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Aim: Capuchin monkey species are widely distributed across Central and South America. Morphological studies consistently divide the clade into robust and gracile forms, which show extensive sympatry in the Amazon Basin. We use genetic data to test whether Miocene or Plio-Pleistocene processes may explain capuchin species' present distributions, and consider three possible scenarios to explain widespread sympatry. Location: The Neotropics, including the Amazon and Atlantic Coastal Forest. Methods: We sequenced the 12S ribosomal RNA and cytochrome b genes from capuchin monkey specimens. The majority were sampled from US museum collections and were wild-caught individuals of known provenance across their distribution. We applied a Bayesian discrete-states diffusion model, which reconstructed the most probable history of invasion across nine subregions. We used comparative methods to test for phylogeographic association and dispersal rate variation. Results: Capuchins contained two well supported monophyletic clades, the morphologically distinct 'gracile' and 'robust' groups. The time-tree analysis estimated a late Miocene divergence between Cebus and Sapajus and a subsequent Plio-Pleistocene diversification within each of the two clades. Bayesian analysis of phylogeographic diffusion history indicated that the current wide-ranging sympatry of Cebus and Sapajus across much of the Amazon Basin was the result of a single explosive late Pleistocene invasion of Sapajus from the Atlantic Forest into the Amazon, where Sapajus is now sympatric with gracile capuchins across much of their range. Main conclusions: The biogeographic history of capuchins suggests late Miocene geographic isolation of the gracile and robust forms. Each form diversified independently, but during the Pleistocene, the robust Sapajus expanded its range from the Atlantic Forest to the Amazon, where it has now encroached substantially upon what was previously the exclusive range of gracile Cebus. The genus Cebus, as currently recognized, should be split into two genera to reflect the Miocene divergence and two subsequent independent Pliocene radiations: Cebus from the Amazon and Sapajus from the Atlantic Forest.

BACKGROUND: 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).

Leptospirosis, the most widespread zoonotic disease in the world, is broadly understudied in multi-host wildlife systems. Knowledge gaps regarding Leptospira circulation in wildlife, particularly in densely populated areas, contribute to frequent misdiagnoses in humans and domestic animals. We assessed Leptospira prevalence levels and risk factors in five target wildlife species across the greater Los Angeles region: striped skunks ( Mephitis mephitis ), raccoons ( Procyon lotor ), coyotes ( Canis latrans ), Virginia opossums ( Didelphis virginiana ), and fox squirrels ( Sciurus niger ). We sampled more than 960 individual animals, including over 700 from target species in the greater Los Angeles region, and an additional 266 sampled opportunistically from other California regions and species. In the five target species seroprevalences ranged from 5 to 60%, and infection prevalences ranged from 0.8 to 15.2% in all except fox squirrels (0%). Leptospira phylogenomics and patterns of serologic reactivity suggest that mainland terrestrial wildlife, particularly mesocarnivores, could be the source of repeated observed introductions of Leptospira into local marine and island ecosystems. Overall, we found evidence of widespread Leptospira exposure in wildlife across Los Angeles and surrounding regions. This indicates exposure risk for humans and domestic animals and highlights that this pathogen can circulate endemically in many wildlife species even in densely populated urban areas.

Aim Our aim was to examine gracile capuchin (Cebus) and robust capuchin monkey (Sapajus) diversification, with a focus on recent Sapajus expansion within Amazonia. We wanted to reconstruct the biogeographical history of the clade using statistical methods that model lineages' occupation of different regions over time in order to evaluate recently proposed 'Out of Amazonia' and 'Reinvasion of Amazonia' hypotheses as alternative explanations for the extensive geographical overlap between reciprocally monophyletic gracile (Cebus) and robust (Sapajus) capuchin monkeys. Location Central and South America. Methods We reconstructed a time-calibrated molecular phylogeny for capuchins under Bayesian inference from three mitochondrial genes. We then categorized 12 capuchin clades across four Neotropical centres of endemism and reconstructed the biogeographical history of the capuchin radiation using six models implemented in 'BioGeoBEARS'. We performed a phylogeographical analysis for a robust capuchin clade that spans the Atlantic Forest, Cerrado, Caatinga and Amazonia. Results We find support for a late Miocene vicariant Cebus-Sapajus divergence and a Pleistocene Sapajus invasion of Amazonia from the Atlantic Forest. Our new analyses confirm Sapajus diversified first in the Atlantic Forest, with subsequent range expansion into widespread sympatry with Cebus in Amazonia, as well as multiple expansions into drier savanna-like habitats. We do not find mitochondrial molecular congruence with morphological species distinctions for Sapajus flavius, S. cay, S. macrocephalus, S. libidinosus and S. apella; instead, these five morphological types together form a single widespread clade (Bayesian posterior probability = 1) with geographical substructure and shared ancestry during the Pleistocene. Main conclusions Our results support vicariance dividing ancestral capuchin populations in Amazonia versus the Atlantic Forest, and a Pleistocene 'Amazonian invasion' by Sapajus to explain the present-day sympatry of Cebus and Sapajus.

