Center for Infectious Disease Dynamics and Department of Biology, Huck Institute of the Life Sciences, Pennsylvania State University, University Park, PA 16802.
Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08540;
Proc Natl Acad Sci U S A. 2021 Mar 9;118(10). doi: 10.1073/pnas.2020023118.
The population structure of social species has important consequences for both their demography and transmission of their pathogens. We develop a metapopulation model that tracks two key components of a species' social system: average group size and number of groups within a population. While the model is general, we parameterize it to mimic the dynamics of the Yellowstone wolf population and two associated pathogens: sarcoptic mange and canine distemper. In the initial absence of disease, we show that group size is mainly determined by the birth and death rates and the rates at which groups fission to form new groups. The total number of groups is determined by rates of fission and fusion, as well as environmental resources and rates of intergroup aggression. Incorporating pathogens into the models reduces the size of the host population, predominantly by reducing the number of social groups. Average group size responds in more subtle ways: infected groups decrease in size, but uninfected groups may increase when disease reduces the number of groups and thereby reduces intraspecific aggression. Our modeling approach allows for easy calculation of prevalence at multiple scales (within group, across groups, and population level), illustrating that aggregate population-level prevalence can be misleading for group-living species. The model structure is general, can be applied to other social species, and allows for a dynamic assessment of how pathogens can affect social structure and vice versa.
社会物种的种群结构对它们的种群动态和病原体传播都有重要影响。我们开发了一个集合种群模型，该模型跟踪物种社会系统的两个关键组成部分：平均群体大小和种群内的群体数量。虽然该模型具有通用性，但我们对其进行了参数化处理，以模拟黄石狼群及其两种相关病原体（痒螨和犬瘟热）的动态。在没有疾病的初始情况下，我们表明群体大小主要取决于出生率和死亡率以及群体分裂形成新群体的速度。群体总数由分裂和融合的速度、环境资源以及群体间攻击的速度决定。将病原体纳入模型会减少宿主种群的数量，主要是通过减少社会群体的数量来实现。平均群体大小的反应方式更为微妙：受感染的群体规模会减小，但当疾病减少群体数量从而减少种内竞争时，未受感染的群体可能会增加。我们的建模方法允许在多个尺度上（群体内、群体间和种群水平）轻松计算流行率，这表明聚合的种群水平流行率可能对群居物种具有误导性。模型结构具有通用性，可应用于其他社会物种，并可以动态评估病原体如何影响社会结构，反之亦然。
