Yoon Su'ad A, Harrison Joshua G, Philbin Casey S, Dodson Craig D, Jones Danielle M, Wallace Ian S, Forister Matthew L, Smilanich Angela M
Department of Biology, Program of Ecology, Evolution, and Conservation Biology, University of Nevada Reno, Reno, NV, USA.
Department of Botany, University of Wyoming, Laramie, WY, USA.
Oecologia. 2019 Sep;191(1):141-152. doi: 10.1007/s00442-019-04480-3. Epub 2019 Aug 1.
Herbivorous insects can defend themselves against pathogens via an immune response, which is influenced by the nutritional quality and phytochemistry of the host plant. However, it is unclear how these aspects of diet interact to influence the insect immune response and what role is played by ingested foliar microbes. We examined dietary protein, phytochemistry, and the caterpillar microbiome to understand variation in immune response of the Melissa blue butterfly, Lycaeides melissa. We also asked if these factors have host plant-specific effects by measuring L. melissa immune response when reared on a recently colonized exotic host plant (Medicago sativa) as compared to the immune response on an ancestral, native host (Astragalus canadensis). L. melissa did not experience immunological benefits directly related to consumption of the novel plant M. sativa. However, we did find negative, direct effects of phytochemical diversity and negative, direct effects of diet-derived microbial diversity on constitutive immune response for caterpillars fed M. sativa, as measured by phenoloxidase activity. Foliar protein did not directly influence the immune response, but did do so indirectly by increasing weight gain. Our results highlight the important effects of host diet on caterpillar physiology and raise the possibility that foliar microbiota, despite being rapidly passed through the gut, can affect the caterpillar immune response.
植食性昆虫可以通过免疫反应来抵御病原体，而这种免疫反应会受到宿主植物的营养质量和植物化学性质的影响。然而，目前尚不清楚饮食的这些方面如何相互作用以影响昆虫的免疫反应，以及摄入的叶片微生物发挥了什么作用。我们研究了饮食中的蛋白质、植物化学性质以及毛虫的微生物群，以了解灰蝶（Lycaeides melissa）免疫反应的变化。我们还通过测量在新近定植的外来宿主植物（紫花苜蓿）上饲养的灰蝶的免疫反应，并与在祖先本土宿主（加拿大黄芪）上的免疫反应进行比较，来探究这些因素是否具有宿主植物特异性效应。灰蝶并没有从食用新植物紫花苜蓿中直接获得免疫益处。然而，我们确实发现，以紫花苜蓿为食的毛虫，其植物化学多样性对组成性免疫反应有负面的直接影响，饮食来源的微生物多样性对组成性免疫反应也有负面的直接影响，这是通过酚氧化酶活性来衡量的。叶片蛋白质并没有直接影响免疫反应，但通过增加体重间接产生了影响。我们的研究结果突出了宿主饮食对毛虫生理的重要影响，并提出了一个可能性，即叶片微生物群尽管会迅速通过肠道，但仍可能影响毛虫的免疫反应。