The major histocompatibility complex (MHC) is an important gene complex contributing to adaptive immunity. Studies of platyrrhine MHC have focused on identifying experimental models of immune system function in the equivalent Human Leukocyte Antigen (HLA). These genes have thus been explored primarily in captive platyrrhine individuals from research colonies. However, investigations of standing MHC variation and evolution in wild populations are essential to understanding its role in immunity, sociality and ecology. Capuchins are a promising model group exhibiting the greatest habitat diversity, widest diet breadth and arguably the most social complexity among platyrrhines, together likely resulting in varied immunological challenges. We use high-throughput sequencing to characterize polymorphism in four Class II DR and DQ exons for the first time in seven capuchin species. We find evidence for at least three copies for DQ genes and at least five for DRB, with possible additional unrecovered diversity. Our data also reveal common genotypes that are inherited across our most widely sampled population, Cebus imitator in Sector Santa Rosa, Costa Rica. Notably, phylogenetic analyses reveal that platyrrhine DQA sequences form a monophyletic group to the exclusion of all Catarrhini sequences examined. This result is inconsistent with the trans -species hypothesis for MHC evolution across infraorders in Primates and provides further evidence for the independent origin of current MHC genetic diversity in Platyrrhini. Identical allele sharing across cebid species, and more rarely genera, however, does underscore the complexity of MHC gene evolution and the need for more comprehensive assessments of allelic diversity and genome structure.

Postings on social media on Twitter (now X), BioAnthropology News (Facebook), and other venues, as well as recent publications in prominent journals, show that primatologists, ecologists, and other researchers are questioning the terms “Old World” and “New World” due to their colonial implications and history. The terms are offensive if they result in erasing Indigenous voices and history, ignoring the fact that Indigenous peoples were in the Americas long before European colonization. Language use is not without context, but alternative terminology is not always obvious and available. In this perspective, we share opinions expressed by an international group of primatologists who considered questions about the use of these terms, whether primatologists should adjust language use, and how to move forward. The diversity of opinions provides insight into how conventional terms used in primatological research and conservation may impact our effectiveness in these domains.

The platyrrhine family Cebidae (capuchin and squirrel monkeys) exhibit among the largest primate encephalization quotients. Each cebid lineage is also characterized by notable lineage-specific traits, with capuchins showing striking similarities to Hominidae such as high sensorimotor intelligence with tool use, advanced cognitive abilities, and behavioral flexibility. Here, we take a comparative genomics approach, performing genome-wide tests for positive selection across five cebid branches, to gain insight into major periods of cebid adaptive evolution. We uncover candidate targets of selection across cebid evolutionary history that may underlie the emergence of lineage-specific traits. Our analyses highlight shifting and sustained selective pressures on genes related to brain development, longevity, reproduction, and morphology, including evidence for cumulative and diversifying neurobiological adaptations across cebid evolution. In addition to generating a high-quality reference genome assembly for robust capuchins, our results lend to a better understanding of the adaptive diversification of this distinctive primate clade.

Robust capuchin monkeys, Sapajus genus, are among the most phenotypically diverse and widespread groups of primates in South America, with one of the most confusing and often shifting taxonomies. We used a ddRADseq approach to generate genome-wide SNP markers for 171 individuals from all putative extant species of Sapajus to access their evolutionary history. Using maximum likelihood, multispecies coalescent phylogenetic inference, and a Bayes Factor method to test for alternative hypotheses of species delimitation, we inferred the phylogenetic history of the Sapajus radiation, evaluating the number of discrete species supported. Our results support the recognition of three species from the Atlantic Forest south of the São Francisco River, with these species being the first splits in the robust capuchin radiation. Our results were congruent in recovering the Pantanal and Amazonian Sapajus as structured into three monophyletic clades, though new morphological assessments are necessary, as the Amazonian clades do not agree with previous morphology-based taxonomic distributions. Phylogenetic reconstructions for Sapajus occurring in the Cerrado, Caatinga, and northeastern Atlantic Forest were less congruent with morphology-based phylogenetic reconstructions, as the bearded capuchin was recovered as a paraphyletic clade, with samples from the Caatinga biome being either a monophyletic clade or nested with the blond capuchin monkey.

Seasonal patterns of group fragmentation, including the size of subgroups and percentage of time spent in subgroups, may provide information on individual decision-making in response to resource distribution. Age-sex class composition of subgroup membership can offer insights into the social dynamics of the group as a whole. At most field sites, capuchins (Cebus spp.) form stable groups with no evidence of group fragmentation. Here I describe seasonal subgrouping patterns, including proportion of time spent in subgroups, subgroup size, age-sex membership, dyadic fidelity, stability of membership, and the effect of subgrouping on individual foraging efficiency, in a group of wild Cebus apella nigritus. From September 1996 to August 1997 the study group at the Estação Biológica de Caratinga, Brazil divided into 148 different subgroups, on 99 of 194 census days. In contrast to expectations for subgrouping patterns as a response to seasonal distribution of resources, the proportion of days spent in subgroups did not vary significantly by season. Subgroup composition was relatively fluid, with multimale multifemale subgroups the most common throughout the year. Unimale multifemale subgroups were restricted to the wet season; in contrast, all-male subgroups and unimale unifemale subgroups occurred in the dry season. For both males and females, low rank predicted membership in smaller subgroups. For males, but not females, subgrouping coincided with increased foraging efficiency, as measured by increased time spent ingesting food and decreased time spent traveling on days with subgrouping compared to days with the group in a cohesive unit.[PUBLICATION ABSTRACT]

The rich diversity of primate faces has interested naturalists for over a century. Researchers have long proposed that social behaviours have shaped the evolution of primate facial diversity. However, the primate face constitutes a unique structure where the diverse and potentially competing functions of communication, ecology and physiology intersect, and the major determinants of facial diversity remain poorly understood. Here, we provide the first evidence for an adaptive role of facial colour patterns and pigmentation within Neotropical primates. Consistent with the hypothesis that facial patterns function in communication and species recognition, we find that species living in smaller groups and in sympatry with a higher number of congener species have evolved more complex patterns of facial colour. The evolution of facial pigmentation and hair length is linked to ecological factors, and ecogeographical rules related to UV radiation and thermoregulation are met by some facial regions. Our results demonstrate the interaction of behavioural and ecological factors in shaping one of the most outstanding facial diversities of any mammalian lineage.