Reproductive mode and the genetic benefits of polyandry

Behavioural ecology is currently undergoing a paradigm shift, with the traditional concepts of the choosy, monogamous female and the coadapted gene complex increasingly giving way to the realization that sexual reproduction engenders conflicts, promotes polyandry, and thereby provides females with a cryptic arsenal of postcopulatory processes with which to safeguard their investment in large, costly eggs. As research focuses on reproduction from the female perspective, evidence is emerging that polyandry can provide genetic benefits that enhance female reproductive success. In this review, we propose that reproductive mode is a critically important factor influencing the type of genetic benefits that females gain by mating with more than one male. Among the hypotheses that propose genetic benefits to polyandry, there is a distinction between those that posit benefits from intrinsic (additive) effects of paternal genes in offspring, and those that propose a benefit resulting from defence against incompatibility. Polyandry to acquire superior paternal genes and polyandry as a defence against incompatibility are not mutually exclusive hypotheses. However, evidence from reproductive physiology, immunology and evolutionary conflict theory suggest that development of the embryo within the female makes polyandry for incompatibility avoidance far more important for viviparous females than for females that lay eggs. (C) 2001 The Association for the Study of Animal Behaviour.