The study finds that bite-force performance was a strong predictor of reproductive success. However, no size measure was correlated with any estimate of mating success or with potential reproductive output. These results counter the conventional wisdom that bigger is always better, and they support the hypothesis that weapon performance, which is likely to directly influence fight outcomes, has far stronger effects on fitness than size. The strong influence of weapon performance on reproductive success suggests that selection acts on weapon performance, which in turn drives the evolution of weapon morphology. As such, the use of morphology as a proxy for performance and its presumed extensions to fitness should be based, whenever possible, on empirical morphologyperformance relationships.
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A. Kristopher Lappin (Northern Arizona University) and Jerry F. Husak (Oklahoma State University), "Weapon Performance, Not Size, Determines Mating Success and Potential Reproductive Output in the Collared Lizard (Crotaphytus collaris)" 166:3 September 2005.