Abstract 

Group-living species are often organized into social dominance hierarchies, where high-ranking individuals have priority of access to resources, including estrous females. Traits associated with male dominance status should thus be correlated with reproductive success, but, with the exception of research on some primates, studies with both behavioral data to determine dominance hierarchies and a pedigree to identify male siring success are rare. For a wild population of sexually dimorphic eastern grey kangaroos Macropus giganteus, we characterized the social hierarchy over 6 non-consecutive years to investigate the relationship between male dominance and yearly reproductive success. Dominance hierarchies were steep, linear, and stable over time. Asymmetries in body mass and size between contestants were strong predictors of contest outcomes, and these morphological traits were positively correlated with dominance status. Males did not spatially avoid each other but tended to fight with individuals of similar size, suggesting that when asymmetries were large, contests were unlikely. Dominance status was under strong sexual selection, despite moderate monopolization of paternities by highly dominant males. Overall, these results suggest that body size and weapons are important determinants of dominance status and male reproductive success but that other traits play a considerable role. A clear-cut dominance hierarchy and strong selection on dominance status do not necessarily lead to monopolization of reproduction by the most dominant males in this strongly sexually dimorphic species.

Significance statement

It is generally assumed that high social rank in males is a very strong determinant of access to mates in polygamous species. Like other sexually dimorphic species, male kangaroos are thought to establish dominance hierarchies based on size. A few high-ranking males are then believed to monopolize matings. Our study confirms a strong correlation between body size and dominance status, and that males mostly engage in contests with males of similar size. However, we also found weak monopolization of reproduction, despite strong, positive sexual selection on dominance status. This result suggests that strong selection for high rank does not imply that subordinate males cannot sire offspring. A few highly dominant males had high reproductive success but did not monopolize matings.

中文翻译：

---

东部大灰袋鼠雄性占优势，但不垄断交配

摘要 

群居物种通常被组织成社会支配等级，其中高级个体优先获得资源，包括发情的雌性。因此，与男性优势地位相关的特征应该与繁殖成功相关，但是，除了对一些灵长类动物的研究外，很少有通过行为数据确定优势等级和确定男性父亲成功的谱系的研究。对于性二态东部灰袋鼠Macropus giganteus的野生种群，我们描述了 6 个非连续年份的社会等级，以研究男性优势与年度繁殖成功之间的关系。随着时间的推移，支配层级是陡峭的、线性的和稳定的。参赛者之间体重和体型的不对称是比赛结果的有力预测因素，这些形态特征与优势地位呈正相关。雄性不会在空间上相互避开，而是倾向于与体型相似的个体打架，这表明当不对称性很大时，不太可能发生竞争。尽管具有高度优势的男性适度垄断了亲子关系，但优势地位仍处于强烈的性选择之下。全面的，这些结果表明，体型和武器是支配地位和雄性繁殖成功的重要决定因素，但其他特征也起着相当大的作用。明确的支配等级和对支配地位的强烈选择并不一定会导致这种强烈的两性二态物种中最主要的雄性垄断繁殖。

意义陈述

人们普遍认为，男性的高社会地位是一夫多妻制物种获得配偶的一个非常重要的决定因素。与其他两性异形的物种一样，雄性袋鼠被认为是根据体型建立统治等级的。然后，一些高级雄性被认为垄断了交配。我们的研究证实了体型和支配地位之间存在很强的相关性，并且男性大多与体型相似的男性进行比赛。然而，我们也发现生殖垄断弱，尽管对支配地位有强烈的、积极的性选择。这一结果表明，对高位的强烈选择并不意味着从属男性不能生育后代。少数具有高度优势的雄性具有很高的繁殖成功率，但没有垄断交配。