The study of competition has been a cornerstone of ecological research. Competition between related species may lead to exclusive ranges. Alternatively, similar species may develop behavioral or morphological differences in shared environments. These differences may serve two functions: 1) to mediate resource competition and 2) to reinforce reproductive barriers between species. The links between ecology and reproductive isolation form the basis of new and productive lines of inquiry.
In Malagasy lemurs, competition appears to have played a significant role in structuring communities. Despite a wealth of information on related pairs of species, few studies have examined competition between different populations of the same species. The overlap of populations with incomplete reproductive isolation is the focus of much speciation research. Thus, these populations represent a compelling test case for examining the interface of community ecology and speciation.
The present study proposes a 12-month field study of two brown lemur (Eulemur fulvus) subspecies in southeastern Madagascar. The project will investigate interactions between white-collared lemurs (E. f. albocollaris) and rufous lemurs (E. f. rufus) in a shared environment, as well as an isolated population of white-collared lemurs. Recent genetic studies suggest these animals may be separate species. However, natural hybrids are found at the boundary of their ranges. This area provides an opportunity to examine mechanisms of reproductive and ecological separation in these related populations.
The major questions of the study are: 1) What are the ecological and behavioral factors that permit white-collared and rufous lemurs to overlap? 2) What are the variables that prevent further expansion beyond the area of overlap? 3) How do these variables contribute to the limitations of gene flow between the subspecies?
To test these questions, the project will examine habitat structure, feeding ecology, population densities, and interactions between social groups. The following methods will be used: daily animal follows (recording feeding and social behavior), line transect censuses, and botanical sampling (including forest structure and food availability). In addition, genetic analyses will be conducted to clarify population affinities. Research will take place in consecutive seasons of resource scarcity (when niche separation is most marked) at one isolated white-collar lemur site and at one site in the area of subspecies overlap.
This project will integrate areas of particular interest in ecology and evolutionary studies: competition and speciation. Moreover, this research will provide new evidence to assist in the conservation of one of Madagascar's most endangered primates.
