Vogelweith Fanny, Moret Yannick, Thiéry Denis, Delbac Lionel, Moreau Jérôme
Johannes-Gutenberg University of Mainz, Institute of Organismic and Molecular Evolution, Behavioral Ecology and Social Evolution Group, Johannes-von-Müller-Weg 6, 55128 Mainz, Germany.
Université Bourgogne-Franche Comté, Équipe Écologie Évolutive, UMR 6282 Biogéosciences, 6 Bd Gabriel, 21000 Dijon, France.
J Insect Physiol. 2017 Oct;102:7-11. doi: 10.1016/j.jinsphys.2017.08.010. Epub 2017 Aug 24.
Immune function is a key determinant of an organism's fitness, and natural insect populations are highly variable for this trait, mainly due to environmental heterogeneity and pathogen diversity. We previously reported a positive correlation between infection prevalence by parasitoids and host immunity in natural populations of the vineyard pest Lobesia botrana. Here, we tested whether this correlation reflects a plastic adjustment of host immunity in response to the local presence of parasites. To this end, we measured immunity of non-parasitized L. botrana larvae exposed, respectively, to one of the two most common species of parasitoids in vineyards, over 6days. Larvae were able to sense the parasitoid through visual, chemical, or mechanical cues, but contact larvae-parasitoid were excluded. Contrary to our hypothesis, we found that L. botrana larvae did not increase their immune defenses in the presence of parasitoids, despite their ability to sense a potential threat. Our results therefore suggest that the positive correlation between infection prevalence by parasitoids and L. botrana immunity among natural populations may result from micro-evolutionary changes resulting from long-term local selection pressures imposed by parasitoids in wild populations rather than plastic adjustments of immunity.
免疫功能是生物体健康状况的关键决定因素，自然昆虫种群在这一特性上具有高度变异性，主要是由于环境异质性和病原体多样性。我们之前报道过，在葡萄园害虫葡萄小卷蛾（Lobesia botrana）的自然种群中，寄生蜂的感染率与宿主免疫力之间存在正相关。在此，我们测试了这种相关性是否反映了宿主免疫力对当地寄生虫存在的可塑性调整。为此，我们在6天时间里，分别测量了暴露于葡萄园两种最常见寄生蜂之一的未被寄生的葡萄小卷蛾幼虫的免疫力。幼虫能够通过视觉、化学或机械线索感知寄生蜂，但排除了幼虫与寄生蜂的接触。与我们的假设相反，我们发现葡萄小卷蛾幼虫在有寄生蜂存在的情况下并没有增强其免疫防御，尽管它们有能力感知潜在威胁。因此，我们的结果表明，在自然种群中，寄生蜂感染率与葡萄小卷蛾免疫力之间的正相关可能是野生种群中寄生蜂长期局部选择压力导致的微进化变化的结果，而不是免疫力的可塑性调整。
