DISSERTATION RESEARCH: Comparative Analysis of the Costs of Sexually Selected Traits within Swordtails and Platyfish

University Of California-Riverside, Riverside CA

Investigators

Abstract

Theodore Garland, Jr. and Christopher E. Oufiero Proposal # 0709788 Comparative analysis of the costs of sexually selected traits within swordtails and platyfish. Through natural selection, organisms generally become better adapted to their environmental circumstances with each passing generation. However, some traits are difficult to explain as a result of natural selection. For example, the long and gaudy tails of male peacocks would seem likely to hinder their flying abilities and to attract the attention of predators. Moreover, such elaborate tails are probably expensive to grow and maintain, diverting scarce energetic resources away from other needs. Therefore, Charles Darwin proposed the theory of sexual selection, the idea that such traits as male peacock tails might evolve because they helped their bearers to obtain mates, even if they also compromised, to some extent, other things they had to do. This research will examine costs and potential compensatory mechanisms related to a well-described sexually selected trait, the "sword" exhibited by males in several species of swordtail and platyfish (genus Xiphophorus). The sword has the potential to reduce locomotor abilities through an increase in drag or physiological burden. Several locomotor performances will be examined, including sprint speed and swimming endurance. Additionally, potential compensatory traits, such as heart mass and maximum oxygen consumption, will be examined. When not taken into account, these traits may mask the negative effect of the sexually selected trait on locomotor performance. This research will significantly advance our understanding of the costs of sexual selection. It will be the first multi-species comparative study to examine both costs and possible compensatory mechanisms. It will also further elucidate the relations between structure and performance in a novel vertebrate system. This will enable biomedically oriented undergraduate assistants to gain a broader understanding of, and appreciation for, animal behavior and organismal biology, and how these integrate with anatomy and physiology.