基于BDNF和NT-3基因部分序列探讨爬行动物系统发生中的若干问题及扬子鳄分类地位

SEVERAL QUESTIONS ON THE REPTILE′S PHYLOGENY AND THE PHYLOGENETIC POSITION OF CHINESE ALLIGATOR INFERRED FROM THE BDNF AND NT-3 GENES PARTIAL SEQUENCES

通过两个核基因NT-3基因(约740bp)和BDNF基因部分序列(约720bp)的分析,对爬行动物的系统发生关系中鳄类与鸟类和哺乳类系统发生关系、龟类在爬行动物系统发生中的位置以及扬子鳄属的划分等问题进行探讨。结果表明,在NT-3基因序列中,有307个位点存在变异(约为总位点数的47·3%),BDNF基因序列有256个变异位点(约为38·79%);构建的分子系统树显示,NT-3和BDNF基因以及两序列合并数据后所得系统树的拓扑结构均支持鳄类和鸟类聚为一支构成姐妹群,鳄类与蜥蜴类尽管在形态上非常相似,但它们的亲缘关系仍然较远;同时支持把龟鳖类作为鳄类和鸟类支系的姐妹群,支持把蜥蜴类(有鳞类)放在爬行类系统发生树的基部,而不是龟鳖类作为现代爬行类中最基部的1支。对扬子鳄分类地位的研究结果支持在现存的鳄类中扬子鳄与密西西比鳄的亲缘关系较近的结论。

This paper researched some questions on the reptiles phylogeny inferred from the BDNF and NT-3 nuclear genes partial sequences, such as the phylogenetic relationships of crocodiles, avians and mammals; the classification status of Testudinate in Reptila and the classification of Chinese alligator. Molecular phylogenetic trees were reconstructed using Maximum Parsimony （MP）. The results showed： there were 307 variable sites in NT-3 gene （47.3% of the total nucleotide sites in NT-3 gene） and 256 variable sites in BDNF gene （38.79% of the total nucleotide sites in BDNF gene）. The results also showed that the Crocodilinus and Aves became the sister cluster, which revealed that they had the closest relationship. Whereas Crocodilinus and Lacertidae had the similar morphology, they had the further relationship. The results also ,sustained that the tortoises were clustered to Crocodilinus and Ayes. The clades of Lacertidae was the basal one in Reptila phylogeny tree. The research results for Alligator sinensis classification sustained the Chinese alligator and Alligator mississippiensis had the closest relationship among five Crocodilinus.