Low levels of relatedness on black grouse leks despite male philopatry

Abstract

In lekking species, males cluster on specific areas for display (the leks) and females generally prefer to copulate with males on large aggregations. The maintenance of leks in which only a few males reproduce might be explained if subordinate males gain indirect fitness benefits. By joining a lek on which relatives are displaying, subordinates might attract more females to the lek thereby increasing the mating opportunities of their kin. In black grouse, a genetic structure among leks has previously been found suggesting that relatives could display together. Using 11 microsatellite loci, we extended this result by testing for the presence of kin structures in nine black grouse leks (101 males). The genetic differentiation among flocks was higher in males than in females, suggesting female-biased dispersal and male philopatry. Because of this genetic structure, males were more related within than among leks. However, the mean relatedness within each lek hardly differed from zero. The lekking males were not more related than random assortments of males from the winter flocks and there were no kin clusters within leks. Thus, black grouse males do not choose to display with and close to relatives. Male philopatry alone was not sufficient to induce elevated levels of relatedness on the leks either because of male partial dispersal or a rapid turnover of the successful males. The indirect fitness benefits associated with males' settlement decision are probably limited compared to the direct benefits of joining large aggregations such as increased current and future mating opportunities.