ABSTRACT In the North-east (NE) Atlantic, most intertidal fucoids and warm-temperate kelps show unique low-latitude gene pools matching long-term climatic refugia. For cold-temperate kelps data are scarcer despite their unique cultural, ecological and economic significance. Here we test whether the amphi-Atlantic range of Laminaria digitata is derived from past glacial survival (and vicariance) in both NE and North-west (NW) Atlantic refugia (as suggested by niche modelling), or post-glacial (re)colonization (as suggested by low mtDNA divergence). We screened 14 populations from across the species range for 12 microsatellite loci to identify and map major gene pools and refugia. We assessed if NW Atlantic survival was supported by unique endemic variation, and if genetic diversity and structure were, as predicted from larger hindcasted glacial ranges, higher in the NE Atlantic. Microsatellite data subdivided L. digitata into three main genetic groups matching Brittany, northern Europe and the NW Atlantic, with finer-scale sub-structuring within European clusters. The relatively diverse NE Atlantic lineages probably survived the Last Glacial Maximum along unglaciated periglacial shorelines of the Armorican and Celtic Seas (Brittany cluster) and Ireland (northern European cluster), and remain well differentiated despite their relative proximity. The unique Brittany gene pool, at the contemporary European rear edge, is projected to disappear in the near future under high greenhouse gas emission scenarios. Low allelic diversity and low endemism in the NW Atlantic are consistent with recent post-glacial colonization from Europe, challenging the long-standing hypothesis of in situ glacial survival. Confusion with Hedophyllum nigripes may have led to underestimation of regional diversity of L. digitata, but also to overestimation of its presence along putative trans-Atlantic migration routes. Partial incongruence between modelling and genetic-based biogeographic inferences highlights the benefits of comparing both approaches to understand how shifting climatic conditions affect marine species distributions and explain large-scale patterns of spatial genetic structure.

中文翻译：

---

两栖大西洋海带（Laminariales，Phaeophyceae）的遗传结构揭示了一个独特的范围边缘基因库，并表明西北大西洋的冰川后殖民化

摘要 在东北 (NE) 大西洋，大多数潮间带岩藻和暖温带海带显示出与长期气候保护区相匹配的独特低纬度基因库。尽管冷温带海带具有独特的文化、生态和经济意义，但它们的数据很少。在这里，我们测试了 Laminaria digitata 的两栖大西洋范围是否来自东北​​和西北（NW）大西洋保护区过去的冰川生存（和替代）（如生态位建模所建议的），或冰川后（重新）殖民化（如低 mtDNA 分歧所暗示的那样）。我们从物种范围内筛选了 14 个种群的 12 个微卫星位点，以识别和绘制主要基因库和避难所。我们评估了西北大西洋的生存是否受到独特的地方性变异的支持，以及遗传多样性和结构是否受到支持，正如从更大的后倾冰川范围所预测的那样，在东北大西洋更高。微卫星数据将 L. digitata 细分为与布列塔尼、北欧和西北大西洋相匹配的三个主要遗传组，在欧洲集群内具有更精细的亚结构。相对多样化的东北大西洋谱系可能在末次冰期盛期中幸存下来，沿着阿莫里克海和凯尔特海（布列塔尼海群）和爱尔兰（欧洲北部海群）的未冰川边缘海岸线，尽管它们相对接近，但仍然保持良好的分化。在高温室气体排放情景下，位于当代欧洲后方的独特布列塔尼基因库预计将在不久的将来消失。西北大西洋的低等位基因多样性和低特有现象与欧洲最近的冰川后殖民化一致，挑战原位冰川存活的长期假设。与 Hedophyllum nigripes 的混淆可能导致低估了 L. digitata 的区域多样性，但也高估了它在假定的跨大西洋迁移路线上的存在。建模和基于遗传的生物地理学推断之间的部分不一致突出了比较两种方法的好处，以了解不断变化的气候条件如何影响海洋物种分布并解释空间遗传结构的大尺度模式。