Abstract
The handicap theory of sexual selection posits that male display traits that are favored in mate choice come at a significant cost to performance. We tested one facet of this hypothesis in the green swordtail (Xiphophorus helleri). In this species, the lower ray of male caudal fin is extended into a ‘sword’, which serves to attract potential mates. However, bearing a long sword may increase drag and thus compromise a male's ability to swim effectively. We tested escape performance in this species by eliciting C-start escape responses, an instinctive escape behavior, in males with various sword lengths. We then removed males' swords and retested escape performance. We found no relationship between escape performance and sword length and no effect of sword removal on escape performance. While having a large sword may attract a predator's attention, our results suggest that sword size does not compromise a male's escape performance.
Highlights
Males in many species have elaborate display traits that they use to attract females [1]
Well-established theories of sexual selection maintain that traits which are favorable in mate choice will be strongly selected for, even if natural selection does not favor these traits
Our results suggest that in Xiphophorus helleri the sword does not compromise male escape performance
Summary
Males in many species have elaborate display traits that they use to attract females [1]. Exaggerated visual ornaments may make males more conspicuous to females, while increasing their conspicuousness to eavesdropping predators [1,5,6,7]. In the barn swallow Hirundo rustica, males with elongated tail feathers are preferred by females but are less efficient at capturing prey [10]. In addition to increasing the likelihood of detection by predators or potential prey, exaggerated male display traits may inhibit a male’s ability to escape predators: the drag imposed by moving a large display trait through the medium—water or air—may significantly reduce escape velocity [11,12]
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