Today's scientists are facing the enormous challenge of predicting how climate change will affect species distributions and species assemblages. To do so, ecologists are widely using phenomenological ...models of species distributions that mainly rely on the concept of species niche and generally ignore species' demography, species' adaptive potential, and biotic interactions. This review examines the potential role of the emerging synthetic discipline of evolutionary community ecology in improving our understanding of how climate change will alter future distribution of biodiversity. We review theoretical and empirical advances about the role of niche evolution, interspecific interactions, and their interplay in altering species geographic ranges and community assembly. We discuss potential ways to integrate complex feedbacks between ecology and evolution in ecological forecasting. We also point at a number of caveats in our understanding of the eco-evolutionary consequences of climate change and highlight several challenges for future research.
There is concern that the rate of environmental change is now exceeding the capacity of many populations to adapt. Mitigation of biodiversity loss requires science that integrates both ecological and ...evolutionary responses of populations and communities to rapid environmental change, and can identify the conditions that allow the recovery of declining populations. This special issue focuses on evolutionary rescue (ER), the idea that evolution might occur sufficiently fast to arrest population decline and allow population recovery before extinction ensues. ER emphasizes a shift to a perspective on evolutionary dynamics that focuses on short time-scales, genetic variants of large effects and absolute rather than relative fitness. The contributions in this issue reflect the state of field; the articles address the latest conceptual developments, and report novel theoretical and experimental results. The examples in this issue demonstrate that this burgeoning area of research can inform problems of direct practical concern, such as the conservation of biodiversity, adaptation to climate change and the emergence of infectious disease. The continued development of research on ER will be necessary if we are to understand the extent to which anthropogenic global change will reduce the Earth's biodiversity.
Ecology Letters (2012) 15: 378–392
Forest trees are the dominant species in many parts of the world and predicting how they might respond to climate change is a vital global concern. Trees are ...capable of long‐distance gene flow, which can promote adaptive evolution in novel environments by increasing genetic variation for fitness. It is unclear, however, if this can compensate for maladaptive effects of gene flow and for the long‐generation times of trees. We critically review data on the extent of long‐distance gene flow and summarise theory that allows us to predict evolutionary responses of trees to climate change. Estimates of long‐distance gene flow based both on direct observations and on genetic methods provide evidence that genes can move over spatial scales larger than habitat shifts predicted under climate change within one generation. Both theoretical and empirical data suggest that the positive effects of gene flow on adaptation may dominate in many instances. The balance of positive to negative consequences of gene flow may, however, differ for leading edge, core and rear sections of forest distributions. We propose future experimental and theoretical research that would better integrate dispersal biology with evolutionary quantitative genetics and improve predictions of tree responses to climate change.
This review proposes ten tentative answers to frequently asked questions about dispersal evolution. I examine methodological issues, model assumptions and predictions, and their relation to empirical ...data. Study of dispersal evolution points to the many ecological and genetic feedbacks affecting the evolution of this complex trait, which has contributed to our better understanding of life-history evolution in spatially structured populations. Several lines of research are suggested to ameliorate the exchanges between theoretical and empirical studies of dispersal evolution.
It is widely recognized that ecological dynamics influence evolutionary dynamics, and conversely that evolutionary changes alter ecological processes. Because fragmentation impacts all biological ...levels (from individuals to ecosystems) through isolation and reduced habitat size, it strongly affects the links among evolutionary and ecological processes such as population dynamics, local adaptation, dispersal and speciation. Here, we review our current knowledge of the eco‐evolutionary dynamics in fragmented landscapes, focusing on both theory and experimental studies. We then suggest future experimental directions to study eco‐evolutionary dynamics and/or feedbacks in fragmented landscapes, especially to bridge the gap between theoretical predictions and experimental validations.
Evolutionary rescue occurs when a population genetically adapts to a new stressful environment that would otherwise cause its extinction. Forecasting the probability of persistence under stress, ...including emergence of drug resistance as a special case of interest, requires experimentally validated quantitative predictions. Here, we propose general analytical predictions, based on diffusion approximations, for the probability of evolutionary rescue. We assume a narrow genetic basis for adaptation to stress, as is often the case for drug resistance. First, we extend the rescue model of Orr & Unckless (Am. Nat. 2008 172, 160–169) to a broader demographic and genetic context, allowing the model to apply to empirical systems with variation among mutation effects on demography, overlapping generations and bottlenecks, all common features of microbial populations. Second, we confront our predictions of rescue probability with two datasets from experiments with Saccharomyces cerevisiae (yeast) and Pseudomonas fluorescens (bacterium). The tests show the qualitative agreement between the model and observed patterns, and illustrate how biologically relevant quantities, such as the per capita rate of rescue, can be estimated from fits of empirical data. Finally, we use the results of the model to suggest further, more quantitative, tests of evolutionary rescue theory.
