The Genetic Relatedness in Groups of Joint-Nesting Taiwan Yuhinas: Low Genetic Relatedness with Preferences for Male Kin

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.

Correlated pay-offs are key to cooperation

“…However, the general belief that kin selection is necessary to maintain cooperation and altruism in social groups has recently been challenged by results from cooperatively breeding insects and vertebrates, in which groups are composed mainly of non-relatives (e.g. [2][3][4][5]; cf. [6,7]), and by the realization that cooperative interactions among non-relatives are widespread in contexts outside of cooperative breeding (e.g.…”

Understanding dispersal patterns can inform future translocation strategies: A case study of the threatened greater stick‐nest rat (Leporillus conditor)

“…A Wilcoxon rank sum test was chosen because the data were not normally distributed. If sexbiased dispersal was occurring, individuals of the dispersing sex were expected to demonstrate lower relatedness than the philopatric sex at the cooperative group level (Liu et al 2015).…”

Prenatal environmental conditions underlie alternative reproductive tactics that drive the formation of a mixed-kin cooperative society

“…Although most animal societies are therefore characterized by groups with high kin structure, a surprising number of species form social groups with low kin structure (Riehl, 2013) that consist of same-sex residents and immigrants, which often compete for breeding opportunities (Baglione et al, 2002;Davidian et al, 2016;Kaiser et al, 2018;Reyer, 1980). Since kin selection alone cannot explain the evolution of these mixed-kin societies (Liu et al, 2015;Riehl and Jara, 2009;Rubenstein and Abbot, 2017), direct reproductive or survival benefits may underlie their formation (Baglione et al, 2002;Clutton-Brock, 2002;Kaiser et al, 2018). Understanding how mixed-kin cooperative societies form and remain stable despite their reduced kin structure and potential for high social conflict will require examining the causes and lifetime fitness consequences of individual dispersal decisions to determine why some individuals choose to remain in their natal groups with kin while others do not.…”

“…Although most animal societies are therefore characterized by groups with high kin structure, a surprising number of species form social groups with low kin structure 6 that consist of same-sex residents and immigrants, which often compete for breeding opportunities 7-10 . Since indirect benefits alone cannot explain the evolution of these mixed-kin societies [11][12][13] , direct reproductive or survival benefits may underlie their formation 7,9,14 . Understanding how mixed-kin cooperative societies form and remain stable despite their reduced kin structure and potential…”