MAMMAL COMMUNITY STRUCTURE OVER TIME AND SPACE

What factors act to influence the structure of mammal communities? How persistent are these over geological space or evolutionary time? Using a database constructed from the literature that spans the Cenozoic and with representation from multiple continents and various habitat types, we investigate mammalian body size distributions at multiple levels of the ecological hierarchy across both space and time. Our results clearly demonstrate that: a) the modern bimodal continental pattern found in Africa has a deep history and first developed approximately 40 million years ago. The distribution of mammals on other continents were once quite similar, but changed as a result of the terminal Pleistocene extinction of the megafauna; b) both currently, and in the deep time fossil record, local level body size distributions are strongly influenced by habitat type and other biome level factors. Specifically, increased habitat structure and productivity lead to more peaked body size distributions presumably because a greater number of ‘medium’ sized mammals can be supported. Because we find consistent patterns across the Cenozoic for both modern and archaic mammal faunas, we suspect both have responded similarly to increased environmental complexity.

Additional authors: A.G. Boyer, J.H. Brown, D.P. Costa, A.R. Evans, M. Fortelius, J.L. Gittleman, M.J. Hamilton, L.E. Harding, K. Lintulaakso, J.G. Okie, J.J. Saarinen, P.R. Stephens, J. Theodor, M.D. Uhen, and R.M. Sibly.