Davis Staige E, Malfi Rosemary L, Roulston T'ai H
Department of Environmental Sciences, University of Virginia, 291 McCormick Road, Charlottesville, VA, 22904, USA.
Oecologia. 2015 Aug;178(4):1017-32. doi: 10.1007/s00442-015-3292-8. Epub 2015 Mar 21.
Endoparasitoids develop inside the body of a host organism and, if successful, eventually kill their host in order to reach maturity. Host species can vary in their suitability for a developing endoparasitoid; in particular, the host immune response, which can suppress egg hatching and larval development, has been hypothesized to be one of the most important determinants of parasitoid host range. In this study, we investigated whether three bumblebee host species (Bombus bimaculatus, Bombus griseocollis, and Bombus impatiens) varied in their suitability for the development of a shared parasitoid, the conopid fly (Conopidae, Diptera) and whether the intensity of host encapsulation response, an insect immune defense against invaders, could predict parasitoid success. When surgically implanted with a nylon filament, B. griseocollis exhibited a stronger immune response than both B. impatiens and B. bimaculatus. Similarly, B. griseocollis was more likely to melanize conopid larvae from natural infections and more likely to kill conopids prior to its own death. Our results indicate that variation in the strength of the general immune response of insects may have ecological implications for sympatric species that share parasites. We suggest that, in this system, selection for a stronger immune response may be heightened by the pattern of phenological overlap between local host species and the population peak of their most prominent parasitoid.
内寄生蜂在宿主生物体内发育，如果成功，最终会杀死宿主以达到成熟。宿主物种对发育中的内寄生蜂的适宜性可能各不相同；特别是，宿主免疫反应可抑制卵孵化和幼虫发育，据推测这是寄生蜂宿主范围的最重要决定因素之一。在本研究中，我们调查了三种熊蜂宿主物种（二斑熊蜂、灰颈熊蜂和凤蝶熊蜂）对一种共享寄生蜂——食虫虻（双翅目，食虫虻科）发育的适宜性是否存在差异，以及宿主包囊反应的强度（一种针对入侵者的昆虫免疫防御）是否能够预测寄生蜂的成功。当通过手术植入尼龙丝时，灰颈熊蜂比凤蝶熊蜂和二斑熊蜂表现出更强的免疫反应。同样，灰颈熊蜂更有可能使自然感染的食虫虻幼虫黑化，并且更有可能在自身死亡之前杀死食虫虻。我们的结果表明，昆虫一般免疫反应强度的差异可能对共享寄生虫的同域物种具有生态影响。我们认为，在这个系统中，当地宿主物种与其最主要寄生蜂的种群高峰期之间的物候重叠模式可能会加剧对更强免疫反应的选择。
