Taxonomy and Conservation

Byrne et al 2016 - Titi monkeys, Callicebus, comprise the most species-rich primate genus—34 species are currently recognised, five of them described since 2005. The lack of molecular data for titi monkeys has meant that little is known of their phylogenetic relationships and divergence times. To clarify their evolutionary history, we assembled a large molecular dataset by sequencing 20 nuclear and two mitochondrial loci for 15 species, including representatives from all recognised species groups. Phylogenetic relationships were inferred using concatenated maximum likelihood and Bayesian analyses, allowing us to evaluate the current taxonomic hypothesis for the genus. Results: Our results show four distinct Callicebus clades, for the most part concordant with the currently recognised morphological species-groups—the torquatus group, the personatus group, the donacophilus group, and the moloch group. The cupreus and moloch groups are not monophyletic, and all species of the formerly recognized cupreus group are reassigned to the moloch group. Two of the major divergence events are dated to the Miocene. The torquatus group, the oldest radiation, diverged c. 11 Ma; and the Atlantic forest personatus group split from the ancestor of all donacophilus and moloch species at 9–8 Ma. There is little molecular evidence for the separation of Callicebus caligatus and C. dubius, and we suggest that C. dubius should be considered a junior synonym of a polymorphic C. caligatus. Conclusions: Considering molecular, morphological and biogeographic evidence, we propose a new genus level taxonomy for titi monkeys: Cheracebus n. gen. in the Orinoco, Negro and upper Amazon basins (torquatus group), Callicebus Thomas, 1903, in the Atlantic Forest (personatus group), and Plecturocebus n. gen. in the Amazon basin and Chaco region (donacophilus and moloch groups).

Byrne, H. Rylands, A., Nash, S. and Boubli, J. 2020 PRIMATE CONSERVATION- Abstract - The collared titi, Cheracebus torquatus, is paradoxically the least well-defined of the so-called "torquatus group" of Neotropical titi monkeys. Since its description by Hoffmannsegg in 1807, it has been re-characterized numerous times. In this study, the true identity of Cheracebus torquatus is assessed based on a review of its taxonomic history and the observation of 100 skins from across the genus Cheracebus, including the holotype for C. torquatus. We propose that the C. torquatus type specimen and type description fit most closely with widow monkeys found south of the Rio Solimões between the rios Juruá and Purus, and we conclude that purinus Thomas, 1927, is a junior synonym of torquatus. This necessarily invalidates the torquatus type locality, as defined by Hershkovitz, of Codajás, north (left) bank of the Solimões, and we thus restrict the type locality to Aiapuá, left bank of the Rio Purus, Brazil. The left bank Rio Solimões populations that were previously classified as C. torquatus (sensu Hershkovitz) are here included as lugens, and we redefine C. lugens to include all Cheracebus found north of the Solimões-Japurá-Caquetá. We discuss the broad phenotypic variation found across C. lugens specimens and the existence of three C. lugens lineages in molecular phylogenies, as well as issues with the classification of other forms recognized by Hershkovitz. To conclude, we currently consider the genus Cheracebus to comprise five widow monkey species-torquatus (formerly purinus), regulus, lucifer, medemi and lugens.