Evolution of Plasticity in Response to Ethanol between Sister Species with Different Ecological Histories ( and ).

AbstractWhen populations evolve adaptive reaction norms in response to novel environments, it can occur through a process termed genetic accommodation. Under this model, the initial response to the environment is widely variable between genotypes as a result of cryptic genetic variation, which is then refined by selection to a single adaptive response. Here, I empirically test these predictions from genetic accommodation by measuring reaction norms in individual genotypes and across several time points. I compare two species of that differ in their adaptation to ethanol ( and ). Both species are human commensals with a recent cosmopolitan expansion, but only is adapted to ethanol exposure. Using gene expression as a phenotype and an approach that combines information about expression and alternative splicing, I find that exhibits cryptic genetic variation in the response to ethanol, while has almost no genotype-specific variation in reaction norm. This is evidence for adaptation to ethanol through genetic accommodation, suggesting that the evolution of phenotypic plasticity could be an important contributor to the ability to exploit novel resources.