Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.
Department of Anthropology, Center for the Advanced Study of Human Paleobiology, The George Washington University, Washington, District of Columbia, United States of America.
PLoS One. 2020 Jun 3;15(6):e0233235. doi: 10.1371/journal.pone.0233235. eCollection 2020.
According to life history theory, natural selection has shaped trade-offs for allocating energy among growth, reproduction and maintenance to maximize individual fitness. In social mammals body size and dominance rank are two key variables believed to influence female reproductive success. However, few studies have examined these variables together, particularly in long-lived species. Previous studies found that female dominance rank correlates with reproductive success in mountain gorillas (Gorilla beringei beringei), which is surprising given they have weak dominance relationships and experience seemingly low levels of feeding competition. It is not currently known whether this relationship is primarily driven by a positive correlation between rank and body size. We used the non-invasive parallel laser method to measure two body size variables (back breadth and body length) of 34 wild adult female mountain gorillas, together with long-term dominance and demography data to investigate the interrelationships among body size, dominance rank and two measures of female reproductive success (inter-birth interval N = 29 and infant mortality N = 64). Using linear mixed models, we found no support for body size to be significantly correlated with dominance rank or female reproductive success. Higher-ranking females had significantly shorter inter-birth intervals than lower-ranking ones, but dominance rank was not significantly correlated with infant mortality. Our results suggest that female dominance rank is primarily determined by factors other than linear body dimensions and that high rank provides benefits even in species with weak dominance relationships and abundant year-round food resources. Future studies should focus on the mechanisms behind heterogeneity in female body size in relation to trade-offs in allocating energy to growth, maintenance and lifetime reproductive success.
根据生活史理论，自然选择塑造了在生长、繁殖和维持之间分配能量的权衡，以最大限度地提高个体适应性。在社会性哺乳动物中，体型和支配地位等级是两个被认为影响雌性生殖成功的关键变量。然而，很少有研究同时考察这些变量，特别是在长寿命物种中。先前的研究发现，雌性支配地位等级与山地大猩猩（Gorilla beringei beringei）的生殖成功相关，这令人惊讶，因为它们的支配关系较弱，并且似乎经历了较低水平的摄食竞争。目前尚不清楚这种关系是否主要是由等级和体型之间的正相关关系驱动的。我们使用非侵入性的平行激光方法测量了 34 只野生成年雌性山地大猩猩的两个体型变量（背部宽度和体长），以及长期的支配地位和人口统计数据，以研究体型、支配地位等级和两种雌性生殖成功指标（生育间隔 N = 29 和婴儿死亡率 N = 64）之间的相互关系。使用线性混合模型，我们没有发现体型与支配地位等级或雌性生殖成功有显著相关性的证据。高等级雌性的生育间隔明显短于低等级雌性，但支配地位等级与婴儿死亡率没有显著相关性。我们的结果表明，雌性支配地位等级主要由体型线性维度以外的因素决定，即使在支配关系较弱且全年食物资源丰富的物种中，高等级也能提供好处。未来的研究应集中于与生长、维持和终生生殖成功之间的能量分配权衡相关的女性体型异质性背后的机制。
