Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, 06269, USA.
Department of Biological Sciences, North Carolina State University, Morehead City, NC, 28557, USA.
Oecologia. 2024 Feb;204(2):317-325. doi: 10.1007/s00442-023-05409-7. Epub 2023 Jun 30.
Parasitic infections are a global occurrence and impact the health of many species. Coinfections, where two or more species of parasite are present in a host, are a common phenomenon across species. Coinfecting parasites can interact directly or indirectly via their manipulation of (and susceptibility to) the immune system of their shared host. Helminths, such as the cestode Schistocephalus solidus, are well known to suppress immunity of their host (threespine stickleback, Gasterosteus aculeatus), potentially facilitating other parasite species. Yet, hosts can evolve a more robust immune response (as seen in some stickleback populations), potentially turning facilitation into inhibition. Using wild-caught stickleback from 20 populations with non-zero S. solidus prevalence, we tested an a priori hypothesis that S. solidus infection facilitates infection by other parasites. Consistent with this hypothesis, individuals with S. solidus infections have 18.6% higher richness of other parasites compared to S. solidus-uninfected individuals from the same lakes. This facilitation-like trend is stronger in lakes where S. solidus is particularly successful but is reversed in lakes with sparse and smaller cestodes (indicative of stronger host immunity). These results suggest that a geographic mosaic of host-parasite co-evolution might lead to a mosaic of between-parasite facilitation/inhibition effects.
寄生虫感染是一种全球性现象，影响着许多物种的健康。在宿主中同时存在两种或两种以上寄生虫的混合感染是一种常见的现象。寄生的寄生虫可以通过操纵（和对免疫系统的敏感性）它们共享宿主的免疫系统直接或间接相互作用。像绦虫 Schistocephalus solidus 这样的寄生虫，众所周知会抑制宿主的免疫力（三刺鱼，Gasterosteus aculeatus），这可能会促进其他寄生虫的感染。然而，宿主可以进化出更强壮的免疫反应（如在一些刺鱼种群中所见），从而将促进作用转变为抑制作用。使用来自 20 个种群的野生捕获的刺鱼，这些种群的 S. solidus 感染率不为零，我们检验了一个先验假设，即 S. solidus 感染会促进其他寄生虫的感染。与这一假设一致的是，与来自同一湖泊的未感染 S. solidus 的个体相比，感染 S. solidus 的个体的其他寄生虫丰富度高 18.6%。这种类似于促进的趋势在 S. solidus 特别成功的湖泊中更强，但在 S. solidus 稀疏和较小的（表明宿主免疫力较强）的湖泊中则相反。这些结果表明，宿主-寄生虫共同进化的地理镶嵌可能导致寄生虫之间促进/抑制作用的镶嵌模式。
