Time scale for cyclostome evolution inferred with a phylogenetic diagnosis of hagfish and lamprey cDNA sequences
Time scale for cyclostome evolution inferred with a phylogenetic diagnosis of hagfish and lamprey cDNA sequences
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DOI：
10.2108/zsj.23.1053
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发表时间：
2006-12-01
影响因子：
0.9
通讯作者：
Kuratani, Shigeru
中科院分区：
文献类型：
--
作者：
Kuraku, Shigehiro;Kuratani, Shigeru
圆口目包括两个目Myxiniformes（盲鳗）和Petromyzoniformes（七鳃鳗），其单系性已明确支持最近的分子系统发育研究。根据这一更新的脊椎动物的进化，我们进行了计算机进化分析，使用目前可用的cDNA序列的圆口动物。我们首先计算了GC含量在四倍退化网站（GC 4），这表明，一个非常高的GC含量是共享的所有七鳃鳗物种，我们调查，而没有显着的模式，在GC含量中观察到的任何调查的盲鳗物种。然后，我们估计的时间多样化的圆口动物进化使用核苷酸和氨基酸序列。在奥陶纪-志留纪-泥盆纪期间，Myxiniformes和Petromyzoniformes的目间分裂的分歧时间为4.7 - 3.9亿年前（Mya），在奥陶纪-第三纪期间，Myxinininae和Eptatretinae两个盲鳗亚科的分裂时间为90-60 Mya;二叠-三叠纪280-220百万年，七鳃鳗亚科Geotriinae和Petromyzoninae分裂;第三纪为30-10百万年，为七鳃鳗属Petromyzon和Lethenteron的分裂。这种进化结构表明，Myxiniformes和Petromyzoniformes分歧后不久，共同的祖先圆口动物从未来的nathostome谱系分裂。我们的研究结果还表明，在盲鳗和七鳃鳗谱系（特别是那些分布在北方半球）的亚家族内的多样化发生在白垩纪或第三纪。
The Cyclostomata consists of the two orders Myxiniformes (hagfishes) and Petromyzoniformes (lampreys), and its monophyly has been unequivocally supported by recent molecular phylogenetic studies. Under this updated vertebrate phylogeny, we performed in silico evolutionary analyses using currently available cDNA sequences of cyclostomes. We first calculated the GC-content at four-fold degenerate sites (GC4), which revealed that an extremely high GC-content is shared by all the lamprey species we surveyed, whereas no striking pattern in GC-content was observed in any of the hagfish species surveyed. We then estimated the timing of diversification in cyclostome evolution using nucleotide and amino acid sequences. We obtained divergence times of 470-390 million years ago (Mya) in the Ordovician-Silurian-Devonian Periods for the interordinal split between Myxiniformes and Petromyzoniformes; 90-60 Mya in the Cretaceous-Tertiary Periods for the split between the two hagfish subfamilies, Myxininae and Eptatretinae; 280-220 Mya in the Permian-Triassic Periods for the split between the two lamprey subfamilies, Geotriinae and Petromyzoninae; and 30-10 Mya in the Tertiary Period for the split between the two lamprey genera, Petromyzon and Lethenteron. This evolutionary configuration indicates that Myxiniformes and Petromyzoniformes diverged shortly after the common ancestor of cyclostomes split from the future gnathostome lineage. Our results also suggest that intra-subfamilial diversification in hagfish and lamprey lineages (especially those distributed in the northern hemisphere) occurred in the Cretaceous or Tertiary Periods.