Influence of forest fragmentation on an endangered large-bodied lemur in northwestern Madagascar

Madagascar’s diverse and mostly endemic fauna and flora suffer from recent landscape changes that are primarily caused by high levels of human activities. The loss and fragmentation of forest habitats are well known consequences of human activities. In this study, we investigate the effects of forest fragmentation on presence, abundance and genetic diversity in a larger-bodied lemur species, Lepilemur edwardsi, in northwestern Madagascar. In addition, we characterized the genetic differentiation among populations and demographic changes. We found L. edwardsi at only 13 (76.5%) of 17 visited sites, 11 of which were situated in the Ankarafantsika National Park (ANP). We captured between two and 17 individuals per site. We sequenced the mtDNA d-loop of all samples and genotyped 14 microsatellite loci in two exemplary populations for demographic analyses. A negative influence on forest fragmentation could be detected, since the fragments had a lower genetic diversity than sites in the ANP. Genetic differentiation between populations ranged from low to high but was almost always significant. A typical pattern of isolation-by-distance could not be detected and the data could rather be interpreted as results of random genetic drift. The data furthermore revealed signals of a demographic collapse of about two orders of magnitude in the two exemplary sites. This decline probably started during the last few hundred years of intensified human disturbances and population growth. Given the results of this study, urgent conservation actions are needed and should concentrate on an effective protection of the few remaining populations in order to ensure the long-term survival of L. edwardsi.