Whitlock&Agrawal.Evolution.09 - PERSPECTIVE...

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PERSPECTIVE doi:10.1111/j.1558-5646.2008.00558.x PURGING THE GENOME WITH SEXUAL SELECTION: REDUCING MUTATION LOAD THROUGH SELECTION ON MALES Michael C. Whitlock 1 , 2 and Aneil F. Agrawal 3 , 4 1 Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4 Canada 2 E-mail: [email protected] 3 4 E-mail: [email protected] Received July 2, 2008 Accepted September 23, 2008 Healthy males are likely to have higher mating success than unhealthy males because of differential expression of condition- dependent traits such as mate searching intensity, ±ghting ability, display vigor, and some types of exaggerated morphological characters. We therefore expect that most new mutations that are deleterious for overall ±tness may also be deleterious for male mating success. From this perspective, sexual selection is not limited to influencing those genes directly involved in exaggerated morphological traits but rather affects most, if not all, genes in the genome. If true, sexual selection can be an important force acting to reduce the frequency of deleterious mutations and, as a result, mutation load. We review the literature and ±nd various forms of indirect evidence that sexual selection helps to eliminate deleterious mutations. However, direct evidence is scant, and there are almost no data available to address a key issue: is selection in males stronger than selection in females? In addition, the total effect of sexual selection on mutation load is complicated by possible increases in mutation rate that may be attributable to sexual selection. Finally, sexual selection affects population ±tness not only through mutation load but also through sexual conflict, making it dif±cult to empirically measure how sexual selection affects load. Several lines of enquiry are suggested to better ±ll large gaps in our understanding of sexual selection and its effect on genetic load. KEY WORDS: Condition, male mating success, mean ±tness, mutation load, sexual selection, vigor. Sexual selection is the selection that arises from differential mat- ing success among living individuals. Although the study of sexual selection has focused on the evolution of showy secondary sexual traits such as the peacock’s tail, other factors may contribute even more heavily to the mating success of an individual. For example, the overall health of a male may determine the energy with which he searches for and courts females, the strength and weight of a male may determine the outcome of interactions between rival suitors, and the vigor and condition of a male may directly affect his attractiveness to a potential mate (Andersson 1994). Although some of these effects may be mediated through effects on exag- gerated morphological characteristics, the health and condition of a male has great potential also to directly affect his mating success. Most genes in the genome likely contribute to the overall
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This note was uploaded on 06/08/2011 for the course PCB 4674 taught by Professor Baer during the Fall '08 term at University of Florida.

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Whitlock&Agrawal.Evolution.09 - PERSPECTIVE...

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