Baird Helena P, Moon Katherine L, Janion-Scheepers Charlene, Chown Steven L
School of Biological Sciences Monash University Clayton Victoria Australia.
Iziko Museums of South Africa Cape Town South Africa.
Evol Appl. 2020 Feb 12;13(5):960-973. doi: 10.1111/eva.12913. eCollection 2020 May.
Human-mediated transport of species outside their natural range is a rapidly growing threat to biodiversity, particularly for island ecosystems that have evolved in isolation. The genetic structure underpinning island populations will largely determine their response to increased transport and thus help to inform biosecurity management. However, this information is severely lacking for some groups, such as the soil fauna. We therefore analysed the phylogeographic structure of an indigenous and an invasive springtail species (Collembola: Poduromorpha), each distributed across multiple remote sub-Antarctic islands, where human activity is currently intensifying. For both species, we generated a genome-wide SNP data set and additionally analysed all available COI barcodes. Genetic differentiation in the indigenous springtail is substantial among (and, to a lesser degree, within) islands, reflecting low dispersal and historic population fragmentation, while COI patterns reveal ancestral signatures of postglacial recolonization. This pronounced geographic structure demonstrates the key role of allopatric divergence in shaping the region's diversity and highlights the vulnerability of indigenous populations to genetic homogenization via human transport. For the invasive species , nuclear genetic structure is much less apparent, particularly for islands linked by regular shipping, while diverged COI haplotypes indicate multiple independent introductions to each island. Thus, human transport has likely facilitated this species' persistence since its initial colonization, through the ongoing introduction and inter-island spread of genetic variation. These findings highlight the different evolutionary consequences of human transport for indigenous and invasive soil species. Crucially, both outcomes demonstrate the need for improved intraregional biosecurity among remote island systems, where the policy focus to date has been on external introductions.
人类将物种运输到其自然分布范围之外，这对生物多样性构成了迅速增长的威胁，对于那些在隔离状态下进化的岛屿生态系统而言尤其如此。支撑岛屿种群的遗传结构在很大程度上决定了它们对运输增加的反应，从而有助于为生物安全管理提供信息。然而，对于一些群体，如土壤动物群，这方面的信息严重匮乏。因此，我们分析了一种本土弹尾虫物种和一种入侵弹尾虫物种（弹尾目：原等节跳虫）的系统发育地理结构，这两种弹尾虫都分布在多个偏远的亚南极岛屿上，而目前人类活动正在这些岛屿上加剧。对于这两个物种，我们生成了全基因组SNP数据集，并额外分析了所有可用的细胞色素氧化酶亚基I（COI）条形码。本土弹尾虫在岛屿之间（以及在较小程度上在岛屿内部）存在显著的遗传分化，这反映了其低扩散率和历史上的种群碎片化，而COI模式揭示了冰期后重新定殖的祖先特征。这种明显的地理结构表明异域分化在塑造该地区多样性方面的关键作用，并突出了本土种群通过人类运输而导致遗传同质化的脆弱性。对于入侵物种，核遗传结构不太明显，特别是对于有定期航运连接的岛屿，而不同的COI单倍型表明每个岛屿有多次独立引入。因此，自最初定殖以来，人类运输可能通过持续引入和在岛屿间传播遗传变异，促进了该物种的存续。这些发现突出了人类运输对本土和入侵土壤物种的不同进化后果。至关重要的是，这两种结果都表明，在偏远岛屿系统中需要改善区域内生物安全，而迄今为止政策重点一直放在外部引入上。
