Abstracts (first author)
Quick adaptation to a new environment erases signature of history in natural populations
In a world where human activity is changing the climate and habitats at a fast pace it is fundamental to understand how much and how quickly can species adapt. In the last few years we have witnessed the evolutionary response of various species to the effects of global warming. One such case is Drosophila subobscura, which presents clinal variation for body size and inversions, across three continents. Recent evidence shows that temporal changes are occurring in the clinal variation as a response to global warming, with northern populations becoming more similar to southern ones. Both local adaptation and gene flow may be involved, the latter possibly overcoming historical constraints. In this study we propose to measure the contributions of history and selection when populations initially differentiated in Nature are under a similar selective pressure, in order to test if the uniform selection erases prior genetic differences, even in the absence of gene flow. We used as scenario the adaptation to a new, common environment of three populations of Drosophila subobscura initially differentiated along the European latitudinal cline. Quick evolutionary response was observed in all foundations leading to full convergence. All foundations converged to the same adaptive peak, although at different rates and through different paths, suggesting an overall smooth fitness landscape. We concluded that although history had a strong effect during the initial generations, selection quickly overcame it, especially in fitness related traits. The fast loss of differentiation shows that, even in the absence of gene flow adaptation to a common environment can erase the variation observed in nature, a finding that raises concerns in Conservation terms.