

    PubMed

    Parker, G A; Ball, M A; Chubb, J C

    2015-02-01

    We review how trophically transmitted helminths adapt to the special problems associated with successive hosts in complex cycles. In intermediate hosts, larvae typically show growth arrest at larval maturity (GALM). Theoretical models indicate that optimization of size at GALM requires larval mortality rate to increase with time between infection and GALM: low larval growth or paratenicity (no growth) arises from unfavourable growth and mortality rates in the intermediate host and low transmission rates to the definitive host. Reverse conditions favour high GALM size or continuous growth. Some support is found for these predictions. Intermediate host manipulation involves predation suppression (which decreases host vulnerability before the larva can establish in its next host) and predation enhancement (which increases host vulnerability after the larva can establish in its next host). Switches between suppression and enhancement suggest adaptive manipulation. Manipulation conflicts can occur between larvae of different ages/species a host individual. Larvae must usually develop to GALM before becoming infective to the next host, possibly due to trade-offs, e.g. between growth/survival in the present host and infection ability for the next host. In definitive hosts, if mortality rate is constant, optimal growth before switching to reproduction is set by the growth/morality rate ratio. Rarely, no growth occurs in definitive hosts, predicted (with empirical support) when larval size on infection exceeds growth/mortality rate. Tissue migration patterns and residence sites may be explained by variations in growth/mortality rates between host gut and soma, migration costs and benefits of releasing eggs in the gut.

  10. Why equalising trade-offs aren't always neutral.

    PubMed

    Turnbull, Lindsay A; Rees, Mark; Purves, Drew W

    2008-10-01

    Equalising trade-offs, such as seed mass vs. number, have been invoked to reconcile neutral theory with observed differences between species. This is an appealing explanation for the dramatic seed size variation seen within guilds of otherwise similar plants: under size-symmetric competition, where resource capture is proportional to mass, the outcome of competition should be insensitive to whether species produce many small seeds or few large ones. However, under this assumption, stochastic variation in seed rain leads to exclusion of all but the smallest-seeded species. Thus stochasticity in seed arrivals, a process that was previously thought to generate drift, instead results in deterministic competitive exclusion. A neutral outcome is possible under one special case of a more general equalising framework, where seed mass affects survival but not competition. Further exploration of the feasibility of neutral trade-offs is needed to understand the respective roles of neutrality and niche structure in community dynamics.

  11. Trade-off analysis for environmental projects: An annotated bibliography

    SciTech Connect

    Feather, T.D.; Harrington, K.W.; Capan, D.T.

    1995-08-01

    This is a report with an attached annotated bibliography. This study explores the literature for analytical techniques that can support the complex decision-making process associated with Corps of Engineers environmental projects. The literature review focuses on opportunities for using trade-off methodologies and group processes in environmental plan formulation and evaluation. The work was conducted under the Evaluation Framework Work Unit within the Evaluation of Environmental Investments Research Program.

  12. Host Sexual Dimorphism and Parasite Adaptation

    PubMed Central

    Duneau, David; Ebert, Dieter

    2012-01-01

    In species with separate sexes, parasite prevalence and disease expression is often different between males and females. This effect has mainly been attributed to sex differences in host traits, such as immune response. Here, we make the case for how properties of the parasites themselves can also matter. Specifically, we suggest that differences between host sexes in many different traits, such as morphology and hormone levels, can impose selection on parasites. This selection can eventually lead to parasite adaptations specific to the host sex more commonly encountered, or to differential expression of parasite traits depending on which host sex they find themselves in. Parasites adapted to the sex of the host in this way can contribute to differences between males and females in disease prevalence and expression. Considering those possibilities can help shed light on host–parasite interactions, and impact epidemiological and medical science. PMID:22389630

  13. Speed and stamina trade-off in lacertid lizards.

    PubMed

    Vanhooydonck, B; Van Damme, R; Aerts, P

    2001-05-01

    Morphological and physiological considerations suggest that sprinting ability and endurance capacity put conflicting demands on the design of an animal's locomotor apparatus and therefore cannot be maximized simultaneously. To test this hypothesis, we correlated size-corrected maximal sprint speed and stamina of 12 species of lacertid lizards. Phylogenetically independent contrasts of sprint speed and stamina showed a significant negative relationship, giving support to the idea of an evolutionary trade-off between the two performance measures. To test the hypothesis that the trade-off is mediated by a conflict in morphological requirements, we correlated both performance traits with snout-vent length, size-corrected estimates of body mass and limb length, and relative hindlimb length (the residuals of the relationship between hind- and forelimb length). Fast-running species had hindlimbs that were long compared to their forelimbs. None of the other size or shape variables showed a significant relationship with speed or endurance. We conclude that the evolution of sprint capacity may be constrained by the need for endurance capacity and vice versa, but the design conflict underlying this trade-off has yet to be identified.

  14. Hormesis results in trade-offs with immunity.

    PubMed

    McClure, Colin D; Zhong, Weihao; Hunt, Vicky L; Chapman, Fiona M; Hill, Fiona V; Priest, Nicholas K

    2014-08-01

    Many have argued that we may be able to extend life and improve human health through hormesis, the beneficial effects of low-level toxins and other stressors. But, studies of hormesis in model systems have not yet established whether stress-induced benefits are cost free, artifacts of inbreeding, or come with deleterious side effects. Here, we provide evidence that hormesis results in trade-offs with immunity. We find that a single topical dose of dead spores of the entomopathogenic fungus, Metarhizium robertsii, increases the longevity of the fruit fly, Drosophila melanogaster, without significant decreases in fecundity. We find that hormetic benefits of pathogen challenge are greater in lines that lack key components of antifungal immunity (Dif and Turandot M). And, in outbred fly lines, we find that topical pathogen challenge enhances both survival and fecundity, but reduces ability to fight off live infections. The results provide evidence that hormesis is manifested by stress-induced trade-offs with immunity, not cost-free benefits or artifacts of inbreeding. Our findings illuminate mechanisms underlying pathogen-induced life-history trade-offs, and indicate that reduced immune function may be an ironic side effect of the "elixirs of life."

  15. HORMESIS RESULTS IN TRADE-OFFS WITH IMMUNITY

    PubMed Central

    McClure, Colin D; Zhong, Weihao; Hunt, Vicky L; Chapman, Fiona M; Hill, Fiona V; Priest, Nicholas K

    2014-01-01

    Many have argued that we may be able to extend life and improve human health through hormesis, the beneficial effects of low-level toxins and other stressors. But, studies of hormesis in model systems have not yet established whether stress-induced benefits are cost free, artifacts of inbreeding, or come with deleterious side effects. Here, we provide evidence that hormesis results in trade-offs with immunity. We find that a single topical dose of dead spores of the entomopathogenic fungus, Metarhizium robertsii, increases the longevity of the fruit fly, Drosophila melanogaster, without significant decreases in fecundity. We find that hormetic benefits of pathogen challenge are greater in lines that lack key components of antifungal immunity (Dif and Turandot M). And, in outbred fly lines, we find that topical pathogen challenge enhances both survival and fecundity, but reduces ability to fight off live infections. The results provide evidence that hormesis is manifested by stress-induced trade-offs with immunity, not cost-free benefits or artifacts of inbreeding. Our findings illuminate mechanisms underlying pathogen-induced life-history trade-offs, and indicate that reduced immune function may be an ironic side effect of the “elixirs of life.” PMID:24862588

  16. Speed and Endurance Do Not Trade Off in Phrynosomatid Lizards.

    PubMed

    de Albuquerque, Ralph Lacerda; Bonine, Kevin E; Garland, Theodore

    2015-01-01

    Trade-offs are a common focus of study in evolutionary biology and in studies of locomotor physiology and biomechanics. A previous comparative study of 12 species of European lacertid lizards found a statistically significant negative correlation between residual locomotor speed and stamina (controlling for variation in body size), consistent with ideas about trade-offs in performance based on variation in muscle fiber type composition and other subordinate traits. To begin examining the generality of this finding in other groups of squamates, we measured maximal sprint running speed on a high-speed treadmill and endurance at 1.0 km/h (0.28 m/s) in 14 species of North American phrynosomatid lizards, plus a sample of nine additional species to encompass some of the broadscale diversity of lizards. We used both conventional and phylogenetically informed regression analyses to control for some known causes of performance variation (body size, stockiness, body temperature) and then computed residual performance values. We found no evidence for a trade-off between speed and endurance among the 14 phrynosomatids or among the 23 species in the extended data set. Possible explanations for the apparent difference between lacertids and phrynosomatids are discussed.

  17. Trade-offs in the design of experiments.

    PubMed

    Wiley, R Haven

    2009-11-01

    This comment supplements and clarifies issues raised by J. C. Schank and T. J. Koehnle (2009) in their critique of experimental design. First, the pervasiveness of trade-offs in the design of experiments is emphasized (Wiley, 2003). Particularly germane to Schank and Koehnle's discussion are the inevitable trade-offs in any decisions to include blocking or to standardize conditions in experiments. Second, the interpretation of multiple tests of a hypothesis is clarified. Only when interest focuses on any, rather than each, of N possible responses is it appropriate to adjust criteria for statistical significance of the results. Finally, a misunderstanding is corrected about a disadvantage of large experiments (Wiley, 2003). Experiments with large samples raise the possibility of small, but statistically significant, biases even after randomization of treatments. Because these small biases are difficult for experimenters and readers to notice, large experiments demonstrating small effects require special scrutiny. Such experiments are justified only when they involve minimal human intervention and maximal standardization. Justifications for the inevitable trade-offs in experimental design require careful attention when reporting any experiment.

  18. The energy trade-off between growth and longevity.

    PubMed

    Hou, Chen

    2013-09-01

    Understanding the trade-offs between organisms' life history traits has been a major goal of physiology, ecology and evolution. In the last few decades, two types of intra-specific studies have highlighted the trade-off between growth and longevity. First, diet restriction (DR), as an environmental intervention, has been shown to suppress growth and extend the lifespan of a broad range of animals. Second, genetic studies have also shown that mice, whose growth hormone function is genetically modified (GM), grow slower and live longer than their wild-type siblings. Despite a wealth of empirical data, still largely missing is a theoretical framework that specifies and makes quantitative predictions on this trade-off. Here, I present a mechanistic model based on the principles of energy conservation. The model quantifies explicitly how DR and GM alter the animal's energy budget, and channel metabolic energy to somatic maintenance by suppressing growth, thereby extending lifespan. Data from a diverse set of empirical studies on small rodents supports the predictions of the model. More importantly, the model reveals that although DR and GM are two different methods to extend lifespan, i.e., environmental vs. genetic, the underlying mechanisms of them are the same from the energetic viewpoint.

  19. Functional Trade-Offs in Promiscuous Enzymes Cannot Be Explained by Intrinsic Mutational Robustness of the Native Activity

    PubMed Central

    Kaltenbach, Miriam; Emond, Stephane; Tokuriki, Nobuhiko

    2016-01-01

    The extent to which an emerging new function trades off with the original function is a key characteristic of the dynamics of enzyme evolution. Various cases of laboratory evolution have unveiled a characteristic trend; a large increase in a new, promiscuous activity is often accompanied by only a mild reduction of the native, original activity. A model that associates weak trade-offs with “evolvability” was put forward, which proposed that enzymes possess mutational robustness in the native activity and plasticity in promiscuous activities. This would enable the acquisition of a new function without compromising the original one, reducing the benefit of early gene duplication and therefore the selection pressure thereon. Yet, to date, no experimental study has examined this hypothesis directly. Here, we investigate the causes of weak trade-offs by systematically characterizing adaptive mutations that occurred in two cases of evolutionary transitions in enzyme function: (1) from phosphotriesterase to arylesterase, and (2) from atrazine chlorohydrolase to melamine deaminase. Mutational analyses in various genetic backgrounds revealed that, in contrast to the prevailing model, the native activity is less robust to mutations than the promiscuous activity. For example, in phosphotriesterase, the deleterious effect of individual mutations on the native phosphotriesterase activity is much larger than their positive effect on the promiscuous arylesterase activity. Our observations suggest a revision of the established model: weak trade-offs are not caused by an intrinsic robustness of the native activity and plasticity of the promiscuous activity. We propose that upon strong adaptive pressure for the new activity without selection against the original one, selected mutations will lead to the largest possible increases in the new function, but whether and to what extent they decrease the old function is irrelevant, creating a bias towards initially weak trade-offs and

  20. Effects of Emotion on Memory Specificity: Memory Trade-Offs Elicited by Negative Visually Arousing Stimuli

    ERIC Educational Resources Information Center

    Kensinger, Elizabeth A.; Garoff-Eaton, Rachel J.; Schacter, Daniel L.

    2007-01-01

    Two different types of trade-offs have been discussed with regard to memory for emotional information: A trade-off in the ability to remember the gist versus the visual detail of emotional information, and a trade-off in the ability to remember the central emotional elements of an event versus the nonemotional (peripheral) elements of that same…

  1. Trade-offs between savanna woody plant diversity and carbon storage in the Brazilian Cerrado.

    PubMed

    Pellegrini, Adam F A; Socolar, Jacob B; Elsen, Paul R; Giam, Xingli

    2016-10-01

    Incentivizing carbon storage can be a win-win pathway to conserving biodiversity and mitigating climate change. In savannas, however, the situation is more complex. Promoting carbon storage through woody encroachment may reduce plant diversity of savanna endemics, even as the diversity of encroaching forest species increases. This trade-off has important implications for the management of biodiversity and carbon in savanna habitats, but has rarely been evaluated empirically. We quantified the nature of carbon-diversity relationships in the Brazilian Cerrado by analyzing how woody plant species richness changed with carbon storage in 206 sites across the 2.2 million km(2) region at two spatial scales. We show that total woody plant species diversity increases with carbon storage, as expected, but that the richness of endemic savanna woody plant species declines with carbon storage both at the local scale, as woody biomass accumulates within plots, and at the landscape scale, as forest replaces savanna. The sharpest trade-offs between carbon storage and savanna diversity occurred at the early stages of carbon accumulation at the local scale but the final stages of forest encroachment at the landscape scale. Furthermore, the loss of savanna species quickens in the final stages of forest encroachment, and beyond a point, savanna species losses outpace forest species gains with increasing carbon accumulation. Our results suggest that although woody encroachment in savanna ecosystems may provide substantial carbon benefits, it comes at the rapidly accruing cost of woody plant species adapted to the open savanna environment. Moreover, the dependence of carbon-diversity trade-offs on the amount of savanna area remaining requires land managers to carefully consider local conditions. Widespread woody encroachment in both Australian and African savannas and grasslands may present similar threats to biodiversity.

  2. Modeling the trade-off between diet costs and methane emissions: A goal programming approach.

    PubMed

    Moraes, L E; Fadel, J G; Castillo, A R; Casper, D P; Tricarico, J M; Kebreab, E

    2015-08-01

    Enteric methane emission is a major greenhouse gas from livestock production systems worldwide. Dietary manipulation may be an effective emission-reduction tool; however, the associated costs may preclude its use as a mitigation strategy. Several studies have identified dietary manipulation strategies for the mitigation of emissions, but studies examining the costs of reducing methane by manipulating diets are scarce. Furthermore, the trade-off between increase in dietary costs and reduction in methane emissions has only been determined for a limited number of production scenarios. The objective of this study was to develop an optimization framework for the joint minimization of dietary costs and methane emissions based on the identification of a set of feasible solutions for various levels of trade-off between emissions and costs. Such a set of solutions was created by the specification of a systematic grid of goal programming weights, enabling the decision maker to choose the solution that achieves the desired trade-off level. Moreover, the model enables the calculation of emission-mitigation costs imputing a trading value for methane emissions. Emission imputed costs can be used in emission-unit trading schemes, such as cap-and-trade policy designs. An application of the model using data from lactating cows from dairies in the California Central Valley is presented to illustrate the use of model-generated results in the identification of optimal diets when reducing emissions. The optimization framework is flexible and can be adapted to jointly minimize diet costs and other potential environmental impacts (e.g., nitrogen excretion). It is also flexible so that dietary costs, feed nutrient composition, and animal nutrient requirements can be altered to accommodate various production systems.

  3. Early developmental exposures shape trade-offs between acquired and innate immunity in humans

    PubMed Central

    Georgiev, Alexander V.; Kuzawa, Christopher W.; McDade, Thomas W.

    2016-01-01

    Background and objectives Life history theory predicts resource allocation trade-offs between competing functions and processes. We test the hypothesis that relative investment towards innate versus acquired immunity in humans is subject to such trade-offs and that three types of early developmental exposures are particularly salient in shaping adult immunophenotype: (i) pathogen exposure, (ii) nutritional resources; and (iii) extrinsic mortality cues. Methodology We quantified one aspect each of innate and acquired immune function, via C-reactive protein and Epstein–Barr virus antibodies, respectively, in a sample of 1248 men and women from the Philippines (ca. 21.5 years old). Early developmental exposures were assessed via long-term data collected prospectively since participants’ birth (1983–4). We calculated a standardized ratio to assess relative bias towards acquired versus innate immune function and examined its relationship to a suite of predictors via multiple regression. Results In partial support of our predictions, some of the measures of higher pathogen exposure, greater availability of nutritional resources, and lower extrinsic mortality cues in early life were associated with a bias toward acquired immunity in both men and women. The immune profile of women, in particular, appeared to be more sensitive to early life pathogen exposures than those of men. Finally, contrary to prediction, women exhibited a greater relative investment toward innate, not acquired, immunity. Conclusions and implications Early environments can exert considerable influence on the development of immunity. They affect trade-offs between innate and acquired immunity, which show adaptive plasticity and may differ in their influence in men and women. PMID:27530543

  4. The immunomodulatory role of the hypothalamus-pituitary-gonad axis: Proximate mechanism for reproduction-immune trade offs?

    PubMed

    Segner, Helmut; Verburg-van Kemenade, B M Lidy; Chadzinska, Magdalena

    2017-01-01

    The present review discusses the communication between the hypothalamic-pituitary-gonad (HPG) axis and the immune system of vertebrates, attempting to situate the HPG-immune interaction into the context of life history trade-offs between reproductive and immune functions. More specifically, (i) we review molecular and cellular interactions between hormones of the HPG axis, and, as far as known, the involved mechanisms on immune functions, (ii) we evaluate whether the HPG-immune crosstalk serves as proximate mechanism mediating reproductive-immune trade-offs, and (iii) we ask whether the nature of the HPG-immune interaction is conserved throughout vertebrate evolution, despite the changes in immune functions, reproductive modes, and life histories. In all vertebrate classes studied so far, HPG hormones have immunomodulatory functions, and indications exist that they contribute to reproduction-immunity resource trade-offs, although the very limited information available for most non-mammalian vertebrates makes it difficult to judge how comparable or different the interactions are. There is good evidence that the HPG-immune crosstalk is part of the proximate mechanisms underlying the reproductive-immune trade-offs of vertebrates, but it is only one factor in a complex network of factors and processes. The fact that the HPG-immune interaction is flexible and can adapt to the functional and physiological requirements of specific life histories. Moreover, the assumption of a relatively fixed pattern of HPG influence on immune functions, with, for example, androgens always leading to immunosuppression and estrogens always being immunoprotective, is probably oversimplified, but the HPG-immune interaction can vary depending on the physiological and envoironmental context. Finally, the HPG-immune interaction is not only driven by resource trade-offs, but additional factors such as, for instance, the evolution of viviparity shape this neuroendocrine-immune relationship.

  5. Ant Colonies Do Not Trade-Off Reproduction against Maintenance.

    PubMed

    Kramer, Boris H; Schrempf, Alexandra; Scheuerlein, Alexander; Heinze, Jürgen

    2015-01-01

    The question on how individuals allocate resources into maintenance and reproduction is one of the central questions in life history theory. Yet, resource allocation into maintenance on the organismic level can only be measured indirectly. This is different in a social insect colony, a "superorganism" where workers represent the soma and the queen the germ line of the colony. Here, we investigate whether trade-offs exist between maintenance and reproduction on two levels of biological organization, queens and colonies, by following single-queen colonies of the ant Cardiocondyla obscurior throughout the entire lifespan of the queen. Our results show that maintenance and reproduction are positively correlated on the colony level, and we confirm results of an earlier study that found no trade-off on the individual (queen) level. We attribute this unexpected outcome to the existence of a positive feedback loop where investment into maintenance (workers) increases the rate of resource acquisition under laboratory conditions. Even though food was provided ad libitum, variation in productivity among the colonies suggests that resources can only be utilized and invested into additional maintenance and reproduction by the colony if enough workers are available. The resulting relationship between per-capita and colony productivity in our study fits well with other studies conducted in the field, where decreasing per-capita productivity and the leveling off of colony productivity have been linked to density dependent effects due to competition among colonies. This suggests that the absence of trade-offs in our laboratory study might also be prevalent under natural conditions, leading to a positive association of maintenance, (= growth) and reproduction. In this respect, insect colonies resemble indeterminate growing organisms.

  6. Laser space rendevous and docking trade-off

    NASA Technical Reports Server (NTRS)

    1974-01-01

    A spaceborne LADAR sensor, which will meet the requirements for rendezvous and docking with a cooperative object in synchronous orbit is presented. The sensor is being configured around a pulsed CO2 laser which can be constructed and deployed using technology which presently exists or is being developed, and which appears to lend itself very well to the envisioned family of space missions. In order to determine the applicability of the type of sensor being considered, the performance of a family of candidate sensors is being traded off as a function of size, weight, and power consumption. The maximum ranges being considered are 50, 100, 200, and 300 nautical miles.

  7. Metabolic Trade-Offs Promote Diversity in a Model Ecosystem

    NASA Astrophysics Data System (ADS)

    Posfai, Anna; Taillefumier, Thibaud; Wingreen, Ned S.

    2017-01-01

    In nature, a large number of species can coexist on a small number of shared resources; however, resource-competition models predict that the number of species in steady coexistence cannot exceed the number of resources. Motivated by recent studies of phytoplankton, we introduce trade-offs into a resource-competition model and find that an unlimited number of species can coexist. Our model spontaneously reproduces several notable features of natural ecosystems, including keystone species and population dynamics and abundances characteristic of neutral theory, despite an underlying non-neutral competition for resources.

  8. Egg size-number trade-off and a decline in oviposition site choice quality: female Pararge aegeria butterflies pay a cost of having males present at oviposition.

    PubMed

    Gibbs, M; Lace, L A; Jones, M J; Moore, A J

    2005-12-06

    Once mated, the optimal strategy for females of the monandrous butterfly, Pararge aegeria, is to avoid male contact and devote as much time as possible to ovipositing, as there is little advantage for females to engage in multiple matings. In other butterfly species the presence of males during egg laying has been shown to affect aspects of oviposition behavior and it has been suggested that repeated interference from males has the potential to reduce reproductive output. The aim of this study was to assess the effects of male presence during oviposition on reproductive output and behavior of a population of P. aegeria obtained from Madeira Island, Portugal, and maintained in the laboratory. Two experiments were performed where females were housed individually in small cages. Experiment 1 examined how social factors influenced the egg laying behavior of females. To do this the presence or absence of males was manipulated and egg size and number was measured over the first 14 days of oviposition. It was observed that when males were present during oviposition females made a trade-off between egg size and number. Experiment 2 examined how social factors affected oviposition site choice. Again, male presence/absence was manipulated, but in this experiment where the female laid her egg in relation to host quality was scored, and the size of the egg laid was measured. In the absence of males females selectively positioned their larger eggs on good quality host plants. However, selective oviposition was no longer observed when females were in the presence of males. We suggest that P. aegeria females from the Madeira Island population are adapted for a flexible oviposition strategy, governed by external cues, allowing a trade-off between egg size and number when the time available for egg laying is limiting.

  9. IXO/XMS Detector Trade-Off Study

    NASA Technical Reports Server (NTRS)

    Kilbourne, Caroline Anne; deKorte, P.; Smith, S.; Hoevers, H.; vdKuur, J.; Ezoe, Y.; Ullom, J.

    2010-01-01

    This document presents the outcome of the detector trade-off for the XMS instrument on IXO. This trade-off is part of the Cryogenic instrument Phase-A study as proposed to ESA in the Declaration of Interest SRONXMS-PL-2009-003 dated June 6, 2009. The detector consists of two components: a core array for the highest spectral resolution and an outer array to increase the field of view substantially with modest increase in the number of read-out channels. Degraded resolution of the outer array in comparison with the core array is accepted in order to make this scheme possible. The two detector components may be a single unit or separate units. These arrays comprise pixels and the components that allow them to be arrayed. Each pixel comprises a thermometer, an absorber, and the thermal links between them and to the rest of the array. These links may be interfaces or distinct components. The array infrastructure comprises the mechanical structure of the array, the arrangement of the leads, and features added to improve the integrated thermal properties of the array in the focal-plane assembly.

  10. DISTRIBUTED PROCESSING TRADE-OFF MODEL FOR ELECTRIC UTILITY OPERATION

    NASA Technical Reports Server (NTRS)

    Klein, S. A.

    1994-01-01

    The Distributed processing Trade-off Model for Electric Utility Operation is based upon a study performed for the California Institute of Technology's Jet Propulsion Laboratory. This study presented a technique that addresses the question of trade-offs between expanding a communications network or expanding the capacity of distributed computers in an electric utility Energy Management System (EMS). The technique resulted in the development of a quantitative assessment model that is presented in a Lotus 1-2-3 worksheet environment. The model gives EMS planners a macroscopic tool for evaluating distributed processing architectures and the major technical and economic tradeoffs as well as interactions within these architectures. The model inputs (which may be varied according to application and need) include geographic parameters, data flow and processing workload parameters, operator staffing parameters, and technology/economic parameters. The model's outputs are total cost in various categories, a number of intermediate cost and technical calculation results, as well as graphical presentation of Costs vs. Percent Distribution for various parameters. The model has been implemented on an IBM PC using the LOTUS 1-2-3 spreadsheet environment and was developed in 1986. Also included with the spreadsheet model are a number of representative but hypothetical utility system examples.

  11. Trade-offs between performance and variability in the escape responses of bluegill sunfish (Lepomis macrochirus)

    PubMed Central

    Hitchcock, Amanda C.; Chen, Tiffany; Connolly, Erin; Darakananda, Karin; Jeong, Janet; Quist, Arbor; Robbins, Allison; Ellerby, David J.

    2015-01-01

    Successful predator evasion is essential to the fitness of many animals. Variation in escape behaviour may be adaptive as it reduces predictability, enhancing escape success. High escape velocities and accelerations also increase escape success, but biomechanical factors likely constrain the behavioural range over which performance can be maximized. There may therefore be a trade-off between variation and performance during escape responses. We have used bluegill sunfish (Lepomis macrochirus) escape responses to examine this potential trade-off, determining the full repertoire of escape behaviour for individual bluegill sunfish and linking this to performance as indicated by escape velocity and acceleration. Fish escapes involve an initial C-bend of the body axis, followed by variable steering movements. These generate thrust and establish the escape direction. Directional changes during the initial C-bend were less variable than the final escape angle, and the most frequent directions were associated with high escape velocity. Significant inter-individual differences in escape angles magnified the overall variation, maintaining unpredictability from a predator perspective. Steering in the latter stages of the escape to establish the final escape trajectory also affected performance, with turns away from the stimulus associated with reduced velocity. This suggests that modulation of escape behaviour by steering may also have an associated performance cost. This has important implications for understanding the scope and control of intra- and inter-individual variation in escape behaviour and the associated costs and benefits. PMID:25910940

  12. Physiological and genomic basis of mechanical-functional trade-off in plant vasculature

    PubMed Central

    Sengupta, Sonali; Majumder, Arun Lahiri

    2014-01-01

    Some areas in plant abiotic stress research are not frequently addressed by genomic and molecular tools. One such area is the cross reaction of gravitational force with upward capillary pull of water and the mechanical-functional trade-off in plant vasculature. Although frost, drought and flooding stress greatly impact these physiological processes and consequently plant performance, the genomic and molecular basis of such trade-off is only sporadically addressed and so is its adaptive value. Embolism resistance is an important multiple stress- opposition trait and do offer scopes for critical insight to unravel and modify the input of living cells in the process and their biotechnological intervention may be of great importance. Vascular plants employ different physiological strategies to cope with embolism and variation is observed across the kingdom. The genomic resources in this area have started to emerge and open up possibilities of synthesis, validation and utilization of the new knowledge-base. This review article assesses the research till date on this issue and discusses new possibilities for bridging physiology and genomics of a plant, and foresees its implementation in crop science. PMID:24904619

  13. A newly evolved Drosophila Cytorace-9 shows trade-off between longevity and immune response.

    PubMed

    Sinam, Yoirentomba Meetei; Chatterjee, Arunita; Ranjini, Mysore S; Poojari, Adarsh; Nagarajan, Aarthi; Ramachandra, Nallur B; Nongthomba, Upendra

    2016-10-01

    Species with an efficient immune system would be at an advantage to evade pathogenic challenges and adapt to an ever changing ecological niche. The upkeep of immunity is a costly affair, thus trade-offs between immunity and other life history traits are expected. However, studies on the relation between immunity and life span have yielded paradoxical results. Drosophila Cytoraces, being at different stages of evolutionary divergence, provide an excellent experimental model system to study how evolving populations gain novel traits in the absence of selection. We found that in the absence of pathogenic infections, the Cytorace-9 flies lived longer than those of Cytorace-3. However, when these Cytoraces were challenged with different pathogenic microbes, the trend was opposite. After infection with pathogens, the long-lived Cytorace-9 survived worse than the short lived Cytorace-3, which can be attributed to a reduction in its immune response. This study provides evidence to support the existence of a trade-off between life span and immunity.

  14. Parasites and competitors suppress bacterial pathogen synergistically due to evolutionary trade-offs.

    PubMed

    Wang, Xiaofang; Wei, Zhong; Li, Mei; Wang, Xueqi; Shan, Anqi; Mei, Xinlan; Jousset, Alexandre; Shen, Qirong; Xu, Yangchun; Friman, Ville-Petri

    2016-12-07

    Parasites and competitors are important for regulating pathogen densities and subsequent disease dynamics. It is, however, unclear to what extent this is driven by ecological and evolutionary processes. Here, we used experimental evolution to study the eco-evolutionary feedbacks among Ralstonia solanacearum bacterial pathogen, Ralstonia-specific phage parasite, and Bacillus amyloliquefaciens competitor bacterium in the laboratory and plant rhizosphere. We found that while the phage had a small effect on pathogen densities on its own, it considerably increased the R. solanacearum sensitivity to antibiotics produced by B. amyloliquefaciens. Instead of density effects, this synergy was due to phage-driven increase in phage resistance that led to trade-off with the resistance to B. amyloliquefaciens antibiotics. While no evidence was found for pathogen resistance evolution to B. amyloliquefaciens antibiotics, the fitness cost of adaptation (reduced growth) was highest when the pathogen had evolved in the presence of both parasite and competitor. Qualitatively similar patterns were found between laboratory and greenhouse experiments even though the evolution of phage resistance was considerably attenuated in the tomato rhizosphere. These results suggest that evolutionary trade-offs can impose strong constraints on disease dynamics and that combining phages and antibiotic-producing bacteria could be an efficient way to control agricultural pathogens.

  15. Antagonistic pleiotropy and fitness trade-offs reveal specialist and generalist traits in strains of canine distemper virus.

    PubMed

    Nikolin, Veljko M; Osterrieder, Klaus; von Messling, Veronika; Hofer, Heribert; Anderson, Danielle; Dubovi, Edward; Brunner, Edgar; East, Marion L

    2012-01-01

    Theoretically, homogeneous environments favor the evolution of specialists whereas heterogeneous environments favor generalists. Canine distemper is a multi-host carnivore disease caused by canine distemper virus (CDV). The described cell receptor of CDV is SLAM (CD150). Attachment of CDV hemagglutinin protein (CDV-H) to this receptor facilitates fusion and virus entry in cooperation with the fusion protein (CDV-F). We investigated whether CDV strains co-evolved in the large, homogeneous domestic dog population exhibited specialist traits, and strains adapted to the heterogeneous environment of smaller populations of different carnivores exhibited generalist traits. Comparison of amino acid sequences of the SLAM binding region revealed higher similarity between sequences from Canidae species than to sequences from other carnivore families. Using an in vitro assay, we quantified syncytia formation mediated by CDV-H proteins from dog and non-dog CDV strains in cells expressing dog, lion or cat SLAM. CDV-H proteins from dog strains produced significantly higher values with cells expressing dog SLAM than with cells expressing lion or cat SLAM. CDV-H proteins from strains of non-dog species produced similar values in all three cell types, but lower values in cells expressing dog SLAM than the values obtained for CDV-H proteins from dog strains. By experimentally changing one amino acid (Y549H) in the CDV-H protein of one dog strain we decreased expression of specialist traits and increased expression of generalist traits, thereby confirming its functional importance. A virus titer assay demonstrated that dog strains produced higher titers in cells expressing dog SLAM than cells expressing SLAM of non-dog hosts, which suggested possible fitness benefits of specialization post-cell entry. We provide in vitro evidence for the expression of specialist and generalist traits by CDV strains, and fitness trade-offs across carnivore host environments caused by antagonistic

  16. Trade-offs in osmoregulation and parallel shifts in molecular function follow ecological transitions to freshwater in the Alewife

    USGS Publications Warehouse

    Velotta, Jonathan P.; McCormick, Stephen; Schultz, Eric T.

    2015-01-01

    Adaptation to freshwater may be expected to reduce performance in seawater because these environments represent opposing selective regimes. We tested for such a trade-off in populations of the Alewife (Alosa pseudoharengus). Alewives are ancestrally anadromous, and multiple populations have been independently restricted to freshwater (landlocked). We conducted salinity challenge experiments, whereby juvenile Alewives from one anadromous and multiple landlocked populations were exposed to freshwater and seawater on acute and acclimation timescales. In response to acute salinity challenge trials, independently derived landlocked populations varied in the degree to which seawater tolerance has been lost. In laboratory-acclimation experiments, landlocked Alewives exhibited improved freshwater tolerance, which was correlated with reductions in seawater tolerance and hypo-osmotic balance, suggesting that trade-offs in osmoregulation may be associated with local adaptation to freshwater. We detected differentiation between life-history forms in the expression of an ion-uptake gene (NHE3), and in gill Na+/K+-ATPase activity. Trade-offs in osmoregulation, therefore, may be mediated by differentiation in ion-uptake and salt-secreting pathways.

  17. Sentinel-1 EPS Architecture And Power Conversion Trade-Off

    NASA Astrophysics Data System (ADS)

    Catalano, Toni Fabio; Costanitini, Stefano; Daparati, Giorgio

    2011-10-01

    The paper will present the selected EPS (Electrical Power System) Architecture for the Sentinel-1 mission. After a brief survey of Sentinel-1 mission, the EPS design will be illustrated, with particular focus on the architecture adopted for SAW (Solar Array Wing) power conversion and relevant trade-off. In the early phase of the project, various trade-offs have been carried out in order to define the suitable Sentinel- 1 EPS architecture. Mainly the following subjects have been exploited: -BTA (Battery) technology and topology identification; -SAW rotation strategy and relevant mechanism selection; -primary power bus voltage selection; - distribution and protection philosophy; -SAW power conditioning strategy. All those, and many minor ones, have been evaluated singly to assess the best solution for the individual problem and all together to evaluate the consequences of the interactions at subsystem level to be finally reflected in system budget and architecture sizing. As the choice of the most appropriate conditioning architecture is directly influenced by chosen EPS architecture and has direct impact on S/C (Spacecraft) capability to sustain required operational profile, specially considering the long mission lifetime plus mission extension, dedicated analysis and simulations have been carried out. This paper focuses on SAW conditioning trade-off analysis results along with a brief description of the in- house developed simulator used during this study. Basing on project inputs such as mission operational scenarios, system requirement and HW constraints, a direct comparison of the performances achievable with the different accounted conditioning systems, S3R, MPPT buck and MPPT boost, is given. Finally, the outcomes of simulations run lead to a substantial equivalence of the three architecture topologies if no specific BTA configuration is accounted (ideal configuration). When considering different BTA topologies (s-p or p-s) and related possible failures, a

  18. A safety vs efficiency trade-off identified in the hydraulic pathway of grass leaves is decoupled from photosynthesis, stomatal conductance and precipitation.

    PubMed

    Ocheltree, Troy W; Nippert, Jesse B; Prasad, P V Vara

    2016-04-01

    A common theme in plant physiological research is the trade-off between stress tolerance and growth; an example of this trade-off at the tissue level is the safety vs efficiency hypothesis, which suggests that plants with the greatest resistance to hydraulic failure should have low maximum hydraulic conductance. Here, we quantified the leaf-level drought tolerance of nine C4 grasses as the leaf water potential at which plants lost 50% (P50 × RR ) of maximum leaf hydraulic conductance (Ksat ), and compared this trait with other leaf-level and whole-plant functions. We found a clear trade-off between Ksat and P50 × RR when Ksat was normalized by leaf area and mass (P = 0.05 and 0.01, respectively). However, no trade-off existed between P50 × RR and gas-exchange rates; rather, there was a positive relationship between P50 × RR and photosynthesis (P = 0.08). P50 × RR was not correlated with species distributions based on precipitation (P = 0.70), but was correlated with temperature during the wettest quarter of the year (P < 0.01). These results suggest a trade-off between safety and efficiency in the hydraulic system of grass leaves, which can be decoupled from other leaf-level functions. The unique physiology of C4 plants and adaptations to pulse-driven systems may provide mechanisms that could decouple hydraulic conductance from other plant functions.

  19. Evaluating taboo trade-offs in ecosystems services and human well-being

    PubMed Central

    Coulthard, Sarah; Cheung, William W. L.; Brown, Katrina; Abunge, Caroline; Galafassi, Diego; Peterson, Garry D.; McClanahan, Tim R.; Omukoto, Johnstone O.; Munyi, Lydiah

    2015-01-01

    Managing ecosystems for multiple ecosystem services and balancing the well-being of diverse stakeholders involves different kinds of trade-offs. Often trade-offs involve noneconomic and difficult-to-evaluate values, such as cultural identity, employment, the well-being of poor people, or particular species or ecosystem structures. Although trade-offs need to be considered for successful environmental management, they are often overlooked in favor of win-wins. Management and policy decisions demand approaches that can explicitly acknowledge and evaluate diverse trade-offs. We identified a diversity of apparent trade-offs in a small-scale tropical fishery when ecological simulations were integrated with participatory assessments of social–ecological system structure and stakeholders’ well-being. Despite an apparent win-win between conservation and profitability at the aggregate scale, food production, employment, and well-being of marginalized stakeholders were differentially influenced by management decisions leading to trade-offs. Some of these trade-offs were suggested to be “taboo” trade-offs between morally incommensurable values, such as between profits and the well-being of marginalized women. These were not previously recognized as management issues. Stakeholders explored and deliberated over trade-offs supported by an interactive “toy model” representing key system trade-offs, alongside qualitative narrative scenarios of the future. The concept of taboo trade-offs suggests that psychological bias and social sensitivity may exclude key issues from decision making, which can result in policies that are difficult to implement. Our participatory modeling and scenarios approach has the potential to increase awareness of such trade-offs, promote discussion of what is acceptable, and potentially identify and reduce obstacles to management compliance. PMID:26038547

  20. Evaluating taboo trade-offs in ecosystems services and human well-being.

    PubMed

    Daw, Tim M; Coulthard, Sarah; Cheung, William W L; Brown, Katrina; Abunge, Caroline; Galafassi, Diego; Peterson, Garry D; McClanahan, Tim R; Omukoto, Johnstone O; Munyi, Lydiah

    2015-06-02

    Managing ecosystems for multiple ecosystem services and balancing the well-being of diverse stakeholders involves different kinds of trade-offs. Often trade-offs involve noneconomic and difficult-to-evaluate values, such as cultural identity, employment, the well-being of poor people, or particular species or ecosystem structures. Although trade-offs need to be considered for successful environmental management, they are often overlooked in favor of win-wins. Management and policy decisions demand approaches that can explicitly acknowledge and evaluate diverse trade-offs. We identified a diversity of apparent trade-offs in a small-scale tropical fishery when ecological simulations were integrated with participatory assessments of social-ecological system structure and stakeholders' well-being. Despite an apparent win-win between conservation and profitability at the aggregate scale, food production, employment, and well-being of marginalized stakeholders were differentially influenced by management decisions leading to trade-offs. Some of these trade-offs were suggested to be "taboo" trade-offs between morally incommensurable values, such as between profits and the well-being of marginalized women. These were not previously recognized as management issues. Stakeholders explored and deliberated over trade-offs supported by an interactive "toy model" representing key system trade-offs, alongside qualitative narrative scenarios of the future. The concept of taboo trade-offs suggests that psychological bias and social sensitivity may exclude key issues from decision making, which can result in policies that are difficult to implement. Our participatory modeling and scenarios approach has the potential to increase awareness of such trade-offs, promote discussion of what is acceptable, and potentially identify and reduce obstacles to management compliance.

  1. Evidence of trade-offs shaping virulence evolution in an emerging wildlife pathogen.

    PubMed

    Williams, P D; Dobson, A P; Dhondt, K V; Hawley, D M; Dhondt, A A

    2014-06-01

    In the mid-1990s, the common poultry pathogen Mycoplasma gallisepticum (MG) made a successful species jump to the eastern North American house finch Haemorhous mexicanus (HM). Subsequent strain diversification allows us to directly quantify, in an experimental setting, the transmission dynamics of three sequentially emergent geographic isolates of MG, which differ in the levels of pathogen load they induce. We find significant among-strain variation in rates of transmission as well as recovery. Pathogen strains also differ in their induction of host morbidity, measured as the severity of eye lesions due to infection. Relationships between pathogen traits are also investigated, with transmission and recovery rates being significantly negatively correlated, whereas transmission and virulence, measured as average eye lesion score over the course of infection, are positively correlated. By quantifying these disease-relevant parameters and their relationships, we provide the first analysis of the trade-offs that shape the evolution of this important emerging pathogen.

  2. Trade-off study of data storage technologies

    NASA Technical Reports Server (NTRS)

    Kadyszewski, R. V.

    1977-01-01

    The need to store and retrieve large quantities of data at modest cost has generated the need for an economical, compact, archival mass storage system. Very significant improvements in the state-of-the-art of mass storage systems have been accomplished through the development of a number of magnetic, electro-optical, and other related devices. This study was conducted in order to do a trade-off between these data storage devices and the related technologies in order to determine an optimum approach for an archival mass data storage system based upon a comparison of the projected capabilities and characteristics of these devices to yield operational systems in the early 1980's.

  3. Synergies and trade-offs in achieving global biodiversity targets.

    PubMed

    Di Marco, Moreno; Butchart, Stuart H M; Visconti, Piero; Buchanan, Graeme M; Ficetola, Gentile F; Rondinini, Carlo

    2016-02-01

    After their failure to achieve a significant reduction in the global rate of biodiversity loss by 2010, world governments adopted 20 new ambitious Aichi biodiversity targets to be met by 2020. Efforts to achieve one particular target can contribute to achieving others, but different targets may sometimes require conflicting solutions. Consequently, lack of strategic thinking might result, once again, in a failure to achieve global commitments to biodiversity conservation. We illustrate this dilemma by focusing on Aichi Target 11. This target requires an expansion of terrestrial protected area coverage, which could also contribute to reducing the loss of natural habitats (Target 5), reducing human-induced species decline and extinction (Target 12), and maintaining global carbon stocks (Target 15). We considered the potential impact of expanding protected areas to mitigate global deforestation and the consequences for the distribution of suitable habitat for >10,000 species of forest vertebrates (amphibians, birds, and mammals). We first identified places where deforestation might have the highest impact on remaining forests and then identified places where deforestation might have the highest impact on forest vertebrates (considering aggregate suitable habitat for species). Expanding protected areas toward locations with the highest deforestation rates (Target 5) or the highest potential loss of aggregate species' suitable habitat (Target 12) resulted in partially different protected area network configurations (overlapping with each other by about 73%). Moreover, the latter approach contributed to safeguarding about 30% more global carbon stocks than the former. Further investigation of synergies and trade-offs between targets would shed light on these and other complex interactions, such as the interaction between reducing overexploitation of natural resources (Targets 6, 7), controlling invasive alien species (Target 9), and preventing extinctions of native

  4. Performance trade-offs in in situ chemostat NMR.

    PubMed

    Castro, C D; Koretsky, A P; Domach, M M

    1999-01-01

    Investigating cell cultures with NMR requires high cell densities to provide adequate signal-to-noise, or scans must be summed over long time periods and short-term events are lost. The mixing within a chemostat can be used to shorten the time required to acquire informative in situ NMR spectra from cell cultures. However, performance trade-offs can occur between net signal, spectral resolution, and oxygenation due to sampling volume, conductivity, gas bubble, and fluid flow effects. These trade-offs and the effect of different mixing regimes were theoretically analyzed to quantify how device design decisions impact performance. The results were found to concur with data from cell-free NMR experiments performed in 18 mS/cm conductivity medium. The results also guided the redesign of an NMR bioreactor in terms of relative radio frequency (rf) coil and sample dimensions and other factors. The design, which entails using chemostat mixing to shunt sample through a rf coil in ca. 0.4 s, provides adequate oxygenation for the 4-16% (v/v) cell suspensions examined. Gains realized include lower conductive losses, better magnetic field homogeneity, and the exclusion of gas bubbles from the sampling zone. These gains enable the acquistion of spectra from dilute (3-4% v/v) Saccharomyces cerevisiae chemostat cultures in 6.9 min with high resolution in both the orthophosphate and the beta-NTP regions. Samples with 16% (v/v) cells also yield useful spectra within 0.5-1.0 min.

  5. Geographic biotype and host-associated local adaptation in a polyphagous species, Lambdina fiscellaria (Lepidoptera: Geometridae) feeding on balsam fir on Anticosti Island, Canada.

    PubMed

    Hébert, C; Berthiaume, R; Bauce, E; Brodeur, J

    2006-12-01

    The debate about mechanisms underlying the evolution of host specialization by herbivorous insects remains open. Natural selection may act locally and lead to different patterns of geographic variation in life history traits of polyphagous herbivores. The hypothesis of genetically-based trade-offs in offspring performance on different hosts has been proposed but this has rarely been demonstrated. Under laboratory conditions, the biological performance of two populations of the hemlock looper Lambdina fiscellaria (Guenée), a highly polyphagous lepidopteran, was compared when reared on three different tree host species: balsam fir, eastern hemlock and sugar maple. One population originated from Anticosti Island, Québec, Canada, where the insect has evolved without having access to two of the three tree species tested, the other being from the mainland where all tree species are present. When reared on balsam fir foliage, which was naturally available to each population, larvae from Anticosti Island underwent four instars compared with five for the mainland population, indicating the existence of geographic biotypes in L. fiscellaria. When reared on the foliage of non-naturally available host trees, larvae from Anticosti Island had a higher incidence of supernumerary instars. This is a unique example where local adaptation to environmental conditions of an insect herbivore is expressed through a differential number of larval instars. Moreover, the Anticosti Island population showed a higher growth related index on the host available to both populations indicating that a fitness trade-off was the evolutionary process underlying the local adaptation of this population on balsam fir.

  6. Host adaptive immunity alters gut microbiota.

    PubMed

    Zhang, Husen; Sparks, Joshua B; Karyala, Saikumar V; Settlage, Robert; Luo, Xin M

    2015-03-01

    It has long been recognized that the mammalian gut microbiota has a role in the development and activation of the host immune system. Much less is known on how host immunity regulates the gut microbiota. Here we investigated the role of adaptive immunity on the mouse distal gut microbial composition by sequencing 16 S rRNA genes from microbiota of immunodeficient Rag1(-/-) mice, versus wild-type mice, under the same housing environment. To detect possible interactions among immunological status, age and variability from anatomical sites, we analyzed samples from the cecum, colon, colonic mucus and feces before and after weaning. High-throughput sequencing showed that Firmicutes, Bacteroidetes and Verrucomicrobia dominated mouse gut bacterial communities. Rag1(-) mice had a distinct microbiota that was phylogenetically different from wild-type mice. In particular, the bacterium Akkermansia muciniphila was highly enriched in Rag1(-/-) mice compared with the wild type. This enrichment was suppressed when Rag1(-/-) mice received bone marrows from wild-type mice. The microbial community diversity increased with age, albeit the magnitude depended on Rag1 status. In addition, Rag1(-/-) mice had a higher gain in microbiota richness and evenness with increase in age compared with wild-type mice, possibly due to the lack of pressure from the adaptive immune system. Our results suggest that adaptive immunity has a pervasive role in regulating gut microbiota's composition and diversity.

  7. Reproductive effort and the egg number vs. size trade-off in Physalaemus frogs (Anura: Leiuperidae)

    NASA Astrophysics Data System (ADS)

    Camargo, Arley; Sarroca, Macarena; Maneyro, Raúl

    2008-09-01

    Patterns of reproductive allocation are expected to differ between species according to temporally and spatially variable costs of reproduction. Even when reproductive allocation patterns are the same, species can also differ in how the reproductive effort is allocated between offspring number and size. In this study, we compared the reproductive allocation patterns and the offspring number vs. size trade-off in two frog species, Physalaemus biligonigerus and P. gracilis, using bivariate (standardized major axis) and multiple linear regressions. Both species showed a common slope between body size and reproductive effort and thus a similar allocation pattern although P. biligonigerus has a larger body size (shift along common slope) and makes a lower reproductive effort (shift in intercept) than P. gracilis. We suggest that similar allocation patterns may be related to the shared phenologies of these frogs and that the differences in reproductive effort could represent either an adaptive shift (e.g., change in body space for the clutch) or a historical constraint. There was a negative correlation between fecundity and egg size in P. biligonigerus but not in P. gracilis as predicted by the acquisition-allocation model (Y-model). This study constitutes the first valid test of the Y-model based on recent predictions derived for the trade-off between offspring size vs. number. We conclude that future studies should compare reproductive allocation patterns between species using tests of allometric slopes with appropriate phylogenetic control to detect both adaptive shifts in allocation strategies and correlations with other life-history traits.

  8. Local orientation and the evolution of foraging: changes in decision making can eliminate evolutionary trade-offs.

    PubMed

    van der Post, Daniel J; Semmann, Dirk

    2011-10-01

    Information processing is a major aspect of the evolution of animal behavior. In foraging, responsiveness to local feeding opportunities can generate patterns of behavior which reflect or "recognize patterns" in the environment beyond the perception of individuals. Theory on the evolution of behavior generally neglects such opportunity-based adaptation. Using a spatial individual-based model we study the role of opportunity-based adaptation in the evolution of foraging, and how it depends on local decision making. We compare two model variants which differ in the individual decision making that can evolve (restricted and extended model), and study the evolution of simple foraging behavior in environments where food is distributed either uniformly or in patches. We find that opportunity-based adaptation and the pattern recognition it generates, plays an important role in foraging success, particularly in patchy environments where one of the main challenges is "staying in patches". In the restricted model this is achieved by genetic adaptation of move and search behavior, in light of a trade-off on within- and between-patch behavior. In the extended model this trade-off does not arise because decision making capabilities allow for differentiated behavioral patterns. As a consequence, it becomes possible for properties of movement to be specialized for detection of patches with more food, a larger scale information processing not present in the restricted model. Our results show that changes in decision making abilities can alter what kinds of pattern recognition are possible, eliminate an evolutionary trade-off and change the adaptive landscape.

  9. Robustness trade-offs and host–microbial symbiosis in the immune system

    PubMed Central

    Kitano, Hiroaki; Oda, Kanae

    2006-01-01

    The immune system provides organisms with robustness against pathogen threats, yet it also often adversely affects the organism as in autoimmune diseases. Recently, the molecular interactions involved in the immune system have been uncovered. At the same time, the role of the bacterial flora and its interactions with the host immune system have been identified. In this article, we try to reconcile these findings to draw a consistent picture of the host defense system. Specifically, we first argue that the network of molecular interactions involved in immune functions has a bow-tie architecture that entails inherent trade-offs among robustness, fragility, resource limitation, and performance. Second, we discuss the possibility that commensal bacteria and the host immune system constitute an integrated defense system. This symbiotic association has evolved to optimize its robustness against pathogen attacks and nutrient perturbations by harboring a broad range of microorganisms. Owing to the inherent propensity of a host immune system toward hyperactivity, maintenance of bacterial flora homeostasis might be particularly important in the development of preventive strategies against immune disorders such as autoimmune diseases. PMID:16738567

  10. Energy-Information Trade-Offs between Movement and Sensing

    PubMed Central

    MacIver, Malcolm A.; Patankar, Neelesh A.; Shirgaonkar, Anup A.

    2010-01-01

    While there is accumulating evidence for the importance of the metabolic cost of information in sensory systems, how these costs are traded-off with movement when sensing is closely linked to movement is poorly understood. For example, if an animal needs to search a given amount of space beyond the range of its vision system, is it better to evolve a higher acuity visual system, or evolve a body movement system that can more rapidly move the body over that space? How is this trade-off dependent upon the three-dimensional shape of the field of sensory sensitivity (hereafter, sensorium)? How is it dependent upon sensorium mobility, either through rotation of the sensorium via muscles at the base of the sense organ (e.g., eye or pinna muscles) or neck rotation, or by whole body movement through space? Here we show that in an aquatic model system, the electric fish, a choice to swim in a more inefficient manner during prey search results in a higher prey encounter rate due to better sensory performance. The increase in prey encounter rate more than counterbalances the additional energy expended in swimming inefficiently. The reduction of swimming efficiency for improved sensing arises because positioning the sensory receptor surface to scan more space per unit time results in an increase in the area of the body pushing through the fluid, increasing wasteful body drag forces. We show that the improvement in sensory performance that occurs with the costly repositioning of the body depends upon having an elongated sensorium shape. Finally, we show that if the fish was able to reorient their sensorium independent of body movement, as fish with movable eyes can, there would be significant energy savings. This provides insight into the ubiquity of sensory organ mobility in animal design. This study exposes important links between the morphology of the sensorium, sensorium mobility, and behavioral strategy for maximally extracting energy from the environment. An

  11. Optimization based trade-off analysis of biodiesel crop production for managing a German agricultural catchment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In agricultural production, the existence of multiple trade-offs among several conflicting objectives, such as food production, water quantity, water quality, biodiversity and ecosystem services, is well known. However, quantification of the trade-offs among objectives in bioenergy crop production i...

  12. Spatial Resolution, Grayscale, and Error Diffusion Trade-offs: Impact on Display System Design

    NASA Technical Reports Server (NTRS)

    Gille, Jennifer L. (Principal Investigator)

    1996-01-01

    We examine technology trade-offs related to grayscale resolution, spatial resolution, and error diffusion for tessellated display systems. We present new empirical results from our psychophysical study of these trade-offs and compare them to the predictions of a model of human vision.

  13. 76 FR 70408 - Information Collection; Understanding Value Trade-Offs Regarding Fire Hazard Reduction Programs...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-14

    ... Forest Service Information Collection; Understanding Value Trade-Offs Regarding Fire Hazard Reduction... approved information collection, Understanding Value Trade-offs Regarding Fire Hazard Reduction Programs in...-offs Regarding Fire Hazard Reduction Programs in the Wildland-Urban Interface. OMB Number:...

