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Coppery titi monkeys (Plecturocebus cupreus) are an important non-human primate model for studying neurobiology and social behavior, in part owing to their relatively unusual combination of social monogamy and paternal care. Despite this importance, relatively little is known regarding the underlying population genomics of this platyrrhine. This study presents high-coverage, whole-genome sequencing data from 26 individuals which, combined with a highly accurate multi-algorithm ensemble approach, was used to characterize the first map of structural variation in the species. This novel genomic resource includes over 13,000 structural variants, with the majority (>90%) being copy number variants. While many of these were found to be located in intergenic regions, several affected genes associated with disease, including an inversion predicted to impact a pathway implicated in early-onset Parkinson's disease. Furthermore, utilizing parent-offspring trios included within this study, the de novo structural variant rate was estimated to be one in every 1.5 births, similar to that reported in rhesus macaques but considerably higher than that observed in large human cohorts, as may be expected from underlying differences in life history traits amongst these species. Taken together, these insights into the structural variant landscape ofP. cupreuswill not only improve their utility as a behavioral model system, but will also contribute to our general understanding of the role of structural variation in both the evolution of the primate clade and disease-outcomes. 

ABSTRACT Although recent advances in genomics have enabled the high-resolution study of whole genomes, our understanding of one of the key evolutionary processes, mutation, still remains limited. In primates specifically, studies have largely focused on humans and their closest evolutionary relatives, the great apes, as well as a handful of species of biomedical or conservation interest. Yet, as biological variation in mutation rates has been shown to vary across genomic regions, individuals, and species, a greater understanding of the underlying evolutionary dynamics at play will ultimately be illuminated by not only additional sampling across the Order, but also by a greater depth of sampling within-species. To address these needs, we here present the first population-scale genomic resources for a platyrrhine of considerable biomedical interest for both social behavior and neurobiology, the coppery titi monkey (Plecturocebus cupreus). Deep whole-genome sequencing of 15 parent-offspring trios, together with a computationalde novomutation detection pipeline based on pan-genome graphs, has provided a detailed picture of the sex-averaged mutation rate — 0.63 × 10^-8(95% CI: 0.43 × 10^-8– 0.90 × 10^-8) per site per generation — as well as the effects of both sex and parental age on underlying rates, demonstrating a significant paternal age effect. Coppery titi monkey males exhibit long reproductive lifespans, afforded by long-term pair bonding in the species’ monogamous mating system, and our results have demonstrated that individuals reproducing later in life exhibit one of the strongest male mutation biases observed in any non-human primate studied to date. Taken together, this study thus provides an important piece of the puzzle for better comprehending the mutational landscape across primates. 

ABSTRACT Along with germline mutations, meiotic recombination plays a fundamental role in shaping genetic diversity and thus directly influences a species’ potential adaptive response to environmental change, amongst other features. Despite the recombination landscape being of central importance for a variety of questions in molecular evolution, the genome-wide distribution and frequency of recombination remains to be elucidated in many non-human primate species. Utilizing novel high-coverage genomic data from three multi-sibling families, we here provide the first estimates of the rates and patterns of crossover and non-crossover recombination in coppery titi monkeys (Plecturocebus cupreus) — a socially monogamous, pair-bonded primate that serves as an important model in behavioral research. Consistent with haplorrhines, crossover and non-crossover recombination in this platyrrhine are frequently localized at PRDM9-mediated hotspots, characterized by a 15-mer binding motif with substantial similarities to the degenerate 13-mer motif found in humans. The sex-averaged crossover rate in coppery titi monkeys is comparable with those of other primates; however, no significant difference in recombination rates was observed between the sexes, despite a pronounced maternal age effect in the species. Similarities also exist with regards to the sex-specific genomic distribution of non-crossover events, though the minimal conversion tract lengths of extended events was observed to be considerably longer in maternally-inherited non-crossovers. Taken together, these similarities and differences in the recombination landscape relative to other primates highlight the importance of incorporating species-specific rates and patterns in evolutionary models, and the resources provided here will thus serve to aid future studies in this important primate model system. 

Aggression and its neurochemical modulators are typically studied in males, leaving the mechanisms of female competitive aggression or dominance largely unexplored. To better understand how competitive aggression is regulated in the primate brain, we used receptor autoradiography to compare the neural distributions of oxytocin and vasopressin receptors in male and female members of female-dominant versus egalitarian/codominant species within theEulemurgenus, wherein dominance structure is a reliable proxy of aggression in both sexes. We found that oxytocin receptor binding in the central amygdala (CeA) was predicted by dominance structure, with the members of three codominant species showing more oxytocin receptor binding in this region than their peers in four female-dominant species. Thus, both sexes in female-dominantEulemurshow a pattern consistent with the regulation of aggression in male rodents. We suggest that derived pacifism inEulemurstems from selective suppression of ancestral female aggression over evolutionary time via a mechanism of increased oxytocin receptor binding in the CeA, rather than from augmented male aggression. This interpretation implies fitness costs to female aggression and/or benefits to its inhibition. These data establishEulemuras a robust model for examining neural correlates of male and female competitive aggression, potentially providing novel insights into female dominance. 

Abstract Despite being an important biomedical model species for social behavior, the natural population history of the coppery titi monkey (Plecturocebus cupreus) remains largely uncharacterized, in part due to the scarcity of genomic resources available for the species. Apart from the inherent interest in the demographic dynamics of this abundant platyrrhine native to the Amazon forest of Brazil and Peru, this quantification will also serve as a central component of future genotype-to-phenotype studies, given the ability of historical population size change and structure to generate genetic associations. In this study, we deep-sequenced the genomes of six unrelated individuals and inferred a baseline demographic model based on observed levels and patterns of variation in the non-coding regions of the genome. In characterizing these demographic dynamics, we found that estimated population size changes correspond well to previously described speciation times as well as to large-scale climatic changes relating to glaciation patterns. 

