Meeting Abstract
Populations of conspecifics that are distributed across a wide latitudinal range allow for the study of adaptation to varying local environments. Tigriopus californicus is a copepod found in high rocky tide pools along the west coast of North America. The relative genetic isolation of different populations, coupled with the range of thermal regimes to which they are exposed, make it an ideal study system for examining the evolution of thermal tolerance. Previous studies have shown that the southernmost populations of T. californicus have the highest survivorship following acute heat stress. In this study, we examine the physiological basis of heat tolerance. We hypothesize that adaptation among populations leads to differences in mitochondrial thermal performance and confers enhanced tolerance to southern populations. In order to understand the physiological basis for thermal tolerance, we measured ATP production, ROS presence, membrane potential, and electron transport system activity in both northern and southern populations. Despite common garden acclimation, we found differences in mitochondrial performance between northern and southern populations. Furthermore, we found evidence that suggests mitochondria are more thermally sensitive than whole animals. These results may indicate that mitochondria have an important role in setting the range limits of T. californicus populations and that nuclear and mitochondrial genes involved in mitochondrial functions may be targets for selection leading to adaptation to the thermal environment.
