Browsing by Author "Wright, PC"

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Open Access
Estimating the population size of lemurs based on their mutualistic food trees
(Journal of Biogeography, 2018-11-01) Herrera, JP; Borgerson, C; Tongasoa, L; Andriamahazoarivosoa, P; Rasolofoniaina, BJR; Rakotondrafarasata, ER; Randrianasolo, JLRR; Johnson, SE; Wright, PC; Golden, CD
Aim: Species’ distributions and abundances are primarily determined by the suitability of environmental conditions, including climate and interactions with sympatric species, but also increasingly by human activities. Modelling tools can help in assessing the extinction risk of affected species. By combining species distribution modelling of abiotic and biotic niches with population size modelling, we estimated the abundance of 19 lemur taxa in three regions, especially focusing on 10 species that are considered Endangered or Critically Endangered. Location: Madagascar. Taxa: Lemurs (Primates) and angiosperm trees. Methods: We used climate data, field samples, and published occurrence data on trees to construct species distribution models (SDM) for lemur food tree species. We then inferred the SDMs for lemurs based on the probability of occurrence of their food trees as well as climate. Finally, we used tree SDMs, topography, distance to the forest edge, and field estimates of lemur population density to predict lemur abundance in general linear models. Results: The SDMs of lemur food trees were stronger predictors of the occurrence of lemurs than climate. The predicted probability of presence of food trees, slope, elevation, and distance from the forest edge were significant correlates of lemur density. We found that sixteen species had minimum estimated abundances greater than 10,000 individuals over >1,000km2. Three lemur species are especially threatened, with less than 2,500 individuals predicted for Cheirogaleus sibreei, and heavy hunting pressure for the relatively small populations of Indri indri and Hapalemur occidentalis. Main conclusions: Biotic interactors were important variables in SDMs for lemurs, allowing refined estimates of ranges and abundances. This paper provides an analytical workflow that can be applied to other taxonomic groups to substantiate estimates of species’ vulnerability to extinction.
Open Access
Morphometrics and testicle size of rain forest lemur species from southeastern Madagascar
(Journal of Human Evolution, 1992-01-01) Glander, KE; Wright, PC; Daniels, PS; Merenlender, AM
Six species of prosimians inhabiting the montane rain forest of the Ranomafana National Park located in southeastern Madagascar were captured, weighed, and measured during the months of May or June of 1987, 1988, and 1989. There were no significant differences in body weights and measurements between male and femaleEulemur rubriventer (red-bellied lemur) orEulemur fulvus rufus (red-fronted lemur). Adult femalePropithecus diadema edwardsi (Milne Edward's sifaka) were heavier than males but the difference was not significant. A fewAvahi laniger laniger (woolly lemur),Hapalemur aureus (golden bamboo lemur) andH. g. griseus (gentle bamboo lemur) also were captured and measured. Body weights of the same individual adultP. d. edwardsi changed over the three years, suggesting variation in food availability. Although there was no difference in body weight among adult males of two groups ofP. d. edwardsi, one male in each group had a testicular volume four times larger than that of other males, even though these measurements were taken five months after the breeding season. These data suggest that only one adult male mates in each group. Testicular size of the polygynousE. f. rufus males was significantly larger than that of the monogamousE. rubriventer. © 1992 Academic Press Limited.
Open Access
Sexual selection and canine dimorphism in New World monkeys.
(Am J Phys Anthropol, 1988-11) Kay, RF; Plavcan, JM; Glander, KE; Wright, PC
Social and ecological factors are important in shaping sexual dimorphism in Anthropoidea, but there is also a tendency for body-size dimorphism and canine dimorphism to increase with increased body size (Rensch's rule) (Rensch: Evolution Above the Species Level. London: Methuen, 1959.) Most ecologist interpret Rensch's rule to be a consequence of social and ecological selective factors that covary with body size, but recent claims have been advanced that dimorphism is principally a consequence of selection for increased body size alone. Here we assess the effects of body size, body-size dimorphism, and social structure on canine dimorphism among platyrrhine monkeys. Platyrrhine species examined are classified into four behavioral groups reflecting the intensity of intermale competition for access to females or to limiting resources. As canine dimorphism increases, so does the level of intermale competition. Those species with monogamous and polyandrous social structures have the lowest canine dimorphism, while those with dominance rank hierarchies of males have the most canine dimorphism. Species with fission-fusion social structures and transitory intermale breeding-season competition fall between these extremes. Among platyrrhines there is a significant positive correlation between body size and canine dimorphism However, within levels of competition, no significant correlation was found between the two. Also, with increased body size, body-size dimorphism tends to increase, and this correlation holds in some cases within competition levels. In an analysis of covariance, once the level of intermale competition is controlled for, neither molar size nor molar-size dimorphism accounts for a significant part of the variance in canine dimorphism. A similar analysis using body weight as a measure of size and dimorphism yields a less clear-cut picture: body weight contributes significantly to the model when the effects of the other factors are controlled. Finally, in a model using head and body length as a measure of size and dimorphism, all factors and the interactions between them are significant. We conclude that intermale competition among platyrrhine species is the most important factor explaining variations in canine dimorphism. The significant effects of size and size dimorphism in some models may be evidence that natural (as opposed to sexual) selection also plays a role in the evolution of increased canine dimorphism.