American NaturalistPub Date : 2025-02-01Epub Date: 2024-12-12DOI: 10.1086/733456
Victoria Caudill, Peter Ralph
{"title":"Genetic Architecture, Spatial Heterogeneity, and the Arms Race between Newts and Snakes: Exploring Coevolution with Simulations.","authors":"Victoria Caudill, Peter Ralph","doi":"10.1086/733456","DOIUrl":"10.1086/733456","url":null,"abstract":"<p><p>AbstractCoevolution between two species can lead to exaggerated phenotypes that vary in a correlated manner across space. However, the conditions under which we expect such spatially varying coevolutionary patterns in polygenic traits are not well understood. We investigate the coevolutionary dynamics between two species undergoing reciprocal adaptation across space and time using simulations inspired by the <i>Taricha</i> newt/<i>Thamnophis</i> garter snake system. One striking observation from this system is that newts in some areas carry much more tetrodotoxin than in other areas, and garter snakes that live near more toxic newts tend to be more resistant to this toxin, a correlation seen across several broad geographic areas. Furthermore, snakes seem to be \"winning\" the coevolutionary arms race, that is, having a high level of resistance compared with local newt toxicity, despite substantial variation in both toxicity and resistance across the range. We explore how possible genetic architectures of the toxin and resistance traits would affect the coevolutionary dynamics by manipulating both mutation rate and effect size of mutations across many simulations. We find that coevolutionary dynamics alone were not sufficient in our simulations to produce the striking mosaic of levels of toxicity and resistance observed in nature, but simulations with ecological heterogeneity (in trait costliness or interaction rate) did produce such patterns. We also find that differences in polygenicity do not seem sufficient to explain the observation that snakes seem to be winning.</p>","PeriodicalId":50800,"journal":{"name":"American Naturalist","volume":"205 2","pages":"184-202"},"PeriodicalIF":2.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143366698","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
American NaturalistPub Date : 2025-02-01Epub Date: 2025-01-15DOI: 10.1086/733434
Sebastian J Schreiber
{"title":"Partitioning the Impacts of Spatial-Temporal Variation in Demography and Dispersal on Metapopulation Growth Rates.","authors":"Sebastian J Schreiber","doi":"10.1086/733434","DOIUrl":"10.1086/733434","url":null,"abstract":"<p><p>AbstractSpatial-temporal variation in environmental conditions is ubiquitous in nature. This variation simultaneously impacts survival, reproduction, and movement of individuals and thereby the rate at which metapopulations grow. Using the tools of stochastic demography, the metapopulation growth rate is decomposed into five components corresponding to temporal, spatial, and spatial-temporal variation in fitness and spatial and spatial-temporal covariation in dispersal and fitness. While temporal variation in fitness always reduces the metapopulation growth rate, all other sources of variation can either increase or reduce the metapopulation growth rate. Increases occur either by reducing the impacts of temporal variation or by generating a positive fitness-density covariance where individuals tend to concentrate in higher-quality patches. For example, positive autocorrelations in spatial-temporal variability in fitness generate this positive fitness-density covariance for less dispersive populations but decrease it for highly dispersive populations (e.g., migratory species). Negative autocorrelations in spatial-temporal variability have the opposite effects. Positive covariances between movement and future fitness, on short or long timescales, increase growth rates. These positive covariances can arise in unexpected ways. For example, the win-stay, lose-shift dispersal strategy in negatively autocorrelated environments can generate positive spatial covariances that exceed negative spatial-temporal covariances. This decomposition of the metapopulation growth rate provides a way to quantify the relative importance of fundamental sources of variation for metapopulation persistence.</p>","PeriodicalId":50800,"journal":{"name":"American Naturalist","volume":"205 2","pages":"149-169"},"PeriodicalIF":2.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143366705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
American NaturalistPub Date : 2025-02-01Epub Date: 2024-12-09DOI: 10.1086/733307
Michela N Dumas, Christoph M Meier, Pierre Bize, Julien G A Martin
