Despite the importance of population structures throughout ecology, relatively little theoretical attention has been paid to understanding the implications of social groups for population dynamics. The dynamics of socially structured populations differ substantially from those of unstructured or metapopulation-structured populations, because social groups themselves may split, fuse, and compete. These “between-group processes” remain understudied as drivers of the dynamics of socially structured populations. Here, we explore the role of various between-group processes in the dynamics of socially structured populations. To do so, we analyze a model that includes births, deaths, migration, fissions, fusions, and between-group competition and flexibly allows for density dependence in each process. Both logistic growth and an Allee effect are considered for within-group density dependence. We show that the effect of various between-group processes is mediated by their influence on the stable distribution of group sizes, with the ultimate impact on the population determined by the interaction between within-group density dependence and the process's effect on the group size distribution. Between-group interactions that change the number of groups can lead to both negative and positive density dependence at the global population level (even if birth and death rates depend only on group size and not population size). We conclude with a series of case studies that illustrates different ways that age, sex, and class structure impact the dynamics of social populations. These case studies demonstrate the importance of group-formation mechanisms, the cost of having excess males in a group, and the potential drawbacks of generating too many reproductive individuals. In sum, our results make clear the importance of within-group density dependence, between-group dynamics, and the interactions between them for the population dynamics of social species and provide a flexible framework for modeling social populations.

中文翻译：

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社会人口动态的灵活理论：群体内密度依赖性和群体间过程

尽管人口结构在整个生态学中很重要，但人们对理解社会群体对人口动态的影响的理论关注相对较少。社会结构人口的动态与非结构或集合人口结构的人口动态有很大不同，因为社会群体本身可能分裂、融合和竞争。这些“群体间过程”作为社会结构人口动态的驱动因素仍然没有得到充分研究。在这里，我们探讨了各种群体间过程在社会结构人口动态中的作用。为此，我们分析了一个模型，其中包括出生、死亡、迁移、裂变、融合和群体间竞争，并灵活地允许每个过程中的密度依赖。逻辑增长和 Allee 效应均被视为组内密度依赖性。我们表明，各种群体间过程的影响是通过其对群体规模稳定分布的影响来调节的，对群体的最终影响是由群体内密度依赖性和过程对群体规模分布的影响之间的相互作用决定的。改变群体数量的群体间相互作用可能导致全球人口水平上的负密度依赖性和正密度依赖性（即使出生率和死亡率仅取决于群体规模而不取决于人口规模）。最后，我们通过一系列案例研究来说明年龄、性别和阶层结构影响社会人口动态的不同方式。这些案例研究证明了群体形成机制的重要性、群体中雄性过多的成本以及产生过多繁殖个体的潜在缺点。总之，我们的结果明确了群体内密度依赖性、群体间动态以及它们之间的相互作用对于社会物种种群动态的重要性，并为社会种群建模提供了灵活的框架。