Meeting Abstract

81.5  Friday, Jan. 6  Trade-offs and compensatory traits: bite force and sprint speed pose conflicting demands on the design of male geckos (Hemidactylus frenatus) CAMERON, SF*; WYNN, ML; WILSON, RS; Univ. of Queensland, Australia

The evolution of exaggerated ornaments and armaments is driven by the benefits accrued to reproductive success and by the costs imposed on viability. Thus, when traits are required to perform multiple functions that are important to both reproduction and viability, trade-offs can result in a compromised phenotype. One of the more intuitive viability costs that can result from the possession of exaggerated male traits is increased predation pressure due to reduced locomotor capacity. Despite only mixed empirical support for such locomotor costs, recent studies suggest these costs may be masked as a result of the evolution of compensatory mechanisms that offset any detrimental effects. In this study, we provide a comprehensive assessment of the importance of potential locomotor costs that are associated with improved male-male competitive ability by simultaneously testing for locomotor trade-offs and compensatory mechanisms. For males of the Asian house gecko (Hemidactylus frenatus), both fighting capacity and escape performance are likely to place conflicting demands on an individual’s phenotype. Males that are highly territorial and aggressive are more likely to require greater investment in jaw size/strength in order to compete with rival males, which may affect the overall manoeuvrability and speed of an individual. We found that males, exhibited a trade-off between maximum sprint speed and bite-force; where males that exhibited a larger bite force capacity had a reduced sprint speed. In addition, this performance trade-off was amplified for male H. frenatus with larger heads when sprinting up inclines. Larger males with stronger bites showed greater prey-capture and fighting capacity, but the poorer sprint speed. However, we found little evidence for compensatory mechanisms that off-set the functional trade-off between bite force and sprint speed.