Inter-island divergence within Drosophila mauritiana, a species of the D. simulans complex: past history and/or speciation in progress?

Speciation with gene flow may be more common than generally thought making detailed understanding of the extent and pattern of genetic divergence between geographically isolated populations useful. Species of the Drosophila simulans complex provide a good model for speciation and evolutionary studies; understanding their population genetic structure will increase our understanding of the context in which speciation has occurred. Here we describe the genetic diversity and the genetic differentiation, at mitochondrial and nuclear loci, of two distant populations of D. mauritiana (Mauritius and Rodrigues Islands). We surveyed the two populations for their mitochondrial types, eight nuclear genes and 18 microsatellite loci. A new mitochondrial type is fixed in the Rodrigues population of D. mauritiana. The two populations are highly differentiated, their divergence appears relatively ancient (100,000 years) compared to the origin of the species, around 0.25 MYA, and they exhibit very limite...