Postcopulatory sexual selection: Darwin's omission and its consequences

Abstract

In one of his few major oversights, Darwin failed to appreciate that male-male competition and sexual selection can continue even after copulation has begun. The postcopulatory equivalents of both direct male-male battles (sperm competition) and female choice (cryptic female choice) occur within the female's body. Recognition of this hidden, but intense, sexual competition provides new insights into a variety of fields. These include the hyperdiverse and paradoxically elaborate morphology of both sperm and male genitalia, the equally puzzling and elaborate morphology of nongenitalic male structures that are specialized to grasp and stimulate females, powerful manipulative effects of substances in male semen on female reproductive physiology, paradoxical male courtship behavior that occurs after copulation has already begun, variability in parental investments, and the puzzlingly complex and diverse interactions between sperm and female products that surround animal eggs and between male gametophytes and female tissues in flowering plants. Many bizarre traits are involved, including male genitalia that are designed to explode or fall apart during copulation leaving behind parts within the female, male genitalia that ''sing'' during copulation, potent seminal products that invade the female's body cavity and her nervous system to influence her behavior, and a virtual Kama Sutra of courtship behavior performed after rather than before genital coupling, including male-female dialogues during copulation.cryptic female choice ͉ sexually antagonistic coevolution P icture a pile of freshly-cut weeds at the sunny edge of a tropical forest. Metallic green flies dart and circle over it, chasing one another in short dashes. Your eye is caught when a chase ends as one fly grasps another in midair and the pair immediately lands on the pile of weeds. Their genitalia are already coupled, and the male immediately turns to face away from the female. After a few seconds, paradoxically (because he is already securely attached), he begins to court, rhythmically waving his colorful hind legs and tapping the female's abdomen. The courtship continues for a few minutes as the pair remains coupled, and then the flies separate. The female walks down into the pile where she lays eggs (her larvae will feed on the rotting vegetation), while the male rejoins the frenetic chases above the pile.Why would a male fly wait to court a female until after he has already achieved his evolutionary objective of copulating with her? The answer (recently worked out by a Brazilian graduate student, F. Barbosa, personal communication) had to wait for Ͼ100 years after Darwin's great book on sexual selection (1) that explained so many other aspects of male-female sexual interactions.

The spermatozoa structure peculiarities of the subgenus Sumeriomys (Rodentia, Arvicolinae, Microtus)

“…The diversity in sperm design reflects the highly variable physiological and morphological environments in which sperm have to survive, function, and compete for fertilization (Eberhard, 2009). It is difficult to explain the reasons of so considerable transformations of spermatozoa in these related groups of species.…”

Female cooperation in plug formation in a spider: effects of male copulatory courtship

“…In addition, females showed no sign of resistance to these male behavior patterns, despite the fact that they can easily interrupt undesired coercion by breaking away from males at any time during copulation or by pushing the male's palp away from the epigynum with their tarsi (Eberhard and Huber 1998;Mendez 2004). A sensory trap version of SAC (Arnqvist 2006), which supposes that female cooperation with the male is not in her own reproductive best interests, but persists because the male uses a sensory trap, also seems unlikely (though it cannot be eliminated) because it depends on females having been unable to free themselves from these traps (Eberhard 2009). For instance, a female change in response threshold or context-specific changes in female responsiveness could free the female from maladaptive oversensitivity to male stimulation.…”

Secondary Sexual Characteristics in the Galerucinae (Sensu Stricto) (Coleoptera: Chrysomelidae)

“…One common function of this structure is to grasp the female. The nongenitalic male structure, such as modified antennae and legs that are specialized to grasp and stimulate the female, is involved in intersexual competition [13]; thus, the tight grasping by the copulating male resists any attempt by another male to dislodge the copulation.…”

“…Observational and 2 ISRN Zoology experimental evidence suggest that feather ornaments of birds play an important role in female choice [11]. Eberhard [12,13] referred to an SSC as the nongenitalic male contact structure, a product of an intersexual competition [14]. Besides agreeing that SSCs are the result of Darwinian selection, Jolivet [15] noted that they are also a manifestation of biodiversity.…”