Connectivity in fragmented landscape: Generalist and specialist gerbils show unexpected gene flow patterns

Landscape structure can affect connectivity among populations. In a patchy landscape, specialist species that are limited to particular elements are expected to show low gene diversity, low connectivity and high differentiation among patches. Conversely, for generalist species, genetic variability and gene flow among sites are expected to be high, and differentiation is expected to be low. Here we tested this hypothesis for two rodent species: Gerbillus gerbillus, the psammophile specialist species abundant in sandy habitats, and Gerbillus nanus, the parapatric habitat generalist species, found in the more stable sands in Israel and West Africa. We found that among the psammophile specialist G. gerbillus populations, differentiation was low and connectivity was high. In contrast, the parapatric generalist species G. nanus demonstrates markedly high genetic differentiation between localities within short distances in Israel. Furthermore, our results support a division between the African and the Israeli G. nanus populations, suggesting two distinct species.