Cylindrotheca closterium Is a Species Complex as Was Evidenced by the Variations of rbcL Gene and SSU rDNA  

作　　者：LI Haitao YANG Guanpin SUN Ying WU Suihan ZHANG Xiufang 

机构地区：[1]College of Marine Life Sciences, Ocean University of China, Qingdao 266003, P. R. China

出　　处：《Journal of Ocean University of China》2007年第2期167-174,共8页中国海洋大学学报（英文版）

基　　金：This research was financially supported by an open project of The Key Laboratory of Mariculture of The Ministry of Education of China affiliated to 0cean umversity of China(200405);by the National Natural Science Foundation of China(30471318,40176028).

摘　　要：The genus Cylindrotheca consists of a small group of marine diatoms with a few species described. Eleven isolates of diatoms identified as Cylindrotheca closterium morphologically were obtained from Jiaozhou Bay with their nuclear-encoded small-subunit ribosomal RNA （SSU rDNA） and chloroplast-encoded rbcL gene sequences determined in this study. Interestingly, very high sequence divergences of SSU rDNA and rbcL gene were found among these isolates, and numerous nucleotide variation of rbcL gene caused relatively few variation of deduced amino acid sequence. Phylogenetic analyses based on SSU rDNA and rbcL gene, respectively, grouped the isolates into 6 clades. Phylogenetic tree of SSU rDNA placed all the Cylindrotheca isolates together, separating them into two lineages clearly. LineageⅠ was composed of the eleven C. closterium isolates obtained in this study together with another C. closterium isolate, but some clades were not well supported. LineageⅠwas contained two C. closterium isolates and one C. fusiformis isolate. Phylogenetic analysis of rbcL gene also separated the Cylindrotheca isolates into two well-defined lineages. The eleven C. closterium isolates formed a lineage and all clades were supported strongly. Statistical comparisons of SSU rDNA indicated that the average distance within lineageⅠwas significantly higher than that of other microalgae species （P 〈0.01）. These results suggested the existence of cryptic species within C. closterium.The genus Cylindrotheca consists of a small group of marine diatoms with a few species described. Eleven isolates of diatoms identified as Cylindrotheca closterium morphologically were obtained from Jiaozhou Bay with their nuclear-encoded small-subunit ribosomal RNA (SSU rDNA) and chloroplast-encoded rbcL gene sequences determined in this study. Interestingly, very high sequence divergences of SSU rDNA and rbcL gene were found among these isolates, and numerous nucleotide variation of rbcL gene caused relatively few variation of deduced amino acid sequence. Phylogenetic analyses based on SSU rDNA and rbcL gene, respectively, grouped the isolates into 6 clades. Phylogenetic tree of SSU rDNA placed all the Cylindrotheca isolates together, separating them into two lineages clearly. Lineage I was composed of the eleven C. closterium isolates obtained in this study together with another C. closterium isolate, but some clades were not well supported. Lineage II contained two C. closterium isolates and one C. fusiformis isolate. Phylogenetic analysis of rbcL gene also separated the Cylindrotheca isolates into two well-defined lineages. The eleven C. closterium isolates formed a lineage and all clades were supported strongly. Statistical comparisons of SSU rDNA indicated that the average distance within lineageⅠwas significantly higher than that of other microalgae species (P < 0.01). These results suggested the existence of cryptic species within C. closterium.

关 键 词：Cylindrotheca closterium species complex rbcL gene  SSU rDNA 

分 类 号：Q949.271[生物学—植物学]