Data from: Defense traits of larval Drosophila melanogaster exhibit genetically based tradeoffs against different species of parasitoids

Populations of Drosophila melanogaster face significant mortality risks from parasitoid wasps that use species-specific strategies to locate and survive in hosts. We tested the hypothesis that parasitoids with different strategies select for alternative host defense characteristics and in doing so contribute to the maintenance of fitness variation and produce trade-offs among traits. We characterized defense traits of Drosophila when exposed to parasitoids with different host searching behaviors (Aphaereta sp. and Leptopilina boulardi). We used host larvae with different natural alleles of the gene Dopa decarboxylase (Ddc), a gene controlling the production of dopamine and known to influence the immune response against parasitoids. Previous population genetic analyses indicate that our focal alleles are maintained by balancing selection. Genotypes exhibited a trade-off between the immune response against Aphaereta sp. and the ability to avoid parasitism by L. boulardi. We also identified a trade off between the ability to avoid parasitism by L. boulardi and larval competitive ability as indicated by differences in foraging and feeding behavior. Genotypes differed in dopamine levels potentially explaining variation in these traits. Our results highlight the potential role of parasitoid biodiversity on host fitness variation and implicate Ddc as an antagonistic pleiotropic locus influencing larval fitness traits.

黑腹果蝇（Drosophila melanogaster）种群面临来自寄生蜂的显著致死风险，这类寄生蜂会演化出物种特异性策略以定位宿主并在宿主体内存活。本研究验证了如下假说：采用不同生存策略的寄生蜂会对宿主的不同防御特征施加选择压力，进而维持宿主适合度变异，并引发性状间的权衡效应。我们以两种具有不同宿主搜寻行为的寄生蜂——阿菲丽塔蜂属物种（Aphaereta sp.）和布氏勒氏茧蜂（Leptopilina boulardi）——为实验对象，对果蝇的防御性状展开了表征分析。本研究采用了携带多巴脱羧酶（Dopa decarboxylase, Ddc）基因不同天然等位基因的宿主幼虫；该基因负责调控多巴胺的生物合成，且已被证实可影响宿主针对寄生蜂的免疫应答。此前的群体遗传学分析表明，本研究关注的这些等位基因通过平衡选择得以维持。不同基因型的果蝇在针对Aphaereta sp.的免疫应答与抵御L. boulardi寄生的能力之间呈现出性状权衡。此外，我们还发现抵御L. boulardi寄生的能力与幼虫竞争能力之间存在性状权衡，该关联可通过取食与觅食行为的差异得到印证。不同基因型个体的多巴胺水平存在差异，这或许可以解释上述性状间的变异。本研究结果凸显了寄生蜂生物多样性对宿主适合度变异的潜在调控作用，并表明Ddc基因是一个拮抗多效性位点，可调控幼虫的适合度相关性状。