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.

The DataZip file contains the following objects:

DataNetwork.csv

This file contains all observations of individual sharks (rows).

ID contains the identification of all individuals observed in the groups;
Group is the identification number of the groups;
Date is the date at which the observation was made;
Year is the year at which the observation was made;
Month is the month number at which the observation was made;
Period contains information on the period of observation (M = mating period, N = non-mating period);
Site is the site ID where the observation was made;
WeekNB is the week of the year at which the observation was made;
Spweek is the continuous week number of these observations;
SPMonth is the continuous month number of these observations
Genetic contains information on whether genetic sample was taken for the individual.

DataBTRS_15sightings.csv

This file contains five variables of 156 groups (rows).

Date is the date at which the group was observed;
Year is the year of the observed group;
Month is the month of the observed group;
Period contains information on the period of observation (M = mating period, N = non-mating period);
Site is the site ID where the observation was made;
Lat is the latitude of the site
Long is the latitude of the site
SP is the continuous week number of these observations
IDs contains the identification of all individuals observed in the groups.

Attribute.csv

This file contains five covariables of 106 photo-identified individuals.

ID contains the identity of all 106 photo-identified individuals;
Sex contains the sex of each individual, where M refer to male individuals and F to females;
Size contains the size (in cm) for each individual;
Maturity contains the maturity status for each individual (MATURE = sexually mature, IMMATURE = sexually immature);
DNA contains information on whether genetic sample was taken for the individual (Y = sampled, N = unsampled).

No.sightings.csv

This file contains three covariables of 106 photo-identified individuals in the overall study (without threshold).

ID contains the identity of all 106 photo-identified individuals;
Sightings contains the number of times the individual was sighted;
Context indicates in which context the number of sightings corresponds to (All = overall study, Mating = mating period, NonMating = non-mating period)

MatrixGeneticRelatedness_Trioml.csv

This file contains the pairwise genetic relatedness (TrioML, Wang 2007) among 83 individuals.

SpatialProfile.csv

This file contains for each individual and each site an encounter rate (i.e., no. sightings of individual at site, divided by no. sampling occasions at site).

CountSightings.csv

This file contains for each individual and each site the number of sightings.

TempData.csv

This file contains five covariables to calculate temporal overlap.

ID contains the identity of all 106 photo-identified individuals;
Group is the identification number of the groups;
Date is the date at which the observation was made;
Site is the site ID where the observation was made;
SPMonth is the continuous month number of these observations

Genotype(16markers).txt

This file contains the genotypes of 83 individuals at 16 microsatellite markers.