Within the same species, individuals show marked variation in their social dominance. Studies on a handful of populations have indicated heritable genetic variation for this trait, which is determined by both the genetic background of the individual (direct genetic effect) and of its opponent (indirect genetic effect). However, the evolutionary consequences of selection for this trait are largely speculative, as it is not a usual target of selection in livestock populations. Moreover, studying social dominance presents the challenge of working with a phenotype with a mean value that cannot change in the population, as for every winner of an agonistic interaction there will necessarily be a loser. Thus, to investigate what could be the evolutionary response to selection for social dominance, it is necessary to focus on traits that might be correlated with it. This study investigated the genetic correlations of social dominance, both direct and indirect, with several morphology and fitness traits. We used a dataset of agonistic contests involving cattle (Bos taurus): during these contests, pairs of cows compete in ritualized interactions to assess social dominance. The outcomes of 37,996 dominance interactions performed by 8789 cows over 20 years were combined with individual data for fertility, mammary health, milk yield and morphology and analysed using bivariate animal models including indirect genetic effects. We found that winning agonistic interactions has a positive genetic correlation with more developed frontal muscle mass, lower fertility, and poorer udder health. We also discovered that the trends of changes in the estimated breeding values of social dominance, udder health and more developed muscle mass were consistent with selection for social dominance in the population. We present evidence that social dominance is genetically correlated with fitness traits, as well as empirical evidence of the possible evolutionary trade-offs between these traits. We show that it is feasible to estimate genetic correlations involving dyadic social traits.

中文翻译：

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牛社会优势的直接和间接遗传成分与健康和形态特征的遗传相关性

在同一物种内，个体的社会统治地位表现出显着的差异。对少数人群的研究表明，这种性状存在可遗传的遗传变异，这是由个体的遗传背景（直接遗传效应）及其对手（间接遗传效应）决定的。然而，对该性状的选择的进化后果在很大程度上是推测性的，因为它不是牲畜种群中通常的选择目标。此外，研究社会支配地位提出了一个挑战，即研究具有在群体中无法改变的均值的表型，因为竞争性互动的每一个胜利者都必然有一个失败者。因此，为了研究对社会支配地位选择的进化反应，有必要关注可能与之相关的特征。本研究调查了社会主导地位与多种形态和健康特征的直接和间接遗传相关性。我们使用了涉及牛（Bos taurus）的竞争竞赛数据集：在这些竞赛中，成对的牛通过仪式化的互动进行竞争，以评估社会主导地位。将 8789 头奶牛在 20 年来进行的 37,996 次优势相互作用的结果与生育力、乳房健康、产奶量和形态的个体数据相结合，并使用包括间接遗传效应在内的双变量动物模型进行分析。我们发现，赢得竞争性相互作用与更发达的额肌质量、较低的生育能力和较差的乳房健康状况具有正向遗传相关性。我们还发现，社会优势、乳房健康和更发达的肌肉质量的估计育种值的变化趋势与群体中社会优势的选择一致。我们提供的证据表明，社会主导地位与健康特征在遗传上相关，以及这些特征之间可能的进化权衡的经验证据。我们证明估计涉及二元社会特征的遗传相关性是可行的。