Data for: Non-host species reduce parasite infection in a focal host species within experimental fish communities

AbstractThe dilution effect describes the negative association between host biodiversity and the risk of infectious disease. Tests designed to understand the relative roles of host species richness, host species identity, and rates of exposure within experimental host communities would help resolve ongoing contention regarding the importance and generality of dilution effects. We exposed fathead minnows to infective larvae of the trematode, Ornithodiplostomum ptychocheilus in minnow-only containers and in mixed containers that held 1-3 other species of fish. Parasite infection was estimated as the numbers of encysted worms (i.e., brainworms) present in minnows following exposure. The results of exposure trials showed that non-minnow fish species were incompatible with O. ptychocheilus larvae. There was no reduction in mean brainworm counts in minnows in mixed containers with brook sticklebacks or longnose dace. In contrast, brainworm counts in minnows declined by 51% and 27% in mesocosms and aquaria, respectively, when they co-occurred with emerald shiners. Dilution within minnow + shiner containers may arise from shiner-induced alterations in minnow or parasite behaviours that reduced encounter rates between minnows and parasite larvae. Alternatively, shiners may act as parasite sinks for parasite larvae. These results highlight the role of host-species identity in the dilution effect. Our results also emphasize the complex and idiosyncratic effects of host community composition on rates of parasite infection within contemporary host communities that contain combinations of introduced and native species.摘要：稀释效应（dilution effect）指宿主生物多样性与传染病感染风险之间的负相关关联。旨在厘清宿主物种丰富度、宿主物种特性（host species identity）以及实验宿主群落内暴露率相对作用的相关测试，将有助于解决当前围绕稀释效应的重要性与普适性的持续争议。 本研究将胖头鱥（fathead minnows）暴露于吸虫纲（trematode）奥氏双穴吸虫（Ornithodiplostomum ptychocheilus）的感染性幼虫中，实验设置了两类饲养容器：仅含胖头鱥的单一物种容器，以及包含1~3种其他鱼类的混合物种容器。以暴露后胖头鱥体内包囊蠕虫（即脑蠕虫，brainworms）的数量评估寄生虫感染情况。 暴露实验结果显示，非胖头鱥鱼类对该吸虫幼虫不具备感染兼容性。当混合容器中饲养有溪流刺鱼（brook sticklebacks）或长鼻雅罗鱼（longnose dace）时，胖头鱥体内的脑蠕虫数量均值未出现显著下降。与之形成鲜明对比的是，当胖头鱥与翡翠闪鳞鱼（emerald shiners）共存时，中型实验生态系统（mesocosms）与水族箱（aquaria）内胖头鱥的脑蠕虫数量分别下降了51%与27%。 胖头鱥与闪鳞鱼混合容器内出现的稀释效应，可能源于闪鳞鱼诱导的胖头鱥或寄生虫行为改变，降低了胖头鱥与寄生虫幼虫的接触率；或者，闪鳞鱼亦可作为寄生虫幼虫的宿主汇（parasite sinks）。 上述研究结果凸显了宿主物种特性在稀释效应中的核心作用。同时，本研究强调，在包含外来物种与本地物种组合的当代宿主群落中，宿主群落组成对寄生虫感染率存在复杂且具物种特异性的影响。