Research


I study the ecology and biogeography of mammals in Southeast Asia, a region recently identified as one of the world's mammal hotspots by the IUCN. Using range maps, I am examining patterns in species distribution and richness throughout Southeast Asia. My research will focus on the Thai-Malay Peninsula, which bridges the transition zone between the Indochinese and Sundaic biogeographic subregions. Wallace identified this boundary at the very northern tip of the peninsula, but others have set the boundary up to 500 km farther south. Where does this boundary appear among mammals? Does this boundary affect Indochinese and Sundaic species equally, or does it represent more of an obstacle to one particular biota?

With its narrow base and wide tip, the Thai-Malay Peninsula forms an ideal setting to test the relative importance of the peninsula effect, where richness declines from peninsula base to tip, and the area effect, where richness is positively associated with land area. Along a latitudinal gradient, mammal species richness increases from 140 species in the Tenasserim Mountains between Thailand and Myanmar to over 180 species in the highlands of central Peninsula Malaysia. However, there is a precipitous drop in species richness along a 600-km long stretch in southern Thailand, where only 110 species occur, a decline of over 30% from expected richness based on latitude. These preliminary results suggest species richness is associated with a regional area effect.

In addition to these GIS-based analyses, I will conduct field studies to measure patterns in local richness, community organization, population structure, and niche breadth. I hypothesize that niche breadth will be negatively associated with species richness due to interspecific competition. I will compare small mammal communities at multiple sites along a 1000-km long latitudinal transect spanning the Thai-Malay Peninsula. At each site, I will use live trapping to measure abundance, body size, and home range size of 8-12 terrestrial rodent and treeshrew species. In addition, I will clip hair from each individual to quantify resource breadth and trophic level based on stable carbon and nitrogen isotope analysis, respectively. This measure of niche breadth will allow me to assess the relative conservatism or plasticity of species niches over a richness gradient.

At one of my study sites, I will include a local research component. In a large reservoir in Khlong Saeng Wildlife Sanctuary, southern Thailand, I will compare small mammal communities on islands formed by the reservoir and in forest patches adjacent to the reservoir. I will implement the same methodology to test the same hypotheses used in my regional study. By featuring this local component, I will be able to assess the relative influence of area effects at both a regional and local scale.

By documenting the plasticity of species niches, my research may be applied globally to assist predictions of future community changes due to ongoing land use and climate change.