title: The effects of ecology and evolutionary history on robust capuchin morphological diversity.
abstract: Recent molecular work has confirmed the long-standing morphological hypothesis that capuchins are comprised of two distinct clades, the gracile (untufted) capuchins (genus Cebus, Erxleben, 1777) and the robust (tufted) capuchins (genus Sapajus Kerr, 1792). In the past, the robust group was treated as a single, undifferentiated and cosmopolitan species, with data from all populations lumped together in morphological and ecological studies, obscuring morphological differences that might exist across this radiation. Genetic evidence suggests that the modern radiation of robust capuchins began diversifying ∼2.5 Ma, with significant subsequent geographic expansion into new habitat types. In this study we use a morphological sample of gracile and robust capuchin craniofacial and postcranial characters to examine how ecology and evolutionary history have contributed to morphological diversity within the robust capuchins. We predicted that if ecology is driving robust capuchin variation, three distinct robust morphotypes would be identified: (1) the Atlantic Forest species (Sapajus xanthosternos, S. robustus, and S. nigritus), (2) the Amazonian rainforest species (S. apella, S. cay and S. macrocephalus), and (3) the Cerrado-Caatinga species (S. libidinosus). Alternatively, if diversification time between species pairs predicts degree of morphological difference, we predicted that the recently diverged S. apella, S. macrocephalus, S. libidinosus, and S. cay would be morphologically comparable, with greater variation among the more ancient lineages of S. nigritus, S. xanthosternos, and S. robustus. Our analyses suggest that S. libidinosus has the most derived craniofacial and postcranial features, indicative of inhabiting a more terrestrial niche that includes a dependence on tool use for the extraction of imbedded foods. We also suggest that the cranial robusticity of S. macrocephalus and S. apella are indicative of recent competition with sympatric gracile capuchin species, resulting in character displacement.
authors.affiliation: Department of Anatomy, Kansas City University of Medicine and Biosciences, Kansas City, MO, USA. Electronic address: kwright@kcumb.edu.
authors.forename: Kristin A
authors.initials: KA
authors.lastname: Wright
authors.affiliation: Department of Anatomy, Kansas City University of Medicine and Biosciences, Kansas City, MO, USA.
authors.forename: Barth W
authors.initials: BW
authors.lastname: Wright
authors.affiliation: Department of Anthropology and Graduate School, Southern Illinois University, Carbondale, IL, USA.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Ford
authors.affiliation: Department of Psychology, University of Georgia, Athens, GA, USA.
authors.forename: Dorothy
authors.initials: D
authors.lastname: Fragaszy
authors.affiliation: Department of Experimental Psychology, Institute of Psychology, University of São Paulo, Brazil.
authors.forename: Patricia
authors.initials: P
authors.lastname: Izar
authors.affiliation: Department of Anthropology, Kent State University, Kent, OH, USA.
authors.forename: Marilyn
authors.initials: M
authors.lastname: Norconk
authors.affiliation: Department of Health Sciences, Central Michigan University, Mount Pleasant, MI, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Masterson
authors.affiliation: Seminole State College, Sanford, FL, USA.
authors.forename: David G
authors.initials: DG
authors.lastname: Hobbs
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California, Los Angeles, Los Angeles, CA, USA.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Alfaro
authors.affiliation: Institute for Society and Genetics, University of California, Los Angeles, Los Angeles, CA, USA; Department of Anthropology, University of California, Los Angeles, Los Angeles, CA, USA.
authors.forename: Jessica W
authors.initials: JW
authors.lastname: Lynch Alfaro
mesh_terms: D000818:Animals; D005075:Biological Evolution; D016646:Cebinae / Q000033:anatomy & histology / Q000145:classification*; D017753:Ecosystem; D005260:Female; D008297:Male; D010679:Philippines; D010802:Phylogeny; D025341:Principal Component Analysis; D017422:Sequence Analysis, DNA; D012886:Skull / Q000033:anatomy & histology; D013020:South America
keywords: Cebidae; Evolution; Morphological variation; Platyrrhini; Robust capuchin monkeys; Sapajus