The coppery titi monkey (Plecturocebus cupreus) is an emerging nonhuman primate model system for behavioral and neurobiological research. At the same time, the almost entire absence of genomic resources for the species has hampered insights into the genetic underpinnings of the phenotypic traits of interest. To facilitate future genotype-to-phenotype studies, we here present a high-quality, fully annotated de novo genome assembly for the species with chromosome-length scaffolds spanning the autosomes and chromosome X (scaffold N50 = 130.8 Mb), constructed using data obtained from several orthologous short- and long-read sequencing and scaffolding techniques. With a base-level accuracy of ∼99.99% in chromosome-length scaffolds as well as benchmarking universal single-copy ortholog and k-mer completeness scores of >99.0% and 95.1% at the genome level, this assembly represents one of the most complete Pitheciidae genomes to date, making it an invaluable resource for comparative evolutionary genomics research to improve our understanding of lineage-specific changes underlying adaptive traits as well as deleterious mutations associated with disease. 

ABSTRACT Despite being a primate of considerable biomedical interest, particularly as a model for social behavior and neurobiology, the evolutionary processes shaping genetic variation in the coppery titi monkey (Plecturocebus cupreus) remain largely uncharacterized. Utilizing divergence and polymorphism data together with a recently published high-quality, annotated genome, we here infer the first fine-scale maps of mutation and recombination rates in this platyrrhine. We find a mean genome-wide mutation rate of between 0.93 × 10^-8and 1.61 × 10^-8per site per generation and a mean genome-wide recombination rate of 0.975 cM/Mb, in line with fine-scale rates estimated in other primates. In addition to providing novel biological insights into the mutation and recombination rates in this emerging model species for behavioral research, these fine-scale maps also improve our understanding of how the processes of mutation and recombination shape genetic variation in the coppery titi monkey genome, and their incorporation into evolutionary models will be a necessary aspect of future downstream inference of other evolutionary processes required to elucidate the genetic factors underlying the phenotypic traits studied in this species. 

Abstract Contemporary theory that emphasizes the roles of oxytocin and vasopressin in mammalian sociality has been shaped by seminal vole research that revealed interspecific variation in neuroendocrine circuitry by mating system. However, substantial challenges exist in interpreting and translating these rodent findings to other mammalian groups, including humans, making research on nonhuman primates crucial. Both monogamous and non-monogamous species exist within Eulemur , a genus of strepsirrhine primate, offering a rare opportunity to broaden a comparative perspective on oxytocin and vasopressin neurocircuitry with increased evolutionary relevance to humans. We performed oxytocin and arginine vasopressin 1a receptor autoradiography on 12 Eulemur brains from seven closely related species to (1) characterize receptor distributions across the genus, and (2) examine differences between monogamous and non-monogamous species in regions part of putative “pair-bonding circuits”. We find some binding patterns across Eulemur reminiscent of olfactory-guided rodents, but others congruent with more visually oriented anthropoids, consistent with lemurs occupying an ‘intermediary’ evolutionary niche between haplorhine primates and other mammalian groups. We find little evidence of a “pair-bonding circuit” in Eulemur akin to those proposed in previous rodent or primate research. Mapping neuropeptide receptors in these nontraditional species questions existing assumptions and informs proposed evolutionary explanations about the biological bases of monogamy. 

ABSTRACT The study of the mammalian microbiome serves as a critical tool for understanding host-microbial diversity and coevolution and the impact of bacterial communities on host health. While studies of specific microbial systems (e.g., in the human gut) have rapidly increased, large knowledge gaps remain, hindering our understanding of the determinants and levels of variation in microbiomes across multiple body sites and host species. Here, we compare microbiome community compositions from eight distinct body sites among 17 phylogenetically diverse species of nonhuman primates (NHPs), representing the largest comparative study of microbial diversity across primate host species and body sites. Analysis of 898 samples predominantly acquired in the wild demonstrated that oral microbiomes were unique in their clustering, with distinctive divergence from all other body site microbiomes. In contrast, all other body site microbiomes clustered principally by host species and differentiated by body site within host species. These results highlight two key findings: (i) the oral microbiome is unique compared to all other body site microbiomes and conserved among diverse nonhuman primates, despite their considerable dietary and phylogenetic differences, and (ii) assessments of the determinants of host-microbial diversity are relative to the level of the comparison (i.e., intra-/inter-body site, -host species, and -individual), emphasizing the need for broader comparative microbial analyses across diverse hosts to further elucidate host-microbial dynamics, evolutionary and biological patterns of variation, and implications for human-microbial coevolution. IMPORTANCE The microbiome is critical to host health and disease, but much remains unknown about the determinants, levels, and evolution of host-microbial diversity. The relationship between hosts and their associated microbes is complex. Most studies to date have focused on the gut microbiome; however, large gaps remain in our understanding of host-microbial diversity, coevolution, and levels of variation in microbiomes across multiple body sites and host species. To better understand the patterns of variation and evolutionary context of host-microbial communities, we conducted one of the largest comparative studies to date, which indicated that the oral microbiome was distinct from the microbiomes of all other body sites and convergent across host species, suggesting conserved niche specialization within the Primates order. We also show the importance of host species differences in shaping the microbiome within specific body sites. This large, comparative study contributes valuable information on key patterns of variation among hosts and body sites, with implications for understanding host-microbial dynamics and human-microbial coevolution.