Data from: Kin selection may contribute to lek evolution and trait introgression across an avian hybrid zone

Understanding the mechanism(s) that favor cooperation among individuals
competing for the same resources provides direct insights into the
evolution of grouping behaviour. In a hybrid zone between
golden/yellow-collared (Manacus vitellinus) and white-collared (M. candei)
manakins, males form aggregations composed of white and yellow males
solely to attract females (“mixed leks”). Previous work shows that yellow
males in these mixed leks experience a clear mating advantage over white
males, resulting in the preferential introgression of yellow plumage
allele(s) into the white species. However, the yellow male mating
advantage only occurs in mixed leks with high frequency of yellow males
and only a few of these males likely mate. Hence, it remains unclear why
unsuccessful males join leks. Here, we used microsatellite markers to
estimate pair-wise relatedness among males within and between leks to test
if indirect genetic benefits of helping kin (“kin selection”) can promote
grouping. We found that yellow males are significantly more related to
each other within than between leks, while relatedness among white males
did not differ within and between leks. This suggests that yellow males
may indirectly enhance their own reproductive success by preferentially
lekking with relatives because yellow plumage is under positive frequency
dependent selection. Our results are consistent with the hypothesis that
kin selection may promote grouping and facilitate positive frequency
dependent selection for yellow males, mediating the movement of yellow
plumage across this hybrid zone.