Meeting Abstract

46.2  Wednesday, Jan. 5  Does the evolution of a sexually selected trait compromise sprint and endurance performance in Xiphophorus swordtails and their close relatives? OUFIERO, C.E.*; JUGO, K.; YAU, T.; CHAPPELL, M.A.; GARLAND, T.; Univ. of California, Riverside; Univ. of California, Riverside; Univ. of California, Riverside; Univ. of California, Riverside; Univ. of California, Riverside coufi001@student.ucr.edu

Sexual selection often results in the evolution of elaborate secondary characteristics. Some of these secondary characteristics are in the form of exaggerated morphological structures. Many such structures are under competing selection, with sexual selection favoring an increase in the trait; while natural selection limits the expression of the trait if it imposes a cost to the bearer in terms of other fitness components (e.g., survivorship). We examined the effect of the ‘sword’ exhibited by males among species of Xiphophorus on sprint speed and critical swimming speed. We measured ~280 males from 19 species of Xiphophorus and Priapella to determine if the evolution of a longer sword is associated with a reduction in these aspects of locomotor performance. However, sexually selected traits do not evolve in isolation from the rest of the organism, so we also included several potential ‘compensatory’ traits that may have evolved to offset the cost of the sword (including possibly increased caudal fin length, maximum oxygen consumption, heart mass, gill mass, and tail muscle citrate synthase activity). For all traits, we removed correlations with body size prior to phylogenetic multiple regression analyses. Residual sword length was not a significant negative predictor of either sprint speed or critical swimming speed, irrespective of whether potential compensatory traits were included in the statistical models. Therefore, longer swords do not appear to be costly with respect to these measures of locomotor performance. Supported by IOS-0709788.