Résumé
Genetic relatedness in animal societies is often a factor that drives the
structure of social groups. In the marine world, most studies which have
investigated this question have focused on marine mammals such as whales
and dolphins. For sharks, recent studies have demonstrated preferential
associations among individuals from which social communities emerge.
Assortment patterns have been found according to phenotypic or behavioural
traits but the role of genetic relatedness in shaping the social structure
of adult shark populations has, to the best our knowledge, never been
investigated. Here, we used a social network analysis crossed with DNA
microsatellite genotyping to investigate the role of the genetic
relatedness in the social structure of a blacktip reef shark (Carcharhinus
melanopterus) population. Based on data from 156 groups of sharks, we used
generalized affiliation indices to isolate social preferences from
non-social associations, controlling for the contribution of sex, size,
gregariousness, spatial and temporal overlap on social associations, to
test for the influence of genetic relatedness on social structure. A
double permutation procedure was employed to confirm our results and
account for issues arising from potentially elevated type I and type II
error rates. Kinship was not a predictor of associations and affiliations
among sharks at the dyad or community levels as individuals tended to
associate independently of the genetic relatedness among them. The lack of
parental care in this species may contribute to the breakdown of family
links in the population early in life, thereby preventing the formation of
kin-based social networks.