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.

病原体（Pathogens）在塑造自然群落（natural communities）的结构与动态过程中发挥着关键作用，因为不同物种对其易感程度并不一致。
生态学（ecology）与流行病学（epidemiology）的共同研究目标之一，是预测某一物种最易感染病害的时段。主流假说提出，病害的影响应随宿主丰度（host abundance）升高而增强，由此产生“稀有种优势（rare-species advantage）”。然而，病原体的影响可能与宿主丰度脱钩——由于大多数病原体能侵染多个宿主物种，会导致病原体溢出（pathogen spillover）至近缘宿主类群。
本研究表明，周边群落的系统发育与生态结构（phylogenetic and ecological structure）可作为病害压力（disease pressure）的重要预测因子。我们在草原植物群落（grassland plant community）中发现，病害造成的组织损失量随某一物种的相对丰度提升而增加，且这一稀有种优势还存在额外的系统发育维度：亲缘关系越近的物种，其所受病害压力越强。
我们基于宿主间亲缘关系构建了病原体宿主范围的全球模型，该模型可在局域尺度上稳健预测相对病害压力。
在本研究的草原群落中，总病害发生量的准确预测因子并非仅依赖目标宿主（focal host）的丰度，而是结合了群落内所有物种的丰度及其与目标宿主的系统发育距离的加权值。
此外，该模型可精准预测我们在实验样地中新引入的44个宿主物种的实测病害压力，这为解释为何系统发育上的稀有种在引入后更易成为入侵物种提供了机制性证据。
本研究结果证实，群落的系统发育与生态结构在病害动态中扮演关键角色，该发现对生物多样性（biodiversity）维持、外来杂草的生物抗性（biotic resistance）防控，以及农业（agriculture）与林业（forestry）中栽培植物的生产成效均具有重要借鉴意义。