1Anatomy, The Geisel School of Medicine at Dartmouth, 2Anthropology, Dartmouth College, 3Anthropology, University of Massachusetts, Amherst
Saturday Afternoon, Ballroom A
Comparisons of primate diversity across subfossil and modern localities in Madagascar have concluded that there is a strong distinction between eastern (humid forest) and western (dry forest) communities. However, the subfossil record demonstrates that several extant species currently restricted to humid forests once had more widespread distributions. Furthermore, an east–west distance effect in extant mammal distributions has been interpreted as evidence that faunal exchange routes once crossed the central highlands. We ask: Can geographic patterning in lemur occurrence data shed light on hypotheses about past dispersal corridors? We assembled a database of extinct and still-extant lemur occurrences, geographic coordinates, elevation, and radiocarbon dates for subfossil and modern localities across Madagascar. These data were analyzed using spatial analysis software. Our results indicate that several inferred dry forest-dwelling extinct lemur taxa are shared among southern localities and south-central highlands. This lemur assemblage is fundamentally different from those recovered from subfossil sites crossing the mid-central highlands through the Antananarivo Province, which include still-extant eastern rainforest-dwelling lemurs, among others. The higher elevational distribution of subfossil sites in the mid-central versus the south-central highlands may have acted as a filter to limit species that may have dispersed across the island in the past. It has been suggested that watersheds with sources at high elevation may have maintained mesic conditions during Quaternary climate shifts due to orographic precipitation. For humid forest-dependent mammals, such mesic conditions may have allowed dispersal across a more northern passage, but limited dispersal of moisture-restricted animals in the south.