  14. The effect of cognitive reappraisal on the emotional memory trade-off.

    PubMed

    Steinberger, Allie; Payne, Jessica D; Kensinger, Elizabeth A

    2011-11-01

    Emotional information is often remembered better than neutral information, but this enhancement can come at the cost of memory for non-emotional stimuli presented alongside emotionally salient items. Two encoding-related factors have been proposed to influence the magnitude of this trade-off: The intensity of the affective response to the scenes (which increases the trade-off) and the cognitive control exerted to process the scenes (which decreases the trade-off). The present study examined the relative importance of these two factors by assessing the effect of cognitive reappraisal on the magnitude of the trade-off effect. Cognitive reappraisal refers to the implementation of cognitive strategies to assist a person in changing the intensity of their response to an experience. Thus, reappraisal provides a way to assess both of the factors that are important for the elicitation of the trade-off. The results revealed that when participants were asked to view the scenes, without cognitive reappraisal, a robust memory trade-off occurred. But, when participants were asked to either heighten or decrease their emotional reactions via reappraisal, there was a reduction in the magnitude of the trade-off. These results suggest that the cognitive process of reappraising the scenes is sufficient to reduce the trade-off effect, even when such processing leads to an intensified affective response.

  15. The Lotka-Volterra predator-prey model with foraging-predation risk trade-offs.

    PubMed

    Krivan, Vlastimil

    2007-11-01

    This article studies the effects of adaptive changes in predator and/or prey activities on the Lotka-Volterra predator-prey population dynamics. The model assumes the classical foraging-predation risk trade-offs: increased activity increases population growth rate, but it also increases mortality rate. The model considers three scenarios: prey only are adaptive, predators only are adaptive, and both species are adaptive. Under all these scenarios, the neutral stability of the classical Lotka-Volterra model is partially lost because the amplitude of maximum oscillation in species numbers is bounded, and the bound is independent of the initial population numbers. Moreover, if both prey and predators behave adaptively, the neutral stability can be completely lost, and a globally stable equilibrium would appear. This is because prey and/or predator switching leads to a piecewise constant prey (predator) isocline with a vertical (horizontal) part that limits the amplitude of oscillations in prey and predator numbers, exactly as suggested by Rosenzweig and MacArthur in their seminal work on graphical stability analysis of predator-prey systems. Prey and predator activities in a long-term run are calculated explicitly. This article shows that predictions based on short-term behavioral experiments may not correspond to long-term predictions when population dynamics are considered.

  16. Constraints on muscular performance: trade-offs between power output and fatigue resistance.

    PubMed Central

    Wilson, Robbie S; James, Rob S

    2004-01-01

    An important functional and evolutionary constraint on the physical performance of vertebrates is believed to be the trade-off between speed and endurance capacity. However, despite the pervasiveness of physiological arguments, most studies have found no evidence of the trade-off when tested at the whole-animal level. We investigated the existence of this trade-off at the whole-muscle level, the presumed site of this physiological conflict, by examining inter-individual variation in both maximum power output and fatigue resistance for mouse extensor digitorum longus (EDL) muscle using the work-loop technique. We found negative correlations between several measures of in vitro maximum power output and force production with fatigue resistance for individual mouse EDL muscles, indicating functional trade-offs between these performance parameters. We suggest that this trade-off detected at the whole-muscle level has imposed an important constraint on the evolution of vertebrate physical performance. PMID:15252990

  17. Evidence for a trade-off between early growth and tooth wear in Svalbard reindeer.

    PubMed

    Veiberg, Vebjørn; Mysterud, Atle; Bjørkvoll, Eirin; Langvatn, Rolf; Loe, Leif Egil; Irvine, R Justin; Bonenfant, Christophe; Couweleers, Fred; Stenseth, Nils Chr

    2007-11-01

    Ruminants depend on efficient physical degradation of forage through chewing to increase the surface area of the food particles presented to the microflora. Fossil evidence suggests that increased molar height is an adaptation for wear tolerance in dry ecosystems with sparse vegetation, but no study has shown selection pressure for hypsodonty in contemporary ruminants. We explored the relationships between particle size in rumen, tooth wear (scanned molar occlusal topography), age and body mass of female Svalbard reindeer living in an arctic desert at 78 degrees latitude on Svalbard. We predicted that (H1) if the rumen particle size is determined mainly by constraints due to tooth wear, and if tooth wear is mainly a function of age, average particle size in rumen should increase with age. From allometric relations it is known that larger individuals can survive on a lower-quality diet, we therefore predicted (H2) larger particle sizes with increases in (ln) body mass, irrespective of age and wear. Lastly, if there is a trade-off between growth and tooth wear in dry ecosystems (a selection pressure for hypsodonty), we predicted (H3) that teeth of heavier animals should be more worn than those of lighter animals of the same age. The proportion of small particles (<1.0 mm) decreased rapidly with increasing age (consistent with H1). Heavier females within an age class had more worn teeth (consistent with H3) than lighter ones. A close-to-isometric relationship between particle size and body mass suggested that heavier animals partly compensated for reduced tooth efficiency by chewing more. We provide the first evidence of a trade-off between fast early growth and wear (a somatic cost) of a senescence-related trait--the structure and height of the molar--in a wild ruminant inhabiting an arctic desert where selection pressure for increased tooth height is expected. This suggests that foraging conditions are more extreme than the environment in which the species

  18. Egg number-egg size: an important trade-off in parasite life history strategies.

    PubMed

    Cavaleiro, Francisca I; Santos, Maria J

    2014-03-01

    Parasites produce from just a few to many eggs of variable size, but our understanding of the factors driving variation in these two life history traits at the intraspecific level is still very fragmentary. This study evaluates the importance of performing multilevel analyses on egg number and egg size, while characterising parasite life history strategies. A total of 120 ovigerous females of Octopicola superba (Copepoda: Octopicolidae) (one sample (n=30) per season) were characterised with respect to different body dimensions (total length; genital somite length) and measures of reproductive effort (fecundity; mean egg diameter; total reproductive effort; mean egg sac length). While endoparasites are suggested to follow both an r- and K-strategy simultaneously, the evidence found in this and other studies suggests that environmental conditions force ectoparasites into one of the two alternatives. The positive and negative skewness of the distributions of fecundity and mean egg diameter, respectively, suggest that O. superba is mainly a K-strategist (i.e. produces a relatively small number of large, well provisioned eggs). Significant sample differences were recorded concomitantly for all body dimensions and measures of reproductive effort, while a general linear model detected a significant influence of season*parasite total length in both egg number and size. This evidence suggests adaptive phenotypic plasticity in body dimensions and size-mediated changes in egg production. Seasonal changes in partitioning of resources between egg number and size resulted in significant differences in egg sac length but not in total reproductive effort. Evidence for a trade-off between egg number and size was found while controlling for a potential confounding effect of parasite total length. However, this trade-off became apparent only at high fecundity levels, suggesting a state of physiological exhaustion.

  19. Eco-evolutionary dynamics in a coevolving host-virus system.

    PubMed

    Frickel, Jens; Sieber, Michael; Becks, Lutz

    2016-04-01

    Eco-evolutionary dynamics have been shown to be important for understanding population and community stability and their adaptive potential. However, coevolution in the framework of eco-evolutionary theory has not been addressed directly. Combining experiments with an algal host and its viral parasite, and mathematical model analyses we show eco-evolutionary dynamics in antagonistic coevolving populations. The interaction between antagonists initially resulted in arms race dynamics (ARD) with selective sweeps, causing oscillating host-virus population dynamics. However, ARD ended and populations stabilised after the evolution of a general resistant host, whereas a trade-off between host resistance and growth then maintained host diversity over time (trade-off driven dynamics). Most importantly, our study shows that the interaction between ecology and evolution had important consequences for the predictability of the mode and tempo of adaptive change and for the stability and adaptive potential of populations.

  20. Air quality and climate--synergies and trade-offs.

    PubMed

    von Schneidemesser, Erika; Monks, Paul S

    2013-07-01

    Air quality and climate are often treated as separate science and policy areas. Air quality encompasses the here-and-now of pollutant emissions, atmospheric transformations and their direct effect on human and ecosystem health. Climate change deals with the drivers leading to a warmer world and the consequences of that. These two science and policy issues are inexorably linked via common pollutants, such as ozone (methane) and black carbon. This short review looks at the new scientific evidence around so-called "short-lived climate forcers" and the growing realisation that a way to meet short-term climate change targets may be through the control of "air quality" pollutants. None of the options discussed here can replace reduction of long-lived greenhouse gases, such as CO2, which is required for any long-term climate change mitigation strategy. An overview is given of the underlying science, remaining uncertainties, and some of the synergies and trade-offs for addressing air quality and climate in the science and policy context.

  1. Cadmium Protection Strategies—A Hidden Trade-Off?

    PubMed Central

    Sandbichler, Adolf Michael; Höckner, Martina

    2016-01-01

    Cadmium (Cd) is a non-essential transition metal which is introduced into the biosphere by various anthropogenic activities. Environmental pollution with Cd poses a major health risk and Cd toxicity has been extensively researched over the past decades. This review aims at changing the perspective by discussing protection mechanisms available to counteract a Cd insult. Antioxidants, induction of antioxidant enzymes, and complexation of Cd to glutathione (GSH) and metallothionein (MT) are the most potent protective measures to cope with Cd-induced oxidative stress. Furthermore, protection mechanisms include prevention of endoplasmic reticulum (ER) stress, mitophagy and metabolic stress, as well as expression of chaperones. Pre-exposure to Cd itself, or co-exposure to other metals or trace elements can improve viability under Cd exposure and cells have means to reduce Cd uptake and improve Cd removal. Finally, environmental factors have negative or positive effects on Cd toxicity. Most protection mechanisms aim at preventing cellular damage. However, this might not be possible without trade-offs like an increased risk of carcinogenesis. PMID:26805823

  2. Performance trade-offs in the flight initiation of Drosophila.

    PubMed

    Card, Gwyneth; Dickinson, Michael

    2008-02-01

    The fruit fly Drosophila melanogaster performs at least two distinct types of flight initiation. One kind is a stereotyped escape response to a visual stimulus that is mediated by the hard-wired giant fiber neural pathway, and the other is a more variable ;voluntary' response that can be performed without giant fiber activation. Because the simpler escape take-offs are apparently successful, it is unclear why the fly has multiple pathways to coordinate flight initiation. In this study we use high-speed videography to observe flight initiation in unrestrained wild-type flies and assess the flight performance of each of the two types of take-off. Three-dimensional kinematic analysis of take-off sequences indicates that wing use during the jumping phase of flight initiation is essential for stabilizing flight. During voluntary take-offs, early wing elevation leads to a slower and more stable take-off. In contrast, during visually elicited escapes, the wings are pulled down close to the body during take-off, resulting in tumbling flights in which the fly translates faster but also rotates rapidly about all three of its body axes. Additionally, we find evidence that the power delivered by the legs is substantially greater during visually elicited escapes than during voluntary take-offs. Thus, we find that the two types of Drosophila flight initiation result in different flight performances once the fly is airborne, and that these performances are distinguished by a trade-off between speed and stability.

  3. Trade-offs in antibody repertoires to complex antigens

    PubMed Central

    Childs, Lauren M.; Baskerville, Edward B.; Cobey, Sarah

    2015-01-01

    Pathogens vary in their antigenic complexity. While some pathogens such as measles present a few relatively invariant targets to the immune system, others such as malaria display considerable antigenic diversity. How the immune response copes in the presence of multiple antigens, and whether a trade-off exists between the breadth and efficacy of antibody (Ab)-mediated immune responses, are unsolved problems. We present a theoretical model of affinity maturation of B-cell receptors (BCRs) during a primary infection and examine how variation in the number of accessible antigenic sites alters the Ab repertoire. Naive B cells with randomly generated receptor sequences initiate the germinal centre (GC) reaction. The binding affinity of a BCR to an antigen is quantified via a genotype–phenotype map, based on a random energy landscape, that combines local and distant interactions between residues. In the presence of numerous antigens or epitopes, B-cell clones with different specificities compete for stimulation during rounds of mutation within GCs. We find that the availability of many epitopes reduces the affinity and relative breadth of the Ab repertoire. Despite the stochasticity of somatic hypermutation, patterns of immunodominance are strongly shaped by chance selection of naive B cells with specificities for particular epitopes. Our model provides a mechanistic basis for the diversity of Ab repertoires and the evolutionary advantage of antigenically complex pathogens. PMID:26194759

  4. Trade-offs in antibody repertoires to complex antigens.

    PubMed

    Childs, Lauren M; Baskerville, Edward B; Cobey, Sarah

    2015-09-05

    Pathogens vary in their antigenic complexity. While some pathogens such as measles present a few relatively invariant targets to the immune system, others such as malaria display considerable antigenic diversity. How the immune response copes in the presence of multiple antigens, and whether a trade-off exists between the breadth and efficacy of antibody (Ab)-mediated immune responses, are unsolved problems. We present a theoretical model of affinity maturation of B-cell receptors (BCRs) during a primary infection and examine how variation in the number of accessible antigenic sites alters the Ab repertoire. Naive B cells with randomly generated receptor sequences initiate the germinal centre (GC) reaction. The binding affinity of a BCR to an antigen is quantified via a genotype-phenotype map, based on a random energy landscape, that combines local and distant interactions between residues. In the presence of numerous antigens or epitopes, B-cell clones with different specificities compete for stimulation during rounds of mutation within GCs. We find that the availability of many epitopes reduces the affinity and relative breadth of the Ab repertoire. Despite the stochasticity of somatic hypermutation, patterns of immunodominance are strongly shaped by chance selection of naive B cells with specificities for particular epitopes. Our model provides a mechanistic basis for the diversity of Ab repertoires and the evolutionary advantage of antigenically complex pathogens.

  5. Product life trade-offs: what if products fail early?

    PubMed

    Skelton, Alexandra C H; Allwood, Julian M

    2013-02-05

    Increasing product life allows the embodied emissions in products to be spread across a longer period but can mean that opportunities to improve use-phase efficiency are foregone. In this paper, a model that evaluates this trade-off is presented and used to estimate the optimal product life for a range of metal-intensive products. Two strategies that have potential to save emissions are explored: (1) adding extra embodied emissions to make products more sturdy, increasing product life, and (2) increasing frequency of use, causing early product failure to take advantage of improvements in use-phase efficiency. These strategies are evaluated for two specific case studies (long-life washing machines and more frequent use of vehicles through car clubs) and for a range of embodied and use-phase intensive products under different use-phase improvement rate assumptions. Particular emphasis is placed on the fact that products often fail neither at their design life nor at their optimal life. Policy recommendations are then made regarding the targeting of these strategies according to product characteristics and the timing of typical product failure relative to optimal product life.

  6. Time trade-off: one methodology, different methods.

    PubMed

    Attema, Arthur E; Edelaar-Peeters, Yvette; Versteegh, Matthijs M; Stolk, Elly A

    2013-07-01

    There is no scientific consensus on the optimal specification of the time trade-off (TTO) task. As a consequence, studies using TTO to value health states may share the core element of trading length of life for quality of life, but can differ considerably on many other elements. While this pluriformity in specifications advances the understanding of TTO from a methodological point of view, it also results in incomparable health state values. Health state values are applied in health technology assessments, and in that context comparability of information is desired. In this article, we discuss several alternative specifications of TTO presented in the literature. The defining elements of these specifications are identified as being either methodological, procedural or analytical in nature. Where possible, it is indicated how these elements affect health state values (i.e., upward or downward). Finally, a checklist for TTO studies is presented, which incorporates a list of choices to be made by researchers who wish to perform a TTO task. Such a checklist enables other researchers to align methodologies in order to enhance the comparability of health state values.

  7. Anthrax Sampling and Decontamination: Technology Trade-Offs

    SciTech Connect

    Price, Phillip N.; Hamachi, Kristina; McWilliams, Jennifer; Sohn, Michael D.

    2008-09-12

    The goal of this project was to answer the following questions concerning response to a future anthrax release (or suspected release) in a building: 1. Based on past experience, what rules of thumb can be determined concerning: (a) the amount of sampling that may be needed to determine the extent of contamination within a given building; (b) what portions of a building should be sampled; (c) the cost per square foot to decontaminate a given type of building using a given method; (d) the time required to prepare for, and perform, decontamination; (e) the effectiveness of a given decontamination method in a given type of building? 2. Based on past experience, what resources will be spent on evaluating the extent of contamination, performing decontamination, and assessing the effectiveness of the decontamination in abuilding of a given type and size? 3. What are the trade-offs between cost, time, and effectiveness for the various sampling plans, sampling methods, and decontamination methods that have been used in the past?

  8. Reliability, Risk and Cost Trade-Offs for Composite Designs

    NASA Technical Reports Server (NTRS)

    Shiao, Michael C.; Singhal, Surendra N.; Chamis, Christos C.

    1996-01-01

    Risk and cost trade-offs have been simulated using a probabilistic method. The probabilistic method accounts for all naturally-occurring uncertainties including those in constituent material properties, fabrication variables, structure geometry and loading conditions. The probability density function of first buckling load for a set of uncertain variables is computed. The probabilistic sensitivity factors of uncertain variables to the first buckling load is calculated. The reliability-based cost for a composite fuselage panel is defined and minimized with respect to requisite design parameters. The optimization is achieved by solving a system of nonlinear algebraic equations whose coefficients are functions of probabilistic sensitivity factors. With optimum design parameters such as the mean and coefficient of variation (representing range of scatter) of uncertain variables, the most efficient and economical manufacturing procedure can be selected. In this paper, optimum values of the requisite design parameters for a predetermined cost due to failure occurrence are computationally determined. The results for the fuselage panel analysis show that the higher the cost due to failure occurrence, the smaller the optimum coefficient of variation of fiber modulus (design parameter) in longitudinal direction.

  9. Trade-Offs in Delayed Information Transmission in Biochemical Networks

    NASA Astrophysics Data System (ADS)

    Mancini, F.; Marsili, M.; Walczak, A. M.

    2016-03-01

    In order to transmit biochemical signals, biological regulatory systems dissipate energy with concomitant entropy production. Additionally, signaling often takes place in challenging environmental conditions. In a simple model regulatory circuit given by an input and a delayed output, we explore the trade-offs between information transmission and the system's energetic efficiency. We determine the maximally informative network, given a fixed amount of entropy production and a delayed response, exploring both the case with and without feedback. We find that feedback allows the circuit to overcome energy constraints and transmit close to the maximum available information even in the dissipationless limit. Negative feedback loops, characteristic of shock responses, are optimal at high dissipation. Close to equilibrium positive feedback loops, known for their stability, become more informative. Asking how the signaling network should be constructed to best function in the worst possible environment, rather than an optimally tuned one or in steady state, we discover that at large dissipation the same universal motif is optimal in all of these conditions.

  10. Telomere Length and the Cancer–Atherosclerosis Trade-Off

    PubMed Central

    Stone, Rivka C.; Horvath, Kent; Kark, Jeremy D.; Susser, Ezra; Tishkoff, Sarah A.; Aviv, Abraham

    2016-01-01

    Modern humans, the longest-living terrestrial mammals, display short telomeres and repressed telomerase activity in somatic tissues compared with most short-living small mammals. The dual trait of short telomeres and repressed telomerase might render humans relatively resistant to cancer compared with short-living small mammals. However, the trade-off for cancer resistance is ostensibly increased age-related degenerative diseases, principally in the form of atherosclerosis. In this communication, we discuss (a) the genetics of human telomere length, a highly heritable complex trait that is influenced by genetic ancestry, sex, and paternal age at conception, (b) how cancer might have played a role in the evolution of telomere biology across mammals, (c) evidence that in modern humans telomere length is a determinant (rather than only a biomarker) of cancer and atherosclerosis, and (d) the potential influence of relatively recent evolutionary forces in fashioning the variation in telomere length across and within populations, and their likely lasting impact on major diseases in humans. Finally, we propose venues for future research on human telomere genetics in the context of its potential role in shaping the modern human lifespan. PMID:27386863

  11. Supply-demand equilibria and the size-number trade-off in spatially structured recreational fisheries.

    PubMed

    Wilson, Kyle L; Cantin, Ariane; Ward, Hillary G M; Newton, Eric R; Mee, Jonathan A; Varkey, Divya A; Parkinson, Eric A; Post, John R

    2016-06-01

    Recreational fishing effort varies across complex inland landscapes (e.g., lake-districts) and appears influenced by both angler preferences and qualities of the fishery resource, like fish size and abundance. However, fish size and abundance have an ecological trade-off within a population, thereby structuring equal-quality isopleths expressing this trade-off across the fishing landscape. Since expressed preferences of recreational anglers (i.e., site-selection of high-quality fishing opportunities among many lakes) can be analogous to optimal foraging strategies of natural predators, adopting such concepts can aid in understanding scale-dependence in fish-angler interactions and impacts of fishing across broad landscapes. Here, we assumed a fish supply-angler demand equilibria and adapted a novel bivariate measure of fishing quality based on fish size and catch rates to assess how recreational anglers influence fishing quality among a complex inland landscape. We then applied this metric to evaluate (1) angler preferences for caught and released fish compared to harvested fish, (2) the nonlinear size-numbers trade-off with uncertainty in both traits, and (3) the spatial-scale of the equilibria across 62 lakes and four independent management regions in British Columbia's (BC) rainbow trout Oncorhynchus mykiss fishery. We found anglers had low preference for caught and released fish (~10% of the value compared to harvested fish), which modified anglers' perception of fishing quality. Hence, fishing quality and angler effort was not influenced simply by total fish caught, but largely by harvested fish catch rates. Fishing quality varied from BC's northern regions (larger fish and more abundant) compared to southern regions (smaller fish and less abundant) directly associated with a 2.5 times increase in annual fishing effort in southern regions, suggesting that latent fishing pressure can structure the size-numbers trade-off in rainbow trout populations. The

  12. Evolutionary Trade-Offs Underlie the Multi-faceted Virulence of Staphylococcus aureus

    PubMed Central

    Laabei, Maisem; Uhlemann, Anne-Catrin; Lowy, Franklin D.; Austin, Eloise D.; Yokoyama, Maho; Ouadi, Khadija; Feil, Edward; Thorpe, Harry A.; Williams, Barnabas; Perkins, Mark; Peacock, Sharon J.; Clarke, Stephen R.; Dordel, Janina; Holden, Matthew; Votintseva, Antonina A.; Bowden, Rory; Crook, Derrick W.; Young, Bernadette C.

    2015-01-01

    Bacterial virulence is a multifaceted trait where the interactions between pathogen and host factors affect the severity and outcome of the infection. Toxin secretion is central to the biology of many bacterial pathogens and is widely accepted as playing a crucial role in disease pathology. To understand the relationship between toxicity and bacterial virulence in greater depth, we studied two sequenced collections of the major human pathogen Staphylococcus aureus and found an unexpected inverse correlation between bacterial toxicity and disease severity. By applying a functional genomics approach, we identified several novel toxicity-affecting loci responsible for the wide range in toxic phenotypes observed within these collections. To understand the apparent higher propensity of low toxicity isolates to cause bacteraemia, we performed several functional assays, and our findings suggest that within-host fitness differences between high- and low-toxicity isolates in human serum is a contributing factor. As invasive infections, such as bacteraemia, limit the opportunities for onward transmission, highly toxic strains could gain an additional between-host fitness advantage, potentially contributing to the maintenance of toxicity at the population level. Our results clearly demonstrate how evolutionary trade-offs between toxicity, relative fitness, and transmissibility are critical for understanding the multifaceted nature of bacterial virulence. PMID:26331877

  13. Trade-offs in designing a mobile infrared scene projector

    NASA Astrophysics Data System (ADS)

    Brown, Richard; Lastra, Henry M.; Vuong, Francisca R.; Brooks, Geoffrey W.

    2000-07-01

    Current test and evaluation methods are not adequate for fully assessing the operational performance of imaging infrared sensors while they are installed on the weapon system platform. The use of infrared (IR) scene projection in test and evaluation will augment and redefine test methodologies currently being used to test and evaluate forward looking infrared (FLIR) and imaging IR sensors. The Mobile Infrared Scene Projector (MIRSP) projects accurate, dynamic, and realistic IR imagery into the entrance aperture of the sensor, such that the sensor would perceive and respond to the imagery as it would to the real-world scenario. The MIRSP domain of application includes development, analysis, integration, exploitation, training, and test and evaluation of ground and aviation based imaging IR sensors/subsystems/systems. This applies to FLIR systems, imaging IR missile seekers/guidance sections, as well as non-imaging thermal sensors. The MIRSP Phase I, 'pathfinder' has evolved from other scene projector systems, such as the Flight Motion Simulator Infrared Scene Projector (FIRSP) and the Dynamic Infrared Scene Projector (DIRSP). Both of these projector systems were designed for laboratory test and evaluation use rather than field test and evaluation use. This paper will detail the MIRSP design to include trade-off analysis performed at the system/subsystem levels. The MIRSP Phase II will provide the capability to test and evaluate various electro-optical sensors on weapon platform. The MIRSP Phase I and II will be advancing current IR scene projector technologies by exploring other technologies such as mobility/transportability, packaging, sensors, and scene generation.

  14. Reproduction alters oxidative status when it is traded-off against longevity.

    PubMed

    Beaulieu, Michaël; Geiger, Rina E; Reim, Elisabeth; Zielke, Luisa; Fischer, Klaus

    2015-07-01

    Oxidative stress has been proposed to mediate one of the most important aspects of life-history evolution: the trade-off between reproduction and self-maintenance. However, empirical studies have cast doubt on the generality of this intriguing notion. Here, we hypothesize that reproduction alters oxidative status only when a trade-off between reproduction and self-maintenance occurs. Accordingly, in female Bicyclus anynana butterflies, we found that reproduction affected oxidative markers only under challenging thermal conditions that made the trade-off between reproduction and longevity emerge. Interestingly, under such conditions, butterflies favored longevity over reproduction, suggesting that self-maintenance mechanisms were activated. Accordingly, butterflies reproducing under challenging thermal conditions exhibited enhanced antioxidant defenses and stable oxidative damage. Altogether, our results indicate that a trade-off between reproduction and self-maintenance is indeed a necessary condition for reproduction to alter oxidative status, and that the effects of such a trade-off on oxidative status depend on whether priority is given to self-maintenance or reproduction. Assessing the existence of the trade-off between self-maintenance and reproduction, and whether self-maintenance is prioritized relative to reproduction is therefore crucial for understanding variation in oxidative status in reproducing animals, which may clarify the general implication of oxidative stress in the resolution of life-history trade-offs.

  15. Insights from life history theory for an explicit treatment of trade-offs in conservation biology.

    PubMed

    Charpentier, Anne

    2015-06-01

    As economic and social contexts become more embedded within biodiversity conservation, it becomes obvious that resources are a limiting factor in conservation. This recognition is leading conservation scientists and practitioners to increasingly frame conservation decisions as trade-offs between conflicting societal objectives. However, this framing is all too often done in an intuitive way, rather than by addressing trade-offs explicitly. In contrast, the concept of trade-off is a keystone in evolutionary biology, where it has been investigated extensively. I argue that insights from evolutionary theory can provide methodological and theoretical support to evaluating and quantifying trade-offs in biodiversity conservation. I reviewed the diverse ways in which trade-offs have emerged within the context of conservation and how advances from evolutionary theory can help avoid the main pitfalls of an implicit approach. When studying both evolutionary trade-offs (e.g., reproduction vs. survival) and conservation trade-offs (e.g., biodiversity conservation vs. agriculture), it is crucial to correctly identify the limiting resource, hold constant the amount of this resource when comparing different scenarios, and choose appropriate metrics to quantify the extent to which the objectives have been achieved. Insights from studies in evolutionary theory also reveal how an inadequate selection of conservation solutions may result from considering suboptimal rather than optional solutions when examining whether a trade-off exits between 2 objectives. Furthermore, the shape of a trade-off curve (i.e., whether the relationship between 2 objectives follows a concave, convex, or linear form) is known to affect crucially the definition of optimal solutions in evolutionary biology and very likely affects decisions in biodiversity conservation planning too. This interface between evolutionary biology and biodiversity conservation can therefore provide methodological guidance to

  16. Competing values, tensions and trade-offs in management of nuclear power plants.

    PubMed

    Reiman, Teemu; Rollenhagen, Carl

    2012-01-01

    The specific goal of the study is to look how tensions, competing values and trade-offs manifest in the management of nuclear power plants. Second goal is to inspect how existing frameworks, such as Competing Values Framework, can be used to model the tensions. Empirical data consists of thirty interviews that were conducted as part of a NKS study on safety culture in the Nordic nuclear branch. Eight trade-offs are identified based on a grounded theory based analysis of the interview data. The competing values and potential tensions involved in the trade-offs are discussed.

  17. Source-structure trade-offs in ambient noise correlations: Theory and numerical examples

    NASA Astrophysics Data System (ADS)

    Fichtner, A.; Sager, K.; Ermert, L. A.

    2015-12-01

    We analyse the physics and geometry of trade-offs between Earth structure and noise sources in inter-station noise correlations. Our approach is based on the computation of off-diagonal Hessian elements that describe the extent to which variations in noise sources can compensate for variations in Earth structure without changing the misfit beyond the measurement uncertainty. Despite the fact that all ambient noise inverse problems are special in terms of their receiver configuration and data, some general statements concerning source-structure trade-offs can be made: (i) While source-structure trade-offs may be reduced to some extent by clever measurement design, there are inherent trade-offs that can generally not be avoided. These inherent trade-offs may lead to a mispositioning of structural heterogeneities when the noise source distribution is unknown. (ii) When attenuation is weak, source-structure trade-offs in ambient noise correlations are a global phenomenon, meaning that there is no noise source perturbation that does not trade-off with some Earth structure, and vice versa. (iii) The most significant source-structure trade-offs occur within two elliptically shaped regions connecting a potential noise source perturbation to each one of the receivers. (iv) Far from these elliptical regions, only small-scale structure can trade off against changes in the noise source. (v) While source-structure trade-offs mostly decay with increasing attenuation, they are nearly unaffected by attenuation when the noise source perturbation is located near the receiver-receiver line. We complement these theoretical considerations by numerical experiments where we model ambient noise correlations for arbitrary source geometries. The experiments illustrate how and to which extent unknown noise sources may map into spurious Earth structure. This work is intended to contribute to the development of joint source-structure inversions of ambient noise correlations, and in particular

  18. A Computational Analysis of Stoichiometric Constraints and Trade-Offs in Cyanobacterial Biofuel Production

    PubMed Central

    Knoop, Henning; Steuer, Ralf

    2015-01-01

    Cyanobacteria are a promising biological chassis for the synthesis of renewable fuels and chemical bulk commodities. Significant efforts have been devoted to improve the yields of cyanobacterial products. However, while the introduction and heterologous expression of product-forming pathways is often feasible, the interactions and incompatibilities of product synthesis with the host metabolism are still insufficiently understood. In this work, we investigate the stoichiometric properties and trade-offs that underlie cyanobacterial product formation using a computational reconstruction of cyanobacterial metabolism. First, we evaluate the synthesis requirements of a selection of cyanobacterial products of potential biotechnological interest. Second, the large-scale metabolic reconstruction allows us to perform in silico experiments that mimic and predict the metabolic changes that must occur in the transition from a growth-only phenotype to a production-only phenotype. Applied to the synthesis of ethanol, ethylene, and propane, these in silico transition experiments point to bottlenecks and potential modification targets in cyanobacterial metabolism. Our analysis reveals incompatibilities between biotechnological product synthesis and native host metabolism, such as shifts in ATP/NADPH demand and the requirement to reintegrate metabolic by-products. Similar strategies can be employed for a large class of cyanobacterial products to identify potential stoichiometric bottlenecks. PMID:25941672

  19. Parasite-mediated selection drives an immunogenetic trade-off in plains zebras (Equus quagga).

    PubMed

    Kamath, Pauline L; Turner, Wendy C; Küsters, Martina; Getz, Wayne M

    2014-05-22

    Pathogen evasion of the host immune system is a key force driving extreme polymorphism in genes of the major histocompatibility complex (MHC). Although this gene family is well characterized in structure and function, there is still much debate surrounding the mechanisms by which MHC diversity is selectively maintained. Many studies have investigated relationships between MHC variation and specific pathogens, and have found mixed support for and against the hypotheses of heterozygote advantage, frequency-dependent or fluctuating selection. Few, however, have focused on the selective effects of multiple parasite types on host immunogenetic patterns. Here, we examined relationships between variation in the equine MHC gene, ELA-DRA, and both gastrointestinal (GI) and ectoparasitism in plains zebras (Equus quagga). Specific alleles present at opposing population frequencies had antagonistic effects, with rare alleles associated with increased GI parasitism and common alleles with increased tick burdens. These results support a frequency-dependent mechanism, but are also consistent with fluctuating selection. Maladaptive GI parasite 'susceptibility alleles' were reduced in frequency, suggesting that these parasites may play a greater selective role at this locus. Heterozygote advantage, in terms of allele mutational divergence, also predicted decreased GI parasite burden in genotypes with a common allele. We conclude that an immunogenetic trade-off affects resistance/susceptibility to parasites in this system. Because GI and ectoparasites do not directly interact within hosts, our results uniquely show that antagonistic parasite interactions can be indirectly modulated through the host immune system. This study highlights the importance of investigating the role of multiple parasites in shaping patterns of host immunogenetic variation.

  20. The tortoise or the hare? Impacts of within-host dynamics on transmission success of arthropod-borne viruses

    PubMed Central

    Althouse, Benjamin M.; Hanley, Kathryn A.

    2015-01-01

    Arthropod-borne viruses (arboviruses) are maintained in a cycle of alternating transmission between vertebrate hosts and arthropod vectors. Arboviruses possess RNA genomes capable of rapid diversification and adaptation, and the between-host trade-offs inherent to host alternation impose well-documented constraints on arbovirus evolution. Here, we investigate the less well-studied within-host trade-offs that shape arbovirus replication dynamics and transmission. Arboviruses generally establish lifelong infection in vectors but transient infection of variable magnitude (i.e. peak virus concentration) and duration in vertebrate hosts. In the majority of experimental infections of vertebrate hosts, both the magnitude and duration of arbovirus replication depended upon the dose of virus administered, with increasing dose resulting in greater magnitude but shorter duration of viraemia. This pattern suggests that the vertebrate immune response imposes a trade-off between the height and breadth of the virus replication curve. To investigate the impact of this trade-off on transmission, we used a simple modelling approach to contrast the effect of ‘tortoise’ (low magnitude, long duration viraemia) and ‘hare’ (high magnitude, short duration viraemia) arbovirus replication strategies on transmission. This model revealed that, counter to previous theory, arboviruses that adopt a tortoise strategy have higher rates of persistence in both host and vector populations. PMID:26150665

  1. How zooplankton feed: mechanisms, traits and trade-offs.

    PubMed

    Kiørboe, Thomas

    2011-05-01

    Zooplankton is a morphologically and taxonomically diverse group and includes organisms that vary in size by many orders of magnitude, but they are all faced with the common problem of collecting food from a very dilute suspension. In order to maintain a viable population in the face of mortality, zooplankton in the ocean have to clear daily a volume of ambient water for prey particles that is equivalent to about 10(6) times their own body volume. While most size-specific vital rates and mortality rates decline with size, the clearance requirement is largely size-independent because food availability also declines with size. There is a limited number of solutions to the problem of concentrating dilute prey from a sticky medium: passive and active ambush feeding; feeding-current feeding, where the prey is either intercepted directly, retained on a filter, or individually perceived and extracted from the feeding current; cruise feeding; and colonization of large particles and marine snow aggregates. The basic mechanics of these food-collection mechanisms are described, and it is shown that their efficiencies are inherently different and that each of these mechanisms becomes less efficient with increasing size. Mechanisms that compensate for this decline in efficiency are described, including inflation of feeding structures and development of vision. Each feeding mode has implications beyond feeding in terms of risk of encountering predators and chance of meeting mates, and they partly target different types of prey. The main dichotomy is between (inefficient) ambush feeding on motile prey and the more efficient active feeding modes; a secondary dichotomy is between (efficient) hovering and (less efficient) cruising feeding modes. The efficiencies of the various feeding modes are traded off against feeding-mode-dependent metabolic expenses, predation risks, and mating chances. The optimality of feeding strategies, evaluated as the ratio of gain over risk, varies with

  2. Pathogen evolution under host avoidance plasticity.

    PubMed

    McLeod, David V; Day, Troy

    2015-09-07

    Host resistance consists of defences that limit pathogen burden, and can be classified as either adaptations targeting recovery from infection or those focused upon infection avoidance. Conventional theory treats avoidance as a fixed strategy which does not vary from one interaction to the next. However, there is increasing empirical evidence that many avoidance strategies are triggered by external stimuli, and thus should be treated as phenotypically plastic responses. Here, we consider the implications of avoidance plasticity for host-pathogen coevolution. We uncover a number of predictions challenging current theory. First, in the absence of pathogen trade-offs, plasticity can restrain pathogen evolution; moreover, the pathogen exploits conditions in which the host would otherwise invest less in resistance, causing resistance escalation. Second, when transmission trades off with pathogen-induced mortality, plasticity encourages avirulence, resulting in a superior fitness outcome for both host and pathogen. Third, plasticity ensures the sterilizing effect of pathogens has consequences for pathogen evolution. When pathogens castrate hosts, selection forces them to minimize mortality virulence; moreover, when transmission trades off with sterility alone, resistance plasticity is sufficient to prevent pathogens from evolving to fully castrate.

  3. Parent-offspring conflict and the genetic trade-offs shaping parental investment.

    PubMed

    Kölliker, Mathias; Boos, Stefan; Wong, Janine W Y; Röllin, Lilian; Stucki, Dimitri; Raveh, Shirley; Wu, Min; Meunier, Joël

    2015-04-16

    The genetic conflict between parents and their offspring is a cornerstone of kin selection theory and the gene-centred view of evolution, but whether it actually occurs in natural systems remains an open question. Conflict operates only if parenting is driven by genetic trade-offs between offspring performance and the parent's ability to raise additional offspring, and its expression critically depends on the shape of these trade-offs. Here we investigate the occurrence and nature of genetic conflict in an insect with maternal care, the earwig Forficula auricularia. Specifically, we test for a direct response to experimental selection on female future reproduction and correlated responses in current offspring survival, developmental rate and growth. The results demonstrate genetic trade-offs that differ in shape before and after hatching. Our study not only provides direct evidence for parent-offspring conflict but also highlights that conflict is not inevitable and critically depends on the genetic trade-offs shaping parental investment.

  4. Endocrine uncoupling of the trade-off between reproduction and somatic maintenance in eusocial insects.

    PubMed

    Rodrigues, Marisa A; Flatt, Thomas

    2016-08-01

    In most animals reproduction trades off with somatic maintenance and survival. Physiologically this trade-off is mediated by hormones with opposite effects on reproduction and maintenance. In many insects, this regulation is achieved by an endocrine network that integrates insulin-like/IGF-1 signaling (IIS), juvenile hormone (JH), and the yolk precursor vitellogenin (Vg) (or, more generally, yolk proteins [YPs]). Downregulation of this network promotes maintenance and survival at the expense of reproduction. Remarkably, however, queens of highly eusocial social insects exhibit both enormous reproductive output and longevity, thus escaping the trade-off. Here we argue - based on recent evidence - that the proximate reason for why eusocial insects can decouple this trade-off is that they have evolved a different 'wiring' of the IIS-JH-Vg/YP circuit.

  5. The trade-off between food and temperature in the habitat choice of bluegill sunfish

    USGS Publications Warehouse

    Wildhaber, M.L.

    2001-01-01

    A model is presented to describe the trade-off between food and temperature in bluegills Lepomis macrochirus, where temperature was the primary factor used in determining the patch in which to reside.

  6. Competition and predation in simple food webs: intermediately strong trade-offs maximize coexistence.

    PubMed Central

    HilleRisLambers, Reinier; Dieckmann, Ulf

    2003-01-01

    Competition and predation are fundamental interactions structuring food webs. However, rather than always following these neat theoretical categories, mixed interactions are ubiquitous in nature. Of particular importance are omnivorous species, such as intra-guild predators that can both compete with and predate on their prey. Here, we examine trade-offs between competitive and predatory capacities by analysing the entire continuum of food web configurations existing between purely predator-prey and purely competitive interactions of two consumers subsisting on a single resource. Our results show that the range of conditions allowing for coexistence of the consumers is maximized at intermediately strong trade-offs. Even though coexistence under weak trade-offs and under very strong trade-offs is also possible, it occurs under much more restrictive conditions. We explain these findings by an intricate interplay between energy acquisition and interaction strength. PMID:14728782

  7. Risk/Requirements Trade-off Guidelines for Low Cost Satellite Systems

    NASA Technical Reports Server (NTRS)

    Cornford, Steven L.; Man, Kin F.

    1996-01-01

    The accelerating trend toward faster, better, cheaper missions places increasing emphasis on the trade-offs between requirements and risk to reduce cost and development times, while still improving quality and reliability. The Risk/Requirement Trade-off Guidelines discussed in this paper are part of an integrated approach to address the main issues by focusing on the sum of prevention, analysis, control, or test (PACT) processes.

  8. Light Helicopter Family Trade-Off Analysis. Volume 8. Appendices S and T

    DTIC Science & Technology

    2014-01-02

    UNITED STATES AIMY MATERIEL COMMAND LIGHT I COPTER FAMlL Y TllADE-QFF ANALYSIS APPENDICES S AND T VOLUME VIII ACN : 69396 Copy IQJ. of 130...REPORT NUMBER ACN 69396 2. GOVT ACCESSION NO. 4. TITLE (and Subtltl») LIGHT HELICOPTER FAMILY TRADE-OFF ANALYSIS, APPENDICES S AND T, VOLUME VIII...UNITED STATES ARMY MATERIEL COMMAND LIGHT HELICOPTER FAMILY TRADE-OFF ANALYSIS APPENDICES S AND T . VOLUME VIII ACN : 69396 1 Accession For

  9. Trade-offs between the accuracy and integrity of autobiographical narrative in memory reconsolidation.

    PubMed

    Montemayor, Carlos

    2015-01-01

    Lane et al. propose an integrative model for the reconsolidation of traces in their timely and impressive article. This commentary draws attention to trade-offs between accuracy and self-narrative integrity in the model. The trade-offs concern the sense of agency in memory and its role in both implicit and explicit memory reconsolidation, rather than balances concerning degrees of emotional arousal.

  10. A design-constraint trade-off underpins the diversity in ecologically important traits in species Escherichia coli.

    PubMed

    Phan, Katherine; Ferenci, Thomas

    2013-10-01

    Bacterial species are internally diverse in genomic and multi-locus gene comparisons. The ecological causes of phenotypic and genotypic diversity within species are far less well understood. Here, we focus on the competitive fitness for growth on nutrients within Escherichia coli, an internally rich species. Competition experiments in nutrient-limited chemostats revealed that members of the ECOR collection exhibited a wide continuum of competitive abilities, with some fitter and some less fit than the lab strain MG1655. We observed an inverse relationship between competitiveness and the resistance of strains to detergent and antibiotic, consistent with the notion that membrane permeability and competitive fitness are linked by a trade-off between self-preservation and nutritional competence (SPANC); high permeability has a postulated cost in antibacterial sensitivity whereas a low permeability has a cost in nutrient affinity. Isolates moved along the markedly nonlinear trade-off curve by mutational adaptation; an ECOR strain sensitive to antibacterials and a good competitor was easily converted by mutation into a mutant with higher resistance but poorer competition in the presence of low antibiotic concentrations. Conversely, a resistant ECOR strain changed into a better competitor after a short period of selection under nutrient limitation. In both directions, mutations can affect porin proteins and outer membrane permeability, as indicated by protein analysis, gene sequencing and an independent assay of outer membrane permeability. The extensive, species-wide diversity of E. coli in ecologically important traits can thus be explained as an evolutionary consequence of a SPANC trade-off driven by antagonistic pleiotropy.

  11. Phenotypic constraints and community structure: linking trade-offs within and among species.

    PubMed

    Angert, Amy L; Kimball, Sarah; Peterson, Megan; Huxman, Travis E; Venable, David L

    2014-11-01

    Trade-offs are central to many topics in biology, from the evolution of life histories to ecological mechanisms of species coexistence. Trade-offs observed among species may reflect pervasive constraints on phenotypes that are achievable given biophysical and resource limitations. If so, then among-species trade-offs should be consistent with trade-offs within species. Alternatively, trait variation among co-occurring species may reflect historical contingencies during community assembly rather than within-species constraints. Here, we test whether a key trade-off between relative growth rate (RGR) and water-use efficiency (WUE) among Sonoran Desert winter annual plants is apparent within four species representing different strategies in the system. We grew progeny of maternal families from multiple populations in a greenhouse common garden. One species, Pectocarya recurvata, displayed the expected RGR-WUE trade-off among families within populations. For other species, although RGR and WUE often varied clinally among populations, among-family variation within populations was lacking, implicating a role for past selection on these traits. Our results suggest that a combination of limited genetic variation in single traits and negative trait correlations could pose constraints on the evolution of a high-RGR and high-WUE phenotype within species, providing a microevolutionary explanation for phenotypes that influence community-level patterns of abundance and coexistence.

  12. Life history trade-offs and evidence for hierarchical resource allocation in two monocarpic perennials.

    PubMed

    Cao, G-X; Worley, A C

    2013-01-01

    The evolution of floral display is thought to be constrained by trade-offs between the size and number of flowers; however, empirical evidence for the trade-off is inconsistent. We examined evidence for trade-offs and hierarchical allocation of resources within and between two populations each of the monocarpic perennials, Cardiocrinum cordatum and C. giganteum. Within all populations, flower size-number trade-offs were evident after accounting for variation in plant size. In addition, variation in flower size explained much variation in flower-level allocation to attraction, and female and male function, a pattern consistent with hierarchical allocation. However, between population differences in flower size (C. cordatum) and number (C. giganteum) were not consistent with size-number trade-offs or hierarchical allocation. The population-level difference in C. cordatum likely reflects the combined influence of a time lag between initiation and maturation of flowers, and higher light levels in one population. Thus, our study highlights one mechanism that may account for the apparent independence of flower size and number in many studies. A prediction of sex allocation theory was also supported. In C. giganteum: plants from one population invested more mass in pistils and less in stamens than did plants from the other population. Detection of floral trade-offs in Cardiocrinum may be facilitated by monocarpic reproduction, production of a single inflorescence and ease of measuring plant size.

  13. Reproductive trade-offs may moderate the impact of Gyrodactylus salaris in warmer climates.

    PubMed

    Denholm, Scott J; Norman, Rachel A; Hoyle, Andrew S; Shinn, Andrew P; Taylor, Nick G H

    2013-01-01

    Gyrodactylus salaris is a notifiable freshwater ectoparasite of salmonids. Its primary host is Atlantic salmon (Salmo salar), upon which infections can cause death, and have led to massive declines in salmon numbers in Norway, where the parasite is widespread. Different strains of S. salar vary in their susceptibility, with Atlantic strains (such as those found in Norway) exhibiting no resistance to the parasite, and Baltic strains demonstrating an innate resistance sufficient to regulate parasite numbers on the host causing it to either die out or persist at a low level. In this study, Leslie matrix and compartmental models were used to generate data that demonstrated the population growth of G. salaris on an individual host is dependent on the total number of offspring per parasite, its longevity and the timing of its births. The data demonstrated that the key factor determining the rate of G. salaris population growth is the time at which the parasite first gives birth, with rapid birth rate giving rise to large population size. Furthermore, it was shown that though the parasite can give birth up to four times, only two births are required for the population to persist as long as the first birth occurs before a parasite is three days old. As temperature is known to influence the timing of the parasite's first birth, greater impact may be predicted if introduced to countries with warmer climates than Norway, such as the UK and Ireland which are currently recognised to be free of G. salaris. However, the outputs from the models developed in this study suggest that temperature induced trade-offs between the total number of offspring the parasite gives birth to and the first birth timing may prevent increased population growth rates over those observed in Norway.

  14. Emergence of host-adapted Salmonella Enteritidis through rapid evolution in an immunocompromised host

    PubMed Central

    Klemm, Elizabeth J; Gkrania-Klotsas, Effrossyni; Hadfield, James; Forbester, Jessica L; Harris, Simon R; Hale, Christine; Heath, Jennifer N; Wileman, Thomas; Clare, Simon; Kane, Leanne; Goulding, David; Otto, Thomas D; Kay, Sally; Doffinger, Rainer; Cooke, Fiona J; Carmichael, Andrew; Lever, Andrew ML; Parkhill, Julian; MacLennan, Calman A; Kumararatne, Dinakantha

    2016-01-01

    Summary Host adaptation is a key factor contributing to the emergence of new bacterial, viral and parasitic pathogens. Many pathogens are considered promiscuous because they cause disease across a range of host species, while others are host-adapted, infecting particular hosts1. Host adaptation can potentially progress to host restriction where the pathogen is strictly limited to a single host species and is frequently associated with more severe symptoms. Host-adapted and host-restricted bacterial clades evolve from within a broader host-promiscuous species and sometimes target different niches within their specialist hosts, such as adapting from a mucosal to a systemic lifestyle. Genome degradation, marked by gene inactivation and deletion, is a key feature of host adaptation, although the triggers initiating genome degradation are not well understood. Here, we show that a chronic systemic non-typhoidal Salmonella infection in an immunocompromised human patient resulted in genome degradation targeting genes that are expendable for a systemic lifestyle. We present a genome-based investigation of a recurrent blood-borne Salmonella enterica serotype Enteritidis (S. Enteritidis) infection covering 15 years in an interleukin (IL)-12 β-1 receptor-deficient individual that developed into an asymptomatic chronic infection. The infecting S. Enteritidis harbored a mutation in the mismatch repair gene mutS that accelerated the genomic mutation rate. Phylogenetic analysis and phenotyping of multiple patient isolates provides evidence for a remarkable level of within-host evolution that parallels genome changes present in successful host-restricted bacterial pathogens but never before observed on this timescale. Our analysis identifies common pathways of host adaptation and demonstrates the role that immunocompromised individuals can play in this process. PMID:27127642

  15. Nutritional and non-nutritional food components modulate phenotypic variation but not physiological trade-offs in an insect

    PubMed Central

    Pascacio-Villafán, Carlos; Williams, Trevor; Birke, Andrea; Aluja, Martín

    2016-01-01

    Our understanding of how food modulates animal phenotypes and mediate trade-offs between life-history traits has benefited greatly from the study of combinations of nutritional and non-nutritional food components, such as plant secondary metabolites. We used a fruit fly pest, Anastrepha ludens, to examine phenotypic variation across larval, pupal and adult stages as a function of larval food with varying nutrient balance and content of chlorogenic acid, a secondary metabolite. Larval insects that fed on carbohydrate-biased diets relative to protein exhibited longer larval and pupal developmental periods, were often heavier as pupae and resisted desiccation and starvation for longer periods in the adult stage than insects fed on highly protein-biased diets. Except for a potential conflict between pupal development time and adult desiccation and starvation resistance, we did not detect physiological trade-offs mediated by the nutritional balance in larval food. Chlorogenic acid affected A. ludens development in a concentration and nutrient-dependent manner. Nutrients and host plant secondary metabolites in the larval diet induced changes in A. ludens phenotype and could influence fruit fly ecological interactions. We provide a unique experimental and modelling approach useful in generating predictive models of life history traits in a variety of organisms. PMID:27406923

  16. Escherichia coli deletion mutants illuminate trade-offs between growth rate and flux through a foreign anabolic pathway.

    PubMed

    Falls, Kelly C; Williams, Aimee L; Bryksin, Anton V; Matsumura, Ichiro

    2014-01-01

    Metabolic engineers strive to improve the production yields of microbial fermentations, sometimes by mutating the genomes of production strains. Some mutations are detrimental to the health of the organism, so a quantitative and mechanistic understanding of the trade-offs could inform better designs. We employed the bacterial luciferase operon (luxABCDE), which uses ubiquitous energetic cofactors (NADPH, ATP, FMNH2, acetyl-CoA) from the host cell, as a proxy for a novel anabolic pathway. The strains in the Escherichia coli Keio collection, each of which contains a single deletion of a non-essential gene, represent mutational choices that an engineer might make to optimize fermentation yields. The Keio strains and the parental BW25113 strain were transformed with a luxABCDE expression vector. Each transformant was propagated in defined M9 medium at 37 °C for 48 hours; the cell density (optical density at 600 nanometers, OD600) and luminescence were measured every 30 minutes. The trade-offs were visualized by plotting the maximum growth rate and luminescence/OD600 of each transformant across a "production possibility frontier". Our results show that some loss-of-function mutations enhance growth in vitro or light production, but that improvement in one trait generally comes at the expense of the other.

  17. Insight into trade-off between wood decay and parasitism from the genome of a fungal forest pathogen

    SciTech Connect

    Olson, Ake; Aerts, Andrea; Asiegbu, Fred; Belbahri, Lassaad; Bouzid, Ourdia; Broberg, Anders; Canback, Bjorn; Coutinho, Pedro M.; Cullen, Dan; Dalman, Kerstin; Deflorio, Giuliana; van Diepen, Linda T. A.; Dunand, Christophe; Duplessis, Sebastien; Durling, Mikael; Gonthier, Paolo; Grimwood, Jane; Fossdal, Carl Gunnar; Hansson, David; Henrissat, Bernard; Hietala, Ari; Himmelstrand, Kajsa; Hoffmeister, Dirk; Hogberg, Nils; James, Timothy Y.; Karlsson, Magnus; Kohler, Annegret; Lucas, Susan; Lunden, Karl; Morin, Emmanuelle; Murat, Claude; Park, Jongsun; Raffaello, Tommaso; Rouze, Pierre; Salamov, Asaf; Schmutz, Jeremy; Solheim, Halvor; Stahlberg, Jerry; Velez, Heriberto; de Vries, Ronald P.; Wiebenga, Ad; Woodward, Steve; Yakovlev, Igor; Garbelotto, Matteo; Martin, Francis; Grigoriev, Igor V.; Stenlid, Jan

    2012-01-01

    Parasitism and saprotrophic wood decay are two fungal strategies fundamental for succession and nutrient cycling in forest ecosystems. An opportunity to assess the trade-off between these strategies is provided by the forest pathogen and wood decayer Heterobasidion annosum sensu lato. We report the annotated genome sequence and transcript profiling, as well as the quantitative trait loci mapping, of one member of the species complex: H. irregulare. Quantitative trait loci critical for pathogenicity, and rich in transposable elements, orphan and secreted genes, were identified. A wide range of cellulose-degrading enzymes are expressed during wood decay. By contrast, pathogenic interaction between H. irregulare and pine engages fewer carbohydrate-active enzymes, but involves an increase in pectinolytic enzymes, transcription modules for oxidative stress and secondary metabolite production. Our results show a trade-off in terms of constrained carbohydrate decomposition and membrane transport capacity during interaction with living hosts. Our findings establish that saprotrophic wood decay and necrotrophic parasitism involve two distinct, yet overlapping, processes.

  18. Nutritional and non-nutritional food components modulate phenotypic variation but not physiological trade-offs in an insect.

