Population genetic effects of human‐mediated plant range expansions on native phytophagous insects

Abstract

Anthropogenic changes in organismal distributions have affected many, if not all, terrestrial ecosystems. Anthropogenic plant range expansions (APREs) may have profound effects on the population genetics of native phytophagous insects exploiting recent changes in plant distributions. Here I focus on the important, although often overlooked, effects on insect species which feed on such plants, but do not show evidence of host race formation. This article investigates geographic range expansion and increased interpopulation gene flow, which may occur as a result of phytophagous insects exploiting APREs. The two effects have clear predicted genetic signatures: (1) geographic range expansion should result in low levels of genetic diversity in new portions of the insect species’ range, relative to older, pre‐APRE portions of the range and (2) increased interpopulation gene flow will result in reduced population genetic differentiation. Data from the literature are qualitatively consistent with the predictions of one or both population genetic change scenarios. Higher order effects, such as reduced local adaptation, increased spread of resistance in agricultural systems, and hybridization among formerly isolated lineages, as evidenced by case studies, and the economic and conservation implications thereof are also discussed. Finally, I outline future approaches for addressing the impact of APREs on native phytophagous insect ecology and discuss the application of these concepts of population genetic change and resultant outcomes to research outside plant–insect interactions.