title: Sexually selected skin colour is heritable and related to fecundity in a non-human primate.
abstract: Sexual selection promotes the prevalence of heritable traits that increase an individual's reproductive rate. Despite theoretically strong directional selection, sexually selected traits can show inter-individual variation. Here, we investigate whether red skin ornamentation, a rare example of a male mammalian trait involved in mate attraction, influences fecundity and is heritable in rhesus macaques (Macaca mulatta), and explore the mechanisms that are involved in maintaining trait variation. Interestingly, the trait is expressed by and is attractive to both sexes. We collected facial images of 266 free-ranging individuals and modelled skin redness and darkness to rhesus macaque vision. We used 20 years of genetic parentage data to calculate selection gradients on the trait and perform heritability analyses. Results show that males who were both darkly coloured and high-ranking enjoyed higher fecundity. Female skin redness was positively linked to fecundity, although it remains unclear whether this influences male selectiveness. Heritability explained 10-15% of the variation in redness and darkness, and up to 30% for skin darkness when sexes are considered separately, suggesting sex-influenced inheritance. Our results suggest that inter-individual variation is maintained through condition-dependence, with an added effect of balancing selection on male skin darkness, providing rare evidence for a mammalian trait selected through inter-sexual selection.
authors.affiliation: Center for the Study of Human Origins, Department of Anthropology, New York University, 25 Waverly Place, New York, NY 10003, USA constance.dubuc@nyu.edu.
authors.forename: Constance
authors.initials: C
authors.lastname: Dubuc
authors.affiliation: Center for the Study of Human Origins, Department of Anthropology, New York University, 25 Waverly Place, New York, NY 10003, USA.
authors.forename: Sandra
authors.initials: S
authors.lastname: Winters
authors.affiliation: Center for the Study of Human Origins, Department of Anthropology, New York University, 25 Waverly Place, New York, NY 10003, USA.
authors.forename: William L
authors.initials: WL
authors.lastname: Allen
authors.affiliation: Duke Institute for Brain Sciences and Center for Cognitive Neuroscience, Duke University, 450 Research Drive, Durham, NC 27708, USA.
authors.forename: Lauren J N
authors.initials: LJ
authors.lastname: Brent
authors.affiliation: Center for the Study of Human Origins, Department of Anthropology, New York University, 25 Waverly Place, New York, NY 10003, USA.
authors.forename: Julie
authors.initials: J
authors.lastname: Cascio
authors.affiliation: Institute for Mind and Biology, University of Chicago, Chicago, IL 60637, USA Department of Comparative Human Development, University of Chicago, Chicago, IL 60637, USA.
authors.forename: Dario
authors.initials: D
authors.lastname: Maestripieri
authors.affiliation: Cayo Santiago, Caribbean Primate Research Center, University of Puerto Rico, Medical Sciences Campus, PO Box 906, Punta Santiago, PR 00741, USA Junior Research Group of Primate Kin Selection, Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, Leipzig 04103, Germany.
authors.forename: Angelina V
authors.initials: AV
authors.lastname: Ruiz-Lambides
authors.affiliation: Junior Research Group of Primate Kin Selection, Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, Leipzig 04103, Germany Institute of Biology, Faculty of Bioscience, Pharmacy and Psychology, University of Leipzig, Talstrasse 33, Leipzig 04103, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Widdig
authors.affiliation: Center for the Study of Human Origins, Department of Anthropology, New York University, 25 Waverly Place, New York, NY 10003, USA.
authors.forename: James P
authors.initials: JP
authors.lastname: Higham
mesh_terms: D000818:Animals; D005260:Female; D005298:Fertility / Q000235:genetics*; D008253:Macaca mulatta / Q000235:genetics* / Q000523:psychology*; D008297:Male; D052586:Mating Preference, Animal; D010641:Phenotype; D010858:Pigmentation / Q000235:genetics*; D012727:Sex Characteristics
keywords: ornaments; quantitative genetics; selection gradient; sexual selection; signalling