Truth in Advertising: The Kinds of Traits Favored by Sexual Selection

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Abstract
The truth in advertising model describes a mechanism of sexual selection to account for the evolution of the kinds of traits used by males of polygynous species to compete for and attract mates. Sexual selection favors the display of male traits that vary phenotypically within and among individuals which maintain a positive correlation between the degree of expression of the traits and overall genetic fitness. Because the exaggerated expression of these traits requires allocation of limited resources to reproduction, it reflects age, nutritional condition, social status and resistance to predators and pathogens. It is advantageous to females to choose mates with such exaggerated traits (and also those that have won aggressive bouts with other males) because these traits honestly advertise desirable attributes that can be passed on to both male and female offspring. By stressing the relationship between sexual traits and overall male fitness, this model deemphasizes the traditional dichotomies between the effects of sexual selection and natural selection and between female choice and male-male competition as mechanisms of sexual selection. Necessary conditions and predicted consequences of the truth in advertising mechanism are illustrated with examples of antlers of deer and nuptial coloration in fishes.