{"title":"Who Keeps the House after Divorcing? Partner and Nest Fidelity in the Long-Lived Alpine Swift.","authors":"Michela N Dumas, Christoph M Meier, Pierre Bize, Julien G A Martin","doi":"10.1086/733307","DOIUrl":"10.1086/733307","url":null,"abstract":"<p><p>AbstractDespite the advantages of lasting pair bonds and the prevalence of monogamy, at least in avian species, some individuals switch mates (divorce). Divorce is generally considered to be adaptive (i.e., conferring net fitness benefits), although its causes and consequences often remain unclear, most notably regarding the genetic basis of this behavior. Using more than 30 years of data in a long-lived bird with obligate biparental care, the Alpine swift, we first described the overall patterns of mate and nest site fidelity and investigated the predictors of between-year divorce. We show that 16.6% of pairings ended in divorce, with low reproductive success and young age as predictors of divorce, and that males retained the nest site more often than females. By then studying individual repeatability and heritability of divorce, we show moderate repeatability in females and low repeatability in males and little additive genetic variance in either sex. Finally, we assessed the fitness consequences of divorce and report that an active decision to modify the pair bond (divorce) may be more beneficial than reactionary re-pairing following a partner's death. Overall, divorce may provide some reproductive benefits for Alpine swifts, but no microevolutionary potential of this behavior is evident in this population.</p>","PeriodicalId":50800,"journal":{"name":"American Naturalist","volume":"205 2","pages":"224-239"},"PeriodicalIF":2.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143366733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
American NaturalistPub Date : 2025-01-01Epub Date: 2024-11-15DOI: 10.1086/733184
Emile Gluck-Thaler, Muhammad Arsam Shaikh, Corlett W Wood
{"title":"Multivariate Divergence in Wild Microbes: No Evidence for Evolution along a Genetic Line of Least Resistance.","authors":"Emile Gluck-Thaler, Muhammad Arsam Shaikh, Corlett W Wood","doi":"10.1086/733184","DOIUrl":"https://doi.org/10.1086/733184","url":null,"abstract":"<p><p>AbstractTrait evolution depends both on the direct fitness effects of specific traits and on indirect selection arising from genetically correlated traits. Although well established in plants and animals, the role of trait correlations in microbial evolution remains a major open question. Here, we tested whether genetic correlations in a suite of metabolic traits are conserved between two sister lineages of fungal endophytes and whether phenotypic divergence between lineages occurred in the direction of the multivariate trait combination containing the most genetic variance within lineages (i.e., the genetic lines of least resistance). We found that while one lineage grew faster across nearly all substrates, lineages differed in their mean response to specific substrates and in their overall multivariate metabolic trait means. The structure of the genetic variance-covariance (<b>G</b>) matrix was conserved between lineages, yet to our surprise divergence in metabolic phenotypes between lineages was nearly orthogonal to the major axis of genetic variation within lineages, indicating that divergence did not occur along the genetic lines of least resistance. Our findings suggest that the evolutionary genetics of trait correlations in microorganisms warrant further research and highlight the extensive functional variation that exists at very fine taxonomic scales in host-associated microbial communities.</p>","PeriodicalId":50800,"journal":{"name":"American Naturalist","volume":"205 1","pages":"107-124"},"PeriodicalIF":2.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142883424","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
American NaturalistPub Date : 2025-01-01Epub Date: 2024-11-22DOI: 10.1086/733104
Ashley Atkins Coleman, Kelly D Miller, Kelly L O'Neil, Rin Pell, Shelby R Green, E Keith Bowers
{"title":"Sex Allocation in a Monogamous Bird: Advantaged Matrilines and Sons with Silver Spoons.","authors":"Ashley Atkins Coleman, Kelly D Miller, Kelly L O'Neil, Rin Pell, Shelby R Green, E Keith Bowers","doi":"10.1086/733104","DOIUrl":"https://doi.org/10.1086/733104","url":null,"abstract":"<p><p>AbstractThe ability to secure food for offspring and withstand the cost of reproduction favors high-quality mothers that overproduce the larger sex, typically sons, only if they will receive adequate food, as this should enhance these sons' fitness returns. However, high-quality daughters ensure that grandoffspring receive quality parental care and may possess greater reproductive value than their brothers, favoring daughters also from high-quality mothers. Using a mixed cross-fostering approach, we investigated effects of early rearing conditions, covariance between breeders and their genetic parents in parental quality, and primary offspring sex ratios in Carolina wrens. In this socially and genetically monogamous bird, sons grew larger than daughters, paternal food provisioning impacted the condition and recruitment of sons but not daughters, and females overproduced sons when paired with males that provisioned at a high rate, reflecting females' anticipation of the quality of the rearing environment. Components of reproductive potential, including total fecundity, were inherited matrilineally, and all else being equal, females in better condition produced larger-than-average clutches biased toward daughters, who eventually produced larger-than-average clutches themselves. Sex ratios therefore varied with components of parental investment but in opposing directions for matrilineally inherited and environmental effects, suggesting that multiple countervailing selective forces shape sex ratio variation.</p>","PeriodicalId":50800,"journal":{"name":"American Naturalist","volume":"205 1","pages":"90-106"},"PeriodicalIF":2.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142883381","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
American NaturalistPub Date : 2025-01-01Epub Date: 2024-12-04DOI: 10.1086/733196
