A model of the interaction between ‘good genes’ and direct benefits in courtship-feeding animals: when do males of high genetic quality invest less?

Abstract

Conflict between mates over the amount of parental investment by each partner is probably the rule except in rare cases of genetic monogamy. In systems with parental care, males may frequently benefit by providing smaller investments than are optimal for individual female partners. Females are therefore expected to choose males that will provide the largest amounts of parental investment. In some species, however, the preferred males provide less care than their rivals. Focusing on species in which males invest by feeding their mates, I use a simple model to demonstrate the conditions under which males preferred by females may have optimal donations that are smaller than those of less-preferred rivals. Pre-mating female choice may sufficiently bias the perception of mate availability of preferred males relative to their rivals such that preferred males gain by conserving resources for future matings. Similarly, 'cryptic' biases in favour of high-quality ejaculates by females can compensate for smaller than average donations received from preferred males. However, post-fertilization cryptic choice should not change the optimal donations of preferred males relative to their rivals. I discuss the implications of this work for understanding sexual selection in courtship-feeding animals, and the relevance of these systems to understanding patterns of investment for animals in general.

Sexual Conflict and Cryptic Female Choice in the Black Field Cricket, Teleogryllus Commodus

“…This has been shown in several courtship feeding insects, where spermatophore retention increases with the size of a courtship food gift (Vahed 1998;Gwynne 2001). However, the extent to which such biased insemination arises via indirect selection for genetic benefits rather than direct selection for food acquisition is not clear (Gwynne 2001;Bussière 2002). In field crickets, where spermatophores are not associated with large nutritional donations (but see Wagner et al 2001), the evidence for CFC is more equivocal, especially when one considers the probable publication bias against negative results.…”

“…The mechanisms and evolutionary consequences of sperm competition are well established (Birkhead and Moller 1998;Simmons 2001b), but the prevalence of CFC remains controversial (Birkhead 1998;Telford and Jennions 1998;Birkhead 2000;Eberhard 2000;Kempenaers et al 2000;Pitnick and Brown 2000;Birkhead and Pizzari 2002) in spite of its numerous and important evolutionary implications (Eberhard 1996). For example, CFC is central to determining whether post-copulatory processes reinforce or oppose pre-copulatory mate choice (Danielsson 2001) and whether indirect benefits of post-copulatory paternity biasing can offset or complement the direct costs and benefits of mating (Bussière 2002;Cameron et al 2003;Chapman et al 2003a;Eberhard and Cordero 2003).…”

Cryptic Female Choice in Crickets and Relatives (Orthoptera: Ensifera)

“…Such variation will obviously reduce the extent to which gift size will act as an honest indicator of male genetic quality. It has even been proposed that attractive, high-quality males should provide smaller gifts due to their higher expected mating frequency (allocating limited gift resources over a greater number of matings) (Bussière 2002).…”

Incidental Sanctions and the Evolution of Direct Benefits

“…For genetic benefits, the primary problem for signal reliability is deceptive signaling by males of low genetic quality; males of high genetic quality cannot cheat by choosing to provide lower fitness alleles, and would not profit from doing so. For direct benefits, however, there are two problems for signal reliability: deceptive signaling by males unable to provide high quality benefits, and cheating by males that are able to produce attractive signals and provide high quality benefits but choose to withhold the benefits (Bussière 2002; Bussière et al. 2005).…”