Thompson Claire E, Taylor Eric B, McPhail J Donald
Department of Zoology, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada.
Evolution. 1997 Dec;51(6):1955-1965. doi: 10.1111/j.1558-5646.1997.tb05117.x.
Three drainage systems in British Columbia, Canada, contain divergent parapatric lake-stream pairs of threespine sticklebacks (Gasterosteus aculeatus): Drizzle and Mayer Lakes on Graham Island, Queen Charlotte Islands, and Misty Lake on northeastern Vancouver Island. Ecological and morphological differences between members of all three lake-stream pairs are strikingly similar; lake fish are melanistic and slim bodied with smaller mouths and more gill rakers than the mottled-brown and robust-bodied stream sticklebacks. We estimated the level of genetic divergence between lake and stream fish in Misty Lake and tested hypotheses of single versus multiple origins of the pairs by assaying mitochondrial DNA (mtDNA) restriction site variation in samples from the three lake systems. MtDNA analysis revealed the existence of two highly divergent lineages differing by 2.7% in sequence. One lineage predominated in Misty stream fish (73%), whereas the other lineage predominated in Misty Lake samples (96%). Comparable forms (lake or stream) in the different lakes did not cluster together in terms of mtDNA nucleotide divergence, suggesting that the pairs have had independent origins. We concluded that: (1) divergent mtDNA lineages in North Pacific sticklebacks stem from historical isolation in the two major glacial refugia proposed for the North Pacific (Beringia and Cascadia); (2) the stream and lake pair in Misty Lake are distinct gene pools; (3) the divergence between parapatric lake and stream Gasterosteus represents parallel evolution having occurred at least twice in the North Pacific; and (4) different scales of evolutionary divergence exist in North Pacific Gasterosteus, that is, a relatively ancient divergence of mtDNA clades as well as recent (i.e., postglacial) divergence of ecotypes within major clades.
加拿大不列颠哥伦比亚省的三个排水系统中，包含三刺鱼（Gasterosteus aculeatus）的不同邻域性湖 - 溪对：夏洛特皇后群岛格雷厄姆岛上的毛毛雨湖和梅耶湖，以及温哥华岛东北部的迷雾湖。所有这三对湖 - 溪的成员之间在生态和形态上的差异惊人地相似；湖鱼体色呈黑色且体型细长，嘴巴较小，鳃耙比斑驳褐色且体型粗壮的溪流三刺鱼更多。我们估计了迷雾湖中的湖鱼和溪流鱼之间的遗传分化水平，并通过分析来自这三个湖泊系统样本中的线粒体DNA（mtDNA）限制性位点变异，来检验这些配对是单次还是多次起源的假说。mtDNA分析揭示存在两个高度分化的谱系，序列差异为2.7%。一个谱系在迷雾溪鱼中占主导（73%），而另一个谱系在迷雾湖样本中占主导（96%）。不同湖泊中类似形态的（湖或溪）鱼在mtDNA核苷酸分化方面并未聚集在一起，这表明这些配对有独立的起源。我们得出以下结论：（1）北太平洋三刺鱼中不同的mtDNA谱系源于为北太平洋提出的两个主要冰川避难所（白令陆桥和卡斯卡迪亚）中的历史隔离；（2）迷雾湖中的溪流和湖泊配对是不同的基因库；（3）邻域性的湖栖和溪流三刺鱼之间的分化代表了在北太平洋至少发生过两次的平行进化；（4）北太平洋三刺鱼存在不同尺度的进化分化，即mtDNA分支相对古老的分化以及主要分支内生态型的近期（即冰期后）分化。
