Data from: Kinship and association in a highly social apex predator population, killer whales at Marion Island

Social structure is a core element of population biology, influenced by intrinsic and environmental factors. Intra-taxon comparisons of social organization are useful in elucidating the role of such ecological determinants of sociality. Killer whales (Orcinus orca) are widely-distributed, social delphinids with diverse morphology, diet, behavior and genetics, but few studies have quantitatively examined social structure in this species. We used 7 years of individual identification data on killer whales at Marion Island, Southern Ocean, to calculate the half-weight association index among 39 individuals, creating a weighted association network. There were long-term associations between individuals, though associations were dynamic over time. We defined 8 social modules using a community detection algorithm and these typically contained 3 individuals of various ages and sexes. Pairwise genetic relatedness among 20 individuals was not significantly correlated with association index. Individuals were on average more related within than between social modules, but social modules contained related as well as unrelated individuals. Likely parent pairs of six individuals indicated mating between social modules.社会结构是种群生物学的核心要素之一，其受到内在因素与环境因子的共同影响。针对同一分类群内社会组织的比较研究，有助于阐明社会性的各类生态决定因子所发挥的作用。虎鲸（Orcinus orca）作为分布广泛、具有高度社会性的海豚科物种，展现出多样的形态、食性、行为与遗传特征，但目前针对该物种社会结构的定量研究仍较为匮乏。我们利用南大洋马里恩岛海域7年间的虎鲸个体识别数据，对39头个体间的半权重关联指数（half-weight association index）进行计算，构建了加权关联网络。个体间存在长期稳定的关联关系，不过这类关联亦随时间呈现动态变化。我们通过群落检测算法（community detection algorithm）定义了8个社会模块，每个模块通常包含3头不同年龄与性别的个体。20头个体间的两两遗传亲缘度与关联指数并无显著相关性。平均而言，个体在社会模块内部的亲缘关系要高于模块间的亲缘关系，但各社会模块中同时包含亲缘个体与非亲缘个体。基于6头个体的疑似亲本配对关系可知，跨社会模块间存在交配行为。