Damerau M, Matschiner M, Salzburger W, Hanel R
Thünen-Institute of Fisheries Ecology, Palmaille 9, 22767, Hamburg, Germany.
Department of Mathematics and Statistics, Allan Wilson Centre of Molecular Ecology and Evolution, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.
Mol Ecol. 2014 Feb;23(2):284-99. doi: 10.1111/mec.12612. Epub 2013 Dec 28.
Dispersal via pelagic larval stages plays a key role in population connectivity of many marine species. The degree of connectivity is often correlated with the time that larvae spend in the water column. The Antarctic notothenioid fishes develop through an unusually long pelagic larval phase often exceeding 1 year. Notothenioids thus represent a prime model system for studying the influence of prolonged larval phases on population structure in otherwise demersal species. Here, we compare the population genetic structure and demographic history of two sub-Antarctic crocodile icefish species (Chaenocephalus aceratus and Champsocephalus gunnari) from the Scotia Arc and Bouvet Island in the Atlantic sector of the Southern Ocean to delineate the relative importance of species-specific, oceanographic and paleoclimatic factors to gene flow. Based on 7 (C. aceratus) and 8 (C. gunnari) microsatellites, as well as two mitochondrial DNA markers (cytochrome b, D-loop), we detect pronounced population genetic structure in both species (amova FSTs range from 0.04 to 0.53). High genetic similarities were found concordantly in the populations sampled at the Southern Scotia Arc between Elephant Island and South Orkney Islands, whereas the populations from Bouvet Island, which is located far to the east of the Scotia Arc, are substantially differentiated from those of the Scotia Arc region. Nonetheless, haplotype genealogies and Bayesian cluster analyses suggest occasional gene flow over thousands of kilometres. Higher divergences between populations of C. gunnari as compared to C. aceratus are probably caused by lower dispersal capabilities and demographic effects. Bayesian skyline plots reveal population size reductions during past glacial events in both species with an estimated onset of population expansions about 25 000 years ago.
通过浮游幼体阶段进行扩散在许多海洋物种的种群连通性中起着关键作用。连通程度通常与幼体在水柱中停留的时间相关。南极南极鱼科鱼类经历异常漫长的浮游幼体阶段，通常超过1年。因此，南极鱼科鱼类是研究延长的幼体阶段对原本底栖物种种群结构影响的理想模型系统。在这里，我们比较了南大洋大西洋海域斯科舍海岭和布韦岛的两种亚南极鳄冰鱼（长头南极鱼和冈氏头带冰鱼）的种群遗传结构和种群历史，以确定物种特异性、海洋学和古气候因素对基因流动的相对重要性。基于7个（长头南极鱼）和8个（冈氏头带冰鱼）微卫星以及两个线粒体DNA标记（细胞色素b、D环），我们在这两个物种中均检测到明显的种群遗传结构（分子方差分析FST范围为0.04至0.53）。在南斯科舍海岭的象岛和南奥克尼群岛之间采集的种群中一致发现了高度的遗传相似性，而位于斯科舍海岭以东很远的布韦岛的种群与斯科舍海岭地区的种群有很大差异。尽管如此，单倍型谱系和贝叶斯聚类分析表明，偶尔会有数千公里的基因流动。与长头南极鱼相比，冈氏头带冰鱼种群之间的差异更大，这可能是由于扩散能力较低和种群统计学效应所致。贝叶斯天际线图显示，在过去的冰川事件中，这两个物种的种群数量都有所减少，估计种群扩张开始于约25000年前。
