Feder Jeffrey L, Berlocher Stewart H, Roethele Joseph B, Dambroski Hattie, Smith James J, Perry William L, Gavrilovic Vesna, Filchak Kenneth E, Rull Juan, Aluja Martin
Department of Biological Sciences, P.O. Box 369, Galvin Life Science Center, University of Notre Dame, Notre Dame, IN 46556-0369, USA.
Proc Natl Acad Sci U S A. 2003 Sep 2;100(18):10314-9. doi: 10.1073/pnas.1730757100. Epub 2003 Aug 19.
Tephritid fruit flies belonging to the Rhagoletis pomonella sibling species complex are controversial because they have been proposed to diverge in sympatry (in the absence of geographic isolation) by shifting and adapting to new host plants. Here, we report evidence suggesting a surprising source of genetic variation contributing to sympatric host shifts for these flies. From DNA sequence data for three nuclear loci and mtDNA, we infer that an ancestral, hawthorn-infesting R. pomonella population became geographically subdivided into Mexican and North American isolates approximately 1.57 million years ago. Episodes of gene flow from Mexico subsequently infused the North American population with inversion polymorphism affecting key diapause traits, forming adaptive clines. Sometime later (perhaps +/-1 million years), diapause variation in the latitudinal clines appears to have aided North American flies in adapting to a variety of plants with differing fruiting times, helping to spawn several new taxa. Thus, important raw genetic material facilitating the adaptive radiation of R. pomonella originated in a different time and place than the proximate ecological host shifts triggering sympatric divergence.
属于苹果实蝇复合种的实蝇科果蝇存在争议，因为有人提出它们通过转移并适应新的寄主植物，在同域环境中（即没有地理隔离的情况下）发生了分化。在此，我们报告了一些证据，表明这些果蝇在同域寄主转移过程中存在一个令人惊讶的遗传变异来源。通过对三个核基因座和线粒体DNA的DNA序列数据进行分析，我们推断，大约157万年前，一个以山楂为寄主的苹果实蝇祖先种群在地理上被细分为墨西哥和北美两个隔离种群。随后，来自墨西哥的基因流事件向北美种群注入了影响关键滞育性状的倒位多态性，形成了适应性渐变群。一段时间后（可能在±100万年前），纬度渐变群中的滞育变异似乎帮助北美果蝇适应了多种结果时间不同的植物，从而促成了几个新分类群的产生。因此，促进苹果实蝇适应性辐射的重要原始遗传物质起源于与引发同域分化的直接生态寄主转移不同的时间和地点。
