EVOLUTION OF BODY-SIZE IN THE WOODRAT OVER THE PAST 25,000 YEARS OF CLIMATE-CHANGE

Microevolutionary changes in the body size of the bushy-tailed woodrat (Neotoma cinerea) since the last glacial maximum were estimated from measurements of fecal pellets preserved in paleomiddens from the Great Basin and Colorado Plateau of the United States. The changes closely track regional temperature fluctuations simulated by the Community Cli mate Model of the National Center for Atmospheric Research and also th ose estimated from deuterium isotope ratios of plant cellulose recover ed from paleomiddens. Body size decreased during periods of climatic w arming, as predicted from Bergmann's rule and from physiological respo nses to temperature stress. Fossil woodrat middens, by providing detai led temporal sequences of body sizes from many locations, permit preci se quantification of responses to climatic change that have occurred i n the past and may occur in the future.