The phylogeography of Cheracebus species located in the Rio Negro basin and its implications for our understanding of the historical biogeography of Amazonia

The Amazon holds the greatest primate diversity in the world. To date, little is known about how tis diversity originated. Recent evidence points to the role of rivers as important geographical barriers to primates and potential engines of speciation. Titi monkeys are the most diverse group of primates in the Amazon. Few studies have addressed the origins of such high diversity. Although it has been shown that large Amazonian rivers divide many titi monkey species, it is not known if smaller tributaries also play a role in separating sister species. In this study, we investigate if populations of widow titi monkeys Cheracebus lugens inhabiting the Rio Negro basin in Brazil present any genetic differentiation across this river’s left bank tributaries namely, Cauaburi, Marauia, Padauari, Araca and Demeni. We also examine for the first time using molecular phylogenetics, the phylogenetic relationships of C. lugens with other two species of this genus C. lucifer and C. purinus and the role of Japura and Solimoes rivers in the separation of these different species. We use three mitochondrial markers (COI, Cytochrome B, D-Loop) and one nuclear marker (RAG1). We constructed haplotype networks and preferred phylogenetic analysis to analyse their genetic differences. Our results show genetic differences for these markers between the three species of titi monkey but little variation between the samples of C. lugens collected on the left bank of Rio Negro. Suprisingly our samples of C. lugens from the right bank of Rio Negro were sister to the clade including C. purinus and C. lucifer, making C. lugens paraphyletic. However, the sample of size for this study of very small, and we should interpret our findings with a grain of salt. More samples will be required to fully understand the relationships amongst all species of widow titi monkeys and to better understand population level variability in C. lugens.