Fisherian and "good genes" benefits of mate choice: how (not) to distinguish between them

"Good genes" models of mate choice are commonly tested by examining whether attractive males sire offspring with improved survival. If offspring do no t survive better (or indeed survive less well), but instead inherit the att ractiveness of their father, results are typically interpreted to support t he Fisherian process, which allows the evolution of preferences for arbitra ry traits. Here, I show that the above view is mistaken. Because of life-hi story trade-offs, an attractive male may perform less well in other compone nts of fitness. A female obtains a "good genes" benefit whenever males show heritable variation in quality, even if high-quality males invest so much in sexual advertisement that attractiveness has no positive correlation wit h any other life-history trait than male mating success itself. Therefore, a negative correlation between attractiveness and viability does not falsif y good genes, if mating with a high-quality male results on average in supe rior offspring performance (mating success of sons included). The heritable "good genes" benefit can be sustained even if sexually antagonistic genes cause female offspring sired by high-quality males to survive and reproduce less well. Neglecting the component of male mating success from measuremen ts of fitness returns from sons and daughters will bias the advantage of ma ting with a high-quality male downwards. This result may partly account for the rather weak "good genes" effects found in a recent meta-analysis.