Hill Davina L, Pillay Neville, Schradin Carsten
School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa.
School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa; Université de Strasbourg, IPHC-DEPE, 23 rue Becquerel 67087 Strasbourg, France; CNRS, UMR7178, 67087 Strasbourg, France; Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
Horm Behav. 2015 May;71:1-9. doi: 10.1016/j.yhbeh.2015.03.004. Epub 2015 Mar 28.
Alternative reproductive tactics (ARTs), where members of the same sex and population show distinct reproductive phenotypes governed by decision-rules, have been well-documented in males of many species, but are less well understood in females. The relative plasticity hypothesis (RPH) predicts that switches between plastic ARTs are mediated by changes in steroid hormones. This has received much support in males, but little is known about the endocrine control of female ARTs. Here, using a free-living population of African striped mice (Rhabdomys pumilio) over five breeding seasons, we tested whether females following different tactics differed in corticosterone and testosterone levels, as reported for male striped mice using ARTs, and in progesterone and oestrogen, which are important in female reproduction. Female striped mice employ three ARTs: communal breeders give birth in a shared nest and provide alloparental care, returners leave the group temporarily to give birth, and solitary breeders leave to give birth and do not return. We expected communal breeders and returners to have higher corticosterone, owing to the social stress of group-living, and lower testosterone than solitary breeders, which must defend territories alone. Solitary breeders had lower corticosterone than returners and communal breeders, as predicted, but testosterone and progesterone did not differ between ARTs. Oestrogen levels were higher in returners (measured before leaving the group) than in communal and solitary breeders, consistent with a modulatory role. Our study demonstrates hormonal differences between females following (or about to follow) different tactics, and provides the first support for the RPH in females.
替代生殖策略（ARTs）是指同一性别和种群的成员表现出由决策规则支配的不同生殖表型，这在许多物种的雄性中已有充分记录，但在雌性中却了解较少。相对可塑性假说（RPH）预测，可塑性ARTs之间的转换是由类固醇激素的变化介导的。这在雄性中得到了很多支持，但关于雌性ARTs的内分泌控制却知之甚少。在这里，我们利用非洲条纹小鼠（Rhabdomys pumilio）在五个繁殖季节的自由生活种群，测试了采用不同策略的雌性在皮质酮和睾酮水平上是否存在差异（正如使用ARTs的雄性条纹小鼠的报道），以及在孕酮和雌激素方面是否存在差异（这在雌性繁殖中很重要）。雌性条纹小鼠采用三种ARTs：群居繁殖者在共享巢穴中产仔并提供异亲照料，回归者暂时离开群体去产仔，独居繁殖者离开去产仔且不再回归。我们预计群居繁殖者和回归者由于群居的社会压力会有更高的皮质酮，并且睾酮水平低于独居繁殖者，因为独居繁殖者必须独自保卫领地。如预测的那样，独居繁殖者的皮质酮低于回归者和群居繁殖者，但ARTs之间的睾酮和孕酮没有差异。回归者（在离开群体之前测量）的雌激素水平高于群居和独居繁殖者，这与调节作用一致。我们的研究证明了采用（或即将采用）不同策略的雌性之间的激素差异，并为雌性中的RPH提供了首个支持。
