Kriesner Peter, Hoffmann Ary A
School of BioSciences, Bio21 Institute, The University of Melbourne, Parkville, 3010, Australia.
Evolution. 2018 May 15. doi: 10.1111/evo.13506.
Wolbachia endosymbionts that are maternally inherited can spread rapidly in host populations through inducing sterility in uninfected females, but some Wolbachia infections do not influence host reproduction yet still persist. These infections are particularly interesting because they likely represent mutualistic endosymbionts, spreading by increasing host fitness. Here, we document such a spread in the wAu infection of Drosophila simulans. By establishing multiple replicate cage populations, we show that wAu consistently increased from an intermediate frequency to near fixation, representing an estimated fitness advantage of around 20% for infected females. The effective population size in the cages was estimated from SNP markers to be around a few thousand individuals, precluding large effects of genetic drift in the populations. The exact reasons for the fitness advantage are unclear but viral protection and nutritional benefits are two possibilities.
通过母系遗传的沃尔巴克氏体共生菌可通过诱导未感染雌虫不育而在宿主种群中迅速传播，但一些沃尔巴克氏体感染并不影响宿主繁殖却仍能持续存在。这些感染尤其令人感兴趣，因为它们可能代表着互利共生的内共生菌，通过提高宿主适应性来传播。在此，我们记录了在拟暗果蝇的wAu感染中的这种传播情况。通过建立多个重复的笼养种群，我们发现wAu的频率持续从中间水平增加到接近固定状态，这表明感染雌虫的适应性优势估计约为20%。根据单核苷酸多态性标记估计，笼中的有效种群大小约为几千只个体，排除了种群中遗传漂变的重大影响。适应性优势的确切原因尚不清楚，但病毒保护和营养益处是两种可能的原因。
