Partitioning the net effect of host diversity on an emerging amphibian pathogen

The ‘dilution effect’ (DE) hypothesis predicts that diverse host communities will show reduced disease. The underlying causes of pathogen dilution are complex, because they involve non-additive (driven by host interactions and differential habitat use) and additive (controlled by host species composition) mechanisms. Here, we used measures of complementarity and selection traditionally employed in the field of biodiversity–ecosystem function (BEF) to quantify the net effect of host diversity on disease dynamics of the amphibian-killing fungus Batrachochytrium dendrobatidis (Bd). Complementarity occurs when average infection load in diverse host assemblages departs from that of each component species in uniform populations. Selection measures the disproportionate impact of a particular species in diverse assemblages compared with its performance in uniform populations, and therefore has strong additive and non-additive properties. We experimentally infected tropical amphibian species of ...“稀释效应（dilution effect，DE）假说”预测，宿主群落多样性越高，其疾病发生程度越低。病原体稀释的潜在机制较为复杂，既涉及非加性机制（由宿主相互作用与差异化生境利用驱动），也包含加性机制（由宿主物种组成决定）。本研究采用生物多样性-生态系统功能（biodiversity–ecosystem function, BEF）领域传统使用的互补效应与选择效应指标，量化宿主多样性对杀两栖动物真菌蛙壶菌（Batrachochytrium dendrobatidis, Bd）病害动态的净效应。其中，互补效应指多宿主组合的平均感染负荷与各单物种种群的平均感染负荷存在差异；选择效应则衡量某一物种在多宿主组合中的不成比例影响，相较于其在单物种种群中的表现，因此兼具显著的加性与非加性特性。我们对热带两栖动物物种开展了实验感染……