Plasticity in evolutionary potential under environmental variation in a population of pied flycatchers, Ficedula hypoleuca
One major objective in evolutionary biology is to understand how the interplay between natural selection and genetic variation results in local adaptation. However, genetic changes in life-history traits produced after the consistent action of agents of selection are not widespread, particularly in breeding timing in birds. An alternative mechanism that allows local adaptation without genetic change is phenotypic plasticity. From an evolutionary perspective, phenotypic plasticity can be an evolutionary mechanism if there is additive genetic variation underlying trait plasticity. Here, we explored the role of microevolution and phenotypic plasticity as mechanisms of adaptive evolution in response to multiple climatic factors. We took advantage of “animal models” to explore the genetic basis of phenotypic plasticity and microevolution of laying date using a long-term study (1987-2016) of pied flycatchers (Ficedula hypoleuca) monitored at the individual level. Our results show: 1) a lack of temporal trend, due to large yearly variation in all climatic variables considered; 2) an increase in population density; 3) a lack of temporal trend in the genetic basis (breeding value) of breeding date; 4) statistical support for a genotype-by-environment interaction when considering the two most important climatic factors explaining selection on breeding date in the population: variation in spring temperature and mean North Atlantic Oscillation in winter. Given the presence of a genotype-by-environment interaction and the observed increase in population density, our results suggest that evolution may favor more plastic genotypes able to adapt to stochastic environments.