Phylogenies & Evolutionary Ecology

The rate-limiting step for our work are complete phylogenies. Currently, complete species-level information on mammalian evolutionary relationships is not available in one source. Although there are now an ever-growing number of published studies using morphological or molecular gene sequences to construct the evolution of mammalian clades, it is scattered throughout the literature and is not easily accessible. A recent approach to building comprehensive, complete, species-level phylogenies is to combine all the available phylogenetic information into one consensus producing a phylogenetic supertree showing more precise and resolved relationships among taxa. Supertrees of primates, carnivores, bats and angiosperms have already been successfully used to estimate speciation and extinction rates, help identify those species most at risk (see Biodiversity and Extinction), and describe evolutionary patterns of biodiversity within hotspots (see Biology of Geographic Ranges). As part of the PanTheria project, we have now published a complete supertree of all mammals - below .

We are studying a diverse range of biological and anthropological processes that determine the biological richness of pathogens in mammals. Together with Charlie Nunn (postdoctoral Fellow, presently at the University of California, Davis), we have recently shown across primates and carnivores that white blood cell counts associated with disease risk are significantly related to mating systems - below. Presently, we are involved in a large international collaborative effort to examine epidemiological diversity across other mammal groups including ungulates, bats and rodents. Through an initiative sponsored by NCEAS (The National Center for Ecological Analysis and Synthesis in Santa Barbara, California), with additional funding from Conservational International, we have assembled a team of experts to examine the evolutionary and ecological interactions between social organization and the evolution of infectious pathogens. Presently, we are examining whether speciation rates in primates correlate with parasite richness, the amount of infectious diseases in threatened species, and potential losses of biodiversity if endangered hosts become extinct.

A flurry of important papers have recently shown that a range of biological problems from cellular to global can be described and understood from the scaling of changes in size. We are particularly interested in applying the methodology of scaling to problems of biodiversity and conservation. Working with Chris Carbone (Institute of Zoology, The Zoological Society of London) and Sam Ross, we are developing and testing models for within and between species variation in population density across the order Carnivora. Strikingly, we are finding for example that 10,000kg of prey supports 53kg of a given species of carnivore irrespective of body mass and that carnivore number/(unit prey biomass) approximate a quarter power scaling rule - below. Our models suggest that some carnivores (e.g., African wild dogs) are dangerously low in population density mainly due to reduced biomass levels. Our models may better enable conservation biologists to diagnose and predict extinction risk due to critical thresholds of low densities. We are also involved with an NCEAS Working Group examining the patterns of body size distributions across local to broad geographic space and from contemporary to "deep" time.