Climate change poses a particular threat to long‐lived trees, which may not adapt or migrate fast enough to keep up with rising temperatures. Assisted gene flow could facilitate adaptation of ...populations to future climates by using managed translocation of seeds from a warmer location (provenance) within the current range of a species. Finding the provenance that will perform best in terms of survival or growth is complicated by a trade‐off. Because trees face a rapidly changing climate during their long lives, the alleles that confer optimal performance may vary across their lifespan. For instance, trees from warmer provenances could be well adapted as adults but suffer from colder temperatures while juvenile. Here we use a stage‐structured model, using both analytical predictions and numerical simulations, to determine which provenance would maximize the survival of a cohort of long‐lived trees in a changing climate. We parameterize our simulations using empirically estimated demographic transition matrices for 20 long‐lived tree species. Unable to find reliable quantitative estimates of how climatic tolerance changes across stages in these same species, we varied this parameter to study its effect. Both our mathematical model and simulations predict that the best provenance depends strongly on how fast the climate changes and also how climatic tolerance varies across the lifespan of a tree. We thus call for increased empirical efforts to measure how climate tolerance changes over life in long‐lived species, as our model suggests that it should strongly influence the best provenance for assisted gene flow.
AbstractPrevious theory has shown that assortative mating for plastic traits can maintain genetic divergence across environmental gradients despite high gene flow. Yet these models did not examine ...how assortative mating affects the evolution of plasticity. We here describe patterns of genetic variation across elevation for plasticity in a trait under assortative mating, using multiple-year observations of budburst date in a common garden of sessile oaks. Despite high gene flow, we found significant spatial genetic divergence for the intercept, but not for the slope, of reaction norms to temperature. We then used individual-based simulations, where both the slope and the intercept of the reaction norm evolve, to examine how assortative mating affects the evolution of plasticity, varying the intensity and distance of gene flow. Our model predicts the evolution of either suboptimal plasticity (reaction norms with a slope shallower than optimal) or hyperplasticity (slopes steeper than optimal) in the presence of assortative mating when optimal plasticity would evolve under random mating. Furthermore, a cogradient pattern of genetic divergence for the intercept of the reaction norm (where plastic and genetic effects are in the same direction) always evolves in simulations with assortative mating, consistent with our observations in the studied oak populations.
Many theoretical models predict when genetic evolution and phenotypic plasticity allow adaptation to changing environmental conditions. These models generally assume stabilizing selection around some ...optimal phenotype. We however often ignore how optimal phenotypes change with the environment, which limit our understanding of the adaptive value of phenotypic plasticity. Here, we propose an approach based on our knowledge of the causal relationships between climate, adaptive traits, and fitness to further these questions. This approach relies on a sensitivity analysis of the process‐based model Phenofit, which mathematically formalizes these causal relationships, to predict fitness landscapes and optimal budburst dates along elevation gradients in three major European tree species. Variation in the overall shape of the fitness landscape and resulting directional selection gradients were found to be mainly driven by temperature variation. The optimal budburst date was delayed with elevation, while the range of dates allowing high fitness narrowed and the maximal fitness at the optimum decreased. We also found that the plasticity of the budburst date should allow tracking the spatial variation in the optimal date, but with variable mismatch depending on the species, ranging from negligible mismatch in fir, moderate in beech, to large in oak. Phenotypic plasticity would therefore be more adaptive in fir and beech than in oak. In all species, we predicted stronger directional selection for earlier budburst date at higher elevation. The weak selection on budburst date in fir should result in the evolution of negligible genetic divergence, while beech and oak would evolve counter‐gradient variation, where genetic and environmental effects are in opposite directions. Our study suggests that theoretical models should consider how whole fitness landscapes change with the environment. The approach introduced here has the potential to be developed for other traits and species to explore how populations will adapt to climate change.
Sexual dimorphism in plants may emerge as a result of sex‐specific selection on traits enhancing access to nutritive resources and/or to sexual partners. Here we investigated sex‐specific differences ...in selection of sexually dimorphic traits and in the spatial distribution of effective fecundity (our fitness proxy) in a highly dimorphic dioecious wind‐pollinated shrub, Leucadendron rubrum. In particular, we tested for the effect of density on male and female effective fecundity. We used spatial and genotypic data of parent and offspring cohorts to jointly estimate individual male and female effective fecundity on the one hand and pollen and seed dispersal kernels on the other hand. This methodology was adapted to the case of dioecious species. Explicitly modelling dispersal avoids the confounding effects of heterogeneous spatial distribution of mates and sampled seedlings on the estimation of effective fecundity. We also estimated selection gradients on plant traits while modelling sex‐specific spatial autocorrelation in fecundity. Males exhibited spatial autocorrelation in effective fecundity at a smaller scale than females. A higher local density of plants was associated with lower effective fecundity in males but was not related to female effective fecundity. These results suggest sex‐specific sensitivities to environmental heterogeneity in L. rubrum. Despite these sexual differences, we found directional selection for wider canopies and smaller leaves in both sexes, and no sexually antagonistic selection on strongly dimorphic traits in L. rubrum. Many empirical studies in animals similarly failed to detect sexually antagonistic selection in species expressing strong sexual dimorphism, and we discuss reasons explaining this common pattern.
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