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 colonisation 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 L. 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 829bp 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 post-glacial colonisation 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倾向，仍是进化生物学中尚未被充分阐明的核心议题之一，但其可能通过异域分化与同域分化两种机制，在推动物种辐射演化过程中发挥关键作用。溯河洄游（anadromy）本身为淡水生境的开拓提供了天然契机，众多鱼类类群均曾独立发生从溯河洄游生活史向完全淡水生活史的适应性转变。七鳃鳗类（七鳃鳗科Petromyzontidae与 Mordaciidae）中，淡水定居型类群已多次独立起源，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同类，究竟是独立的有效物种，还是多态物种内的趋异生态型？本研究对采自18个采样点（主要分布于不列颠群岛）的543份欧洲河七鳃鳗*Lampetra fluviatilis*样本（多数来自溯河洄游种群）以及欧洲溪七鳃鳗*L. planeri*淡水种群样本，开展了13个多态微卫星DNA位点的基因分型检测；同时对其中6个采样点的108份样本，进行了829bp长度的线粒体DNA（mtDNA）序列扩增与测序。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均表现出低遗传多样性与弱种群分化结构，这与近期奠基者扩张事件的遗传特征高度相符；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*L. planeri*种群之间，以及*L. fluviatilis*与*L. planeri*之间，均存在较强的微卫星DNA位点遗传分化，但溯河洄游型*L. fluviatilis*种群之间几乎无明显的种群结构分化。本研究最终认为，第四纪冰期后的殖民事件孕育了多个具有高栖息地忠实性与有限扩散能力的淡水定居种群，这些种群随后发生了显著的遗传分化，而人为活动造成的阻隔进一步加剧了这一分化模式。