Migratory Bird Center, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC 20013;
Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada.
Proc Natl Acad Sci U S A. 2020 Feb 11;117(6):2993-2999. doi: 10.1073/pnas.1913284117. Epub 2020 Jan 24.
The dynamics of social networks can determine the transmission of information, the spread of diseases, and the evolution of behavior. Despite this broad importance, a general framework for predicting social network stability has not been proposed. Here we present longitudinal data on the social dynamics of a cooperative bird species, the wire-tailed manakin, to evaluate the potential causes of temporal network stability. We find that when partners interact less frequently and when social connectedness increases, the network is subsequently less stable. Social connectivity was also negatively associated with the temporal persistence of coalition partnerships on an annual timescale. This negative association between connectivity and stability was surprising, especially given that individual manakins who were more connected also had more stable partnerships. This apparent paradox arises from a within-individual behavioral trade-off between partnership quantity and quality. Crucially, this trade-off is easily masked by behavioral variation among individuals. Using a simulation, we show that these results are explained by a simple model that combines among-individual behavioral heterogeneity and reciprocity within the network. As social networks become more connected, individuals face a trade-off between partnership quantity and maintenance. This model also demonstrates how among-individual behavioral heterogeneity, a ubiquitous feature of natural societies, can improve social stability. Together, these findings provide unifying principles that are expected to govern diverse social systems.
社交网络的动态可以决定信息的传播、疾病的扩散和行为的演变。尽管这具有广泛的重要性，但尚未提出用于预测社交网络稳定性的通用框架。在这里，我们展示了关于合作鸟类——线尾凤头雨燕的社交动态的纵向数据，以评估时间网络稳定性的潜在原因。我们发现，当伙伴之间的互动频率较低，社交联系增加时，网络随后会变得不稳定。在年度时间尺度上，社交联系也与联盟伙伴关系的时间持久性呈负相关。这种连接性和稳定性之间的负相关关系令人惊讶，尤其是考虑到与连接性更强的个体相比，个体凤头雨燕的伙伴关系更稳定。这种明显的悖论源于个体内部在伙伴关系数量和质量之间的行为权衡。至关重要的是，这种权衡很容易被个体之间的行为差异所掩盖。通过模拟，我们表明这些结果可以通过一个简单的模型来解释，该模型结合了网络内的个体间行为异质性和互惠性。随着社交网络的连接性越来越强，个体在伙伴关系数量和维护之间面临权衡。该模型还展示了自然社会中普遍存在的个体间行为异质性如何提高社交稳定性。总之，这些发现提供了统一的原则，预计这些原则将支配各种社会系统。
