Sexual selection when the female directly benefits

Abstract

Why do females of many species mate with males on the basis of traits apparently detrimental to male survival? The answer may lie in the fact that these male traits are correlated with male condition. We consider the argument that high male condition directly benefits female fecundity and/or viability (e.g. through lower transmission of parasites, improved control of resources, or better paternal care). Using a quantitative genetic model we show how female preferences for male traits that indicate condition can evolve, even if the male traits themselves have deleterious effects on both the male and the female's fecundity. So-called 'arbitrary preferences' can spread in this way because male traits subject to sexual selection are often under additional selection to become correlated with condition. At equilibrium the positive effects of male condition on a female's fecundity and the negative effects of the male trait on her fecundity are balanced and the female preference is under stabilizing selection. The male trait will often be correlated with viability, but not with fecundity, even though the preference evolved as a rrsult of differences in male fecundity. The mean fecundity of females is not maximized, and can steadily decline as the male trait and female preference evolve. If the male trait has no direct deleterious effects on female fecundity, as may happen in species with no paternal care, female preferences are under continuous directional selection to increase. ADDITIONAL KEY WORDS:-Fecundityselection --handicapsmean fitnessfemale preferencesconditionpaternal carequantitative geneticstheoretical modelsbirds.

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

“…Indirect mate choice also fits models of assessment of mates (Andersson 1986;Grafen 1990a,b;Iwasa et al 1991;Price et al 1993). These models assume that females benefit by mating with males in better physiological condition.…”

Fisherian flies: benefits of female choice in a lekking sandfly

“…However, demonstrating that a particular bene¢t exists does not by itself mean that it plays the major role in maintaining female choice in a particular species. For example, if direct bene¢ts are present, they are likely to have a much greater e¡ect on female ¢tness than any indirect bene¢ts (Price 1993;Kirkpatrick & Barton 1997). Thus evidence that indirect bene¢ts underpin female choice would be most convincing if coupled with evidence of a lack of direct bene¢ts.…”

Why do multiple traits determine mating success? Differential use in female choice and male competition in a water boatman

“…Interestingly, the importance of adult condition increased when male competition was included, resulting in the 'choice' of the male in the best overall condition. Condition is generally assumed to reflect mate quality by reflecting direct or indirect genetic benefits of mate choice (Andersson 1986;Price et al 1993;Johnstone 1995;Rowe & Houle 1996;Griffith et al 1999;David et al 2000;Kotiaho et al 2001). Thus, females could benefit from mating with males in good condition and consequently from the inclusion of male competition.…”

“…Traits used as cues in mate choice are generally assumed to be condition dependent (Andersson 1986;Price et al 1993;Johnstone 1995;Rowe & Houle 1996;Griffith et al 1999;David et al 2000;Kotiaho et al 2001). This can ensure that the traits reflect mate quality by preventing low-condition individuals from developing traits as large or pronounced as males in good condition, presuming that condition correlates with quality.…”