Fig2_code from Vector-borne parasite invasion in communities across space and time

While vector-borne parasite transmission often operates via generalist-feeding vectors facilitating cross-species transmission in host communities, theory describing the relationship between host species diversity and parasite invasion in these systems is underdeveloped. Host community composition and abundance vary across space and time, generating opportunities for parasite invasion. To explore how host community variation can modify parasite invasion potential, we develop a model for vector-borne parasite transmission dynamics that includes a host community of arbitrary richness and species' abundance. To compare invasion potential across communities, we calculate the community basic reproductive ratio of the parasite. We compare communities comprising a set of host species to their subsets, which allows for flexible scenario building including the introduction of novel host species and species loss. We allow vector abundance to scale with, or be independent of, community size, capturing regulation by feeding opportunities and non-host effects such as limited oviposition sites. Motivated by equivocal data relating host species competency to abundance, we characterize plausible host communities via phenomenological relationships between host species abundance and competency. We identify an underappreciated mechanism whereby changes to communities simultaneously alter average competency and the vector to host ratio and demonstrate that the interaction can profoundly influence invasion potential.

尽管虫媒寄生虫（vector-borne parasite）的传播通常由广食性媒介介导，进而在宿主群落中促成跨物种传播，但目前针对这类系统中宿主物种多样性与寄生虫入侵之间关系的理论研究仍较为匮乏。宿主群落的组成与丰度随空间和时间动态变化，为寄生虫入侵创造了条件。为探究宿主群落变化如何调控寄生虫入侵潜能，我们构建了包含任意物种丰富度及物种丰度的宿主群落的虫媒寄生虫传播动力学模型。为比较不同群落的入侵潜能，我们计算了该寄生虫的群落基本繁殖数（community basic reproductive ratio）。我们将包含一组宿主物种的完整群落与其子集进行对比，以此实现灵活的情景构建，可涵盖新增宿主物种及物种丧失等多种场景。我们设定媒介丰度可随群落规模缩放，或独立于群落规模变化，以此刻画取食机会介导的种群调控效应以及产卵位点受限等非宿主效应。鉴于宿主物种传播能力（host competency）与丰度之间的关联数据尚无定论，我们通过宿主物种丰度与传播能力之间的现象学关系来表征合理的宿主群落。我们发现了一个尚未被充分关注的机制：群落变化可同时改变平均传播能力与媒介-宿主比值，并证明该交互作用可对寄生虫入侵潜能产生显著影响。