Ananda Shikhara Bhat, Vishwesha Guttal
{"title":"Eco-Evolutionary Dynamics for Finite Populations and the Noise-Induced Reversal of Selection.","authors":"Ananda Shikhara Bhat, Vishwesha Guttal","doi":"10.1086/733196","DOIUrl":"https://doi.org/10.1086/733196","url":null,"abstract":"<p><p>AbstractTheoretical studies from diverse areas of population biology have shown that demographic stochasticity can substantially impact evolutionary dynamics in finite populations, including scenarios where traits that are disfavored by natural selection can nevertheless increase in frequency through the course of evolution. Here, we analytically describe the eco-evolutionary dynamics of finite populations from demographic first principles. We investigate how noise-induced effects can alter the evolutionary fate of populations in which total population size may vary stochastically over time. Starting from a generic birth-death process, we derive a set of stochastic differential equations (SDEs) that describe the eco-evolutionary dynamics of a finite population of individuals bearing discrete traits. Our equations recover well-known descriptions of evolutionary dynamics, such as the replicator-mutator equation, the Price equation, and Fisher's fundamental theorem in the infinite population limit. For finite populations, our SDEs reveal how stochasticity can predictably bias evolutionary trajectories to favor certain traits, a phenomenon we call \"noise-induced biasing.\" We show that noise-induced biasing acts through two distinct mechanisms, which we call the \"direct\" and \"indirect\" mechanisms. While the direct mechanism can be identified with classic bet-hedging theory, the indirect mechanism is a more subtle consequence of frequency- and density-dependent demographic stochasticity. Our equations reveal that noise-induced biasing may lead to evolution proceeding in a direction opposite to that predicted by natural selection in the infinite population limit. By extending and generalizing some standard equations of population genetics, we thus describe how demographic stochasticity appears alongside, and interacts with, the more well-understood forces of natural selection and neutral drift to determine the eco-evolutionary dynamics of finite populations of nonconstant size.</p>","PeriodicalId":50800,"journal":{"name":"American Naturalist","volume":"205 1","pages":"1-19"},"PeriodicalIF":2.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142883412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
American NaturalistPub Date : 2025-01-01Epub Date: 2024-11-14DOI: 10.1086/733101
Jessie Mutz, Karen C Abbott
{"title":"Life History Modulates Effects of Inducible Defenses on Consumer-Resource Dynamics.","authors":"Jessie Mutz, Karen C Abbott","doi":"10.1086/733101","DOIUrl":"https://doi.org/10.1086/733101","url":null,"abstract":"<p><p>AbstractInducible defenses can affect the persistence, structure, and stability of consumer-resource systems. Theory shows that these effects depend on characteristics of the inducible defense, including timing, costs, efficacy, and sensitivity to consumer density. However, the expression and costs of inducible defenses often vary among life stages, which has not been captured in previous unstructured models. To explore how inducible defenses expressed in stage-structured populations affect consumer-resource dynamics, we developed a model based on the biology of plant-herbivore interactions, with the plant (resource) population structured into juvenile and mature stages. We then investigated the joint effects of inducible defenses and resource life history (i.e., patterns of fecundity, maturation, and mortality) by simulating dynamics for plant populations occurring along a fast-slow pace-of-life continuum. In general, high inducible defense costs, or a slow pace of life coupled with high herbivore growth rates, promoted persistent cycles. However, these cycles fundamentally differed, with either the plant or the herbivore population peaking first. Additionally, plant population pace of life influenced the relative effects of stage-specific induction strength on equilibrium densities and the extent to which inducible defenses enabled persistence. Our work illustrates how life history modifies the population-level effects of trait-mediated interactions, with implications for conservation and pest management.</p>","PeriodicalId":50800,"journal":{"name":"American Naturalist","volume":"205 1","pages":"41-54"},"PeriodicalIF":2.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142883420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
American NaturalistPub Date : 2025-01-01Epub Date: 2024-11-18DOI: 10.1086/733181
Jasper C Croll, Hal Caswell
