Meudt Heidi M, Pearson Sofie M, Ning Weixuan, Prebble Jessica M, Tate Jennifer A
Museum of New Zealand Te Papa Tongarewa, PO Box 467, Cable St, Wellington 6140, New Zealand.
Museum of New Zealand Te Papa Tongarewa, PO Box 467, Cable St, Wellington 6140, New Zealand; School of Agriculture and Environment, Massey University, Private Bag 11222, Palmerston North 4412, New Zealand.
Mol Phylogenet Evol. 2025 Mar;204:108250. doi: 10.1016/j.ympev.2024.108250. Epub 2024 Nov 22.
Island and mountain systems represent natural laboratories for studies of species radiations, but they often present several challenges for phylogenetic inference and species delimitation. The southern hemisphere forget-me-nots (Myosotis, Boraginaceae) comprise a geologically recent radiation centred in Aotearoa New Zealand, a mountainous archipelago, with about 50 species that are morphologically and ecologically divergent but lack genetic variation sufficient to resolve phylogenetic relationships and species boundaries using standard DNA Sanger sequencing markers, AFLPs, or microsatellites. Many of these Myosotis species are geographically restricted in alpine areas, uncommon or threatened, have polyploid and dysploid genomes, and are of high taxonomic and conservation priority. Here we present phylogenomic analyses using target-capture of Angiosperms353 baits, and genome skimming of whole plastomes and nrDNA, to improve resolution of the radiation, explore biogeographic and morphological patterns within it, and address specific taxonomic questions for each species. Our comprehensive sampling includes over 300 individuals representing nearly all species from New Zealand and Australia, which is ∼ 2-3 × more taxon sampling and ∼ 80-120 × more molecular data than previously published for Myosotis. Exploration of different data filtering, curation and analyses (coalescent vs. concatenation) improved the resolution of the Angiosperms353 tree, which despite short backbone branches with low support values, showed taxonomic and geographic patterns, including multiple switches between ebracteate and bracteate inflorescences and multiple expansions within New Zealand from Te Waipounamu South Island to Te Ika-a-Māui North Island, Rakiura Stewart Island, subantarctic islands, and Australia. Some of these patterns were also seen in the genome skimming datasets, and comparison of the three datasets was useful for improving our understanding of the taxonomy and resolution of this radiation. Although this phylogenomic study does not fully overcome all of the challenges regarding species delimitation of this rapid island and mountain species radiation, it nevertheless makes an important contribution to an integrative taxonomic revision of the southern hemisphere species of Myosotis.
岛屿和山脉系统是研究物种辐射的天然实验室，但它们在系统发育推断和物种界定方面往往带来诸多挑战。南半球勿忘草属（Myosotis，紫草科）植物在地质历史时期近期经历了一次辐射演化，其中心位于多山的新西兰群岛（Aotearoa New Zealand），约有50个物种，这些物种在形态和生态上存在差异，但利用标准的DNA桑格测序标记、AFLP或微卫星分析，缺乏足以解析系统发育关系和物种界限的遗传变异。这些勿忘草属物种中的许多在高山地区地理分布受限，较为罕见或受到威胁，具有多倍体和非整倍体基因组，在分类学和保护方面具有高度优先性。在此，我们利用被子植物353个诱饵的目标捕获、全质体基因组和nrDNA的基因组浅层测序进行系统基因组分析，以提高辐射演化的分辨率，探索其中的生物地理和形态模式，并解决每个物种的具体分类学问题。我们全面的采样包括来自新西兰和澳大利亚几乎所有物种的300多个个体，与之前发表的勿忘草属研究相比，分类单元采样增加了约2 - 3倍，分子数据增加了约80 - 120倍。对不同数据过滤、整理和分析（溯祖法与串联法）的探索提高了被子植物353树的分辨率，尽管主干分支较短且支持值较低，但该树显示出分类学和地理模式，包括无苞片和有苞片花序之间的多次转变，以及在新西兰境内从南岛的蒂瓦普纳穆（Te Waipounamu）到北岛的蒂伊卡-阿-毛伊（Te Ika-a-Māui）、拉基乌拉斯图尔特岛（Rakiura Stewart Island）、亚南极岛屿和澳大利亚的多次扩张。其中一些模式在基因组浅层测序数据集中也能看到，三个数据集的比较有助于增进我们对该辐射演化的分类学和分辨率的理解。尽管这项系统基因组研究并未完全克服关于这种快速的岛屿和山区物种辐射的物种界定的所有挑战，但它仍然为南半球勿忘草属物种的综合分类修订做出了重要贡献。
