Sexual selection and the evolution of extra-pair copulation: rules of the game from the females' point of view

V. Amrhein, Sexual selection and the evolution of extra-pair copulation: rules of the game from the females' point of view, J ORNITHOL, 140(4), 1999, pp. 431-441
Citations number
Categorie Soggetti
Animal Sciences
Journal title
ISSN journal
0021-8375 → ACNP
Year of publication
431 - 441
SICI code
In view of Darwin's fundamental thesis on sexual selection, which appeared in 1871, it is no longer a secret that a peacock can spread his tail becaus e the females want it that way. It is generally acknowledged that the peaco ck is polygamous; whichever male has the most attractive plumage wins the m ost females and therefore achieves the greatest reproductive success. It is due to selective breeding by the females, i.e. "female choice" that the ma les have become what they are today. In monogamous mating systems, however, the source of striking colouring in males could not be explained the same way until evidence for the common occurrence of "extra-pair copulation" bec ame more accepted. This mating behaviour offers an explanation of how certa in males, even in monogamous species, can produce more offspring than other s. Only in recent years was it recognised that it is often the females whic h play the active role in the initiation of extra-pair copulation. What fit ness gains can the females expect to achieve through this behaviour? This review commences with an introduction to fundamental theories of sexua l selection. Progressing from this, the current discussion of extra-pair co pulation (EPC) is reviewed. Conceivable fitness gains for the females, whic h may have resulted in the evolution of EPC, are summarised. A connection i s noted between the various possible fitness gains in their effect on the " total reproductive value" of the females. The necessity of considering all of these theories from a more general perspective, without having to dismis s any explanations from the outset, is made clear Gowaty's "constrained fem ale hypothesis" (1996) is one example in which this has been achieved. This hypothesis proposes that females can be obliged to engage in EPC in order to obtain any kind of extra fitness gain, since they are often constrained in their choice of a partner (e.g. by the males themselves). In conclusion, possible directions are suggested for the testing of these hypotheses in f ield studies; in future more emphasis should be put on intrinsic quality di fferences between the females while investigating their mating behaviour.