Evolutionary history and taxonomy of the titi monkeys (callicebinae)
Titi monkeys (Callicebinae; Pitheciidae) are a diverse, species-rich group of New World primates with an extensive range across South America. They diverged from their sister clade (Pitheciinae) in the early Miocene, and thus, they comprise one of the oldest lineages of extant New World primates. To date, there has been no comprehensive molecular investigation of the phylogenetic relationships among Callicebinae species and, consequently, the evolutionary history of this diverse clade remains poorly studied. The overall goal of this PhD dissertation is, therefore, to provide insight into the evolutionary and biogeographic history of the subfamily Callicebinae using DNA sequence data. To infer phylogeny and estimate divergence times, we generated sequence data for 50+ wild-caught titi monkey specimens using multi-locus Sanger sequencing (22 nuclear and mitochondrial loci, > 14,500 bp) and reduced representation, genome-wide double-digest restriction-associated DNA (ddRAD) sequencing. A statistical biogeographical approach was employed to reconstruct the biogeography of Callicebinae and investigate the processes responsible for shaping present day distributions. Furthermore, the ddRAD sequence dataset was used to provide additional insight into phylogenetic relationships and genetic structure among taxa of the moloch group. Our phylogenetic and biogeographic results indicate that titi monkeys are divided into three distinct clades that diverged in the late Miocene through vicariance of a widespread ancestral range. Species relationships were generally recovered with strong support, and species-level diversification in the Amazonian clades was characterised by sequential founder events across river barriers in the Pleistocene. We propose a revised genus-level classification for Callicebinae that recognises three genera (Cheracebus, Callicebus, Plecturocebus) based on the results from the phylogenetic analyses, as well as morphological, karyological and biogeographic evidence. Overall, this study represents a major advance in our understanding of the evolutionary history of this strikingly poorly studied group, with implications for classification and research priorities.
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