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Experimental evolution of virulence and associated traits in a Drosophila melanogaster – Wolbachia symbiosis
bioRxiv - Evolutionary Biology Pub Date : 2020-10-27 , DOI: 10.1101/2020.04.26.062265
David Monnin , Natacha Kremer , Caroline Michaud , Manon Villa , Hélène Henri , Emmanuel Desouhant , Fabrice Vavre

Evolutionary theory predicts that vertically transmitted symbionts are selected for low virulence, as their fitness is directly correlated to that of their host. In contrast with this prediction, the Wolbachia strain wMelPop drastically reduces its Drosophila melanogaster host lifespan at high rearing temperatures. It is generally assumed that this feature is maintained because the D. melanogaster-wMelPop symbiosis is usually not exposed to environmental conditions in which the symbiont is virulent. To test this hypothesis, we submitted wMelPop-infected D. melanogaster lines to 17 generations of experimental evolution at a high temperature, while enforcing late reproduction by artificial selection. The fly survival was measured at different time points, as well as two traits that have been proposed to be causally responsible for wMelPop virulence: its relative density and the mean number of copies of octomom, an 8-genes region of the Wolbachia genome. We hypothesised that these conditions (high temperature and late reproduction) would select for a reduced wMelPop virulence, a reduced wMelPop density, and a reduced octomom copy number. Our results indicate that density, octomom copy number and virulence are correlated to each other. However, contrary to our expectations, we could not detect any reduction in virulence during the course of evolution. We discuss the significance of our results with respect to the evolutionary causes of wMelPop virulence.

中文翻译:

果蝇-Wolbachia共生中毒力和相关性状的实验演变

进化理论预测,选择垂直传播的共生体以降低毒力,因为它们的适应性与其宿主的适应性直接相关。与该预测相反,Wolbachia菌株wMelPop在高饲养温度下会大大降低其果蝇果蝇的宿主寿命。通常认为保留此功能是因为黑腹果蝇-wMelPop共生通常不暴露于该共生体具有毒性的环境条件下。为了验证这一假设,我们在高温下将wMelPop感染的D. melanogaster品系提交到17代实验进化中,同时通过人工选择来强制后期繁殖。在不同的时间点测量了果蝇的存活率,并提出了导致wMelPop毒力的两个因果特征:它的相对密度和octomom的平均拷贝数,后者是Wolbachia基因组的8个基因区域。我们假设这些条件(高温和后期繁殖)会选择降低的wMelPop毒力,降低的wMelPop密度和降低的octomom拷贝数。我们的结果表明,密度,八倍体拷贝数和毒力相互关联。但是,与我们的预期相反,我们在进化过程中没有发现任何毒力降低。我们讨论了关于wMelPop毒力进化原因的研究结果的重要性。降低了wMelPop密度,降低了八倍拷贝数。我们的结果表明,密度,八倍体拷贝数和毒力相互关联。但是,与我们的预期相反,我们在进化过程中没有发现任何毒力降低。我们讨论了关于wMelPop毒力进化原因的研究结果的重要性。降低了wMelPop密度,降低了八倍拷贝数。我们的结果表明,密度,八倍体拷贝数和毒力相互关联。但是,与我们的预期相反,我们在进化过程中没有发现任何毒力下降。我们讨论了关于wMelPop毒力进化原因的研究结果的重要性。
更新日期:2020-10-30
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