    PubMed

    Pascacio-Villafán, Carlos; Williams, Trevor; Birke, Andrea; Aluja, Martín

    2016-07-12

    Our understanding of how food modulates animal phenotypes and mediate trade-offs between life-history traits has benefited greatly from the study of combinations of nutritional and non-nutritional food components, such as plant secondary metabolites. We used a fruit fly pest, Anastrepha ludens, to examine phenotypic variation across larval, pupal and adult stages as a function of larval food with varying nutrient balance and content of chlorogenic acid, a secondary metabolite. Larval insects that fed on carbohydrate-biased diets relative to protein exhibited longer larval and pupal developmental periods, were often heavier as pupae and resisted desiccation and starvation for longer periods in the adult stage than insects fed on highly protein-biased diets. Except for a potential conflict between pupal development time and adult desiccation and starvation resistance, we did not detect physiological trade-offs mediated by the nutritional balance in larval food. Chlorogenic acid affected A. ludens development in a concentration and nutrient-dependent manner. Nutrients and host plant secondary metabolites in the larval diet induced changes in A. ludens phenotype and could influence fruit fly ecological interactions. We provide a unique experimental and modelling approach useful in generating predictive models of life history traits in a variety of organisms.

  19. A New Model for Solving Time-Cost-Quality Trade-Off Problems in Construction.

    PubMed

    Fu, Fang; Zhang, Tao

    2016-01-01

    A poor quality affects project makespan and its total costs negatively, but it can be recovered by repair works during construction. We construct a new non-linear programming model based on the classic multi-mode resource constrained project scheduling problem considering repair works. In order to obtain satisfactory quality without a high increase of project cost, the objective is to minimize total quality cost which consists of the prevention cost and failure cost according to Quality-Cost Analysis. A binary dependent normal distribution function is adopted to describe the activity quality; Cumulative quality is defined to determine whether to initiate repair works, according to the different relationships among activity qualities, namely, the coordinative and precedence relationship. Furthermore, a shuffled frog-leaping algorithm is developed to solve this discrete trade-off problem based on an adaptive serial schedule generation scheme and adjusted activity list. In the program of the algorithm, the frog-leaping progress combines the crossover operator of genetic algorithm and a permutation-based local search. Finally, an example of a construction project for a framed railway overpass is provided to examine the algorithm performance, and it assist in decision making to search for the appropriate makespan and quality threshold with minimal cost.

  20. A New Model for Solving Time-Cost-Quality Trade-Off Problems in Construction

    PubMed Central

    Fu, Fang; Zhang, Tao

    2016-01-01

    A poor quality affects project makespan and its total costs negatively, but it can be recovered by repair works during construction. We construct a new non-linear programming model based on the classic multi-mode resource constrained project scheduling problem considering repair works. In order to obtain satisfactory quality without a high increase of project cost, the objective is to minimize total quality cost which consists of the prevention cost and failure cost according to Quality-Cost Analysis. A binary dependent normal distribution function is adopted to describe the activity quality; Cumulative quality is defined to determine whether to initiate repair works, according to the different relationships among activity qualities, namely, the coordinative and precedence relationship. Furthermore, a shuffled frog-leaping algorithm is developed to solve this discrete trade-off problem based on an adaptive serial schedule generation scheme and adjusted activity list. In the program of the algorithm, the frog-leaping progress combines the crossover operator of genetic algorithm and a permutation-based local search. Finally, an example of a construction project for a framed railway overpass is provided to examine the algorithm performance, and it assist in decision making to search for the appropriate makespan and quality threshold with minimal cost. PMID:27911939

  1. Concepts and trade-offs in velocity estimation with plane-wave contrast-enhanced Doppler.

    PubMed

    Tremblay-Darveau, Charles; Williams, Ross; Sheeran, Paul; Milot, Laurent; Bruce, Matthew; Burns, Peter

    2016-07-29

    While long Doppler ensembles are, in principle, beneficial for velocity estimates, short acoustic pulses must be used in microbubble contrast-enhanced Doppler to mitigate microbubble destruction. This introduces inherent trade-offs in velocity estimates with autocorrelators, which are studied here. A model of the autocorrelation function adapted to the microbubble Doppler signal, accounting for transit time, the echo frequency uncertainty and contrast-agent destruction is derived and validated in vitro. It is further demonstrated that a local measurement of the center frequency of the microbubble echo is essential in order to avoid significant bias in velocity estimates arising from the linear and nonlinear frequency-dependent scattering of microbubbles, and compensate the inherent speckle nature of the received echo frequency. For these reasons, broadband Doppler estimators (2D autocorrelator, Radon projection) are better suited than simpler narrowband estimators (1D autocorrelator, 1D Fourier transform) for contrast-enhanced flow assessment. A case study of perfusion in a VX-2 carcinoma using contrast-enhanced planewave Doppler is also shown. We demonstrate that even when considering all uncertainties associated with microbubble-related decorrelation (destruction, pulse bandwidth, transit time, flow gradient) and the need for real-time imaging, a coefficient of variation of 4% on the an axial velocity is achievable with planewave imaging.

  2. Dopaminergic Control of the Exploration-Exploitation Trade-Off via the Basal Ganglia

    PubMed Central

    Humphries, Mark D.; Khamassi, Mehdi; Gurney, Kevin

    2012-01-01

    We continuously face the dilemma of choosing between actions that gather new information or actions that exploit existing knowledge. This “exploration-exploitation” trade-off depends on the environment: stability favors exploiting knowledge to maximize gains; volatility favors exploring new options and discovering new outcomes. Here we set out to reconcile recent evidence for dopamine’s involvement in the exploration-exploitation trade-off with the existing evidence for basal ganglia control of action selection, by testing the hypothesis that tonic dopamine in the striatum, the basal ganglia’s input nucleus, sets the current exploration-exploitation trade-off. We first advance the idea of interpreting the basal ganglia output as a probability distribution function for action selection. Using computational models of the full basal ganglia circuit, we showed that, under this interpretation, the actions of dopamine within the striatum change the basal ganglia’s output to favor the level of exploration or exploitation encoded in the probability distribution. We also found that our models predict striatal dopamine controls the exploration-exploitation trade-off if we instead read-out the probability distribution from the target nuclei of the basal ganglia, where their inhibitory input shapes the cortical input to these nuclei. Finally, by integrating the basal ganglia within a reinforcement learning model, we showed how dopamine’s effect on the exploration-exploitation trade-off could be measurable in a forced two-choice task. These simulations also showed how tonic dopamine can appear to affect learning while only directly altering the trade-off. Thus, our models support the hypothesis that changes in tonic dopamine within the striatum can alter the exploration-exploitation trade-off by modulating the output of the basal ganglia. PMID:22347155

  3. No trade-off between learning speed and associative flexibility in bumblebees: a reversal learning test with multiple colonies.

    PubMed

    Raine, Nigel E; Chittka, Lars

    2012-01-01

    Potential trade-offs between learning speed and memory-related performance could be important factors in the evolution of learning. Here, we test whether rapid learning interferes with the acquisition of new information using a reversal learning paradigm. Bumblebees (Bombus terrestris) were trained to associate yellow with a floral reward. Subsequently the association between colour and reward was reversed, meaning bees then had to learn to visit blue flowers. We demonstrate that individuals that were fast to learn yellow as a predictor of reward were also quick to reverse this association. Furthermore, overnight memory retention tests suggest that faster learning individuals are also better at retaining previously learned information. There is also an effect of relatedness: colonies whose workers were fast to learn the association between yellow and reward also reversed this association rapidly. These results are inconsistent with a trade-off between learning speed and the reversal of a previously made association. On the contrary, they suggest that differences in learning performance and cognitive (behavioural) flexibility could reflect more general differences in colony learning ability. Hence, this study provides additional evidence to support the idea that rapid learning and behavioural flexibility have adaptive value.

  4. Evolution of increased competitiveness in cows trades off with reduced milk yield, fertility and more masculine morphology.

    PubMed

    Sartori, Cristina; Mazza, Serena; Guzzo, Nadia; Mantovani, Roberto

    2015-08-01

    In some species females compete for food, foraging territories, mating, and nesting sites. Competing females can exhibit morphological, physiological, and behavioral adaptations typical of males, which are commonly considered as secondary sexual traits. Competition and the development of traits increasing competitiveness require much energy and may exert adverse effects on fecundity and survival. From an evolutionary perspective, positive selection for increased competitiveness would then result in evolution of reduced values for traits related to fitness such as fecundity and survival. There is recent evidence for such evolutionary trade-offs involving male competition, but no study has considered competing females so far. Using data from competitions for dominance in cows (Bos taurus), we found negative genetic correlations between traits providing success in competition, that is, fighting ability and fitness traits related to milk production and with fertility (the inverse of parity-conception interval). Fighting ability also showed low but positive genetic correlations with "masculine" morphological traits, and negative correlations with "feminine" traits. A genetic change in traits over time has occurred due to selection on competitiveness, corresponding to an evolutionary process of "masculinization" counteracting the official selection for milk yield. Similar evolutionary trade-off between success in competition and fitness components may be present in various species experiencing female competition.

  5. No Trade-Off between Learning Speed and Associative Flexibility in Bumblebees: A Reversal Learning Test with Multiple Colonies

    PubMed Central

    Raine, Nigel E.; Chittka, Lars

    2012-01-01

    Potential trade-offs between learning speed and memory-related performance could be important factors in the evolution of learning. Here, we test whether rapid learning interferes with the acquisition of new information using a reversal learning paradigm. Bumblebees (Bombus terrestris) were trained to associate yellow with a floral reward. Subsequently the association between colour and reward was reversed, meaning bees then had to learn to visit blue flowers. We demonstrate that individuals that were fast to learn yellow as a predictor of reward were also quick to reverse this association. Furthermore, overnight memory retention tests suggest that faster learning individuals are also better at retaining previously learned information. There is also an effect of relatedness: colonies whose workers were fast to learn the association between yellow and reward also reversed this association rapidly. These results are inconsistent with a trade-off between learning speed and the reversal of a previously made association. On the contrary, they suggest that differences in learning performance and cognitive (behavioural) flexibility could reflect more general differences in colony learning ability. Hence, this study provides additional evidence to support the idea that rapid learning and behavioural flexibility have adaptive value. PMID:23028779

  6. Trade-off between frequency and precision during stepping movements: Kinematic and BOLD brain activation patterns.

    PubMed

    Martínez, Martin; Valencia, Miguel; Vidorreta, Marta; Luis, Elkin O; Castellanos, Gabriel; Villagra, Federico; Fernández-Seara, Maria A; Pastor, Maria A

    2016-05-01

    The central nervous system has the ability to adapt our locomotor pattern to produce a wide range of gait modalities and velocities. In reacting to external pacing stimuli, deviations from an individual preferred cadence provoke a concurrent decrease in accuracy that suggests the existence of a trade-off between frequency and precision; a compromise that could result from the specialization within the control centers of locomotion to ensure a stable transition and optimal adaptation to changing environment. Here, we explore the neural correlates of such adaptive mechanisms by visually guiding a group of healthy subjects to follow three comfortable stepping frequencies while simultaneously recording their BOLD responses and lower limb kinematics with the use of a custom-built treadmill device. In following the visual stimuli, subjects adopt a common pattern of symmetric and anti-phase movements across pace conditions. However, when increasing the stimulus frequency, an improvement in motor performance (precision and stability) was found, which suggests a change in the control mode from reactive to predictive schemes. Brain activity patterns showed similar BOLD responses across pace conditions though significant differences were observed in parietal and cerebellar regions. Neural correlates of stepping precision were found in the insula, cerebellum, dorsolateral pons and inferior olivary nucleus, whereas neural correlates of stepping stability were found in a distributed network, suggesting a transition in the control strategy across the stimulated range of frequencies: from unstable/reactive at lower paces (i.e., stepping stability managed by subcortical regions) to stable/predictive at higher paces (i.e., stability managed by cortical regions). Hum Brain Mapp 37:1722-1737, 2016. © 2016 Wiley Periodicals, Inc.

  7. Do highly ornamented and less parasitized males have high quality sperm? – an experimental test for parasite-induced reproductive trade-offs in European minnow (Phoxinus phoxinus)

    PubMed Central

    Kekäläinen, Jukka; Pirhonen, Juhani; Taskinen, Jouni

    2014-01-01

    Parasites take their resources from hosts and thus directly reduce available resources for hosts’ own body functions, such as growth and reproduction. Furthermore, parasite infections cause significant indirect costs to their hosts in terms of increased investments on immune defense. In this study, we investigated the impact of parasite infection on the sperm quality and expression of secondary sexual ornamentation (saturation of the red abdominal colouration and number of breeding tubercles) in the Eurasian minnow (Phoxinus phoxinus). We exposed minnows to a high and low dose of common nonspecific fish ectoparasite, the glochidia larvae of duck mussel (Anodonta anatina) and tested whether parasite infection leads to trade-off in sperm quality and/or ornamental expression. We found that glochidia infection reduces the curvature of the sperm swimming trajectory, number of breeding tubercles, and possibly male competitive ability, but does not affect expression of male color ornamentation. Furthermore, glochidia infection was found to reduce sperm motility, but only when all the noninfected individuals were excluded from the model. Supporting one of the predictions by phenotype-linked fertility hypothesis both in high-infection and low-infection group male breeding colouration was positively associated with sperm quality. Our results suggest that although glochidia infection may have negative impact on male reproductive success, parasite-induced costs may not create strong trade-off between breeding colouration and sperm quality or that such trade-off become detectable only in resource-limited conditions. PMID:25540686

  8. The offspring quantity–quality trade-off and human fertility variation

    PubMed Central

    Lawson, David W.; Borgerhoff Mulder, Monique

    2016-01-01

    The idea that trade-offs between offspring quantity and quality shape reproductive behaviour has long been central to economic perspectives on fertility. It also has a parallel and richer theoretical foundation in evolutionary ecology. We review the application of the quantity–quality trade-off concept to human reproduction, emphasizing distinctions between clutch size and lifetime fertility, and the wider set of forces contributing to fertility variation in iteroparous and sexually reproducing species like our own. We then argue that in settings approximating human evolutionary history, several factors limit costly sibling competition. Consequently, while the optimization of quantity–quality trade-offs undoubtedly shaped the evolution of human physiology setting the upper limits of reproduction, we argue it plays a modest role in accounting for socio-ecological and individual variation in fertility. Only upon entering the demographic transition can fertility limitation be clearly interpreted as strategically orientated to advancing offspring quality via increased parental investment per child, with low fertility increasing descendant socio-economic success, although not reproductive success. We conclude that existing economic and evolutionary literature has often overemphasized the centrality of quantity–quality trade-offs to human fertility variation and advocate for the development of more holistic frameworks encompassing alternative life-history trade-offs and the evolved mechanisms guiding their resolution. PMID:27022072

  9. When are multiobjective calibration trade-offs in hydrologic models meaningful?

    NASA Astrophysics Data System (ADS)

    Kollat, J. B.; Reed, P. M.; Wagener, T.

    2012-03-01

    This paper applies a four-objective calibration strategy focusing on peak flows, low flows, water balance, and flashiness to 392 model parameter estimation experiment (MOPEX) watersheds across the United States. Our analysis explores the influence of model structure by analyzing how the multiobjective calibration trade-offs for two conceptual hydrologic models, the Hydrology Model (HYMOD) and the Hydrologiska Byråns Vattenbalansavdelning (HBV) model, compare for each of the 392 catchments. Our results demonstrate that for modern multiobjective calibration frameworks to identify any meaningful measure of model structural failure, users must be able to carefully control the precision by which they evaluate their trade-offs. Our study demonstrates that the concept of epsilon-dominance provides an effective means of attaining bounded and meaningful hydrologic model calibration trade-offs. When analyzed at an appropriate precision, we found that meaningful multiobjective trade-offs are far less frequent than prior literature has suggested. However, when trade-offs do exist at a meaningful precision, they have significant value for supporting hydrologic model selection, distinguishing core model deficiencies, and identifying hydroclimatic regions where hydrologic model prediction is highly challenging.

  10. Control over speeded actions: a common processing locus for micro- and macro-trade-offs?

    PubMed

    Jentzsch, Ines; Leuthold, Hartmut

    2006-08-01

    Cognitive control processes associated with long- and short-term adjustments of human behaviour have attracted much interest recently. It is still unclear, however, whether the mechanisms underlying these adjustments share a common locus within the chain of stimulus-response processing. In order to address this issue, the present study employed a speed-accuracy instruction producing a macro-trade-off, whereas micro-trade-off was studied by means of posterror slowing in reaction time (RT). Participants performed a spatially compatible or incompatible four-stimuli-to-two-response alternative choice RT task. Reliable variations in micro-and macro-trade-off as well as effects of spatial compatibility were found in RT and error rate. Most importantly, posterror slowing was larger when instruction stressed accuracy rather than speed, an effect being independent of spatial compatibility. Because the influence of speed-accuracy instruction and posterror slowing on performance was strongest for response alternations, together present findings suggest that the mechanisms underlying micro- and macro-trade-offs have one common locus at the level of motor processing. Additional influences of macro-trade-off on premotoric processing are likely.

  11. Ocean Acidification May Aggravate Social-Ecological Trade-Offs in Coastal Fisheries

    PubMed Central

    Voss, Rudi; Quaas, Martin F.; Schmidt, Jörn O.; Kapaun, Ute

    2015-01-01

    Ocean Acidification (OA) will influence marine ecosystems by changing species abundance and composition. Major effects are described for calcifying organisms, which are significantly impacted by decreasing pH values. Direct effects on commercially important fish are less well studied. The early life stages of fish populations often lack internal regulatory mechanisms to withstand the effects of abnormal pH. Negative effects can be expected on growth, survival, and recruitment success. Here we study Norwegian coastal cod, one of the few stocks where such a negative effect was experimentally quantified, and develop a framework for coupling experimental data on OA effects to ecological-economic fisheries models. In this paper, we scale the observed physiological responses to the population level by using the experimentally determined mortality rates as part of the stock-recruitment relationship. We then use an ecological-economic optimization model, to explore the potential effect of rising CO2 concentration on ecological (stock size), economic (profits), consumer-related (harvest) and social (employment) indicators, with scenarios ranging from present day conditions up to extreme acidification. Under the assumptions of our model, yields and profits could largely be maintained under moderate OA by adapting future fishing mortality (and related effort) to changes owing to altered pH. This adaptation comes at the costs of reduced stock size and employment, however. Explicitly visualizing these ecological, economic and social tradeoffs will help in defining realistic future objectives. Our results can be generalized to any stressor (or stressor combination), which is decreasing recruitment success. The main findings of an aggravation of trade-offs will remain valid. This seems to be of special relevance for coastal stocks with limited options for migration to avoid unfavorable future conditions and subsequently for coastal fisheries, which are often small scale local

  12. Ocean acidification may aggravate social-ecological trade-offs in coastal fisheries.

    PubMed

    Voss, Rudi; Quaas, Martin F; Schmidt, Jörn O; Kapaun, Ute

    2015-01-01

    Ocean Acidification (OA) will influence marine ecosystems by changing species abundance and composition. Major effects are described for calcifying organisms, which are significantly impacted by decreasing pH values. Direct effects on commercially important fish are less well studied. The early life stages of fish populations often lack internal regulatory mechanisms to withstand the effects of abnormal pH. Negative effects can be expected on growth, survival, and recruitment success. Here we study Norwegian coastal cod, one of the few stocks where such a negative effect was experimentally quantified, and develop a framework for coupling experimental data on OA effects to ecological-economic fisheries models. In this paper, we scale the observed physiological responses to the population level by using the experimentally determined mortality rates as part of the stock-recruitment relationship. We then use an ecological-economic optimization model, to explore the potential effect of rising CO2 concentration on ecological (stock size), economic (profits), consumer-related (harvest) and social (employment) indicators, with scenarios ranging from present day conditions up to extreme acidification. Under the assumptions of our model, yields and profits could largely be maintained under moderate OA by adapting future fishing mortality (and related effort) to changes owing to altered pH. This adaptation comes at the costs of reduced stock size and employment, however. Explicitly visualizing these ecological, economic and social tradeoffs will help in defining realistic future objectives. Our results can be generalized to any stressor (or stressor combination), which is decreasing recruitment success. The main findings of an aggravation of trade-offs will remain valid. This seems to be of special relevance for coastal stocks with limited options for migration to avoid unfavorable future conditions and subsequently for coastal fisheries, which are often small scale local

  13. Differences in Integron Cassette Excision Dynamics Shape a Trade-Off between Evolvability and Genetic Capacitance

    PubMed Central

    Loot, Céline; Nivina, Aleksandra; Cury, Jean; Escudero, José Antonio; Ducos-Galand, Magaly; Bikard, David; Rocha, Eduardo P. C.

    2017-01-01

    ABSTRACT Integrons ensure a rapid and “on demand” response to environmental stresses driving bacterial adaptation. They are able to capture, store, and reorder functional gene cassettes due to site-specific recombination catalyzed by their integrase. Integrons can be either sedentary and chromosomally located or mobile when they are associated with transposons and plasmids. They are respectively called sedentary chromosomal integrons (SCIs) and mobile integrons (MIs). MIs are key players in the dissemination of antibiotic resistance genes. Here, we used in silico and in vivo approaches to study cassette excision dynamics in MIs and SCIs. We show that the orientation of cassette arrays relative to replication influences attC site folding and cassette excision by placing the recombinogenic strands of attC sites on either the leading or lagging strand template. We also demonstrate that stability of attC sites and their propensity to form recombinogenic structures also regulate cassette excision. We observe that cassette excision dynamics driven by these factors differ between MIs and SCIs. Cassettes with high excision rates are more commonly found on MIs, which favors their dissemination relative to SCIs. This is especially true for SCIs carried in the Vibrio genus, where maintenance of large cassette arrays and vertical transmission are crucial to serve as a reservoir of adaptive functions. These results expand the repertoire of known processes regulating integron recombination that were previously established and demonstrate that, in terms of cassette dynamics, a subtle trade-off between evolvability and genetic capacitance has been established in bacteria. PMID:28351923

  14. Why are not all chilies hot? A trade-off limits pungency.

    PubMed

    Haak, David C; McGinnis, Leslie A; Levey, Douglas J; Tewksbury, Joshua J

    2012-05-22

    Evolutionary biologists increasingly recognize that evolution can be constrained by trade-offs, yet our understanding of how and when such constraints are manifested and whether they restrict adaptive divergence in populations remains limited. Here, we show that spatial heterogeneity in moisture maintains a polymorphism for pungency (heat) among natural populations of wild chilies (Capsicum chacoense) because traits influencing water-use efficiency are functionally integrated with traits controlling pungency (the production of capsaicinoids). Pungent and non-pungent chilies occur along a cline in moisture that spans their native range in Bolivia, and the proportion of pungent plants in populations increases with greater moisture availability. In high moisture environments, pungency is beneficial because capsaicinoids protect the fruit from pathogenic fungi, and is not costly because pungent and non-pungent chilies grown in well-watered conditions produce equal numbers of seeds. In low moisture environments, pungency is less beneficial as the risk of fungal infection is lower, and carries a significant cost because, under drought stress, seed production in pungent chilies is reduced by 50 per cent relative to non-pungent plants grown in identical conditions. This large difference in seed production under water-stressed (WS) conditions explains the existence of populations dominated by non-pungent plants, and appears to result from a genetic correlation between pungency and stomatal density: non-pungent plants, segregating from intra-population crosses, exhibit significantly lower stomatal density (p = 0.003), thereby reducing gas exchange under WS conditions. These results demonstrate the importance of trait integration in constraining adaptive divergence among populations.

  15. Multivariate trade-offs, succession, and phenological differentiation in a guild of colonial invertebrates.

    PubMed

    Edwards, Kyle F; Stachowicz, John J

    2010-11-01

    For competing species limited by one or few resources, diversity is thought to be maintained by trade-offs that allow niche differentiation without resource partitioning. However, few studies have quantified multiple key traits for each species in a guild and shown that trade-offs among these traits apply across the guild. Here we document strong bivariate and multivariate relationships among growth rate, fecundity, longevity, and overgrowth ability for six co-occurring colonial invertebrates. We find that all four of these traits are constrained to a single "fast-slow" niche axis that mechanistically relates life history variation to a colonization-competition trade-off. The location of species on this axis strongly predicts the timing of their peak abundance during succession. We also find that species closer to each other on the fast-slow axis are more likely to differ in reproductive phenology, suggesting a secondary dimension of niche differentiation for otherwise similar species.

  16. Evolutionary trade-offs, Pareto optimality, and the geometry of phenotype space.

    PubMed

    Shoval, O; Sheftel, H; Shinar, G; Hart, Y; Ramote, O; Mayo, A; Dekel, E; Kavanagh, K; Alon, U

    2012-06-01

    Biological systems that perform multiple tasks face a fundamental trade-off: A given phenotype cannot be optimal at all tasks. Here we ask how trade-offs affect the range of phenotypes found in nature. Using the Pareto front concept from economics and engineering, we find that best-trade-off phenotypes are weighted averages of archetypes--phenotypes specialized for single tasks. For two tasks, phenotypes fall on the line connecting the two archetypes, which could explain linear trait correlations, allometric relationships, as well as bacterial gene-expression patterns. For three tasks, phenotypes fall within a triangle in phenotype space, whose vertices are the archetypes, as evident in morphological studies, including on Darwin's finches. Tasks can be inferred from measured phenotypes based on the behavior of organisms nearest the archetypes.

  17. Is There Evidence for a Mixture of Processes in Speed-Accuracy Trade-Off Behavior?

    PubMed

    van Maanen, Leendert

    2016-01-01

    The speed-accuracy trade-off (SAT) effect refers to the behavioral trade-off between fast yet error-prone respones and accurate but slow responses. Multiple theories on the cognitive mechanisms behind SAT exist. One theory assumes that SAT is a consequence of strategically adjusting the amount of evidence required for overt behaviors, such as perceptual choices. Another theory hypothesizes that SAT is the consequence of the mixture of multiple categorically different cognitive processes. In this paper, these theories are disambiguated by assessing whether the fixed-point property of mixture distributions holds, in both simulations and data. I conclude that, at least for perceptual decision making, there is no evidence for a mixture of different cognitive processes to trade off accuracy of responding for speed.

  18. Cancer susceptibility and reproductive trade-offs: a model of the evolution of cancer defences

    PubMed Central

    Boddy, Amy M.; Kokko, Hanna; Breden, Felix; Wilkinson, Gerald S.; Aktipis, C. Athena

    2015-01-01

    The factors influencing cancer susceptibility and why it varies across species are major open questions in the field of cancer biology. One underexplored source of variation in cancer susceptibility may arise from trade-offs between reproductive competitiveness (e.g. sexually selected traits, earlier reproduction and higher fertility) and cancer defence. We build a model that contrasts the probabilistic onset of cancer with other, extrinsic causes of mortality and use it to predict that intense reproductive competition will lower cancer defences and increase cancer incidence. We explore the trade-off between cancer defences and intraspecific competition across different extrinsic mortality conditions and different levels of trade-off intensity, and find the largest effect of competition on cancer in species where low extrinsic mortality combines with strong trade-offs. In such species, selection to delay cancer and selection to outcompete conspecifics are both strong, and the latter conflicts with the former. We discuss evidence for the assumed trade-off between reproductive competitiveness and cancer susceptibility. Sexually selected traits such as ornaments or large body size require high levels of cell proliferation and appear to be associated with greater cancer susceptibility. Similar associations exist for female traits such as continuous egg-laying in domestic hens and earlier reproductive maturity. Trade-offs between reproduction and cancer defences may be instantiated by a variety of mechanisms, including higher levels of growth factors and hormones, less efficient cell-cycle control and less DNA repair, or simply a larger number of cell divisions (relevant when reproductive success requires large body size or rapid reproductive cycles). These mechanisms can affect intra- and interspecific variation in cancer susceptibility arising from rapid cell proliferation during reproductive maturation, intrasexual competition and reproduction. PMID:26056364

  19. Emotion-Induced Trade-Offs in Spatiotemporal Vision

    ERIC Educational Resources Information Center

    Bocanegra, Bruno R.; Zeelenberg, Rene

    2011-01-01

    It is generally assumed that emotion facilitates human vision in order to promote adaptive responses to a potential threat in the environment. Surprisingly, we recently found that emotion in some cases impairs the perception of elementary visual features (Bocanegra & Zeelenberg, 2009b). Here, we demonstrate that emotion improves fast temporal…

  20. Quantifying ecosystem service trade-offs: the case of an urban floodplain in Vienna, Austria.

    PubMed

    Sanon, Samai; Hein, Thomas; Douven, Wim; Winkler, Peter

    2012-11-30

    Wetland ecosystems provide multiple functions and services for the well-being of humans. In urban environments, planning and decision making about wetland restoration inevitably involves conflicting objectives, trade-offs, uncertainties and conflicting value judgments. This study applied trade-off and multi criteria decision analysis to analyze and quantify the explicit trade-offs between the stakeholder's objectives related to management options for the restoration of an urban floodplain, the Lobau, in Vienna, Austria. The Lobau has been disconnected from the main channel of the Danube River through flood protection schemes 130 years ago that have reduced the hydraulic exchange processes. Urban expansion has also changed the adjacent areas and led to increased numbers of visitors, which hampers the maximum potential for ecosystem development and exerts additional pressure on the sensitive habitats in the national park area. The study showed that increased hydraulic connectivity would benefit several stakeholders that preferred the ecological development of the floodplain habitats. However, multiple uses including fishery, agriculture and recreation, exploring the maximum potential in line with national park regulations, were also possible under the increased hydraulic connectivity options. The largest trade-offs were quantified to be at 0.50 score between the ecological condition of the aquatic habitats and the drinking water production and 0.49 score between the ecological condition of the terrestrial habitats and the drinking water production. At this point, the drinking water production was traded-off with 0.40 score, while the ecological condition of the aquatic habitats and the ecological condition of the terrestrial habitats were traded off with 0.30 and 0.23 score, respectively. The majority of the stakeholders involved preferred the management options that increased the hydraulic connectivity compared with the current situation which was not preferred by

  1. Local host adaptation and use of a novel host in the seed beetle Megacerus eulophus.

    PubMed

    Stotz, Gisela C; Suárez, Lorena H; Gonzáles, Wilfredo L; Gianoli, Ernesto

    2013-01-01

    Spatial variation in host plant availability may lead to specialization in host use and local host adaptation in herbivorous insects, which may involve a cost in performance on other hosts. We studied two geographically separated populations of the seed beetle Megacerus eulophus (Coleoptera: Bruchidae) in central Chile: a population from the host Convolvulus chilensis (in Aucó) and a population from C. bonariensis (in Algarrobo). In Aucó C. chilensis is the only host plant, while in Algarrobo both C. bonariensis and C. chilensis are available. We tested local adaptation to these native host plants and its influence on the use of another, exotic host plant. We hypothesized that local adaptation would be verified, particularly for the one-host population (Aucó), and that the Aucó population would be less able to use an alternative, high-quality host. We found evidence of local adaptation in the population from C. chilensis. Thus, when reared on C. chilensis, adults from the C. chilensis population were larger and lived longer than individuals from the C. bonariensis population, while bruchids from the two populations had the same body size and longevity when reared on C. bonariensis. Overall, bruchids from the C. chilensis population showed greater performance traits than those from the C. bonariensis population. There were no differences between the bruchid populations in their ability to use the alternative, exotic host Calystegia sepium, as shown by body size and longevity patterns. Results suggest that differences in local adaptation might be explained by differential host availability in the study populations.

  2. Local Host Adaptation and Use of a Novel Host in the Seed Beetle Megacerus eulophus

    PubMed Central

    Stotz, Gisela C.; Suárez, Lorena H.; Gonzáles, Wilfredo L.; Gianoli, Ernesto

    2013-01-01

    Spatial variation in host plant availability may lead to specialization in host use and local host adaptation in herbivorous insects, which may involve a cost in performance on other hosts. We studied two geographically separated populations of the seed beetle Megacerus eulophus (Coleoptera: Bruchidae) in central Chile: a population from the host Convolvulus chilensis (in Aucó) and a population from C. bonariensis (in Algarrobo). In Aucó C. chilensis is the only host plant, while in Algarrobo both C. bonariensis and C. chilensis are available. We tested local adaptation to these native host plants and its influence on the use of another, exotic host plant. We hypothesized that local adaptation would be verified, particularly for the one-host population (Aucó), and that the Aucó population would be less able to use an alternative, high-quality host. We found evidence of local adaptation in the population from C. chilensis. Thus, when reared on C. chilensis, adults from the C. chilensis population were larger and lived longer than individuals from the C. bonariensis population, while bruchids from the two populations had the same body size and longevity when reared on C. bonariensis. Overall, bruchids from the C. chilensis population showed greater performance traits than those from the C. bonariensis population. There were no differences between the bruchid populations in their ability to use the alternative, exotic host Calystegia sepium, as shown by body size and longevity patterns. Results suggest that differences in local adaptation might be explained by differential host availability in the study populations. PMID:23326528

  3. Effect of flower shape and size on foraging performance and trade-offs in a tropical hummingbird.

    PubMed

    Temeles, Ethan J; Koulouris, Carolyn R; Sander, Sarah E; Kress, W John

    2009-05-01

    Matches between the bills of hummingbirds and the flowers they visit have been interpreted as examples of coadaptation and feeding specialization. Observations of birds feeding at flowers longer or shorter than their bills combined with a lack of experimental evidence for foraging trade-offs, however, fail to support these interpretations. We addressed these inconsistencies by considering a seldom-studied dimension of hummingbird-flower relationships, the shape of bills and flowers, through experiments on the Purple-throated Carib, Eulampis jugularis, and its major food plant, Heliconia, in the eastern Caribbean. Bills of male E. jugularis are considerably shorter and straighter than bills of females. We examined foraging performances and trade-offs during visits to natural heliconias and 34 artificial flowers of differing length and curvature. Supporting predictions based on matches between bill and flower morphology, handling times of females were significantly shorter than those of males at the long, curved flowers of a green morph of H. bihai. Contrary to predictions, handling times of males were not significantly shorter than handling times of females at the short flowers of H. caribaea. At artificial flowers, maximum extraction depths of females were significantly longer than maximum extraction depths of males at all curved flowers, but not at straight flowers. Handling times of females were significantly shorter than handling times of males at the longest artificial flowers for all curvatures, whereas handling times of males were significantly shorter at short, straight, artificial flowers, but only while hover-feeding without a perch. Within each sex, handling times were inversely related to bill length at long flowers for all shapes. Taken together, these performance trade-offs suggest that the long, curved bills of females are adapted for feeding from long, curved flowers, whereas the short bills of males are adapted for hover-feeding from short

  4. FAST Conformational Searches by Balancing Exploration/Exploitation Trade-Offs.

    PubMed

    Zimmerman, Maxwell I; Bowman, Gregory R

    2015-12-08

    Molecular dynamics simulations are a powerful means of understanding conformational changes. However, it is still difficult to simulate biologically relevant time scales without the use of specialized supercomputers. Here, we introduce a goal-oriented sampling method, called fluctuation amplification of specific traits (FAST), for extending the capabilities of commodity hardware. This algorithm rapidly searches conformational space for structures with desired properties by balancing trade-offs between focused searches around promising solutions (exploitation) and trying novel solutions (exploration). FAST was inspired by the hypothesis that many physical properties have an overall gradient in conformational space, akin to the energetic gradients that are known to guide proteins to their folded states. For example, we expect that transitioning from a conformation with a small solvent-accessible surface area to one with a large surface area will require passing through a series of conformations with steadily increasing surface areas. We demonstrate that such gradients are common through retrospective analysis of existing Markov state models (MSMs). Then we design the FAST algorithm to exploit these gradients to find structures with desired properties by (1) recognizing and amplifying structural fluctuations along gradients that optimize a selected physical property whenever possible, (2) overcoming barriers that interrupt these overall gradients, and (3) rerouting to discover alternative paths when faced with insurmountable barriers. To test FAST, we compare its performance to other methods for three common types of problems: (1) identifying unexpected binding pockets, (2) discovering the preferred paths between specific structures, and (3) folding proteins. Our conservative estimate is that FAST outperforms conventional simulations and an adaptive sampling algorithm by at least an order of magnitude. Furthermore, FAST yields both the proper thermodynamics and

  5. Phytoplankton size-diversity mediates an emergent trade-off in ecosystem functioning for rare versus frequent disturbances

    PubMed Central

    Smith, S. Lan; Vallina, Sergio M.; Merico, Agostino

    2016-01-01

    Biodiversity is known to be an important determinant of ecosystem-level functions and processes. Although theories have been proposed to explain the generally positive relationship between, for example, biodiversity and productivity, it remains unclear which mechanisms underlie the observed variations in Biodiversity-Ecosystem Function (BEF) relationships. Using a continuous trait-distribution model for a phytoplankton community of gleaners competing with opportunists, and subjecting it to differing frequencies of disturbance, we find that species selection tends to enhance temporal species complementarity, which is maximised at high disturbance frequency and intermediate functional diversity. This leads to the emergence of a trade-off whereby increasing diversity tends to enhance short-term adaptive capacity under frequent disturbance while diminishing long-term productivity under infrequent disturbance. BEF relationships therefore depend on both disturbance frequency and the timescale of observation. PMID:27748359

  6. Developing an integrated concept for the E-ELT Multi-Object Spectrograph (MOSAIC): design issues and trade-offs

    NASA Astrophysics Data System (ADS)

    Rodrigues, Myriam; Dalton, Gavin; Fitzsimons, Ewan; Chemla, Fanny; Morris, Tim; Hammer, Francois; Puech, Mathieu; Evans, Christopher; Jagourel, Pascal

    2016-08-01

    We present a discussion of the design issues and trade-offs that have been considered in putting together a new concept for MOSAIC,1, 2 the multi-object spectrograph for the E-ELT. MOSAIC aims to address the combined science cases for E-ELT MOS that arose from the earlier studies of the multi-object and multi-adaptive optics instruments (see MOSAIC science requirements in [3]). MOSAIC combines the advantages of a highly-multiplexed instrument targeting single-point objects with one which has a more modest multiplex but can spatially resolve a source with high resolution (IFU). These will span across two wavebands: visible and near-infrared.

  7. Building clinical and organizational resilience to reconcile safety threats, tensions and trade-offs: insights from theory and evidence.

    PubMed

    Jeffs, Lianne; Tregunno, Deborah; MacMillan, Kathleen; Espin, Sherry

    2009-01-01

    Healthcare delivery settings are complex adaptive and tightly coupled, interrelated systems. Within the larger healthcare system, a key subsystem is the "clinical microsystem" level. It is at this level that clinicians are faced with high levels of uncertainty in their daily work - uncertainty that impacts the quality and safety of care that patients receive. The first aim of this paper is to enhance healthcare leaders' understanding of what is currently known about safety threats and strategies to manage the inherent tensions and trade-offs that occur in everyday practice. The second aim is to inform strategies that build clinical and organizational resilience through a multi-level framework derived from the collective theoretical and empirical work. Together, this information can strengthen safety practices throughout healthcare organizations.

  8. Trade-off between allocation to reproductive ramets and rhizome buds in Carex brevicuspis populations along a small-scale elevational gradient.

    PubMed

    Chen, Xin-sheng; Li, Ya-fang; Xie, Yong-hong; Deng, Zheng-miao; Li, Xu; Li, Feng; Hou, Zhi-yong

    2015-07-31

    The trade-off between allocation to sexual and clonal reproduction in clonal plants is influenced by a variety of environmental factors; however, it has rarely been examined under field conditions. In this study, we investigated the trade-off between two modes of reproduction in Carex brevicuspis C. B. Clarke across a small-scale elevational gradient (21-27 m a.s.l.) at the Dongting Lake wetlands, China. The proportion of biomass allocated to and the density of reproductive ramets were higher at low than at intermediate and high elevations. In contrast, the proportion of biomass allocated to and the density of rhizome buds were lower at low than at intermediate and high elevations. Redundancy analysis showed that sexual reproduction was positively correlated with soil moisture content, soil organic matter, total phosphorus, and pH, and negatively correlated with elevation and ramet density. Our findings suggested that allocation to sexual reproduction is favored in disturbed habitats with fertile soils, whereas allocation to vegetative propagation is favored in stable and competitive habitats. Trade-off between allocation to sexual reproduction and vegetative propagation along an elevational gradient might be a reproductive strategy of C. brevicuspis to adapt to the water level fluctuations in wetland habitats.

  9. Daisyworld inhabited with daisies incorporating a seed size/number trade-off: the mechanism of negative feedback on selection from a standpoint of the competition theory.

    PubMed

    Seto, Mayumi; Akagi, Tasuku

    2005-05-21

    We reexamined a Daisyworld model from the traditional view of competition theory. Unlike the original model, white and black daisies in our model incorporate a seeding/germination trade-off against bare ground area without assuming the local temperature reward. As a result, the planetary temperature is automatically regulated by two species if the following conditions are met: (i) the species react equally to an environmental condition, but one can alter the environmental condition in the opposite direction to the other. (ii) that one of the two cannot have both a higher maximal growth rate (mu(max)) and lower half-saturation constant (K) than those of the other. In other words, a pair of phenotypes incorporates a trade-off between quality and number of seeds. We found that the homeostatic regulation can also be reconciled with the adaptive evolution of optimal temperature. The results of simulation imply that biotic environmental feedback can also be maintained when the emergence of polymorphisms (black and white daisies) is closely linked to such a trade-off.

  10. Single amino acid changes in the 6K1-CI region can promote the alternative adaptation of Prunus- and Nicotiana-propagated Plum pox virus C isolates to either host.

    PubMed

    Calvo, María; Malinowski, Tadeusz; García, Juan Antonio

    2014-02-01

    Plum pox virus (PPV) C is one of the less common PPV strains and specifically infects cherry trees in nature. Making use of two PPV-C isolates that display different pathogenicity features, i.e., SwCMp, which had been adapted to Nicotiana species, and BY101, which had been isolated from cherry rootstock L2 (Prunus lannesiana) and propagated only in cherry species, we have generated two infective full-length cDNA clones in order to determine which viral factors are involved in the adaptation to each host. According to our results, the C-P3(PIPO)/6K1/N-CI (cylindrical inclusion) region contains overlapping but not coincident viral determinants involved in symptoms development, local viral amplification, and systemic movement capacity. Amino acid changes in this region promoting the adaptation to N. benthamiana or P. avium have trade-off effects in the alternative host. In both cases, adaptation can be achieved through single amino acid changes in the NIapro protease recognition motif between 6K1 and CI or in nearby sequences. Thus, we hypothesize that the potyvirus polyprotein processing could depend on specific host factors and the adaptation of PPV-C isolates to particular hosts relies on a fine regulation of the proteolytic cleavage of the 6K1-CI junction.

  11. Regulating Interest when Learning Online: Potential Motivation and Performance Trade-Offs

    ERIC Educational Resources Information Center

    Sansone, Carol; Smith, Jessi L.; Thoman, Dustin B.; MacNamara, Atara

    2012-01-01

    Online learning may be particularly sensitive to self-regulatory trade-offs between maintaining interest and performance. Undergraduates in online or on-campus sections of the same course rated strategies used to motivate studying for the first exam, and interest after the first exam and at semester's end. First exam and final class grades were…

  12. Trade-Off Analysis vs. Constrained Optimization with an Economic Control Chart Model

    DTIC Science & Technology

    1994-01-01

    description of this technique can be found in Luenberger (1989) or Reklaitis et al. (1983). Similar to the economic statistical designs, the trade-off...15] Reklaitis , G. V.; Ravindran, A.; and Ragsdell, K. M., Engineering Optimization, Methods and Applications, John Wiley & Sons, New York (1983). [16

  13. A Classroom Exercise to Examine the Trade-off between Mission Capacity and Life Cycle Cost

    ERIC Educational Resources Information Center

    Kang, Keebom; Doerr, Kenneth H.

    2015-01-01

    This article presents a classroom exercise, centered on a simulation that has been used for 4 years in an MBA program to help students develop an understanding of the trade-offs involved in managing capital assets in the public sector. Though often ignored in business schools, "mission" is a key criterion that must be considered when…

  14. Ethical Implications of Validity-vs.-Reliability Trade-Offs in Educational Research

    ERIC Educational Resources Information Center

    Fendler, Lynn

    2016-01-01

    In educational research that calls itself empirical, the relationship between validity and reliability is that of trade-off: the stronger the bases for validity, the weaker the bases for reliability (and vice versa). Validity and reliability are widely regarded as basic criteria for evaluating research; however, there are ethical implications of…

  15. Educational Systems and the Trade-Off between Labor Market Allocation and Equality of Educational Opportunity

    ERIC Educational Resources Information Center

    Bol, Thijs; van de Werfhorst, Herman G.

    2013-01-01

    Educational systems with a high level of tracking and vocational orientation have been shown to improve the allocation of school-leavers in the labor market. However, tracked educational systems are also known to increase inequality of educational opportunity. This presumed trade-off between equality and labor market preparation is clearly rooted…

  16. Neural Trade-Offs between Recognizing and Categorizing Own- and Other-Race Faces.

    PubMed

    Liu, Jiangang; Wang, Zhe; Feng, Lu; Li, Jun; Tian, Jie; Lee, Kang

    2015-08-01

    Behavioral research has suggested a trade-off relationship between individual recognition and race categorization of own- and other-race faces, which is an important behavioral marker of face processing expertise. However, little is known about the neural mechanisms underlying this trade-off. Using functional magnetic resonance imaging (fMRI) methodology, we concurrently asked participants to recognize and categorize own- and other-race faces to examine the neural correlates of this trade-off relationship. We found that for other-race faces, the fusiform face area (FFA) and occipital face area (OFA) responded more to recognition than categorization, whereas for own-race faces, the responses were equal for the 2 tasks. The right superior temporal sulcus (STS) responses were the opposite to those of the FFA and OFA. Further, recognition enhanced the functional connectivity from the right FFA to the right STS, whereas categorization enhanced the functional connectivity from the right OFA to the right STS. The modulatory effects of these 2 couplings were negatively correlated. Our findings suggested that within the core face processing network, although recognizing and categorizing own- and other-race faces activated the same neural substrates, there existed neural trade-offs whereby their activations and functional connectivities were modulated by face race type and task demand due to one's differential processing expertise with own- and other-race faces.

  17. Analysis and trade-off studies of large lightweight mirror structures. [large space telescope

    NASA Technical Reports Server (NTRS)

    Soosaar, K.; Grin, R.; Ayer, F.

    1975-01-01

    A candidate mirror, hexagonally lightweighted, is analyzed under various loadings using as complete a procedure as possible. Successive simplifications are introduced and compared to an original analysis. A model which is a reasonable compromise between accuracy and cost is found and is used for making trade-off studies of the various structural parameters of the lightweighted mirror.

  18. Trade-off between land vehicle antenna cost and gain for satellite mobile communications

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Trade-offs between antenna cost and gain made for nine antennas as a feasibility study for the experimental land mobile satellite system, M-SAT(X) reported. This system is under development by JPL-NASA for a mobile telephone system to be used throughout the continental USA and Alaska. The mobile antenna is a key element in the development of this system.

  19. Neural Trade-Offs between Recognizing and Categorizing Own- and Other-Race Faces

    PubMed Central

    Liu, Jiangang; Wang, Zhe; Feng, Lu; Li, Jun; Tian, Jie; Lee, Kang

    2015-01-01

    Behavioral research has suggested a trade-off relationship between individual recognition and race categorization of own- and other-race faces, which is an important behavioral marker of face processing expertise. However, little is known about the neural mechanisms underlying this trade-off. Using functional magnetic resonance imaging (fMRI) methodology, we concurrently asked participants to recognize and categorize own- and other-race faces to examine the neural correlates of this trade-off relationship. We found that for other-race faces, the fusiform face area (FFA) and occipital face area (OFA) responded more to recognition than categorization, whereas for own-race faces, the responses were equal for the 2 tasks. The right superior temporal sulcus (STS) responses were the opposite to those of the FFA and OFA. Further, recognition enhanced the functional connectivity from the right FFA to the right STS, whereas categorization enhanced the functional connectivity from the right OFA to the right STS. The modulatory effects of these 2 couplings were negatively correlated. Our findings suggested that within the core face processing network, although recognizing and categorizing own- and other-race faces activated the same neural substrates, there existed neural trade-offs whereby their activations and functional connectivities were modulated by face race type and task demand due to one's differential processing expertise with own- and other-race faces. PMID:24591523

  20. Child Care and Work Absences: Trade-Offs by Type of Care

    ERIC Educational Resources Information Center

    Gordon, Rachel A.; Kaestner, Robert; Korenman, Sanders

    2008-01-01

    Parents face a trade-off in the effect of child-care problems on employment. Whereas large settings may increase problems because of child illness, small group care may relate to provider unavailability. Analyzing the NICHD Study of Early Child Care, we find that child-care centers and large family day care lead to mothers' greater work absences…

  1. Trade-off between immunocompetence and growth in magpies: an experimental study.

    PubMed Central

    Soler, Juan José; de Neve, Liesbeth; Pérez-Contreras, Tomás; Soler, Manuel; Sorci, Gabriele

    2003-01-01

    A trade-off between immunity and growth has repeatedly been suggested, mainly based on laboratory and poultry science, but also from experiments where parasitism intensity was manipulated in field bird populations. However, as resource allocation to different activities (or organs) during growth is difficult to manipulate, this trade-off has only been experimentally tested by studying the effects of non-pathogenic antigens. By providing some nestling magpies (Pica pica) with methionine, a sulphur amino acid that specifically enhances T-cell immune response in chickens, we investigated this trade-off by directly affecting allocation of limited resources during growth. Results were in accordance with the hypothetical trade-off because nestlings fed with methionine showed a lower growth rate during the four days of methionine administration, but a larger response when fledglings were challenged with phytohaemagglutinin (a measure of the intensity of T-lymphocyte-mediated immune responsiveness) than control nestlings. Surprisingly, we found that control and experimental nestlings fledged with similar body mass, size and condition, but experimental nestlings suffered less from blood parasites (Haemoproteus) and had fewer lymphocytes (a widely used measure of health status) than control nestlings, suggesting a negative effect of blood parasites or other pathogens on nestling growth. PMID:12614572

  2. Parent–offspring conflict and the genetic trade-offs shaping parental investment

    PubMed Central

    Kölliker, Mathias; Boos, Stefan; Wong, Janine W.Y.; Röllin, Lilian; Stucki, Dimitri; Raveh, Shirley; Wu, Min; Meunier, Joël

    2015-01-01

    The genetic conflict between parents and their offspring is a cornerstone of kin selection theory and the gene-centred view of evolution, but whether it actually occurs in natural systems remains an open question. Conflict operates only if parenting is driven by genetic trade-offs between offspring performance and the parent's ability to raise additional offspring, and its expression critically depends on the shape of these trade-offs. Here we investigate the occurrence and nature of genetic conflict in an insect with maternal care, the earwig Forficula auricularia. Specifically, we test for a direct response to experimental selection on female future reproduction and correlated responses in current offspring survival, developmental rate and growth. The results demonstrate genetic trade-offs that differ in shape before and after hatching. Our study not only provides direct evidence for parent–offspring conflict but also highlights that conflict is not inevitable and critically depends on the genetic trade-offs shaping parental investment. PMID:25880586

  3. An Education Freedom Index: Why, Key Determinants, Component Weights, and Trade-Offs

    ERIC Educational Resources Information Center

    Merrifield, John

    2011-01-01

    Freedom of any kind has intrinsic value, and education freedom is controversial, in need of empirical assessment of possible and likely trade-offs between freedom from state control and social goals such as equity and cohesion. Without a reasonable empirical measure of education freedom we can only cite the controversies and choose sides. The…

  4. Site-specific trade-offs of harvesting cereal residues as biofuel feedstocks

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cereal residues are considered an important feedstock for future biofuel production. Harvesting cereal residues, however, could lead to substantial soil degradation. Our objective was to evaluate trade-offs associated with harvesting straw including impacts on soil erosion and quality, soil organic ...

  5. The tolerance–fecundity trade-off and the maintenance of diversity in seed size

    PubMed Central

    Muller-Landau, Helene C.

    2010-01-01

    Seed size commonly varies by five to six orders of magnitude among coexisting plant species, a pattern ecologists have long sought to explain. Because seed size trades off with seed number, small-seeded species clearly have the advantage in fecundity, but what is the countervailing advantage of large seeds? Higher competitive ability combined with strong competitive asymmetry can in theory allow coexistence through a competition–colonization trade-off, but empirical evidence is inconsistent with this mechanism. Instead, the key advantage of large seeds appears to be their tolerance of stresses such as shade or drought that are present in some but not all regeneration sites. Here I present a simple, analytically tractable model of species coexistence in heterogeneous habitats through a tolerance–fecundity trade-off. Under this mechanism, the more tolerant species win all of the more stressful regeneration sites and some of those that are less stressful, whereas the more fecund species win most but not all of the less stressful sites. The tolerance–fecundity trade-off enables stable coexistence of large numbers of species in models with and without seed limitation. The tolerance–fecundity mechanism provides an excellent explanation for the maintenance of diversity of seed size within plant communities and also suggests new hypotheses for coexistence in animal and microbial communities. PMID:20160078

  6. GARBAGE: A Card Game That Simulates the Trade-Off between Competition and Concern.

    ERIC Educational Resources Information Center

    Thiagarajan, Sivasailam

    1991-01-01

    Describes a simulation card game involved with the dumping of hazardous wastes that was designed to explore the trade-off between industrial competition and social concern. Steps of play are described for the game, which is called GARBAGE, and debriefing techniques are suggested, including an affective phase and a cognitive phase. (LRW)

  7. Environmental trade-offs of tunnels vs cut-and-cover subways

    USGS Publications Warehouse

    Walton, M.

    1978-01-01

    Heavy construction projects in cities entail two kinds of cost - internal cost, which can be defined in terms of payments from one set of parties to another, and external cost, which is the cost borne by the community at large as the result of disutilities entailed in construction and operation. Environmental trade-offs involve external costs, which are commonly difficult to measure. Cut-and-cover subway construction probably entails higher external and internal cost than deep tunnel construction in many urban geological environments, but uncertainty concerning the costs and environmental trade-offs of tunneling leads to limited and timid use of tunneling by American designers. Thus uncertainty becomes a major trade-off which works against tunneling. The reverse is true in Sweden after nearly 30 years of subway construction. Econometric methods for measuring external costs exist in principle, but are limited in application. Economic theory based on market pressure does not address the real problem of urban environmental trade-offs. Nevertheless, the problem of uncertainty can be addressed by comparative studies of estimated and as-built costs of cut-and-cover vs tunnel projects and a review of environmental issues associated with such construction. Such a study would benefit the underground construction industry and the design of transportation systems. It would also help solve an aspect of the urban problem. ?? 1978.

  8. Valuing trade-offs of river ecosystem services in large hydropower development in Tibet, China

    NASA Astrophysics Data System (ADS)

    Yu, B.; Xu, L.

    2015-12-01

    Hydropower development can be considered as a kind of trade-offs of ecosystem services generated by human activity for their economic and energy demand, because it can increase some river ecosystem services but decrease others. In this context, an ecosystem service trade-off framework in hydropower development was proposed in this paper. It aims to identify the ecological cost of river ecosystem and serve for the ecological compensation during hydropower development, for the hydropower services cannot completely replace the regulating services of river ecosystem. The valuing trade-offs framework was integrated by the influenced ecosystem services identification and ecosystem services valuation, through ecological monitoring and ecological economic methods, respectively. With a case study of Pondo hydropower project in Tibet, China, the valuing trade-offs of river ecosystem services in large hydropower development was illustrated. The typical ecological factors including water, sediment and soil were analyzed in this study to identify the altered river ecosystem services by Pondo hydropower project. Through the field monitoring and valuation, the results showed that the Lhasa River ecosystem services value could be changed annually by Pondo hydropower project with the increment of 5.7E+8CNY, and decrement of 5.1E+7CNY. The ecological compensation for river ecosystem should be focus on water and soil conservation, reservoir dredging and tributaries habitat protection.

