Widdig Anja, Engel Lisa, Ruiz-Lambides Angelina, Dubuc Constance, Weiß Brigitte M
Department of Human Behavior, Ecology and Culture, Max-Planck Institute for Evolutionary Anthropology, Research Group of Primate Behavioral Ecology, Leipzig, Germany.
Research Group of Behavioral Ecology, Institute of Biology, University of Leipzig, Leipzig, Germany.
Am J Primatol. 2025 Feb;87(2):e23687. doi: 10.1002/ajp.23687. Epub 2024 Oct 22.
The unequal share in male reproduction (male reproductive skew) has been reported across primate species. To explain the distribution of male reproduction within groups various skew models have been applied to primates, however the "dynamic tug-of-war" model first accounted for the specifics of primate sociality. This model assumes that an increase in the number of competing males, a high degree of female cycle synchrony and their interaction will result in a lower degree of male reproductive skew. Here, we first tested the predictors of this model in rhesus macaques (Macaca mulatta) using long-term demographic and genetic data (up to 9 groups over 22 seasons) of the Cayo Santiago population (Puerto Rico). We also tested an extended version including group size and sex ratio and their interaction with female cycle synchrony. Finally, we investigated which male attributes determine the probability to become a top sire (highest paternity share per group and season). Confirming studies, male rhesus macaques exhibited low to medium degrees of reproductive skew based on the multinomial index, M. Unlike predicted, reproductive skew was higher in groups with more males. The extended analysis suggested that reproductive skew increased with group size in more male-biased groups, but decreased with group size in female-biased groups indicating that the numbers of male and female group members matter. We detected no effect of female cycle synchrony on the variance of reproductive skew. Finally, only maternal rank predicted the probability to become a top sire as long as males resided in their natal group. Together, our results did not support predictions by the dynamic skew model in rhesus macaques, but strengthen studies suggesting that other factors in addition to male-male competition predict male reproductive output in rhesus macaques. Future skew studies should consider female choice and alternative male mating strategies.
在灵长类动物中，雄性繁殖份额不均（雄性繁殖偏斜）的现象已被报道。为了解释群体内雄性繁殖的分布情况，各种偏斜模型已应用于灵长类动物，但“动态拔河”模型首次解释了灵长类动物社会性的具体情况。该模型假设，竞争雄性数量的增加、雌性发情周期的高度同步及其相互作用将导致雄性繁殖偏斜程度降低。在此，我们首先利用波多黎各圣地亚哥岛种群（长达22个季节的9个群体）的长期人口统计学和遗传学数据，对恒河猴（猕猴）中该模型的预测因素进行了测试。我们还测试了一个扩展版本，包括群体大小和性别比例及其与雌性发情周期同步的相互作用。最后，我们研究了哪些雄性特征决定了成为顶级父亲（每个群体和季节父权份额最高）的概率。与以往研究一致，基于多项指数M，恒河猴雄性表现出低到中等程度的繁殖偏斜。与预测不同的是，雄性较多的群体中繁殖偏斜程度更高。扩展分析表明，在雄性偏多的群体中，繁殖偏斜随群体大小增加，而在雌性偏多的群体中则随群体大小降低，这表明群体中雄性和雌性成员的数量很重要。我们未检测到雌性发情周期同步对繁殖偏斜方差的影响。最后，只要雄性居住在其出生群体中，只有母亲的等级能预测成为顶级父亲的概率。总之，我们的结果不支持恒河猴中动态偏斜模型的预测，但强化了其他研究结果，即除了雄性间竞争外，其他因素也能预测恒河猴的雄性繁殖产出。未来的偏斜研究应考虑雌性选择和雄性的替代交配策略。
