INRAE, URZF, Orleans, France.
UMR CBGP, INRAE, CIRAD, IRD, Institut Agro, Université Montpellier, Montpellier, France.
Mol Ecol. 2023 Aug;32(15):4381-4400. doi: 10.1111/mec.16993. Epub 2023 May 21.
Xylosandrus crassiusculus, a fungus-farming wood borer native to Southeastern Asia, is the most rapidly spreading invasive ambrosia species worldwide. Previous studies focusing on its genetic structure suggested the existence of cryptic genetic variation in this species. Yet, these studies used different genetic markers, focused on different geographical areas and did not include Europe. Our first goal was to determine the worldwide genetic structure of this species based on both mitochondrial and genomic markers. Our second goal was to study X. crassiusculus' invasion history on a global level and identify the origins of the invasion in Europe. We used a COI and RAD sequencing design to characterize 188 and 206 specimens worldwide, building the most comprehensive genetic data set for any ambrosia beetle to date. The results were largely consistent between markers. Two differentiated genetic clusters were invasive, albeit in different regions of the world. The markers were inconsistent only for a few specimens found exclusively in Japan. Mainland USA could have acted as a source for further expansion to Canada and Argentina through stepping stone expansion and bridgehead events. We showed that Europe was only colonized by Cluster II through a complex invasion history including several arrivals from multiple origins in the native area, and possibly including bridgehead from the United States. Our results also suggested that Spain was colonized directly from Italy through intracontinental dispersion. It is unclear whether the mutually exclusive allopatric distribution of the two clusters is due to neutral effects or due to different ecological requirements.
南洋大兜虫，一种原产于东南亚的真菌养殖蛀木甲虫，是全球传播速度最快的入侵性粉状介壳虫物种。先前的研究集中在该物种的遗传结构上，表明其存在隐性遗传变异。然而，这些研究使用了不同的遗传标记，关注不同的地理区域，并且不包括欧洲。我们的首要目标是基于线粒体和基因组标记来确定该物种的全球遗传结构。我们的第二个目标是在全球范围内研究 X. crassiusculus 的入侵历史，并确定欧洲入侵的起源。我们使用 COI 和 RAD 测序设计对全球 188 个和 206 个标本进行了特征描述，构建了迄今为止任何粉状介壳虫中最全面的遗传数据集。标记之间的结果在很大程度上是一致的。两个分化的遗传群是入侵性的，尽管它们位于世界的不同地区。只有在日本发现的少数标本与标记不一致。美国大陆可能通过踏脚石扩张和桥头堡事件成为进一步向加拿大和阿根廷扩张的源头。我们表明，欧洲仅通过包括原产地区的多个来源的多次到达以及可能包括来自美国的桥头堡的复杂入侵历史，才被集群 II 殖民。我们的研究结果还表明，西班牙是通过大陆内的分散直接从意大利殖民的。目前还不清楚两个集群的互斥地理分布是由于中性效应还是由于不同的生态需求造成的。
