The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)


Ecological effects on sexual dimorphism: Sex-specific body mass response to climate variables in wild populations of eastern sifakas

ADAM D. GORDON1, STEIG E. JOHNSON2 and EDWARD E. LOUIS, JR3.

1Department of Anthropology, University at Albany - SUNY, 2Department of Anthropology, University of Calgary, 3Center for Conservation and Research, Omaha's Henry Doorly Zoo, Omaha, NE

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It has long been recognized that sexual dimorphism is influenced by factors other than sexual selection alone. One such potential factor is a differential response of male and female body size to resource availability due to the metabolic demands of pregnancy and lactation. If true, female body mass may vary more across populations in relation to environmental variables than male body mass. Lemurs are well-suited to investigations of this hypothesis in that (1) lemurs are endemic to an isolated land mass with wide climatic variability and (2) the limited dimorphism present within lemur species is not correlated with sexual selection.

Sex-specific body mass and locality data for 19 wild populations of eastern Propithecus were drawn from a database of observations from over 3500 wild lemurs accumulated since 1999 by the Center for Conservation and Research. Populations included in this study lived in the eastern humid forests of Madagascar from 12.8 to 21.3 degrees south in latitude, and at elevations from 200 to 1300 meters above sea level. Precipitation and temperature data for each population were estimated using the WorldClim global climate database. Male and female body size were both found to be significantly positively correlated with annual rainfall across populations at alpha = 0.05. Female regressions slopes were higher than male slopes, consistent with a greater response in female size to environmental variables, although the difference in slopes was not significant. Future work will use the CCR database to test this hypothesis across a broader collection of environments and taxa.

This study was funded in part by support from the University at Albany and Omaha’s Henry Doorly Zoo.

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