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.

Ecogeographic size variations in Sifakas: a test of the resource seasonality and resource quality hypotheses.

Ecogeographic size variations have been documented in some but not all sifakas. Few morphometric or body weight data have been available for two critically endangered subspecies of diademed sifakas: Perrier's sifakas (Propithecus diadema perrieri) and silky sifakas (Propithecus diadema candidus). The objectives of our study were to determine size variations in sifakas and if these variations are related to resource quality and/or resource seasonality. P. d. perrieri and P. d. candidus were captured, weighed, and measured in northern Madagascar. Body weights and morphometrics were compared with other subspecies of diademed sifakas and indris (Indri indri). Differences in body weights and morphometrics between taxa are particularly pronounced for P. d. perrieri compared to P. d. diadema, P. d. edwardsi, and I. indri. Most morphometrics varied in comparisons between P. d. candidus and the other Indriidae (P. d. diadema, P. d. edwardsi, and I. indri). Average body size in sifakas is positively correlated with annual rainfall and negatively correlated with length of dry season. Sifaka body size is not correlated with protein-to-fiber ratios. Thus, size variations in sifakas are related to resource seasonality rather than resource quality. The relationships between the temporal availability of food resources and sifaka body size reflect complex and regionally varying causalities. Detailed, longitudinal information on the ecological factors underlying food selection and nutrient requirements in sifakas are needed to determine the relationship between ecogeographic variables and body size in sifakas.

Dietary patterns in Perrier's sifakas (Propithecus diadema perrieri): a preliminary study.

Some lemur species range into only one habitat type, whereas others range into a variety of habitats. Because plant community structure can differ between habitats, dietary patterns may vary for conspecific groups of primates that range into more than one type of habitat. The goal of our study was to determine how habitat variation influences dietary patterns in Perrier's sifakas (Propithecus diadema perrieri) that range into both dry and riparian forests in northern Madagascar. We collected 542 hr of data on the behavior and diet of two groups of P.d. perrieri from 7 June to 4 August 1998 at Camp Antobiratsy in Analamera Special Reserve, Madagascar. We computed indices of dietary diversity for each group and dietary/plant species similarity between groups. P.d. perrieri in group 1 fed predominantly in dry forest (72.7% of feeding records, n=660), whereas those in group 2 fed most often in riparian forest (73.7% of feeding records, n=666). The index of dietary similarity (0.986) was significantly higher than the index of plant species similarity (0.767). Although the P.d. perrieri in the two study groups fed predominantly in different forest habitats, they ate similar food items in very comparable proportions (but not from the same plant species). However, based on habitat availability measures, neither group fed where they were expected to feed.