  9. University Efficiency: Complementariness versus Trade-Off between Teaching, Research and Administrative Activities

    ERIC Educational Resources Information Center

    Sellers-Rubio, Ricardo; Mas-Ruiz, Francisco J.; Casado-Diaz, Ana B.

    2010-01-01

    University managers should be aware of the importance that efficiency has for their own universities, orientating their actions towards research and teaching excellence. This study estimates teaching and research efficiency of the different departments of a university and tests the complementariness versus trade-off between them. The results…

  10. On the origins of extreme mycorrhizal specificity in the Monotropoideae (Ericaceae): performance trade-offs during seed germination and seedling development.

    PubMed

    Bidartondo, M I; Bruns, T D

    2005-04-01

    Fungal-induced seed germination is a phenomenon characteristic of mycorrhizal plants that produce dust-like seeds with only minimal nutritional reserves. In such systems, fungi trigger germination and/or subsidize development. We studied mycorrhizal germination in relation to mycorrhizal specificity in the Monotropoideae, a lineage of dust-seeded non-photosynthetic plants that are dependent upon ectomycorrhizal fungi of forest trees. A total of 1695 seed packets, each containing two to five compartments with seeds from different sources, were buried for up to 2 years near known ectomycorrhizal fungi in six different native forest locations. Upon harvest, seedlings were analysed by cultivation-independent molecular methods to identify their mycorrhizal fungi. We report that (i) germination is only induced by the same fungus that associates with mature plants or by closely related congeners; (ii) seedlings associated with the latter fungi develop less than those associated with maternal fungal species in most settings; and (iii) exceptions to this pattern occur in allopatric settings, where novel plant-fungal associations can result in the greatest seedling development. We interpret these results as evidence of performance trade-offs between breadth of host range and rate of development. We propose that in conjunction with host-derived germination cues, performance trade-offs can explain the extreme mycorrhizal specificity observed at maturity. The allopatric exceptions support the idea that performance trade-offs may be based on a coevolutionary arms race and that host range can be broadened most readily when naive fungal hosts are encountered in novel settings.

  11. Green trees for greenhouse gases: a fair trade-off?

    PubMed

    Schmidt, C W

    2001-03-01

    While forests retain carbon in plants, detritus, and soils, utility companies spew it into the air as carbon dioxide, the main greenhouse gas behind global warming. Industrial carbon dioxide emissions aren't currently regulated by federal law, but a number of companies are trying to address the problem voluntarily by launching carbon sequestration programs in heavily forested countries, where carbon is contained in so-called sinks. But the November 2000 meeting of the Kyoto Protocol delegates in The Hague collapsed over the issue of the acceptability of carbon sinks as a source of carbon pollution credits, delivering what many see as a deathblow to the concept. At issue are a host of ecological and statistical questions, differing local land use practices, cultural factors, issues of verifiability, and even disagreement over definitions of basic terms such as "forest" Kyoto negotiators are gearing up for another round of discussions in Bonn in May 2001, and it is likely that the continuing debate over carbon sinks will dominate the agenda.

  12. The trade-off between safety and efficiency in hydraulic architecture in 31 woody species in a karst area.

    PubMed

    Fan, Da-Yong; Jie, Sheng-Lin; Liu, Chang-Cheng; Zhang, Xiang-Ying; Xu, Xin-Wu; Zhang, Shou-Ren; Xie, Zong-Qiang

    2011-08-01

    Karst topography is a special landscape shaped by the dissolution of one or more layers of soluble bedrock, usually carbonate rock such as limestone or dolomite. Due to subterranean drainage, overland flow, extraction of water by plants and evapotranspiration, there may be very limited surface water. The hydraulic architecture that plants use to adapt to karst topography is very interesting, but few systematic reports exist. The karst area in southwestern China is unique when compared with other karst areas at similar latitudes, because of its abundant precipitation, with rainfall concentrated in the growing season. In theory, resistance to water-stress-induced cavitation via air seeding should be accompanied by decreased pore hydraulic conductivity and stem hydraulic conductivity. However, evidence for such trade-offs across species is ambiguous. We measured the hydraulic structure and foliar stable carbon isotope ratios of 31 karst woody plants at three locations in Guizhou Province, China, to evaluate the functional coordination between resistance to cavitation and specific conductivity. We also applied phylogenetically independent contrast (PIC) analysis in situations where the inter-species correlations of functional traits may be biased on the potential similarity of closely related species. The average xylem tension measurement, at which 50% of hydraulic conductivity of the plants was lost (Ψ(50)), was only -1.27 MPa. Stem Ψ(50) was positively associated with specific conductance (K(s)) (P < 0.05) and leaf specific conductance (K(l)) (P < 0.05). However, the PIC correlation for both relationships was not statistically significant. δ(13)C was positively related to K(l) in both the traditional cross-species correlation analysis and the corresponding PIC correlations (P < 0.05). The Huber value (sapwood area:leaf area ratio) was negatively correlated with K(s) in both the traditional cross-species correlation and the corresponding PIC

  13. Local adaptation of plant viruses: lessons from experimental evolution.

    PubMed

    Elena, Santiago F

    2016-09-09

    For multihost pathogens, adaptation to multiple hosts has important implications for both applied and basic research. At the applied level, it is one of the main factors determining the probability and severity of emerging disease outbreaks. At the basic level, it is thought to be a key mechanism for the maintenance of genetic diversity both in host and pathogen species. In recent years, a number of evolution experiments have assessed the fate of plant virus populations replicating within and adapting to one single or to multiple hosts species. A first group of these experiments tackled the existence of trade-offs in fitness and virulence for viruses evolving either within a single hosts species or alternating between two different host species. A second set of experiments explored the role of genetic variability in susceptibility and resistance to infection among individuals from the same host species in the extent of virus local adaptation and of virulence. In general, when a single host species or genotype is available, these experiments show that local adaptation takes place, often but not always associated with a fitness trade-off. However, alternating between different host species or infecting resistant host genotypes may select for generalist viruses that experience no fitness cost. Therefore, the expected cost of generalism, arising from antagonistic pleiotropy and other genetic mechanisms generating fitness trade-offs between hosts, could not be generalized and strongly depend on the characteristics of each particular pathosystem. At the genomic level, these studies show pervasive convergent molecular evolution, suggesting that the number of accessible molecular pathways leading to adaptation to novel hosts is limited.

  14. Trade-offs between predation risk and forage differ between migrant strategies in a migratory ungulate.

    PubMed

    Hebblewhite, Mark; Merrill, Evelyn H

    2009-12-01

    Trade-offs between predation risk and forage fundamentally drive resource selection by animals. Among migratory ungulates, trade-offs can occur at large spatial scales through migration, which allows an "escape" from predation, but trade-offs can also occur at finer spatial scales. Previous authors suggest that ungulates will avoid predation risk at the largest scale, although few studies have examined multi-scale trade-offs to test for the relative benefits of risk avoidance across scales. Building on previously developed spatial models of forage and wolf predation risk, we tested for trade-offs at the broad landscape scale and at a finer, within-home-range scale for migratory and non-migratory resident elk (Cervus elaphus) during summer in the Canadian Rockies in Banff National Park (BNP) and adjacent Alberta, Canada. Migration reduced exposure to wolf predation risk by 70% relative to residents at the landscape scale; at the fine scale, migrants used areas that were, on average, 6% higher in forage digestibility. In contrast, by forgoing migration, resident elk were exposed to higher predation risk, but they reduced predation risk at fine scales to only 15% higher than migrants by using areas close to human activity, which wolves avoided. Thus, residents paid for trying to avoid predation risk with lower forage quality. Residents may have been able to compensate, however, by using areas of abundant forage close to human activity where they may have been able to forage more selectively while avoiding predation risk. Human activity effectively decoupled the positive correlation between high forage quality and wolf predation, providing an effective alternate strategy for residents, similar to recent findings in other systems. Although ungulates appear capable of balancing risk and forage at different spatial scales, risk avoidance at large landscape scales may be more effective in the absence of human-caused refugia from predation.

  15. Novel players fine-tune plant trade-offs.

    PubMed

    Gimenez-Ibanez, Selena; Boter, Marta; Solano, Roberto

    2015-01-01

    Jasmonates (JAs) are essential signalling molecules that co-ordinate the plant response to biotic and abiotic challenges, as well as co-ordinating several developmental processes. Huge progress has been made over the last decade in understanding the components and mechanisms that govern JA perception and signalling. The bioactive form of the hormone, (+)-7-iso-jasmonyl-L-isoleucine (JA-Ile), is perceived by the COI1-JAZ co-receptor complex. JASMONATE ZIM DOMAIN (JAZ) proteins also act as direct repressors of transcriptional activators such as MYC2. In the emerging picture of JA-Ile perception and signalling, COI1 operates as an E3 ubiquitin ligase that upon binding of JA-Ile targets JAZ repressors for degradation by the 26S proteasome, thereby derepressing transcription factors such as MYC2, which in turn activate JA-Ile-dependent transcriptional reprogramming. It is noteworthy that MYCs and different spliced variants of the JAZ proteins are involved in a negative regulatory feedback loop, which suggests a model that rapidly turns the transcriptional JA-Ile responses on and off and thereby avoids a detrimental overactivation of the pathway. This chapter highlights the most recent advances in our understanding of JA-Ile signalling, focusing on the latest repertoire of new targets of JAZ proteins to control different sets of JA-Ile-mediated responses, novel mechanisms of negative regulation of JA-Ile signalling, and hormonal cross-talk at the molecular level that ultimately determines plant adaptability and survival.

  16. Organizing principles underlying microorganism's growth-robustness trade-off.

    PubMed

    Bolli, Alessandro; Salvador, Armindo

    2014-10-01

    Growth Robustness Reciprocity (GRR) is an intriguing microbial manifestation: the impairment of microorganism's growth enhances their ability to resist acute stresses, and vice-versa. This is caused by regulatory interactions that determine higher expression of protection mechanisms in response to low growth rates. But because such regulatory mechanisms are species-specific, GRR must result from convergent evolution. Why does natural selection favor such an outcome? We used mathematical models of optimal cellular resource allocation to identify the general principles underlying GRR. Non-linear optimization allowed to predict allocation patterns of biosynthetic resources (ribosomes devoted to the synthesis of each cell component) that maximize growth. These models predict the down-regulation of stress defenses under high substrate availabilities and low stress levels. Under these conditions, stress tolerance ensues from growth-related damage dilution: the higher the substrate availability, the fastest the dilution of damaged proteins by newly synthesized proteins, the lower the accumulation of damaged components into the cell. In turn, under low substrate availability growth is too slow for effective damage dilution, and the expression of the defenses up to some optimal level then increases growth. As a consequence, slow-growing cells are pre-adapted to withstand acute stresses. Therefore, the observed negative correlation between growth and stress tolerance can be explained as a consequence of optimal resource allocation for maximal growth. We acknowledge fellowship SFRH/BPD/90065/2012 and grants PEst-C/SAU/LA0001/2013-2014 and FCOMP-01-0124-FEDER-020978 financed by FEDER through the "Programa Operacional Factores de Competitividade, COMPETE" and by national funds through "FCT, Fundação para a Ciência e a Tecnologia" (project PTDC/QUI-BIQ/119657/2010).

  17. Speed accuracy trade-off under response deadlines

    PubMed Central

    Karşılar, Hakan; Simen, Patrick; Papadakis, Samantha; Balcı, Fuat

    2014-01-01

    Perceptual decision making has been successfully modeled as a process of evidence accumulation up to a threshold. In order to maximize the rewards earned for correct responses in tasks with response deadlines, participants should collapse decision thresholds dynamically during each trial so that a decision is reached before the deadline. This strategy ensures on-time responding, though at the cost of reduced accuracy, since slower decisions are based on lower thresholds and less net evidence later in a trial (compared to a constant threshold). Frazier and Yu (2008) showed that the normative rate of threshold reduction depends on deadline delays and on participants' uncertainty about these delays. Participants should start collapsing decision thresholds earlier when making decisions under shorter deadlines (for a given level of timing uncertainty) or when timing uncertainty is higher (for a given deadline). We tested these predictions using human participants in a random dot motion discrimination task. Each participant was tested in free-response, short deadline (800 ms), and long deadline conditions (1000 ms). Contrary to optimal-performance predictions, the resulting empirical function relating accuracy to response time (RT) in deadline conditions did not decline to chance level near the deadline; nor did the slight decline we typically observed relate to measures of endogenous timing uncertainty. Further, although this function did decline slightly with increasing RT, the decline was explainable by the best-fitting parameterization of Ratcliff's diffusion model (Ratcliff, 1978), whose parameters are constant within trials. Our findings suggest that at the very least, typical decision durations are too short for participants to adapt decision parameters within trials. PMID:25177265

  18. Dopamine drives Drosophila sechellia adaptation to its toxic host.

    PubMed

    Lavista-Llanos, Sofía; Svatoš, Aleš; Kai, Marco; Riemensperger, Thomas; Birman, Serge; Stensmyr, Marcus C; Hansson, Bill S

    2014-12-09

    Many insect species are host-obligate specialists. The evolutionary mechanism driving the adaptation of a species to a toxic host is, however, intriguing. We analyzed the tight association of Drosophila sechellia to its sole host, the fruit of Morinda citrifolia, which is toxic to other members of the melanogaster species group. Molecular polymorphisms in the dopamine regulatory protein Catsup cause infertility in D. sechellia due to maternal arrest of oogenesis. In its natural host, the fruit compensates for the impaired maternal dopamine metabolism with the precursor l-DOPA, resuming oogenesis and stimulating egg production. l-DOPA present in morinda additionally increases the size of D. sechellia eggs, what in turn enhances early fitness. We argue that the need of l-DOPA for successful reproduction has driven D. sechellia to become an M. citrifolia obligate specialist. This study illustrates how an insect's dopaminergic system can sustain ecological adaptations by modulating ontogenesis and development.

  19. Modelling the evolution of common cuckoo host-races: speciation or genetic swamping?

    PubMed

    Krüger, O; Kolss, M

    2013-11-01

    Co-evolutionary arms races have provided clear evidence for evolutionary change, especially in host-parasite systems. The evolution of host-specific races in the common cuckoo (Cuculus canorus), however, is also an example where sexual conflict influences the outcome. Cuckoo females benefit from better adaptation to overcome host defences, whereas cuckoo males face a trade-off between the benefits of better adaptation to a host and the benefits of multiple mating with females from other host-races. The outcome of this trade-off might be genetic differentiation or prevention of it by genetic swamping. We use a simulation model to test which outcome is more likely with three sympatric cuckoo host-races. We assume a cost for cuckoo chicks that express a host adaptation allele not suited to their foster host species and that cuckoo males that switch to another host-race experience either a fitness benefit or cost. Over most of the parameter space, cuckoo male host-race fidelity increases significantly with time, and gene flow between host-races ceases within a few thousand to a hundred thousand generations. Our results hence support the idea that common cuckoo host-races might be in the incipient stages of speciation.

  20. Pleiotropic effects of juvenile hormone in ant queens and the escape from the reproduction-immunocompetence trade-off.

    PubMed

    Pamminger, Tobias; Treanor, David; Hughes, William O H

    2016-01-13

    The ubiquitous trade-off between survival and costly reproduction is one of the most fundamental constraints governing life-history evolution. In numerous animals, gonadotropic hormones antagonistically suppressing immunocompetence cause this trade-off. The queens of many social insects defy the reproduction-survival trade-off, achieving both an extraordinarily long life and high reproductive output, but how they achieve this is unknown. Here we show experimentally, by integrating quantification of gene expression, physiology and behaviour, that the long-lived queens of the ant Lasius niger have escaped the reproduction-immunocompetence trade-off by decoupling the effects of a key endocrine regulator of fertility and immunocompetence in solitary insects, juvenile hormone (JH). This modification of the regulatory architecture enables queens to sustain a high reproductive output without elevated JH titres and suppressed immunocompetence, providing an escape from the reproduction-immunocompetence trade-off that may contribute to the extraordinary lifespan of many social insect queens.

  1. Evolution of intrinsic growth and energy acquisition rates. I. Trade-offs with swimming performance in Menidia menidia.

    PubMed

    Billerbeck, J M; Lankford, T E; Conover, D O

    2001-09-01

    Latitudinal populations of the Atlantic silverside, Menidia menidia, show substantial genetic variation in rates of energy acquistion and allocation. Reared in common environments, silversides from northern latitudes consume more food, grow faster and more efficiently, store more energy, and produce greater quantities of eggs than their southern conspecifics. The persistence of seemingly inferior southern genotypes in the face of ostensibly superior northern genotypes suggest that there are hidden evolutionary trade-offs associated with these elevated acquisition and allocation rates. We tested the hypothesis that rapid growth and high levels of food consumption trade-off against locomotory performance in M. menidia. We compared both aerobic (prolonged and endurance) and anaerobic (burst) swimming capacities between intrinsically fast-growing fish from the north (Nova Scotia, NS) and intrinsically slow-growing fish from the south (South Carolina, SC) and between growth-manipulated phenotypes within each population. We also compared swimming speeds and endurance between fasted and recently fed fish within populations. Maximum prolonged and burst swimming speeds of NS fish were significantly lower than those of SC fish, and swimming speeds of fast-growing phenotypes were lower than those of slow-growing phenotypes within populations. Fed fish had lower burst speeds and less endurance than fasted fish from the same population. Thus, high rates of growth and the consumption of large meals clearly diminish swimming performance, which likely increases vulnerability to predation and decreases survival and relative fitness. The submaximal growth rate of southern M. menidia appears to be adaptive, resulting from balancing selection on rates of somatic growth.

  2. Association genetics, geography and ecophysiology link stomatal patterning in Populus trichocarpa with carbon gain and disease resistance trade-offs.

    PubMed

    McKown, Athena D; Guy, Robert D; Quamme, Linda; Klápště, Jaroslav; La Mantia, Jonathan; Constabel, C P; El-Kassaby, Yousry A; Hamelin, Richard C; Zifkin, Michael; Azam, M S

    2014-12-01

    Stomata are essential for diffusive entry of gases to support photosynthesis, but may also expose internal leaf tissues to pathogens. To uncover trade-offs in range-wide adaptation relating to stomata, we investigated the underlying genetics of stomatal traits and linked variability in these traits with geoclimate, ecophysiology, condensed foliar tannins and pathogen susceptibility in black cottonwood (Populus trichocarpa). Upper (adaxial) and lower (abaxial) leaf stomatal traits were measured from 454 accessions collected throughout much of the species range. We calculated broad-sense heritability (H(2) ) of stomatal traits and, using SNP data from a 34K Populus SNP array, performed a genome-wide association studies (GWAS) to uncover genes underlying stomatal trait variation. H(2) values for stomatal traits were moderate (average H(2) = 0.33). GWAS identified genes associated primarily with adaxial stomata, including polarity genes (PHABULOSA), stomatal development genes (BRASSINOSTEROID-INSENSITIVE 2) and disease/wound-response genes (GLUTAMATE-CYSTEINE LIGASE). Stomatal traits correlated with latitude, gas exchange, condensed tannins and leaf rust (Melampsora) infection. Latitudinal trends of greater adaxial stomata numbers and guard cell pore size corresponded with higher stomatal conductance (gs ) and photosynthesis (Amax ), faster shoot elongation, lower foliar tannins and greater Melampsora susceptibility. This suggests an evolutionary trade-off related to differing selection pressures across the species range. In northern environments, more adaxial stomata and larger pore sizes reflect selection for rapid carbon gain and growth. By contrast, southern genotypes have fewer adaxial stomata, smaller pore sizes and higher levels of condensed tannins, possibly linked to greater pressure from natural leaf pathogens, which are less significant in northern ecosystems.

  3. Trade-offs between predation risk and growth benefits in the copepod Eurytemora affinis with contrasting pigmentation.

    PubMed

    Gorokhova, Elena; Lehtiniemi, Maiju; Motwani, Nisha H

    2013-01-01

    Intraspecific variation in body pigmentation is an ecologically and evolutionary important trait; however, the pigmentation related trade-offs in marine zooplankton are poorly understood. We tested the effects of intrapopulation phenotypic variation in the pigmentation of the copepod Eurytemora affinis on predation risk, foraging, growth, metabolic activity and antioxidant capacity. Using pigmented and unpigmented specimens, we compared (1) predation and selectivity by the invertebrate predator Cercopagis pengoi, (2) feeding activity of the copepods measured as grazing rate in experiments and gut fluorescence in situ, (3) metabolic activity assayed as RNA:DNA ratio in both experimental and field-collected copepods, (4) reproductive output estimated as egg ratio in the population, and (5) total antioxidant capacity. Moreover, mitochondrial DNA (mtDNA) COI gene variation was analysed. The pigmented individuals were at higher predation risk as evidenced by significantly higher predation rate by C. pengoi on pigmented individuals and positive selection by the predator fed pigmented and unpigmented copepods in a mixture. However, the antioxidant capacity, RNA:DNA and egg ratio values were significantly higher in the pigmented copepods, whereas neither feeding rate nor gut fluorescence differed between the pigmented and unpigmented copepods. The phenotypic variation in pigmentation was not associated with any specific mtDNA genotype. Together, these results support the metabolic stimulation hypothesis to explain variation in E. affinis pigmentation, which translates into beneficial increase in growth via enhanced metabolism and antioxidant protective capacity, together with disadvantageous increase in predation risk. We also suggest an alternative mechanism for the metabolic stimulation via elevated antioxidant levels as a primary means of increasing metabolism without the increase in heat absorbance. The observed trade-offs are relevant to evolutionary mechanisms

  4. Trade-Offs between Predation Risk and Growth Benefits in the Copepod Eurytemora affinis with Contrasting Pigmentation

    PubMed Central

    Gorokhova, Elena; Lehtiniemi, Maiju; Motwani, Nisha H.

    2013-01-01

    Intraspecific variation in body pigmentation is an ecologically and evolutionary important trait; however, the pigmentation related trade-offs in marine zooplankton are poorly understood. We tested the effects of intrapopulation phenotypic variation in the pigmentation of the copepod Eurytemora affinis on predation risk, foraging, growth, metabolic activity and antioxidant capacity. Using pigmented and unpigmented specimens, we compared (1) predation and selectivity by the invertebrate predator Cercopagis pengoi, (2) feeding activity of the copepods measured as grazing rate in experiments and gut fluorescence in situ, (3) metabolic activity assayed as RNA:DNA ratio in both experimental and field-collected copepods, (4) reproductive output estimated as egg ratio in the population, and (5) total antioxidant capacity. Moreover, mitochondrial DNA (mtDNA) COI gene variation was analysed. The pigmented individuals were at higher predation risk as evidenced by significantly higher predation rate by C. pengoi on pigmented individuals and positive selection by the predator fed pigmented and unpigmented copepods in a mixture. However, the antioxidant capacity, RNA:DNA and egg ratio values were significantly higher in the pigmented copepods, whereas neither feeding rate nor gut fluorescence differed between the pigmented and unpigmented copepods. The phenotypic variation in pigmentation was not associated with any specific mtDNA genotype. Together, these results support the metabolic stimulation hypothesis to explain variation in E. affinis pigmentation, which translates into beneficial increase in growth via enhanced metabolism and antioxidant protective capacity, together with disadvantageous increase in predation risk. We also suggest an alternative mechanism for the metabolic stimulation via elevated antioxidant levels as a primary means of increasing metabolism without the increase in heat absorbance. The observed trade-offs are relevant to evolutionary mechanisms

  5. Metabolic adaptation of Chlamydia trachomatis to mammalian host cells.

    PubMed

    Mehlitz, Adrian; Eylert, Eva; Huber, Claudia; Lindner, Buko; Vollmuth, Nadine; Karunakaran, Karthika; Goebel, Werner; Eisenreich, Wolfgang; Rudel, Thomas

    2017-03-01

    Metabolic adaptation is a key feature for the virulence of pathogenic intracellular bacteria. Nevertheless, little is known about the pathways in adapting the bacterial metabolism to multiple carbon sources available from the host cell. To analyze the metabolic adaptation of the obligate intracellular human pathogen Chlamydia trachomatis, we labeled infected HeLa or Caco-2 cells with (13) C-marked glucose, glutamine, malate or a mix of amino acids as tracers. Comparative GC-MS-based isotopologue analysis of protein-derived amino acids from the host cell and the bacterial fraction showed that C. trachomatis efficiently imported amino acids from the host cell for protein biosynthesis. FT-ICR-MS analyses also demonstrated that label from exogenous (13) C-glucose was efficiently shuffled into chlamydial lipopolysaccharide probably via glucose 6-phosphate of the host cell. Minor fractions of bacterial Ala, Asp, and Glu were made de novo probably using dicarboxylates from the citrate cycle of the host cell. Indeed, exogenous (13) C-malate was efficiently taken up by C. trachomatis and metabolized into fumarate and succinate when the bacteria were kept in axenic medium containing the malate tracer. Together, the data indicate co-substrate usage of intracellular C. trachomatis in a stream-lined bipartite metabolism with host cell-supplied amino acids for protein biosynthesis, host cell-provided glucose 6-phosphate for cell wall biosynthesis, and, to some extent, one or more host cell-derived dicarboxylates, e.g. malate, feeding the partial TCA cycle of the bacterium. The latter flux could also support the biosynthesis of meso-2,6-diaminopimelate required for the formation of chlamydial peptidoglycan.

  6. Evolutionary implications of the adaptation to different immune systems in a parasite with a complex life cycle.

    PubMed

    Hammerschmidt, Katrin; Kurtz, Joachim

    2005-12-07

    Many diseases are caused by parasites with complex life cycles that involve several hosts. If parasites cope better with only one of the different types of immune systems of their host species, we might expect a trade-off in parasite performance in the different hosts, that likely influences the evolution of virulence. We tested this hypothesis in a naturally co-evolving host-parasite system consisting of the tapeworm Schistocephalus solidus and its intermediate hosts, a copepod, Macrocyclops albidus, and the three-spined stickleback Gasterosteus aculeatus. We did not find a trade-off between infection success in the two hosts. Rather, tapeworms seem to trade-off adaptation towards different parts of their hosts' immune systems. Worm sibships that performed better in the invertebrate host also seem to be able to evade detection by the fish innate defence systems, i.e. induce lower levels of activation of innate immune components. These worm variants were less harmful for the fish host likely due to reduced costs of an activated innate immune system. These findings substantiate the impact of both hosts' immune systems on parasite performance and virulence.

  7. The transcriptional regulator BZR1 mediates trade-off between plant innate immunity and growth

    PubMed Central

    Lozano-Durán, Rosa; Macho, Alberto P; Boutrot, Freddy; Segonzac, Cécile; Somssich, Imre E; Zipfel, Cyril

    2013-01-01

    The molecular mechanisms underlying the trade-off between plant innate immunity and steroid-mediated growth are controversial. Here, we report that activation of the transcription factor BZR1 is required and sufficient for suppression of immune signaling by brassinosteroids (BR). BZR1 induces the expression of several WRKY transcription factors that negatively control early immune responses. In addition, BZR1 associates with WRKY40 to mediate the antagonism between BR and immune signaling. We reveal that BZR1-mediated inhibition of immunity is particularly relevant when plant fast growth is required, such as during etiolation. Thus, BZR1 acts as an important regulator mediating the trade-off between growth and immunity upon integration of environmental cues. DOI: http://dx.doi.org/10.7554/eLife.00983.001 PMID:24381244

  8. The transcriptional regulator BZR1 mediates trade-off between plant innate immunity and growth.

    PubMed

    Lozano-Durán, Rosa; Macho, Alberto P; Boutrot, Freddy; Segonzac, Cécile; Somssich, Imre E; Zipfel, Cyril

    2013-12-31

    The molecular mechanisms underlying the trade-off between plant innate immunity and steroid-mediated growth are controversial. Here, we report that activation of the transcription factor BZR1 is required and sufficient for suppression of immune signaling by brassinosteroids (BR). BZR1 induces the expression of several WRKY transcription factors that negatively control early immune responses. In addition, BZR1 associates with WRKY40 to mediate the antagonism between BR and immune signaling. We reveal that BZR1-mediated inhibition of immunity is particularly relevant when plant fast growth is required, such as during etiolation. Thus, BZR1 acts as an important regulator mediating the trade-off between growth and immunity upon integration of environmental cues. DOI: http://dx.doi.org/10.7554/eLife.00983.001.

  9. Development of trade-off equations for EnergyStar windows

    SciTech Connect

    Huang, Joe; Mitchell, Robin; Selkowitz, Steve; Arasteh, Dariush; Clear, Bob

    2004-06-09

    The authors explore the feasibility of adding a performance option to DOE's EnergyStar{copyright} Windows program whereby windows of differing U-factors and SHGCs can qualify so long as they have equivalent annual energy performance. An iterative simulation procedure is used to calculate trade-off equations giving the change in SHGC needed to compensate for a change in U-factor. Of the four EnergyStar{copyright} Window climate zones, trade-off equations are possible only in the Northern and Southern zones. In the North/Central and South/Central zones, equations are not possible either because of large intrazone climate variations or the current SHGC requirements are already near optimum.

  10. Some trade-offs: culture, education, and economic progress on Federal Indian reservations

    SciTech Connect

    Murray, S.; Tweeten, L.

    1981-04-01

    Federal policies have not been consistent about whether to assimilate American Indians into the larger culture or whether to preserve the reservations. Single-equation, eight-variable regression models are developed to analyze per-capita income and labor-force participation on the reservation. The variables include educational levels, retention of Indian culture, the ratio of tribal to government employees on the reservation, the percentage of labor in agriculture relative to professional jobs, home ownership, automobile ownership, and marriage. A trade-off between education and culture retention is shown for both models in relation to income level. Indian residents who remain on reservations accept lower incomes in order to retain their culture, although continued government investment in reservation programs will raise per-capita income. Educational programs that emphasize traditional culture and cognitive skills can offset the trade-off dilemma of economic development. (DCK)

  11. Trade-offs between robustness and small-world effect in complex networks

    PubMed Central

    Peng, Guan-Sheng; Tan, Suo-Yi; Wu, Jun; Holme, Petter

    2016-01-01

    Robustness and small-world effect are two crucial structural features of complex networks and have attracted increasing attention. However, little is known about the relation between them. Here we demonstrate that, there is a conflicting relation between robustness and small-world effect for a given degree sequence. We suggest that the robustness-oriented optimization will weaken the small-world effect and vice versa. Then, we propose a multi-objective trade-off optimization model and develop a heuristic algorithm to obtain the optimal trade-off topology for robustness and small-world effect. We show that the optimal network topology exhibits a pronounced core-periphery structure and investigate the structural properties of the optimized networks in detail. PMID:27853301

  12. Evaluation of trade-offs in costs and environmental impacts for returnable packaging implementation

    NASA Astrophysics Data System (ADS)

    Jarupan, Lerpong; Kamarthi, Sagar V.; Gupta, Surendra M.

    2004-02-01

    The main thrust of returnable packaging these days is to provide logistical services through transportation and distribution of products and be environmentally friendly. Returnable packaging and reverse logistics concepts have converged to mitigate the adverse effect of packaging materials entering the solid waste stream. Returnable packaging must be designed by considering the trade-offs between costs and environmental impact to satisfy manufacturers and environmentalists alike. The cost of returnable packaging entails such items as materials, manufacturing, collection, storage and disposal. Environmental impacts are explicitly linked with solid waste, air pollution, and water pollution. This paper presents a multi-criteria evaluation technique to assist decision-makers for evaluating the trade-offs in costs and environmental impact during the returnable packaging design process. The proposed evaluation technique involves a combination of multiple objective integer linear programming and analytic hierarchy process. A numerical example is used to illustrate the methodology.

  13. Definition and trade-off of low power arcjet missions and system parameters

    NASA Astrophysics Data System (ADS)

    Deininger, W. D.; de Toma, E.

    1992-08-01

    The first phase of activities of an ongoing systems study are described where missions are identified and evaluated based on where a low power arcjet propulsion subsystem can provide improved performance with respect to a monopropellant chemical subsystem. Mission requirements including delta-V, onboard spacecraft power and propellant mass are discussed. A trade-off analysis is conducted to examine the mission options and determine how the largest near-term mission benefits can be derived using arcjet propulsion. A reference mission is outlined from this trade-off analysis which is North-South stationkeeping of a 2600 kg-class telecommunications satellite. The major systems issues and factors to be evaluated in subsequent phases of the systems study are discussed.

  14. A fitness trade-off between seasons causes multigenerational cycles in phenotype and population size

    PubMed Central

    Betini, Gustavo S; McAdam, Andrew G; Griswold, Cortland K; Norris, D Ryan

    2017-01-01

    Although seasonality is widespread and can cause fluctuations in the intensity and direction of natural selection, we have little information about the consequences of seasonal fitness trade-offs for population dynamics. Here we exposed populations of Drosophila melanogaster to repeated seasonal changes in resources across 58 generations and used experimental and mathematical approaches to investigate how viability selection on body size in the non-breeding season could affect demography. We show that opposing seasonal episodes of natural selection on body size interacted with both direct and delayed density dependence to cause populations to undergo predictable multigenerational density cycles. Our results provide evidence that seasonality can set the conditions for life-history trade-offs and density dependence, which can, in turn, interact to cause multigenerational population cycles. DOI: http://dx.doi.org/10.7554/eLife.18770.001 PMID:28164780

  15. Trade-offs between robustness and small-world effect in complex networks

    NASA Astrophysics Data System (ADS)

    Peng, Guan-Sheng; Tan, Suo-Yi; Wu, Jun; Holme, Petter

    2016-11-01

    Robustness and small-world effect are two crucial structural features of complex networks and have attracted increasing attention. However, little is known about the relation between them. Here we demonstrate that, there is a conflicting relation between robustness and small-world effect for a given degree sequence. We suggest that the robustness-oriented optimization will weaken the small-world effect and vice versa. Then, we propose a multi-objective trade-off optimization model and develop a heuristic algorithm to obtain the optimal trade-off topology for robustness and small-world effect. We show that the optimal network topology exhibits a pronounced core-periphery structure and investigate the structural properties of the optimized networks in detail.

  16. Trade-off between false positives and false negatives in the linkage analysis of complex traits.

    PubMed

    Todorov, A A; Rao, D C

    1997-01-01

    This study examines the issue of false positives in genomic scans for detecting complex trait loci using subpair linkage methods and investigates the trade-off between the rate of false positives and the rate of false negatives. It highlights the tremendous cost in terms of power brought about by an excessive control of type I error and, at the same time, confirms that a larger number of false positives can occur otherwise in the course of a genomic scan. Finally, it compares the power and rate of false positives obtained in preplanned replicated studies conducted using a liberal significance level to those for single-step studies that use the same total sample size but stricter levels of significance. For the models considered here, replicate studies were found more attractive as long as one is willing to accept a trade-off, exchanging a much lower rate of false negatives for a slight increase in the rate of false positives.

  17. Trade-offs between robustness and small-world effect in complex networks.

    PubMed

    Peng, Guan-Sheng; Tan, Suo-Yi; Wu, Jun; Holme, Petter

    2016-11-17

    Robustness and small-world effect are two crucial structural features of complex networks and have attracted increasing attention. However, little is known about the relation between them. Here we demonstrate that, there is a conflicting relation between robustness and small-world effect for a given degree sequence. We suggest that the robustness-oriented optimization will weaken the small-world effect and vice versa. Then, we propose a multi-objective trade-off optimization model and develop a heuristic algorithm to obtain the optimal trade-off topology for robustness and small-world effect. We show that the optimal network topology exhibits a pronounced core-periphery structure and investigate the structural properties of the optimized networks in detail.

  18. Trade-Off and Synergy among Ecosystem Services in the Guanzhong-Tianshui Economic Region of China.

    PubMed

    Qin, Keyu; Li, Jing; Yang, Xiaonan

    2015-11-03

    Natural ecosystems provide society with important goods and services. With rapidly increasing populations and excessive utilization of natural resources, humans have been enhancing the production of some services at the expense of others. Although the need for certain trade-offs between conservation and development is urgent, having only a small number of efficient methods to assess such trade-offs has impeded progress. This study focuses on the evaluation of ecosystem services under different land use schemes. It reveals the spatial and temporal distributions of and changes in ecosystem services. Based on a correlation rate model and distribution mapping, the trade-offs and synergies of these ecosystem services can be found. Here, we also describe a new simple approach to quantify the relationships of every trade-off and synergy. The results show that all ecosystem services possess trade-offs and synergies in the study area. The trend of improving carbon sequestration and water interception indicate that these key ecosystem services have the strongest synergy. And the decrease in regional agricultural production and other services, except water yield, may be considered as trade-offs. The synergy between water yield and agricultural production was the most significant, while the trade-off between water interception and carbon sequestration was the most apparent, according to our interaction quantification model. The results of this study have implications for planning and monitoring the future management of natural capital and ecosystem services, and can be integrated into land use decision-making.

  19. Trade-offs between reproductive coloration and innate immunity in a natural population of female sagebrush lizards, Sceloporus graciosus

    PubMed Central

    Ruiz, Mayté; Wang, Danfeng; Reinke, Beth A.; Demas, Gregory E.; Martins, Emília P.

    2014-01-01

    Trade-offs between immune function and reproduction are common to many organisms. Nevertheless, high energetic resources may eliminate the need for these trade-offs. In this study, we consider the effects of food availability on these trade-offs in a wild population of female sagebrush lizards (Sceloporus graciosus) during the breeding season. We manipulated food availability by supplementing some lizards but not others. We measured female orange side coloration as an indicator of reproductive state and calculated the bacterial killing capability of collected plasma exposed to Escherichia coli ex vivo as a measure of innate immunity. We found that female lizards show a natural trade-off between reproductive effort and immune function; females under high reproductive investment had lower innate immunity than those at a later reproductive state. We did not detect this trade-off with food supplementation. We show that trade-offs depend on the energetic state of the animal, illustrating that trade-offs between immune function and reproduction can be context-dependent. PMID:25400312

  20. Trade-Off and Synergy among Ecosystem Services in the Guanzhong-Tianshui Economic Region of China

    PubMed Central

    Qin, Keyu; Li, Jing; Yang, Xiaonan

    2015-01-01

    Natural ecosystems provide society with important goods and services. With rapidly increasing populations and excessive utilization of natural resources, humans have been enhancing the production of some services at the expense of others. Although the need for certain trade-offs between conservation and development is urgent, having only a small number of efficient methods to assess such trade-offs has impeded progress. This study focuses on the evaluation of ecosystem services under different land use schemes. It reveals the spatial and temporal distributions of and changes in ecosystem services. Based on a correlation rate model and distribution mapping, the trade-offs and synergies of these ecosystem services can be found. Here, we also describe a new simple approach to quantify the relationships of every trade-off and synergy. The results show that all ecosystem services possess trade-offs and synergies in the study area. The trend of improving carbon sequestration and water interception indicate that these key ecosystem services have the strongest synergy. And the decrease in regional agricultural production and other services, except water yield, may be considered as trade-offs. The synergy between water yield and agricultural production was the most significant, while the trade-off between water interception and carbon sequestration was the most apparent, according to our interaction quantification model. The results of this study have implications for planning and monitoring the future management of natural capital and ecosystem services, and can be integrated into land use decision-making. PMID:26540068

  1. SIVsm Quasispecies Adaptation to a New Simian Host

    PubMed Central

    2005-01-01

    Despite the potential for infectious agents harbored by other species to become emerging human pathogens, little is known about why some agents establish successful cross-species transmission, while others do not. The simian immunodeficiency viruses (SIVs), certain variants of which gave rise to the human HIV-1 and HIV-2 epidemics, have demonstrated tremendous success in infecting new host species, both simian and human. SIVsm from sooty mangabeys appears to have infected humans on several occasions, and was readily transmitted to nonnatural Asian macaque species, providing animal models of AIDS. Here we describe the first in-depth analysis of the tremendous SIVsm quasispecies sequence variation harbored by individual sooty mangabeys, and how this diverse quasispecies adapts to two different host species—new nonnatural rhesus macaque hosts and natural sooty mangabey hosts. Viral adaptation to rhesus macaques was associated with the immediate amplification of a phylogenetically related subset of envelope (env) variants. These variants contained a shorter variable region 1 loop and lacked two specific glycosylation sites, which may be selected for during acute infection. In contrast, transfer of SIVsm to its natural host did not subject the quasispecies to any significant selective pressures or bottleneck. After 100 d postinfection, variants more closely representative of the source inoculum reemerged in the macaques. This study describes an approach for elucidating how pathogens adapt to new host species, and highlights the particular importance of SIVsm env diversity in enabling cross-species transmission. The replicative advantage of a subset of SIVsm variants in macaques may be related to features of target cells or receptors that are specific to the new host environment, and may involve CD4-independent engagement of a viral coreceptor conserved among primates. PMID:16201015

  2. Unconventional Fossil-Based Fuels. Economic and Environmental Trade-Offs

    DTIC Science & Technology

    2008-01-01

    Library of Congress Cataloging-in-Publication Data Unconventional fossil-based fuels : economic and environmental trade-offs / Michael Toman ... [et...247, No. 4945, February 23, 1990, pp. 920–924. Baker, John M., Tyson E. Ochsner, Rodney T. Venterea, and Timothy J. Griffis, “Tillage and Soil...D.C., April 20–21, 2006. Lacombe, Romain H., and John E. Parsons, Technologies, Markets and Challenges for Development of the Canadian Oil Sands

  3. Trade-offs in seedling growth and survival within and across tropical forest microhabitats

    PubMed Central

    Inman-Narahari, Faith; Ostertag, Rebecca; Asner, Gregory P; Cordell, Susan; Hubbell, Stephen P; Sack, Lawren

    2014-01-01

    For niche differences to maintain coexistence of sympatric species, each species must grow and/or survive better than each of the others in at least one set of conditions (i.e., performance trade-offs). However, the extent of niche differentiation in tropical forests remains highly debated. We present the first test of performance trade-offs for wild seedlings in a tropical forest. We measured seedling relative growth rate (RGR) and survival of four common native woody species across 18 light, substrate, and topography microhabitats over 2.5 years within Hawaiian montane wet forest, an ideal location due to its low species diversity and strong species habitat associations. All six species pairs exhibited significant performance trade-offs across microhabitats and for RGR versus survival within microhabitats. We also found some evidence of performance equivalence, with species pairs having similar performance in 26% of comparisons across microhabitats. Across species, survival under low light was generally positively associated with RGR under high light. When averaged over all species, topography (slope, aspect, and elevation) explained most of the variation in RGR attributable to microhabitat variables (51–53%) followed by substrate type (35–37%) and light (11–12%). However, the relative effects of microhabitat differed among species and RGR metric (i.e., RGR for height, biomass, or leaf area). These findings indicate that performance trade-offs among species during regeneration are common in low-diversity tropical forest, although other mechanisms may better explain the coexistence of species with small performance differences. PMID:25614790

  4. Towards an Optimal Noise Versus Resolution Trade-Off in Wind Scatterometry

    NASA Technical Reports Server (NTRS)

    Williams, Brent A.

    2011-01-01

    This paper approaches the noise versus resolution trade-off in wind scatterometry from a field-wise retrieval perspective. Theoretical considerations are discussed and practical implementation using a MAP estimator is applied to the Sea-Winds scatterometer. The approach is compared to conventional approaches as well as numerical weather predictions. The new approach incorporates knowledge of the wind spectrum to reduce the impact of components of the wind signal that are expected to be noisy.

  5. Simbol-X Background Minimization: Mirror Spacecraft Passive Shielding Trade-off Study

    NASA Astrophysics Data System (ADS)

    Fioretti, V.; Malaguti, G.; Bulgarelli, A.; Palumbo, G. G. C.; Ferri, A.; Attinà, P.

    2009-05-01

    The present work shows a quantitative trade-off analysis of the Simbol-X Mirror Spacecraft (MSC) passive shielding, in the phase space of the various parameters: mass budget, dimension, geometry and composition. A simplified physical (and geometrical) model of the sky screen, implemented by means of a GEANT4 simulation, has been developed to perform a performance-driven mass optimization and evaluate the residual background level on Simbol-X focal plane.

  6. Mate choice trade-offs and women's preference for physically attractive men.

    PubMed

    Waynforth, D

    2001-09-01

    Researchers studying human sexuality have repeatedly concluded that men place more emphasis on the physical attractiveness of potential mates than women do, particularly in long-term sexual relationships. Evolutionary theorists have suggested that this is the case because male mate value (the total value of the characteristics that an individual possesses in terms of the potential contribution to his or her mate's reproductive success) is better predicted by social status and economic resources, whereas women's mate value hinges on signals conveyed by their physical appearance. This pattern may imply that women trade off attractiveness for resources in mate choice. Here I test whether a trade-off between resources and attractiveness seems to be occurring in the mate choice decisions of women in the United States. In addition, the possibility that the risk of mate desertion drives women to choose less attractive men as long-term mates is tested. The results were that women rated physically attractive men as more likely to cheat or desert a long-term relationship, whereas men did not consider attractive women to be more likely to cheat. However, women showed no aversion to the idea of forming long-term relationships with attractive men. Evidence for a trade-off between resources and attractiveness was found for women, who traded off attractiveness, but not other traits, for resources. The potential meaning of these findings, as well as how they relate to broader issues in the study of sex differences in the evolution of human mate choice for physical traits, is discussed.

  7. Exploring a water/energy trade-off in regional sourcing of livestock feed crops.

    PubMed

    Heller, Martin C; Keoleian, Gregory A

    2011-12-15

    Feed production constitutes a major portion of the energy and water resource inputs in modern livestock production. Schemes to reduce these inputs may include local sourcing of animal feed. However, in water stressed regions where irrigation of feed crops is necessary, a trade-off between local sourcing (with high water stress) and transport from less water stressed regions can occur. We demonstrate this trade-off in the U.S. by combining state-level irrigation water use and pumping energy demand from USDA surveys with fertilizer and transportation energy demands for producing major feed crops (corn grain, soybean, alfalfa hay, corn silage) in each state and delivering them to two hypothetical dairy farms located in Kersey, CO and Rosendale, WI. A back-up technology approach is employed to express freshwater resource depletion in units of energy, allowing direct comparison with other energy resource demands. Corn grain, soybean, and alfalfa hay delivered to CO demonstrate a clear trade-off between transportation energy (proportional to the distance between CO and the production state) and water stress. On the other hand, transportation burdens dominate for corn silage, making local production most attractive, even in water stressed regions. All crops delivered to WI (a region of low water stress and minimal irrigation) are dominated by transportation burdens, making local production preferable, but this is clearly not a universal principal, as other cases show. This paper quantitatively elucidates the water-energy trade-off in sourcing feed for livestock and the method is expected to be applicable in managing supply chain logistics of other farm commodities.

  8. A trade-off between reproduction and feather growth in the barn swallow (Hirundo rustica).

    PubMed

    Saino, Nicola; Romano, Maria; Rubolini, Diego; Ambrosini, Roberto; Romano, Andrea; Caprioli, Manuela; Costanzo, Alessandra; Bazzi, Gaia

    2014-01-01

    Physiological trade-offs mediated by limiting energy, resources or time constrain the simultaneous expression of major functions and can lead to the evolution of temporal separation between demanding activities. In birds, plumage renewal is a demanding activity, which accomplishes fundamental functions, such as allowing thermal insulation, aerodynamics and socio-sexual signaling. Feather renewal is a very expensive and disabling process, and molt is often partitioned from breeding and migration. However, trade-offs between feather renewal and breeding have been only sparsely studied. In barn swallows (Hirundo rustica) breeding in Italy and undergoing molt during wintering in sub-Saharan Africa, we studied this trade-off by removing a tail feather from a large sample of individuals and analyzing growth bar width, reflecting feather growth rate, and length of the growing replacement feather in relation to the stage in the breeding cycle at removal and clutch size. Growth bar width of females and length of the growing replacement feather of both sexes were smaller when the original feather had been removed after clutch initiation. Importantly, in females both growth bar width and replacement feather length were negatively predicted by clutch size, and more strongly so for large clutches and when feather removal occurred immediately after clutch completion. Hence, we found strong, coherent evidence for a trade-off between reproduction, and laying effort in particular, and the ability to generate new feathers. These results support the hypothesis that the derived condition of molting during wintering in long-distance migrants is maintained by the costs of overlapping breeding and molt.

  9. Design Trade-off Between Performance and Fault-Tolerance of Space Onboard Computers

    NASA Astrophysics Data System (ADS)

    Gorbunov, M. S.; Antonov, A. A.

    2017-01-01

    It is well known that there is a trade-off between performance and power consumption in onboard computers. The fault-tolerance is another important factor affecting performance, chip area and power consumption. Involving special SRAM cells and error-correcting codes is often too expensive with relation to the performance needed. We discuss the possibility of finding the optimal solutions for modern onboard computer for scientific apparatus focusing on multi-level cache memory design.

  10. Does individual quality mask the detection of performance trade-offs? A test using analyses of human physical performance.

    PubMed

    Wilson, Robbie S; Niehaus, Amanda C; David, Gwendolyn; Hunter, Andrew; Smith, Michelle

    2014-02-15

    Why are performance trade-offs so rarely detected in animals when their underlying physiological basis seems so intuitive? One possibility is that individual variation in health, fitness, nutrition, development or genetics, or 'individual quality', makes some individuals better or worse performers across all motor tasks. If this is the case, then correcting for individual quality should reveal functional trade-offs that might otherwise be overlooked. We tested this idea by exploring trade-offs in maximum physical performance and motor skill function in semi-professional soccer players. We assessed individual performance across five maximum 'athletic' tasks providing independent measures of power, stamina and speed, as well as five soccer-specific 'motor skill' tasks providing independent measures of foot control. We expected to find functional trade-offs between pairs of traits (e.g. endurance versus power/speed tasks or specialist-generalist performance) - but only after correcting for individual quality. Analyses of standardised raw data found positive associations among several pairs of traits, but no evidence of performance trade-offs. Indeed, peak performance across a single athletic task (degree of specialisation) was positively associated with performance averaged across all other athletic tasks (generalist). However, after accounting for an individual's overall quality, several functional trade-offs became evident. Within our quality-corrected data, 1500 m-speed (endurance) was negatively associated with squat time (power), jump distance (power) and agility speed - reflecting the expected speed-endurance trade-off; and degree of specialisation was negatively associated with average performance across tasks. Taken together, our data support the idea that individual variation in general quality can mask the detection of performance trade-offs at the whole-animal level. These results highlight the possibility that studies may spuriously conclude certain

  11. Assessing trade-offs to inform ecosystem-based fisheries management of forage fish

    PubMed Central

    Shelton, Andrew Olaf; Samhouri, Jameal F.; Stier, Adrian C.; Levin, Philip S.

    2014-01-01

    Twenty-first century conservation is centered on negotiating trade-offs between the diverse needs of people and the needs of the other species constituting coupled human-natural ecosystems. Marine forage fishes, such as sardines, anchovies, and herring, are a nexus for such trade-offs because they are both central nodes in marine food webs and targeted by fisheries. An important example is Pacific herring, Clupea pallisii in the Northeast Pacific. Herring populations are subject to two distinct fisheries: one that harvests adults and one that harvests spawned eggs. We develop stochastic, age-structured models to assess the interaction between fisheries, herring populations, and the persistence of predators reliant on herring populations. We show that egg- and adult-fishing have asymmetric effects on herring population dynamics - herring stocks can withstand higher levels of egg harvest before becoming depleted. Second, ecosystem thresholds proposed to ensure the persistence of herring predators do not necessarily pose more stringent constraints on fisheries than conventional, fishery driven harvest guidelines. Our approach provides a general template to evaluate ecosystem trade-offs between stage-specific harvest practices in relation to environmental variability, the risk of fishery closures, and the risk of exceeding ecosystem thresholds intended to ensure conservation goals are met. PMID:25407879

  12. Genetic basis of the trade-off between offspring number and quality in the bank vole.

    PubMed

    Mappes, Tapio; Koskela, Esa

    2004-03-01

    One of the main tenets of modern life-history theory is the negative relationship (trade-off) between the number and quality of offspring produced. Theory predicts a negative genetic correlation between these traits since both are closely related to fitness of individuals. However, the genetic basis of the trade-off has only been tested to a limited extent in natural populations. We examined whether size and quality of offspring are negatively related to litter size in the bank vole Clethrionomys glareolus. First, we found a significant negative phenotypic correlation between the number and size of offspring at birth in both laboratory and field populations of the bank vole. Second, a larger size at birth decreased the maturation age of female offspring in the laboratory, and increased the probability of breeding and the size of the first litter in the field. Furthermore, manipulation of offspring size at weaning indicated that structural effects of birth size in mammals have a more profound effect on the expression of life-history traits than weaning size. Finally, in addition to the phenotypic negative correlation between the number and size of offspring, we found evidence for a negative genetic correlation between these two traits, which confirms the genetic basis of the trade-off. This negative genetic covariation may have considerable effects on the rate and direction of evolution of the two related life-historical traits.

  13. Trade-offs between force and fit: extreme morphologies associated with feeding behavior in carabid beetles.

    PubMed

    Konuma, Junji; Chiba, Satoshi

    2007-07-01

    We explored how functional trade-offs in resource handling strategies are associated with the divergent morphology of predators. The malacophagous carabid Damaster blaptoides shows two extreme morphologies in the forebody; there is an elongate small-headed type and a stout large-headed type. A feeding experiment showed that the small-headed type obtained a high feeding performance on snails with a thick shell and a large aperture by penetrating the shell with its head. In contrast, the large-headed type showed a high feeding performance on snails that had a thin shell and a small aperture, and they ate these prey by crushing the shell. The large-headed, strong-jawed beetles are efficient at shell crushing but are ineffective at shell entry; the large mandibles and musculature that allow for shell crushing make the beetle's head too wide to penetrate shell apertures. On the other hand, small-headed, weak-jawed beetles crush poorly but can reach into shells for direct predation on snail bodies. These findings are hypothesized to be functional trade-offs between force and fit due to morphological constraints. This trade-off would be a primary mechanism affecting both resource handling ability in animals and phenotypic diversity in predators and prey.

  14. Soil management shapes ecosystem service provision and trade-offs in agricultural landscapes.

    PubMed

    Tamburini, Giovanni; De Simone, Serena; Sigura, Maurizia; Boscutti, Francesco; Marini, Lorenzo

    2016-08-31

    Agroecosystems are principally managed to maximize food provisioning even if they receive a large array of supporting and regulating ecosystem services (ESs). Hence, comprehensive studies investigating the effects of local management and landscape composition on the provision of and trade-offs between multiple ESs are urgently needed. We explored the effects of conservation tillage, nitrogen fertilization and landscape composition on six ESs (crop production, disease control, soil fertility, water quality regulation, weed and pest control) in winter cereals. Conservation tillage enhanced soil fertility and pest control, decreased water quality regulation and weed control, without affecting crop production and disease control. Fertilization only influenced crop production by increasing grain yield. Landscape intensification reduced the provision of disease and pest control. We also found tillage and landscape composition to interactively affect water quality regulation and weed control. Under N fertilization, conventional tillage resulted in more trade-offs between ESs than conservation tillage. Our results demonstrate that soil management and landscape composition affect the provision of several ESs and that soil management potentially shapes the trade-offs between them.

