P3.197 Friday, Jan. 6 Emerging patterns of microendemism in the rodent Eliurus myoxinus within Madagascar's western forests SHI, Jeff J.*; CHAN, Lauren M.; RAKOTOMALALA, Zafimahery; GOODMAN, Steven M.; YODER, Anne D.; Duke University; Duke University; Université d'Antananarivo; Field Museum of Natural History; Duke University email@example.com
Madagascar is considered one of the world's irreplaceable biodiversity hotspots, characterized by its incredible levels of species diversity and endemism. This, coupled with its long isolation from other landmasses, makes Madagascar ideal for the study of speciation and differentiation without the confounding influences of migration and colonization. Using DNA sequence data from one mitochondrial and two nuclear loci, we examined patterns of phylogeographic differentiation in Eliurus myoxinus, an endemic rodent widespread along the western coast and its dry forests. Our aims were twofold: to assess whether extant patterns of genetic diversity were concordant with two previously established biogeographic models, and to examine possible evolutionary mechanisms that have shaped this diversity. The genetic diversity of E. myoxinus best fits an established model based on current climate gradients, but cannot be fully explained by either of the proposed biogeographic models. The phylogenetic relationships suggest that E. myoxinus originated in the southwest and expanded along the west coast into its current distribution. At least three diverging centers of microendemism were identified along the western coast, though with some gene flow between them. Importantly, this study highlights evolutionary processes resulting in latitudinal divergence within this species. This adds to recent evidence for differentiation between north and south as opposed to the more traditional dichotomy between eastern and western Madagascar.