Data from: Worldwide population genetic structure of the oriental fruit moth (Grapholita molesta), a globally invasive pest

Background: Invasive pest species have large impacts on agricultural crop yields, and understanding their population dynamics is important for ensuring food security. The oriental fruit moth Grapholita molesta is a cosmopolitan pest of stone and pome fruit species including peach and apple, and historical records indicate that it has invaded North and South America, Europe, Australia and Africa from its putative native range in Asia over the past century. Results: We used 13 microsatellite loci, including nine newly developed markers, to characterize global population structure of G. molesta. Approximately 15 individuals from each of 26 globally distributed populations were genotyped. A weak but significant global pattern of isolation-by-distance was found, and G. molesta populations were geographically structured on a continental scale. Evidence does not support that G. molesta was introduced to North America from Japan as previously proposed. However, G. molesta was probably introduced from North America to The Azores, South Africa, and Brazil, and from East Asia to Australia. Shared ancestry was inferred between populations from Western Europe and from Brazil, although it remains unresolved whether an introduction occurred from Europe to Brazil, or vice versa. Both genetic diversity and levels of inbreeding were surprisingly high across the range of G. molesta and were not higher or lower overall in introduced areas compared to native areas. There is little evidence for multiple introductions to each continent (except in the case of South America), or for admixture between populations from different origins. Conclusions: Cross-continental introductions of G. molesta appear to be infrequent, which is surprising given its rapid worldwide expansion over the past century. We suggest that area-wide spread via transport of fruits and other plant materials is a major mechanism of ongoing invasion, and management efforts should therefore target local and regional farming communities and distribution networks.

研究背景：入侵害虫物种对农作物产量造成显著负面影响，解析其种群动态对保障粮食安全具有重要意义。梨小食心虫（Grapholita molesta）是一类广泛为害核果类与梨果类作物（涵盖桃、苹果等）的广布性害虫，历史记录显示，在过去一个世纪间，该虫从其推测的亚洲原生分布区扩散至南北美洲、欧洲、澳洲及非洲。

研究结果：本研究利用13个微卫星位点（microsatellite loci），其中包含9个新开发的分子标记，对梨小食心虫的全球种群结构进行了表征。对全球26个采样种群的约15头个体开展了基因分型。研究发现了微弱但显著的全球距离隔离（isolation-by-distance）模式，梨小食心虫种群在大陆尺度上呈现地理结构分化。现有证据不支持此前提出的“梨小食心虫从日本传入北美”的假说。然而，梨小食心虫大概率是从北美传入亚速尔群岛、南非与巴西，以及从东亚传入澳洲。研究推断西欧种群与巴西种群存在共享祖先谱系，但目前仍无法明确究竟是欧洲向巴西引入种群，还是反之。在该虫的整个分布范围内，遗传多样性与近交水平均出乎意料地高，且入侵区与原生区的整体水平并无显著差异。几乎没有证据表明各大陆存在多次引入事件（南美大陆除外），也未发现不同起源种群间存在基因混合现象。

研究结论：尽管梨小食心虫在过去一个世纪内实现了全球范围的快速扩散，但跨大陆的引入事件似乎并不频繁，这一结果颇为出人意料。本研究认为，通过果品及其他植物材料运输实现的区域间扩散是当前入侵过程的主要途径，因此防控工作应聚焦于地方及区域农业社区与流通网络。