Complete mitochondrial genomes and eutherian evolution.
Complete mitochondrial genomes and eutherian evolution.
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DOI：
10.1023/a:1023926013667
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发表时间：
2002-12-01
影响因子：
1.9
通讯作者：
Corneli, Patrice Showers
中科院分区：
文献类型：
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作者：
Corneli, Patrice Showers
最近的大规模核DNA系统发育支持了现代真兽类之间非常规的序间关系以及分歧日期（100 mya），这些日期基本上早于白垩纪/新生代（K/T）边界（65-70 mya）附近现代真兽类化石的首次出现。为了与核数据进行比较，我分析了来自 53 个真兽类群的 12 个完整线粒体 DNA (mtDNA) 蛋白质编码基因 (10,677 bp)，使用最大似然方法来估计模型参数 (GTR+I+GAMMA) 并优化拓扑和分支长度估计。尽管线粒体 DNA 最大似然树与核 DNA 树非常相似，但它只是七种统计上无法区分的 (DELTA lnL le 1.747) 树之一，每种树都表明不同的进化关系。这个包含 53 个分类单元的数据集和另一个包含 56 个分类单元的数据集没有为单系非洲兽亚纲提供统计上显着的支持。事实上，这些线粒体 DNA 序列无法支持核数据所暗示的三个假定的真兽亚纲（Afrotheria、Laurasiatheria 或 Euarchontoglires）的单系性。与描述家庭之间关系的得到良好支持的分支相比，那些描述序间关系的分支非常短，而且只得到了微弱的支持。这些序列和在已知树下模拟的序列都不能完全解决任何序间关系。即使是 mtDNA 蛋白质编码基因两倍长 (22kb) 的模拟序列也太短且太饱和，无法解析最深和最短的序间关系。此外，哺乳动物线粒体 DNA 序列似乎与分子钟和四重体测年假设有显着差异。与最近的核 DNA 研究不同，我发现 mtDNA 基因本身不足以描述真兽树底部的关系或分歧时间。
Recent large-scale nuclear DNA phylogenies have supported unconventional interordinal relationships among modern eutherians as well as divergence dates (100 mya) that substantially predate the first appearance of fossils from modern eutherians near the Cretaceous/Cenozoic (K/T) boundary (65-70 mya). For comparison to the nuclear data, I analyzed 12 complete mitochondrial DNA (mtDNA) protein-coding genes (10,677 bp) from 53 eutherian taxa, using maximum-likelihood methods to estimate model parameters (GTR+I+GAMMA) and to optimize topology and branch-length estimates. Although closely resembling the nuclear DNA trees, the mtDNA maximum-likelihood tree is just one of seven statistically indistinguishable (DELTA lnL le 1.747) trees, each suggesting different evolutionary relationships. This 53-taxon data set and another including 56 taxa provide no statistically significant support for a monophyletic afrotherian clade. In fact, these mitochondrial DNA sequences fail to support the monophyly of three putative eutherian divisions suggested by the nuclear data (Afrotheria, Laurasiatheria or Euarchontoglires). By comparison to well-supported branches describing relationships among families, those describing interordinal relationships are extremely short and only tenuously supported. Neither these sequences, nor sequences simulated under a known tree, fully resolve any interordinal relationship. Even simulated sequences that are twice as long (22kb) as mtDNA protein-coding genes are too short and too saturated to resolve the deepest and shortest interordinal relationships. Further, the mammalian mtDNA sequences appear to depart significantly from molecular-clock and quartet dating assumptions. Unlike recent nuclear DNA studies, I find that mtDNA genes, by themselves, are inadequate to describe relationships or divergence times at the base of the eutherian tree.