Adaptive suppression of subordinate reproduction in cooperative mammals

在许多合作繁殖的动物中，每个群体中的一个占主导地位的雌性有效地垄断了繁殖，其他雌性帮助抚养她的后代。然而，在大多数动物社会中，从属的雌性有时会繁殖，在少数物种中，大多数成熟的雌性会定期繁殖。了解这些对比的原因和控制女性之间的生殖分布和生殖偏斜的程度的行为和生理机制是至关重要的，在解释合作的演变，个人的生殖策略和合作育种的人口动态。然而，虽然生殖偏斜的变化一直是行为生态学二十多年来大量研究的焦点，但还不可能解释物种之间或物种内部的从属繁殖分布。以前试图解释的频率繁殖的下属要么假设，下属的女性繁殖的优势女性给予他们生殖让步，以确保他们留在组中，并协助抚养后代或下属繁殖的优势是无法阻止他们怀孕或抚养年轻。另一种可能性，这已经得到了相对较少的关注，压制或驱逐从属的雌性会对统治者的适应性造成巨大的损失（部分原因是从属的雌性通常是它们的女儿或姐妹篇，部分原因是支配者的繁殖成功取决于居民助手的数量）而次级繁殖频率的差异是抑制次级对显性的净利益变化的结果。虽然一些相关的证据表明，这可能是这样的情况下，还没有研究测量的成本下属繁殖占主导地位的女性或已确定是否变化的净收益抑制下属影响的频率与下属繁殖或被驱逐出集团的占主导地位。到目前为止，最好的方式来调查的最终和近端机制控制生殖偏斜是操纵繁殖的频率由下属和显性，并确定这如何影响繁殖成功的显性和他们的下属的待遇。利用卡拉哈里猫鼬Suricta suricatta的现有研究群体，其中所有个体都是可识别的，并且可以获得超过15年的多个群体在生长和繁殖成功方面的个体差异的详细记录，我们将使用定量比较和实验的组合来操纵下级和显性的繁殖频率，（1）测量从属繁殖对显性的成本（2）确定抑制从属对显性的净收益的变化是否影响它们容忍从属的程度（3）确定支配者是否监控下属的成长，并有选择地将可能的挑战者驱逐出群体（4）确定支配者是否试图影响其可能的继任者的身份（5）发展广义的博弈论模型，可用于预测在何种程度上占主导地位的容忍下属，程度的生殖倾斜和规模和结构的群体在其他社会脊椎动物。

In many animals that breed cooperatively, one dominant female in each group effectively monopolises reproduction and other females help to rear her offspring. However, in most animal societies, subordinate females sometimes breed and, in a few species, most mature females breed regularly. Understanding the reasons for these contrasts and the behavioural and physiological mechanisms controlling the distribution of reproduction among females and the degree of reproductive skew is of central importance in explaining the evolution of cooperation, the reproductive strategies of individuals and the population dynamics of cooperative breeders. However, although variation in reproductive skew has been the focus of considerable research in behavioural ecology for more than twenty years, it has not yet been possible to account for the distribution of subordinate breeding either between or within species. Previous attempts to explain the frequency of breeding by subordinates 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. An alternative possibility, which has received relatively little attention, is that suppressing or evicting subordinate females has substantial costs to the fitness of dominants (partly because subordinate females are commonly their daughters or sisters and partly because the breeding success of dominants depends on the number of resident helpers) and that differences in the frequency of subordinate breeding are a consequence of variation in the net benefits of suppressing subordinates to dominants. While some correlational evidence suggests that this may be the case, no studies have yet measured the costs of subordinate breeding to dominant females or have determined whether variation in the net benefits of suppressing subordinates affects the frequency with which subordinates breed or are evicted from the group by dominants. By far the best way to investigate the ultimate and proximate mechanisms controlling reproductive skew is to manipulate the frequency of breeding by subordinates and dominants and to determine how this affects the breeding success of dominants and their treatment of subordinates. Drawing on an existing study population of Kalahari meerkats Suricta suricatta, where all individuals are recognisable and detailed records of individual differences in growth and breeding success are available for multiple groups over fifteen years, we shall use a combination of quantitative comparisons and experiments manipulating the frequency of reproduction by subordinates and dominants, to (1) measure the costs of subordinate breeding to dominants (2) determine whether variation in the net benefits of suppressing subordinates to dominants affects the extent to which they tolerate subordinates (3) determine whether dominants monitor the growth of subordinates and selectively evict likely challengers from the group (4) determine whether dominants attempt to influence the identity of their likely successors (5) develop generalised game-theory models that can be used to predict the extent to which dominants tolerate subordinates, the degree of reproductive skew and the size and structure of groups in other social vertebrates.