Johnson K P, Sorenson M D
Department of Ecology, Evolution, and Behavior, and Bell Museum of Natural History, University of Minnesota, St. Paul, USA.
Mol Phylogenet Evol. 1998 Aug;10(1):82-94. doi: 10.1006/mpev.1997.0481.
Rates of sequence evolution were estimated for the cytochrome b (cyt b) and NADH dehydrogenase sub-unit 2 (ND2) genes using a phylogeny of the dabbling ducks (Tribe: Anatini) and outgroups. This speciose group was densely sampled, reducing the impact of undetected homoplasy on rate comparisons. Phylogenies based on sequences of the two gene regions and various weighting schemes differed, but most of the differences involved weakly supported nodes. In addition, partition homogeneity tests show that these differences were not due to statistically significant conflict between the data sets. Cyt b and ND2 also showed similar rates and types of both nucleotide and amino acid substitutions. For both genes, substitutions between isoleucine and valine and between alanine and threonine were most common; both of these substitution types are the result of A-G transitions at first positions of codons. Rates of sequence evolution varied substantially and significantly among nucleotide positions, and even within a given codon position (first, second, or third), rates were significantly heterogeneous among sites. Within Anatini, cyt b and ND2 show similar levels of variation and homoplasy, and are equally useful for reconstructing the species level phylogeny of this group.
利用河鸭族（Anatini）及其外类群的系统发育关系，估计了细胞色素b（cyt b）基因和烟酰胺腺嘌呤二核苷酸脱氢酶亚基2（ND2）基因的序列进化速率。这个种类繁多的类群样本密集，减少了未检测到的同塑性对速率比较的影响。基于两个基因区域序列和各种加权方案构建的系统发育关系有所不同，但大多数差异涉及支持度较弱的节点。此外，分区同质性检验表明，这些差异并非由于数据集之间存在统计学上的显著冲突。Cyt b和ND2在核苷酸和氨基酸替换的速率及类型上也表现出相似性。对于这两个基因，异亮氨酸和缬氨酸之间以及丙氨酸和苏氨酸之间的替换最为常见；这两种替换类型均是密码子第一位发生A - G转换的结果。序列进化速率在核苷酸位置之间差异很大且显著，甚至在给定的密码子位置（第一位、第二位或第三位）内，位点之间的速率也存在显著的异质性。在河鸭族内部，cyt b和ND2表现出相似程度的变异和同塑性，对于重建该类群的物种水平系统发育关系同样有用。
