Stefanni Sergio, Knutsen Halvor
IMAR/DOP, University of the Azores, Cais Sta Cruz, 9901-862 Horta, Azores, Portugal.
Mol Phylogenet Evol. 2007 Jan;42(1):38-46. doi: 10.1016/j.ympev.2006.05.035. Epub 2006 Jun 3.
Comparative phylogeography for the commercially valuable deep-sea fish Aphanopus carbo from a large area of the NE Atlantic revealed remarkable patterns of concordance using two mtDNA markers. Two strongly supported phylogroups were identified from complete sequences of the control region (731-733 bp) and partial sequences of cytochrome b (414 bp) In one of these groups, all sequences from the Mid-Atlantic Ridge (Faraday seamount), mainland Portugal and Madeira were clustered together. The other group constituted all the sequences from the southern coast of Pico island (Azores, central group). The remaining sampling localities had sequences represented in both phylogroups. Although the two clades were strongly differentiated (Phi(ST) = 0.8281 for the CR and Phi(ST) = 0.9083 for the cytb) no evidence for any geographical pattern in this structure, was found. Historical demography of the mitochondrial control region was analysed to clarify the phylogenetic signals embedded in each phylogroup. Mismatch distributions for both clades suggested that both phylogroups were in agreement with sudden expansion models, and both with similar time estimates of expansion (tau = 4.30 and tau = 3.45 for phylogroup one and two, respectively). A molecular clock based on cytb sequences was enforced and dating of divergence for the two phylogroup was 412.5 KY, a time that coincides with geological events that might have caused a split in the original population of black scabbardfish. Once climatic conditions and sea level were restored, the two separate populations came into contact again, leaving traces of the historical events in the non-recombinant mtDNA genes. An alternative hypothesis suggested is that two species of scabbardfish are present. The outcome from the comparison of the same mtDNA regions of the closely related Aphanopus intermedius from Angola clustered with the ones from phylogroup two (from the southern coast of Pico island, Azores). Therefore, these two species may have overlapping distribution ranges and are found sympatrically in the Azores.
对东北大西洋大片区域内具有商业价值的深海鱼类卡氏无须鳕进行的比较系统地理学研究显示，使用两个线粒体DNA标记呈现出显著的一致性模式。从控制区的完整序列（731 - 733 bp）和细胞色素b的部分序列（414 bp）中鉴定出两个得到有力支持的系统类群。在其中一个类群中，来自大西洋中脊（法拉第海山）、葡萄牙大陆和马德拉岛的所有序列聚集在一起。另一个类群由皮科岛（亚速尔群岛，中部组）南岸的所有序列组成。其余采样地点的序列在两个系统类群中均有体现。尽管这两个进化枝有强烈分化（控制区的Phi(ST) = 0.8281，细胞色素b的Phi(ST) = 0.9083），但未发现这种结构存在任何地理模式的证据。对线粒体控制区的历史种群动态进行了分析，以阐明每个系统类群中所蕴含的系统发育信号。两个进化枝的错配分布表明，两个系统类群均符合突然扩张模型，且扩张时间估计相似（系统类群一和二的tau分别为4.30和3.45）。基于细胞色素b序列的分子钟被应用，两个系统类群的分歧时间为412.5千年前，这一时期与可能导致黑剑鱼原始种群分裂的地质事件相吻合。一旦气候条件和海平面恢复正常，两个分离的种群再次接触，在非重组的线粒体DNA基因中留下了历史事件的痕迹。另一种提出的假设是存在两种剑鱼。对来自安哥拉的近缘种中间无须鳕相同线粒体DNA区域的比较结果显示，其与来自系统类群二（来自亚速尔群岛皮科岛南岸）的样本聚集在一起。因此，这两个物种可能具有重叠的分布范围，并且在亚速尔群岛同域分布。
