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.

诸多物种放弃迁徙的倾向，是进化生物学中尚未被充分理解的重要方面，其可能通过异域物种形成（allopatric）与同域物种形成（sympatric）两种机制，在推动物种辐射中发挥关键作用。溯河产卵洄游（anadromy）本身为淡水生境的拓殖提供了可能，而从溯河洄游生活史转变为完全淡水生活史的现象，在多个鱼类类群中均有发生。七鳃鳗类中（七鳃鳗科Petromyzontidae与Mordaciidae科）反复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近缘类群，究竟是独立物种，还是多态物种下的趋异生态型。本研究采集了分布于18个采样点（主要位于不列颠群岛）的543尾欧洲河七鳃鳗（Lampetra fluviatilis，多数来自溯河洄游种群）以及欧洲溪七鳃鳗（Lampetra planeri，淡水定居型）样本，对其13个多态性微卫星DNA位点（microsatellite DNA loci）进行分型检测；同时从其中6个采样点的108尾样本中，扩增测序得到829 bp的线粒体DNA（mitochondrial DNA, mtDNA）序列。研究发现，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：所有种群的线粒体DNA多样性较低且种群结构分化不明显（与近期奠基者扩张事件的特征相符），而核基因标记则呈现出显著的精细尺度种群分化。多数情况下，淡水定居型的L. planeri种群之间，以及L. fluviatilis与L. planeri之间的微卫星DNA位点均存在强烈的遗传分化，但溯河洄游型L. fluviatilis种群之间几乎无明显种群结构。本研究认为，冰期后拓殖事件催生了多个具有强生境专一性且扩散能力有限的淡水定居种群，这些种群随后发生了高度的遗传分化，而人为活动造成的障碍可能进一步加剧了这一分化模式。