  15. Having it all: historical energy intakes do not generate the anticipated trade-offs in fecundity

    PubMed Central

    Johnston, S.L; Grune, T; Bell, L.M; Murray, S.J; Souter, D.M; Erwin, S.S; Yearsley, J.M; Gordon, I.J; Illius, A.W; Kyriazakis, I; Speakman, J.R

    2006-01-01

    An axiom of life-history theory, and fundamental to our understanding of ageing, is that animals must trade-off their allocation of resources since energy and nutrients are limited. Therefore, animals cannot ‘have it all’—combine high rates of fecundity with extended lifespans. The idea of life-history trade-offs was recently challenged by the discovery that ageing may be governed by a small subset of molecular processes independent of fitness. We tested the ‘trade-off’ and ‘having it all’ theories by examining the fecundities of C57BL/6J mice placed onto four different dietary treatments that generated caloric intakes from −21 to +8.6% of controls. We predicted body fat would be deposited in relation to caloric intake. Excessive body fat is known to cause co-morbidities that shorten lifespan, while caloric restriction enhances somatic protection and increases longevity. The trade-off model predicts that increased fat would be tolerated because reproductive gain offsets shortened longevity, while animals on a restricted intake would sacrifice reproduction for lifespan extension. The responses of body fat to treatments followed our expectations, however, there was a negative relationship between reproductive performance (fecundity, litter mass) and historical intake/body fat. Our dietary restricted animals had lower protein oxidative damage and appeared able to combine life-history traits in a manner contrary to traditional expectations by having increased fecundity with the potential to have extended lifespans. PMID:16777725

  16. Dopaminergic modulation of the trade-off between probability and time in economic decision-making.

    PubMed

    Arrondo, Gonzalo; Aznárez-Sanado, Maite; Fernández-Seara, Maria A; Goñi, Joaquín; Loayza, Francis R; Salamon-Klobut, Ewa; Heukamp, Franz H; Pastor, Maria A

    2015-06-01

    Studies on animals and humans have demonstrated the importance of dopamine in modulating decision-making processes. In this work, we have tested dopaminergic modulation of economic decision-making and its neural correlates by administering either placebo or metoclopramide, a dopamine D2-receptor antagonist, to healthy subjects, during a functional MRI study. The decision-making task combined probability and time delay with a fixed monetary reward. For individual behavioral characterization, we used the Probability Time Trade-off (PTT) economic model, which integrates the traditional trade-offs of reward magnitude-time and reward magnitude-probability into a single measurement, thereby quantifying the subjective value of a delayed and probabilistic outcome. A regression analysis between BOLD signal and the PTT model index permitted to identify the neural substrate encoding the subjective reward-value. Behaviorally, medication reduced the rate of temporal discounting over probability, reflected in medicated subjects being more prone to postpone the reward in order to increase the outcome probability. In addition, medicated subjects showed less activity during the task in the postcentral gyrus as well as frontomedian areas, whereas there were no differences in the ventromedial orbitofrontal cortex (VMOFC) between groups when coding the subjective value. The present study demonstrates by means of behavior and imaging that dopamine modulation alters the probability-time trade-off in human economic decision-making.

  17. Assessing trade-offs to inform ecosystem-based fisheries management of forage fish.

    PubMed

    Shelton, Andrew Olaf; Samhouri, Jameal F; Stier, Adrian C; Levin, Philip S

    2014-11-19

    Twenty-first century conservation is centered on negotiating trade-offs between the diverse needs of people and the needs of the other species constituting coupled human-natural ecosystems. Marine forage fishes, such as sardines, anchovies, and herring, are a nexus for such trade-offs because they are both central nodes in marine food webs and targeted by fisheries. An important example is Pacific herring, Clupea pallisii in the Northeast Pacific. Herring populations are subject to two distinct fisheries: one that harvests adults and one that harvests spawned eggs. We develop stochastic, age-structured models to assess the interaction between fisheries, herring populations, and the persistence of predators reliant on herring populations. We show that egg- and adult-fishing have asymmetric effects on herring population dynamics--herring stocks can withstand higher levels of egg harvest before becoming depleted. Second, ecosystem thresholds proposed to ensure the persistence of herring predators do not necessarily pose more stringent constraints on fisheries than conventional, fishery driven harvest guidelines. Our approach provides a general template to evaluate ecosystem trade-offs between stage-specific harvest practices in relation to environmental variability, the risk of fishery closures, and the risk of exceeding ecosystem thresholds intended to ensure conservation goals are met.

  18. Evading the strength–ductility trade-off dilemma in steel through gradient hierarchical nanotwins

    PubMed Central

    Wei, Yujie; Li, Yongqiang; Zhu, Lianchun; Liu, Yao; Lei, Xianqi; Wang, Gang; Wu, Yanxin; Mi, Zhenli; Liu, Jiabin; Wang, Hongtao; Gao, Huajian

    2014-01-01

    The strength–ductility trade-off has been a long-standing dilemma in materials science. This has limited the potential of many structural materials, steels in particular. Here we report a way of enhancing the strength of twinning-induced plasticity steel at no ductility trade-off. After applying torsion to cylindrical twinning-induced plasticity steel samples to generate a gradient nanotwinned structure along the radial direction, we find that the yielding strength of the material can be doubled at no reduction in ductility. It is shown that this evasion of strength–ductility trade-off is due to the formation of a gradient hierarchical nanotwinned structure during pre-torsion and subsequent tensile deformation. A series of finite element simulations based on crystal plasticity are performed to understand why the gradient twin structure can cause strengthening and ductility retention, and how sequential torsion and tension lead to the observed hierarchical nanotwinned structure through activation of different twinning systems. PMID:24686581

  19. No allocation trade-offs between flowering and sproutingin the lignotuberous, Mediterranean shrub Erica australis

    NASA Astrophysics Data System (ADS)

    Cruz, Alberto; Moreno, José M.

    2001-04-01

    Trade-offs between allocation to sexual or vegetative regeneration capacity are well established as a driving force in the life history patterns of plants in fire-prone environments. However, it is not known whether such trade-offs exist in plants which after aboveground removing disturbances, such as fire, may regenerate by sexual (seeding) or asexual (sprouting) mechanisms. We evaluated whether in the fire-recruiting resprouter Erica australis, which after fire can regenerate by seedling establishment or resprouting, a larger investment in flowers and seeds prior to being disturbed by clipping its aboveground parts would decrease subsequent sprouting, that is, its vegetative regeneration capacity. We analysed the relationships between flower and seed production and the ensuing production and growth of sprouts of six plants from thirteen different sites in central-western Spain. We found no significant relationships between measures of sexual reproductive effort and resprout production and growth 6 months after clipping the aboveground parts of the plants. No evidence of trade-offs between sexual and asexual efforts was found. Furthermore, no significant relationship was found between lignotuber total non-structural carbohydrates and sexual reproductive effort. In addition, 2 years after the disturbance, resprout biomass was positively and significantly correlated with sexual reproductive effort prior to the disturbance. This indicates that growth of resprouts was higher at the sites where plants made a greater reproductive effort. The sites that were more favourable to producing flowers and seeds could also be more favourable to resprouting.

  20. Many-objective optimization and visual analytics reveal key trade-offs for London's water supply

    NASA Astrophysics Data System (ADS)

    Matrosov, Evgenii S.; Huskova, Ivana; Kasprzyk, Joseph R.; Harou, Julien J.; Lambert, Chris; Reed, Patrick M.

    2015-12-01

    In this study, we link a water resource management simulator to multi-objective search to reveal the key trade-offs inherent in planning a real-world water resource system. We consider new supplies and demand management (conservation) options while seeking to elucidate the trade-offs between the best portfolios of schemes to satisfy projected water demands. Alternative system designs are evaluated using performance measures that minimize capital and operating costs and energy use while maximizing resilience, engineering and environmental metrics, subject to supply reliability constraints. Our analysis shows many-objective evolutionary optimization coupled with state-of-the art visual analytics can help planners discover more diverse water supply system designs and better understand their inherent trade-offs. The approach is used to explore future water supply options for the Thames water resource system (including London's water supply). New supply options include a new reservoir, water transfers, artificial recharge, wastewater reuse and brackish groundwater desalination. Demand management options include leakage reduction, compulsory metering and seasonal tariffs. The Thames system's Pareto approximate portfolios cluster into distinct groups of water supply options; for example implementing a pipe refurbishment program leads to higher capital costs but greater reliability. This study highlights that traditional least-cost reliability constrained design of water supply systems masks asset combinations whose benefits only become apparent when more planning objectives are considered.

  1. Early-late life trade-offs and the evolution of ageing in the wild.

    PubMed

    Lemaître, Jean-François; Berger, Vérane; Bonenfant, Christophe; Douhard, Mathieu; Gamelon, Marlène; Plard, Floriane; Gaillard, Jean-Michel

    2015-05-07

    Empirical evidence for declines in fitness components (survival and reproductive performance) with age has recently accumulated in wild populations, highlighting that the process of senescence is nearly ubiquitous in the living world. Senescence patterns are highly variable among species and current evolutionary theories of ageing propose that such variation can be accounted for by differences in allocation to growth and reproduction during early life. Here, we compiled 26 studies of free-ranging vertebrate populations that explicitly tested for a trade-off between performance in early and late life. Our review brings overall support for the presence of early-late life trade-offs, suggesting that the limitation of available resources leads individuals to trade somatic maintenance later in life for high allocation to reproduction early in life. We discuss our results in the light of two closely related theories of ageing-the disposable soma and the antagonistic pleiotropy theories-and propose that the principle of energy allocation roots the ageing process in the evolution of life-history strategies. Finally, we outline research topics that should be investigated in future studies, including the importance of natal environmental conditions in the study of trade-offs between early- and late-life performance and the evolution of sex-differences in ageing patterns.

  2. Trade-off between carotenoid-based sexual ornamentation and sperm resistance to oxidative challenge.

    PubMed

    Tomášek, Oldřich; Albrechtová, Jana; Němcová, Martina; Opatová, Pavlína; Albrecht, Tomáš

    2017-01-25

    It has been hypothesized that carotenoid-based sexual ornamentation signals male fertility and sperm competitive ability as both ornamentation and sperm traits may be co-affected by oxidative stress, resulting in positive covariation (the 'redox-based phenotype-linked fertility hypothesis'; redox-based PLFH). On the other hand, the 'sperm competition theory' (SCT) predicts a trade-off between precopulatory and postcopulatory traits. Here, we manipulate oxidative status (using diquat dibromide) and carotenoid availability in adult zebra finch (Taeniopygia guttata) males in order to test whether carotenoid-based beak ornamentation signals, or is traded off against, sperm resistance to oxidative challenge. Initial beak colouration, but not its change during the experiment, was associated with effect of oxidative challenge on sperm velocity, such that more intense colouration predicted an increase in sperm velocity under control conditions but a decline under oxidative challenge. This suggests a long-term trade-off between ornament expression and sperm resistance to oxidative challenge. Shortening of the sperm midpiece following oxidative challenge further suggests that redox homeostasis may constrain sperm morphometry. Carotenoid supplementation resulted in fewer sperm abnormalities but had no effect on other sperm traits. Overall, our data challenge the redox-based PLFH, partially support the SCT and highlight the importance of carotenoids for normal sperm morphology.

  3. Potential Trade-Offs in Treatment of Pre-Manifest Huntington Disease

    PubMed Central

    Albin, Roger L.; Burke, James F

    2016-01-01

    The potential long-term consequences of treatments delaying manifestations of neurodegenerative diseases have not been explored. Using Huntington disease (HD) data and Markov Chain Monte Carlo methods, we simulated the effects of therapies with equivalent effects on time to onset of HD and survival with HD. Our results suggest substantial potential trade-offs in effects of these therapies; significant delays in time to onset of HD were accompanied by significant prolongations of survival after onset of HD. Under a variety of assumptions, treatments delaying onset of HD result in some patients likely to have a greater increase in survival with manifest HD compared to delays in time to onset of HD. Our results suggest that future work in HD should be sensitive to the potential existence of such trade offs and that understanding the preferences of HD patients and the broader HD community will be increasingly important. Future research, trial design, and treatment strategies in HD and other mid-life onset neurodegenerative disorders should consider the possibility of trade-offs in long-term consequences of disease-modifying treatments. PMID:26173644

  4. Faster reproductive rates trade off against offspring growth in wild chimpanzees

    PubMed Central

    Emery Thompson, Melissa; Muller, Martin N.; Sabbi, Kris; Machanda, Zarin P.; Otali, Emily; Wrangham, Richard W.

    2016-01-01

    Life history theory predicts a trade-off between offspring quality and quantity. Among large-bodied mammals, prolonged lactation and infant dependence suggest particularly strong potential for a quality–quantity trade-off to exist. Humans are one of the only such species to have been examined, providing mixed evidence under a peculiar set of circumstances, including extensive nutritional provisioning by nonmothers and extrasomatic wealth transmission. Here, we examine trade-offs between reproductive rate and one aspect of offspring quality (body size) in wild chimpanzees (Pan troglodytes schweinfurthii), a species with long periods of infant dependence and little direct provisioning. Juvenile lean body mass, estimated using urinary creatinine excretion, was positively associated with the interval to the next sibling’s birth. These effects persisted into adolescence and were not moderated by maternal identity. Maternal depletion could not explain poor offspring growth, as older mothers had larger offspring, and low maternal energy balance during lactation predicted larger, not smaller, juvenile size. Instead, our data suggest that offspring growth suffers when mothers wean early to invest in new reproductive efforts. These findings indicate that chimpanzee mothers with the resources to do so prioritize production of new offspring over prolonged investment in current offspring. PMID:27354523

  5. Early-late life trade-offs and the evolution of ageing in the wild

    PubMed Central

    Lemaître, Jean-François; Berger, Vérane; Bonenfant, Christophe; Douhard, Mathieu; Gamelon, Marlène; Plard, Floriane; Gaillard, Jean-Michel

    2015-01-01

    Empirical evidence for declines in fitness components (survival and reproductive performance) with age has recently accumulated in wild populations, highlighting that the process of senescence is nearly ubiquitous in the living world. Senescence patterns are highly variable among species and current evolutionary theories of ageing propose that such variation can be accounted for by differences in allocation to growth and reproduction during early life. Here, we compiled 26 studies of free-ranging vertebrate populations that explicitly tested for a trade-off between performance in early and late life. Our review brings overall support for the presence of early-late life trade-offs, suggesting that the limitation of available resources leads individuals to trade somatic maintenance later in life for high allocation to reproduction early in life. We discuss our results in the light of two closely related theories of ageing—the disposable soma and the antagonistic pleiotropy theories—and propose that the principle of energy allocation roots the ageing process in the evolution of life-history strategies. Finally, we outline research topics that should be investigated in future studies, including the importance of natal environmental conditions in the study of trade-offs between early- and late-life performance and the evolution of sex-differences in ageing patterns. PMID:25833848

  6. Metabolic Trade-offs in Yeast are Caused by F1F0-ATP synthase

    PubMed Central

    Nilsson, Avlant; Nielsen, Jens

    2016-01-01

    Intermediary metabolism provides living cells with free energy and precursor metabolites required for synthesizing proteins, lipids, RNA and other cellular constituents, and it is highly conserved among living species. Only a fraction of cellular protein can, however, be allocated to enzymes of intermediary metabolism and consequently metabolic trade-offs may take place. One such trade-off, aerobic fermentation, occurs in both yeast (the Crabtree effect) and cancer cells (the Warburg effect) and has been a scientific challenge for decades. Here we show, using flux balance analysis combined with in vitro measured enzyme specific activities, that fermentation is more catalytically efficient than respiration, i.e. it produces more ATP per protein mass. And that the switch to fermentation at high growth rates therefore is a consequence of a high ATP production rate, provided by a limited pool of enzymes. The catalytic efficiency is also higher for cells grown on glucose compared to galactose and ethanol, which may explain the observed differences in their growth rates. The enzyme F1F0-ATP synthase (Complex V) was found to have flux control over respiration in the model, and since it is evolutionary conserved, we expect the trade-off to occur in organisms from all kingdoms of life. PMID:26928598

  7. Information content of SNR/resolution trade-offs in three-dimensional magnetic resonance imaging.

    PubMed

    Portnoy, S; Kale, S C; Feintuch, A; Tardif, C; Pike, G B; Henkelman, R M

    2009-04-01

    In MRI, a trade-off exists between resolution and signal-to-noise ratio, since different fractions of the available scan time can be used to acquire data at higher spatial frequencies and to perform signal averaging. By comparing a wide variety of 3D isotropic MR scans with different combinations of SNR, resolution, and scan duration, the impact of this trade-off on the image information content was assessed. The information content of mouse brain, mouse whole-body, and human brain images was evaluated using a simple numerical approach, which sums the information contribution of each individual k-space data point. Results show that, with a fixed receiver bandwidth and field of view, the information content of trade-off images is always maximized when the SNR is equal to about 16. The optimal imaging resolution is dependent on the scan duration, as well as certain MR system properties, such as field strength and coil sensitivity. These properties are, however, easily accounted for with the acquisition of a single scout MR image, and the optimal imaging resolution can then be calculated using a simple mathematical relationship. If the imaging task is approached with a predetermined resolution requirement, the same scout scan can be used to calculate the scan duration that will provide the maximum possible information. Using these relationships to maximize the image information content is an excellent technique for guiding the initial selection of imaging parameters.

  8. Virus adaptation by manipulation of host's gene expression.

    PubMed

    Agudelo-Romero, Patricia; Carbonell, Pablo; Perez-Amador, Miguel A; Elena, Santiago F

    2008-06-11

    Viruses adapt to their hosts by evading defense mechanisms and taking over cellular metabolism for their own benefit. Alterations in cell metabolism as well as side-effects of antiviral responses contribute to symptoms development and virulence. Sometimes, a virus may spill over from its usual host species into a novel one, where usually will fail to successfully infect and further transmit to new host. However, in some cases, the virus transmits and persists after fixing beneficial mutations that allow for a better exploitation of the new host. This situation would represent a case for a new emerging virus. Here we report results from an evolution experiment in which a plant virus was allowed to infect and evolve on a naïve host. After 17 serial passages, the viral genome has accumulated only five changes, three of which were non-synonymous. An amino acid substitution in the viral VPg protein was responsible for the appearance of symptoms, whereas one substitution in the viral P3 protein the epistatically contributed to exacerbate severity. DNA microarray analyses show that the evolved and ancestral viruses affect the global patterns of host gene expression in radically different ways. A major difference is that genes involved in stress and pathogen response are not activated upon infection with the evolved virus, suggesting that selection has favored viral strategies to escape from host defenses.

  9. Testing for local host-parasite adaptation: an experiment with Gyrodactylus ectoparasites and guppy hosts.

    PubMed

    Pérez-Jvostov, Felipe; Hendry, Andrew P; Fussmann, Gregor F; Scott, Marilyn E

    2015-05-01

    Hosts and parasites are in a perpetual co-evolutionary "arms race". Due to their short generation time and large reproductive output, parasites are commonly believed to be ahead in this race, although increasing evidence exists that parasites are not always ahead in the arms race - in part owing to evolutionary lineage and recent ecological history. We assess local adaptation of hosts and parasites, and determine whether adaptation was influenced by ecological or evolutionary history, using full reciprocal cross-infections of four Gyrodactylus ectoparasite populations and their four guppy (Poecilia reticulata) host populations in Trinidad. To consider effects of evolutionary lineage and recent ecology, these four populations were collected from two different river drainages (Marianne and Aripo) and two different predation environments (high and low). The highest infection levels were obtained when parasites from the Aripo lineage infected guppies from the Marianne lineage, indicating a higher infectivity, virulence and/or reproductive success of the Aripo parasites. Aripo lineage guppies were also better able to limit Gyrodactylus population growth than guppies from the Marianne River, indicating their strong "resistance" to Gyrodactylus regardless of the source of the parasite. Predation environment had no detectable influence on host-parasite population dynamics of sympatric or allopatric combinations. The much stronger effect of evolutionary lineage (i.e., river) than recent ecological history (i.e., predation) emphasises its importance in driving co-evolutionary dynamics, and should be explored further in future studies on local host-parasite adaptation.

  10. Host coevolution alters the adaptive landscape of a virus

    PubMed Central

    2016-01-01

    The origin of new and complex structures and functions is fundamental for shaping the diversity of life. Such key innovations are rare because they require multiple interacting changes. We sought to understand how the adaptive landscape led to an innovation whereby bacteriophage λ evolved the new ability to exploit a receptor, OmpF, on Escherichia coli cells. Previous work showed that this ability evolved repeatedly, despite requiring four mutations in one virus gene. Here, we examine how this innovation evolved by studying six intermediate genotypes of λ isolated during independent transitions to exploit OmpF and comparing them to their ancestor. All six intermediates showed large increases in their adsorption rates on the ancestral host. Improvements in adsorption were offset, in large part, by the evolution of host resistance, which occurred by reduced expression of LamB, the usual receptor for λ. As a consequence of host coevolution, the adaptive landscape of the virus changed such that selection favouring four of the six virus intermediates became stronger after the host evolved resistance, thereby accelerating virus populations along the path to using the new OmpF receptor. This dependency of viral fitness on host genotype thus shows an important role for coevolution in the origin of the new viral function. PMID:27683370

  11. Evolutionary implications of the adaptation to different immune systems in a parasite with a complex life cycle

    PubMed Central

    Hammerschmidt, Katrin; Kurtz, Joachim

    2005-01-01

    Many diseases are caused by parasites with complex life cycles that involve several hosts. If parasites cope better with only one of the different types of immune systems of their host species, we might expect a trade-off in parasite performance in the different hosts, that likely influences the evolution of virulence. We tested this hypothesis in a naturally co-evolving host–parasite system consisting of the tapeworm Schistocephalus solidus and its intermediate hosts, a copepod, Macrocyclops albidus, and the three-spined stickleback Gasterosteus aculeatus. We did not find a trade-off between infection success in the two hosts. Rather, tapeworms seem to trade-off adaptation towards different parts of their hosts' immune systems. Worm sibships that performed better in the invertebrate host also seem to be able to evade detection by the fish innate defence systems, i.e. induce lower levels of activation of innate immune components. These worm variants were less harmful for the fish host likely due to reduced costs of an activated innate immune system. These findings substantiate the impact of both hosts' immune systems on parasite performance and virulence. PMID:16271977

  12. Evolution of aging: individual life history trade-offs and population heterogeneity account for mortality patterns across species.

    PubMed

    Le Cunff, Y; Baudisch, A; Pakdaman, K

    2014-08-01

    A broad range of mortality patterns has been documented across species, some even including decreasing mortality over age. Whether there exist a common denominator to explain both similarities and differences in these mortality patterns remains an open question. The disposable soma theory, an evolutionary theory of aging, proposes that universal intracellular trade-offs between maintenance/lifespan and reproduction would drive aging across species. The disposable soma theory has provided numerous insights concerning aging processes in single individuals. Yet, which specific population mortality patterns it can lead to is still largely unexplored. In this article, we propose a model exploring the mortality patterns which emerge from an evolutionary process including only the disposable soma theory core principles. We adapt a well-known model of genomic evolution to show that mortality curves producing a kink or mid-life plateaus derive from a common minimal evolutionary framework. These mortality shapes qualitatively correspond to those of Drosophila melanogaster, Caenorhabditis elegans, medflies, yeasts and humans. Species evolved in silico especially differ in their population diversity of maintenance strategies, which itself emerges as an adaptation to the environment over generations. Based on this integrative framework, we also derive predictions and interpretations concerning the effects of diet changes and heat-shock treatments on mortality patterns.

  13. Nest Construction by a Ground-nesting Bird Represents a Potential Trade-off Between Egg Crypticity and Thermoregulation

    EPA Science Inventory

    Predation selects against conspicuous colors in bird eggs and nests, while thermoregulatory constraints select for nest building behavior that regulates incubation temperatures. We present results that reveal a trade-off between nest crypticity and thermoregulation of eggs base...

  14. A trade-off between embryonic development rate and immune function of avian offspring is concealed by embryonic temperature

    USGS Publications Warehouse

    Martin, Thomas E.; Arriero, Elena; Majewska, Ania

    2011-01-01

    Long embryonic periods are assumed to reflect slower intrinsic development that are thought to trade off to allow enhanced physiological systems, such as immune function. Yet, the relatively rare studies of this trade-off in avian offspring have not found the expected trade-off. Theory and tests have not taken into account the strong extrinsic effects of temperature on embryonic periods of birds. Here, we show that length of the embryonic period did not explain variation in two measures of immune function when temperature was ignored, based on studies of 34 Passerine species in tropical Venezuela (23 species) and north temperate Arizona (11 species). Variation in immune function was explained when embryonic periods were corrected for average embryonic temperature, in order to better estimate intrinsic rates of development. Immune function of offspring trades off with intrinsic rates of embryonic development once the extrinsic effects of embryonic temperatures are taken into account.

  15. How do illusions constrain goal-directed movement: perceptual and visuomotor influences on speed/accuracy trade-off.

    PubMed

    Skewes, Joshua C; Roepstorff, Andreas; Frith, Christopher D

    2011-03-01

    Recent research shows that visual processing influences the speed/accuracy trade-off people use when performing goal-directed movement. This raises the question of how this influence is produced in visual cognition. Visual influences on speed/accuracy trade-off could be produced in conscious visual perception, in non-conscious visuomotor transformation, or by some interaction of conscious perceptual and non-conscious visuomotor processes. There is independent evidence showing that both perceptual and visuomotor processes are involved in trading off speed and accuracy; however, the interaction between these processes has yet to be investigated. We present an experiment in which we show that a change in visual consciousness induced by a perceptual illusion affects the speed and accuracy of goal-directed movements, suggesting that perceptual and visuomotor processes do interact in speed/accuracy trade-off. We discuss the consequences of these results for theories of visual function more generally.

  16. Are trade-offs among species' ecological interactions scale dependent? A test using pitcher-plant inquiline species.

    PubMed

    Kneitel, Jamie M

    2012-01-01

    Trade-offs among species' ecological interactions is a pervasive explanation for species coexistence. The traits associated with trade-offs are typically measured to mechanistically explain species coexistence at a single spatial scale. However, species potentially interact at multiple scales and this may be reflected in the traits among coexisting species. I quantified species' ecological traits associated with the trade-offs expected at both local (competitive ability and predator tolerance) and regional (competitive ability and colonization rate) community scales. The most common species (four protozoa and a rotifer) from the middle trophic level of a pitcher plant (Sarracenia purpurea) inquiline community were used to link species traits to previously observed patterns of species diversity and abundance. Traits associated with trade-offs (competitive ability, predator tolerance, and colonization rate) and other ecological traits (size, growth rate, and carrying capacity) were measured for each of the focal species. Traits were correlated with one another with a negative relationship indicative of a trade-off. Protozoan and rotifer species exhibited a negative relationship between competitive ability and predator tolerance, indicative of coexistence at the local community scale. There was no relationship between competitive ability and colonization rate. Size, growth rate, and carrying capacity were correlated with each other and the trade-off traits: Size was related to both competitive ability and predator tolerance, but growth rate and carrying capacity were correlated with predator tolerance. When partial correlations were conducted controlling for size, growth rate and carrying capacity, the trade-offs largely disappeared. These results imply that body size is the trait that provides the basis for ecological interactions and trade-offs. Altogether, this study showed that the examination of species' traits in the context of coexistence at different scales

  17. Grayscale/resolution trade-off for text: Model predictions and psychophysical results for letter confusion and letter discrimination

    NASA Technical Reports Server (NTRS)

    Gille, Jennifer; Martin, Russel; Lubin, Jeffrey; Larimer, James

    1995-01-01

    In a series of papers presented in 1994, we examined the grayscale/resolution trade-off for natural images displayed on devices with discrete pixellation, such as AMLCD's. In the present paper we extend this study by examining the grayscale/resolution trade-off for text images on discrete-pixel displays. Halftoning in printing is an example of the grayscale/resolution trade-off. In printing, spatial resolution is sacrificed to produce grayscale. Another example of this trade-off is the inherent low-pass spatial filter of a CRT, caused by the point-spread function of the electron beam in the phosphor layer. On a CRT, sharp image edges are blurred by this inherent low-pass filtering, and the block noise created by spatial quantization is greatly reduced. A third example of this trade-off is text anti-aliasing, where grayscale is used to improve letter shape, size and location when rendered at a low spatial resolution. There are additional implications for display system design from the grayscale/resolution trade-off. For example, reduced grayscale can reduce system costs by requiring less complexity in the framestore, allowing the use of lower cost drivers, potentially increasing data transfer rates in the image subsystem, and simplifying the manufacturing processes that are used to construct the active matrix for AMLCD (active-matrix liquid-crystal display) or AMTFEL (active-matrix thin-film electroluminescent) devices. Therefore, the study of these trade-offs is important for display designers and manufacturing and systems engineers who wish to create the highest performance, lowest cost device possible. Our strategy for investigating this trade-off is to generate a set of simple test images, manipulate grayscale and resolution, predict discrimination performance using the ViDEOS(Sarnoff) Human Vision Model, conduct an empirical study of discrimination using psychophysical procedures, and verify the computational results using the psychophysical results.

  18. Genomics of adaptation to host-plants in herbivorous insects.

    PubMed

    Simon, Jean-Christophe; d'Alençon, Emmanuelle; Guy, Endrick; Jacquin-Joly, Emmanuelle; Jaquiéry, Julie; Nouhaud, Pierre; Peccoud, Jean; Sugio, Akiko; Streiff, Réjane

    2015-11-01

    Herbivorous insects represent the most species-rich lineages of metazoans. The high rate of diversification in herbivorous insects is thought to result from their specialization to distinct host-plants, which creates conditions favorable for the build-up of reproductive isolation and speciation. These conditions rely on constraints against the optimal use of a wide range of plant species, as each must constitute a viable food resource, oviposition site and mating site for an insect. Utilization of plants involves many essential traits of herbivorous insects, as they locate and select their hosts, overcome their defenses and acquire nutrients while avoiding intoxication. Although advances in understanding insect-plant molecular interactions have been limited by the complexity of insect traits involved in host use and the lack of genomic resources and functional tools, recent studies at the molecular level, combined with large-scale genomics studies at population and species levels, are revealing the genetic underpinning of plant specialization and adaptive divergence in non-model insect herbivores. Here, we review the recent advances in the genomics of plant adaptation in hemipterans and lepidopterans, two major insect orders, each of which includes a large number of crop pests. We focus on how genomics and post-genomics have improved our understanding of the mechanisms involved in insect-plant interactions by reviewing recent molecular discoveries in sensing, feeding, digesting and detoxifying strategies. We also present the outcomes of large-scale genomics approaches aimed at identifying loci potentially involved in plant adaptation in these insects.

  19. Dopamine drives Drosophila sechellia adaptation to its toxic host

    PubMed Central

    Lavista-Llanos, Sofía; Svatoš, Aleš; Kai, Marco; Riemensperger, Thomas; Birman, Serge; Stensmyr, Marcus C; Hansson, Bill S

    2014-01-01

    Many insect species are host-obligate specialists. The evolutionary mechanism driving the adaptation of a species to a toxic host is, however, intriguing. We analyzed the tight association of Drosophila sechellia to its sole host, the fruit of Morinda citrifolia, which is toxic to other members of the melanogaster species group. Molecular polymorphisms in the dopamine regulatory protein Catsup cause infertility in D. sechellia due to maternal arrest of oogenesis. In its natural host, the fruit compensates for the impaired maternal dopamine metabolism with the precursor l-DOPA, resuming oogenesis and stimulating egg production. l-DOPA present in morinda additionally increases the size of D. sechellia eggs, what in turn enhances early fitness. We argue that the need of l-DOPA for successful reproduction has driven D. sechellia to become an M. citrifolia obligate specialist. This study illustrates how an insect's dopaminergic system can sustain ecological adaptations by modulating ontogenesis and development. DOI: http://dx.doi.org/10.7554/eLife.03785.001 PMID:25487989

  20. Testing the competition-colonization trade-off with a 32-year study of a saxicolous lichen community.

    PubMed

    Pastore, A I; Prather, C M; Gornish, E S; Ryan, W H; Ellis, R D; Milleri, T E

    2014-02-01

    Competition-colonization trade-offs are theorized to be a mechanism of coexistence in communities structured by environmental fluctuations. But many studies that have tested for the trade-off have failed to detect it, likely because a spatiotemporally structured environment and many species assemblages are needed to adequately test for a competition-colonization trade-off. Here, we present a unique 32-year study of rock-dwelling lichens in New Mexico, USA, in which photographs were used to quantify lichen life history traits and interactions through time. These data allowed us to determine whether there were any trade-offs between traits associated with colonization and competition, as well as the relationship between diversity and disturbance in the community. We did not find evidence for a trade-off between competitive ability and colonization rate or any related life history traits. Interestingly, we did find a peak in all measures of species diversity at intermediate levels of disturbance, consistent with the intermediate disturbance hypothesis pattern. We suggest that the coexistence of the dominant species in this system is regulated by differences in persistence and growth rate mediating overgrowth competition rather than a competition-colonization trade-off.

  1. Trade-Offs between Silicon and Phenolic Defenses may Explain Enhanced Performance of Root Herbivores on Phenolic-Rich Plants.

    PubMed

    Frew, Adam; Powell, Jeff R; Sallam, Nader; Allsopp, Peter G; Johnson, Scott N

    2016-08-01

    Phenolic compounds play a role in plant defense against herbivores. For some herbivorous insects, particularly root herbivores, host plants with high phenolic concentrations promote insect performance and tissue consumption. This positive relationship between some insects and phenolics, however, could reflect a negative correlation with other plant defenses acting against insects. Silicon is an important element for plant growth and defense, particularly in grasses, as many grass species take up large amounts of silicon. Negative impact of a high silicon diet on insect herbivore performance has been reported aboveground, but is unreported for belowground herbivores. It has been hypothesized that some silicon accumulating plants exhibit a trade-off between carbon-based defense compounds, such as phenolics, and silicon-based defenses. Here, we investigated the impact of silicon concentrations and total phenolic concentrations in sugarcane roots on the performance of the root-feeding greyback canegrub (Dermolepida albohirtum). Canegrub performance was positively correlated with root phenolics, but negatively correlated with root silicon. We found a negative relationship in the roots between total phenolics and silicon concentrations. This suggests the positive impact of phenolic compounds on some insects may be the effect of lower concentrations of silicon compounds in plant tissue. This is the first demonstration of plant silicon negatively affecting a belowground herbivore.

  2. Assessing Social – Ecological Trade-Offs to Advance Ecosystem-Based Fisheries Management

    PubMed Central

    Voss, Rudi; Quaas, Martin F.; Schmidt, Jörn O.; Tahvonen, Olli; Lindegren, Martin; Möllmann, Christian

    2014-01-01

    Modern resource management faces trade-offs in the provision of various ecosystem goods and services to humanity. For fisheries management to develop into an ecosystem-based approach, the goal is not only to maximize economic profits, but to consider equally important conservation and social equity goals. We introduce such a triple-bottom line approach to the management of multi-species fisheries using the Baltic Sea as a case study. We apply a coupled ecological-economic optimization model to address the actual fisheries management challenge of trading-off the recovery of collapsed cod stocks versus the health of ecologically important forage fish populations. Management strategies based on profit maximization would rebuild the cod stock to high levels but may cause the risk of stock collapse for forage species with low market value, such as Baltic sprat (Fig. 1A). Economically efficient conservation efforts to protect sprat would be borne almost exclusively by the forage fishery as sprat fishing effort and profits would strongly be reduced. Unless compensation is paid, this would challenge equity between fishing sectors (Fig. 1B). Optimizing equity while respecting sprat biomass precautionary levels would reduce potential profits of the overall Baltic fishery, but may offer an acceptable balance between overall profits, species conservation and social equity (Fig. 1C). Our case study shows a practical example of how an ecosystem-based fisheries management will be able to offer society options to solve common conflicts between different resource uses. Adding equity considerations to the traditional trade-off between economy and ecology will greatly enhance credibility and hence compliance to management decisions, a further footstep towards healthy fish stocks and sustainable fisheries in the world ocean. PMID:25268117

  3. Army ants dynamically adjust living bridges in response to a cost–benefit trade-off

    PubMed Central

    Reid, Chris R.; Lutz, Matthew J.; Powell, Scott; Kao, Albert B.; Couzin, Iain D.; Garnier, Simon

    2015-01-01

    The ability of individual animals to create functional structures by joining together is rare and confined to the social insects. Army ants (Eciton) form collective assemblages out of their own bodies to perform a variety of functions that benefit the entire colony. Here we examine ‟bridges” of linked individuals that are constructed to span gaps in the colony’s foraging trail. How these living structures adjust themselves to varied and changing conditions remains poorly understood. Our field experiments show that the ants continuously modify their bridges, such that these structures lengthen, widen, and change position in response to traffic levels and environmental geometry. Ants initiate bridges where their path deviates from their incoming direction and move the bridges over time to create shortcuts over large gaps. The final position of the structure depended on the intensity of the traffic and the extent of path deviation and was influenced by a cost–benefit trade-off at the colony level, where the benefit of increased foraging trail efficiency was balanced by the cost of removing workers from the foraging pool to form the structure. To examine this trade-off, we quantified the geometric relationship between costs and benefits revealed by our experiments. We then constructed a model to determine the bridge location that maximized foraging rate, which qualitatively matched the observed movement of bridges. Our results highlight how animal self-assemblages can be dynamically modified in response to a group-level cost–benefit trade-off, without any individual unit’s having information on global benefits or costs. PMID:26598673

  4. Army ants dynamically adjust living bridges in response to a cost-benefit trade-off.

    PubMed

    Reid, Chris R; Lutz, Matthew J; Powell, Scott; Kao, Albert B; Couzin, Iain D; Garnier, Simon

    2015-12-08

    The ability of individual animals to create functional structures by joining together is rare and confined to the social insects. Army ants (Eciton) form collective assemblages out of their own bodies to perform a variety of functions that benefit the entire colony. Here we examine ‟bridges" of linked individuals that are constructed to span gaps in the colony's foraging trail. How these living structures adjust themselves to varied and changing conditions remains poorly understood. Our field experiments show that the ants continuously modify their bridges, such that these structures lengthen, widen, and change position in response to traffic levels and environmental geometry. Ants initiate bridges where their path deviates from their incoming direction and move the bridges over time to create shortcuts over large gaps. The final position of the structure depended on the intensity of the traffic and the extent of path deviation and was influenced by a cost-benefit trade-off at the colony level, where the benefit of increased foraging trail efficiency was balanced by the cost of removing workers from the foraging pool to form the structure. To examine this trade-off, we quantified the geometric relationship between costs and benefits revealed by our experiments. We then constructed a model to determine the bridge location that maximized foraging rate, which qualitatively matched the observed movement of bridges. Our results highlight how animal self-assemblages can be dynamically modified in response to a group-level cost-benefit trade-off, without any individual unit's having information on global benefits or costs.

  5. Assessing social--ecological trade-offs to advance ecosystem-based fisheries management.

    PubMed

    Voss, Rudi; Quaas, Martin F; Schmidt, Jörn O; Tahvonen, Olli; Lindegren, Martin; Möllmann, Christian

    2014-01-01

    Modern resource management faces trade-offs in the provision of various ecosystem goods and services to humanity. For fisheries management to develop into an ecosystem-based approach, the goal is not only to maximize economic profits, but to consider equally important conservation and social equity goals. We introduce such a triple-bottom line approach to the management of multi-species fisheries using the Baltic Sea as a case study. We apply a coupled ecological-economic optimization model to address the actual fisheries management challenge of trading-off the recovery of collapsed cod stocks versus the health of ecologically important forage fish populations. Management strategies based on profit maximization would rebuild the cod stock to high levels but may cause the risk of stock collapse for forage species with low market value, such as Baltic sprat (Fig. 1A). Economically efficient conservation efforts to protect sprat would be borne almost exclusively by the forage fishery as sprat fishing effort and profits would strongly be reduced. Unless compensation is paid, this would challenge equity between fishing sectors (Fig. 1B). Optimizing equity while respecting sprat biomass precautionary levels would reduce potential profits of the overall Baltic fishery, but may offer an acceptable balance between overall profits, species conservation and social equity (Fig. 1C). Our case study shows a practical example of how an ecosystem-based fisheries management will be able to offer society options to solve common conflicts between different resource uses. Adding equity considerations to the traditional trade-off between economy and ecology will greatly enhance credibility and hence compliance to management decisions, a further footstep towards healthy fish stocks and sustainable fisheries in the world ocean.

  6. A Reference-Dependent Regret Model for Deterministic Trade-off Studies

    SciTech Connect

    Kujawski, Edouard

    2005-02-25

    Today's typical multi-criteria decision analysis is based on classical expected utility theory that assumes a mythical ''Rational Individual'' immune to psychological influences such as anticipated regret. It is therefore in conflict with rational individuals who trade-off some benefits and forgo the alternative with the highest total classical utility for a more balanced alternative in order to reduce their levels of anticipated regret. This paper focuses on decision making under certainty. It presents a reference-dependent regret model (RDRM) in which the level of regret that an individual experiences depends on the absolute values rather than the differences of the utilities of the chosen and forgone alternatives. The RDRM best choice may differ from the conventional linear additive utility model, the analytic hierarchy process, and the regret theory of Bell and Loomes and Sugden. Examples are presented that indicate that RDRM is the better predictive descriptor for decision making under certainty. RDRM satisfies transitivity of the alternatives under pairwise comparisons and models rank reversal consistent with observed reasonable choices under dynamic or distinct situations. Like regret theory, the RDRM utilities of all the alternatives under consideration are interrelated. For complex trade-off studies regret is incorporated as an element of a cost-utility-regret analysis that characterizes each alternative in terms of its monetary cost, an aggregate performance utility, and a regret value. This provides decision makers adequate information to compare the alternatives and depending on their values they may trade-off some performance and/or cost to avoid high levels of regret. The result is a well-balanced alternative often preferred by reasonable decision makers to the optimal choice of classical multi-attribute utility analysis. The model can readily be extended to incorporate rejoicing to suit decision makers who seek it. The approach is illustrated using a

  7. Invasion versus isolation: trade-offs in managing native salmonids with barriers to upstream movement.

    PubMed

    Fausch, Kurt D; Rieman, Bruce E; Dunham, Jason B; Young, Michael K; Peterson, Douglas P

    2009-08-01

    Conservation biologists often face the trade-off that increasing connectivity in fragmented landscapes to reduce extinction risk of native species can foster invasion by non-native species that enter via the corridors created, which can then increase extinction risk. This dilemma is acute for stream fishes, especially native salmonids, because their populations are frequently relegated to fragments of headwater habitat threatened by invasion from downstream by 3 cosmopolitan non-native salmonids. Managers often block these upstream invasions with movement barriers, but isolation of native salmonids in small headwater streams can increase the threat of local extinction. We propose a conceptual framework to address this worldwide problem that focuses on 4 main questions. First, are populations of conservation value present (considering evolutionary legacies, ecological functions, and socioeconomic benefits as distinct values)? Second, are populations vulnerable to invasion and displacement by non-native salmonids? Third, would these populations be threatened with local extinction if isolated with barriers? And, fourth, how should management be prioritized among multiple populations? We also developed a conceptual model of the joint trade-off of invasion and isolation threats that considers the opportunities for managers to make strategic decisions. We illustrated use of this framework in an analysis of the invasion-isolation trade-off for native cutthroat trout (Oncorhynchus clarkii) in 2 contrasting basins in western North America where invasion and isolation are either present and strong or farther away and apparently weak. These cases demonstrate that decisions to install or remove barriers to conserve native salmonids are often complex and depend on conservation values, environmental context (which influences the threat of invasion and isolation), and additional socioeconomic factors. Explicit analysis with tools such as those we propose can help managers make

  8. Trade-offs between xylem hydraulic properties, wood anatomy and yield in Populus.

    PubMed

    Hajek, Peter; Leuschner, Christoph; Hertel, Dietrich; Delzon, Sylvain; Schuldt, Bernhard

    2014-07-01

    Trees face the dilemma that achieving high plant productivity is accompanied by a risk of drought-induced hydraulic failure due to a trade-off in the trees' vascular system between hydraulic efficiency and safety. By investigating the xylem anatomy of branches and coarse roots, and measuring branch axial hydraulic conductivity and vulnerability to cavitation in 4-year-old field-grown aspen plants of five demes (Populus tremula L. and Populus tremuloides Michx.) differing in growth rate, we tested the hypotheses that (i) demes differ in wood anatomical and hydraulic properties, (ii) hydraulic efficiency and safety are related to xylem anatomical traits, and (iii) aboveground productivity and hydraulic efficiency are negatively correlated to cavitation resistance. Significant deme differences existed in seven of the nine investigated branch-related anatomical and hydraulic traits but only in one of the four coarse-root-related anatomical traits; this likely is a consequence of high intra-plant variation in root morphology and the occurrence of a few 'high-conductivity roots'. Growth rate was positively related to branch hydraulic efficiency (xylem-specific conductivity) but not to cavitation resistance; this indicates that no marked trade-off exists between cavitation resistance and growth. Both branch hydraulic safety and hydraulic efficiency significantly depended on vessel size and were related to the genetic distance between the demes, while the xylem pressure causing 88% loss of hydraulic conductivity (P88 value) was more closely related to hydraulic efficiency than the commonly used P50 value. Deme-specific variation in the pit membrane structure may explain why vessel size was not directly linked to growth rate. We conclude that branch hydraulic efficiency is an important growth-influencing trait in aspen, while the assumed trade-off between productivity and hydraulic safety is weak.

  9. Exaggerated Trait Allometry, Compensation and Trade-Offs in the New Zealand Giraffe Weevil (Lasiorhynchus barbicornis)

    PubMed Central

    Painting, Christina. J.; Holwell, Gregory I.

    2013-01-01

    Sexual selection has driven the evolution of exaggerated traits among diverse animal taxa. The production of exaggerated traits can come at a cost to other traits through trade-offs when resources allocated to trait development are limited. Alternatively some traits can be selected for in parallel to support or compensate for the cost of bearing the exaggerated trait. Male giraffe weevils (Lasiorhynchus barbicornis) display an extremely elongated rostrum used as a weapon during contests for mates. Here we characterise the scaling relationship between rostrum and body size and show that males have a steep positive allometry, but that the slope is non-linear due to a relative reduction in rostrum length for the largest males, suggesting a limitation in resource allocation or a diminishing requirement for large males to invest increasingly into larger rostra. We also measured testes, wings, antennae, fore- and hind-tibia size and found no evidence of a trade-off between these traits and rostrum length when comparing phenotypic correlations. However, the relative length of wings, antennae, fore- and hind-tibia all increased with relative rostrum length suggesting these traits may be under correlational selection. Increased investment in wing and leg length is therefore likely to compensate for the costs of flying with, and wielding the exaggerated rostrum of larger male giraffe weevils. These results provide a first step in identifying the potential for trait compensation and trades-offs, but are phenotypic correlations only and should be interpreted with care in the absence of breeding experiments. PMID:24312425

  10. Carbon allocation during defoliation: testing a defense-growth trade-off in balsam fir

    PubMed Central

    Deslauriers, Annie; Caron, Laurie; Rossi, Sergio

    2015-01-01

    During repetitive defoliation events, carbon can become limiting for trees. To maintain growth and survival, the resources have to be shared more efficiently, which could result in a trade-off between the different physiological processes of a plant. The objective of this study was to assess the effect of defoliation in carbon allocation of balsam fir [Abies balsamea (L.) Mill.] to test the presence of a trade-off between allocation to growth, carbon storage, and defense. Three defoliation intensities [control (C-trees, 0% defoliation), moderately (M-trees, 41–60%), and heavily (H-trees, 61–80%) defoliated] were selected in order to monitor several variables related to stem growth (wood formation in xylem), carbon storage in stem and needle (non-structural soluble sugars and starch), and defense components in needles (terpenoids compound) from May to October 2011. The concentration of starch was drastically reduced in both wood and leaves of H-trees with a quasi-absence of carbon partitioning to storage in early summer. Fewer kinds of monoterpenes and sesquiterpenes were formed with an increasing level of defoliation indicating a lower carbon allocation for the production of defense. The carbon allocation to wood formation gradually reduced at increasing defoliation intensities, with a lower growth rate and fewer tracheids resulting in a reduced carbon sequestration in cell walls. The hypothesis of a trade-off between the allocations to defense components and to non-structural (NCS) and structural (growth) carbon was rejected as most of the measured variables decreased with increasing defoliation. The starch amount was highly indicative of the tree carbon status at different defoliation intensity and future research should focus on the mechanism of starch utilization for survival and growth following an outbreak. PMID:26029235

  11. Co-benefits and trade-offs in the water-energy nexus of irrigation modernization in China

    NASA Astrophysics Data System (ADS)

    Cremades, Roger; Rothausen, Sabrina G. S. A.; Conway, Declan; Zou, Xiaoxia; Wang, Jinxia; Li, Yu'e.

    2016-05-01

    There are strong interdependencies between water use in agriculture and energy consumption as water saving technologies can require increased pumping and pressurizing. The Chinese Government includes water efficiency improvement and carbon intensity reduction targets in the 12th Five-Year Plan (5YP. 2011-2015), yet the links between energy use and irrigation modernization are not always addressed in policy targets. Here we build an original model of the energy embedded in water pumping for irrigated agriculture and its related processes. The model is based on the physical processes of irrigation schemes and the implication of technological developments, comprising all processes from extraction and conveyance of water to its application in the field. The model uses data from government sources to assess policy targets for deployment of irrigation technologies, which aim to reduce water application and contribute to adaptation of Chinese agriculture to climate change. The consequences of policy targets involve co-beneficial outcomes that achieve water and energy savings, or trade-offs in which reduced water application leads to increasing greenhouse gas (GHG) emissions. We analyze irrigation efficiency and energy use in four significant provinces and nationally, using scenarios based on the targets of the 12th 5YP. At the national scale, we find that expansion of sprinklers and micro-irrigation as outlined in the 5YP would increase GHG emissions from agricultural water use, however, emissions decrease in those provinces with predominant groundwater use and planned expansion of low-pressure pipes. We show that the most costly technologies relate to trade-offs, while co-benefits are generally achieved with less expensive technologies. The investment cost per area of irrigation technology expansion does not greatly affect the outcome in terms of water, but in terms of energy the most expensive technologies are more energy-intensive and produce more emissions. The

  12. Vega roll and attitude control system algorithms trade-off study

    NASA Astrophysics Data System (ADS)

    Paulino, N.; Cuciniello, G.; Cruciani, I.; Corraro, F.; Spallotta, D.; Nebula, F.

    2013-12-01

    This paper describes the trade-off study for the selection of the most suitable algorithms for the Roll and Attitude Control System (RACS) within the FPS-A program, aimed at developing the new Flight Program Software of VEGA Launcher. Two algorithms were analyzed: Switching Lines (SL) and Quaternion Feedback Regulation. Using a development simulation tool that models two critical flight phases (Long Coasting Phase (LCP) and Payload Release (PLR) Phase), both algorithms were assessed with Monte Carlo batch simulations for both of the phases. The statistical outcomes of the results demonstrate a 100 percent success rate for Quaternion Feedback Regulation, and support the choice of this method.

  13. The growth-defense trade-off and habitat specialization by plants in Amazonian forests.

    PubMed

    Fine, Paul V A; Miller, Zachariah J; Mesones, Italo; Irazuzta, Sebastian; Appel, Heidi M; Stevens, M Henry H; Sääksjärvi, Ilari; Schultz, Jack C; Coley, Phyllis D

    2006-07-01

    Tropical forests include a diversity of habitats, which has led to specialization in plants. Near Iquitos, in the Peruvian Amazon, nutrient-rich clay forests surround nutrient-poor white-sand forests, each harboring a unique composition of habitat specialist trees. We tested the hypothesis that the combination of impoverished soils and herbivory creates strong natural selection for plant defenses in white-sand forest, while rapid growth is favored in clay forests. Recently, we reported evidence from a reciprocal-transplant experiment that manipulated the presence of herbivores and involved 20 species from six genera, including phylogenetically independent pairs of closely related white-sand and clay specialists. When protected from herbivores, clay specialists exhibited faster growth rates than white-sand specialists in both habitats. But, when unprotected, white-sand specialists outperformed clay specialists in white-sand habitat, and clay specialists outperformed white-sand specialists in clay habitat. Here we test further the hypothesis that the growth defense trade-off contributes to habitat specialization by comparing patterns of growth, herbivory, and defensive traits in these same six genera of white-sand and clay specialists. While the probability of herbivore attack did not differ between the two habitats, an artificial defoliation experiment showed that the impact of herbivory on plant mortality was significantly greater in white-sand forests. We quantified the amount of terpenes, phenolics, leaf toughness, and available foliar protein for the plants in the experiment. Different genera invested in different defensive strategies, and we found strong evidence for phylogenetic constraint in defense type. Overall, however, we found significantly higher total defense investment for white-sand specialists, relative to their clay specialist congeners. Furthermore, herbivore resistance consistently exhibited a significant trade-off against growth rate in each of

  14. Inbreeding-related trade-offs in stress resistance in the ant Formica exsecta.

    PubMed

    Freitak, D; Bos, N; Stucki, D; Sundström, L

    2014-11-01

    Inbred individuals and populations are predicted to suffer from inbreeding depression, especially in times of stress. Under natural conditions, organisms are exposed to more than one stressor at any one time, highlighting the importance of stress resistance traits. We studied how inbreeding- and immunity-related traits are correlated under different dietary conditions in the ant Formica exsecta. Its natural diet varies in the amount and nature of plant secondary compounds and the level of free radicals, all of which require detoxification to maintain organismal homeostasis. We found that inbreeding decreased general antibacterial activity under dietary stress, suggesting inbreeding-related physiological trade-offs.

  15. Science requirements and trade-offs for the MOSAIC instrument for the European ELT

    NASA Astrophysics Data System (ADS)

    Evans, C. J.; Puech, M.; Rodrigues, M.; Barbuy, B.; Cuby, J.-G.; Dalton, G.; Fitzsimons, E.; Hammer, F.; Jagourel, P.; Kaper, L.; Morris, S. L.; Morris, T. J.

    2016-08-01

    Building on the comprehensive White Paper on the scientific case for multi-object spectroscopy on the European ELT, we present the top-level instrument requirements that are being used in the Phase A design study of the MOSAIC concept. The assembled cases span the full range of E-ELT science and generally require either `high multiplex' or 'high definition' observations to best exploit the excellent sensitivity and spatial performance of the telescope. We highlight some of the science studies that are now being used in trade-off studies to inform the capabilities of MOSAIC and its technical design.

  16. Emerging asymmetric interactions between forage and predator fisheries impose management trade-offs.

    PubMed

    Houle, J E; Andersen, K H; Farnsworth, K D; Reid, D G

    2013-10-01

    A size and trait-based marine community model was used to investigate interactions, with potential implications for yields, when a fishery targeting forage fish species (whose main adult diet is zooplankton) co-occurs with a fishery targeting larger-sized predator species. Predicted effects on the size structure of the fish community, growth and recruitment of fishes, and yield from the fisheries were used to identify management trade-offs among the different fisheries. Results showed that moderate fishing on forage fishes imposed only small effects on predator fisheries, whereas predator fisheries could enhance yield from forage fisheries under some circumstances.

