Range shifts have become ubiquitous features of modern biomes due to the increasing pace and severity of anthropogenic climate change. Recent research has emphasized the importance of both ecological and evolutionary processes in driving the dynamics of range expansions and shifts. In particular, the process of spatial sorting (assortative mating of high dispersing individuals at the front of an expanding population) can lead to rapid evolution of increased dispersal abilities. While this process can be problematic in the context of invasive species, it may provide relief to populations shifting their ranges in response to climate change. However, studies have found conflicting evidence that dispersal evolution can rescue shifting populations, likely due to differences in key assumptions governing the genetic architecture of the dispersal trait. We set out to determine how different facets of genetic architecture influence the ability of dispersal evolution to rescue populations during range shifts. We constructed an individual-based model varying multiple aspects of dispersal genetic architecture (number of loci encoding dispersal, haploid vs. diploid genomes, and asexual vs. sexual reproduction) in range shifting populations. Using the model, we evaluated genetic architecture’s influence on the speed of dispersal evolution and corresponding extinction risk for populations undergoing range shifts.
Results/Conclusions
By using a single framework, we directly compared the effect of differing genetic architectures on the rate of dispersal evolution and extinction risk due to climate change. We first quantified the rate of dispersal evolution due to spatial sorting as it varied with genetic architecture, showing that simplified genetic architectures (e.g. haploid genomes or few loci) resulted in more rapid evolutionary changes in dispersal. Importantly, these differences in the rate of dispersal evolution dramatically impacted extinction risk during range shifts. Populations characterized by slow dispersal evolution experienced much greater extinction risks during climate change. Many theoretical studies have used simplified genetic architectures when modeling dispersal and our results suggest this could lead to an important bias in model predictions. Namely, they may predict higher likelihoods of population rescue via dispersal evolution than should be expected from systems with more complex genetic architecture. This study helps reconcile previous discrepancies in the literature concerning the role of dispersal evolution in rescuing shifting populations, pointing to the critical role of underlying differences in genetic architecture. Future studies combining models with empirical tests are needed to illuminate the circumstances under which dispersal evolution might play an important role in climate-driven range shifts.