First signals of small-scale molecular edge effects in a non-human primate
Habitat edges lead to major ecological interactions of abiotic and biotic variables due to high ecological contrast. These processes are known to result in variable responses of plants and animals, although little is known about how animals respond to edge effects in tropical dry forests. In this context, interactions between edge effects and animal movement patterns are a critical yet largely unexplored area of ecological research. The aim of this study is to use population genetics tools to infer molecular edge effects in Microcebus ravelobensis, a small, nocturnal, arboreal, endangered lemur species, endemic to the dry deciduous forests of northwestern Madagascar. Microcebus ravelobensis was sampled in one edge and two interior habitats in close proximity to each other (500-1,400 m) in a continuous forest bordering abruptly on a savannah. A total of 41 individual mouse lemurs were genotyped with a suite of nuclear microsatellites to determine genetic diversity, genetic differentiation, and movements between the sites. Furthermore, the mitochondrial D-loop was sequenced to determine maternal lineages. The overall genetic diversity was lower in the edge habitat compared to the two interior sites, and all subpopulations showed relatively low genetic exchange and significant genetic differentiation, despite the short geographical distances that lie within the possible dispersal distance of single individuals. These findings support a local preference model and can be interpreted as the first signals of molecular edge effects, while suggesting the potential for local adaptation. Such an effect should have important conservation implications, since an additional molecular subdivision of already small populations inhabiting fragmented landscapes should further increase their vulnerability to stochastic demographic changes and collapse.