Assessing Ecological Divergence and Speciation Scenarios of the Paragalago zanzibaricus Species Complex Through Climatic Niche Modeling

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.