Using species distribution modeling to assess factors that determine the distribution of two parapatric howlers (Alouatta spp.) in South America

Abstract

We used the ecological niche model MaxEnt to predict the potential distribution of the brown howler monkey (Alouatta guariba clamitans) and the black-and-gold howler monkey (Alouatta caraya) in South America, as well as the potential sympatry area between both species. We used 271 presence localities for A. caraya and 127 for A. guariba clamitans and 8 and 13 (respectively) bioclimatic variables from WorldClim to build a MaxEnt model in which habitat suitability was categorized as low, moderate or high presence probability. The black-and-gold howler monkey shows a broader potential distribution, occupying a wide variety of habitats in an ample range of temperatures. Temperature annual range (Bio 7) was the bioclimatic variable with the most influence in modeling this species potential distribution. The brown howler monkey was more restricted to rainy areas of mature forests that are placed in higher altitudes with low minimum temperatures. Mean temperature of coldest quarter (Bio 11) was the bioclimatic variable with the highest influence in this model. Predicted potential sympatry area between both species resulted in a relatively small area placed in the interior Atlantic Forest ecoregion. The Paraná river as a natural barrier for dispersion, differences in niche requirements and potential interspecific competition could be some of the causes that maintain a narrow zone of overlap between these two howler monkey species.