Evolution of life history and dispersal traits during the range expansion of a biological control agent

Abstract

Evolutionary theory predicts that the process of range expansion will lead to differences between core and edge populations in life-history and dispersal traits. Selection and genetic drift can influence reproductive ability, while spatial sorting by dispersal ability can increase dispersal at the edge. However, the context individuals experience (e.g., population density and mating status) also impacts dispersal behavior. We evaluated theoretical predictions for evolution of reproductive life-history and dispersal traits using the range expansion of a biological control agent, Diorhabda carinulata, or northern tamarisk beetle. We found divergence between core and edge populations in fecundity, age at first reproduction, and female body mass. We also show that density and mating status influence dispersal and that dispersal increases at the edge of the range under some conditions. We find support for most predictions about evolution during range expansion, even across a heterogeneous environment, especially when the ecological context is considered.