Data from: Population density, not host competence, drives patterns of disease in an invaded community

Generalist parasites can strongly influence interactions between native and invasive species. Host competence can be used to predict how an invasive species will affect community disease dynamics; the addition of a highly competent, invasive host is predicted to increase disease. However, densities of invasive and native species can also influence the impacts of invasive species on community disease dynamics. We examined whether information on host competence alone could be used to accurately predict the effects of an invasive host on disease in native hosts. We first characterized the relative competence of an invasive species and a native host species to a native parasite. Next, we manipulated species composition in mesocosms and found that host competence results did not accurately predict community dynamics. While the invasive host was more competent than the native, the presence of the native (lower competence) host increased disease in the invasive (higher competence) host. To identify potential mechanisms driving these patterns, we analyzed a two-host, one-parasite model parameterized for our system. Our results demonstrate that patterns of disease were primarily driven by relative population densities, mediated by asymmetry in intra- and interspecific competition. Thus, information on host competence alone may not accurately predict how an invasive species will influence disease in native species.

泛宿主寄生虫（generalist parasite）可显著影响本地物种与入侵物种之间的相互作用。宿主感受性（host competence）可用于预测入侵物种对群落疾病动态的影响：研究预测，引入高感受性的入侵宿主会加剧疾病传播。然而，入侵物种与本地物种的种群密度同样会调控入侵物种对群落疾病动态的作用效果。本研究旨在探究仅依靠宿主感受性信息，是否能够准确预测入侵宿主对本地宿主疾病的影响。我们首先针对一种本地寄生虫，分别测定了入侵宿主与本地宿主的相对感受性。随后，我们通过中宇宙实验体系（mesocosms）调控群落物种组成，结果发现基于宿主感受性的预测结果无法准确匹配群落疾病动态。尽管入侵宿主的感受性高于本地宿主，但本地（低感受性）宿主的存在反而提升了入侵（高感受性）宿主的疾病感染水平。为阐明驱动该观测结果的潜在机制，我们针对本研究体系构建了参数化的双宿主-单寄生虫模型并开展分析。研究结果表明，疾病动态主要由种群相对密度驱动，而该作用又受到种内与种间竞争不对称性的调控。因此，仅依靠宿主感受性信息，或无法准确预测入侵物种对本地宿主疾病的影响。