title: Highly polymorphic colour vision in a New World monkey with red facial skin, the bald uakari (Cacajao calvus).
abstract: Colour vision is highly variable in New World monkeys (NWMs). Evidence for the adaptive basis of colour vision in this group has largely centred on environmental features such as foraging benefits for differently coloured foods or predator detection, whereas selection on colour vision for sociosexual communication is an alternative hypothesis that has received little attention. The colour vision of uakaris (Cacajao) is of particular interest because these monkeys have the most dramatic red facial skin of any primate, as well as a unique fission/fusion social system and a specialist diet of seeds. Here, we investigate colour vision in a wild population of the bald uakari,C. calvus, by genotyping the X-linked opsin locus. We document the presence of a polymorphic colour vision system with an unprecedented number of functional alleles (six), including a novel allele with a predicted maximum spectral sensitivity of 555 nm. This supports the presence of strong balancing selection on different alleles at this locus. We consider different hypotheses to explain this selection. One possibility is that trichromacy functions in sexual selection, enabling females to choose high-quality males on the basis of red facial coloration. In support of this, there is some evidence that health affects facial coloration in uakaris, as well as a high prevalence of blood-borne parasitism in wild uakari populations. Alternatively, the low proportion of heterozygous female trichromats in the population may indicate selection on different dichromatic phenotypes, which might be related to cryptic food coloration. We have uncovered unexpected diversity in the last major lineage of NWMs to be assayed for colour vision, which will provide an interesting system to dissect adaptation of polymorphic trichromacy.
authors.affiliation: Programa de Pós-Graduação em Genética e Biologia Molecular, Universidade Federal do Rio Grande do Sul, Avenida Bento Gonçalves 9500, Porto Alegre, Rio Grande do Sul 91501-970, Brazil.
authors.forename: Josmael
authors.initials: J
authors.lastname: Corso
authors.affiliation: Behavioral Ecology Division, San Diego Zoo Institute for Conservation Research, 15600 San Pasqual Valley Road, Escondido, CA 92027-7000, USA Behavioral Ecology and Sociobiology Unit, German Primate Center, Leibniz Institute for Primate Research, Kellnerweg 4, Göttingen 37077, Germany.
authors.forename: Mark
authors.identifier: http://orcid.org/0000-0001-5236-3477
authors.initials: M
authors.lastname: Bowler
authors.affiliation: Behavioral Ecology and Sociobiology Unit, German Primate Center, Leibniz Institute for Primate Research, Kellnerweg 4, Göttingen 37077, Germany.
authors.forename: Eckhard W
authors.identifier: http://orcid.org/0000-0002-4259-8018
authors.initials: EW
authors.lastname: Heymann
authors.affiliation: Gene Bank of Primates and Primate Genetics Laboratory, German Primate Center, Leibniz Institute for Primate Research, Kellnerweg 4, Göttingen 37077, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Roos
authors.affiliation: Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK nim21@cam.ac.uk.
authors.forename: Nicholas I
authors.identifier: http://orcid.org/0000-0002-5545-1517
authors.initials: NI
authors.lastname: Mundy
mesh_terms: D000818:Animals; D055253:Color Vision; D005145:Face; D005260:Female; D008297:Male; D053820:Pitheciidae / Q000235:genetics / Q000502:physiology*; D017299:Rod Opsins / Q000235:genetics*; D017422:Sequence Analysis, DNA; D012867:Skin
chemical_list: D017299:Rod Opsins
keywords: cacajao; colour vision; sexual selection; trichromacy