The origin of species is a central topic in biology. Ecological speciation might be a driver in adaptive radiation, providing a framework for understanding mechanisms, level, and rate of diversification. The Arctic charr Salvelinus alpinus L. is a polymorphic species with huge morphological and life‐history diversity in Holarctic water systems. We studied adaptive radiation of Arctic charr in the 460‐m‐deep Lake Tinnsjøen to (a) document eco‐morphology and life‐history traits of morphs, (b) estimate reproductive isolation of morphs, and (c) illuminate Holarctic phylogeography and lineages colonizing Lake Tinnsjøen. We compared Lake Tinnsjøen with four Norwegian outgroup populations. Four field‐assigned morphs were identified in Lake Tinnsjøen: the planktivore morph in all habitats except deep profundal, the dwarf morph in shallow‐moderate profundal, the piscivore morph mainly in shallow‐moderate profundal, and a new undescribed abyssal morph in the deep profundal. Morphs displayed extensive life‐history variation in age and size. A moderate‐to‐high concordance was observed among morphs and four genetic clusters from microsatellites. mtDNA suggested two minor endemic clades in Lake Tinnsjøen originating from one widespread colonizing clade in the Holarctic. All morphs were genetically differentiated at microsatellites (F_ST: 0.12–0.20), associated with different mtDNA clade frequencies. Analyses of outgroup lakes implied colonization from a river below Lake Tinnsjøen. Our findings suggest postglacial adaptive radiation of one colonizing mtDNA lineage with niche specialization along a depth–temperature–productivity–pressure gradient. Concordance between reproductive isolation and habitats of morphs implies ecological speciation as a mechanism. Particularly novel is the extensive morph diversification with depth into the often unexplored deepwater profundal habitat, suggesting we may have systematically underestimated biodiversity in lakes. In a biological conservation framework, it is imperative to protect endemic below‐species‐level biodiversity, particularly so since within‐species variation comprises an extremely important component of the generally low total biodiversity observed in the northern freshwater systems.

中文翻译：

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“如果你长时间凝视深渊，深渊也会凝视你”：四种北极红点鲑正在适应 Tinnsjøen 湖的深度梯度。


物种起源是生物学的中心话题。生态物种形成可能是适应性辐射的驱动因素，为理解多样化的机制、水平和速率提供了框架。北极红点鲑Salvelinus alpinus L. 是一种多态性物种，在全北极水系统中具有巨大的形态和生活史多样性。我们研究了 460 米深的 Tinnsjøen 湖中北极红点鲑的适应性辐射，以 (a) 记录变体的生态形态和生活史特征，(b) 估计变体的生殖隔离，以及 (c) 阐明全北极系统发育和谱系殖民廷斯舍恩湖。我们将 Tinnsjøen 湖与四个挪威外群体进行了比较。在 Tinnsjøen 湖中发现了四种野外指定的变种：除深海以外所有生境中的浮游动物变种、浅-中深水区的矮化变种、主要在浅-中深水区的食鱼变种，以及深渊中新的未描述的深渊变种。 。变体在年龄和体型方面表现出广泛的生活史差异。在微卫星的形态和四个遗传簇之间观察到中度到高度的一致性。线粒体 DNA 表明，廷斯舍恩湖中的两个较小的地方性进化支起源于全北极的一个广泛的殖民进化支。所有形态均在微卫星上进行遗传分化（ F _ST ：0.12-0.20），与不同的 mtDNA 进化枝频率相关。对外群湖泊的分析表明，殖民活动来自廷斯舍恩湖下方的一条河流。我们的研究结果表明，一种沿深度-温度-生产力-压力梯度的生态位专门化的殖民线粒体DNA谱系的冰河后适应性辐射。 生殖隔离和变形栖息地之间的一致性意味着生态物种形成是一种机制。特别新颖的是，随着深入到经常未经探索的深水深海栖息地，广泛的形态多样化，这表明我们可能系统性地低估了湖泊的生物多样性。在生物保护框架中，必须保护特有的物种以下生物多样性，特别是因为物种内变异是北部淡水系统中观察到的总体生物多样性总体较低的极其重要的组成部分。