ABSTRACT

The terrestrial slug Deroceras invadens has spread across much of the world over the last century. What is there to learn about its origin, colonizations and diversity by comparing barcoding sequences of the mitochondrial gene COI (cytochrome c oxidase subunit I)? Samples from 317 localities covering most of the species’ range yielded 87 haplotypes. Higher diversity, the predominance of private haplotypes and geographic structuring all indicate a native range centred on southern Italy, including eastern Sicily. In contrast, central Italy is dominated by one haplotype, although accompanied by both close and more distant relatives; the lack of geographic structuring suggests recent expansion from a restricted distribution within that region. Beyond the Alps, two haplotypes predominate, accompanied by very similar variants; such star-shaped genealogies characterize recent population growth. Also, some rarer haplotypes have been independently introduced. Generally, haplotypes are well mixed here, often co-occurring at a locality. In North America and Australasia, some frequent haplotypes were likely directly introduced from Italy, because they were not found elsewhere in Europe. The rarity or absence in these continents of one or other of the two dominant European haplotypes suggests that import inspections have restricted repeated introductions. A skyline plot detects the recent demographic expansion but also indicates an earlier population decline in the native area. This may explain why the one-dimensional summary statistics F_S and R₂ did not signal population growth. A review of 41 other studies that used DNA to analyse invasions of terrestrial molluscs documents considerable diversity in methodology. Studies using genetic data to date recent invasions probably should adjust standard substitution rates upwards.

中文翻译：

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遗传证据阐明了De虫Deroceras invadens的起源和全球传播

摘要

上个世纪，陆地Deroceras入侵已扩散到世界各地。通过比较线粒体基因COI（细胞色素c的条形码）的序列来了解其起源，定植和多样性氧化酶亚基I）？来自317个地区的样本涵盖了该物种的大部分范围，得出了87个单倍型。更高的多样性，私人单倍型的优势和地理结构都表明一个以意大利南部（包括西西里岛东部）为中心的本土范围。相比之下，意大利中部以一种单体型为主导，尽管有近亲和远亲。由于缺乏地理结构，这表明该地区最近的分布有限。除阿尔卑斯山外，还有两个单体型，并伴有非常相似的变异。这种星形家谱是近期人口增长的特征。另外，一些罕见的单体型已被独立引入。通常，单倍型在这里混合得很好，通常在一个地方同时出现。在北美和大洋洲，一些常见的单倍型很可能是直接从意大利引进的，因为它们在欧洲其他地方没有发现。在这两个大陆上，欧洲两种主要单倍型中的一种或另一种很少见或缺乏，这表明进口检查已限制了重复进口。天际线图可以检测到最近的人口增长情况，但也表明本地人口较早减少。这可以解释为什么一维汇总统计F _S和R ₂并不表示人口增长。对其他41个使用DNA分析陆地软体动物入侵的研究的回顾表明，方法学上存在很大差异。迄今为止，利用遗传数据进行的最新研究可能应该向上调整标准替代率。