The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

Towards a theoretical framework for understanding the variation in sexually-selected traits among multimale-multifemale anthropoid primates


1Department of Anthropology, NYU, 2Reproductive Biology Unit, DPZ, 3CRC, University of Goettingen

Thursday 4:45-5:00, Ballroom B Add to calendar

Sexual selection theory explains the evolution of traits that increase reproductive rate. A variety of mechanisms may influence the evolution of sexually-selected traits in males, including contest competition, sperm competition, and female mate choice. However, it remains unclear whether and how such mechanisms interact to shape trait evolution. Anthropoid primates are an ideal model system for investigating these interactions because they display a great array of sexually-selected traits that are typically attributed to different sexual selection mechanisms, even among those subject to the same mating system: polygynandry. Here, we propose a framework aimed at explaining this variation using a socio-ecological approach. We explain the observed pattern based on variability in the degree of synchrony of female mating activity, which has previously been proposed to shape male-male competition for fertile females. In short, we predict that species facing high degree of synchrony exhibit traits associated with contest competition (e.g. sexual dimorphism in weaponry; signals of social status), while those facing low degree of synchrony exhibit traits associated with sperm competition (e.g. large testis size) and female mate choice (e.g. signals of quality). We further propose that the dynamic of male-male competition also shape the evolution of female signals. We predict that presence, precision and/or conspicuousness of signals of the probability of ovulation are more likely to evolve in context of low degree of synchrony where male dominance rank provides honest cue about their quality. These predictions will be illustrated with examples extracted from the literature.

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