Bracken Fiona S A, Hoelzel A Rus, Hume John B, Lucas Martyn C
School of Biological and Biomedical Sciences, Durham University, Durham, DH1 3LE, UK.
Mol Ecol. 2015 Mar;24(6):1188-204. doi: 10.1111/mec.13112. Epub 2015 Mar 6.
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.
许多物种放弃洄游的倾向在进化生物学中仍是一个鲜为人知的方面，这可能通过异域和同域机制在促进物种辐射方面发挥重要作用。溯河洄游本质上为淡水环境的定殖提供了机会，并且在许多鱼类家族中都发生了从溯河洄游到完全淡水生活史的转变。淡水定居形态在七鳃鳗（在盲鳗科和八目鳗科内）中反复出现，关于溯河洄游的七鳃鳗及其衍生的淡水定居类似物是构成不同物种还是多态物种的不同生态型，一直存在很多争论。对来自18个地点（主要在不列颠群岛）的543个欧洲河七鳃鳗Lampetra fluviatilis样本（大多来自溯河洄游种群）和淡水欧洲溪七鳃鳗Lampetra planeri进行了13个多态微卫星DNA位点的研究，并对其中6个地点的108个样本进行了829 bp线粒体DNA（mtDNA）的测序。我们发现mtDNA和微卫星DNA标记的种群结构模式形成对比，即所有种群的mtDNA多样性低且几乎没有结构（与近期的奠基者扩张事件一致），而核标记则呈现出明显的精细结构。在大多数情况下，淡水定居的溪七鳃鳗种群之间以及河七鳃鳗和溪七鳃鳗之间微卫星DNA位点的分化很强，但溯河洄游的河七鳃鳗种群之间几乎没有结构。我们得出结论，冰期后定殖形成了多个具有强烈栖息地忠诚度和有限扩散倾向的淡水定居种群，这些种群变得高度分化，这种模式可能因人为障碍而加剧。
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