Mate choice in males with one-shot genitalia: limited importance of female fecundity

Abstract

Male mate choice is expected in species in which future mating opportunities of males are strongly diminished after their first copulation and mate quality is variable unless the costs of choice exceed the benefits. Males of the spider Argiope bruennichi are mostly monogynous; they damage their paired one-shot genitalia during copulation and fall victim to sexual cannibalism. Even males that are not cannibalized can achieve a maximum of two matings. Such a high mating effort implies that a male’s reproductive success can be increased by selecting the best possible mate. Mate quality may depend on female mating status and/or fecundity. Males should be selected to prefer virgin females over mated ones since previously used female genital ducts can be blocked by genital mating plugs. Fecundity is a common approximation of female quality and in invertebrates is generally correlated with body size and mass. Argiope bruennichi females vary in body size and fecundity, providing a basis for male selectivity. By creating binary choice situations in field and laboratory experiments in which search costs were largely removed, we tested whether males show mate choice. There was weak evidence for a male preference based on female phenotype. However, virgin females were significantly preferred over mated females even if the virgin had a less fecund phenotype. We conclude that selective benefits of mating first with a female override potential benefits of choice based on female fecundity, leading to competition for virgin females.