In population dynamics, animal movement is often given species-typical values. This approach masks important behavioral variation among individuals. While individual variation in dispersal is well documented, it is unclear how individuality in dispersal affects other traits relevant to population dynamics. Behavioral variation among dispersers can produce clustering of individuals of similar phenotype in local habitat patches, known as spatial sorting. In landscapes composed of fragmented populations (e.g., metapopulations), spatial sorting among patches could influence eco-evolutionary feedbacks to alter long-term population dynamics. The first step to understand how spatial sorting can influence metapopulation dynamics is to determine which ecologically important life-history traits are genetically and phenotypically correlated with dispersal.
To accomplish this goal, we spatially sorted individuals by creating an environment where females sensitive to competition will disperse long distances to locate resources without competition. We artificially selected for beetles that did not disperse and beetles that dispersed long distances. We used these selected lines to evaluate the phenotypic and genetic correlation of multiple life-history traits with dispersal behavior.
Results/Conclusions
Individuals from lines selected for long distance dispersal moved farther than individuals from lines selected for philopatry, suggesting that our selection experiment led to evolutionary change in density-dependent dispersal. The disperser populations had a higher dispersal tendency than non-disperser populations, but there were no significant differences in general activity among the populations.
In disperser populations, both fecundity and body mass were positively genetically and phenotypically correlated with dispersal; however, in non-disperser populations, there were no detectable genetic or phenotypic correlations between these traits. Additionally, we found evidence that the populations selected for dispersal also evolved larger bodies, decreased fecundity, and slightly smaller eggs than non-disperser populations. We found no evidence that lifespan, larval development time, or larval competitive ability evolved differently between disperser and non-disperser populations.
When individuals spatially sort within fragmented landscapes, as simulated in our experiment, indirectly sorted life-history traits can interact with the local environment, ultimately leading to eco-evolutionary feedbacks that alter population dynamics. We propose fecundity as a key life-history trait that, through its phenotypic and genetic correlation with dispersal, is likely to alter the population dynamics of fragmented populations via spatial sorting.
