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 f...