Research Themes

Paleomiddens

The body size of an organism is the result of a complex and dynamic interaction between physiology, life history, the environment, phylogenetic constraints and past history.  In turn, the ramifications of being a certain size are profound because of size dependent scaling relationships.  Consequently, the study of body size has long been a central area of research in both ecology and paleoecology.  My research seeks to bridge the gap between ecology and paleoecology by examining the various factors influencing mammalian body size across both ecological and evolutionary time.  For the most part, I focus on temperature because it fluctuates at both short and long time scales, can profoundly influence the physiology, life history and evolution of mammals, and it is of obvious importance in predicting the impact of anthropogenic climate change on ecosystems. To date, I have concentrated studies on the mammalian genus Neotoma (woodrats).  Not only are these small rodents extremely sensitive to temperature, but they produce paleomiddens that provide an unparalleled record of diet and body size over the late Quaternary.  I have a number of ongoing studies involving both paleo and contemporary woodrat populations:
 
Phylogeography and biogeographic history of the Neotoma complex in western North America:  population-level analysis of modern and ancient mtDNA. Collaborators:  Julio L. Betancourt (USGS), Jim L Patton (UC Berkeley), and Hendrik Poinar  (McMaster University). 
  
The Influence of Late Quaternary Climate Change on the Ecology and Evolutionary Dynamics of Small Mammalian Herbivores. Collaborators:  Julio L. Betancourt (USGS)
 
Heat, Death and Sex: did late Quaternary climate change select for a shift in reproductive strategy of woodrats in Death Valley?