Trait Plasticity in Herbivore Populations Maintains Geographic Patterns of Herbivory on a Dominant Plant Species Under Warming

ABSTRACT

Across species' geographic ranges, local populations may enlist behavioral, physiological, and morphological plasticity together to cope with stress from changing thermal conditions. But if local populations cannot sufficiently adjust their phenotype, then they may fail to persist, resulting in disassembly of their local communities. Thus, determining the fate of local populations and their constituent communities under changing thermal regimes requires understanding the integrative expression of plasticity across multiple fitness‐relevant traits. At two common garden field sites, we raised a dominant herbivore (grasshoppers) from six broadly distributed populations in New England under ambient and experimentally warmed conditions. Grasshoppers used both behavioral and physiological plasticity but blended the expression of the two traits in response to experimental warming in ways that depended on population origin. These responses enabled grasshoppers from the different populations to maintain similar estimated in situ metabolic rates, achieve similar survivorship, and exert similar, location‐specific patterns of trophic impact on two plant groups, including the competitive dominant plant in the system. The experimental results suggest that local populations may express different blends of trait plasticity in response to warming. Such responses may contribute to the maintenance of population resilience and local community dynamics under environmental warming.