Data from: Flies on the move: an inherited virus mirrors Drosophila melanogaster’s elusive ecology and demography

Vertically transmitted parasites rely on their host’s reproduction for their transmission, leading to the evolutionary histories of both parties being intimately entwined. Parasites can thus serve as a population genetic magnifying glass for their host’s demographic history. Here, we study the fruitfly Drosophila melanogaster’s vertically transmitted sigma virus DMelSV. The virus has a high mutation rate and low effective population size, allowing us to reconstruct at a fine scale how the combined forces of the movement of flies and selection on the virus have shaped its migration patterns. We found that the virus is likely to have spread to Europe from Africa, mirroring the colonization route of Drosophila. The North American DMelSV population appears to be the result of a recent single immigration from Europe, invading together with its host in the late 19th century. Across Europe, DMelSV migration rates are low and populations are highly genetically structured, likely reflecting limited fly movement. Despite being intolerant of extreme cold, viral diversity suggests that fly populations can persist in harsh continental climates and that recolonisation from the warmer south plays a minor role. In conclusion, studying DMelSV can provide insights into the poorly understood ecology of D. melanogaster, one of the best-studied organisms in biology.

垂直传播寄生虫（vertically transmitted parasites）依赖宿主的繁殖完成自身传播，使得二者的演化历史紧密交织在一起。因此，寄生虫可作为解析宿主种群动态历史的群体遗传学放大镜。本研究聚焦黑腹果蝇（Drosophila melanogaster）的垂直传播西格玛病毒DMelSV。该病毒具有较高的突变率与较低的有效种群规模，使我们能够精细重构果蝇移动与病毒所受选择压力的共同作用如何塑造了其扩散模式。研究发现，该病毒极有可能从非洲传入欧洲，这与黑腹果蝇的殖民扩散路径相一致。北美DMelSV种群似乎源自近期一次从欧洲的独立入侵事件，于19世纪晚期随宿主一同传入。在欧洲范围内，DMelSV的种群扩散速率较低，种群具有高度的遗传结构，这大概率反映了果蝇的移动范围有限。尽管病毒无法耐受极端低温，但病毒的遗传多样性表明，果蝇种群能够在严酷的大陆性气候中存续，而从温暖南部的重新定植所起的作用较为有限。综上，对DMelSV的研究可为人们深入理解黑腹果蝇的生态学特征提供新视角——黑腹果蝇是生物学领域研究最为透彻的模式生物之一。