Data from: Inferences on population history of a seed chalcid wasp: invasion success despite a severe founder effect from an unexpected source population

Most invasive species established in Europe originate from either Asia or North America, but little is currently known about the potential of the Anatolian Peninsula (Asia Minor) and/or the Near East to constitute invasion sources. Mediterranean forests are generally fragile ecosystems that can be threatened by invasive organisms coming from different regions of the Mediterranean Basin, but for which historical data are difficult to gather and the phylogeographic patterns are still poorly understood for most terrestrial organisms. In this study, we characterized the genetic structure of Megastigmus schimitscheki, an invasive seed-feeding insect species originating from the Near East, and elucidated its invasion route in Southeastern France in the mid 1990’s. To disentangle the evolutionary history of this introduction, we gathered samples from the main native regions (Taurus Mountains in Turkey, Lebanon and Cyprus) and from the invaded region, that we genotyped using five microsatellite markers and for which we sequenced the mitochondrial Cytochrome Oxidase I gene. We applied a set of population genetic statistics and methods, including approximate Bayesian computation. We proposed a detailed phylogeographic pattern for the Near East populations, and we unambiguously showed that the French invasive populations originated from Cyprus, although the available historical data strongly suggested that Turkey could be the most plausible source area. Interestingly, we could show that the introduced populations were founded from an extremely restricted number of individuals that realized a host switch from Cedrus brevifolia to C. atlantica. Evolutionary hypotheses are discussed to account for this unlikely scenario.

目前在欧洲成功定殖的多数入侵物种均源自亚洲或北美洲，但学界对安纳托利亚半岛（Anatolian Peninsula，又称小亚细亚 Asia Minor）及/或近东作为入侵源的潜力仍知之甚少。地中海森林属于典型的脆弱生态系统，易受来自地中海盆地不同区域的入侵生物威胁，但由于历史数据难以搜集，多数陆生生物的系统地理格局仍未得到充分解析。本研究以源自近东的入侵性食籽昆虫Megastigmus schimitscheki为研究对象，解析其遗传结构，并阐明其于20世纪90年代中期在法国东南部的入侵路径。为厘清该物种的入侵演化历史，我们从其主要原生分布区（土耳其托罗斯山脉、黎巴嫩及塞浦路斯）以及入侵区域采集样本，利用5个微卫星标记（microsatellite markers）对样本进行基因分型，并对线粒体细胞色素氧化酶I基因（mitochondrial Cytochrome Oxidase I gene）进行测序。我们采用了一系列种群遗传学统计方法与分析手段，包括近似贝叶斯计算（approximate Bayesian computation）。本研究明确揭示了近东种群的系统地理格局，并确凿证实法国入侵种群源自塞浦路斯——尽管现有历史数据曾强烈暗示土耳其或是最合理的起源地。值得注意的是，我们发现该入侵种群由极少数个体奠基建立，且发生了从短叶雪松（Cedrus brevifolia）到大西洋雪松（C. atlantica）的寄主转换。本文还对该非同寻常的入侵场景提出了相关演化假说以供讨论。