Macroevolutionary dynamics of mammals
I am also interested in the evolution of body size in mammals and the role of constraints on minimum and maximum size over the last 65 ma. Using a global database of mammalian body sizes (Smith et al. 2003), we have shown that mammals under 18 g show differences in their diversification patterns compared to mammals over 18 g suggesting that when faced with novel environments small bodied mammals are more likely to evolve by changing body size than large bodied mammals (Smith et al., 2004). Biomechanical constraints are thought to play a role in limiting the maximum size of terrestrial mammals. Because the effect of these constraints should be limited in marine mammals because of the aquatic habitat, terrestrial and marine mammals should show differences in body size diversification. However, late Pleistocene terrestrial and marine mammals show no differences in their patterns of body size diversification, suggesting that biomechanical constraints do not play a major role in limiting maximum size of terrestrial mammals (Smith and Lyons, in revision).
With Felisa Smith and Morgan Ernest, I am a co-PI on a 5 year NSF grant to investigate the macroevolutionary dynamics of body size in mammals and the constraints on minimum and maximum size. This work will focus on the role of life history characteristics, ecology and phylogeny on the evolution of body size in mammals (see below).
Integrating Macroecologial Pattern and Processes across Scales
The body size of an organism reflects complex tradeoffs among numerous processes. Nevertheless, certain size-dependent relationships are repeatedly observed for mammals and other taxa. For example, the distribution of mammalian body sizes (i.e., minimum, maximum, and modal size) is remarkably similar across continents, despite little speices overlap. Moreover, distributions appear to have been similar for the past 50 million years. Do patterns arise because of common ancestry, because organisms exist in similar environments, or because they face similar design or life history constraints? The broad goal of this project is to assess the generality of body size patterns and investigate general underlying processes. The project assembles an international and distinguished team of scientists with expertise spanning the full spectrum of time, space, and various disciplines (e.g., paleontology, marine and terrestrial ecology, evolutionary biology, genetics). Anticipated results include the development of a comprehensive global database on life history, body size, geography, and phylogenetic relatedness for mammals as well as the development of novel analytical and statistical tools.
Collaborators: James Brown (University of New Mexico), Edward Bedrick (University of New Mexico), Alison Boyer (University of North Carolina, Chapel Hill), Daniel Costa (University of California Santa Cruz), Tamar Dayan (Tel-Aviv University), Alistair Evans (University of Helsinki), Mikael Fortelius (University of Helsinki), John Gittleman (University of Virginia), Richard Sibly (University of Reading), Jessica Theodor (University of Calgary), Mark Uhen (George Mason University).
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