What Is Indirect Cryptic Female Choice? Theoretical Considerations and an Example from a Promiscuous Earwig

Abstract

Cryptic female choice (CFC) does not necessarily involve discriminative responses in the female nervous system to sperm from multiple mates. Even without any active sperm-choice mechanisms, polyandrous females can gain genetic benefits by having an arena in which genetically superior sperm are "automatically" sorted. In this chapter, possible mechanisms in this CFC category, termed "indirect CFC," are reviewed. A simple theoretical model is developed to examine the hypothesis that females obtain genetic benefits by allowing only partial displacement of stored sperm by subsequent mates. The model predicts that such restricted sperm displacement automatically grants genetic benefits when genetically superior males copulate more times per encounter with the female than less fit males. The promiscuous earwig species, Euborellia plebeja, provides an empirical example of this type of indirect CFC. The elongated female sperm-storage organs allow only partial removal and displacement of stored sperm by shorter male genitalia, resulting in a 20 % gain in paternity per mating. In staged mating trials, large males dominated male-male competition for burrows housing females, resulting in a significant increase in paternity by repeated matings with the same female. A numerical simulation based on this mating pattern showed that restricted sperm displacement (~20 % per mating) is optimal for females to accumulate sperm from larger males. Given that male body size is heritable, females were estimated to gain a 1.4 % increase in their sons' mating success as a genetic benefit. Advantages and disadvantages of indirect CFC are discussed and compared with precopulatory mate choice and direct CFC.

Earwigs from Brazilian caves, with notes on the taxonomic and nomenclatural problems of the Dermaptera (Insecta)

“…directly insert the elongated virga into the female spermatheca during copulation (Kamimura 2000; Lieshout and Elgar 2011). Elongation of the virga (and the genitalia as a whole, which functions as the virgal sheath when in repose) is considered an adaptation for removal of rival sperm from the female spermatheca, which is usually longer than the virga (Kamimura 2000, 2005, 2013, 2015; Lieshout and Elgar 2011). Thus, genital elongation in E. janeirensis suggests intensive sperm competition in this species.…”

Ovoviviparity and genital evolution: a lesson from an earwig species with coercive traumatic mating and accidental breakage of elongated intromittent organs

“…Consistent with this view, Herter () observed a large variation (12–26 days after the first mating) in the timing of the appearance of nymphs among females maintained under the same conditions after their first mating. There is increasing evidence of the ability of females to choose sperm after mating (Eberhard, ; Peretti & Aisenberg, ; see Kamimura, , , for earwigs). Eberhard () indicated that viviparous or ovoviviparous females have many more opportunities to bias paternity among multiple mates, because of the prolonged interaction between a mother and the developing embryos in the mother's body.…”

Significance of constraints on genital coevolution: Why do femaleDrosophilaappear to cooperate with males by accepting harmful matings?

“…Increasing evidence suggests that females make judgements on the quality of males based on features of their genitalia, including behavior, thereby increasing the female's fitness by selecting high‐quality sires (Peretti and Aisenberg ). In addition to female sense organs, female genital morphology can drive this type of postcopulatory sexual selection, termed cryptic female choice (CFC; Thornhill ) (Eberhard ; Kamimura ).…”

“…If there is genetic variation in the male ability to overcome female resistance, it results in genetic benefits to the resisting females since the persistence of their sons increases (Cordero and Eberhard ). Even when the direct costs of additional mating events outweigh the associated genetic benefits (e.g., coercive mating by males), the specialization of female morphology or physiology can evolve as a CFC mechanism to accumulate genetic benefits that compensate for the imposed mating costs (Kamimura ). Finally, females are expected to counter‐adapt to mitigate mating costs imposed by males, thereby decreasing the costs from SC, which are difficult to detect over most evolutionary time (Reinhardt et al.…”