The evolution of primary sexual characters in animals

Alex Córdoba-Aguilar

Primary sexual traits, those structures and processes directly involved in reproduction, are some of the most diverse, specialized, and bizarre in the animal kingdom. Moreover, reproductive traits are often species-specific, suggesting that they evolved very rapidly. This diversity has recently attracted broader interest from evolutionary biologists, especially those interested in sexual selection and the evolution of reproductive strategies. Primary sexual characters were assumed to be the product of natural selection, exclusively. A recent alternative suggests that sexual selection explains much of the diversity of "primary" sexual characters. A third approach to the evolution of reproductive interactions after copulation or insemination has been to consider the process one of sexual conflict. That is, the reproductive processes of a species may reflect, as does the mating system,...