Group benefit associated with polymorphic trichromacy in a Malagasy primate (Propithecus verreauxi).

Rebecca J Lewis,Anthony Di Fiore,E Christopher Kirk,Deborah A Bolnick,Clara J Scarry,Carrie C Veilleux

doi:10.1038/srep38418

Rebecca J Lewis, Anthony Di Fiore + Show 4 more

Open Access

https://doi.org/10.1038/srep38418

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Journal: Scientific reports	Publication Date: Dec 2, 2016
Citations: 27	License type: CC BY 4.0

Affiliation: The University of Texas at Austin

Abstract

In some primate lineages, polymorphisms in the X-linked M/LWS opsin gene have produced intraspecific variation in color vision. In these species, heterozygous females exhibit trichromacy, while males and homozygous females exhibit dichromacy. The evolutionary persistence of these polymorphisms suggests that balancing selection maintains color vision variation, possibly through a ‘trichromat advantage’ in detecting yellow/orange/red foods against foliage. We identified genetic evidence of polymorphic trichromacy in a population of Verreaux’s sifaka (Propithecus verreauxi) at Kirindy Mitea National Park in Madagascar, and explored effects of color vision on reproductive success and feeding behavior using nine years of morphological, demographic, and feeding data. We found that trichromats and dichromats residing in social groups with trichromats exhibit higher body mass indices than individuals in dichromat-only groups. Additionally, individuals in a trichromat social group devoted significantly more time to fruit feeding and had longer fruit feeding bouts than individuals in dichromat-only groups. We hypothesize that, due to small, cohesive sifaka social groups, a trichromat advantage in detecting productive fruit patches during the energetically stressful dry season also benefits dichromats in a trichromat’s group. Our results offer the first support for the ‘mutual benefit of association’ hypothesis regarding the maintenance of polymorphic trichromacy in primates.

Highlights

Researchers have long noted that primates are unique among placental mammals in exhibiting trichromatic color vision[1,2]
We investigated the effects of both individual color vision phenotype and group color vision phenotype on three presumed correlates of reproductive success in Verreaux’s sifaka at Kirindy Mitea: body mass index (BMI) during the dry season, reproductive output, and infant survival to the first year
In the dry season (n = 440 feeding bouts, Table 2), we found a significant effect of group color vision phenotype on the length of time an individual fed in a single fruit tree (LRT: χ21 = 5.29, p = 0.021), but not individual phenotype (LRT: χ21 = 0.79, p = 0.375)

Summary

Introduction

Researchers have long noted that primates are unique among placental mammals in exhibiting trichromatic color vision[1,2]. While trichromat capuchins (Cebus capucinus) may be able to better detect ripe figs, feeding intake rates do not differ among color vision phenotypes, implying that dichromats achieve similar total intake using non-color-based cues[28]. Consistent with this finding, long-term demographic data for capuchins reveal no difference between trichromats and dichromats for any measure of reproductive success[29]. Field studies of capuchins suggest that dichromats are more efficient at capturing camouflaged exposed insect prey and spend less time visually foraging for insects than trichromats, while trichromats are more efficient at extracting embedded insects[15,31,32] These differences in foraging efficiency do not extend to cryptic and conspicuous fruit[31]. Some researchers have proposed that trichromacy may benefit group members through visual discovery of more productive food patches at greater distances, in species with small social groups or with subgrouping where all individuals would be able to exploit the patch[26,33]

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