The roles of phenotypic plasticity and adaptation in morphology and performance of an invasive species in a novel environment

Abstract

1. Species introductions provide insights into how populations respond to new environments and selection pressures through rapid adaptation and adaptive phenotypic plasticity. However, maladaptive responses are increasingly recognised to also be common in nature. The spotted‐wing drosophila, Drosophila suzukii, has rapidly invaded divergent environments providing the opportunity to examine adaptive and maladaptive phenotypic and evolutionary responses to its introduced range.2. We studied how population density in the field and wing size of individuals varied over an elevational gradient on Hawaii. We then conducted a reciprocal common garden experiment to evaluate how temperature influenced wing size and other correlates of fitness. We did this by reciprocally rearing D. suzukii collected from low and high elevations in temperatures representative of low and high elevation.3. We observed a wing size increase with elevation. Additionally, flies were more abundant at higher elevation. In the reciprocal common garden experiment, flies emerged faster in the warm, low‐elevation temperature and developed larger wings in the cool, high‐elevation temperature. Emergence of flies from high‐ and low‐elevation sites showed a pattern suggesting maladaptation to the temperature representing their home environment.4. We suggest that opposing selection pressures, the high vagility of flies, and extreme plasticity in body size constrain adaptation to temperature along an elevational gradient. Although successful invasive species such as D. suzukii often exhibit local adaptation, this research demonstrates that invasive species can be successful even without such adaptation.