Cryptic Female Choice and Its Implications in the Scorpionfly Harpobittacus nigriceps

Abstract

Female choice is a poorly understood area of evolutionary biology. Mate choice theory and the generally greater control of the process of reproduction by females than by males imply that female choice is prevalent in organisms and that it may be subtle in its nature, occurring even after mating and at any time until the female's control of gametes or zygotes terminates. Female choice in the Australian scorpionfly Harpobittacus nigriceps, a species in which males provide females with a nuptial arthropod gift during mating, was studied in the field and laboratory. Female choice before mating occurs in H. nigriceps and there is considerable evidence of its occurrence during and after mating in this species. Females apparently choose during mating by controlling mating duration and thus the number of sperm received from different mates. Postmating choice in H. nigriceps appears to include a female's ability to regulate egg laying in relation to characteristics of her mate. Female choice during and after mating in H. nigriceps almost certainly leads to stronger sexual selection on males than premating choice. All forms of female choice in H. nigriceps would result in directional selection of the criteria important in choice (male body size and its correlate, ability to obtain large prey). Female choice on the basis of body size in H. nigriceps may enhance female fitness if body size is heritable: Large individuals obtain more matings (males) and are more fecund (females) than small individuals, and, in general, survival and size are positively related in both sexes. Fluctuating natural selection pressures on body size within generations may generate enough genetic variation in male body size to maintain adaptive female choice in H. nigriceps.