For example, as temperature was experimentally increased, the amount of genetic variance in the fitness of Drosophila melanogaster decreased; in hot environments, flies had low evolvability . The hypothesis that heat-stress tolerance is evolutionarily constrained is further supported by experiments in which 22 Drosophila spp. drawn from tropical and temperate climes were subjected to extremes of heat and cold. They differed, as expected, in cold tolerances, but not in heat tolerances nor in temperatures at which optimal performances were observed .
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Climate Change 2022: Impacts, Adaptation and Vulnerability
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