Thermal physiology of Drosophila tripunctata across an urbanization gradient

In Drosophila spp., their often high number of annual generations, large population sizes, and large amounts of standing genetic variation should predispose them to undergo contemporary adaptation to climatic warming. However, a number of laboratory experimental evolution studies in this group of organisms suggest strong limits on the rate and magnitude of contemporary thermal adaptation. Here we explore this discrepancy by examining the potential for rapid evolutionary divergence between wild populations of Drosophila tripunctata (Loew 1962) from rural and urban sites. We performed a multi-generation common garden study and found evidence for the evolution of higher heat tolerance (critical thermal maximum) in urban population flies. We also detected evolutionary divergence in cold resistance (chill coma recovery time) with diminished cold resistance in urban population flies, though the effect was weaker than the shift in heat tolerance. Although our study provides evidence of contemp...