Meeting Abstract
Recent studies of populations inhabiting extreme environments have found contradictory results, with some observing reduced fecundity but little improvement in adult survival, and others failing to identify any evidence of higher fitness costs in extremophile populations. These contradictory findings suggest that evolutionary history and gene flow may strongly mediate the ability of populations to adapt to extreme environments. To test this hypothesis, we subjected six populations of Peromyscus mice to experimental elevational treatments — 1000, 3000, and 4500 m — in hypobaric chambers following acclimation to low elevation conditions. Our experiment included a mix of highland and lowland populations, with some of the highland populations coming from species with broad elevational distributions — suggesting the potential for ongoing gene flow across elevations — and others being strictly high elevation specialists. We measured the resting and summit metabolic rates, fecal corticosterone concentrations, and reactive oxygen species levels of individuals both before and after experimental treatments, with the expectation that all populations would exhibit heightened stress responses and reduced aerobic capacities at high elevations relative to lower elevations, but that strictly highland populations would show the smallest changes in stress levels and metabolic function. In combination with recent studies documenting the contributions of both flexible and canalized traits to observed extremophile phenotypes, our study suggests that inter-specific differences in both historical and contemporary demographic processes may help explain some of the life-history variation observed among these populations.
