ABS 2022
Reciprocal help is more evident than kin-bias in a mixed-kin, plural cooperatively breeding society
Alexis D. Earl1, Gerald G. Carter2, Shailee S. Shah1, Arden G. Berlinger1, Dustin R. Rubenstein1. 1Department of Ecology, Evolution, and Environmental Biology, Columbia University, New York, New York, United States; 2Department of Evolution, Ecology and Organismal Biology, The Ohio State University, Columbus, Ohio, United States

Cooperatively breeding societies are typically characterized by nonbreeding helpers who assist in raising others’ offspring. Although the evolution of such societies has historically been explained by kin selection, there is increasing evidence that cooperative breeding can also be favored by direct fitness benefits, particularly in social groups with low and mixed kinship. Understanding the relative importance of direct versus indirect benefits in the evolution of cooperative societies requires identifying the mechanisms that underlie helping behavior. Using a 20-year study of the obligate plural cooperatively breeding superb starlings (Lamprotornis superbus) who live in social groups with multiple breeding pairs and low kinship, we determined whether helpers preferentially assist relatives (kin-bias) or individuals who previously helped them (reciprocal helping), while controlling for sampling bias. Although we detected reciprocal helping when controlling for relatedness, we did not detect kin biases when controlling for reciprocal help. These results suggest that the direct benefits of reciprocity might help promote the evolution and stability of complex cooperative societies.