Core‐marginal dynamics interact with sex and temperature to influence morphology of the rapidly expanding invasive kudzu bug (Megacopta cribraria)

Abstract

1. Invasive species present unique natural experiments through which to study evolutionary processes associated with spatial spread, especially with respect to rapid morphological evolution of dispersal‐related traits.2. The kudzu bug,Megacopta cribraria(Fabricius), established and expanded radially across the southeastern United States beginning in 2009. Here,M. cribrariais used as a model for studying rapid morphological change across an introduced range.3. Kudzu bugs were collected throughout the invasive range to test the hypothesis that body and wing size would increase with greater distance from the invasion source owing to dispersal‐related selection. The effects of sex, local temperature, and latitude were also evaluated to investigate how such factors might influence body and wing size across this range expansion.4. Females were significantly larger than males across all traits. Distance from the invasion core, temperature, and their interaction significantly influenced body size and wing length, suggesting thatM. cribrariawere larger near the invasion periphery. This was especially pronounced at cooler sites. Sex and distance were found to both weakly influence wing length after removing the effect of body size, suggesting that wing size may be disproportionally larger along the invasion front.5. The combined results indicate that a combination of spatial, environmental, and sexual factors must be considered when examining or predicting invasive species responses to new selective pressures and environments.