Adaptive suppression of subordinate reproduction in cooperative mammals

本项目将研究合作繁殖的哺乳动物中雌性繁殖成功差异的进化过程和生理机制。先前的研究要么假设从属的雌性在优势雌性给予它们生殖让步以确保它们留在群体中并帮助抚养后代的地方繁殖，要么假设从属的雌性在优势雌性无法阻止它们怀孕或抚养后代的地方繁殖。然而，他们在解释从属生殖在物种内或物种间的分布方面取得了有限的成功。我们将检验另一种假设，即从属雌性繁殖的频率之所以变化，是因为统治者根据从属繁殖的可能成本和收益的变化，调整了它们抑制从属繁殖的程度。在现有的喀拉哈里狐獴研究种群中，已经有了大量个体样本的完整生活史记录，该项目将结合使用新的实验，包括控制从属和优势雌性的繁殖，并对现有数据进行定量分析，以(1)通过阻止群体样本中的从属繁殖来衡量从属繁殖对优势雌性的成本；(2)确定当从属繁殖对自己的繁殖可能造成的成本时，优势是否能容忍下属的存在或繁殖尝试通过阻止优势物种繁殖并检查这如何影响它们对下属雌性和后代的待遇，成功是很低的(3)确定优势物种是否监控下属的生长并抑制体重接近它们的个体的生长或(4)试图通过选择性地驱逐在等级中直接低于它们的远亲雌性（贝塔雌性）来操纵其继任者的身份。最后，我们将开发新的博弈论模型，该模型基于对压制或驱逐下属的成本和收益的现实估计，可用于预测其他合作繁殖者中下属繁殖的频率和群体结构。

This project will investigate the evolutionary processes and physiological mechanisms underlying variation in reproductive success among females in mammals that breed cooperatively. Previous studies have either assumed that subordinate females breed where dominant females grant them reproductive concessions to ensure that they remain in the group and assist in rearing their offspring or that subordinates breed where dominants are incapable of preventing them from conceiving or rearing young. However, they have had limited success in explaining the distribution of subordinate reproduction within or across species. We shall test the alternative hypothesis that the frequency with which subordinate females breed varies because dominants adjust the extent to which they suppress subordinate reproduction in relation to variation in the likely costs and benefits of subordinate breeding to their own fitness. In an existing study population of Kalahari meerkats Suricata suricatta, where full life-history records are already available for large samples of individuals, the project will use a combination of novel experiments involving the manipulation of reproduction by subordinate and dominant females and quantitative analyses of existing data to (1) measure the costs of subordinate breeding to dominant females by preventing subordinates from breeding in a sample of groups and (2) determine whether the extent to which dominants tolerate the presence or breeding attempts of subordinates when the likely costs of subordinate reproduction to their own breeding success are low by preventing dominants from breeding and examining how this affects their treatment of subordinate females and their offspring (3) determine whether dominants monitor the growth of subordinates and suppress the growth of individuals close to them in weight or (4) attempt to manipulate the identity of their successors by selectively evicting distantly related females immediately below them in the hierarchy (beta females). Finally, we shall develop novel game-theoretical models based on realistic estimates of the costs and benefits of suppressing or evicting subordinates to dominants that can be used to predict the frequency of subordinate reproduction and the structure of groups in other cooperative breeders.