Centre d'Ecologie Fonctionnelle et Evolutive, Montpellier, France.
Evolution. 2013 Oct;67(10):2861-75. doi: 10.1111/evo.12167. Epub 2013 Jun 17.
Inbreeding depression has become a central theme in evolutionary biology and is considered to be a driving force for the evolution of reproductive morphology, physiology, behavior, and mating systems. Despite the overwhelming body of empirical work on the reproductive consequences of inbreeding, relatively little is known on whether inbreeding depresses male and female fitness to the same extent. However, sex-specific inbreeding depression has been argued to affect the evolution of selfing rates in simultaneous hermaphrodites and provides a powerful approach to test whether selection is stronger in males than in females, which is predicted to be the consequence of sexual selection. We tested for sex-specific inbreeding depression in the simultaneously hermaphroditic freshwater snail Physa acuta by comparing the reproductive performance of both sex functions between selfed and outcrossed focal individuals under different levels of male-male competition. We found that inbreeding impaired both male and female reproductive success and that the magnitude of male inbreeding depression exceeded female inbreeding depression when the opportunity for sperm competition was highest. Our study provides the first evidence for sex-specific inbreeding depression in a hermaphroditic animal and highlights the importance of considering the level of male-male competition when assessing sex differences in inbreeding depression.
近亲繁殖衰退已成为进化生物学的一个核心主题，被认为是生殖形态、生理、行为和交配系统进化的驱动力。尽管有大量关于近亲繁殖生殖后果的实证研究，但对于近亲繁殖是否同样程度地降低雌雄配子的适合度，人们知之甚少。然而，有人认为，性别特异性的近亲繁殖衰退会影响同时雌雄同体生物的自交率的进化，并提供了一种强有力的方法来检验选择是否在雄性中比在雌性中更强，这被认为是性选择的结果。我们通过比较在不同程度的雄性间竞争下，自交和杂交焦点个体的两种性别功能的生殖表现，来检验同时雌雄同体的淡水蜗牛 Physa acuta 是否存在性别特异性的近亲繁殖衰退。我们发现，近亲繁殖会损害雌雄两性的生殖成功，并且当精子竞争的机会最高时，雄性近亲繁殖衰退的幅度超过了雌性近亲繁殖衰退。我们的研究首次为雌雄异体动物中的性别特异性近亲繁殖衰退提供了证据，并强调了在评估近亲繁殖衰退中的性别差异时，考虑雄性间竞争水平的重要性。
