SOME LIKE IT HOT? OR NOT? THE ASYMMETRY OF EVOLUTIONARY RESPONSE TO CLIMATE CHANGE ACROSS DIFFERENT TEMPORAL SCALES

Climate fluctuations influence the abundance, distribution and evolution of organisms. Yet, for many animals, the nature, magnitude, and timing of the response to these often abrupt climatic shifts remains unclear. In particular, the question of whether warming or cooling events challenge organisms evolutionary capabitilites to a greater extent has not been adequately addressed. Here, using modern and museum studies and the late Quaternary woodrat (Neotoma) paleomidden record, we examine the morphological response to climate change across the western United States across a variety of temporal scales. Our results demonstrate remarkable congruence across the geographic range at a variety of temporal scales. Chronosequences plotted for various locations demonstrate that woodrats respond as expected on the basis of Bergmann's rule: colder climatic conditions select for larger body size and warmer conditions select for smaller body size. However, warmer climatic oscillations are underrepresented in recovered paleomidden samples despite the trend towards increasing temperature from the last Glacial to present. We suspect our results indicate greater tolerance of Neotoma for variation in cold versus warm environmental temperature.