Female preference for swords in Xiphophorus helleri reflects a bias for large apparent size

• DOI: 10.1073/pnas.95.8.4431
• Publication Date: 2002-07-26T14:40:11Z
• Authors: Gil G. Rosenthal; Christopher S. Evans
• Keywords: Xiphophorus; SWORD; Poeciliidae; Cyprinodontiformes

Swordtail fish (Poeciliidae: genus Xiphophorus ) are a paradigmatic case of sexual selection by sensory exploitation. Female preference for males with conspicuous “sword” ornament is ancestral, suggesting that male morphology has evolved in response to preexisting bias. The perceptual mechanisms underlying female mate choice have not been identified, complicating efforts understand the pressures acting on design. We consider two alternative models receiver behavior, each consistent previous results. Females could respond either specific characteristics sword or more general cues, such as apparent size potential mates. showed swordtails series computer-altered video sequences depicting courting male. Footage an intact was preferred strongly otherwise identical which portions had deleted selectively, but disembodied less attractive than There no difference between responses isolated and swordless comparable length, homogenous background. sworded abolished enlarging image compensate reduction length caused removing ornament. This pattern results being mediated large rather characters. Similar processes may account evolution exaggerated traits other systems.