Meeting Abstract

5.4  Sunday, Jan. 4  Adaptation to Variable Ultraviolet Radiation Threats in Alpine Daphnia Populations MINER, B.E.*; KERR, B.; University of Washington; University of Washington miner@u.washington.edu

How do organisms evolve to tolerate environmental stresses that vary in space and time? This simple question is of critical importance in the current era of global climate change. In particular, one can study the relative importance of induced (acclimation) responses versus local (fixed) adaptation among populations with different environmental histories. In aquatic systems, organisms must frequently cope with exposure to harmful ultraviolet radiation (UVR) in habitats that exhibit high water clarity, such as those at high altitude. The evolutionary processes responsible for adaptations to high UVR habitats in zooplankton have received little attention to date, yet knowledge of such processes will be valuable in the near future, as some freshwater habitats are expected to exhibit increases in UVR transparency due to indirect effects of global climate change and other anthropogenic factors. We investigate the evolutionary history of adaptation to high and variable UVR exposure in multiple interconnected populations of the zooplankton Daphnia pulex in the Olympic Mountains of western Washington. Because these organisms inhabit ponds that are located in a forest-to-alpine transition zone, the UVR transparency of the ponds spans a wide range, such that some populations receive considerable UVR exposure while others receive almost none. We find that a populations tolerance to UVR in the laboratory mirrors the UVR threat in their natal pond. In addition, we find that local adaptation to UVR conditions outweighs acclimation effects in determining UVR tolerance. Finally, we evaluate differentiation for UVR tolerance in the context of neutral genetic differentiation among populations to gain insight into the evolutionary history of these adaptations.