从12SrRNA基因片段序列研究20种蛇的系统发生关系

PHYLOGENETIC RELATIONSHIPS OF 20 SNAKE SPECIES BASED ON PARTIAL SEQUENCES OF 12S rRNA GENE

本文测定了中国产蛇亚目 2 0种蛇约 80 0bp的mtDNA 12SrRNA基因片段序列。所测序列与楔齿蜥的同源序列一起经ClustalX 1 8软件比对 ,共有 881个位点 ,其中变异位点有 4 94个。以楔齿蜥为外群 ,用NJ法构建了 4科 2 0种蛇的进化关系树 ,对这 2 0种蛇的系统发生关系作了初步探讨。研究结果表明 :所研究的 4个科2 0种蛇分成 4个支系。第一个支系包括蟒科的东方沙蟒和蟒 2种蛇 ;第二个支系为蝰科 3种蛇 ,即草原蝰、尖吻蝮、竹叶青组成一个单系群 ;眼镜蛇科的眼镜蛇和银环蛇构成第三个支系 ;游蛇科的 13种蛇构成了第四个支系 ,其中灰鼠蛇、乌梢蛇和赤链蛇组成一个支系 ,锦蛇属的 7种蛇组成一个单系群 ,然后它们与前一支系相聚。剩下的颈槽蛇属两种聚类后与赤链华游蛇构成一个支系 ,并与游蛇科其它蛇组成姐妹群。第四支系首先与第三支系眼镜蛇科聚类 ,第二支系蝰科构成了三、四支系眼镜蛇科和游蛇科的姐妹群 ,第一支系蟒科在系统树的最基部 。

The conservative morphological characters of snakes complicate the analysis of phylogenetic relationships among these organisms. Recently, some authors have employed DNA sequence analysis to examine phylogenetic relationships among snakes but little work on Chinas snakes has been published to date. The evolutionary history of snakes still remains controversial. In the current investigation, we try to shed light on these relationships via DNA sequence analysis of the mitochondrial 12S rRNA gene in 20 species of snake representing 13 genera from 4 families. About 800 bp of gene fragments from these species were sequenced, of which 494 variable sites were identified after combining and aligning the data with the homologous sequence of Sphenodon punctatus. A phylogenetic tree constructed using the neighbor joining method with Sphenodon punctatus as the outgroup indicates that the snakes examined in this study are clustered in four major clades corresponding to their four families. The first clade includes the 2 Boidae species, Erys tataricus and Python molurus biritattatus, the second is comprised of the 3 Viperidae species, Deinagkistrodon acutus, Trimeresurus stejneger and Vipera ursinii, the third contains the two Elapidae species, Naja naja and Bungarus multicinctus, and finally, the remaining 13 species of Colubridae form a large lineage in the phylogenetic tree. Consistent with the widely accepted opinion that it is the most primitive family among all current snakes, the Biodae branch diverges from the base of the tree. The Colubridae and Elapidae cluster together with a bootstrap value of 93 before they combine with the Viperidae lineage, strongly supporting the assumption that the Elapidae share an ancient ancestor with the Colubridae, rather than the Viperidae. Within the 13 species of the Colubridae, there are two major clades, the Rhabdophis and Sinonatrix clade, and the Zaocys, Ptyas, Dinodon and Elaphe clade, with bootstrap values of 99 and 98 respectively. In the second clade, seven species of Elaphe form a common branch before they cluster with other genera, contrary to Dessauers assumption of the polyphyletic origin of this genus.