Meeting Abstract
55.7 Sunday, Jan. 5 15:00 Heterogeneity in Physiological Performance at the Northern Range Edge of a Tropical Frog Complex STREICHER, J.W.*; ROELKE, C.E.; FUJITA, M.K.; Univ. of Arizona; Univ. of Texas, Arlington; Univ. of Texas, Arlington streicher@uta.edu
The process of spatial sorting is thought to occur when differential dispersal capabilities assemble particular phenotypes at expanding range edges. This evolutionary mechanism may be particularly important to understand in lineages that are geographically widespread and ecologically diverse. Barking frogs (Craugastor augusti) are a polytypic species complex that occurs throughout mainland Mexico and the southwestern United States. These amphibians are typically surface active for only a few weeks each year that correspond to heavy spring and summer rains, so much of their biology is unknown. We used a mitochondrial gene fragment and nuclear genome wide SNP data to investigate phylogeographic relationships across the range of barking frogs. We identified multiple geographically circumscribed lineages within the complex and three at the northern range edge. We collected 23 individuals from two of these northern lineages (found to be sister taxa) and maintained them in captivity for several months before examining their physiological traits. Following this acclimation period, we measured oxygen consumption rates at two different temperatures; 24 and 30 C. While the response to temperature was similar in each lineage, we found evidence for significantly different oxygen consumption rates between lineages at both temperature conditions. Given laboratory acclimation, we think it is likely that the observed difference in routine metabolic rate has genetic underpinnings. As such, shifts in physiological phenotypes may have played an integral role in barking frog diversification across their ecologically dynamic range. Our findings are consistent with the tenet that when variable ecological conditions exist across an expanding range edge, environmentally related selective pressures may shift spatially sorted phenotypes along different evolutionary trajectories.
