Microsatellite markers reveal the potential for kin selection on black grouse leks

The evolution of social behaviour has puzzled biologists since Darwin. Sinc e Hamilton's theoretical work in the 1960s it has been realized that social behaviour may evolve through the effects of kinship. By helping relatives, an individual may pass on its genes despite negative effects on its own re production. Leks are groups of males that females visit primarily to mate. The selective advantage for males to join such social groups has been given much recent attention, but no clear picture has yet emerged. Here we show, using microsatellite analysis, that males but not females of a lekking bir d (the black grouse, Tetrao tetrix) are genetically structured at the lek l evel. We interpret this structuring to be the effects of strong natal philo patry in males. This has the consequence that males on any specific lek sho uld be more related than expected by chance as indicated by our genetic dat a. Our results thus suggest that kin selection is a factor that needs to be considered in the evolution and maintenance of the lek mating system in bl ack grouse and sheds new light on models of lek evolution.