The lek paradox and the capture of genetic variance by condition dependent traits

Abstract

Recent evidence suggests that sexually selected traits have unexpectedly high genetic variance. In this paper, we offer a simple and general mechanism to explain this observation. Our explanation offers a resolution to the lek paradox and rests on only two assumptions; condition dependence of sexually selected traits and high genetic variance in condition. The former assumption is well supported by empirical evidence. We discuss the evidence for the latter assumption. These two assumptions lead inevitably to the capture of genetic variance into sexually selected traits concomitantly with the evolution of condition dependence. We present a simple genetic model to illustrate this view. We then explore some implications of genic capture for the coevolution of female preference and male traits. Our exposition of this problem incidentally leads to new insights into the similarities between sexually selected traits and life history traits, and therefore into the maintenance of high genetic variance in the latter. Finally, we discuss some shortcomings of a recently proposed alternative solution to the lek paradox; selection on variance.

Sexual selection and genital allometry in the Hottentot golden mole (Amblysomus hottentotus)

“…Adaptive advantages of the observed allometry in length of the highly modified front foot in the females as opposed to males is difficult to ascertain, however, and the possibility of pleiotropy cannot be ruled out although positive allometry has been observed in the femur and tibia lengths of certain vertebrates (Lammers andGerman 2002, Farlow andPianka 2000). Consistent with results obtained by Pomiankowski and Møller (1995) coefficients of variation were notably higher in sexual than in non-sexual traits (see also Rowe and Houle, 1996).…”

Intralocus Sexual Conflict and the Genetic Architecture of Sexually Dimorphic Traits in Prochyliza Xanthostoma (Diptera: Piophilidae)

“…The observation that sexual traits tend to exhibit higher CV A and CV R than nonsexual traits accords with previous findings (Pomiankowski and Møller 1995;Rowe and Houle 1996). However, considerable variation among sexual traits in these parame-ters and in condition dependence calls for further research.…”

Sexual selection and the evolution of evolvability

“…Predominant among these are the idea that sexual traits are condition-dependent (condition being controlled by relatively large numbers of loci which together result in high levels of genetic variation) (Rowe and Houle, 1996), and the idea that variability is maintained by modifier genes (which act to increase the number of genes contributing to a trait) (Pomiankowski and M ller, 1995). However, these theories have been criticized on the grounds that non-sexual traits may also be conditiondependent and that modifier genes may themselves go to fixation (Turner, 1995;Neff, 2000).…”

“…A number of theories have been proposed to explain this paradox (Pomiankowski and M ller, 1995;Rowe and Houle, 1996;Holland and Rice, 1998;Wilkinson et al, 1998;Lesna and Sabells, 1999;Sheldon, 1999;Randerson et al, 2000;see Tomkins et al, 2004; for a review). Predominant among these are the idea that sexual traits are condition-dependent (condition being controlled by relatively large numbers of loci which together result in high levels of genetic variation) (Rowe and Houle, 1996), and the idea that variability is maintained by modifier genes (which act to increase the number of genes contributing to a trait) (Pomiankowski and M ller, 1995).…”