{"title":"Family Matters: Linking Population Growth, Kin Interactions, and African Elephant Social Groups.","authors":"Jasper C Croll, Hal Caswell","doi":"10.1086/733181","DOIUrl":"10.1086/733181","url":null,"abstract":"<p><p>AbstractIn many species, individuals are embedded in a network of kin with whom they interact. Interactions between kin can affect survival and fertility rates and thus the life history of individuals. These interactions indirectly affect both the network of kin and the dynamics of the population. In this way, a nonlinear feedback between the kin network and individual vital rates emerges. We describe a framework for integrating these kin interactions into a matrix model by linking the individual kin network to a matrix model. We demonstrate the use of this framework for African elephant populations under varying poaching pressure. For this example, we incorporate effects of the maternal presence and matriarchal age on juvenile survival and effects of the presence of a sister on young female fecundity. We find that the feedback resulting from the interactions between family members shifts and reduces the expected kin network. The reduction in family size and structure severely reduces the positive effects of family interactions, leading to an additional decrease in population growth rate on top of the direct decrease due to the additional mortality. Our analysis provides a framework that can be applied to a wide range of social species.</p>","PeriodicalId":50800,"journal":{"name":"American Naturalist","volume":"205 1","pages":"E1-E15"},"PeriodicalIF":2.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142883415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
American NaturalistPub Date : 2025-01-01Epub Date: 2024-11-18DOI: 10.1086/733105
William S Cuello, Sebastian J Schreiber, Jennifer R Gremer, Pete C Trimmer, D Lawrence Venable, Andrew Sih
{"title":"Shifting Precipitation Regimes Influence Optimal Germination Strategies and Population Dynamics in Bet-Hedging Desert Annuals.","authors":"William S Cuello, Sebastian J Schreiber, Jennifer R Gremer, Pete C Trimmer, D Lawrence Venable, Andrew Sih","doi":"10.1086/733105","DOIUrl":"https://doi.org/10.1086/733105","url":null,"abstract":"<p><p>AbstractClimate change will affect both the mean and the variability in environmental conditions and may have major negative impacts on population densities in the future. For annual plants that already live in an extreme environment like the Sonoran Desert, keeping a fraction of their seeds dormant underground (for possibly years at a time) is critical to survive. Here, we consider how this form of bet hedging (i.e., delayed germination) for 10 Sonoran Desert annuals mediates responses to precipitation shifts. We use a demographic model parameterized with long-term field and precipitation data to explore how forecasted changes in precipitation impact annual plant species' population densities. We then examine how instantaneous evolution of optimal germination fractions in the shifted precipitation regimes bolsters population densities. Our results indicate that overall less rainfall and, to a lesser extent, increased variance in rainfall drive population levels down. Instantaneous evolution of optimal germination fractions in new regimes benefited species' populations only marginally, and only for small to moderate shifts in precipitation. Thus, even rapid evolution is unlikely to save populations experiencing larger shifts in precipitation. Finally, we predict that specialists that can capitalize on wet-year bonanzas or are water use efficient will be the most resilient to precipitation shifts as long as their seed survivorships are sufficiently high.</p>","PeriodicalId":50800,"journal":{"name":"American Naturalist","volume":"205 1","pages":"55-75"},"PeriodicalIF":2.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142883384","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
American NaturalistPub Date : 2025-01-01Epub Date: 2024-11-22DOI: 10.1086/733183
Sarah A Waybright, Michael E Dillon
{"title":"Soilscapes of Mortality Risk Suggest a Goldilocks Effect for Overwintering Ectotherms.","authors":"Sarah A Waybright, Michael E Dillon","doi":"10.1086/733183","DOIUrl":"https://doi.org/10.1086/733183","url":null,"abstract":"<p><p>AbstractChanging climates are driving population declines in diverse animals worldwide. Winter conditions may play an important role in these declines but are often overlooked. Animals must not only survive winter but also preserve body condition, a key determinant of growing season success. We hypothesized that ectotherms overwintering in soil face a trade-off between risks of cold damage (including freezing) near the surface and elevated energy use at deeper depths. To test this hypothesis, we developed landscapes of mortality risk across depth for overwintering bumble bee queens. These critical pollinators are in decline in part because of climate change, but little is known about how climate affects overwintering mortality. We developed a mechanistic modeling approach combining measurements of freezing points and the temperature dependence of metabolic rates with soil temperatures from across the United States to estimate mortality risk across depth under historic conditions and under several climate change scenarios. Under current conditions, overwintering queens face a Goldilocks effect: temperatures can be too cold at shallow depths because of substantial freezing risk but too hot at deep depths where they risk prematurely exhausting lipid stores. Models suggest that increases in mean temperatures and in seasonal and daily temperature variation will increase risk of overwinter mortality. Better predictions of effects of changing climate on dormant ectotherms require more measurements of physiological responses to temperature during dormancy across diverse taxa.</p>","PeriodicalId":50800,"journal":{"name":"American Naturalist","volume":"205 1","pages":"E16-E33"},"PeriodicalIF":2.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142883390","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}