Parasites in sexual and asexual mollies ( Poecilia , Poeciliidae, Teleostei): a case for the Red Queen?

Abstract

The maintenance of sexual reproduction in the face of its supposed costs is a major paradox in evolutionary biology. The Red Queen hypothesis, which states that sex is an adaptation to fast-evolving parasites, is currently one of the most recognized explanations for the ubiquity of sex and predicts that asexual lineages should suffer from a higher parasite load if they coexist with closely related sexuals. We tested this prediction using four populations of the sexual fish species Poecilia latipinna and its asexual relative Poecilia formosa . Contrary to expectation, no differences in parasite load could be detected between the two species.