1 April 2009 Evolution of Sexual Size Dimorphisms in Emydid Turtles: Ecological Dimorphism, Rensch's Rule, and Sympatric Divergence
Patrick R. Stephens, John J. Wiens
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The origin of sexual size dimorphisms (SSD) has long been a central topic in evolutionary biology. However, there is little agreement as to which factors are most important in driving the evolution of SSD, and several hypotheses concerning SSD evolution have never been tested empirically. Emydid turtles include species with both male and female-biased SSD, and some emydids exhibit among the most extreme SSD in tetrapods. Here, we use a comparative phylogenetic approach in emydids to analyze the origins of SSD and test several hypotheses for the evolution of SSD, some for the first time. We test the Fairbairn-Preziosi hypothesis for the origin of Rensch's rule, and support it in lineages with male-biased SSD but not those with female-biased SSD. We also find support for the secondary ecological dimorphism hypothesis, which proposes that selection for ecological divergence between sexes exaggerates preexisting SSD. Finally, we find only equivocal support for the Bolnick-Doebeli hypothesis, which relates intersexual ecological divergence to interspecific ecological divergence. Our results also illustrate how global analyses of SSD may mislead in groups in which the factors that drive the evolution of SSD vary among clades.

© 2009 The Society for the Study of Evolution.
Patrick R. Stephens and John J. Wiens "Evolution of Sexual Size Dimorphisms in Emydid Turtles: Ecological Dimorphism, Rensch's Rule, and Sympatric Divergence," Evolution 63(4), 910-925, (1 April 2009). https://doi.org/10.1111/j.1558-5646.2008.00597.x
Received: 22 June 2008; Accepted: 1 November 2008; Published: 1 April 2009

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Comparative methods
sexual size dimorphism
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