Search for: All records

Black-and-white ruffed lemurs (Varecia variegata) are often described as highly sensitive to habitat disturbance (White et al., 1995; Balko, 1998; Ratsimbazafy, 2002; Ratsimbazafy, 2006; Herrera et al., 2011). In fact, local habitat quality has been shown to be a major predictor of Varecia occupancy across the species’ range (Morelli et al., 2020). In Ranomafana National Park, Varecia occupy several structurally and compositionally distinct sites. Disturbed sites—those previously subject to logging—have lower densities of shorter trees with smaller canopies and lower cover, as well as lower floristic diversity than undisturbed sites (Balko, 1998; Mancini, 2023). Resultantly, sites of lower quality habitat, particularly those with fewer large fruiting trees available, have lower population numbers of Varecia, with highly disturbed sites completely absent of this taxon (e.g., Herrera et al., 2011). However, our recent observations of Varecia in a disturbed forest site in Ranomafana National Park suggests the latter is not always the case. 

Cryptic species complexes consist of geographically confluent, closely related species that were once classified as a single species. The diversification mechanisms of cryptic species complexes often are mediated by environmental factors, which in some cases lead to ecological speciation. Niche-based distribution modeling can be an important tool in characterizing the extent of ecological divergence between species that may have resulted from environmentally driven speciation scenarios. We used climatic niche modeling to examine the degree of ecological divergence within the Paragalago zanzibaricus species complex in East Africa. We expected parapatrically distributed P. cocos and P. zanzibaricus to display a significant degree of climatic niche distinction and allopatrically distributed P. zanzibaricus and P. granti to exhibit a degree of niche conservatism. The extent of niche overlap between the three species was assessed by using a Niche Similarity Analysis (NSA) on bioclimatic values. Selected models for all three species exhibited good predictive ability, although the model for P. cocos was most optimal and appeared most consistent with its known range. NSA showed that P. cocos and P. zanzibaricus were statistically more similar than predicted from null distributional values. Results for NSA between the other two species pairings appear to be within the null distribution. The extent of niche overlap between all three species is consistent with the expectations of allopatric speciation processes. Future studies should examine alternative hypotheses for speciation within this group, including the role of sensory drive, interspecific competition, and the impact of Plio-Pleistocene climatic cycles. 

Dispersal is a fundamental aspect of primates’ lives and influences both population and community structuring, as well as species evolution. Primates disperse within an environmental context, where both local and intervening environmental factors affect all phases of dispersal. To date, research has primarily focused on how the intervening landscape influences primate dispersal, with few assessing the effects of local habitat characteristics. Here, we use a landscape genetics approach to examine between- and within-site environmental drivers of short-range black-and-white ruffed lemur (Varecia variegata) dispersal in the Ranomafana region of southeastern Madagascar. We identified the most influential drivers of short-range ruffed lemur dispersal as being between-site terrain ruggedness and canopy height, more so than any within-site habitat characteristic evaluated. Our results suggest that ruffed lemurs disperse through the least rugged terrain that enables them to remain within their preferred tall-canopied forest habitat. Furthermore, we noted a scale-dependent environmental effect when comparing our results to earlier landscape characteristics identified as driving long-range ruffed lemur dispersal. We found that forest structure drives short-range dispersal events, whereas forest presence facilitates long-range dispersal and multigenerational gene flow. Together, our findings highlight the importance of retaining high-quality forests and forest continuity to facilitate dispersal and maintain functional connectivity in ruffed lemurs.