  17. Towards an Optimal Noise Versus Resolution Trade-Off in Wind Scatterometry

    NASA Technical Reports Server (NTRS)

    Williams, Brent A.

    2011-01-01

    A scatterometer is a radar that measures the normalized radar cross section sigma(sup 0) of the Earth's surface. Over the ocean this signal is related to the wind via the geophysical model function (GMF). The objective of wind scatterometry is to estimate the wind vector field from sigma(sup 0) measurements; however, there are many subtleties that complicate this problem-making it difficult to obtain a unique wind field estimate. Conventionally, wind estimation is split into two stages: a wind retrieval stage in which several ambiguous solutions are obtained, and an ambiguity removal stage in which ambiguities are chosen to produce an appropriate wind vector field estimate. The most common approach to wind field estimation is to grid the scatterometer swath into wind vector cells and estimate wind vector ambiguities independently for each cell. Then, field wise structure is imposed on the solution by an ambiguity selection routine. Although this approach is simple and practical, it neglects field wise structure in the retrieval step and does not account for the spatial correlation imposed by the sampling. This makes it difficult to develop a theoretically appropriate noise versus resolution trade-off using pointwise retrieval. Fieldwise structure may be imposed in the retrieval step using a model-based approach. However, this approach is generally only practical if a low order wind field model is applied, which may discard more information than is desired. Furthermore, model-based approaches do not account for the structure imposed by the sampling. A more general fieldwise approach is to estimate all the wind vectors for all the WVCs simultaneously from all the measurements. This approach can account for structure of the wind field as well as structure imposed by the sampling in the wind retrieval step. Williams and Long in 2010 developed a fieldwise retrieval method based on maximum a posteriori estimation (MAP). This MAP approach can be extended to perform a

  18. Trade-offs among ecosystem services in a typical Karst watershed, SW China.

    PubMed

    Tian, Yichao; Wang, Shijie; Bai, Xiaoyong; Luo, Guangjie; Xu, Yan

    2016-10-01

    Nowadays, most research results on ecosystem services in Karst areas are limited to a single function of an ecosystem service. Few scholars conduct a comparative study on the mutual relationships among ecosystem services, let alone reveal the trade-off and synergic relationships in typical Karst watershed. This research aims to understand and quantitatively evaluate the relationships among ecosystem services in a typical Karst watershed, broaden the depth and width of trade-off and synergic relationships in ecosystem services and explore a set of technical processes involved in these relationships. With the Shibantang Karst watershed in China as the research site, we explore the trade-off and synergic relationships of net primary productivity (NPP), water yield, and sediment yield by coupling Soil and Water Assessment Tool (SWAT) and Carnegie-Ames-Stanford Approach (CASA), and simulating and evaluating these three ecosystem services between 2000 and 2010. Results of this study are as follows. (1) The annual average water yield decreased from 528mm in 2000 to 513mm in 2010, decreasing by 2.84%. (2) The annual average sediment yield decreased from 26.15t/ha in 2000 to 23.81t/ha in 2010, with an average annual reduction of 0.23t/ha. (3) The annual average NPP increased from 739.38gCm(-2)a(-1) in 2000 to 746.25gCm(-2)a(-1) in 2010, increasing by 6.87gCm(-2)a(-1) . (4) Water yield and sediment yield are in a synergic relationship. The increase of water yield can accumulate the soil erosion amount. NPP is in a trade-off relationship with water yield and sediment yield. The improvement of NPP is good for decreasing water yield and soil erosion amount and increasing soil conservation amount. This study provides policy makers and planners an approach to develop an integrated model, as well as design mapping and monitoring protocols for land use change and ecosystem service assessments.

  19. Design for manufacturability and optical performance trade-offs using precision glass molded aspheric lenses

    NASA Astrophysics Data System (ADS)

    Symmons, Alan; Huddleston, Jeremy; Knowles, Dennis

    2016-09-01

    Precision glass molding (PGM) enables high-performance, low-cost lens designs through aspheric shapes and a broad array of moldable glass types. While these benefits bring a high potential value, the design of PGM lenses must be skillfully approached to balance manufacturability and cost considerations. Different types of mold tooling and processes used by PGM suppliers can also lead to confusion regarding the manufacturing parameters and design rules that should be considered. The authors discuss the various factors that can affect manufacturability and cost of lenses made to PGM standards, and present a case study to demonstrate the trade-offs in performance.

  20. Trade-off between information format and capacity in the olfactory system.

    PubMed

    Aldworth, Zane N; Stopfer, Mark A

    2015-01-28

    As information about the sensory environment passes between layers within the nervous system, the format of the information often changes. To examine how information format affects the capacity of neurons to represent stimuli, we measured the rate of information transmission in olfactory neurons in intact, awake locusts (Schistocerca americana) while pharmacologically manipulating patterns of correlated neuronal activity. Blocking the periodic inhibition underlying odor-elicited neural oscillatory synchronization increased information transmission rates. This suggests oscillatory synchrony, which serves other information processing roles, comes at a cost to the speed with which neurons can transmit information. Our results provide an example of a trade-off between benefits and costs in neural information processing.

  1. Universal Trade-Off Relation between Power and Efficiency for Heat Engines

    NASA Astrophysics Data System (ADS)

    Shiraishi, Naoto; Saito, Keiji; Tasaki, Hal

    2016-11-01

    For a general thermodynamic system described as a Markov process, we prove a general lower bound for dissipation in terms of the square of the heat current, thus establishing that nonvanishing current inevitably implies dissipation. This leads to a universal trade-off relation between efficiency and power, with which we rigorously prove that a heat engine with nonvanishing power never attains the Carnot efficiency. Our theory applies to systems arbitrarily far from equilibrium, and does not assume any specific symmetry of the model.

  2. Evidence for a temperature acclimation mechanism in bacteria: an empirical test of a membrane-mediated trade-off

    USGS Publications Warehouse

    Hall, Edward K.; Singer, Gabriel A.; Kainz, Martin J.; Lennon, Jay T.

    2010-01-01

    1. Shifts in bacterial community composition along temporal and spatial temperature gradients occur in a wide range of habitats and have potentially important implications for ecosystem functioning. However, it is often challenging to empirically link an adaptation or acclimation that defines environmental niche or biogeography with a quantifiable phenotype, especially in micro-organisms. 2. Here we evaluate a possible mechanistic explanation for shifts in bacterioplankton community composition in response to temperature by testing a previously hypothesized membrane mediated trade-off between resource acquisition and respiratory costs. 3. We isolated two strains of Flavobacterium sp. at two temperatures (cold isolate and warm isolate) from the epilimnion of a small temperate lake in North Central Minnesota. 4. Compared with the cold isolate the warm isolate had higher growth rate, higher carrying capacity, lower lag time and lower respiration at the high temperature and lower phosphorus uptake at the low temperature. We also observed significant differences in membrane lipid composition between isolates and between environments that were consistent with adjustments necessary to maintain membrane fluidity at different temperatures. 5. Our results suggest that temperature acclimation in planktonic bacteria is, in part, a resource-dependent membrane-facilitated phenomenon. This study provides an explicit example of how a quantifiable phenotype can be linked through physiology to competitive ability and environmental niche.

  3. Breaking the trade-off: rainforest bats maximize bandwidth and repetition rate of echolocation calls as they approach prey.

    PubMed

    Schmieder, Daniela A; Kingston, Tigga; Hashim, Rosli; Siemers, Björn M

    2010-10-23

    Both mammals and birds experience a performance trade-off between producing vocalizations with high bandwidths and at high repetition rate. Echolocating bats drastically increase repetition rate from 2-20 calls s(-1) up to about 170 calls s(-1) prior to intercepting airborne prey in order to accurately track prey movement. In turn, bandwidth drops to about 10-30 kHz for the calls of this 'final buzz'. We have now discovered that Southeast Asian rainforest bats (in the vespertilionid subfamilies Kerivoulinae and Murininae) are able to maintain high call bandwidths at very high repetition rates throughout approach to prey. Five species of Kerivoula and Phoniscus produced call bandwidths of between 78 and 170 kHz at repetition rates of 140-200 calls s(-1) and two of Murina at 80 calls s(-1). The 'typical' and distinct drop in call frequency was present in none of the seven species. This stands in striking contrast to our present view of echolocation during approach to prey in insectivorous bats, which was established largely based on European and American members of the same bat family, the Vespertilionidae. Buzz calls of Kerivoula pellucida had mean bandwidths of 170 kHz and attained maximum starting frequencies of 250 kHz which makes them the most broadband and most highly pitched tonal animal vocalization known to date. We suggest that the extreme vocal performance of the Kerivoulinae and Murininae evolved as an adaptation to echolocating and tracking arthropods in the dense rainforest understorey.

  4. Adaptation of HIV-1 to its human host.

    PubMed

    Wain, Louise V; Bailes, Elizabeth; Bibollet-Ruche, Frederic; Decker, Julie M; Keele, Brandon F; Van Heuverswyn, Fran; Li, Yingying; Takehisa, Jun; Ngole, Eitel Mpoudi; Shaw, George M; Peeters, Martine; Hahn, Beatrice H; Sharp, Paul M

    2007-08-01

    Human immunodeficiency virus type 1 (HIV-1) originated from three independent cross-species transmissions of simian immunodeficiency virus (SIVcpzPtt) infecting chimpanzees (Pan troglodytes troglodytes) in west central Africa, giving rise to pandemic (group M) and non-pandemic (groups N and O) clades of HIV-1. To identify host-specific adaptations in HIV-1 we compared the inferred ancestral sequences of HIV-1 groups M, N and O to 12 full length genome sequences of SIVcpzPtt and four of the outlying but closely related SIVcpzPts (from P. t. schweinfurthii). This analysis revealed a single site that was completely conserved among SIVcpzPtt strains but different (due to the same change) in all three groups of HIV-1. This site, Gag-30, lies within p17, the gag-encoded matrix protein. It is Met in SIVcpzPtt, underwent a conservative replacement by Leu in one lineage of SIVcpzPts but changed radically to Arg on all three lineages leading to HIV-1. During subsequent diversification this site has been conserved as a basic residue (Arg or Lys) in most lineages of HIV-1. Retrospective analysis revealed that Gag-30 had reverted to Met in a previous experiment in which HIV-1 was passaged through chimpanzees. To examine whether this substitution conferred a species specific growth advantage, we used site-directed mutagenesis to generate variants of these chimpanzee-adapted HIV-1 strains with Lys at Gag-30, and tested their replication in both human and chimpanzee CD4+ T lymphocytes. Remarkably, viruses encoding Met replicated to higher titers than viruses encoding Lys in chimpanzee T cells, but the opposite was found in human T cells. Taken together, these observations provide compelling evidence for host-specific adaptation during the emergence of HIV-1 and identify the viral matrix protein as a modulator of viral fitness following transmission to the new human host.

  5. Androgens predict parasitism in female meerkats: a new perspective on a classic trade-off.

    PubMed

    Smyth, Kendra N; Greene, Lydia K; Clutton-Brock, Tim; Drea, Christine M

    2016-10-01

    The immunocompetence handicap hypothesis posits that androgens in males can be a 'double-edged sword', actively promoting reproductive success, while also negatively impacting health. Because there can be both substantial androgen concentrations in females and significant androgenic variation among them, particularly in species portraying female social dominance over males or intense female-female competition, androgens might also play a role in mediating female health and fitness. We examined this hypothesis in the meerkat (Suricata suricatta), a cooperatively breeding, social carnivoran characterized by aggressively mediated female social dominance and extreme rank-related reproductive skew. Dominant females also have greater androgen concentrations and harbour greater parasite loads than their subordinate counterparts, but the relationship between concurrent androgen concentrations and parasite burdens is unknown. We found that a female's faecal androgen concentrations reliably predicted her concurrent state of endoparasitism irrespective of her social status: parasite species richness and infection by Spirurida nematodes, Oxynema suricattae, Pseudandrya suricattae and coccidia were greater with greater androgen concentrations. Based on gastrointestinal parasite burdens, females appear to experience the same trade-off in the costs and benefits of raised androgens as do the males of many species. This trade-off presumably represents a health cost of sexual selection operating in females.

  6. The person-trade-off approach to valuing health care programs.

    PubMed

    Nord, E

    1995-01-01

    The person-trade-off technique is a way of estimating the social values of different health care interventions. Basically it consists in asking people how many outcomes of one kind they consider equivalent in social value to X outcomes of another kind. The paper outlines a number of the author's previous studies using the technique. The studies suggest that while the technique is theoretically appealing for resource-allocation purposes, it is in practice quite demanding. It needs to be applied in fairly large groups of subjects to keep random measurement error at an acceptable level. Possible framing effects include the effects of argument presentation and the choice of start points in numerical exercises. To control for these effects, it seems important to take subjects through a multistep procedure, in which they are induced to carefully consider the various arguments that might be relevant in each exercise and to reconsider initial responses in the light of their implications. The investigator must also think through which decision context he or she wishes to study and make his or her choice of context very clear when reporting the results. In spite of these problems, the person-trade-off technique deserves greater attention in the field of cost-utility analysis.

  7. A phase transition model for the speed-accuracy trade-off in response time experiments.

    PubMed

    Dutilh, Gilles; Wagenmakers, Eric-Jan; Visser, Ingmar; van der Maas, Han L J

    2011-03-01

    Most models of response time (RT) in elementary cognitive tasks implicitly assume that the speed-accuracy trade-off is continuous: When payoffs or instructions gradually increase the level of speed stress, people are assumed to gradually sacrifice response accuracy in exchange for gradual increases in response speed. This trade-off presumably operates over the entire range from accurate but slow responding to fast but chance-level responding (i.e., guessing). In this article, we challenge the assumption of continuity and propose a phase transition model for RTs and accuracy. Analogous to the fast guess model (Ollman, 1966), our model postulates two modes of processing: a guess mode and a stimulus-controlled mode. From catastrophe theory, we derive two important predictions that allow us to test our model against the fast guess model and against the popular class of sequential sampling models. The first prediction--hysteresis in the transitions between guessing and stimulus-controlled behavior--was confirmed in an experiment that gradually changed the reward for speed versus accuracy. The second prediction--bimodal RT distributions--was confirmed in an experiment that required participants to respond in a way that is intermediate between guessing and accurate responding.

  8. Trade-off between competition and facilitation defines gap colonization in mountains

    PubMed Central

    Lembrechts, Jonas J.; Milbau, Ann; Nijs, Ivan

    2015-01-01

    Recent experimental observations show that gap colonization in small-stature (e.g. grassland and dwarf shrubs) vegetation strongly depends on the abiotic conditions within them. At the same time, within-gap variation in biotic interactions such as competition and facilitation, caused by distance to the gap edge, would affect colonizer performance, but a theoretical framework to explore such patterns is missing. Here, we model how competition, facilitation and environmental conditions together determine the small-scale patterns of gap colonization along a cold gradient in mountains, by simulating colonizer survival in gaps of various sizes. Our model adds another dimension to the known effects of biotic interactions along a stress gradient by focussing on the trade-off between competition and facilitation in the within-gap environment. We show that this trade-off defines a peak in colonizer survival at a specific distance from the gap edge, which progressively shifts closer to the edge as the environment gets colder, ultimately leaving a large fraction of gaps unsuitable for colonization in facilitation-dominated systems. This is reinforced when vegetation size and temperature amelioration are manipulated simultaneously with temperature in order to simulate an elevational gradient more realistically. Interestingly, all other conditions being equal, the magnitude of the realized survival peak was always lower in large than in small gaps, making large gaps harder to colonize. The model is relevant to predict effects of non-native plant invasions and climate warming on colonization processes in mountains. PMID:26558706

  9. A trade-off solution between model resolution and covariance in surface-wave inversion

    USGS Publications Warehouse

    Xia, J.; Xu, Y.; Miller, R.D.; Zeng, C.

    2010-01-01

    Regularization is necessary for inversion of ill-posed geophysical problems. Appraisal of inverse models is essential for meaningful interpretation of these models. Because uncertainties are associated with regularization parameters, extra conditions are usually required to determine proper parameters for assessing inverse models. Commonly used techniques for assessment of a geophysical inverse model derived (generally iteratively) from a linear system are based on calculating the model resolution and the model covariance matrices. Because the model resolution and the model covariance matrices of the regularized solutions are controlled by the regularization parameter, direct assessment of inverse models using only the covariance matrix may provide incorrect results. To assess an inverted model, we use the concept of a trade-off between model resolution and covariance to find a proper regularization parameter with singular values calculated in the last iteration. We plot the singular values from large to small to form a singular value plot. A proper regularization parameter is normally the first singular value that approaches zero in the plot. With this regularization parameter, we obtain a trade-off solution between model resolution and model covariance in the vicinity of a regularized solution. The unit covariance matrix can then be used to calculate error bars of the inverse model at a resolution level determined by the regularization parameter. We demonstrate this approach with both synthetic and real surface-wave data. ?? 2010 Birkh??user / Springer Basel AG.

  10. Speed-accuracy trade-off in skilled typewriting: decomposing the contributions of hierarchical control loops.

    PubMed

    Yamaguchi, Motonori; Crump, Matthew J C; Logan, Gordon D

    2013-06-01

    Typing performance involves hierarchically structured control systems: At the higher level, an outer loop generates a word or a series of words to be typed; at the lower level, an inner loop activates the keystrokes comprising the word in parallel and executes them in the correct order. The present experiments examined contributions of the outer- and inner-loop processes to the control of speed and accuracy in typewriting. Experiments 1 and 2 involved discontinuous typing of single words, and Experiments 3 and 4 involved continuous typing of paragraphs. Across experiments, typists were able to trade speed for accuracy but were unable to type at rates faster than 100 ms/keystroke, implying limits to the flexibility of the underlying processes. The analyses of the component latencies and errors indicated that the majority of the trade-offs were due to inner-loop processing. The contribution of outer-loop processing to the trade-offs was small, but it resulted in large costs in error rate. Implications for strategic control of automatic processes are discussed.

  11. Prefrontal connections express individual differences in intrinsic resistance to trading off honesty values against economic benefits

    PubMed Central

    Dogan, Azade; Morishima, Yosuke; Heise, Felix; Tanner, Carmen; Gibson, Rajna; Wagner, Alexander F.; Tobler, Philippe N.

    2016-01-01

    Individuals differ profoundly when they decide whether to tell the truth or to be dishonest, particularly in situations where moral motives clash with economic motives, i.e., when truthfulness comes at a monetary cost. These differences should be expressed in the decision network, particularly in prefrontal cortex. However, the interactions between the core players of the decision network during honesty-related decisions involving trade-offs with economic costs remain poorly understood. To investigate brain connectivity patterns associated with individual differences in responding to economic costs of truthfulness, we used functional magnetic resonance imaging and measured brain activations, while participants made decisions concerning honesty. We found that in participants who valued honesty highly, dorsolateral and dorsomedial parts of prefrontal cortex were more tightly coupled with the inferior frontal cortex when economic costs were high compared to when they were low. Finer-grained analysis revealed that information flow from the inferior frontal cortex to the dorsolateral prefrontal cortex and bidirectional information flow between the inferior frontal cortex and dorsomedial prefrontal cortex was associated with a reduced tendency to trade off honesty for economic benefits. Our findings provide a novel account of the neural circuitry that underlies honest decisions in the face of economic temptations. PMID:27646044

  12. Parents face quantity–quality trade-offs between reproduction and investment in offspring in Iceland

    PubMed Central

    Lynch, Robert Francis

    2016-01-01

    How to optimally allocate time, energy and investment in an effort to maximize one's reproductive success is a fundamental problem faced by all organisms. This effort is complicated when the production of each additional offspring dilutes the total resources available for parental investment. Although a quantity–quality trade-off between producing and investing in offspring has long been assumed in evolutionary biology, testing it directly in humans is difficult, partly owing to the long generation time of our species. Using data from an Icelandic genealogy (Íslendingabók) over two centuries, I address this issue and analyse the quantity–quality trade-off in humans. I demonstrate that the primary impact of parents on the fitness of their children is the result of resources and or investment, but not genes. This effect changes significantly across time, in response to environmental conditions. Overall, increasing reproduction has negative fitness consequences on offspring, such that each additional sibling reduces an individual's average lifespan and lifetime reproductive success. This analysis provides insights into the evolutionary conflict between producing and investing in children while also shedding light on some of the causes of the demographic transition. PMID:27293787

  13. Process of selecting completion or workover fluids requires series of trade offs

    SciTech Connect

    Meyer, R.L.; Higueras, R.

    1984-01-30

    Good fluid design requires a series of trade-offs to match cost against formation needs. Here are the fundamentals and current technology for workover or completion fluids along with guidance for the trade-off choices. A completion fluid can be broadly defined as any borehole fluid placed across the producing zone prior to bringing a new well in. Workover fluids are used during remedial work on a well which has been on production for a period of time. Both fluids have the same goal: to maximize the recovery of hydrocarbons from the producing reservoir. This article presents an overview of completion and workover fluids specifically designed to maximize the recovery of hydrocarbons. Poor productivity of promising new wells, or reworked old wells, can almost always be traced to undesirable characteristics of the borehole fluid used in the completion or workover operation. For this reason, considerable care and planning should always go into the selection of these fluids. Many factors should be considered, keeping in mind that compromises often must be made. The secret to handling completion or workover fluids is to keep them clean. They should contain no particulate matter considered damaging to the formation. If handling equipment is not clean, then the expense and effort used to secure clean, uncontaminated completion or workover fluid is wasted.

  14. Fundamental rate-loss trade-off for the quantum internet

    NASA Astrophysics Data System (ADS)

    Azuma, Koji; Mizutani, Akihiro; Lo, Hoi-Kwong

    2016-11-01

    The quantum internet holds promise for achieving quantum communication--such as quantum teleportation and quantum key distribution (QKD)--freely between any clients all over the globe, as well as for the simulation of the evolution of quantum many-body systems. The most primitive function of the quantum internet is to provide quantum entanglement or a secret key to two points efficiently, by using intermediate nodes connected by optical channels with each other. Here we derive a fundamental rate-loss trade-off for a quantum internet protocol, by generalizing the Takeoka-Guha-Wilde bound to be applicable to any network topology. This trade-off has essentially no scaling gap with the quantum communication efficiencies of protocols known to be indispensable to long-distance quantum communication, such as intercity QKD and quantum repeaters. Our result--putting a practical but general limitation on the quantum internet--enables us to grasp the potential of the future quantum internet.

  15. Separating behavioral and physiological mechanisms in testosterone-mediated trade-offs.

    PubMed

    Mougeot, François; Redpath, Stephen M; Piertney, Stuart B; Hudson, Peter J

    2005-08-01

    Testosterone often mediates trade-offs between reproduction and other life-history traits, which are usually investigated using testosterone implants. However, this approach does not distinguish between the physiological and behavioral effects of testosterone. We studied a wild game bird, the red grouse Lagopus lagopus scoticus, and took a new approach to investigate mechanisms linking elevated testosterone to increased parasite intensity. We caught males in autumn, removed their parasites, implanted them with the antiandrogen flutamide in combination with an aromatase inhibitor (FA males) or with empty implants (control males), and challenged them with parasites. The FA treatment increased testosterone concentration and physiological stress, but without enhancing testosterone-dependent behaviors, because testosterone receptors were blocked. FA males ended up with more parasites than the control males the following autumn, an effect similar to that of a testosterone treatment reported elsewhere. However, and unlike the testosterone treatment, the FA treatment did not affect home range, pairing, or breeding success. The results supported a physiological mechanism (increased susceptibility) linking elevated testosterone and increased parasite intensity. The FA treatment provided a new way of investigating testosterone-mediated trade-offs whereby testosterone concentration was increased while the effects on behavior were blocked, resulting in physiological costs without phenotypic benefits.

  16. [Trade-offs in the development of various dosage form (overview)].

    PubMed

    Uchida, Takahiro

    2015-01-01

    In this symposium we focused on trade-offs which might occur in the process of development of many types of formulation and corresponding dissolution methods. Firstly, we focused on a solubility-permeability trade-off in the case of micelle with surfactant or molecular complex with CyD. The micelle would be successful in increasing drug solubility, however it rather decreased permeability of model drug progesterone (Biopharmaceutics Classfication System (BCS) Class II) as an overall flux. Secondly in order to reduce bitterness of branched chain amino acid (BCAA), increasing particle sizes of each amino acid crystals involved in formulation was effective since the release rate of amino acid was restricted efficiently. Thirdly, in the case of injection of paclitaxel (BCS Class II)formulation, the drug was adsorbed to albumin. Thereby the risk of allergy was dramatically decreased compared to the case when non-ionic surfactant was used as an additive. Fourth, anticancer drug was incorporated into the internal (core) phase of an orally disintegrating tablet (ODT), this is also merit to avoid exposure of the drug to a nursing person or individual working person in manufacturing process. Fifth, the convenient syringe type kit pharmaceutical preparation for administration of total parenteral nutrition (TPN) to avoid incompatibility and its risk management effect was briefly discussed. Finally, the risk of an additive such as alcohol for a preterm infant was described.

  17. Second-generation mobile satellite system. A conceptual design and trade-off study

    NASA Technical Reports Server (NTRS)

    Sue, M. K.; Park, Y. H.

    1985-01-01

    In recent years, interest has grown in the mobile satellite (MSAT) system, a satellite-based communications system capable of providing integrated voice and data services to a large number of users. To explore the potential of a commercial mobile satellite system (MSS) beyond the horizon of the first generation, using technologies of the 1990's and to assist MSAT-X in directing its efforts, a conceptual design has been performed for a second-generation system to be launched around the mid-1990's. The design goal is to maximize the number of satellite channels and/or minimize the overall life-cycle cost, subject to the constraint of utilizing a commercial satellite bus with minimum modifications. To provide an optimal design, a series of trade-offs are performed, including antenna sizing, feed configurations, and interference analysis. Interference is a serious problem for MSAT and often an overlapping feed design is required to reduce interbeam interference. The trade-off studies will show that a simple non-overlapping feed is sufficient for the second-generation system, thus avoiding the need for the complicated beam-forming network that is associated with the overlapping feed designs. In addition, a system that operates at L-band, an alternative frequency band that is being considered by some for possible MSAT applications, is also presented.

  18. An alternative approach to establishing trade-offs among greenhouse gases.

    PubMed

    Manne, A S; Richels, R G

    2001-04-05

    The Kyoto Protocol permits countries to meet part of their emission reduction obligations by cutting back on gases other than CO2 (ref. 1). This approach requires a definition of trade-offs among the radiatively active gases. The Intergovernmental Panel on Climate Change has suggested global warming potentials for this purpose, which use the accumulated radiative forcing of each gas by a set time horizon to establish emission equivalence. But it has been suggested that this approach has serious shortcomings: damages or abatement costs are not considered and the choice of time horizon for calculating cumulative radiative force is critical, but arbitrary. Here we describe an alternative framework for determining emission equivalence between radiatively active gases that addresses these weaknesses. We focus on limiting temperature change and rate of temperature change, but our framework is also applicable to other objectives. For a proposed ceiling, we calculate how much one should be willing to pay for emitting an additional unit of each gas. The relative prices then determine the trade-off between gases at each point in time, taking into account economical as well as physical considerations. Our analysis shows that the relative prices are sensitive to the lifetime of the gases, the choice of target and the proximity of the target, making short-lived gases more expensive to emit as we approach the prescribed ceiling.

  19. Trade-offs between soil hydrology and plant disease effects after biochar amendment in sandy soil

    NASA Astrophysics Data System (ADS)

    Verheijen, Frank; Silva, Flavio; Amaro, Antonio; Pinto, Gloria; Mesquita, Raquel; Jesus, Claudia; Alves, Artur; Keizer, Jacob

    2015-04-01

    Biochar can affect multiple soil-based ecosystem services to varying extents, leading to trade-offs. Improvements in plant-available water have predominantly been found at high biochar application rates in sandy soils. Reductions in plant diseases after biochar application have been found in various horticultural plants, and trees such as maple and oak, mostly at relatively low biochar application rates. Serious damage to Eucalyptus globulus has been reported since 1999 when frequent and severe defoliation of young trees was observed, and eucalypts are the major tree species in commercial forestry plantations of Portugal, forming an important economic activity. Here we investigated simultaneous effects on plant available water and on disease suppression of eucalypt, in a completely randomised full factorial greenhouse pot experiment, using a range of woody feedstock biochar concentrations in sandy soil. Treatments included plant inoculation with the fungus Neofusicoccum kwambonambiense and cycles of acute drought stress. Preliminary results showed delayed wilting for plants treated with 3-6% biochar, but also increased stem lesion length. These results suggest a trade-off between effects on water availability and disease for Eucalyptus globulus plants in the selected sandy soil amended with this specific biochar, at the selected application rates.

  20. Trade-offs between driving nodes and time-to-control in complex networks

    NASA Astrophysics Data System (ADS)

    Pequito, Sérgio; Preciado, Victor M.; Barabási, Albert-László; Pappas, George J.

    2017-01-01

    Recent advances in control theory provide us with efficient tools to determine the minimum number of driving (or driven) nodes to steer a complex network towards a desired state. Furthermore, we often need to do it within a given time window, so it is of practical importance to understand the trade-offs between the minimum number of driving/driven nodes and the minimum time required to reach a desired state. Therefore, we introduce the notion of actuation spectrum to capture such trade-offs, which we used to find that in many complex networks only a small fraction of driving (or driven) nodes is required to steer the network to a desired state within a relatively small time window. Furthermore, our empirical studies reveal that, even though synthetic network models are designed to present structural properties similar to those observed in real networks, their actuation spectra can be dramatically different. Thus, it supports the need to develop new synthetic network models able to replicate controllability properties of real-world networks.

  1. Discovery–dominance trade-off among widespread invasive ant species

    PubMed Central

    Bertelsmeier, Cleo; Avril, Amaury; Blight, Olivier; Jourdan, Hervé; Courchamp, Franck

    2015-01-01

    Ants are among the most problematic invasive species. They displace numerous native species, alter ecosystem processes, and can have negative impacts on agriculture and human health. In part, their success might stem from a departure from the discovery–dominance trade-off that can promote co-existence in native ant communities, that is, invasive ants are thought to be at the same time behaviorally dominant and faster discoverers of resources, compared to native species. However, it has not yet been tested whether similar asymmetries in behavioral dominance, exploration, and recruitment abilities also exist among invasive species. Here, we establish a dominance hierarchy among four of the most problematic invasive ants (Linepithema humile, Lasius neglectus, Wasmannia auropunctata, Pheidole megacephala) that may be able to arrive and establish in the same areas in the future. To assess behavioral dominance, we used confrontation experiments, testing the aggressiveness in individual and group interactions between all species pairs. In addition, to compare discovery efficiency, we tested the species’ capacity to locate a food resource in a maze, and the capacity to recruit nestmates to exploit a food resource. The four species differed greatly in their capacity to discover resources and to recruit nestmates and to dominate the other species. Our results are consistent with a discovery–dominance trade-off. The species that showed the highest level of interspecific aggressiveness and dominance during dyadic interactions. PMID:26257879

  2. Allocation trade-offs dominate the response of tropical forest growth to seasonal and interannual drought.

    PubMed

    Doughty, Christopher E; Malhi, Yadvinder; Araujo-Murakami, Alejandro; Metcalfe, Daniel B; Silva-Espejo, Javier E; Arroyo, Luzmila; Heredia, Juan P; Pardo-Toledo, Erwin; Mendizabal, Luz M; Rojas-Landivar, Victor D; Vega-Martinez, Meison; Flores-Valencia, Marcio; Sibler-Rivero, Rebeca; Moreno-Vare, Luzmarina; Viscarra, Laura Jessica; Chuviru-Castro, Tamara; Osinaga-Becerra, Marilin; Ledezma, Roxana

    2014-08-01

    What determines the seasonal and interannual variation of growth rates in trees in a tropical forest? We explore this question with a novel four-year high-temporal-resolution data set of carbon allocation from two forest plots in the Bolivian Amazon. The forests show strong seasonal variation in tree wood growth rates, which are largely explained by shifts in carbon allocation, and not by shifts in total productivity. At the deeper soil plot, there was a clear seasonal trade-off between wood and canopy NPP, while the shallower soils plot showed a contrasting seasonal trade-off between wood and fine roots. Although a strong 2010 drought reduced photosynthesis, NPP remained constant and increased in the six-month period following the drought, which indicates usage of significant nonstructural carbohydrate stores. Following the drought, carbon allocation increased initially towards the canopy, and then in the following year, allocation increased towards fine-root production. Had we only measured woody growth at these sites and inferred total NPP, we would have misinterpreted both the seasonal and interannual responses. In many tropical forest ecosystems, we propose that changing tree growth rates are more likely to reflect shifts in allocation rather than changes in overall productivity. Only a whole NPP allocation perspective can correctly interpret the relationship between changes in growth and changes in productivity.

  3. The Trade-Off between Female Fertility and Longevity during the Epidemiological Transition in the Netherlands

    PubMed Central

    Kaptijn, Ralf; Thomese, Fleur; Liefbroer, Aart C.; Van Poppel, Frans; Van Bodegom, David; Westendorp, Rudi G. J.

    2015-01-01

    Several hypotheses have been put forward to explain the relationship between women’s fertility and their post-reproductive longevity. In this study, we focus on the disposable soma theory, which posits that a negative relationship between women’s fertility and longevity can be understood as an evolutionary trade-off between reproduction and survival. We examine the relationship between fertility and longevity during the epidemiological transition in the Netherlands. This period of rapid decline in mortality from infectious diseases offers a good opportunity to study the relationship between fertility and longevity, using registry data from 6,359 women born in The Netherlands between 1850 and 1910. We hypothesize that an initially negative relationship between women’s fertility and their longevity gradually turns less negative during the epidemiological transition, because of decreasing costs of higher parities. An initially inversed U-shaped association between fertility and longevity changes to zero during the epidemiological transition. This does suggest a diminishing environmental pressure on fertility. However, we find no evidence of an initial linear trade-off between fertility and post-reproductive survival. PMID:26680211

  4. Fundamental rate-loss trade-off for the quantum internet

    PubMed Central

    Azuma, Koji; Mizutani, Akihiro; Lo, Hoi-Kwong

    2016-01-01

    The quantum internet holds promise for achieving quantum communication—such as quantum teleportation and quantum key distribution (QKD)—freely between any clients all over the globe, as well as for the simulation of the evolution of quantum many-body systems. The most primitive function of the quantum internet is to provide quantum entanglement or a secret key to two points efficiently, by using intermediate nodes connected by optical channels with each other. Here we derive a fundamental rate-loss trade-off for a quantum internet protocol, by generalizing the Takeoka–Guha–Wilde bound to be applicable to any network topology. This trade-off has essentially no scaling gap with the quantum communication efficiencies of protocols known to be indispensable to long-distance quantum communication, such as intercity QKD and quantum repeaters. Our result—putting a practical but general limitation on the quantum internet—enables us to grasp the potential of the future quantum internet. PMID:27886172

  5. Reproduction and lifespan: Trade-offs, overall energy budgets, intergenerational costs, and costs neglected by research.

    PubMed

    Jasienska, Grazyna

    2009-01-01

    In human females allocation of resources to support reproduction may cause their insufficient supply to other metabolic functions, resulting in compromised physiology, increased risks of diseases and, consequently, reduced lifespan. While many studies on both historical and contemporary populations show that women with high fertility indeed have shorter lifespans. This relationship is far from universal: a lack of correlation between fertility and lifespan, or even an increased lifespan of women with high fertility have also been documented. Reduced lifespan in women with high fertility may be undetectable due to methodological weaknesses of research or it may be truly absent, and its absence may be explained from biological principles. I will discuss the following reasons for a lack of the negative relationship, described in some demographic studies, between the number of children and lifespan in women: (1) Number of children is only a proxy of the total costs of reproduction and the cost of breastfeeding is often higher than the pregnancy cost but is often not taken into account. (2) Costs of reproduction can be interpreted in a meaningful way only when they are analyzed in relation to the overall energy budget of the woman. (3) Trade-offs between risks of different diseases due to reproduction yield different mortality predictions depending on the socio-economic status of the studied populations. (4) Costs of reproduction are related not only to having children but also to having grandchildren. Such intergenerational costs should be included in analysis of trade-offs between costs of reproduction and longevity.

  6. Deriving tight error-trade-off relations for approximate joint measurements of incompatible quantum observables

    NASA Astrophysics Data System (ADS)

    Branciard, Cyril

    2014-02-01

    The quantification of the "measurement uncertainty"aspect of Heisenberg's uncertainty principle—that is, the study of trade-offs between accuracy and disturbance, or between accuracies in an approximate joint measurement on two incompatible observables—has regained a lot of interest recently. Several approaches have been proposed and debated. In this paper we consider Ozawa's definitions for inaccuracies (as root-mean-square errors) in approximate joint measurements, and study how these are constrained in different cases, whether one specifies certain properties of the approximations—namely their standard deviations and/or their bias—or not. Extending our previous work [C. Branciard, Proc. Natl. Acad. Sci. USA 110, 6742 (2013), 10.1073/pnas.1219331110], we derive error-trade-off relations, which we prove to be tight for pure states. We show explicitly how all previously known relations for Ozawa's inaccuracies follow from ours. While our relations are in general not tight for mixed states, we show how these can be strengthened and how tight relations can still be obtained in that case.

  7. Ecosystem services of the Southern Ocean: trade-offs in decision-making.

    PubMed

    Grant, Susie M; Hill, Simeon L; Trathan, Philip N; Murphy, Eugene J

    2013-10-01

    Ecosystem services are the benefits that mankind obtains from natural ecosystems. Here we identify the key services provided by the Southern Ocean. These include provisioning of fishery products, nutrient cycling, climate regulation and the maintenance of biodiversity, with associated cultural and aesthetic benefits. Potential catch limits for Antarctic krill (Euphausia superba Dana) alone are equivalent to 11% of current global marine fisheries landings. We also examine the extent to which decision-making within the Antarctic Treaty System (ATS) considers trade-offs between ecosystem services, using the management of the Antarctic krill fishery as a case study. Management of this fishery considers a three-way trade-off between fisheries performance, the status of the krill stock and that of predator populations. However, there is a paucity of information on how well these components represent other ecosystem services that might be degraded as a result of fishing. There is also a lack of information on how beneficiaries value these ecosystem services. A formal ecosystem assessment would help to address these knowledge gaps. It could also help to harmonize decision-making across the ATS and promote global recognition of Southern Ocean ecosystem services by providing a standard inventory of the relevant ecosystem services and their value to beneficiaries.

  8. Examining current or future trade-offs for biodiversity conservation in north-eastern Australia.

    PubMed

    Reside, April E; VanDerWal, Jeremy; Moilanen, Atte; Graham, Erin M

    2017-01-01

    With the high rate of ecosystem change already occurring and predicted to occur in the coming decades, long-term conservation has to account not only for current biodiversity but also for the biodiversity patterns anticipated for the future. The trade-offs between prioritising future biodiversity at the expense of current priorities must be understood to guide current conservation planning, but have been largely unexplored. To fill this gap, we compared the performance of four conservation planning solutions involving 662 vertebrate species in the Wet Tropics Natural Resource Management Cluster Region in north-eastern Australia. Input species data for the four planning solutions were: 1) current distributions; 2) projected distributions for 2055; 3) projected distributions for 2085; and 4) current, 2055 and 2085 projected distributions, and the connectivity between each of the three time periods for each species. The four planning solutions were remarkably similar (up to 85% overlap), suggesting that modelling for either current or future scenarios is sufficient for conversation planning for this region, with little obvious trade-off. Our analyses also revealed that overall, species with small ranges occurring across steep elevation gradients and at higher elevations were more likely to be better represented in all solutions. Given that species with these characteristics are of high conservation significance, our results provide confidence that conservation planning focused on either current, near- or distant-future biodiversity will account for these species.

  9. There is no trade-off between speed and force in a dynamic lever system.

    PubMed

    McHenry, Matthew J

    2011-06-23

    Lever systems within a skeleton transmit force with a capacity determined by the mechanical advantage, A. A is the distance from input force to a joint, divided by the distance from the joint to the output force. A lever with a relatively high A in static equilibrium has a great capacity to generate force but moves a load over a small distance. Therefore, the geometry of a skeletal lever presents a trade-off between force and speed under quasi-static conditions. The present study considers skeletal dynamics that do not assume static equilibrium by modelling kicking by a locust leg, which is powered by stored elastic energy. This model predicts that the output force of this lever is proportional to A, but its maximum speed is independent of A. Therefore, no trade-off between force and velocity exists in a lever system with spring-mass dynamics. This demonstrates that the motion of a skeleton depends on the major forces that govern its dynamics and cannot be inferred from skeletal geometry alone.

  10. Evolutionary trade-off between vocal tract and testes dimensions in howler monkeys.

    PubMed

    Dunn, Jacob C; Halenar, Lauren B; Davies, Thomas G; Cristobal-Azkarate, Jurgi; Reby, David; Sykes, Dan; Dengg, Sabine; Fitch, W Tecumseh; Knapp, Leslie A

    2015-11-02

    Males often face a trade-off between investments in precopulatory and postcopulatory traits [1], particularly when male-male contest competition determines access to mates [2]. To date, studies of precopulatory strategies have largely focused on visual ornaments (e.g., coloration) or weapon morphology (e.g., antlers, horns, and canines). However, vocalizations can also play an important role in both male competition and female choice [3-5]. We investigated variation in vocal tract dimensions among male howler monkeys (Alouatta spp.), which produce loud roars using a highly specialized and greatly enlarged hyoid bone and larynx [6]. We examined the relative male investment in hyoids and testes among howler monkey species in relation to the level of male-male competition and analyzed the acoustic consequences of variation in hyoid morphology. Species characterized by single-male groups have large hyoids and small testes, suggesting high levels of vocally mediated competition. Larger hyoids lower formant frequencies, probably increasing the acoustic impression of male body size and playing a role analogous to investment in large body size or weaponry. Across species, as the number of males per group increases, testes volume also increases, indicating higher levels of postcopulatory sperm competition, while hyoid volume decreases. These results provide the first evidence of an evolutionary trade-off between investment in precopulatory vocal characteristics and postcopulatory sperm production.

  11. Energy efficiency trade-offs drive nucleotide usage in transcribed regions.

    PubMed

    Chen, Wei-Hua; Lu, Guanting; Bork, Peer; Hu, Songnian; Lercher, Martin J

    2016-04-21

    Efficient nutrient usage is a trait under universal selection. A substantial part of cellular resources is spent on making nucleotides. We thus expect preferential use of cheaper nucleotides especially in transcribed sequences, which are often amplified thousand-fold compared with genomic sequences. To test this hypothesis, we derive a mutation-selection-drift equilibrium model for nucleotide skews (strand-specific usage of 'A' versus 'T' and 'G' versus 'C'), which explains nucleotide skews across 1,550 prokaryotic genomes as a consequence of selection on efficient resource usage. Transcription-related selection generally favours the cheaper nucleotides 'U' and 'C' at synonymous sites. However, the information encoded in mRNA is further amplified through translation. Due to unexpected trade-offs in the codon table, cheaper nucleotides encode on average energetically more expensive amino acids. These trade-offs apply to both strand-specific nucleotide usage and GC content, causing a universal bias towards the more expensive nucleotides 'A' and 'G' at non-synonymous coding sites.

  12. Trade-off between mating opportunities and parental care: brood desertion by female Kentish plovers.

    PubMed

    Székely, T; Cuthill, I C

    2000-10-22

    Why do some parents care for their young whereas others divorce from their mate and abandon their offspring? This decision is governed by the trade-off between the value of the current breeding event and future breeding prospects. In the precocial Kentish plover Charadrius alexandrinus females frequently, but not always, abandon their broods to be cared for by their mate, and seek new breeding partners within the same season. We have shown previously that females' remating opportunities decline with date in the season, so brood desertion should be particularly favourable for early breeding females. However, the benefits are tempered by the fact that single-parent families have lower survival expectancies than those where the female remains to help the male care for the young. We therefore tested the prediction that increasing the value of the current brood (by brood-size manipulation) should increase the duration of female care early in the season, but that in late breeders, with reduced remating opportunities, desertion and thus the duration of female care should be independent of current brood size. These predictions were fulfilled, indicating that seasonally modulated trade-offs between current brood value and remating opportunities can be important in the desertion decisions of species with flexible patterns of parental care.

  13. Discovery-dominance trade-off among widespread invasive ant species.

    PubMed

    Bertelsmeier, Cleo; Avril, Amaury; Blight, Olivier; Jourdan, Hervé; Courchamp, Franck

    2015-07-01

    Ants are among the most problematic invasive species. They displace numerous native species, alter ecosystem processes, and can have negative impacts on agriculture and human health. In part, their success might stem from a departure from the discovery-dominance trade-off that can promote co-existence in native ant communities, that is, invasive ants are thought to be at the same time behaviorally dominant and faster discoverers of resources, compared to native species. However, it has not yet been tested whether similar asymmetries in behavioral dominance, exploration, and recruitment abilities also exist among invasive species. Here, we establish a dominance hierarchy among four of the most problematic invasive ants (Linepithema humile, Lasius neglectus, Wasmannia auropunctata, Pheidole megacephala) that may be able to arrive and establish in the same areas in the future. To assess behavioral dominance, we used confrontation experiments, testing the aggressiveness in individual and group interactions between all species pairs. In addition, to compare discovery efficiency, we tested the species' capacity to locate a food resource in a maze, and the capacity to recruit nestmates to exploit a food resource. The four species differed greatly in their capacity to discover resources and to recruit nestmates and to dominate the other species. Our results are consistent with a discovery-dominance trade-off. The species that showed the highest level of interspecific aggressiveness and dominance during dyadic interactions.

  14. Global assessment of nitrogen losses and trade-offs with yields from major crop cultivations.

    PubMed

    Liu, Wenfeng; Yang, Hong; Liu, Junguo; Azevedo, Ligia B; Wang, Xiuying; Xu, Zongxue; Abbaspour, Karim C; Schulin, Rainer

    2016-12-01

    Agricultural application of reactive nitrogen (N) for fertilization is a cause of massive negative environmental problems on a global scale. However, spatially explicit and crop-specific information on global N losses into the environment and knowledge of trade-offs between N losses and crop yields are largely lacking. We use a crop growth model, Python-based Environmental Policy Integrated Climate (PEPIC), to determine global N losses from three major food crops: maize, rice, and wheat. Simulated total N losses into the environment (including water and atmosphere) are 44TgNyr(-1). Two thirds of these, or 29TgNyr(-1), are losses to water alone. Rice accounts for the highest N losses, followed by wheat and maize. The N loss intensity (NLI), defined as N losses per unit of yield, is used to address trade-offs between N losses and crop yields. The NLI presents high variation among different countries, indicating diverse N losses to produce the same amount of yields. Simulations of mitigation scenarios indicate that redistributing global N inputs and improving N management could significantly abate N losses and at the same time even increase yields without any additional total N inputs.

  15. Industrial-strength ecology: trade-offs and opportunities in algal biofuel production.

    PubMed

    Shurin, Jonathan B; Abbott, Rachel L; Deal, Michael S; Kwan, Garfield T; Litchman, Elena; McBride, Robert C; Mandal, Shovon; Smith, Val H

    2013-11-01

    Microalgae represent one of the most promising groups of candidate organisms for replacing fossil fuels with contemporary primary production as a renewable source of energy. Algae can produce many times more biomass per unit area than terrestrial crop plants, easing the competing demands for land with food crops and native ecosystems. However, several aspects of algal biology present unique challenges to the industrial-scale aquaculture of photosynthetic microorganisms. These include high susceptibility to invading aquatic consumers and weeds, as well as prodigious requirements for nutrients that may compete with the fertiliser demands of other crops. Most research on algal biofuel technologies approaches these problems from a cellular or genetic perspective, attempting either to engineer or select algal strains with particular traits. However, inherent functional trade-offs may limit the capacity of genetic selection or synthetic biology to simultaneously optimise multiple functional traits for biofuel productivity and resilience. We argue that a community engineering approach that manages microalgal diversity, species composition and environmental conditions may lead to more robust and productive biofuel ecosystems. We review evidence for trade-offs, challenges and opportunities in algal biofuel cultivation with a goal of guiding research towards intensifying bioenergy production using established principles of community and ecosystem ecology.

  16. The Trade-Off between Female Fertility and Longevity during the Epidemiological Transition in the Netherlands.

    PubMed

    Kaptijn, Ralf; Thomese, Fleur; Liefbroer, Aart C; Van Poppel, Frans; Van Bodegom, David; Westendorp, Rudi G J

    2015-01-01

    Several hypotheses have been put forward to explain the relationship between women's fertility and their post-reproductive longevity. In this study, we focus on the disposable soma theory, which posits that a negative relationship between women's fertility and longevity can be understood as an evolutionary trade-off between reproduction and survival. We examine the relationship between fertility and longevity during the epidemiological transition in the Netherlands. This period of rapid decline in mortality from infectious diseases offers a good opportunity to study the relationship between fertility and longevity, using registry data from 6,359 women born in The Netherlands between 1850 and 1910. We hypothesize that an initially negative relationship between women's fertility and their longevity gradually turns less negative during the epidemiological transition, because of decreasing costs of higher parities. An initially inversed U-shaped association between fertility and longevity changes to zero during the epidemiological transition. This does suggest a diminishing environmental pressure on fertility. However, we find no evidence of an initial linear trade-off between fertility and post-reproductive survival.

  17. Fundamental rate-loss trade-off for the quantum internet.

    PubMed

    Azuma, Koji; Mizutani, Akihiro; Lo, Hoi-Kwong

    2016-11-25

    The quantum internet holds promise for achieving quantum communication-such as quantum teleportation and quantum key distribution (QKD)-freely between any clients all over the globe, as well as for the simulation of the evolution of quantum many-body systems. The most primitive function of the quantum internet is to provide quantum entanglement or a secret key to two points efficiently, by using intermediate nodes connected by optical channels with each other. Here we derive a fundamental rate-loss trade-off for a quantum internet protocol, by generalizing the Takeoka-Guha-Wilde bound to be applicable to any network topology. This trade-off has essentially no scaling gap with the quantum communication efficiencies of protocols known to be indispensable to long-distance quantum communication, such as intercity QKD and quantum repeaters. Our result-putting a practical but general limitation on the quantum internet-enables us to grasp the potential of the future quantum internet.

  18. Attention induced neural response trade-off in retinotopic cortex under load

    PubMed Central

    Torralbo, Ana; Kelley, Todd A.; Rees, Geraint; Lavie, Nilli

    2016-01-01

    The effects of perceptual load on visual cortex response to distractors are well established and various phenomena of ‘inattentional blindness’ associated with elimination of visual cortex response to unattended distractors, have been documented in tasks of high load. Here we tested an account for these effects in terms of a load-induced trade-off between target and distractor processing in retinotopic visual cortex. Participants were scanned using fMRI while performing a visual-search task and ignoring distractor checkerboards in the periphery. Retinotopic responses to target and distractors were assessed as a function of search load (comparing search set-sizes two, three and five). We found that increased load not only increased activity in frontoparietal network, but also had opposite effects on retinotopic responses to target and distractors. Target-related signals in areas V2–V3 linearly increased, while distractor response linearly decreased, with increased load. Critically, the slopes were equivalent for both load functions, thus demonstrating resource trade-off. Load effects were also found in displays with the same item number in the distractor hemisphere across different set sizes, thus ruling out local intrahemispheric interactions as the cause. Our findings provide new evidence for load theory proposals of attention resource sharing between target and distractor leading to inattentional blindness. PMID:27625311

  19. The evolution of jumping performance in Caribbean Anolis lizards: solutions to biomechanical trade-offs.

    PubMed

    Toro, Esteban; Herrel, Anthony; Irschick, Duncan

    2004-06-01

    Adaptationist theory predicts that species will evolve functional specializations for occupying different ecological niches. However, whereas performance traits are often complex, most comparative functional studies examine only simple measures of performance (e.g., sprint speed). Here we examine multiple facets of jumping biomechanics in 12 species of Caribbean Anolis lizards. These 12 species represent six ecomorphs, which are distinct ecological and morphological entities that have independently evolved on different Caribbean islands. We first show that the optimal angles for jumping maximum horizontal distances range from 39 degrees to 42 degrees, but the average jump angle of the 12 species is about 36 degrees. Interestingly, these "suboptimal" jumping angles result in only a small decrement in jump distance but substantial savings in flight duration and jump height. Further, our data show that the two key variables associated with increased jumping velocity (hindlimb length and takeoff acceleration) are independent of one another. Thus, there are two possible ways to achieve superior jumping capabilities: to evolve more muscular limbs--as stronger legs will produce more force and, hence, more acceleration--or evolve longer limbs. Our data show that anole species face trade-offs that prevent them from simultaneously optimizing different aspects of jumping ability but that they appear to have evolved behaviors that partially overcome these trade-offs.

  20. Trade-offs in experimental designs for estimating post-release mortality in containment studies

    USGS Publications Warehouse

    Rogers, Mark W.; Barbour, Andrew B; Wilson, Kyle L

    2014-01-01

    Estimates of post-release mortality (PRM) facilitate accounting for unintended deaths from fishery activities and contribute to development of fishery regulations and harvest quotas. The most popular method for estimating PRM employs containers for comparing control and treatment fish, yet guidance for experimental design of PRM studies with containers is lacking. We used simulations to evaluate trade-offs in the number of containers (replicates) employed versus the number of fish-per container when estimating tagging mortality. We also investigated effects of control fish survival and how among container variation in survival affects the ability to detect additive mortality. Simulations revealed that high experimental effort was required when: (1) additive treatment mortality was small, (2) control fish mortality was non-negligible, and (3) among container variability in control fish mortality exceeded 10% of the mean. We provided programming code to allow investigators to compare alternative designs for their individual scenarios and expose trade-offs among experimental design options. Results from our simulations and simulation code will help investigators develop efficient PRM experimental designs for precise mortality assessment.

  1. Costs and trade-offs of grazer-induced defenses in Scenedesmus under deficient resource

    NASA Astrophysics Data System (ADS)

    Zhu, Xuexia; Wang, Jun; Chen, Qinwen; Chen, Ge; Huang, Yuan; Yang, Zhou

    2016-03-01

    The green alga Scenedesmus obliquus can form inducible defensive morphs under grazing threat. Costs and trade-offs of inducible defense are expected to accompany the benefits of defensive morphs, but are hard to detect under nutrient-sufficient experimental conditions. To test the existence of costs associated with inducible defense, we cultured S. obliquus along resource availability gradients in the presence or absence of infochemical cues from Daphnia, and measured the strength of defensive colony formation and fitness characters. Under the lowest phosphorous concentration, the expression of inducible defensive colony resulted in decreased growth rate, which provides direct evidence for physiological costs. Along the gradient reduction of phosphorous concentration or light intensity, inducible defense in S. obliquus showed a decreasing trend. However, the photosynthetic efficiency of S. obliquus was barely affected by its defense responses, suggesting that the negative correlations between resource availability and colony formation of this alga may be due to resource-based trade-offs in the allocation of limited resources. Thus, our results indicated that expression of inducible defense of S. obliquus was impaired under insufficient phosphorus or light. Furthermore, under severe phosphate deficiency, obvious physiological costs of inducible defense could be detected even though defensive colony formation also decreased significantly.

