Plasticity vs. genotypic specialization in local adaptation
Both phenotypic plasticity and genotypic specialization can contribute to differences in physiological performance between populations that are locally adapted to different environments, but their relative contributions are predicted to vary according to the spatial grain of environmental variation. In animal species that are distributed across steep elevational gradients, dramatic changes in environmental conditions occur over relatively small spatial scales. This fine-grained environmental variation should be especially conducive to the evolution of phenotypic plasticity. Conversely, in species with narrow elevational distributions, theory predicts the evolution of genotypic specialization and canalized physiological traits. Because plasticity in organismal phenotypes is often mediated by transcriptional plasticity in underlying regulatory networks, assessing the degree of regulatory plasticity and regulatory canalization in species that differ in their elevational range limits can provide insights into mechanisms of physiological acclimatization. We are exploring these dynamics through comparative studies of physiological and transcriptomic plasticity among Peromyscus species that differ in their elevational range limits using experimental acclimations to hypobaric hypoxia and temperature challenges. We are also extending this line of research to other systems. For example, in collaboration with Shane Dubay, John Bates, and Trevor Price at the University of Chicago and the Fumin Li at the Chinese Academy Sciences, we are extending this framework to study avian species that differ in their degree of seasonal altitudinal migration in the Himalayas. We are also pursuing similar questions in a variety of other avian systems, including latitudinal comparisons of seasonal metabolic flexibility in several bird species, and osmoregulatory flexibility in populations of Savannah Sparrows (Passerculus sandwichensis) that have independently colonized saltmarsh habitats from ancestral inland habitats.