Sieben Andrew J, Mihaljevic Joseph R, Shoemaker Lauren G
Department of Botany, University of Wyoming, Laramie, Wyoming, USA.
School of Medicine, Emory University, Atlanta, Georgia, USA.
Ecology. 2022 Dec;103(12):e3819. doi: 10.1002/ecy.3819. Epub 2022 Sep 29.
Pathogen coexistence depends on ecological processes operating at both within and between-host scales, making it difficult to quantify which processes may promote or prevent coexistence. Here, we propose that adapting modern coexistence theory-traditionally applied in plant communities-to pathogen systems provides an exciting approach for examining mechanisms of coexistence operating across different spatial scales. We first overview modern coexistence theory and its mechanistic decomposition; we subsequently adapt the framework to quantify how spatial variation in pathogen density, host resources and immunity, and their interaction may promote pathogen coexistence. We apply this derivation to an example two pathogen, multiscale model comparing two scenarios with generalist and strain-specific immunity: one with demographic equivalency among pathogens and one with demographic trade-offs among pathogens. We then show how host-pathogen feedbacks generate spatial heterogeneity that promote pathogen coexistence and decompose those mechanisms to quantify how each spatial heterogeneity contributes to that coexistence. Specifically, coexistence of demographically equivalent pathogens occurs due to spatial variation in host resources, immune responses, and pathogen aggregation. With a competition-colonization trade-off, the superior colonizer requires spatial heterogeneity to coexist, whereas the superior competitor does not. Finally, we suggest ways forward for linking theory and empirical tests of coexistence in disease systems.
病原体共存取决于在宿主内和宿主间尺度上起作用的生态过程，这使得难以量化哪些过程可能促进或阻止共存。在这里，我们提出将传统上应用于植物群落的现代共存理论应用于病原体系统，为研究跨不同空间尺度上的共存机制提供了一种令人兴奋的方法。我们首先概述现代共存理论及其机制分解；随后，我们调整该框架以量化病原体密度、宿主资源和免疫力的空间变化及其相互作用如何促进病原体共存。我们将此推导应用于一个双病原体多尺度模型示例，比较具有泛化免疫和菌株特异性免疫的两种情况：一种是病原体之间的人口统计学等效，另一种是病原体之间的人口统计学权衡。然后，我们展示宿主-病原体反馈如何产生促进病原体共存的空间异质性，并分解这些机制以量化每种空间异质性对共存的贡献。具体而言，人口统计学等效的病原体共存是由于宿主资源、免疫反应和病原体聚集的空间变化。在竞争-定殖权衡中，优势定殖者需要空间异质性才能共存，而优势竞争者则不需要。最后，我们提出了将疾病系统中共存的理论与实证检验联系起来的未来方向。
