Sanderson J L, Nichols H J, Marshall H H, Vitikainen E I K, Thompson F J, Walker S L, Cant M A, Young A J
Centre for Ecology and Conservation, University of Exeter (Penryn Campus), Penryn TR10 9FE, UK.
School of Natural Science and Psychology, Liverpool John Moores University, Liverpool L3 3AF, UK.
Biol Lett. 2015 Oct;11(10). doi: 10.1098/rsbl.2015.0620.
Dominant females in social species have been hypothesized to reduce the reproductive success of their subordinates by inducing elevated circulating glucocorticoid (GC) concentrations. However, this 'stress-related suppression' hypothesis has received little support in cooperatively breeding species, despite evident reproductive skews among females. We tested this hypothesis in the banded mongoose (Mungos mungo), a cooperative mammal in which multiple females conceive and carry to term in each communal breeding attempt. As predicted, lower ranked females had lower reproductive success, even among females that carried to term. While there were no rank-related differences in faecal glucocorticoid (fGC) concentrations prior to gestation or in the first trimester, lower ranked females had significantly higher fGC concentrations than higher ranked females in the second and third trimesters. Finally, females with higher fGC concentrations during the third trimester lost a greater proportion of their gestated young prior to their emergence from the burrow. Together, our results are consistent with a role for rank-related maternal stress in generating reproductive skew among females in this cooperative breeder. While studies of reproductive skew frequently consider the possibility that rank-related stress reduces the conception rates of subordinates, our findings highlight the possibility of detrimental effects on reproductive outcomes even after pregnancies have become established.
在社会性物种中，占主导地位的雌性被认为会通过促使循环糖皮质激素（GC）浓度升高来降低其下属的繁殖成功率。然而，尽管雌性之间存在明显的繁殖偏差，但这种“与压力相关的抑制”假说在合作繁殖物种中几乎没有得到支持。我们在带状猫鼬（Mungos mungo）身上检验了这一假说，带状猫鼬是一种合作繁殖的哺乳动物，在每次群体繁殖尝试中，多个雌性都会受孕并怀胎至足月。正如预测的那样，即使在怀胎至足月的雌性中，地位较低的雌性繁殖成功率也较低。虽然在妊娠前或妊娠早期，粪便糖皮质激素（fGC）浓度没有与等级相关的差异，但在妊娠中期和晚期，地位较低的雌性fGC浓度显著高于地位较高的雌性。最后，在妊娠晚期fGC浓度较高的雌性，在幼崽从洞穴中出来之前，其怀胎的幼崽损失比例更大。总之，我们的结果与等级相关的母体压力在这种合作繁殖者中导致雌性之间繁殖偏差的作用是一致的。虽然对繁殖偏差的研究经常考虑等级相关压力降低下属受孕率的可能性，但我们的研究结果突出了即使在怀孕后，对繁殖结果也可能产生不利影响的可能性。