  2. Sensing and communication trade-offs in picosatellite formation flying missions.

    PubMed

    Arnon, Shlomi; Kedar, Debbie

    2009-10-01

    One of the primary challenges in all small satellite design is the attainment of adequate sensing and communication capabilities within the stringent spatial limitations. These can be defined in terms of surface area expenditure for the different payloads. There is an inevitable trade-off between enhancing the sensing capacity at the expense of reducing communication capabilities on the one hand and, on the other hand, increasing the communication capacity to the detriment of the sensing ability. Careful balancing of the conflicting demands is necessary to achieve acceptable performance levels. In this paper we study two intersatellite optical wireless communication scenarios: (i) a direct link between two satellites and (ii) a folded path link between a master satellite and a picosatellite equipped with a modulatable retroreflector. In the latter case the picosatellite does not have a laser transmitter and the data carrier is the retroreflected beam from the master satellite. The data rate, which is bounded by the sensing payload resolution, is derived using diffraction theory and Shannon capacity considerations. We develop a mathematical model to describe the interrelations between sensing and communication facilities in a picosatellite flight formation using optical technologies and demonstrate system performance trade-offs with a numerical example.

  3. Foraging decisions in a capital breeder: trade-offs between mass gain and lactation.

    PubMed

    Hamel, Sandra; Côté, Steeve D

    2009-08-01

    The high energetic costs of lactation can lead to fundamental trade-offs in life-history traits, particularly in young females that reproduce before completing body growth. We assessed whether lactating female mountain goats (Oreamnos americanus) used behavioural tactics at fine spatio-temporal scales to increase energy intake to compensate for the costs of lactation. Lactating females increased bite rate and chewing rate compared with non-lactating females, but selected similar foraging sites in terms of plant quality and abundance. At peak lactation, forage intake of lactating females was >40% greater than that of non-lactating females. For females that had reached asymptotic body mass (i.e. > or =6 years old), summer mass gain of lactating females was similar to that of non-lactating females. At 4 and 5 years of age, however, daily mass gain of lactating females was about 20% lower than that of non-lactating females. We conclude that increased foraging may allow fully-grown lactating females to compensate for the energetic costs of lactation, but that there is a major trade-off between mass gain and lactation for younger females.

  4. Costs and trade-offs of grazer-induced defenses in Scenedesmus under deficient resource

    PubMed Central

    Zhu, Xuexia; Wang, Jun; Chen, Qinwen; Chen, Ge; Huang, Yuan; Yang, Zhou

    2016-01-01

    The green alga Scenedesmus obliquus can form inducible defensive morphs under grazing threat. Costs and trade-offs of inducible defense are expected to accompany the benefits of defensive morphs, but are hard to detect under nutrient-sufficient experimental conditions. To test the existence of costs associated with inducible defense, we cultured S. obliquus along resource availability gradients in the presence or absence of infochemical cues from Daphnia, and measured the strength of defensive colony formation and fitness characters. Under the lowest phosphorous concentration, the expression of inducible defensive colony resulted in decreased growth rate, which provides direct evidence for physiological costs. Along the gradient reduction of phosphorous concentration or light intensity, inducible defense in S. obliquus showed a decreasing trend. However, the photosynthetic efficiency of S. obliquus was barely affected by its defense responses, suggesting that the negative correlations between resource availability and colony formation of this alga may be due to resource-based trade-offs in the allocation of limited resources. Thus, our results indicated that expression of inducible defense of S. obliquus was impaired under insufficient phosphorus or light. Furthermore, under severe phosphate deficiency, obvious physiological costs of inducible defense could be detected even though defensive colony formation also decreased significantly. PMID:26932369

  5. Examining current or future trade-offs for biodiversity conservation in north-eastern Australia

    PubMed Central

    VanDerWal, Jeremy; Moilanen, Atte; Graham, Erin M.

    2017-01-01

    With the high rate of ecosystem change already occurring and predicted to occur in the coming decades, long-term conservation has to account not only for current biodiversity but also for the biodiversity patterns anticipated for the future. The trade-offs between prioritising future biodiversity at the expense of current priorities must be understood to guide current conservation planning, but have been largely unexplored. To fill this gap, we compared the performance of four conservation planning solutions involving 662 vertebrate species in the Wet Tropics Natural Resource Management Cluster Region in north-eastern Australia. Input species data for the four planning solutions were: 1) current distributions; 2) projected distributions for 2055; 3) projected distributions for 2085; and 4) current, 2055 and 2085 projected distributions, and the connectivity between each of the three time periods for each species. The four planning solutions were remarkably similar (up to 85% overlap), suggesting that modelling for either current or future scenarios is sufficient for conversation planning for this region, with little obvious trade-off. Our analyses also revealed that overall, species with small ranges occurring across steep elevation gradients and at higher elevations were more likely to be better represented in all solutions. Given that species with these characteristics are of high conservation significance, our results provide confidence that conservation planning focused on either current, near- or distant-future biodiversity will account for these species. PMID:28222199

  6. Trade-Offs between the Metabolic Rate and Population Density of Plants

    PubMed Central

    Deng, Jian-Ming; Li, Tao; Wang, Gen-Xuan; Liu, Jing; Yu, Ze-Long; Zhao, Chang-Ming; Ji, Ming-Fei; Zhang, Qiang; Liu, Jian-quan

    2008-01-01

    The energetic equivalence rule, which is based on a combination of metabolic theory and the self-thinning rule, is one of the fundamental laws of nature. However, there is a progressively increasing body of evidence that scaling relationships of metabolic rate vs. body mass and population density vs. body mass are variable and deviate from their respective theoretical values of 3/4 and −3/4 or −2/3. These findings questioned the previous hypotheses of energetic equivalence rule in plants. Here we examined the allometric relationships between photosynthetic mass (Mp) or leaf mass (ML) vs. body mass (β); population density vs. body mass (δ); and leaf mass vs. population density, for desert shrubs, trees, and herbaceous plants, respectively. As expected, the allometric relationships for both photosynthetic mass (i.e. metabolic rate) and population density varied with the environmental conditions. However, the ratio between the two exponents was −1 (i.e. β/δ = −1) and followed the trade-off principle when local resources were limited. Our results demonstrate for the first time that the energetic equivalence rule of plants is based on trade-offs between the variable metabolic rate and population density rather than their constant allometric exponents. PMID:18350139

  7. Trade-offs in water and carbon ecosystem services with land-use changes in grasslands.

    PubMed

    Kim, John H; Jobbágy, Esteban G; Jackson, Robert B

    2016-09-01

    Increasing pressures for food, fiber, and fuel continue to drive global land-use changes. Efforts to optimize ecosystem services under alternative land uses are often hampered by the complex interactions and trade-offs among them. We examined the effects of land-use changes on ecosystem carbon storage and groundwater recharge in grasslands of Argentina and the United States to (1) understand the relationships between both services, (2) predict their responses to vegetation shifts across environmental gradients, and (3) explore how market or policy incentives for ecosystem services could affect land-use changes. A trade-off of ecosystem services was evident in most cases, with woody encroachment increasing carbon storage (+29 Mg C/ha) but decreasing groundwater recharge (-7.3 mm/yr) and conversions to rain-fed cultivation driving opposite changes (-32 Mg C/ha vs. +13 mm/yr). In contrast, crops irrigated with ground water tended to reduce both services compared to the natural grasslands they replaced. Combining economic values of the agricultural products together with the services, we highlight potentials for relatively modest financial incentives for ecosystem services to abate land-use changes and for incentives for carbon to drive land-use decisions over those of water. Our findings also identify key opportunities and caveats for some win-win and lose-lose land-use changes for more integrative and sustainable strategies for land management.

  8. Beyond size–number trade-offs: clutch size as a maternal effect

    PubMed Central

    Brown, Gregory P.; Shine, Richard

    2009-01-01

    Traditionally, research on life-history traits has viewed the link between clutch size and offspring size as a straightforward linear trade-off; the product of these two components is taken as a measure of maternal reproductive output. Investing more per egg results in fewer but larger eggs and, hence, offspring. This simple size–number trade-off has proved attractive to modellers, but our experimental studies on keelback snakes (Tropidonophis mairii, Colubridae) reveal a more complex relationship between clutch size and offspring size. At constant water availability, the amount of water taken up by a snake egg depends upon the number of adjacent eggs. In turn, water uptake affects hatchling size, and therefore an increase in clutch size directly increases offspring size (and thus fitness under field conditions). This allometric advantage may influence the evolution of reproductive traits such as growth versus reproductive effort, optimal age at female maturation, the body-reserve threshold required to initiate reproduction and nest-site selection (e.g. communal oviposition). The published literature suggests that similar kinds of complex effects of clutch size on offspring viability are widespread in both vertebrates and invertebrates. Our results also challenge conventional experimental methodologies such as split-clutch designs for laboratory incubation studies: by separating an egg from its siblings, we may directly affect offspring size and thus viability. PMID:19324614

  9. Unified trade-off optimization for general heat devices with nonisothermal processes

    NASA Astrophysics Data System (ADS)

    Long, Rui; Liu, Wei

    2015-04-01

    An analysis of the efficiency and coefficient of performance (COP) for general heat engines and refrigerators with nonisothermal processes is conducted under the trade-off criterion. The specific heat of the working medium has significant impacts on the optimal configurations of heat devices. For cycles with constant specific heat, the bounds of the efficiency and COP are found to be the same as those obtained through the endoreversible Carnot ones. However, they are independent of the cycle time durations. For cycles with nonconstant specific heat, whose dimensionless contact time approaches infinity, the general alternative upper and lower bounds of the efficiency and COP under the trade-off criteria have been proposed under the asymmetric limits. Furthermore, when the dimensionless contact time approaches zero, the endoreversible Carnot model is recovered. In addition, the efficiency and COP bounds of different kinds of actual heat engines and refrigerators have also been analyzed. This paper may provide practical insight for designing and operating actual heat engines and refrigerators.

  10. Optimal solutions for complex design problems: Using isoperformance software for human factors trade offs

    NASA Technical Reports Server (NTRS)

    Kennedy, Robert S.; Jones, Marshall B.; Baltzley, Dennis R.

    1988-01-01

    A major application of isoperformance is as a trade-off methodology of the three major drivers of system design; equipment, training variables, and user characteristics. The flexibility of isoperformance allows each of these three components to be nearly any rational variation. For example, aptitude may be military Armed Forces Qualification Testing (AFQT) categories, cutoff scores within a selection procedure, or simply dichotomizing high and low scorers (pass/fail). Equipment may be new versus old, 'smart' versus dumb, high versus low resolution, etc. Training may be short versus long or varieties of media types (lecture versus CAI/CBI versus self-paced workbooks). In its final computerized form isoperformance lets the user set an operational level of performance (e.g., a jet pilot in a simulated emergency must take prescribed corrective action and clear the plane in several seconds, pilot astronauts will check out all shuttle flight systems within 30 minutes, or Mission Specialists must handle sucdessfully a required number of job elements). At this point the computer program guides the user through any requested trade-offs of the three components while maintaining the specified operational level of performance through isoperformance curves. A demonstration of the computer program is currently available.

  11. Trade-offs between driving nodes and time-to-control in complex networks

    PubMed Central

    Pequito, Sérgio; Preciado, Victor M.; Barabási, Albert-László; Pappas, George J.

    2017-01-01

    Recent advances in control theory provide us with efficient tools to determine the minimum number of driving (or driven) nodes to steer a complex network towards a desired state. Furthermore, we often need to do it within a given time window, so it is of practical importance to understand the trade-offs between the minimum number of driving/driven nodes and the minimum time required to reach a desired state. Therefore, we introduce the notion of actuation spectrum to capture such trade-offs, which we used to find that in many complex networks only a small fraction of driving (or driven) nodes is required to steer the network to a desired state within a relatively small time window. Furthermore, our empirical studies reveal that, even though synthetic network models are designed to present structural properties similar to those observed in real networks, their actuation spectra can be dramatically different. Thus, it supports the need to develop new synthetic network models able to replicate controllability properties of real-world networks. PMID:28054597

  12. Attention induced neural response trade-off in retinotopic cortex under load.

    PubMed

    Torralbo, Ana; Kelley, Todd A; Rees, Geraint; Lavie, Nilli

    2016-09-14

    The effects of perceptual load on visual cortex response to distractors are well established and various phenomena of 'inattentional blindness' associated with elimination of visual cortex response to unattended distractors, have been documented in tasks of high load. Here we tested an account for these effects in terms of a load-induced trade-off between target and distractor processing in retinotopic visual cortex. Participants were scanned using fMRI while performing a visual-search task and ignoring distractor checkerboards in the periphery. Retinotopic responses to target and distractors were assessed as a function of search load (comparing search set-sizes two, three and five). We found that increased load not only increased activity in frontoparietal network, but also had opposite effects on retinotopic responses to target and distractors. Target-related signals in areas V2-V3 linearly increased, while distractor response linearly decreased, with increased load. Critically, the slopes were equivalent for both load functions, thus demonstrating resource trade-off. Load effects were also found in displays with the same item number in the distractor hemisphere across different set sizes, thus ruling out local intrahemispheric interactions as the cause. Our findings provide new evidence for load theory proposals of attention resource sharing between target and distractor leading to inattentional blindness.

  13. Trade-offs between growth and maturation: the cost of reproduction for surviving environmental extremes.

    PubMed

    Luhring, Thomas M; Holdo, Ricardo M

    2015-07-01

    Life-history trade-offs and the costs of reproduction are central concepts in evolution and ecology. Episodic climatic events such as drought and extreme temperatures provide strong selective pressures that can change the balance of these costs and trade-offs. We used size-structured matrix models parameterized from field and laboratory studies to examine the effect of periodic drought on two species of aquatic salamanders (greater siren, Siren lacertina; lesser siren, Siren intermedia) that differ in size at reproduction and maximum body size. Post-drought body size distributions of the larger species (S. lacertina) are consistent with size-dependent mortality. Smaller individuals were extirpated from the population during each drought while large animals persisted, a pattern that contrasted with that seen in several ectotherms. This appears to be largely explained by estivation proficiency and a positive relationship between body size and estivation potential. Increased body size, however, may come at the cost of fecundity and maturation rate compared to a closely related congener. The cost of somatic allocation in this case may manifest itself via reduced per-capita competitive ability, which (at least in simulation studies) allows the smaller, fast-maturing species to outcompete the larger, slow-maturing species when drought is minimal or nonexistent.

  14. Trade-off between capacity and precision in visuospatial working memory.

    PubMed

    Roggeman, Chantal; Klingberg, Torkel; Feenstra, Heleen E M; Compte, Albert; Almeida, Rita

    2014-02-01

    Limitations in the performance of working memory (WM) tasks have been characterized in terms of the number of items retained (capacity) and in terms of the precision with which the information is retained. The neural mechanisms behind these limitations are still unclear. Here we used a biological constrained computational model to study the capacity and precision of visuospatial WM. The model consists of two connected networks of spiking neurons. One network is responsible for storage of information. The other provides a nonselective excitatory input to the storage network. Simulations showed that this excitation boost could temporarily increase storage capacity but also predicted that this would be associated with a decrease in precision of the memory. This prediction was subsequently tested in a behavioral (38 participants) and fMRI (22 participants) experiment. The behavioral results confirmed the trade-off effect, and the fMRI results suggest that a frontal region might be engaged in the trial-by-trial control of WM performance. The average effects were small, but individuals differed in the amount of trade-off, and these differences correlated with the frontal activation. These results support a two-module model of WM where performance is determined both by storage capacity and by top-down influence, which can vary on a trial-by-trial basis, affecting both the capacity and precision of WM.

  15. Optimizing the noise versus bias trade-off for Illumina whole genome expression BeadChips.

    PubMed

    Shi, Wei; Oshlack, Alicia; Smyth, Gordon K

    2010-12-01

    Five strategies for pre-processing intensities from Illumina expression BeadChips are assessed from the point of view of precision and bias. The strategies include a popular variance stabilizing transformation and model-based background corrections that either use or ignore the control probes. Four calibration data sets are used to evaluate precision, bias and false discovery rate (FDR). The original algorithms are shown to have operating characteristics that are not easily comparable. Some tend to minimize noise while others minimize bias. Each original algorithm is shown to have an innate intensity offset, by which unlogged intensities are bounded away from zero, and the size of this offset determines its position on the noise-bias spectrum. By adding extra offsets, a continuum of related algorithms with different noise-bias trade-offs is generated, allowing direct comparison of the performance of the strategies on equivalent terms. Adding a positive offset is shown to decrease the FDR of each original algorithm. The potential of each strategy to generate an algorithm with an optimal noise-bias trade-off is explored by finding the offset that minimizes its FDR. The use of control probes as part of the background correction and normalization strategy is shown to achieve the lowest FDR for a given bias.

  16. Evolutionary Trade-Off between Vocal Tract and Testes Dimensions in Howler Monkeys

    PubMed Central

    Dunn, Jacob C.; Halenar, Lauren B.; Davies, Thomas G.; Cristobal-Azkarate, Jurgi; Reby, David; Sykes, Dan; Dengg, Sabine; Fitch, W. Tecumseh; Knapp, Leslie A.

    2015-01-01

    Summary Males often face a trade-off between investments in precopulatory and postcopulatory traits [1], particularly when male-male contest competition determines access to mates [2]. To date, studies of precopulatory strategies have largely focused on visual ornaments (e.g., coloration) or weapon morphology (e.g., antlers, horns, and canines). However, vocalizations can also play an important role in both male competition and female choice [3, 4, 5]. We investigated variation in vocal tract dimensions among male howler monkeys (Alouatta spp.), which produce loud roars using a highly specialized and greatly enlarged hyoid bone and larynx [6]. We examined the relative male investment in hyoids and testes among howler monkey species in relation to the level of male-male competition and analyzed the acoustic consequences of variation in hyoid morphology. Species characterized by single-male groups have large hyoids and small testes, suggesting high levels of vocally mediated competition. Larger hyoids lower formant frequencies, probably increasing the acoustic impression of male body size and playing a role analogous to investment in large body size or weaponry. Across species, as the number of males per group increases, testes volume also increases, indicating higher levels of postcopulatory sperm competition, while hyoid volume decreases. These results provide the first evidence of an evolutionary trade-off between investment in precopulatory vocal characteristics and postcopulatory sperm production. PMID:26592343

  17. The role of the noradrenergic system in the exploration-exploitation trade-off: a psychopharmacological study.

    PubMed

    Jepma, Marieke; Te Beek, Erik T; Wagenmakers, Eric-Jan; van Gerven, Joop M A; Nieuwenhuis, Sander

    2010-01-01

    Animal research and computational modeling have indicated an important role for the neuromodulatory locus coeruleus-norepinephrine (LC-NE) system in the control of behavior. According to the adaptive gain theory, the LC-NE system is critical for optimizing behavioral performance by regulating the balance between exploitative and exploratory control states. However, crucial direct empirical tests of this theory in human subjects have been lacking. We used a pharmacological manipulation of the LC-NE system to test predictions of this theory in humans. In a double-blind parallel-groups design (N = 52), participants received 4 mg reboxetine (a selective norepinephrine reuptake inhibitor), 30 mg citalopram (a selective serotonin reuptake inhibitor), or placebo. The adaptive gain theory predicted that the increased tonic NE levels induced by reboxetine would promote task disengagement and exploratory behavior. We assessed the effects of reboxetine on performance in two cognitive tasks designed to examine task (dis)engagement and exploitative versus exploratory behavior: a diminishing-utility task and a gambling task with a non-stationary pay-off structure. In contrast to predictions of the adaptive gain theory, we did not find differences in task (dis)engagement or exploratory behavior between the three experimental groups, despite demonstrable effects of the two drugs on non-specific central and autonomic nervous system parameters. Our findings suggest that the LC-NE system may not be involved in the regulation of the exploration-exploitation trade-off in humans, at least not within the context of a single task. It remains to be examined whether the LC-NE system is involved in random exploration exceeding the current task context.

  18. The Role of the Noradrenergic System in the Exploration–Exploitation Trade-Off: A Psychopharmacological Study

    PubMed Central

    Jepma, Marieke; te Beek, Erik T.; Wagenmakers, Eric-Jan; van Gerven, Joop M.A.; Nieuwenhuis, Sander

    2010-01-01

    Animal research and computational modeling have indicated an important role for the neuromodulatory locus coeruleus–norepinephrine (LC–NE) system in the control of behavior. According to the adaptive gain theory, the LC–NE system is critical for optimizing behavioral performance by regulating the balance between exploitative and exploratory control states. However, crucial direct empirical tests of this theory in human subjects have been lacking. We used a pharmacological manipulation of the LC–NE system to test predictions of this theory in humans. In a double-blind parallel-groups design (N = 52), participants received 4 mg reboxetine (a selective norepinephrine reuptake inhibitor), 30 mg citalopram (a selective serotonin reuptake inhibitor), or placebo. The adaptive gain theory predicted that the increased tonic NE levels induced by reboxetine would promote task disengagement and exploratory behavior. We assessed the effects of reboxetine on performance in two cognitive tasks designed to examine task (dis)engagement and exploitative versus exploratory behavior: a diminishing-utility task and a gambling task with a non-stationary pay-off structure. In contrast to predictions of the adaptive gain theory, we did not find differences in task (dis)engagement or exploratory behavior between the three experimental groups, despite demonstrable effects of the two drugs on non-specific central and autonomic nervous system parameters. Our findings suggest that the LC–NE system may not be involved in the regulation of the exploration–exploitation trade-off in humans, at least not within the context of a single task. It remains to be examined whether the LC–NE system is involved in random exploration exceeding the current task context. PMID:21206527

  19. Burkholderia cenocepacia differential gene expression during host-pathogen interactions and adaptation to the host environment.

    PubMed

    O'Grady, Eoin P; Sokol, Pamela A

    2011-01-01

    Members of the Burkholderia cepacia complex (Bcc) are important in medical, biotechnological, and agricultural disciplines. These bacteria naturally occur in soil and water environments and have adapted to survive in association with plants and animals including humans. All Bcc species are opportunistic pathogens including Burkholderia cenocepacia that causes infections in cystic fibrosis and chronic granulomatous disease patients. The adaptation of B. cenocepacia to the host environment was assessed in a rat chronic respiratory infection model and compared to that of high cell-density in vitro grown cultures using transcriptomics. The distribution of genes differentially expressed on chromosomes 1, 2, and 3 was relatively proportional to the size of each genomic element, whereas the proportion of plasmid-encoded genes differentially expressed was much higher relative to its size and most genes were induced in vivo. The majority of genes encoding known virulence factors, components of types II and III secretion systems and chromosome 2-encoded type IV secretion system were similarly expressed between in vitro and in vivo environments. Lower expression in vivo was detected for genes encoding N-acyl-homoserine lactone synthase CepI, orphan LuxR homolog CepR2, zinc metalloproteases ZmpA and ZmpB, LysR-type transcriptional regulator ShvR, nematocidal protein AidA, and genes associated with flagellar motility, Flp type pilus formation, and type VI secretion. Plasmid-encoded type IV secretion genes were markedly induced in vivo. Additional genes induced in vivo included genes predicted to be involved in osmotic stress adaptation or intracellular survival, metal ion, and nutrient transport, as well as those encoding outer membrane proteins. Genes identified in this study are potentially important for virulence during host-pathogen interactions and may be associated with survival and adaptation to the host environment during chronic lung infections.

  20. Evolution of intrinsic growth rate: metabolic costs drive trade-offs between growth and swimming performance in Menidia menidia.

    PubMed

    Arnott, Stephen A; Chiba, Susumu; Conover, David O

    2006-06-01

    There is strong evidence that genetic capacity for growth evolves toward an optimum rather than an absolute maximum. This implies that fast growth has a cost and that trade-offs occur between growth and other life-history traits, but the fundamental mechanisms are poorly understood. Previous work on the Atlantic silverside fish Menidia menidia has demonstrated a trade-off between growth and swimming performance. We hypothesize that the trade-off derives from the competing metabolic demands associated with growth and swimming activity. We tested this by measuring standard metabolic rate (M(STD)), maximum sustainable metabolic rate (M(ACT)) and metabolic scope of laboratory-reared silversides originating from two geographically distinct populations with well-documented differences in genetic capacity for growth. The fast-growth genotype had a significantly greater M(STD) than the slow-growth genotype, but a similar MACT when swum to near exhaustion. The scope for activity of the fast-growth genotype was lower than that of the slow-growth genotype. Furthermore, the fast-growth genotype eats larger meals, thereby incurring a greater postprandial oxygen demand. We conclude that a metabolic trade-off occurs between growth and other metabolic demands and that this trade-off provides a general mechanism underlying the evolution of growth rate.

  1. Pleiotropic effects of juvenile hormone in ant queens and the escape from the reproduction–immunocompetence trade-off

    PubMed Central

    Pamminger, Tobias; Treanor, David; Hughes, William O. H.

    2016-01-01

    The ubiquitous trade-off between survival and costly reproduction is one of the most fundamental constraints governing life-history evolution. In numerous animals, gonadotropic hormones antagonistically suppressing immunocompetence cause this trade-off. The queens of many social insects defy the reproduction–survival trade-off, achieving both an extraordinarily long life and high reproductive output, but how they achieve this is unknown. Here we show experimentally, by integrating quantification of gene expression, physiology and behaviour, that the long-lived queens of the ant Lasius niger have escaped the reproduction–immunocompetence trade-off by decoupling the effects of a key endocrine regulator of fertility and immunocompetence in solitary insects, juvenile hormone (JH). This modification of the regulatory architecture enables queens to sustain a high reproductive output without elevated JH titres and suppressed immunocompetence, providing an escape from the reproduction–immunocompetence trade-off that may contribute to the extraordinary lifespan of many social insect queens. PMID:26763704

  2. Stability for function trade-offs in the enolase superfamily "catalytic module".

    PubMed

    Nagatani, Ray A; Gonzalez, Ana; Shoichet, Brian K; Brinen, Linda S; Babbitt, Patricia C

    2007-06-12

    Enzyme catalysis reflects a dynamic interplay between charged and polar active site residues that facilitate function, stabilize transition states, and maintain overall protein stability. Previous studies show that substituting neutral for charged residues in the active site often significantly stabilizes a protein, suggesting a stability trade-off for functionality. In the enolase superfamily, a set of conserved active site residues (the "catalytic module") has repeatedly been used in nature in the evolution of many different enzymes for the performance of unique overall reactions involving a chemically diverse set of substrates. This catalytic module provides a robust solution for catalysis that delivers the common underlying partial reaction that supports all of the different overall chemical reactions of the superfamily. As this module has been so broadly conserved in the evolution of new functions, we sought to investigate the extent to which it follows the stability-function trade-off. Alanine substitutions were made for individual residues, groups of residues, and the entire catalytic module of o-succinylbenzoate synthase (OSBS), a member of the enolase superfamily from Escherichia coli. Of six individual residue substitutions, four (K131A, D161A, E190A, and D213A) substantially increased protein stability (by 0.46-4.23 kcal/mol), broadly consistent with prediction of a stability-activity trade-off. The residue most conserved across the superfamily, E190, is by far the most destabilizing. When the individual substitutions were combined into groups (as they are structurally and functionally organized), nonadditive stability effects emerged, supporting previous observations that residues within the module interact as two functional groups within a larger catalytic system. Thus, whereas the multiple-mutant enzymes D161A/E190A/D213A and K131A/K133A/D161A/E190A/D213A/K235A (termed 3KDED) are stabilized relative to the wild-type enzyme (by 1.77 and 3.68 kcal

  3. Speed-difficulty trade-off in speech: Chinese versus English.

    PubMed

    Latash, Mark L; Sun, Yao; Latash, Elizaveta M; Mikaelian, Irina L

    2011-06-01

    This study continues the investigation of the previously described speed-difficulty trade-off in picture description tasks. In particular, we tested a hypothesis that the Mandarin Chinese and American English are similar in showing logarithmic dependences between speech time and index of difficulty (ID), while they differ significantly in the amount of time needed to describe simple pictures, this difference increases for more complex pictures, and it is associated with a proportional difference in the number of syllables used. Subjects (eight Chinese speakers and eight English speakers) were tested in pairs. One subject (the Speaker) described simple pictures, while the other subject (the Performer) tried to reproduce the pictures based on the verbal description as quickly as possible with a set of objects. The Chinese speakers initiated speech production significantly faster than the English speakers. Speech time scaled linearly with ln(ID) in all subjects, but the regression coefficient was significantly higher in the English speakers as compared with the Chinese speakers. The number of errors was somewhat lower in the Chinese participants (not significantly). The Chinese pairs also showed a shorter delay between the initiation of speech and initiation of action by the Performer, shorter movement time by the Performer, and shorter overall performance time. The number of syllables scaled with ID, and the Chinese speakers used significantly smaller numbers of syllables. Speech rate was comparable between the two groups, about 3 syllables/s; it dropped for more complex pictures (higher ID). When asked to reproduce the same pictures without speaking, movement time scaled linearly with ln(ID); the Chinese performers were slower than the English performers. We conclude that natural languages show a speed-difficulty trade-off similar to Fitts' law; the trade-offs in movement and speech production are likely to originate at a cognitive level. The time advantage of the

  4. Exploring trade-offs between VMAT dose quality and delivery efficiency using a network optimization approach

    NASA Astrophysics Data System (ADS)

    Salari, Ehsan; Wala, Jeremiah; Craft, David

    2012-09-01

    To formulate and solve the fluence-map merging procedure of the recently-published VMAT treatment-plan optimization method, called vmerge, as a bi-criteria optimization problem. Using an exact merging method rather than the previously-used heuristic, we are able to better characterize the trade-off between the delivery efficiency and dose quality. vmerge begins with a solution of the fluence-map optimization problem with 180 equi-spaced beams that yields the ‘ideal’ dose distribution. Neighboring fluence maps are then successively merged, meaning that they are added together and delivered as a single map. The merging process improves the delivery efficiency at the expense of deviating from the initial high-quality dose distribution. We replace the original merging heuristic by considering the merging problem as a discrete bi-criteria optimization problem with the objectives of maximizing the treatment efficiency and minimizing the deviation from the ideal dose. We formulate this using a network-flow model that represents the merging problem. Since the problem is discrete and thus non-convex, we employ a customized box algorithm to characterize the Pareto frontier. The Pareto frontier is then used as a benchmark to evaluate the performance of the standard vmerge algorithm as well as two other similar heuristics. We test the exact and heuristic merging approaches on a pancreas and a prostate cancer case. For both cases, the shape of the Pareto frontier suggests that starting from a high-quality plan, we can obtain efficient VMAT plans through merging neighboring fluence maps without substantially deviating from the initial dose distribution. The trade-off curves obtained by the various heuristics are contrasted and shown to all be equally capable of initial plan simplifications, but to deviate in quality for more drastic efficiency improvements. This work presents a network optimization approach to the merging problem. Contrasting the trade-off curves of the

  5. Trade-off in object versus spatial visualization abilities: restriction in the development of visual-processing resources.

    PubMed

    Kozhevnikov, Maria; Blazhenkova, Olesya; Becker, Michael

    2010-02-01

    Previous research indicates relative independence between the ventral and dorsal visual pathways, associated with object and spatial visual processing, respectively. The present research shows that, at the individual-differences level, there is a trade-off, rather than independence, between object and spatial visualization abilities. Across five different age groups with different professional specializations, participants with above-average object visualization abilities (artists) had below-average spatial visualization abilities, and the inverse was true for those with above-average spatial visualization abilities (scientists). No groups showed both above-average object and above-average spatial visualization abilities. Furthermore, while total object and spatial visualization resources increase with age and experience, the trade-off relationship between object and spatial visualization abilities does not. These results suggest that the trade-off originates through a bottleneck that restricts the development of overall visualization resources, rather than through preferential experience in one type of visualization.

  6. Trypanosoma cruzi: adaptation to its vectors and its hosts

    PubMed Central

    Noireau, François; Diosque, Patricio; Jansen, Ana Maria

    2009-01-01

    American trypanosomiasis is a parasitic zoonosis that occurs throughout Latin America. The etiological agent, Trypanosoma cruzi, is able to infect almost all tissues of its mammalian hosts and spreads in the environment in multifarious transmission cycles that may or not be connected. This biological plasticity, which is probably the result of the considerable heterogeneity of the taxon, exemplifies a successful adaptation of a parasite resulting in distinct outcomes of infection and a complex epidemiological pattern. In the 1990s, most endemic countries strengthened national control programs to interrupt the transmission of this parasite to humans. However, many obstacles remain to the effective control of the disease. Current knowledge of the different components involved in elaborate system that is American trypanosomiasis (the protozoan parasite T. cruzi, vectors Triatominae and the many reservoirs of infection), as well as the interactions existing within the system, is still incomplete. The Triatominae probably evolve from predatory reduvids in response to the availability of vertebrate food source. However, the basic mechanisms of adaptation of some of them to artificial ecotopes remain poorly understood. Nevertheless, these adaptations seem to be associated with a behavioral plasticity, a reduction in the genetic repertoire and increasing developmental instability. PMID:19250627

  7. Area-delay trade-offs of texture decompressors for a graphics processing unit

    NASA Astrophysics Data System (ADS)

    Novoa Súñer, Emilio; Ituero, Pablo; López-Vallejo, Marisa

    2011-05-01

    Graphics Processing Units have become a booster for the microelectronics industry. However, due to intellectual property issues, there is a serious lack of information on implementation details of the hardware architecture that is behind GPUs. For instance, the way texture is handled and decompressed in a GPU to reduce bandwidth usage has never been dealt with in depth from a hardware point of view. This work addresses a comparative study on the hardware implementation of different texture decompression algorithms for both conventional (PCs and video game consoles) and mobile platforms. Circuit synthesis is performed targeting both a reconfigurable hardware platform and a 90nm standard cell library. Area-delay trade-offs have been extensively analyzed, which allows us to compare the complexity of decompressors and thus determine suitability of algorithms for systems with limited hardware resources.

  8. Exploring trade-offs between air pollutants through an Integrated Assessment Model.

    PubMed

    Carnevale, Claudio; Finzi, Giovanna; Pederzoli, Anna; Turrini, Enrico; Volta, Marialuisa; Guariso, Giorgio; Gianfreda, Roberta; Maffeis, Giuseppe; Pisoni, Enrico; Thunis, Philippe; Markl-Hummel, Lioba; Blond, Nadège; Clappier, Alain; Dujardin, Vincent; Weber, Christiane; Perron, Gilles

    2014-05-15

    When designing air pollution reduction policies, regional decision makers face a limited budget to choose the most efficient measures which will have impacts on several pollutants in different ways. RIAT+ is a regional integrated assessment tool that supports the policy maker in this selection of the optimal emission reduction technologies, to improve air quality at minimum costs. In this paper, this tool is formalized and applied to the specific case of a French region (Alsace), to illustrate how focusing on one single pollutant may exacerbate problems related to other pollutants, on top of conflicts related to budget allocation. In our case, results are shown for possible trade-offs between NO2 and O3 control policies. The paper suggests an approach to prioritize policy maker objectives when planning air pollution policies at regional scale.

  9. Thermodynamics of accuracy in kinetic proofreading: dissipation and efficiency trade-offs

    NASA Astrophysics Data System (ADS)

    Rao, Riccardo; Peliti, Luca

    2015-06-01

    The high accuracy exhibited by biological information transcription processes is due to kinetic proofreading, i.e. by a mechanism which reduces the error rate of the information-handling process by driving it out of equilibrium. We provide a consistent thermodynamic description of enzyme-assisted assembly processes involving competing substrates, in a master equation framework. We introduce and evaluate a measure of the efficiency based on rigorous non-equilibrium inequalities. The performance of several proofreading models are thus analyzed and the related time, dissipation and efficiency versus error trade-offs exhibited for different discrimination regimes. We finally introduce and analyze in the same framework a simple model which takes into account correlations between consecutive enzyme-assisted assembly steps. This work highlights the relevance of the distinction between energetic and kinetic discrimination regimes in enzyme-substrate interactions.

  10. Time-size trade-offs in responses of cycads to male cone herbivory.

    PubMed

    Marler, Thomas E

    2010-11-01

    Plant-arthropod pollination mutualisms based on adults as pollinators and juveniles as predators of reproductive structures are understood to be successful by balancing the benefits of pollination with the antagonisms of herbivory. In a recent paper, I showed that Cycas micronesica male cone herbivory by larvae of the pollinator moth Anatrachyntis species hastened the plant's subsequent reproductive event. In this mutualism, both pollination and predation elicit distinct increases in plant fitness. The results support a resource tradeoff within an optimal-allocation model whereby cone disposal by the pollinator juveniles reduces reproductive costs. Many cycad species exhibit an annual coning season that is fixed by the environment, and in those cases the trade-off may be expressed as plasticity in cone size or cone number. Conservation plans would benefit from understanding the consequences of the lack of natural cone herbivory in ex situ germplasm management.

  11. Age Differences in Trade-off Decisions: Different Strategies but Similar Outcomes.

    PubMed

    Ma, Xiaodong; Chen, Yiwei

    2015-06-01

    The primary purpose of this study was to examine age differences in processing strategies of emotionally difficult trade-off decisions. In addition, the study tested the relevant contributions of the cognitive and emotional mechanisms to age differences in processing strategies. Altogether, 40 younger adults and 40 older adults were randomly assigned to either a high or low emotionally difficult condition of a car-purchasing decision task. MouselabWEB software was used to trace participants' processing strategies. Results showed that older adults were more likely to use attribute-based processing strategies, whereas younger adults were more likely to use alternative-based processing strategies in the high-emotion condition. In the low-emotion condition, on the other hand, both younger and older adults preferred to use alternative-based processing strategies. Furthermore, the results suggested that the cognitive measure (i.e., digit symbol coding) was not correlated with the age effects on processing strategies.

  12. Trade-Off Between Speed and Cost in Shortcuts to Adiabaticity

    NASA Astrophysics Data System (ADS)

    Campbell, Steve; Deffner, Sebastian

    2017-03-01

    Achieving effectively adiabatic dynamics is a ubiquitous goal in almost all areas of quantum physics. Here, we study the speed with which a quantum system can be driven when employing transitionless quantum driving. As a main result, we establish a rigorous link between this speed, the quantum speed limit, and the (energetic) cost of implementing such a shortcut to adiabaticity. Interestingly, this link elucidates a trade-off between speed and cost, namely, that instantaneous manipulation is impossible as it requires an infinite cost. These findings are illustrated for two experimentally relevant systems—the parametric oscillator and the Landau-Zener model—which reveal that the spectral gap governs the quantum speed limit as well as the cost for realizing the shortcut.

  13. Trading-off fish biodiversity, food security, and hydropower in the Mekong River Basin.

    PubMed

    Ziv, Guy; Baran, Eric; Nam, So; Rodríguez-Iturbe, Ignacio; Levin, Simon A

    2012-04-10

    The Mekong River Basin, site of the biggest inland fishery in the world, is undergoing massive hydropower development. Planned dams will block critical fish migration routes between the river's downstream floodplains and upstream tributaries. Here we estimate fish biomass and biodiversity losses in numerous damming scenarios using a simple ecological model of fish migration. Our framework allows detailing trade-offs between dam locations, power production, and impacts on fish resources. We find that the completion of 78 dams on tributaries, which have not previously been subject to strategic analysis, would have catastrophic impacts on fish productivity and biodiversity. Our results argue for reassessment of several dams planned, and call for a new regional agreement on tributary development of the Mekong River Basin.

  14. Optimization of a virtual EUV photoresist for the trade-off between throughput and CDU

    NASA Astrophysics Data System (ADS)

    Smith, Mark D.; Biafore, John; Fang, Chao

    2013-03-01

    EUV source power and resist photospeed will dictate the throughput of EUV lithography, and throughput is a key factor in the cost of ownership of EUVL as a technology. However, low exposure doses typically lead to poor CD uniformity (CDU) and line-width roughness (LWR). In this paper, we simulate the CDU versus dose-to-size trade-off for a large number of virtual photoresists using PROLITH for 28nm, 26nm, and 22nm HP contacts. The resulting CDU versus dose curve is very similar to the experimental investigations by Naulleau et al. (Proc. SPIE, v7972, 2011) and by Goethals et al. (EUVL Symposium 2012). With the simulated results, we can investigate trends with physical properties such as diffusivity of acid and quencher, and overall exposure yield, as well as formulation properties such as PAG and quencher loadings, and conventional versus photodecomposable quencher.

  15. Attentional trade-offs maintain the tracking of moving objects across saccades

    PubMed Central

    Carrasco, Marisa; Cavanagh, Patrick; Rolfs, Martin

    2015-01-01

    In many situations like playing sports or driving a car, we keep track of moving objects, despite the frequent eye movements that drastically interrupt their retinal motion trajectory. Here we report evidence that transsaccadic tracking relies on trade-offs of attentional resources from a tracked object's motion path to its remapped location. While participants covertly tracked a moving object, we presented pulses of coherent motion at different locations to probe the allocation of spatial attention along the object's entire motion path. Changes in the sensitivity for these pulses showed that during fixation attention shifted smoothly in anticipation of the tracked object's displacement. However, just before a saccade, attentional resources were withdrawn from the object's current motion path and reflexively drawn to the retinal location the object would have after saccade. This finding demonstrates the predictive choice the visual system makes to maintain the tracking of moving objects across saccades. PMID:25609111

  16. Aerodynamic and aerothermodynamic trade-off analysis of a small hypersonic flying test bed

    NASA Astrophysics Data System (ADS)

    Pezzella, Giuseppe

    2011-08-01

    This paper deals with the aerodynamic and aerothermodynamic trade-off analysis aiming to design a small hypersonic flying test bed with a relatively simple vehicle architecture. Such vehicle will have to be launched with a sounding rocket and shall re-enter the Earth atmosphere allowing to perform several experiments on critical re-entry technologies such as boundary-layer transition and shock-shock interaction phenomena. The flight shall be conducted at hypersonic Mach number, in the range 6-8 at moderate angles of attack. In the paper some design analyses are shown as, for example, the longitudinal and lateral-directional stability analysis. A preliminary optimization of the configuration has been also done to improve the aerodynamic performance and stability of the vehicle. Several design results, based both on engineering approach and computational fluid dynamics, are reported and discussed in the paper. The aerodynamic model of vehicle is also provided.

  17. Trade-Off between Information Format and Capacity in the Olfactory System

    PubMed Central

    Stopfer, Mark A.

    2015-01-01

    As information about the sensory environment passes between layers within the nervous system, the format of the information often changes. To examine how information format affects the capacity of neurons to represent stimuli, we measured the rate of information transmission in olfactory neurons in intact, awake locusts (Schistocerca americana) while pharmacologically manipulating patterns of correlated neuronal activity. Blocking the periodic inhibition underlying odor-elicited neural oscillatory synchronization increased information transmission rates. This suggests oscillatory synchrony, which serves other information processing roles, comes at a cost to the speed with which neurons can transmit information. Our results provide an example of a trade-off between benefits and costs in neural information processing. PMID:25632129

  18. Predicting Cost/Performance Trade-Offs for Whitney: A Commodity Computing Cluster

    NASA Technical Reports Server (NTRS)

    Becker, Jeffrey C.; Nitzberg, Bill; VanderWijngaart, Rob F.; Kutler, Paul (Technical Monitor)

    1997-01-01

    Recent advances in low-end processor and network technology have made it possible to build a "supercomputer" out of commodity components. We develop simple models of the NAS Parallel Benchmarks version 2 (NPB 2) to explore the cost/performance trade-offs involved in building a balanced parallel computer supporting a scientific workload. We develop closed form expressions detailing the number and size of messages sent by each benchmark. Coupling these with measured single processor performance, network latency, and network bandwidth, our models predict benchmark performance to within 30%. A comparison based on total system cost reveals that current commodity technology (200 MHz Pentium Pros with 100baseT Ethernet) is well balanced for the NPBs up to a total system cost of around $1,000,000.

  19. Predicting Cost/Performance Trade-offs For Whitney: A Commodity Computing Cluster

    NASA Technical Reports Server (NTRS)

    Becker, Jeffrey C.; Nitzberg, Bill; VanDerWijngaart, Rob F.; Tweten, Dave (Technical Monitor)

    1998-01-01

    Recent advances in low-end processor and network technology have made it possible to build a "supercomputer" out of commodity components. We develop simple models of the NAS Parallel Benchmarks version 2 (NPB 2) to explore the cost/performance trade-offs involved in building a balanced parallel computer supporting a scientific workload. By measuring single processor benchmark performance, network latency, and network bandwidth, and using closed form expressions detailing the number and size of messages sent by each benchmark, our models predict benchmark performance to within 30%. A comparison based on total system cost reveals that current commodity technology (200 MHz Pentium Pros with 100baseT Ethernet) is well balanced for the NPBs up to a total system cost of around $ 1,000,000.

  20. Blade design trade-offs using low-lift airfoils for stall-regulated HAWTs

    SciTech Connect

    Giguere, P.; Selig, M.S.; Tangler, J.L.

    1999-11-01

    A systematic blade design study was conducted to explore the trade-offs in using low-lift airfoils for a 750-kilowatt stall-regulated wind turbine. Tip-region airfoils having a maximum-lift coefficient ranging from 0.7--1.2 were considered in this study, with the main objective of identifying the practical lower limit for the maximum-life coefficient. Blades were optimized for both maximum annual energy production and minimum cost of energy using a method that takes into account aerodynamic and structural considerations. The results indicate that the effect of the maximum-lift coefficient on the cost of energy is small with a slight advantage to the highest maximum lift coefficient airfoils for the tip-region of the blade become more desirable as machine size increases, provided the airfoils yield acceptable stall characteristics. The conclusions are applicable to large wind turbines that use passive or active stall to regulate peak power.

  1. Cost-Efficiency Trade-off and the Design of Thermoelectric Power Generators

    SciTech Connect

    Yazawa, Kazuaki; Shakouri, Ali

    2011-07-27

    The energy conversion efficiency of today’s thermoelectric generators is significantly lower than that of conventional mechanical engines. Almost all of the existing research is focused on materials to improve the conversion efficiency. Here we propose a general framework to study the cost-efficiency trade-off for thermoelectric power generation. A key factor is the optimization of thermoelectric modules together with their heat source and heat sinks. Full electrical and thermal co-optimization yield a simple analytical expression for optimum design. Based on this model, power output per unit mass can be maximized. We show that the fractional area coverage of thermoelectric elements in a module could play a significant role in reducing the cost of power generation systems.

  2. Chunking as the result of an efficiency computation trade-off

    PubMed Central

    Ramkumar, Pavan; Acuna, Daniel E.; Berniker, Max; Grafton, Scott T.; Turner, Robert S.; Kording, Konrad P.

    2016-01-01

    How to move efficiently is an optimal control problem, whose computational complexity grows exponentially with the horizon of the planned trajectory. Breaking a compound movement into a series of chunks, each planned over a shorter horizon can thus reduce the overall computational complexity and associated costs while limiting the achievable efficiency. This trade-off suggests a cost-effective learning strategy: to learn new movements we should start with many short chunks (to limit the cost of computation). As practice reduces the impediments to more complex computation, the chunking structure should evolve to allow progressively more efficient movements (to maximize efficiency). Here we show that monkeys learning a reaching sequence over an extended period of time adopt this strategy by performing movements that can be described as locally optimal trajectories. Chunking can thus be understood as a cost-effective strategy for producing and learning efficient movements. PMID:27397420

  3. Study on RLS trade-off resist upgrade for production ready EUV lithography

    NASA Astrophysics Data System (ADS)

    Lee, Junghyung; Kim, Jieun; Jeong, Seunguk; Lim, Mijung; Koo, Sunyoung; Lim, Chang-Moon; Kim, Young-Sik

    2016-03-01

    Extreme Ultraviolet (EUV) is the most promising technology as substitute for multiple patterning based on ArF immersion lithography. If enough productivity can be accomplished, EUV will take main role in the chip manufacturing. Since the introduction of NXE3300, many significant results have been achieved in source power and availability, but lots of improvements are still required in various aspects for the implementation of EUV lithography on high volume manufacturing. Among them, it is especially important to attain high sensitivity resist without degrading other resolution performance. In this paper, performances of various resists were evaluated with real device patterns on NXE3300 scanner and technical progress of up-to-date EUV resists will be shown by comparing with the performance of their predecessors. Finally the prospect of overcoming the triangular trade-off between sensitivity, resolution, line edge roughness (LER) and achieving high volume manufacturing will be discussed.

  4. Local vs. global redundancy - trade-offs between resilience against cascading failures and frequency stability

    NASA Astrophysics Data System (ADS)

    Plietzsch, A.; Schultz, P.; Heitzig, J.; Kurths, J.

    2016-05-01

    When designing or extending electricity grids, both frequency stability and resilience against cascading failures have to be considered amongst other aspects of energy security and economics such as construction costs due to total line length. Here, we compare an improved simulation model for cascading failures with state-of-the-art simulation models for short-term grid dynamics. Random ensembles of realistic power grid topologies are generated using a recent model that allows for a tuning of global vs local redundancy. The former can be measured by the algebraic connectivity of the network, whereas the latter can be measured by the networks transitivity. We show that, while frequency stability of an electricity grid benefits from a global form of redundancy, resilience against cascading failures rather requires a more local form of redundancy and further analyse the corresponding trade-off.

  5. Trade-off between Transcriptome Plasticity and Genome Evolution in Cephalopods.

    PubMed

    Liscovitch-Brauer, Noa; Alon, Shahar; Porath, Hagit T; Elstein, Boaz; Unger, Ron; Ziv, Tamar; Admon, Arie; Levanon, Erez Y; Rosenthal, Joshua J C; Eisenberg, Eli

    2017-04-06

    RNA editing, a post-transcriptional process, allows the diversification of proteomes beyond the genomic blueprint; however it is infrequently used among animals for this purpose. Recent reports suggesting increased levels of RNA editing in squids thus raise the question of the nature and effects of these events. We here show that RNA editing is particularly common in behaviorally sophisticated coleoid cephalopods, with tens of thousands of evolutionarily conserved sites. Editing is enriched in the nervous system, affecting molecules pertinent for excitability and neuronal morphology. The genomic sequence flanking editing sites is highly conserved, suggesting that the process confers a selective advantage. Due to the large number of sites, the surrounding conservation greatly reduces the number of mutations and genomic polymorphisms in protein-coding regions. This trade-off between genome evolution and transcriptome plasticity highlights the importance of RNA recoding as a strategy for diversifying proteins, particularly those associated with neural function. PAPERCLIP.

  6. The risk-return trade-off between solitary and eusocial reproduction.

    PubMed

    Fu, Feng; Kocher, Sarah D; Nowak, Martin A

    2015-01-01

    Social insect colonies can be seen as a distinct form of biological organisation because they function as superorganisms. Understanding how natural selection acts on the emergence and maintenance of these colonies remains a major question in evolutionary biology and ecology. Here, we explore this by using multi-type branching processes to calculate the basic reproductive ratios and the extinction probabilities for solitary vs. eusocial reproductive strategies. We find that eusociality, albeit being hugely successful once established, is generally less stable than solitary reproduction unless large demographic advantages of eusociality arise for small colony sizes. We also demonstrate how such demographic constraints can be overcome by the presence of ecological niches that strongly favour eusociality. Our results characterise the risk-return trade-offs between solitary and eusocial reproduction, and help to explain why eusociality is taxonomically rare: eusociality is a high-risk, high-reward strategy, whereas solitary reproduction is more conservative.

  7. Characteristics and Trade-Offs of Doppler Lidar Global Wind Profiling

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J.; Emmitt, G David

    2004-01-01

    Accurate, global profiling of wind velocity is highly desired by NASA, NOAA, the DOD/DOC/NASA Integrated Program Office (IPO)/NPOESS, DOD, and others for many applications such as validation and improvement of climate models, and improved weather prediction. The most promising technology to deliver this measurement from space is Doppler Wind Lidar (DWL). The NASA/NOAA Global Tropospheric Wind Sounder (GTWS) program is currently in the process of generating the science requirements for a space-based sensor. In order to optimize the process of defining science requirements, it is important for the scientific and user community to understand the nature of the wind measurements that DWL can make. These measurements are very different from those made by passive imaging sensors or by active radar sensors. The purpose of this paper is to convey the sampling characteristics and data product trade-offs of an orbiting DWL.

  8. Trade-Offs in Improving Biofuel Tolerance Using Combinations of Efflux Pumps.

    PubMed

    Turner, William J; Dunlop, Mary J

    2015-10-16

    Microbes can be engineered to produce next-generation biofuels; however, the accumulation of toxic biofuels can limit yields. Previous studies have shown that efflux pumps can increase biofuel tolerance and improve production. Here, we asked whether expressing multiple pumps in combination could further increase biofuel tolerance. Pump overexpression inhibits cell growth, suggesting a trade-off between biofuel and pump toxicity. With multiple pumps, it is unclear how the fitness landscape is impacted. To address this, we measured tolerance of Escherichia coli to the biojet fuel precursor α-pinene in one-pump and two-pump strains. To support our experiments, we developed a mathematical model describing toxicity due to biofuel and overexpression of pumps. We found that data from one-pump strains can accurately predict the performance of two-pump strains. This result suggests that it may be possible to dramatically reduce the number of experiments required for characterizing the effects of combined biofuel tolerance mechanisms.

  9. Cost-efficiency trade-off and the design of thermoelectric power generators.

    PubMed

    Yazawa, Kazuaki; Shakouri, Ali

    2011-09-01

    The energy conversion efficiency of today's thermoelectric generators is significantly lower than that of conventional mechanical engines. Almost all of the existing research is focused on materials to improve the conversion efficiency. Here we propose a general framework to study the cost-efficiency trade-off for thermoelectric power generation. A key factor is the optimization of thermoelectric modules together with their heat source and heat sinks. Full electrical and thermal co-optimization yield a simple analytical expression for optimum design. Based on this model, power output per unit mass can be maximized. We show that the fractional area coverage of thermoelectric elements in a module could play a significant role in reducing the cost of power generation systems.

  10. A transmission-virulence evolutionary trade-off explains attenuation of HIV-1 in Uganda.

    PubMed

    Blanquart, François; Grabowski, Mary Kate; Herbeck, Joshua; Nalugoda, Fred; Serwadda, David; Eller, Michael A; Robb, Merlin L; Gray, Ronald; Kigozi, Godfrey; Laeyendecker, Oliver; Lythgoe, Katrina A; Nakigozi, Gertrude; Quinn, Thomas C; Reynolds, Steven J; Wawer, Maria J; Fraser, Christophe

    2016-11-05

    Evolutionary theory hypothesizes that intermediate virulence maximizes pathogen fitness as a result of a trade-off between virulence and transmission, but empirical evidence remains scarce. We bridge this gap using data from a large and long-standing HIV-1 prospective cohort, in Uganda. We use an epidemiological-evolutionary model parameterised with this data to derive evolutionary predictions based on analysis and detailed individual-based simulations. We robustly predict stabilising selection towards a low level of virulence, and rapid attenuation of the virus. Accordingly, set-point viral load, the most common measure of virulence, has declined in the last 20 years. Our model also predicts that subtype A is slowly outcompeting subtype D, with both subtypes becoming less virulent, as observed in the data. Reduction of set-point viral loads should have resulted in a 20% reduction in incidence, and a three years extension of untreated asymptomatic infection, increasing opportunities for timely treatment of infected individuals.

