Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, UK.
J Evol Biol. 2020 Nov;33(11):1625-1633. doi: 10.1111/jeb.13702. Epub 2020 Sep 25.
When a parasite attacks an insect, the outcome is commonly modulated by the presence of defensive heritable symbionts residing within the insect host. Previous studies noted markedly different strengths of Spiroplasma-mediated fly survival following attack by the same strain of wasp. One difference between the two studies was the strain of Spiroplasma used. We therefore performed a laboratory experiment to assess whether Spiroplasma-mediated protection depends upon the strain of Spiroplasma. We perform this analysis using the two strains of male-killing Spiroplasma used previously, and examined response to challenge by two strains of Leptopilina boulardi and two strains of Leptopilina heterotoma wasp. We found no evidence Spiroplasma strain affected fly survival following wasp attack. In contrast, analysis of the overall level of protection, including the fecundity of survivors of wasp attack, did indicate the two Spiroplasma strains tested varied in protective efficiency against three of the four wasp strains tested. These data highlight the sensitivity of symbiont-mediated protection phenotypes to laboratory conditions, and the importance of common garden comparison. Our results also indicate that Spiroplasma strains can vary in protective capacity in Drosophila, but these differences may exist in the relative performance of survivors of wasp attack, rather than in survival of attack per se.
当寄生虫攻击昆虫时，昆虫体内防御性遗传共生体的存在通常会调节其结果。先前的研究注意到，在被同一种黄蜂攻击后，变形菌介导的苍蝇存活率有明显不同的强度。这两项研究的一个区别是使用的变形菌菌株不同。因此，我们进行了一项实验室实验，以评估变形菌介导的保护是否取决于变形菌菌株。我们使用以前使用的两种雄性致死性变形菌菌株进行了这项分析，并检查了对两种 Leptopilina boulardi 和两种 Leptopilina heterotoma 黄蜂菌株的挑战的反应。我们没有发现变形菌菌株影响黄蜂攻击后苍蝇存活率的证据。相比之下，对整体保护水平（包括黄蜂攻击幸存者的繁殖力）的分析表明，在所测试的四种黄蜂菌株中，有三种测试的两种变形菌菌株的保护效率不同。这些数据突出表明，共生体介导的保护表型对实验室条件非常敏感，并且需要进行常见园林比较。我们的结果还表明，变形菌菌株在果蝇中可能在保护能力上存在差异，但这些差异可能存在于黄蜂攻击幸存者的相对表现中，而不是攻击本身的存活率。
