Data from: Phylogenetic structure and host abundance drive disease pressure in communities

Pathogens play an important part in shaping the structure and dynamics of natural communities, because species are not affected by them equally. A shared goal of ecology and epidemiology is to predict when a species is most vulnerable to disease. A leading hypothesis asserts that the impact of disease should increase with host abundance, producing a ‘rare-species advantage. However, the impact of a pathogen may be decoupled from host abundance, because most pathogens infect more than one species, leading to pathogen spillover onto closely related species. Here we show that the phylogenetic and ecological structure of the surrounding community can be important predictors of disease pressure. We found that the amount of tissue lost to disease increased with the relative abundance of a species across a grassland plant community, and that this rare-species advantage had an additional phylogenetic component: disease pressure was stronger on species with many close relatives. We used a global model of pathogen sharing as a function of relatedness between hosts, which provided a robust predictor of relative disease pressure at the local scale. In our grassland, the total amount of disease was most accurately explained not by the abundance of the focal host alone, but by the abundance of all species in the community weighted by their phylogenetic distance to the host. Furthermore, the model strongly predicted observed disease pressure for 44 novel host species we introduced experimentally to our study site, providing evidence for a mechanism to explain why phylogenetically rare species are more likely to become invasive when introduced. Our results demonstrate how the phylogenetic and ecological structure of communities can have a key role in disease dynamics, with implications for the maintenance of biodiversity, biotic resistance against introduced weeds, and the success of managed plants in agriculture and forestry.

病原物在塑造自然群落的结构与动态过程中发挥着关键作用，因为不同物种受其影响的程度并不均等。生态学与流行病学的共同目标之一，便是预测何种物种最易感染病害。主流假说认为，病害的影响应随宿主丰度升高而增强，由此产生“稀有种优势（rare-species advantage）”。然而，病原物的影响可能与宿主丰度脱耦，因为多数病原物可侵染多个物种，进而引发病原物向近缘物种的溢出效应。本研究表明，周边群落的系统发育与生态结构可作为病害压力的重要预测因子。我们在草原植物群落中发现，病害导致的组织损失量随物种相对丰度升高而增加，且该稀有种优势还存在额外的系统发育维度：拥有较多近缘物种的类群面临的病害压力更强。我们构建了以宿主间亲缘关系为自变量的病原物跨宿主共享全局模型，该模型可在局域尺度上可靠预测相对病害压力。在本研究的草原群落中，病害总发生量最准确的预测因子并非仅依赖于目标宿主的丰度，而是群落中所有物种的丰度与其与目标宿主的系统发育距离加权后的综合值。此外，该模型可精准预测我们在实验样地中引入的44个新宿主物种的实测病害压力，为解释系统发育稀有种在引入后更易成功入侵的机制提供了实证依据。本研究结果表明，群落的系统发育与生态结构在病害动态中发挥着关键作用，该发现对生物多样性维持、外来杂草的生物抗性防控，以及农林生产中栽培植物的定植成功率均具有重要启示。