  11. Reversing the picture superiority effect: a speed-accuracy trade-off study of recognition memory.

    PubMed

    Boldini, Angela; Russo, Riccardo; Punia, Sahiba; Avons, S E

    2007-01-01

    Speed-accuracy trade-off methods have been used to contrast single- and dual-process accounts of recognition memory. With these procedures, subjects are presented with individual test items and required to make recognition decisions under various time constraints. In three experiments, we presented words and pictures to be intentionally learned; test stimuli were always visually presented words. At test, we manipulated the interval between the presentation of each test stimulus and that of a response signal, thus controlling the amount of time available to retrieve target information. The standard picture superiority effect was significant in long response deadline conditions (i.e., > or = 2,000 msec). Conversely, a significant reverse picture superiority effect emerged at short response-signal deadlines (< 200 msec). The results are congruent with views suggesting that both fast familiarity and slower recollection processes contribute to recognition memory. Alternative accounts are also discussed.

  12. Pollinators, pests, and predators: Recognizing ecological trade-offs in agroecosystems.

    PubMed

    Saunders, Manu E; Peisley, Rebecca K; Rader, Romina; Luck, Gary W

    2016-02-01

    Ecological interactions between crops and wild animals frequently result in increases or declines in crop yield. Yet, positive and negative interactions have mostly been treated independently, owing partly to disciplinary silos in ecological and agricultural sciences. We advocate a new integrated research paradigm that explicitly recognizes cost-benefit trade-offs among animal activities and acknowledges that these activities occur within social-ecological contexts. Support for this paradigm is presented in an evidence-based conceptual model structured around five evidence statements highlighting emerging trends applicable to sustainable agriculture. The full range of benefits and costs associated with animal activities in agroecosystems cannot be quantified by focusing on single species groups, crops, or systems. Management of productive agroecosystems should sustain cycles of ecological interactions between crops and wild animals, not isolate these cycles from the system. Advancing this paradigm will therefore require integrated studies that determine net returns of animal activity in agroecosystems.

  13. Towards climate justice: how do the most vulnerable weigh environment-economy trade-offs?

    PubMed

    Running, Katrina

    2015-03-01

    The world's poor are especially vulnerable to environmental disasters, including the adverse consequences of climate change. This creates a challenge for climate justice advocates who seek to ensure that those least responsible for causing climate change do not bear unwanted burdens of mitigation. One way to promote climate justice could be to pay particular attention to the environmental policy preferences of citizens from poorer, lower-emitting countries. This paper examines opinions on environment-economy trade-offs and willingness to make personal financial contributions to protect the environment among residents of 42 developed and developing countries using data from the 2005-2008 World Values Survey, the 2010 Climate Risk Index, and World Bank development indicators. Results reveal that individuals in developing countries are less likely to support policies to prioritize environmental protection over economic growth but are more willing to donate personal income for pro-environmental efforts compared to citizens of more developed nations.

  14. Trade-Off Between Speed and Cost in Shortcuts to Adiabaticity.

    PubMed

    Campbell, Steve; Deffner, Sebastian

    2017-03-10

    Achieving effectively adiabatic dynamics is a ubiquitous goal in almost all areas of quantum physics. Here, we study the speed with which a quantum system can be driven when employing transitionless quantum driving. As a main result, we establish a rigorous link between this speed, the quantum speed limit, and the (energetic) cost of implementing such a shortcut to adiabaticity. Interestingly, this link elucidates a trade-off between speed and cost, namely, that instantaneous manipulation is impossible as it requires an infinite cost. These findings are illustrated for two experimentally relevant systems-the parametric oscillator and the Landau-Zener model-which reveal that the spectral gap governs the quantum speed limit as well as the cost for realizing the shortcut.

  15. No evidence for an evolutionary trade-off between learning and immunity in a social insect.

    PubMed

    Alghamdi, A; Raine, N E; Rosato, E; Mallon, E B

    2009-02-23

    The immune response affects learning and memory in insects. Given this and the known fitness costs of both the immune system and learning, does an evolutionary trade-off exist between these two systems? We tested this by measuring the learning ability of 12 bumble-bee (Bombus terrestris) colonies in a free-flying paradigm. We then tested their immune response using the zone of inhibition assay. We found a positive relationship between colony learning performance and immune response, that is, fast-learning colonies also show high levels of antimicrobial activity. We conclude that there is no a priori reason to demand an evolutionary relationship between two traits that are linked physiologically.

  16. Trapped Between Two Tails: Trading Off Scientific Uncertainties via Climate Targets

    SciTech Connect

    Lemoine, Derek M.; McJeon, Haewon C.

    2013-08-20

    Climate change policies must trade off uncertainties about future warming, about the social and ecological impacts of warming, and about the cost of reducing greenhouse gas emissions. We show that laxer carbon targets produce broader distributions for climate damages, skewed towards severe outcomes. However, if potential low-carbon technologies fill overlapping niches, then more stringent carbon targets produce broader distributions for the cost of reducing emissions, skewed towards high-cost outcomes. We use the technology- rich GCAM integrated assessment model to assess the robustness of 450 ppm and 500 ppm carbon targets to each uncertain factor. The 500 ppm target provides net benefits across a broad range of futures. The 450 ppm target provides net benefits only when impacts are greater than conventionally assumed, when multiple technological breakthroughs lower the cost of abatement, or when evaluated with a low discount rate. Policy evaluations are more sensitive to uncertainty about abatement technology and impacts than to uncertainty about warming.

  17. Democracy-independence trade-off in oscillating dendrites and its implications for grid cells.

    PubMed

    Remme, Michiel W H; Lengyel, Máté; Gutkin, Boris S

    2010-05-13

    Dendritic democracy and independence have been characterized for near-instantaneous processing of synaptic inputs. However, a wide class of neuronal computations requires input integration on long timescales. As a paradigmatic example, entorhinal grid fields have been thought to be generated by the democratic summation of independent dendritic oscillations performing direction-selective path integration. We analyzed how multiple dendritic oscillators embedded in the same neuron integrate inputs separately and determine somatic membrane voltage jointly. We found that the interaction of dendritic oscillations leads to phase locking, which sets an upper limit on the timescale for independent input integration. Factors that increase this timescale also decrease the influence that the dendritic oscillations exert on somatic voltage. In entorhinal stellate cells, interdendritic coupling dominates and causes these cells to act as single oscillators. Our results suggest a fundamental trade-off between local and global processing in dendritic trees integrating ongoing signals.

  18. Trends in porous silicon biomedical devices: tuning microstructure and performance trade-offs in optical biosensors

    NASA Astrophysics Data System (ADS)

    DeLouise, Lisa A.; Miller, Ben L.

    2004-07-01

    High surface area mesoporous silicon microcavities are investigated for direct detect optical biosensor applications. Device quality is reported as a function of fabrication parameters. A dilute KOH etch process is utilized to modify the intrinsic 3D microstructure to enable enhanced pore infiltration of large biomolecules. Results suggest that the KOH etch mechanism is a two step process consisting of a fast step where high surface area nanostructures are rapidly removed. This is followed by a slower step where silicon is removed from the pore channel walls. The enzyme, Glutathione-S-Transferase (50kDa), is utilized to probe pore infiltration. Results from a solid phase immobilized enzyme assay support our conclusions on the impact the KOH etch step has on modifying the porous silicon microstructure. Preliminary findings point to trade-offs that exists between optimizing microstructure with microcavity operation mode and device sensitivity.

  19. Maternal Gestational Cortisol and Testosterone Are Associated with Trade-Offs in Offspring Sex and Number in a Free-Living Rodent (Urocitellus richardsonii)

    PubMed Central

    Ryan, Calen P.; Anderson, W. Gary; Berkvens, Charlene N.; Hare, James F.

    2014-01-01

    The adaptive manipulation of offspring sex and number has been of considerable interest to ecologists and evolutionary biologists. The physiological mechanisms that translate maternal condition and environmental cues into adaptive responses in offspring sex and number, however, remain obscure. In mammals, research into the mechanisms responsible for adaptive sex allocation has focused on two major endocrine axes: the hypothalamic pituitary adrenal (HPA) axis and glucocorticoids, and the hypothalamic pituitary gonadal (HPG) axis and sex steroids, particularly testosterone. While stress-induced activation of the HPA axis provides an intuitive model for sex ratio and litter size adjustment, plasma glucocorticoids exist in both bound and free fractions, and may be acting indirectly, for example by affecting plasma glucose levels. Furthermore, in female mammals, activation of the HPA axis stimulates the secretion of adrenal testosterone in addition to glucocorticoids (GCs). To begin to untangle these physiological mechanisms influencing offspring sex and number, we simultaneously examined fecal glucocorticoid metabolites, free and bound plasma cortisol, free testosterone, and plasma glucose concentration during both gestation and lactation in a free-living rodent (Urocitellus richardsonii). We also collected data on offspring sex and litter size from focal females and from a larger study population. Consistent with previous work in this population, we found evidence for a trade-off between offspring sex and number, as well as positive and negative correlations between glucocorticoids and sex ratio and litter size, respectively, during gestation (but not lactation). We also observed a negative relationship between testosterone and litter size during gestation (but not lactation), but no effect of glucose on either sex ratio or litter size. Our findings highlight the importance of binding proteins, cross-talk between endocrine systems, and temporal windows in the

  20. Seasonal trade-offs in cell-mediated immunosenescence in ruffs (Philomachus pugnax).

    PubMed Central

    Lozano, George A; Lank, David B

    2003-01-01

    The immune system is an energetically expensive self-maintenance complex that, given the risks of parasitism, cannot be carelessly compromised. Life-history theory posits that trade-offs between fitness components, such as self-maintenance and reproduction, vary between genders and age classes depending on their expected residual lifetime reproductive success, and seasonally as energetic requirements change. Using ruff (Philomachus pugnax), a bird with two genetically distinct male morphs, we demonstrate here a decrease in male immunocompetence during the breeding season, greater variance in immune response among males than females, immunosenescence in both sexes and male morphs, and a seasonal shift in the age range required to detect senescence. Using a phytohaemagglutinin delayed hypersensitivity assay, we assessed cell-mediated immunity (CMI) of males of typical breeding age during the breeding and nonbreeding seasons, and of a larger sample that included females and birds of a greater age range during the non-breeding period. CMI was higher for breeding-aged males in May than in November, but the increase was not related to age or male morph. In November, mean CMI did not differ between the sexes, but the variance was higher for males than for females, and there were no differences in mean or variance between the two male morphs. For both sexes and male morphs, CMI was lower for young birds than for birds of typical breeding ages, and it declined again for older birds. In males, senescence was detected in the non-breeding season only when very old birds were included. These results, generally consistent with expectations from life-history theory, indicate that the immune system can be involved in multifarious trade-offs within a yearly cycle and along an individual's lifetime, and that specific predictions about means and variances in immune response should be considered in future immunoecological research. PMID:12816660

  1. Functional trade-offs in succulent stems predict responses to climate change in columnar cacti.

    PubMed

    Williams, David G; Hultine, Kevin R; Dettman, David L

    2014-07-01

    Columnar cacti occur naturally in many habitats and environments in the Americas but are conspicuously dominant in very dry desert regions. These majestic plants are widely regarded for their cultural, economic, and ecological value and, in many ecosystems, support highly diverse communities of pollinators, seed dispersers, and frugivores. Massive amounts of water and other resources stored in the succulent photosynthetic stems of these species confer a remarkable ability to grow and reproduce during intensely hot and dry periods. Yet many columnar cacti are potentially under severe threat from environmental global changes, including climate change and loss of habitat. Stems in columnar cacti and other cylindrical-stemmed cacti are morphologically diverse; stem volume-to-surface area ratio (V:S) across these taxa varies by almost two orders of magnitude. Intrinsic functional trade-offs are examined here across a broad range of V:S in species of columnar cacti. It is proposed that variation in photosynthetic gas exchange, growth, and response to stress is highly constrained by stem V:S, establishing a mechanistic framework for understanding the sensitivity of columnar cacti to climate change and drought. Specifically, species that develop stems with low V:S, and thus have little storage capacity, are expected to express high mass specific photosynthesis and growth rates under favourable conditions compared with species with high V:S. But the trade-off of having little storage capacity is that low V:S species are likely to be less tolerant of intense or long-duration drought compared with high V:S species. The application of stable isotope measurements of cactus spines as recorders of growth, water relations, and metabolic responses to the environment across species of columnar cacti that vary in V:S is also reviewed. Taken together, our approach provides a coherent theory and required set of observations needed for predicting the responses of columnar cacti to

  2. Anti-microbial Use in Animals: How to Assess the Trade-offs

    PubMed Central

    Rushton, J

    2015-01-01

    Antimicrobials are widely used in preventive and curative medicine in animals. Benefits from curative use are clear – it allows sick animals to be healthy with a gain in human welfare. The case for preventive use of antimicrobials is less clear cut with debates on the value of antimicrobials as growth promoters in the intensive livestock industries. The possible benefits from the use of antimicrobials need to be balanced against their cost and the increased risk of emergence of resistance due to their use in animals. The study examines the importance of animals in society and how the role and management of animals is changing including the use of antimicrobials. It proposes an economic framework to assess the trade-offs of anti-microbial use and examines the current level of data collection and analysis of these trade-offs. An exploratory review identifies a number of weaknesses. Rarely are we consistent in the frameworks applied to the economic assessment anti-microbial use in animals, which may well be due to gaps in data or the prejudices of the analysts. There is a need for more careful data collection that would allow information on (i) which species and production systems antimicrobials are used in, (ii) what active substance of antimicrobials and the application method and (iii) what dosage rates. The species need to include companion animals as well as the farmed animals as it is still not known how important direct versus indirect spread of resistance to humans is. In addition, research is needed on pricing antimicrobials used in animals to ensure that prices reflect production and marketing costs, the fixed costs of anti-microbial development and the externalities of resistance emergence. Overall, much work is needed to provide greater guidance to policy, and such work should be informed by rigorous data collection and analysis systems. PMID:25903492

  3. Energy technologies evaluated against climate targets using a cost and carbon trade-off curve.

    PubMed

    Trancik, Jessika E; Cross-Call, Daniel

    2013-06-18

    Over the next few decades, severe cuts in emissions from energy will be required to meet global climate-change mitigation goals. These emission reductions imply a major shift toward low-carbon energy technologies, and the economic cost and technical feasibility of mitigation are therefore highly dependent upon the future performance of energy technologies. However, existing models do not readily translate into quantitative targets against which we can judge the dynamic performance of technologies. Here, we present a simple, new model for evaluating energy-supply technologies and their improvement trajectories against climate-change mitigation goals. We define a target for technology performance in terms of the carbon intensity of energy, consistent with emission reduction goals, and show how the target depends upon energy demand levels. Because the cost of energy determines the level of adoption, we then compare supply technologies to one another and to this target based on their position on a cost and carbon trade-off curve and how the position changes over time. Applying the model to U.S. electricity, we show that the target for carbon intensity will approach zero by midcentury for commonly cited emission reduction goals, even under a high demand-side efficiency scenario. For Chinese electricity, the carbon intensity target is relaxed and less certain because of lesser emission reductions and greater variability in energy demand projections. Examining a century-long database on changes in the cost-carbon space, we find that the magnitude of changes in cost and carbon intensity that are required to meet future performance targets is not unprecedented, providing some evidence that these targets are within engineering reach. The cost and carbon trade-off curve can be used to evaluate the dynamic performance of existing and new technologies against climate-change mitigation goals.

  4. Effects of postural task requirements on the speed-accuracy trade-off.

    PubMed

    Duarte, Marcos; Latash, Mark L

    2007-07-01

    We investigated the speed-accuracy trade-off in a task of pointing with the big toe of the right foot by a standing person that was designed to accentuate the importance of postural adjustments. This was done to test two hypotheses: (1) movement time during foot pointing will scale linearly with ID during target width changes, but the scaling will differ across movement distances; and (2) variations in movement time will be reflected in postural preparations to foot motion. Ten healthy adults stood on the force plate and were instructed to point with the big toe of the right foot at a target (with widths varying from 2 to 10 cm) placed on the floor in front of the subject at a distance varying from 10 to 100 cm. The instruction given to the subjects was typical for Fitts' paradigm: "be as fast and as accurate as possible in your pointing movement". The results have shown that movement time during foot pointing movements scaled with both target distance (D) and target width (W), but the two dependences could not be reduced to a single function of W/D, confirming the first hypothesis. With respect to the second hypothesis, we found that changes in task parameters led to proportional variations in movement speed and indices of variability of the postural adjustments prior to leg movement initiation, confirming the second hypothesis. Both groups of observations were valid over the whole range of distances despite the switch of the movement strategy in the middle of this range. We conclude that the speed-accuracy trade-off in a task with postural adjustments originates at the level of movement planning. The different dependences of movement time on D and W may be related to spontaneous postural sway (migration of the point of application of the resultant force acting on the body of the standing person). The results may have practical implications for posture and gait rehabilitation techniques that use modifications of stepping accuracy.

  5. Revisiting the Time Trade-off Hypothesis: Work, Organized Activities, and Academics during College

    PubMed Central

    Maggs, Jennifer L.

    2014-01-01

    How adolescents spend their time has long-term implications for their educational, health, and labor market outcomes, yet surprisingly little research has explored the time use of students across days and semesters. The current study used longitudinal daily diary data from a sample of college students attending a large public university in the Northeastern US (n = 726, Mage = 18.4) that was followed for 14 days within each of 7 semesters (for up to 98 diary days per student). The study had two primary aims. The first aim was to explore demographic correlates of employment time, organized activity time, and academic time. The second aim was to provide a rigorous test of the time trade-off hypothesis, which suggests that students will spend less time on academics when they spend more time on employment and extracurricular activities. The results demonstrated that time use varied by gender, parental education, and race/ethnicity. Furthermore, the results from multi-level models provided some support for the time trade-off hypothesis, although associations varied by the activity type and whether the day was a weekend. More time spent on employment was linked to less time spent on academics across days and semesters whereas organized activities were associated with less time on academics at the daily level only. The negative associations between employment and academics were most pronounced on weekdays. These results suggest that students may balance certain activities across days, whereas other activities may be in competition over longer time frames (i.e., semesters). PMID:25381597

  6. Trade-offs between seed dispersal and dormancy in an amphi-basicarpic cold desert annual

    PubMed Central

    Lu, Juan J.; Tan, Dun Y.; Baskin, Jerry M.; Baskin, Carol C.

    2013-01-01

    Background and Aims Several studies have demonstrated trade-offs between depth of seed dormancy and dispersal ability for diaspore-dimorphic species. However, relatively little is known about trade-offs between these two life history traits for a species that produces more than two diaspore morphs. The aim of this study was to investigate the relationship between seed dormancy and dispersal in Ceratocarpus arenarius, an amphi-basicarpic cold desert annual that produces a continuum of dispersal unit morphs. Methods A comparison was made of dispersal and dormancy breaking/germination responses of dispersal units from ground level (a), the middle of the plant canopy (c) and the top of the plant canopy (f). Various features of the morphology and mass of dispersal units and fruits (utricles) were measured. The role of bracteoles in diaspore dispersal by wind, settlement onto the soil surface and dormancy/germination was determined by comparing responses of intact dispersal units and fruits. Movement of dispersal units by wind and animals, seed after-ripening, germination phenology and the presence of water-soluble germination inhibitors in bracteoles were tested using standard procedures. Key Results Dispersal units a, c and f differed in morphology and mass; in the majority of cases, extremes were exhibited by a and f, with c being intermediate. Overall, relative dispersal ability was f > c > a, whereas relative intensity of dormancy was a > c > f. Bracteoles increased dispersal distance by wind, enhanced settlement of diaspores onto the soil surface and mechanically inhibited germination. Conclusions The results provide evidence for a model in which there is a continuous inverse-linear relationship between diaspore dispersal ability and depth of dormancy. Thus, dispersal unit heteromorphism of C. arenarius results in a continuum, from no dispersal ability/high dormancy (dispersal unit a) to high dispersal ability/low dormancy (unit f), which may be a bet

  7. Evolution of resistance and tolerance to herbivores: testing the trade-off hypothesis

    PubMed Central

    Kariñho-Betancourt, Eunice

    2015-01-01

    Background. To cope with their natural enemies, plants rely on resistance and tolerance as defensive strategies. Evolution of these strategies among natural population can be constrained by the absence of genetic variation or because of the antagonistic genetic correlation (trade-off) between them. Also, since plant defenses are integrated by several traits, it has been suggested that trade-offs might occur between specific defense traits. Methodology/Principal Findings. We experimentally assessed (1) the presence of genetic variance in tolerance, total resistance, and leaf trichome density as specific defense trait, (2) the extent of natural selection acting on plant defenses, and (3) the relationship between total resistance and leaf trichome density with tolerance to herbivory in the annual herb Datura stramonium. Full-sib families of D. stramonium were either exposed to natural herbivores (control) or protected from them by a systemic insecticide. We detected genetic variance for leaf trichome density, and directional selection acting on this character. However, we did not detect a negative significant correlation between tolerance and total resistance, or between tolerance and leaf trichome density. We argue that low levels of leaf damage by herbivores precluded the detection of a negative genetic correlation between plant defense strategies. Conclusions/Significance. This study provides empirical evidence of the independent evolution of plant defense strategies, and a defensive role of leaf trichomes. The pattern of selection should favor individuals with high trichomes density. Also, because leaf trichome density reduces damage by herbivores and possess genetic variance in the studied population, its evolution is not constrained. PMID:25780756

  8. Transcriptomic Signatures Mirror the Lack of the Fecundity/Longevity Trade-Off in Ant Queens

    PubMed Central

    von Wyschetzki, Katharina; Rueppell, Olav; Oettler, Jan; Heinze, Jürgen

    2015-01-01

    Life-history theory predicts a trade-off between reproductive investment and self-maintenance. The negative association between fertility and longevity found throughout multicellular organisms supports this prediction. As an important exception, the reproductives of many eusocial insects (ants, bees, and termites) are simultaneously very long-lived and highly fertile. Here, we examine the proximate basis for this exceptional relationship by comparing whole-body transcriptomes of differently aged queens of the ant Cardiocondyla obscurior. We show that the sets of genes differentially expressed with age significantly overlap with age-related expression changes previously found in female Drosophila melanogaster. We identified several developmental processes, such as the generation of neurons, as common signatures of aging. More generally, however, gene expression in ant queens and flies changes with age mainly in opposite directions. In contrast to flies, reproduction-associated genes were upregulated and genes associated with metabolic processes and muscle contraction were downregulated in old relative to young ant queens. Furthermore, we searched for putative C. obscurior longevity candidates associated with the previously reported lifespan-prolonging effect of mating by comparing the transcriptomes of queens that differed in mating and reproductive status. We found 21 genes, including the putative aging candidate NLaz (an insect homolog of APOD), which were consistently more highly expressed in short-lived, unmated queens than in long-lived, mated queens. Our study provides clear evidence that the alternative regulation of conserved molecular pathways that mediate the interplay among mating, egg laying, and aging underlies the lack of the fecundity/longevity trade-off in ant queens. PMID:26341296

  9. Trade-off between inverse lithography mask complexity and lithographic performance

    NASA Astrophysics Data System (ADS)

    Kim, Byung-Gook; Suh, Sung Soo; Kim, Byung-Sung; Woo, Sang-Gyun; Cho, Han-Ku; Tolani, Vikram; Dai, Grace; Irby, Dave; Wang, Kechang; Xiao, Guangming; Kim, David; Baik, Ki-Ho; Gleason, Bob

    2009-04-01

    Improvements in resolution of exposure systems have not kept pace with increasing density of semiconductor products. In order to keep shrinking circuits using equipment with the same basic resolution, lithographers have turned to options such as double-patterning, and have moved beyond model-based OPC in the search for optimal mask patterns. Inverse Lithography Technology (ILT) is becoming one of the strong candidates in 32nm & below single patterning, low-k1 lithography regime. It enables computation of optimum mask patterns to minimize deviations of images from their targets not only at nominal but also over a range of process variations, such as dose, defocus, and mask CD errors. When optimizing for a factor, such as process window, more complex mask patterns are often necessary to achieve the desired depth of focus. Complex mask patterns require more shots when written with VSB systems, increasing the component of mask cost associated with writing time. It can also be more difficult to inspect or repair certain types of complex patterns. Inspection and repair may take more time, or require more expensive equipment compared to the case with simpler masks. For these reasons, we desire to determine the simplest mask patterns that meet necessary lithographic manufacturing objectives. Luminescent ILT provides means to constrain complexity of mask solutions, each of which is optimized to meet lithographic objectives within the bounds of the constraints. Results presented here show trade-offs to process window performance with varying degrees of mask complexity. The paper details ILT mask simplification schemes on contact arrays and random logic, comparing process window trade-offs in each case. Ultimately this method enables litho and mask engineers balance lithographic requirements with mask manufacturing complexity and related cost.

  10. Trade-offs and Opportunities in the Nexus of Energy and Water-for-Food

    NASA Astrophysics Data System (ADS)

    Rosegrant, M. W.

    2015-12-01

    The world economy is under pressure for greater, more efficient and more sustainable use of natural resources to meet complementary and competing objectives in the energy, water, and food sectors. Increasing national, regional, and seasonal water scarcities in much of the world pose severe challenges for national governments, the international development community, and ultimately, for individual water users. This presentation assesses the nexus between energy and water, with an emphasis on the interactions and trade-offs between energy and water for food production. It examines the impact of biofuel production on water quantity and quality, and the potential for hydropower potential to meet energy challenges while expanding irrigation water supplies and food production potential, thereby enhancing global food security. Biofuel production affects both water quantity and quality. Expanding production of biofuels—through either crop-based production systems or direct biomass production—can significantly increase demand for water as more acreage is planted or the crop mix begins to favor thirstier crops; water demand for bio-refineries creates additional competition with agricultural water use. Water quality can also be adversely affected by increased acreage for fertilizer-intensive crops, such as maize or sugarcane, which can result in increased nitrate run-off and soil erosion. Hydropower has become a relatively forgotten part of the energy-water security picture that deserves renewed attention. Unlike biofuels, hydropower does not normally compete with agricultural water. Instead, development of hydropower could complement food production by developing dam structures and power that also provide irrigation water and support its distribution for growing food crops. But balanced hydropower policies require consideration of potential trade-offs with environmental and social impacts.

  11. Trade-offs in the evolution of bumblebee colony and body size: a comparative analysis.

    PubMed

    Cueva Del Castillo, Raúl; Sanabria-Urbán, Salomón; Serrano-Meneses, Martín Alejandro

    2015-09-01

    Trade-offs between life-history traits - such as fecundity and survival - have been demonstrated in several studies. In eusocial insects, the number of organisms and their body sizes can affect the fitness of the colony. Large-than-average body sizes as well as more individuals can improve a colony's thermoregulation, foraging efficiency, and fecundity. However, in bumblebees, large colonies and large body sizes depend largely on high temperatures and a large amount of food resources. Bumblebee taxa can be found in temperate and tropical regions of the world and differ markedly in their colony sizes and body sizes. Variation in colony size and body size may be explained by the costs and benefits associated with the evolutionary history of each species in a particular environment. In this study, we explored the effect of temperature and precipitation (the latter was used as an indirect indicator of food availability) on the colony and body size of twenty-one bumblebee taxa. A comparative analysis controlling for phylogenetic effects as well as for the body size of queens, workers, and males in bumblebee taxa from temperate and tropical regions indicated that both temperature and precipitation affect colony and body size. We found a negative association between colony size and the rainiest trimester, and a positive association between the colony size and the warmest month of the year. In addition, male bumblebees tend to evolve larger body sizes in places where the rain occurs mostly in the summer and the overall temperature is warmer. Moreover, we found a negative relationship between colony size and body sizes of queens, workers, and males, suggesting potential trade-offs in the evolution of bumblebee colony and body size.

  12. The interaction of nifedipine with selected cyclodextrins and the subsequent solubility-permeability trade-off.

    PubMed

    Beig, Avital; Miller, Jonathan M; Dahan, Arik

    2013-11-01

    The purpose of this study was to investigate the interaction of 2-hydroxypropyl-β-cyclodextrin (HPβCD) and 2,6-dimethyl-β-cyclodextrin (DMβCD) with the lipophilic drug nifedipine and to investigate the subsequent solubility-permeability interplay. Solubility curves of nifedipine with HPβCD and DMβCD in MES buffer were evaluated using phase solubility methods. Then, the apparent permeability of nifedipine was investigated as a function of increasing HPβCD/DMβCD concentration in the hexadecane-based PAMPA model. The interaction with nifedipine was CD dependent; significantly higher stability constant was obtained for DMβCD in comparison with HPβCD. Moreover, nifedipine displays different type of interaction with these CDs; a 1:1 stoichiometric inclusion complex was apparent with HPβCD, while 1:2 stoichiometry was apparent for DMβCD. In all cases, decreased apparent intestinal permeability of nifedipine as a function of increasing CD level and nifedipine apparent solubility was obtained. A quasi-equilibrium mass transport analysis was developed to explain this solubility-permeability interplay; the model enabled excellent quantitative prediction of nifedipine's permeability as a function of CD concentrations. This work demonstrates that when using CDs in solubility-enabling formulations, a trade-off exists between solubility increase and permeability decrease that must not be overlooked. This trade-off was found to be independent of the type of CD-drug interaction. The transport model presented here can aid in striking the appropriate solubility-permeability balance in order to achieve optimal overall absorption.

  13. Anti-microbial Use in Animals: How to Assess the Trade-offs.

    PubMed

    Rushton, J

    2015-04-01

    Antimicrobials are widely used in preventive and curative medicine in animals. Benefits from curative use are clear - it allows sick animals to be healthy with a gain in human welfare. The case for preventive use of antimicrobials is less clear cut with debates on the value of antimicrobials as growth promoters in the intensive livestock industries. The possible benefits from the use of antimicrobials need to be balanced against their cost and the increased risk of emergence of resistance due to their use in animals. The study examines the importance of animals in society and how the role and management of animals is changing including the use of antimicrobials. It proposes an economic framework to assess the trade-offs of anti-microbial use and examines the current level of data collection and analysis of these trade-offs. An exploratory review identifies a number of weaknesses. Rarely are we consistent in the frameworks applied to the economic assessment anti-microbial use in animals, which may well be due to gaps in data or the prejudices of the analysts. There is a need for more careful data collection that would allow information on (i) which species and production systems antimicrobials are used in, (ii) what active substance of antimicrobials and the application method and (iii) what dosage rates. The species need to include companion animals as well as the farmed animals as it is still not known how important direct versus indirect spread of resistance to humans is. In addition, research is needed on pricing antimicrobials used in animals to ensure that prices reflect production and marketing costs, the fixed costs of anti-microbial development and the externalities of resistance emergence. Overall, much work is needed to provide greater guidance to policy, and such work should be informed by rigorous data collection and analysis systems.

  14. Trade-off between multiple constraints enables simultaneous formation of modules and hubs in neural systems.

    PubMed

    Chen, Yuhan; Wang, Shengjun; Hilgetag, Claus C; Zhou, Changsong

    2013-01-01

    The formation of the complex network architecture of neural systems is subject to multiple structural and functional constraints. Two obvious but apparently contradictory constraints are low wiring cost and high processing efficiency, characterized by short overall wiring length and a small average number of processing steps, respectively. Growing evidence shows that neural networks are results from a trade-off between physical cost and functional value of the topology. However, the relationship between these competing constraints and complex topology is not well understood quantitatively. We explored this relationship systematically by reconstructing two known neural networks, Macaque cortical connectivity and C. elegans neuronal connections, from combinatory optimization of wiring cost and processing efficiency constraints, using a control parameter α, and comparing the reconstructed networks to the real networks. We found that in both neural systems, the reconstructed networks derived from the two constraints can reveal some important relations between the spatial layout of nodes and the topological connectivity, and match several properties of the real networks. The reconstructed and real networks had a similar modular organization in a broad range of α, resulting from spatial clustering of network nodes. Hubs emerged due to the competition of the two constraints, and their positions were close to, and partly coincided, with the real hubs in a range of α values. The degree of nodes was correlated with the density of nodes in their spatial neighborhood in both reconstructed and real networks. Generally, the rebuilt network matched a significant portion of real links, especially short-distant ones. These findings provide clear evidence to support the hypothesis of trade-off between multiple constraints on brain networks. The two constraints of wiring cost and processing efficiency, however, cannot explain all salient features in the real networks. The

  15. Angular versus spatial resolution trade-offs for diffusion imaging under time constraints.

    PubMed

    Zhan, Liang; Jahanshad, Neda; Ennis, Daniel B; Jin, Yan; Bernstein, Matthew A; Borowski, Bret J; Jack, Clifford R; Toga, Arthur W; Leow, Alex D; Thompson, Paul M

    2013-10-01

    Diffusion weighted magnetic resonance imaging (DW-MRI) are now widely used to assess brain integrity in clinical populations. The growing interest in mapping brain connectivity has made it vital to consider what scanning parameters affect the accuracy, stability, and signal-to-noise of diffusion measures. Trade-offs between scan parameters can only be optimized if their effects on various commonly-derived measures are better understood. To explore angular versus spatial resolution trade-offs in standard tensor-derived measures, and in measures that use the full angular information in diffusion signal, we scanned eight subjects twice, 2 weeks apart, using three protocols that took the same amount of time (7 min). Scans with 3.0, 2.7, 2.5 mm isotropic voxels were collected using 48, 41, and 37 diffusion-sensitized gradients to equalize scan times. A specially designed DTI phantom was also scanned with the same protocols, and different b-values. We assessed how several diffusion measures including fractional anisotropy (FA), mean diffusivity (MD), and the full 3D orientation distribution function (ODF) depended on the spatial/angular resolution and the SNR. We also created maps of stability over time in the FA, MD, ODF, skeleton FA of 14 TBSS-derived ROIs, and an information uncertainty index derived from the tensor distribution function, which models the signal using a continuous mixture of tensors. In scans of the same duration, higher angular resolution and larger voxels boosted SNR and improved stability over time. The increased partial voluming in large voxels also led to bias in estimating FA, but this was partially addressed by using "beyond-tensor" models of diffusion.

  16. Revisiting the Time Trade-Off Hypothesis: Work, Organized Activities, and Academics During College.

    PubMed

    Greene, Kaylin M; Maggs, Jennifer L

    2015-08-01

    How adolescents spend their time has long-term implications for their educational, health, and labor market outcomes, yet surprisingly little research has explored the time use of students across days and semesters. The current study used longitudinal daily diary data from a sample of college students attending a large public university in the Northeastern US (n = 726, M age = 18.4) that was followed for 14 days within each of seven semesters (for up to 98 diary days per student). The study had two primary aims. The first aim was to explore demographic correlates of employment time, organized activity time, and academic time. The second aim was to provide a rigorous test of the time trade-off hypothesis, which suggests that students will spend less time on academics when they spend more time on employment and extracurricular activities. The results demonstrated that time use varied by gender, parental education, and race/ethnicity. Furthermore, the results from multi-level models provided some support for the time trade-off hypothesis, although associations varied by the activity type and whether the day was a weekend. More time spent on employment was linked to less time spent on academics across days and semesters whereas organized activities were associated with less time on academics at the daily level only. The negative associations between employment and academics were most pronounced on weekdays. These results suggest that students may balance certain activities across days, whereas other activities may be in competition over longer time frames (i.e., semesters).

  17. Maintenance of brucellosis in Yellowstone bison: linking seasonal food resources, host–pathogen interaction, and life-history trade-offs

    PubMed Central

    Treanor, John J; Geremia, Chris; Ballou, Michael A; Keisler, Duane H; White, Patrick J; Cox, John J; Crowley, Philip H

    2015-01-01

    The seasonal availability of food resources is an important factor shaping the life-history strategies of organisms. During times of nutritional restriction, physiological trade-offs can induce periods of immune suppression, thereby increasing susceptibility to infectious disease. Our goal was to provide a conceptual framework describing how the endemic level bovine brucellosis (Brucella abortus) may be maintained in Yellowstone bison based on the seasonality of food resources and the life-history strategies of the host and pathogen. Our analysis was based on active B. abortus infection (measured via bacterial culture), nutritional indicators (measured as metabolites and hormones in plasma), and carcass measurements of 402 slaughtered bison. Data from Yellowstone bison were used to investigate (1) whether seasonal changes in diet quality affect nutritional condition and coincide with the reproductive needs of female bison; (2) whether active B. abortus infection and infection intensities vary with host nutrition and nutritional condition; and (3) the evidence for seasonal changes in immune responses, which may offer protection against B. abortus, in relation to nutritional condition. Female bison experienced a decline in nutritional condition during winter as reproductive demands of late gestation increased while forage quality and availability declined. Active B. abortus infection was negatively associated with bison age and nutritional condition, with the intensity of infection negatively associated with indicators of nutrition (e.g., dietary protein and energy) and body weight. Data suggest that protective cell-mediated immune responses may be reduced during the B. abortus transmission period, which coincides with nutritional insufficiencies and elevated reproductive demands during spring. Our results illustrate how seasonal food restriction can drive physiological trade-offs that suppress immune function and create infection and transmission opportunities

  18. Heat acclimation and exercise training interact when combined in an overriding and trade-off manner: physiologic-genomic linkage.

    PubMed

    Kodesh, Einat; Nesher, Nir; Simaan, Assi; Hochner, Benny; Beeri, Ronen; Gilon, Dan; Stern, Michael D; Gerstenblith, Gary; Horowitz, Michal

    2011-12-01

    Combined heat acclimation (AC) and exercise training (EX) enhance exercise performance in the heat while meeting thermoregulatory demands. We tested the hypothesis that different stress-specific adaptations evoked by each stressor individually trigger similar cardiac alterations, but when combined, overriding/trade-off interactions take place. We used echocardiography, isolated cardiomyocyte imaging and cDNA microarray techniques to assay in situ cardiac performance, excitation-contraction (EC) coupling features, and transcriptional programs associated with cardiac contractility. Rat groups studied were controls (sedentary 24°C); AC (sedentary, 34°C, 1 mo); normothermic EX (treadmill at 24°C, 1 mo); and heat-acclimated, exercise-trained (EXAC; treadmill at 34°C, 1 mo). Prolonged heat exposure decreased heart rate and contractile velocity and increased end ventricular diastolic diameter. Compared with controls, AC/EXAC cardiomyocytes demonstrated lower l-type Ca(2+) current (I(CaL)) amplitude, higher Ca(2+) transient (Ca(2+)T), and a greater Ca(2+)T-to-I(CaL) ratio; EX alone enhanced I(CaL) and Ca(2+)T, whereas aerobic training in general induced cardiac hypertrophy and action potential elongation in EX/EXAC animals. At the genomic level, the transcriptome profile indicated that the interaction between AC and EX yields an EXAC-specific molecular program. Genes affected by chronic heat were linked with the EC coupling cascade, whereas aerobic training upregulated genes involved with Ca(2+) turnover via an adrenergic/metabolic-driven positive inotropic response. In the EXAC cardiac phenotype, the impact of chronic heat overrides that of EX on EC coupling components and heart rate, whereas EX regulates cardiac morphometry. We suggest that concerted adjustments induced by AC and EX lead to enhanced metabolic and mechanical performance of the EXAC heart.

  19. Functional Trait Trade-Offs for the Tropical Montane Rain Forest Species Responding to Light from Simulating Experiments

    PubMed Central

    Mao, Peili; Zang, Runguo; Shao, Hongbo; Yu, Junbao

    2014-01-01

    Differences among tropical tree species in survival and growth to light play a key role in plant competition and community composition. Two canopy species with contrasting functional traits dominating early and late successional stages, respectively, in a tropical montane rain forest of Hainan Island, China, were selected in a pot experiment under 4 levels of light intensity (full, 50%, 30%, and 10%) in order to explore the adaptive strategies of tropical trees to light conditions. Under each light intensity level, the pioneer species, Endospermum chinense (Euphorbiaceae), had higher relative growth rate (RGR), stem mass ratio (SMR), specific leaf area (SLA), and morphological plasticity while the shade tolerant climax species, Parakmeria lotungensis (Magnoliaceae), had higher root mass ratio (RMR) and leaf mass ratio (LMR). RGR of both species was positively related to SMR and SLA under each light level but was negatively correlated with RMR under lower light (30% and 10% full light). The climax species increased its survival by a conservative resource use strategy through increasing leaf defense and root biomass investment at the expense of growth rate in low light. In contrast, the pioneer increased its growth by an exploitative resource use strategy through increasing leaf photosynthetic capacity and stem biomass investment at the expense of survival under low light. There was a trade-off between growth and survival for species under different light conditions. Our study suggests that tree species in the tropical rainforest adopt different strategies in stands of different successional stages. Species in the earlier successional stages have functional traits more advantageous to grow faster in the high light conditions, whereas species in the late successional stages have traits more favorable to survive in the low light conditions. PMID:25019095

  20. Heat acclimation and exercise training interact when combined in an overriding and trade-off manner: physiologic-genomic linkage

    PubMed Central

    Kodesh, Einat; Nesher, Nir; Simaan, Assi; Hochner, Benny; Beeri, Ronen; Gilon, Dan; Stern, Michael D.; Gerstenblith, Gary

    2011-01-01

    Combined heat acclimation (AC) and exercise training (EX) enhance exercise performance in the heat while meeting thermoregulatory demands. We tested the hypothesis that different stress-specific adaptations evoked by each stressor individually trigger similar cardiac alterations, but when combined, overriding/trade-off interactions take place. We used echocardiography, isolated cardiomyocyte imaging and cDNA microarray techniques to assay in situ cardiac performance, excitation-contraction (EC) coupling features, and transcriptional programs associated with cardiac contractility. Rat groups studied were controls (sedentary 24°C); AC (sedentary, 34°C, 1 mo); normothermic EX (treadmill at 24°C, 1 mo); and heat-acclimated, exercise-trained (EXAC; treadmill at 34°C, 1 mo). Prolonged heat exposure decreased heart rate and contractile velocity and increased end ventricular diastolic diameter. Compared with controls, AC/EXAC cardiomyocytes demonstrated lower l-type Ca2+ current (ICaL) amplitude, higher Ca2+ transient (Ca2+T), and a greater Ca2+T-to-ICaL ratio; EX alone enhanced ICaL and Ca2+T, whereas aerobic training in general induced cardiac hypertrophy and action potential elongation in EX/EXAC animals. At the genomic level, the transcriptome profile indicated that the interaction between AC and EX yields an EXAC-specific molecular program. Genes affected by chronic heat were linked with the EC coupling cascade, whereas aerobic training upregulated genes involved with Ca2+ turnover via an adrenergic/metabolic-driven positive inotropic response. In the EXAC cardiac phenotype, the impact of chronic heat overrides that of EX on EC coupling components and heart rate, whereas EX regulates cardiac morphometry. We suggest that concerted adjustments induced by AC and EX lead to enhanced metabolic and mechanical performance of the EXAC heart. PMID:21957158

  1. Azadirachtin-induced hormesis mediating shift in fecundity-longevity trade-off in the Mexican bean weevil (Chrysomelidae: Bruchinae).

    PubMed

    Mallqui, K S Vilca; Vieira, J L; Guedes, R N C; Gontijo, L M

    2014-04-01

    Insecticides can have lethal or sublethal effects upon targeted pest species, and sublethal effects may even favor pest outbreaks if insecticide-induced hormesis occurs. Hormesis is a biphasic dose-response of a given chemical compound that is stimulatory at low doses and toxic at high doses. The former response may result from the disruption of animal homeostasis leading to trade-off shifts between basic ecophysiological processes. A growing interest in the use of biorational insecticides, such as azadirachtin to control stored-product pests, raises concerns about potential sublethal effects. In this study, we explored the hypothesis that azadirachtin can negatively impact the reproductive capacity of the Mexican bean weevil, Zabrotes subfasciatus (Boheman) (Chrysomelidae: Bruchinae), a key pest of stored beans. In addition, we investigated whether adults of this species could compensate for any sublethal effect that might have affected any of their reproductive parameters by adjusting the allocation of its reproductive efforts. The results showed that females of Z. subfasciatus increased fecundity daily to compensate for azadirachtin-induced decreased longevity. In addition, a stage-structured matrix study revealed that populations of Z. subfasciatus engendered from females exposed to azadirachtin exhibited a higher rate of population increase (r) and a higher net reproductive rate (R(o)). Finally, a projection matrix analysis showed notably higher densities along the generations for azadirachtin-exposed Z. subfasciatus populations. Thus, our study provides empirical evidence for the capacity of Z. subfasciatus to adapt to sublethal effects caused by biorational insecticides; consequently, this study highlights the importance of understanding this phenomenon when devising pest management strategies.

  2. Bartonella species and their ectoparasites: selective host adaptation or strain selection between the vector and the mammalian host?

    PubMed

    Tsai, Yi-Lun; Chang, Chao-Chin; Chuang, Shih-Te; Chomel, Bruno B

    2011-07-01

    A wide range of blood-sucking arthropods have either been confirmed or are suspected as important vectors in Bartonella transmission to mammals, including humans. Overall, it appears that the diversity of Bartonella species DNA identified in ectoparasites is much broader than the species detected in their mammalian hosts, suggesting a mechanism of adaptation of Bartonella species to their host-vector ecosystem. However, these mechanisms leading to the fitness between the vectors and their hosts still need to be investigated.

  3. Trade-Offs between Growth Rate, Tree Size and Lifespan of Mountain Pine (Pinus montana) in the Swiss National Park.

    PubMed

    Bigler, Christof

    2016-01-01

    A within-species trade-off between growth rates and lifespan has been observed across different taxa of trees, however, there is some uncertainty whether this trade-off also applies to shade-intolerant tree species. The main objective of this study was to investigate the relationships between radial growth, tree size and lifespan of shade-intolerant mountain pines. For 200 dead standing mountain pines (Pinus montana) located along gradients of aspect, slope steepness and elevation in the Swiss National Park, radial annual growth rates and lifespan were reconstructed. While early growth (i.e. mean tree-ring width over the first 50 years) correlated positively with diameter at the time of tree death, a negative correlation resulted with lifespan, i.e. rapidly growing mountain pines face a trade-off between reaching a large diameter at the cost of early tree death. Slowly growing mountain pines may reach a large diameter and a long lifespan, but risk to die young at a small size. Early growth was not correlated with temperature or precipitation over the growing period. Variability in lifespan was further contingent on aspect, slope steepness and elevation. The shade-intolerant mountain pines follow diverging growth trajectories that are imposed by extrinsic environmental influences. The resulting trade-offs between growth rate, tree size and lifespan advance our understanding of tree population dynamics, which may ultimately improve projections of forest dynamics under changing environmental conditions.

  4. Trade-Offs between Growth Rate, Tree Size and Lifespan of Mountain Pine (Pinus montana) in the Swiss National Park

    PubMed Central

    Bigler, Christof

    2016-01-01

    A within-species trade-off between growth rates and lifespan has been observed across different taxa of trees, however, there is some uncertainty whether this trade-off also applies to shade-intolerant tree species. The main objective of this study was to investigate the relationships between radial growth, tree size and lifespan of shade-intolerant mountain pines. For 200 dead standing mountain pines (Pinus montana) located along gradients of aspect, slope steepness and elevation in the Swiss National Park, radial annual growth rates and lifespan were reconstructed. While early growth (i.e. mean tree-ring width over the first 50 years) correlated positively with diameter at the time of tree death, a negative correlation resulted with lifespan, i.e. rapidly growing mountain pines face a trade-off between reaching a large diameter at the cost of early tree death. Slowly growing mountain pines may reach a large diameter and a long lifespan, but risk to die young at a small size. Early growth was not correlated with temperature or precipitation over the growing period. Variability in lifespan was further contingent on aspect, slope steepness and elevation. The shade-intolerant mountain pines follow diverging growth trajectories that are imposed by extrinsic environmental influences. The resulting trade-offs between growth rate, tree size and lifespan advance our understanding of tree population dynamics, which may ultimately improve projections of forest dynamics under changing environmental conditions. PMID:26930294

  5. Comparative morphological trade-offs between pre- and post-copulatory sexual selection in Giant hissing cockroaches (Tribe: Gromphadorhini)

    PubMed Central

    Durrant, Kate L.; Skicko, Ian M.; Sturrock, Craig; Mowles, Sophie L.

    2016-01-01

    Sperm competition theory predicts that animals face a trade-off between investment in weaponry and investment in ejaculate composition. Within the Madagascan giant hissing cockroaches (Tribe Gromphadorhini) differences in morphology exist that may indicate differing strategies of male-male competition. We compared relative pronotal horn length using high-resolution X-ray CT scanning data, relative testes mass, and male-male agonistic behaviour between two species of hissing cockroaches, Gromphadorhina oblongonota and Aeluropoda insignis. The gross morphology and behaviour of these two species indicated that G. oblongonota is selected for pre-copulatory mate acquisition and that A. insignis is selected for post-copulatory sperm competition. We found evidence for a trade-off when investing in testes mass vs. horn length between the species. The large, aggressive G. oblongonota follows a strategy of greater investment in weapons at the expense of testes mass while the smaller, less-aggressive A. insignis invests in relatively greater testes mass and less in pronotal weapon length. We also found evidence of a trade-off within each species, where individuals invest more heavily in weapon length at the expense of testes mass. These findings support the predictions of pre- and post-copulatory competitive investment trade-offs for a relatively understudied Tribe of cockroaches. PMID:27819321

  6. Life-history constraints in grassland plant species: a growth-defence trade-off is the norm.

    PubMed

    Lind, Eric M; Borer, Elizabeth; Seabloom, Eric; Adler, Peter; Bakker, Jonathan D; Blumenthal, Dana M; Crawley, Mick; Davies, Kendi; Firn, Jennifer; Gruner, Daniel S; Harpole, W Stanley; Hautier, Yann; Hillebrand, Helmut; Knops, Johannes; Melbourne, Brett; Mortensen, Brent; Risch, Anita C; Schuetz, Martin; Stevens, Carly; Wragg, Peter D

    2013-04-01

    Plant growth can be limited by resource acquisition and defence against consumers, leading to contrasting trade-off possibilities. The competition-defence hypothesis posits a trade-off between competitive ability and defence against enemies (e.g. herbivores and pathogens). The growth-defence hypothesis suggests that strong competitors for nutrients are also defended against enemies, at a cost to growth rate. We tested these hypotheses using observations of 706 plant populations of over 500 species before and following identical fertilisation and fencing treatments at 39 grassland sites worldwide. Strong positive covariance in species responses to both treatments provided support for a growth-defence trade-off: populations that increased with the removal of nutrient limitation (poor competitors) also increased following removal of consumers. This result held globally across 4 years within plant life-history groups and within the majority of individual sites. Thus, a growth-defence trade-off appears to be the norm, and mechanisms maintaining grassland biodiversity may operate within this constraint.

  7. Life-history trade-offs mediate 'personality' variation in two colour morphs of the pea aphid, Acyrthosiphon pisum.

    PubMed

    Schuett, Wiebke; Dall, Sasha R X; Kloesener, Michaela H; Baeumer, Jana; Beinlich, Felix; Eggers, Till

    2015-01-01

    Life-history trade-offs are considered a major driving force in the emergence of consistent behavioural differences (personality variation); but empirical tests are scarce. We investigated links between a personality trait (escape response), life-history and state variables (growth rate, size and age at first reproduction, age-dependent reproductive rates, lifetime reproductive success, life span) in red and green colour morphs of clonal pea aphids, Acyrthosiphon pisum. Escape response (dropping/non-dropping off a plant upon a predatory attack) was measured repeatedly to classify individuals as consistent droppers, consistent nondroppers or inconsistents. Red morphs experienced stronger trade-offs between early reproduction and life span than green morphs; and red consistent (non)droppers had highest lifetime reproductive success. Red droppers followed a risk-averse life-history strategy (high late reproduction), red nondroppers a risk-prone strategy (high early reproduction), while reproductive rates were equivalent for all green behavioural types and red inconsistents. This suggests that red morphs suffer the highest costs of dropping (they are most conspicuous to predators), which 'equivalates' fitness payoffs to both risk-takers (red non-droppers) and risk-averse red droppers. The strong trade-off also means that committing to a particular lifestyle (being consistent) maximises fitness. Our study suggests that life-history trade-offs likely mediate personality variation but effects might depend on interactions with other organismal characteristics (here: colour morph).

  8. Like Hercules and the Hydra: Trade-offs and strategies in ecological model-building and experimental design.

    PubMed

    Inkpen, S Andrew

    2016-06-01

    Experimental ecologists often invoke trade-offs to describe the constraints they encounter when choosing between alternative experimental designs, such as between laboratory, field, and natural experiments. In making these claims, they tend to rely on Richard Levins' analysis of trade-offs in theoretical model-building. But does Levins' framework apply to experiments? In this paper, I focus this question on one desideratum widely invoked in the modelling literature: generality. Using the case of generality, I assess whether Levins-style treatments of modelling provide workable resources for assessing trade-offs in experimental design. I argue that, of four strategies modellers employ to increase generality, only one may be unproblematically applied to experimental design. Furthermore, modelling desiderata do not have obvious correlates in experimental design, and when we define these desiderata in a way that seem consistent with ecologists' usage, the trade-off framework falls apart. I conclude that a Levins-inspired framework for modelling does not provide the content for a similar approach to experimental practice; this does not, however, mean that it cannot provide the form.

  9. The Effects of Prenatal Alcohol Exposure on Adolescent Cognitive Processing: A Speed-Accuracy Trade-off.

    ERIC Educational Resources Information Center

    Sampson, Paul D.; Kerr, Beth; Olson, Heather Carmichael; Streissguth, Ann P.; Hunt, Earl; Barr, Helen M.; Bookstein, Fred L.; Thiede, Keith

    1997-01-01

    Aspects of cognitive processing were evaluated for 462 adolescents followed for 14 years. Adolescents had been exposed prenatally to a broad range of maternal drinking, mostly at "social" levels. Alcohol-related deficits on cognitive tasks were summarized by a speed-accuracy trade-off on the spatial-visual reasoning task. (SLD)

  10. Dealing with Food and Eggs in Mouthbrooding Cichlids: Structural and Functional Trade-Offs in Fitness Related Traits

    PubMed Central

    tkint, Tim; Verheyen, Erik; De Kegel, Barbara; Helsen, Philippe; Adriaens, Dominique

    2012-01-01

    Background As in any vertebrate, heads of fishes are densely packed with functions. These functions often impose conflicting mechanical demands resulting in trade-offs in the species-specific phenotype. When phenotypical traits are linked to gender-specific parental behavior, we expect sexual differences in these trade-offs. This study aims to use mouthbrooding cichlids as an example to test hypotheses on evolutionary trade-offs between intricately linked traits that affect different aspects of fitness. We focused on the oral apparatus, which is not only equipped with features used to feed and breathe, but is also used for the incubation of eggs. We used this approach to study mouthbrooding as part of an integrated functional system with diverging performance requirements and to explore gender-specific selective environments within a species. Methodology/Principal Findings Because cichlids are morphologically very diverse, we hypothesize that the implications of the added constraint of mouthbrooding will primarily depend on the dominant mode of feeding of the studied species. To test this, we compared the trade-off for two maternal mouthbrooding cichlid species: a “suction feeder” (Haplochromis piceatus) and a “biter” (H. fischeri). The comparison of morphology and performance of both species revealed clear interspecific and intersex differences. Our observation that females have larger heads was interpreted