Abstract
The relative importance of direct and indirect fitness and, thus, the role of kinship in the evolution of social behavior is much debated. Studying the genetic relatedness of interacting individuals is crucial to improving our understanding of these issues. Here, we used a seven-year data set to study the genetic structure of the Taiwan yuhina (Yuhina brunneciceps), a joint-nesting passerine. Ten microsatellite loci were used to investigate the pair-wised relatedness among yuhina breeding group members. We found that the average genetic relatedness between same-sex group members was very low (0.069 for male dyads and 0.016 for female dyads). There was also a low ratio of closely-related kin (r>0.25) in the cooperative breeding groups of yuhinas (21.59% and 9.68% for male and female dyads, respectively). However, the relatedness of male dyads within breeding groups was significantly higher than female dyads. Our results suggest that yuhina cooperation is maintained primarily by direct fitness benefits to individuals; however, kin selection might play a role in partner choice for male yuhinas. Our study also highlights an important, but often neglected, question: Why do animals form non-kin groups, if kin are available? We use biological market theory to propose an explanation for group formation of unrelated Taiwan yuhinas.
Highlights
Since Hamilton’s seminal work [1,2], the concept of inclusive fitness has played a crucial role in the study of social behavior
The mean relatedness of all individuals in the Meifeng population did not deviate from an outbreed population (-0.006 ± 0.003, n = 5545, t = 1.93, p = 0.05). These results demonstrate that the microsatellite loci and estimator that we used to estimate relatedness accurately characterized the relatedness of individuals with a known pedigree
Increases in indirect fitness arising from cooperative breeding should be minimal, and inclusive fitness is not crucial factor promoting the evolution of cooperation in yuhinas
Summary
Since Hamilton’s seminal work [1,2], the concept of inclusive fitness has played a crucial role in the study of social behavior. Inclusive fitness theory revolutionized thinking about the evolution of social behavior by explaining how selection can act on a gene through its effects on its bearer’s relatives. Genetic Relatedness in Taiwan Yuhinas influence of kinship on individual behavior has been demonstrated in many studies [3,4,5]. The importance of kinship to the evolution of social behavior has been much debated [6,7,8,9]. Knowledge of the genetic relatedness between interacting individuals is crucial to measuring direct and indirect fitness and, is crucial to understanding social behavior
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