Data from: Contrasting population genetic structure among freshwater-resident and anadromous lampreys: the role of demographic history, differential dispersal, and anthropogenic barriers to movement.

The tendency of many species to abandon migration remains a poorly understood aspect of evolutionary biology that may play an important role in promoting species radiation by both allopatric and sympatric mechanisms. Anadromy inherently offers an opportunity for the colonization of freshwater environments, and the shift from an anadromous to a wholly freshwater life history has occurred in many families of fishes. Freshwater-resident forms have arisen repeatedly among lampreys (within the Petromyzontidae and Mordaciidae), and there has been much debate as to whether anadromous lampreys, and their derived freshwater-resident analogues, constitute distinct species or are divergent ecotypes of polymorphic species. Samples of 543 European river lamprey Lampetra fluviatilis (mostly from anadromous populations) and freshwater European brook lamprey Lampetra planeri from across 18 sites, primarily in the British Isles, were investigated for 13 polymorphic microsatellite DNA loci, and 108 samples from six of these sites were sequenced for 829 bp of mitochondrial DNA (mtDNA). We found contrasting patterns of population structure for mtDNA and microsatellite DNA markers, such that low diversity and little structure were seen for all populations for mtDNA (consistent with a recent founder expansion event), while fine-scale structuring was evident for nuclear markers. Strong differentiation for microsatellite DNA loci was seen among freshwater-resident L. planeri populations and between L. fluviatilis and L. planeri in most cases, but little structure was evident among anadromous L. fluviatilis populations. We conclude that postglacial colonization founded multiple freshwater-resident populations with strong habitat fidelity and limited dispersal tendencies that became highly differentiated, a pattern that was likely intensified by anthropogenic barriers.

诸多物种放弃洄游的习性，仍是进化生物学领域尚未得到充分阐释的核心议题之一，其或通过异域物种形成（allopatric）与同域物种形成（sympatric）两种机制推动物种辐射演化。溯河洄游（anadromy）天生为淡水生境的拓殖提供了天然契机，诸多鱼类类群均曾独立演化出从溯河洄游生活史转向完全淡水定居生活史的策略。七鳃鳗类中（七鳃鳗科Petromyzontidae与袋七鳃鳗科Mordaciidae）已多次独立演化出淡水定居型类群，学界长期存在争议：溯河洄游七鳃鳗及其衍生的淡水定居型近缘类群，究竟是独立的有效物种，还是多态物种内的趋异生态型？本研究采集了主要分布于不列颠群岛的18个采样点的543份欧洲河七鳃鳗（Lampetra fluviatilis，多数样本来自溯河洄游种群）与欧洲溪七鳃鳗（Lampetra planeri，淡水定居型）样本，对其13个多态性微卫星DNA（microsatellite DNA）位点进行分型检测；同时对其中6个采样点的108份样本的829 bp线粒体DNA（mtDNA）片段进行了测序分析。研究结果显示，线粒体DNA与微卫星DNA标记呈现出截然不同的种群结构模式：线粒体DNA在所有种群中均表现出较低的遗传多样性与极弱的种群分化结构，这与近期发生的奠基者扩张事件的特征相符；而核标记则呈现出显著的精细尺度种群分化结构。多数情况下，淡水定居型溪七鳃鳗种群之间，以及河七鳃鳗与溪七鳃鳗之间均存在显著的微卫星DNA位点分化，但溯河洄游型河七鳃鳗种群之间几乎未表现出明显的种群结构。本研究得出结论：冰期后淡水生境拓殖事件催生了多个具有高度生境忠实性与有限扩散能力的淡水定居种群，这些种群逐渐形成了强烈的遗传分化，而人为活动造成的生境障碍进一步加剧了这一分化模式。