Novel opsin gene variation in large-bodied, diurnal lemurs.

Some primate populations include both trichromatic and dichromatic (red-green colour blind) individuals due to allelic variation at the X-linked opsin locus. This polymorphic trichromacy is well described in day-active New World monkeys. Less is known about colour vision in Malagasy lemurs, but, unlike New World monkeys, only some day-active lemurs are polymorphic, while others are dichromatic. The evolutionary pressures underlying these differences in lemurs are unknown, but aspects of species ecology, including variation in activity pattern, are hypothesized to play a role. Limited data on X-linked opsin variation in lemurs make such hypotheses difficult to evaluate. We provide the first detailed examination of X-linked opsin variation across a lemur clade (Indriidae). We sequenced the X-linked opsin in the most strictly diurnal and largest extant lemur, Indri indri, and nine species of smaller, generally diurnal indriids (Propithecus). Although nocturnal Avahi (sister taxon to Propithecus) lacks a polymorphism, at least eight species of diurnal indriids have two or more X-linked opsin alleles. Four rainforest-living taxa-I. indri and the three largest Propithecus species-have alleles not previously documented in lemurs. Moreover, we identified at least three opsin alleles in Indri with peak spectral sensitivities similar to some New World monkeys.

Does the primate pattern hold up? Testing the functional significance of infraorbital foramen size variation among marsupials.

OBJECTIVES: The relative size of the infraorbital foramen (IOF) has been used to infer the ecology of extinct primates for several decades. Primates have relatively smaller IOFs than most other mammals, which may result from the fact that they pre-process and manipulate food with their hands rather than their muzzles. In primates, relative IOF area co-varies with diet, where insectivores and folivores have relatively smaller IOFs than frugivores. We wanted to determine whether the observed patterns associated with IOF variation hold across other orders. MATERIALS AND METHODS: We examined how relative IOF area differs among marsupials occupying different ecological niches. Marsupials were chosen because they converge with primates in both ecology and morphology, but unlike primates, some marsupials approach and pre-process foods only with their muzzles. We measured IOF area and cranial lengths from 72 marsupial species, and behavioral feeding data were obtained from a subset of this sample (N = 20). RESULTS: Relative IOF area did not vary significantly between substrate preferences. However, relative IOF area differed significantly by diet category (P < 0.001). Species that specialize in feeding on non-grassy leaves have significantly smaller relative IOF areas than species which primarily feed on grasses, insects, vertebrates, or some combination thereof. Behavioral analyses support that folivorous marsupials approach and remove food with the hands more often than marsupials from other dietary groups. DISCUSSION: Results suggest that relatively small IOF area may reflect increased reliance on the hands while feeding, and that relative IOF size can be used as an indicator of feeding behavior.

Primate genotyping via high resolution melt analysis: rapid and reliable identification of color vision status in wild lemurs.

Analyses of genetic polymorphisms can aid our understanding of intra- and interspecific variation in primate sociality, ecology, and behavior. Studies of primate opsin genes are prime examples of this, as single nucleotide variants (SNVs) in the X-linked opsin gene underlie variation in color vision. For primate species with polymorphic trichromacy, genotyping opsin SNVs can generally indicate whether individual primates are red-green color-blind (denoted homozygous M or homozygous L) or have full trichromatic color vision (heterozygous ML). Given the potential influence of color vision on behavior and fitness, characterizing the color vision status of study subjects is becoming commonplace for many primate field projects. Such studies traditionally involve a multi-step sequencing-based method that can be costly and time-consuming. Here we present a new reliable, rapid, and relatively inexpensive method for characterizing color vision in primate populations using high resolution melt analysis (HRMA). Using lemurs as a case study, we characterized variation at exons 3 and/or 5 of the X-linked opsin gene for 87 individuals representing nine species. We scored opsin genotypes and color vision status using both traditional sequencing-based methods as well as our novel melting-curve based HRMA protocol. For each species, the melting curves of varying genotypes (homozygous M, homozygous L, heterozygous ML) differed in melting temperature and/or shape. Melting curves for each sample were consistent across replicates, and genotype-specific melting curves were consistent across DNA sources (blood vs. feces). We show that opsin genotypes can be quickly and reliably scored using HRMA once lab-specific reference curves have been developed based on known genotypes. Although the protocol presented here focuses on genotyping lemur opsin loci, we also consider the larger potential for applying this approach to various types of genetic studies of primate populations.