Barluenga Marta, Sanetra Matthias, Meyer Axel
Lehrstuhl für Zoologie und Evolutionsbiologie, Department of Biology, University of Konstanz, Universitätsstrasse 10, 78457 Konstanz, Germany.
Mol Ecol. 2006 Oct;15(12):3583-600. doi: 10.1111/j.1365-294X.2006.03045.x.
The burbot, Lota lota, is the only freshwater species of the codfish family and has a Holarctic distribution. Pleistocene glaciations caused significant geographical differentiation in the past, but its life history characterized by winter spawning migrations over large distances is likely to homogenize populations by contemporary gene flow. We investigated the population genetic structure of 541 burbots from Lake Constance and adjacent Rhine and Danube tributaries in Europe using the entire mitochondrial DNA (mtDNA) control region and 11 microsatellites. Microsatellites revealed considerable population divergence (F(ST) = 0.26) and evidenced recent bottlenecks in two Central European rivers. In accordance to previous evidence two main phylogeographic lineages (Atlantic and Danubian) were found co-occurring at similar frequencies in Lake Constance, where they currently undergo random mating as indicated by microsatellites. The Danubian lineage contributed only a small proportion to the lake's mtDNA diversity, and probably expanded within the lake shortly after its formation approximately 10,000-15,000 BP. The larger Atlantic haplotype diversity suggested a population expansion older than the lake itself. Levels of admixture at microsatellite loci were less obvious due to their high variability, and coalescence methods were used to estimate past admixture proportions. Our results reinforce a model of a two-step colonization of Europe by burbot from an ancestral Danubian refuge, and confirm the persistence of a secondary Atlantic refuge, as proposed to exist for other freshwater fish. We conclude that the present-day burbot population in Lake Constance bears the genetic signature of both contemporary gene flow and historical separation events.
江鳕（Lota lota）是鳕科唯一的淡水物种，分布于全北区。更新世冰川作用在过去造成了显著的地理分化，但其以冬季远距离产卵洄游为特征的生活史可能通过当代基因流使种群同质化。我们使用整个线粒体DNA（mtDNA）控制区和11个微卫星，对来自欧洲康斯坦茨湖及邻近莱茵河和多瑙河支流的541条江鳕的种群遗传结构进行了调查。微卫星显示出相当大的种群分化（F(ST) = 0.26），并证明了两条中欧河流近期存在瓶颈效应。与先前的证据一致，在康斯坦茨湖中发现了两个主要的系统发育谱系（大西洋谱系和多瑙河谱系）以相似的频率共存，微卫星表明它们目前正在进行随机交配。多瑙河谱系对该湖的mtDNA多样性贡献较小，可能在该湖大约在10,000 - 15,000 BP形成后不久就在湖中扩张。较大的大西洋单倍型多样性表明种群扩张早于该湖本身。由于微卫星位点的高变异性，其混合水平不太明显，因此使用了溯祖方法来估计过去的混合比例。我们的结果强化了江鳕从多瑙河祖先避难所分两步殖民欧洲的模型，并证实了如对其他淡水鱼所提出的那样，存在一个二级大西洋避难所。我们得出结论，康斯坦茨湖现今的江鳕种群具有当代基因流和历史隔离事件的遗传特征。
