Department of Biology, Emory University, 1510 Clifton Road, Atlanta, GA 30322, USA.
Ecol Lett. 2011 May;14(5):453-61. doi: 10.1111/j.1461-0248.2011.01604.x. Epub 2011 Mar 7.
Parasites and hosts live in communities consisting of many interacting species, but few studies have examined how communities affect parasite virulence and transmission. We studied a food web consisting of two species of milkweed, two milkweed herbivores (monarch butterfly and oleander aphid) and a monarch butterfly-specific parasite. We found that the presence of aphids increased the virulence and transmission potential of the monarch butterfly's parasite on one milkweed species. These increases were associated with aphid-induced decreases in the defensive chemicals of milkweed plants. Our experiment suggests that aphids can indirectly increase the virulence and transmission potential of monarch butterfly parasites, probably by altering the chemical composition of a shared food plant. These results indicate that species that are far removed from host-parasite interactions can alter such interactions through cascading indirect effects in the food web. As such, indirect effects within ecological communities may drive the dynamics and evolution of parasites.
寄生虫和宿主生活在由许多相互作用的物种组成的群落中，但很少有研究探讨群落如何影响寄生虫的毒力和传播。我们研究了一个由两种乳草、两种乳草食草动物（黑脉金斑蝶和夹竹桃蚜虫）和一种黑脉金斑蝶特异性寄生虫组成的食物网。我们发现，蚜虫的存在增加了一种乳草物种上黑脉金斑蝶寄生虫的毒力和传播潜力。这些增加与蚜虫诱导的乳草植物防御化学物质减少有关。我们的实验表明，蚜虫可以通过改变共享食物植物的化学成分，间接地增加黑脉金斑蝶寄生虫的毒力和传播潜力。这些结果表明，远离宿主-寄生虫相互作用的物种可以通过食物网中的级联间接效应来改变这种相互作用。因此，生态群落中的间接效应可能会驱动寄生虫的动态和进化。
