Hotzy Cosima, Arnqvist Göran
Evolutionary Biology Centre, Department of Ecology and Evolution, Animal Ecology, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden.
Curr Biol. 2009 Mar 10;19(5):404-7. doi: 10.1016/j.cub.2009.01.045. Epub 2009 Feb 19.
One of the most enigmatic observations in evolutionary biology is the evolution of morphological or physiological traits in one sex that physically injure members of the other sex. Such traits occur in a wide range of taxa and range from toxic ejaculate substances to genital or external spines that wound females during copulation. Current hypotheses for the adaptive evolution of such injurious traits rest entirely on the assumption that they are beneficial to their bearer by aiding in reproductive competition. Here, we assess this key assumption in seed beetles where genital spines in males physically injure females. We demonstrate that male spine length is positively correlated with harm to females during mating but also that males with longer spines are more successful in sperm competition. This is the first complete support for the proposal that sexual selection by sperm competition can favor morphological traits in males that inflict injury upon females. However, our results suggest that harm to females is a pleiotropic by-product, such that genital spines in males elevate success in sperm competition by means other than by causing harm.
进化生物学中最神秘的现象之一是，某一性别的形态或生理特征发生进化，却会对另一性别的成员造成身体伤害。这类特征在广泛的分类群中都有出现，从有毒的射精物质到在交配时会弄伤雌性的生殖器或外部棘刺不等。目前关于此类有害特征适应性进化的假说完全基于这样一种假设，即它们通过助力生殖竞争对其携带者有益。在此，我们在豆象中评估这一关键假设，在豆象中雄性生殖器上的棘刺会对雌性造成身体伤害。我们证明，雄性棘刺长度与交配时对雌性的伤害呈正相关，但同时，棘刺较长的雄性在精子竞争中更成功。这是对精子竞争中的性选择会青睐雄性中对雌性造成伤害的形态特征这一观点的首次全面支持。然而，我们的结果表明，对雌性的伤害是一种多效性副产物，以至于雄性生殖器棘刺通过造成伤害以外的其他方式提高了精子竞争的成功率。
