Marino John A, Holland Manja P, Werner Earl E
Department of Ecology and Evolutionary Biology,2019 Kraus Natural Sciences Building,830 North University Ave.,University of Michigan,Ann Arbor,MI 48109,USA.
Parasitology. 2017 May;144(6):801-811. doi: 10.1017/S0031182016002547. Epub 2017 Jan 11.
Parasites can influence host population dynamics, community composition and evolution. Prediction of these effects, however, requires an understanding of the influence of ecological context on parasite distributions and the consequences of infection for host fitness. We address these issues with an amphibian - trematode (Digenea: Echinostomatidae) host-parasite system. We initially performed a field survey of trematode infection in first (snail) and second (larval green frog, Rana clamitans) intermediate hosts over 5 years across a landscape of 23 ponds in southeastern Michigan. We then combined this study with a tadpole enclosure experiment in eight ponds. We found echinostomes in all ponds during the survey, although infection levels in both snails and amphibians differed across ponds and years. Echinostome prevalence (proportion of hosts infected) in snails also changed seasonally depending on host species, and abundance (parasites per host) in tadpoles depended on host size and prevalence in snails. The enclosure experiment demonstrated that infection varied at sites within ponds, and tadpole survival was lower in enclosures with higher echinostome abundance. The observed effects enhance our ability to predict when and where host-parasite interactions will occur and the potential fitness consequences of infection, with implications for population and community dynamics, evolution and conservation.
寄生虫能够影响宿主种群动态、群落组成及进化。然而，要预测这些影响，就需要了解生态环境对寄生虫分布的影响以及感染对宿主适合度的后果。我们利用一个两栖动物 - 吸虫（复殖目：棘口科）宿主 - 寄生虫系统来解决这些问题。我们最初在密歇根州东南部23个池塘的区域内，对第一中间宿主（蜗牛）和第二中间宿主（绿蛙幼体，绿蛙）的吸虫感染情况进行了为期5年的实地调查。然后，我们将这项研究与在8个池塘中进行的蝌蚪围隔实验相结合。在调查期间，我们在所有池塘中都发现了棘口吸虫，尽管蜗牛和两栖动物的感染水平在不同池塘和年份有所不同。蜗牛体内棘口吸虫的感染率（被感染宿主的比例）也会因宿主物种不同而随季节变化，蝌蚪体内的感染强度（每个宿主的寄生虫数量）则取决于宿主大小和蜗牛的感染率。围隔实验表明，池塘内不同地点的感染情况存在差异，棘口吸虫感染强度较高的围隔中蝌蚪的存活率较低。这些观察结果增强了我们预测宿主 - 寄生虫相互作用何时何地会发生以及感染可能对适合度产生何种后果的能力，这对种群和群落动态、进化及保护都具有重要意义。
