Department of Biology, University of Western Ontario, London, ON, Canada.
Department of Biological Sciences, Western Michigan University, Kalamazoo, MI, USA.
J Evol Biol. 2018 May;31(5):753-763. doi: 10.1111/jeb.13265. Epub 2018 Apr 11.
Parasite-host relationships create strong selection pressures that can lead to adaptation and increasing specialization of parasites to their hosts. Even in relatively loose host-parasite relationships, such as between generalist ectoparasites and their hosts, we may observe some degree of specialization of parasite populations to one of the multiple potential hosts. Salivary proteins are used by blood-feeding ectoparasites to prevent hemostasis in the host and maximize energy intake. We investigated the influence of association with specific host species on allele frequencies of salivary protein genes in Cimex adjunctus, a generalist blood-feeding ectoparasite of bats in North America. We analysed two salivary protein genes: an apyrase, which hydrolyses ATP at the feeding site and thus inhibits platelet aggregation, and a nitrophorin, which brings nitrous oxide to the feeding site, inhibiting platelet aggregation and vasoconstriction. We observed more variation at both salivary protein genes among parasite populations associated with different host species than among populations from different spatial locations associated with the same host species. The variation in salivary protein genes among populations on different host species was also greater than expected under a neutral scenario of genetic drift and gene flow. Finally, host species was an important predictor of allelic divergence in genotypes of individual C. adjunctus at both salivary protein genes. Our results suggest differing selection pressures on these two salivary protein genes in C. adjunctus depending on the host species.
寄生虫-宿主关系会产生强大的选择压力，导致寄生虫适应并对宿主越来越专门化。即使在相对松散的宿主-寄生虫关系中，例如一般的外寄生虫与其宿主之间，我们也可能观察到寄生虫种群对多个潜在宿主之一的某种程度的专门化。吸血外寄生虫利用唾液蛋白来阻止宿主止血并最大限度地摄入能量。我们研究了与特定宿主物种的关联对北美的蝙蝠通用吸血外寄生虫 Cimex adjunctus 唾液蛋白基因等位基因频率的影响。我们分析了两种唾液蛋白基因：一种是磷酸酶，它在进食部位水解 ATP，从而抑制血小板聚集，另一种是硝普啉，它将一氧化二氮带到进食部位，抑制血小板聚集和血管收缩。我们观察到与不同宿主物种相关的寄生虫种群中，这两种唾液蛋白基因的等位基因变异比与同一宿主物种相关的不同空间位置的种群中的变异更多。不同宿主物种上的种群之间的唾液蛋白基因变异也大于中性遗传漂变和基因流情景下的预期。最后，宿主物种是个体 C. adjunctus 在两种唾液蛋白基因的基因型中等位基因差异的重要预测因子。我们的结果表明，C. adjunctus 中的这两种唾液蛋白基因受到不同宿主物种的不同选择压力。
