1Center for the Advanced Study of Human Paleobiology, Department of Anthropology, The George Washington University, 2Interdepartmental Doctoral Program in Anthropological Sciences, Stony Brook University, 3Centre ValBio Research Station, Madagascar, 4Department of Anthropology, University of Texas at Austin, 5Department of Anthropology, Washington University in St. Louis
April 14, 2016 2:00, A 602
Trichromatic color vision in primates is generally considered to be adaptive, and multiple hypotheses highlight its potential advantage for foraging on reddish food. Adaptive explanations accord well with the prevalence of routine or polymorphic trichromacy in diurnal haplorhines. In lemurs, polymorphic trichromacy occurs in some diurnal/cathemeral taxa, but others are strictly dichromatic. It is unknown what evolutionary mechanisms lead to differences in color vision, but variation in species’ foraging ecologies might play a role.
Eulemur rubriventer in Ranomafana National Park (RNP) is dichromatic with a long wavelength (L) opsin and may have lost polymorphic trichromacy, which is observed in at least one other Eulemur species. Using reflectance spectra of 40 plant species (72 plant parts) consumed by E. rubriventer in RNP, we quantified their chromaticities as perceived by trichromatic and dichromatic Eulemur phenotypes. Our results indicate that under day and dusk light conditions, red-green chromaticities (indistinguishable to dichromats) of many food items would be conspicuous to a trichromatic Eulemur, suggesting trichromacy may be advantageous during diurnal foraging. When blue-yellow and luminance contrasts were calculated for the two possible dichromatic Eulemur phenotypes (L opsin vs. medium-wavelength opsin), luminance contrasts were significantly greater for dichromats with the L opsin. E. rubriventer in RNP may use luminance cues during foraging, potentially leading to relaxed selection on or selection against trichromacy, as chromatic information may corrupt luminance vision. Fixation of the L opsin could represent directional selection and adaptation for maximizing luminance cues, which may be important to this cathemeral species during nocturnal foraging.
This research was funded by Stony Brook University, The Wenner-Gren Foundation, The Leakey Foundation, National Science Foundation (DDIG BCS 1232535), and the RW Primate Fund.