Plastid marker variation reveals immigration history in Scandinavian <i>Syntrichia norvegica</i> and <i>S. ruralis</i> (Pottiaceae, Bryophyta)

Based on previous analyses of <i>Syntrichia norvegica</i> and <i>S. ruralis</i>, the idea of panmictic populations in Scandinavia can be rejected, despite the high dispersal capacities of wind-dispersed spores. We tested, using comprehensive European datasets, whether intraspecific phylogeographical structure reflects glacial and post-glacial history. We expected different entities to indicate immigration from known Late Glacial Maximum refugial areas, and habitat differentiation. Using plastid markers (<i>atp</i>B–<i>rbc</i>L and <i>rpl</i>16), we investigated 45 and 190 Scandinavian and 17 and 15 non-Scandinavian specimens of <i>Syntrichia norvegica</i> and <i>S. ruralis</i>, respectively. We revealed four intraspecific entities in <i>Syntrichia norvegica</i>. Two were from the Scandinavian mountains and the Alps, and one from the Scandinavian mountains only. The fourth was widespread across the Scandinavian mountains, the northern lowlands, and the Baltic Sea islands Öland and Gotland. For <i>S. ruralis</i>, we recovered five entities, of which three were from both Scandinavia and the Alps. One of these occurred in strongly calcareous habitats in southern Scandinavia and the Alps and dominated on Öland and Gotland. One entity was widely distributed only in Scandinavia. One was restricted to the border between boreo-nemoral and southern-boreal Scandinavia. The plastid haplotype distribution patterns suggest glacial survival of <i>Syntrichia norvegica</i> and <i>S. ruralis</i> in refugia south, east and possibly within ice-covered areas of Scandinavia. We hypothesise that one <i>S. ruralis</i> entity evolved adaptations to strongly calcareous habitats. The dominance or prevalence of specific haplotypes of both species on Öland and Gotland contributes to the unique biodiversity of these islands.基于此前对纽氏缩叶藓（*Syntrichia norvegica*）与赤背缩叶藓（*Syntrichia ruralis*）的研究，尽管风播孢子具备极强的扩散能力，但斯堪的纳维亚半岛存在随机交配种群的假说可被推翻。本研究依托覆盖全欧的综合性数据集，探究种内系统地理结构是否能够反映冰期及冰期后的种群演化历史。我们预设，不同的种内类群应对应来自已知末次冰盛期避难所的迁入事件，以及生境分化现象。本研究借助质体标记（plastid markers）：*atpB–rbcL*与*rpl16*基因间隔区，分别对斯堪的纳维亚半岛的45份纽氏缩叶藓标本、190份赤背缩叶藓标本，以及非斯堪的纳维亚地区的17份纽氏缩叶藓标本、15份赤背缩叶藓标本开展了分析。本研究在纽氏缩叶藓中共检出4个种内类群：其中2个类群分布于斯堪的纳维亚山地与阿尔卑斯山区，1个类群仅见于斯堪的纳维亚山地；第4个类群广泛分布于斯堪的纳维亚山地、北部低地，以及波罗的海岛屿厄兰岛（Öland）与哥特兰岛（Gotland）。针对赤背缩叶藓，我们共鉴定出5个种内类群，其中3个类群同时分布于斯堪的纳维亚半岛与阿尔卑斯山区。其中1个类群见于斯堪的纳维亚南部与阿尔卑斯山区的强钙质生境中，并在厄兰岛与哥特兰岛占据优势；1个类群仅广泛分布于斯堪的纳维亚半岛；另有1个类群局限于寒温带-温带过渡带与南寒温带斯堪的纳维亚地区的交界地带。质体单倍型的分布模式表明，纽氏缩叶藓与赤背缩叶藓在南、东方向的避难所，以及斯堪的纳维亚半岛境内的冰盖覆盖区域中均存在冰期存活种群。我们提出假说：其中1个赤背缩叶藓类群演化出了适应强钙质生境的特性。两个物种的特定单倍型在厄兰岛与哥特兰岛的优势分布或高频出现，是促成这两座岛屿独特生物多样性的重要因素。