Perspective: Indirect Mate Choice, Competition for Mates, and Coevolution of the Sexes

Abstract

Abstract.-When Darwin first proposed the possibility of sexual selection, he identified two mechanisms, male competition for mates and female choice of mates. Extending this classification, we distinguish two forms of mate choice, direct and indirect. This distinction clarifies the relationship between Darwin's two mechanisms and, furthermore, indicates that the potential scope for sexual selection is much wider than thus far realized. Direct mate choice, the focus of most research on sexual selection in recent decades, requires discrimination between attributes of individuals of the opposite sex. Indirect mate choice includes all other behavior or morphology that restricts an individual's set of potential mates. Possibilities for indirect mate choice include advertisement of fertility or copulation, evasive behavior, aggregation or synchronization with other individuals of the same sex, and preferences for mating in particular locations. In each of these cases, indirect mate choice sets the conditions for competition among individuals of the opposite sex and increases the chances of mating with a successful competitor. Like direct mate choice, indirect mate choice produces assortative mating. As a consequence, the genetic correlation between alleles affecting indirect choice and those affecting success in competition for mates can produce self-accelerating evolution of these complementary features of the sexes. The broad possibilities for indirect mate choice indicate that sexual selection has more pervasive influences on the coevolution of male and female characteristics than previously realized.Key words.-Darwin, male-male competition, mate choice, mating systems, sexual selection.Received September 18, 1995. Accepted September 21, 1995 Research has largely confirmed Darwin's (1859Darwin's ( , 1871 speculations about the influence of sexual selection on evolution. Although it required more than a century to settle many of the theoretical and empirical issues, most of the scope for sexual selection as described by Darwin is now widely accepted. Here we take the argument a step farther. By using recent clarifications of sexual selection and by introducing a new distinction, we show that sexual selection has ramifications for the evolution of sexual organisms that extend considerably beyond those originally imagined by Darwin and currently recognized.When introducing his theory of sexual selection, Darwin (1859) envisaged two distinct mechanisms. Sexual selection, he wrote, "depends ... on a struggle between the males for the possession of the females." As an alternative mechanism of sexual selection, he suggested that "female birds, by se-1 Corresponding Author. Present address:

Reproductive competition and fecal testosterone in wild male giant pandas (Ailuropoda melanoleuca)

“…Schaller et al (1985 and Pan et al (2001) reported that males occupy large home ranges that overlap several female and male home ranges, and that males engage in significant competition for females before and during each female's brief 3-day fertile period. Despite the clear role for intrasexual male competition, it is possible that female pandas exercise indirect choice (sensu Wiley and Poston 1996), where female behavior sets the stage for male-male competition. Female pandas advertise reproductive condition through scent beginning up to several weeks before the fertile period (Swaisgood et al 2000(Swaisgood et al , 2002(Swaisgood et al , 2004 and vocal signals (Charlton et al 2010), which may recruit males and incite competition, ensuring that the female mates with the best available male (Cox and Le Boeuf 1977).…”

Female mate choice based on territory quality in barn swallows

“…Among such species, there have been many studies on female mate choice for male phenotype, because this promotes intersexual selection (Andersson 1994). Female mate choice for territory characteristics should also facilitate sexual selection by promoting male-male competition and indirect mate choice (Wiley and Poston 1996). However, female mate choice based on territory quality is less well studied owing to the difficulty of measuring territory quality in species with all-purpose territories containing many resources that are difficult to quantify (e.g., vegetation type and density, perch site, food, and nest site; Searcy and Yasukawa 1995).…”

Indirect female choice mediated by sex pheromones in the hermit crab Pagurus filholi

“…Such cases are called indirect mate choice (Wiley and Poston 1996). Indirect mate choice produces assortative mating in the same fashion as in direct mate choice, and it is widely accepted that indirect mate choice and male coercive behavior coevolved (Wiley and Poston 1996). Yamanoi et al (2006) suggested a possibility of indirect mate choice in this species, in which, by delaying copulation, females may exploit male-male competition to choose dominant males.…”

“…So, an individual indirectly chooses its own mate by setting the conditions for competition. Such cases are called indirect mate choice (Wiley and Poston 1996). Indirect mate choice produces assortative mating in the same fashion as in direct mate choice, and it is widely accepted that indirect mate choice and male coercive behavior coevolved (Wiley and Poston 1996).…”

“…Female mate choices under male coercive behavior have been found in some species (Wiley and Poston 1996). A previous study has suggested that females in guarding pairs of this species increase male-male combat by delaying copulation (Yamanoi et al 2006).…”