Meeting Abstract
In species that are distributed across steep elevational gradients, adaptive variation in physiological performance may be attributable to both transcriptional plasticity and canalization in underlying regulatory networks. We performed a series of common-garden experiments that were designed to elucidate the role of regulatory plasticity in evolutionary adaptation to hypoxic cold-stress in deer mice (Peromyscus maniculatus). Using a system-biology approach, we integrated genomic transcriptional profiles with assays of metabolic enzyme activities, tissue-level phenotypes, and measures of whole-animal thermogenic performance under hypoxia in highland (4350m) and lowland (430m) mice from three experimental groups: (1) wild-caught mice that were sampled at their native elevations; (2) wild-caught/lab-reared mice that were deacclimated to low-elevation conditions in a common-garden lab environment; and (3) the F1 progeny of deacclimated mice that were maintained under low-elevation common-garden conditions. Highland mice exhibited consistently greater thermogenic capacities than lowland mice, which was associated with enhanced oxidative fiber density and capillarity in skeletal muscle. Performance differences were also associated with greater activities of oxidative enzymes and both constitutive and plastic changes in the expression of transcriptional modules that influence hierarchical steps in the O2 cascade, including tissue O2 diffusion (angiogenesis) and tissue O2 utilization (muscle fiber composition, metabolic fuel use, and cellular oxidative capacity). These results suggest that both regulatory plasticity and canalization make important contributions to physiological performance, but their relative contributions vary among steps in the O2 transport cascade.
