Interdepartmental Doctoral Program in Anthropological Sciences, Stony Brook University
Friday 173, Plaza Level
The mechanisms of speciation are related to the geographic distribution of populations, but the relative frequency of vicariance versus dispersal is debated. The lemurs of Madagascar are a model system to study modes of speciation because of their long isolation, geographic distributions and ecological variation. Many theories posit geographic or ecological causes for lemur species diversity and distribution, but few were generated using phylogenetic information. I tested the most likely biogeographic processes that may have led to lemur distribution and diversity. I first reconstructed the phylogeny of lemurs using a total evidence approach, combining molecular and morphological data. I used maximum parsimony and likelihood phylogenetic analyses on separate and combined datasets to build a robust phylogeny of living lemurs. I used maximum likelihood character tracing analyses to reconstruct the most likely geographic ranges of ancestral nodes to test if vicariance or dispersal best explains divergences. The total evidence analysis yielded stronger support for most nodes than morphological or molecular data alone (>75% bootstrap support). The character tracing analysis reconstructs the nodes of family-level divergences as from the northeast of Madagascar (>90% proportional likelihoods versus other biogeographic regions). Nodes of higher-level clades, like genera, are reconstructed as from the north or northeast, while clades within genera are more widely distributed, suggesting dispersal events to other regions. The results suggest that the ancestors of most lemur taxa had their origins in the north / northeast, and subsequent speciation events were due to dispersals to other regions.
This research was supported by the NSF (Graduate Research Fellowship), the Turner Fellowship (Summer Research Grant), and the Harvard MCZ (Ernst Mayr Grant).