Mouse Lemur Phylogeography Revises a Model of Ecogeographic Constraint in Madagascar

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Abstract

Mouse lemurs (genus Microcebus) are small nocturnal primates that are ubiquitously distributed throughout Madagascar. Until the past decade or so, it was believed that there were only two species, one that occupied the eastern regions of Madagascar (M. rufus) and one that occupied the western regions of Madagascar (M. murinus). Intensive field studies, accompanied by genetic analysis, have revealed that the two species taxonomy vastly underestimates the actual species diversity, however, with eight species now recognized. There are numerous indicators that even the eight species taxonomy is an insufficient representation of their actual evolutionary diversity. Our chapter reviews some of the evidence both for the presently acknowledged species diversity, and clarifies the evidence for supposing that there are other species yet to be identified. Primarily, the chapter focuses on the unexpected phylogeographic patterns revealed by mitochondrial DNA analysis. These data show that mouse lemur species do not form western and eastern clades, as ecogeographic evidence might suggest. Rather, there appears to be a historical separation of species into northern and southern clades. We emphasize the point, however, that this latter pattern is based on incomplete species and geographic sampling. Only complete sampling of populations from all regions of Madagascar will reveal the true historical patterns of mouse lemur evolution.