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Alouatta, phylogenetics, Brazil, multi-locus.



Howler monkeys (Alouatta) are the most widely distributed New World primates, ranging from southern Mexico to northern Argentina. They occur in tropical rain forests, flooded and gallery forests, and deciduous and semi-deciduous environments. Despite their importance as seed dispersers, howlers have also been known to be ecological indicators. Available phylogenetic hypotheses for this genus have used chromosomal characters, morphological characteristics, and a limited number of molecular markers and specimens. In spite of these analyses, branching patterns among howler species lineages conflict between studies or remain unresolved. Using 14 unlinked non-coding intergenic nuclear regions under both a concatenated Bayesian approach (MrBayes) and a coalescent-based species tree method (*BEAST). I perform a new phylogenetic study of Alouatta, including five of the seven South American species (A. caraya, A. belzebul, A. guariba, A. seniculus, A. sara) and the two recognized species from Mesoamerica (A. pigra, A. palliata). Contrary to previous studies, I find little to no support for a sister relationship between A. guariba (the only howler species endemic to the Atlantic Coastal Forest) and A. belzebul, irrespective of the method utilized. Instead, the Atlantic forest-based A. guariba is recovered as sister to the remaining South American species, with high support both in the Bayesian and the species tree. Relationships among the remaining South American howlers are not as clearly supported, but a sister-species relationship is recovered between A. sara and A. caraya. Although the phylogenetic relationships inferred through the methods utilized here differ from those proposed in previous studies, the divergence time estimation analyses recovered similar dates to other investigations. The age of the genus Alouatta was estimated at ca. 6.1 Mya (95% Highest Posterior Density, or HPD = 5.2 - 6.9 Mya). The Meso-American clade containing Alouatta pigra and A. palliata was dated back to ca. 1.3 Mya (HPD 0.9 – 1.9 Mya), while the South American taxa coalesce at a node dated to ca. 5.1 Mya (HPD 4.3 – 6.0 Mya). While this study advances our knowledge of evolutionary relationships in howler monkeys, several standing questions remain. Tackling them will require further taxonomic, geographic, and genomic sampling in Alouatta.



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