Audzijonytė Asta, Damgaard Jakob, Varvio Sirkka-Liisa, Vainio Jouni K, Väinölä Risto
Finnish Museum of Natural History, PO Box 17 (P. Rautatiekatu 13), University of Helsinki, FI-00014, Helsinki, Finland.
Department of Biological and Environmental Sciences, PO Box 65 (Viikinkaari 1), University of Helsinki, FI-00014, Helsinki, Finland.
Cladistics. 2005 Dec;21(6):575-596. doi: 10.1111/j.1096-0031.2005.00081.x.
We studied the phylogenetic history of opossum shrimps of the genus Mysis Latreille, 1802 (Crustacea: Mysida) using parsimony analyses of morphological characters, DNA sequence data from mitochondrial (16S, COI and CytB) and nuclear genes (ITS2, 18S), and eight allozyme loci. With these data we aimed to resolve a long-debated question of the origin of the non-marine (continental) taxa in the genus, i.e., "glacial relicts" in circumpolar postglacial lakes and "arctic immigrants" in the Caspian Sea. A simultaneous analysis of the data sets gave a single tree supporting monophyly of all continental species, as well as monophyly of the taxa from circumpolar lakes and from the Caspian Sea. A clade of three circumarctic marine species was sister group to the continental taxa, whereas Atlantic species had more distant relationships to the others. Small molecular differentiation among the morphologically diverse endemic species from the Caspian Sea suggested their recent speciation, while the phenotypically more uniform "glacial relict" species from circumpolar lakes (Mysis relicta group) showed deep molecular divergences. For the length-variable ITS2 region both direct optimization and a priori alignment procedures gave similar topologies, although the former approach provided a better overall resolution. In terms of partitioned Bremer support (PBS), mitochondrial protein coding genes provided the largest contribution (83%) to the total tree resolution. This estimate however, appears to be partly spurious, due to the concerted inheritance of mitochondrial characters and probable cases of introgression or ancestral polymorphism.
我们使用形态特征的简约分析、线粒体（16S、COI和CytB）和核基因（ITS2、18S）的DNA序列数据以及八个等位酶位点，研究了1802年拉特雷耶（Latreille）命名的麦秆虫属（Mysis）负蝽虾类的系统发育历史。利用这些数据，我们旨在解决该属非海洋（大陆）类群起源这一长期争论的问题，即环极冰后期湖泊中的“冰川遗迹种”和里海中的“北极迁入种”。对这些数据集进行同步分析得到了一棵单一的树，支持所有大陆物种的单系性，以及环极湖泊和里海类群的单系性。一个由三个环北极海洋物种组成的分支是大陆类群的姐妹群，而大西洋物种与其他物种的关系更远。里海形态多样的特有物种之间的小分子分化表明它们是近期形成的物种，而环极湖泊中表型上更一致的“冰川遗迹”物种（麦秆虫遗迹种组）表现出深度的分子分歧。对于长度可变的ITS2区域，直接优化和先验比对程序给出了相似的拓扑结构，尽管前一种方法提供了更好的整体分辨率。就分区布雷默支持率（PBS）而言，线粒体蛋白质编码基因对总树分辨率的贡献最大（83%）。然而，由于线粒体特征的协同遗传以及可能的基因渗入或祖先多态性情况，这一估计似乎部分是虚假的。
