Departmento Ecología Evolutiva, Museo Nacional de Ciencias Naturales (CSIC), C/José Gutiérrez Abascal 2, 28006 Madrid, Spain.
Section of Ecology, University of Turku, Turku 20014, Finland.
Biol Lett. 2019 Aug 30;15(8):20190360. doi: 10.1098/rsbl.2019.0360. Epub 2019 Aug 7.
There is no consensus yet on the reasons why females engage in extra-pair copulations (EPCs). In some species, females have been shown to accrue some indirect benefits, but these effects are not consistent across species and studies. The sexual conflict hypothesis posits that extra-pair paternity (EPP) is the result of strong selection for male pursuit of EPC without real benefits for females. In order to test this hypothesis, we experimentally reduced wing area (reversibly tying together some primary feathers), in a group of pied flycatcher females (Ficedula hypoleuca). The manipulation increases wing loading (body mass/wing area), which is negatively associated with flying ability, and thus with the capacity to escape from unwanted copulations. We compared the levels of EPP in this experimental group with those of a group of un-manipulated females. Experimental females almost doubled the proportion of extra-pair young (EPY) with respect to control females. In addition, more males sired EPY in experimental than in control broods containing EPY. These results suggest that in our study population, EPP could be partially a product of female capacity to avoid EPCs. We also discuss the alternative hypothesis that results might be due to an eventual reduction of female attractiveness.
目前对于雌性进行种间交配（EPC）的原因还没有达成共识。在一些物种中，雌性已经被证明获得了一些间接的好处，但这些影响在不同物种和研究中并不一致。性冲突假说认为，种间交配是由于雄性强烈追求 EPC 而没有给雌性带来真正的好处。为了验证这一假说，我们对一群白腰文鸟（Ficedula hypoleuca）雌性进行了翅膀面积的实验性减少（将一些初级飞羽绑在一起）。这种操作增加了翅膀负荷（体重/翅膀面积），这与飞行能力呈负相关，因此也与逃避不必要交配的能力呈负相关。我们将实验组和未受操作的对照组雌性的 EPP 水平进行了比较。实验组雌性的种间交配后代（EPY）比例几乎是对照组的两倍。此外，在实验组含有 EPY 的窝中，有更多的雄性成为 EPY 的父亲。这些结果表明，在我们的研究群体中，EPP 可能部分是雌性避免 EPC 的能力的产物。我们还讨论了另一种假设，即结果可能是由于雌性吸引力的最终降低所致。
