Lemur Diversification

My dissertation work focused on the ecomorphology of lemur teeth and what reconstructions of ancestral tooth shapes might reveal about the evolutionary history of lemurs. I used a class of measurements called dental topography metrics, which mathematically characterize the functional properties of tooth surfaces. Working with colleagues at Duke, I found the combinations of metrics that were best able to distinguish lemurs by dietary ecology, including folivores from insectivores, which has traditionally proven difficult. Leaves and insect tissues are both high in toughness, but the material properties of leaves may be less important than their fundamentally planar geometries. This appears to select for the elaboration of elongated cutting blades and relatively flat basins, driving high variability in tooth curvature (measured as a high coefficient of variation of Dirichlet normal energy). This observation was supported by a second study that tests for relationships between lemur community dental topography values and precipitation and precipitation seasonality at sites across Madagascar. I found that adaptations for processing leaves were not strongly related to their climatically inferred material properties, but instead to the likely importance of leaves in the diet of lemur communities.

We used these effective combinations of metrics to reconstruct dietary adaptation in extinct lemurs and applied phylogenetic modeling approaches to test for an adaptive radiation of lemur dietary strategies in the deep past. We combined ancestral state reconstructions of dental topography metrics with a novel approach to reconstructing continuous tooth shape across the evolutionary history of strepsirrhines and found that the spread of forests on Madagascar coincided with an expansion of lemur ecospace occupation apparently related to the exploitation of defended plant resources, including leaves.

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