STUDIES ON THE STRUCTURE OF THE MITOCHONDRIAL DNA CONTROL REGION AND PHYLOGENETIC RELATIONSHIPS OF THE SUBFAMILY BOTIINAE
沙鳅亚科鱼类线粒体DNA控制区结构分析及系统发育关系的研究

Belonging to Cobitidae of Cypriniformes,the subfamily Botiinae is a group of small or middle freshwater fishes dwelling in slow to moderately swift waters,and many of them are common aquarium species.The classification of Botiinae fishes is controversial among different authors.Fang(1936)and Nalbant(1963)divided Botiinae into two genera,Botia and Leptobotia,while Chen(1980)separated it into three,Botia,Parabotia and Leptobotia.Up to now,there was no study conducted on the structure of mitochondrial DNA control region and the molecular phylogenetic relationship of the subfamily Botiinae.In the present study,the structure of the control region sequences was analyzed for fourteen species representing the three genera of Botiinae.Similar to other fishes,the control region of Botiinae is composed of three domains,the extended termination associated sequence((ETAS)domain,) the Central conserved domain(CD)and the Conserved sequence block(CSB).The ETAS domain is very rich((73.3%) in the) contents of A and T,while the CD domain is much rich(36.3%)in G and C.A termination-associated sequence TAS(TACATA)and its reverse complementary sequence(ATGTAT)were found in the ETAS domain,and the conserved sequence in this domain is ETAS 1.The CD domain is highly conserved,and three conserved sequences were identified,CSB-F,CSB-E and CSB-D.Three conserved sequences were identified in the CSB domain,CSB-1,CSB-2 and CSB-3.With Myxocyprinus asiaticus as outgroup,compared with members of Nemacheilinae,Cobitinae and Homalopteridae as well,the phylogenetic relationship of Botiinae was analyzed using the neighbor-joining(NJ)method in MEGA2.1,the maximum parsimony(MP)method in PAUP~*4.0b10 and the maximum likelihood(ML)method in TREE-PUZZLE 5.0.The results showed that the subfamily Botiinae is monophyletic and the confidence levels in the three analysis methods were 88%in NJ,57%in MP and 97% in ML respectively.It also supported that Botiinae contains three genera,Botia,Parabotia and Leptobotia,since each of these genera formed a monophyly,which were supported with 100%,65%and 78%of bootstrap values in NJ method and 100%,75%and 70%of Quartet puzzling values in ML method.In MP analysis,the bootstrap value supporting monophyly of the genus Parabotia was less than 50%,while for Botia and Leptobotia,the values were 100%and 56%.Based on the results of molecular phylogenetic analysis,morphological comparison and geographical distribution of Botiinae fishes,it was suggested that Botia is the most primitive genus,Parabotia the second,and Leptobotia the most specialized.