Kin selection and the evolution of leks: Whose success do young males maximize?

A proper explanation for the evolution oflekking behaviour requires understanding the advantages that individual males obtain by aggregating. An uneven distribution of mating success gives rise to a conflict between males in the optimal level of aggregation, suggesting that low-rank males should prefer as large leks as possible. However, observations do not strongly support this outcome. We present a completely new hypothesis of kin selection affecting the formation of leks. Even a small probability of the top-rank male and his offspring displaying on the same lek suffices to enable indirect fitness components override the effect of direct mating success in young displaying males. Our model also produces cases with multiple optima, where young males are caught in a suboptimal, non-cooperative strategy. By using data on black grouse, Tetrao tetrix, and ruff, Philomachus pugnax, we show chat criteria for kin selection altering the optima in observed leks are reasonable.