Signals of recent spatial expansions in the grey mouse lemur (Microcebus murinus)
1 Institute of Zoology, University of Veterinary Medicine Hannover, Bünteweg 17, 30559 Hannover, Germany
2 CNRS, EDB (Laboratoire Evolution et Diversité Biologique), UMR CNRS/UPS 5174, F-31062 Toulouse, France
3 Université de Toulouse, UPS, EDB (Laboratoire Evolution et Diversité Biologique), Bâtiment 4R3 b2, 118 Route de Narbonne, F-31062 Toulouse, France
4 Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6, 2780-156 Oeiras, Portugal
5 Laboratory of Anthropology, Genetics and Peopling history (AGP), Department of Anthropology and Ecology, University of Geneva, 12 rue Gustave-Revilliod, 1211 Genève 4, Switzerland
BMC Evolutionary Biology 2010, 10:105 doi:10.1186/1471-2148-10-105Published: 22 April 2010
Pleistocene events have shaped the phylogeography of many taxa worldwide. Their genetic signatures in tropical species have been much less explored than in those living in temperate regions. We analysed the genetic structure of a Malagasy primate species, a mouse lemur with a wide distribution (M. murinus), in order to investigate such phylogeographic processes on a large tropical island. We also evaluated the effects of anthropogenic pressures (fragmentation/deforestation) and natural features (geographic distance, rivers) on genetic structure in order to complement our understanding of past and present processes of genetic differentiation.
The analysis of the mitochondrial D-loop sequences of 195 samples from 15 study sites (10 from a continuous forest and five from isolated forest fragments) from two adjacent Inter-River-Systems (IRSs) revealed that forest fragmentation and the river restrict gene flow, thereby leading to an increased genetic differentiation between populations beyond the effect of isolation-by-distance. Demographic simulations detected signals of two successive spatial expansions that could be preliminarily dated to the late Pleistocene and early Holocene. The haplotype network revealed geographic structure and showed deep molecular divergences within and between the IRSs that would be congruent with a two-step colonization scenario.
This study supports the hypothesis of a relatively recent spatial expansion of the grey mouse lemur in northwestern Madagascar, which may also explain why this taxon, in contrast to its congeners, has not yet undergone allopatric speciation in the studied area and possibly across its presently wide range.