Department of Forest and Soil Sciences, BOKU, University of Natural Resources and Life Sciences Vienna, Vienna, Austria.
Department of Biology, IFM, University of Linköping, Linköping, Sweden.
Mol Ecol. 2019 Oct;28(20):4648-4666. doi: 10.1111/mec.15239. Epub 2019 Oct 13.
Elucidating the mechanisms and conditions facilitating the formation of biodiversity are central topics in evolutionary biology. A growing number of studies imply that divergent ecological selection may often play a critical role in speciation by counteracting the homogenising effects of gene flow. Several examples involve phytophagous insects, where divergent selection pressures associated with host plant shifts may generate reproductive isolation, promoting speciation. Here, we use ddRADseq to assess the population structure and to test for host-related genomic differentiation in the European cherry fruit fly, Rhagoletis cerasi (L., 1758) (Diptera: Tephritidae). This tephritid is distributed throughout Europe and western Asia, and has adapted to two different genera of host plants, Prunus spp. (cherries) and Lonicera spp. (honeysuckle). Our data imply that geographic distance and geomorphic barriers serve as the primary factors shaping genetic population structure across the species range. Locally, however, flies genetically cluster according to host plant, with consistent allele frequency differences displayed by a subset of loci between Prunus and Lonicera flies across four sites surveyed in Germany and Norway. These 17 loci display significantly higher F values between host plants than others. They also showed high levels of linkage disequilibrium within and between Prunus and Lonicera flies, supporting host-related selection and reduced gene flow. Our findings support the existence of sympatric host races in R. cerasi embedded within broader patterns of geographic variation in the fly, similar to the related apple maggot, Rhagoletis pomonella, in North America.
阐明促进生物多样性形成的机制和条件是进化生物学的核心课题。越来越多的研究表明，趋异生态选择通常通过抵消基因流的同质化效应而在物种形成中起着关键作用。有几个例子涉及植食性昆虫，与寄主植物转移相关的趋异选择压力可能产生生殖隔离，从而促进物种形成。在这里，我们使用 ddRADseq 来评估欧洲樱桃实蝇 Rhagoletis cerasi（L.，1758）（双翅目：瘿蚊科）的种群结构，并测试与宿主相关的基因组分化。这种瘿蚊分布在整个欧洲和西亚，并已适应两种不同的寄主植物属，李属（樱桃）和忍冬属（忍冬）。我们的数据表明，地理距离和地貌障碍是塑造物种分布范围内遗传种群结构的主要因素。然而，在局部地区，根据寄主植物，苍蝇在遗传上聚类，在德国和挪威四个调查地点的李属和忍冬属苍蝇之间，有一组特定的基因座显示出一致的等位基因频率差异。这 17 个基因座在寄主植物之间的 F 值显著高于其他基因座。它们还显示出李属和忍冬属苍蝇之间以及内部的高度连锁不平衡，支持与宿主相关的选择和减少基因流。我们的研究结果支持在欧洲樱桃实蝇中存在与宿主相关的同域种系，这与北美相关的苹果实蝇 Rhagoletis pomonella 中存在的更广泛的地理变异模式相似。
