title: Considering the Influence of Nonadaptive Evolution on Primate Color Vision.
abstract: Color vision in primates is variable across species, and it represents a rare trait in which the genetic mechanisms underlying phenotypic variation are fairly well-understood. Research on primate color vision has largely focused on adaptive explanations for observed variation, but it remains unclear why some species have trichromatic or polymorphic color vision while others are red-green color blind. Lemurs, in particular, are highly variable. While some species are polymorphic, many closely-related species are strictly dichromatic. We provide the first characterization of color vision in a wild population of red-bellied lemurs (Eulemur rubriventer, Ranomafana National Park, Madagascar) with a sample size (87 individuals; NX chromosomes = 134) large enough to detect even rare variants (0.95 probability of detection at ≥ 3% frequency). By sequencing exon 5 of the X-linked opsin gene we identified opsin spectral sensitivity based on known diagnostic sites and found this population to be dichromatic and monomorphic for a long wavelength allele. Apparent fixation of this long allele is in contrast to previously published accounts of Eulemur species, which exhibit either polymorphic color vision or only the medium wavelength opsin. This unexpected result may represent loss of color vision variation, which could occur through selective processes and/or genetic drift (e.g., genetic bottleneck). To indirectly assess the latter scenario, we genotyped 55 adult red-bellied lemurs at seven variable microsatellite loci and used heterozygosity excess and M-ratio tests to assess if this population may have experienced a recent genetic bottleneck. Results of heterozygosity excess but not M-ratio tests suggest a bottleneck might have occurred in this red-bellied lemur population. Therefore, while selection may also play a role, the unique color vision observed in this population might have been influenced by a recent genetic bottleneck. These results emphasize the need to consider adaptive and nonadaptive mechanisms of color vision evolution in primates.
authors.affiliation: Department of Anthropology, Center for the Advanced Study of Human Paleobiology, The George Washington University, Washington, District of Columbia, United States of America.|Interdepartmental Doctoral Program in Anthropological Sciences, Stony Brook University, Stony Brook, New York, United States of America.|Centre ValBio Research Station, Ranomafana, Fianarantsoa, Madagascar.
authors.forename: Rachel L
authors.initials: RL
authors.lastname: Jacobs
authors.affiliation: Department of Anthropology, Center for the Advanced Study of Human Paleobiology, The George Washington University, Washington, District of Columbia, United States of America.
authors.forename: Brenda J
authors.initials: BJ
authors.lastname: Bradley
mesh_terms: D000221:Adaptation, Ocular / Q000235:genetics*; D000818:Animals; D005075:Biological Evolution; D055253:Color Vision / Q000235:genetics*; D005145:Face; D005260:Female; D056426:Genetic Loci; D060005:Genotyping Techniques; D005843:Geography; D007900:Lemur / Q000235:genetics*; D008270:Madagascar; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics; D055355:Opsins / Q000378:metabolism; D010802:Phylogeny
chemical_list: D055355:Opsins