The patterns we observed in this study support the idea that multiple factors have been important. For example, allopatric speciation due to the contraction of the forest and the formation of refugia could have been the cause of speciation for A. belzebuth and A. chamek as the recent timing of their split ( 1.8 mya) coincides with a time during the Cenozoic when ecological conditions were not stable in tropical latitudes, especially during the early Pleistocene (Haffer, 2008; Morley, 2000). During this time, alter nating humid and dry climatic periods, as well as warm and cold periods, led to continuous vegetation changes and allopatric speciation and subspeciation of other animal populations within Amazonia due to the contraction of forested and non-forested areas (Haffer, 2008). The origin of Ateles hybridus, on the other hand, was more likely due to isolation and divergence caused by the uplift of the Andes, consistent with a paleogeographic barrier hypothesis. The uplift of the northern Andes started 23 mya but had peaks of activity 12 mya and 4.5 mya (Hoorn et al., 2010),