6个不同海域文蛤地理群体的亲缘关系分析

Genetic relationship analysis of six Meretrix meretrix populations from different sea areas

为探究中国辽东半岛海域（辽宁群体）、长江口及其两翼海域（江苏群体）、台湾海峡西部海域（福建群体）、珠江口及其两翼海域（广东群体）、北部湾海域（广西群体）以及日本伊势湾海域（三重群体）6个不同海域文蛤（Meretrix meretrix）地理群体的亲缘关系,采用18S rRNA基因、线粒体细胞色素氧化酶c亚基Ⅰ（COⅠ）及16S rRNA基因3种分子标记进行序列测定与分析。测序结果显示,3种基因序列长度分别在1 854、658、596 bp左右;18S rRNA基因碱基组成无偏异,序列较为保守;COⅠ与16S rRNA基因A＋T平均含量明显大于G＋C含量,符合线粒体基因组成特征。通过Meg Align软件比对6个地理群体文蛤,序列相似百分比分别为99.7%~100.0%（18S）、91.7%~99.8%（COⅠ）、90.2%~99.8%（16S）,其中三重文蛤序列差异最大;以文蛤属的帘文蛤（Meretrix lyrata）作外群,采用MEGA 5.03软件中相邻连接法（NJ）构建系统发育树显示,我国沿海5个文蛤群体聚为一枝且与日本三重文蛤分开,自展值分别为67%（18S）、99%（COⅠ）、98%（16S）;我国沿海5个文蛤群体中,辽宁、江苏、福建文蛤群体首先聚在一起,其次是广西文蛤群体,最后是广东文蛤群体。研究结果表明,辽宁、江苏、福建文蛤群体同源性较高,亲缘关系最近;广西文蛤群体、广东文蛤群体与我国其它文蛤群体间遗传差异较大,地理遗传分化明显;而日本三重文蛤与我国沿海文蛤可定为文蛤的2个地理亚种。

In this paper,18 S ribosomal RNA gene,mitochondrial cytochrome oxidase c subunit I（ COⅠ）gene and 16 S rRNA gene sequences of six different Meretrix meretrix populations from Liaodong Peninsula sea area（ Liaoning population）,the Yangtze Estuary and its two wing sea areas（ Jiangsu population）,Western sea area of Taiwan Strait（ Fujian population）,Pearl River Estuary and its two wing sea areas（ Guangdong population）,Beibu Bay sea area（ Guangxi population） and Ise Bay sea area,Japan（ Mie population） were sequenced and analyzed to study their genetic relationship. The genetic background of different Meretrix meretrix populations was analyzed in molecular level,to provide theoretical basis for germplasm resources research and breeding. Results of sequence analysis showed that： the length of three genetic sequences was about 1 854 bp,658 bp and 596 bp respectively; base composition of 18 S rRNA gene was unbiased,and its sequence was conservative; COⅠ gene had 73 variable sites,among which 30 were parsim-informative sites,the average content of A ＋ T was 66. 0%; 16 S rRNA gene had 71 variable sites,among which 11 were parsim-informative sites,the average content of A ＋ T was 65. 9%. A ＋ T content was obviously higher than G＋ C content in both CO Ⅰ and 16 S rRNA gene,which was in accordance with features of mitochondrial genes. Gene sequences of six Meretrix meretrix populations were aligned by Meg Align,the percentage of sequence identity was 99. 7%- 100. 0%（ 18S）,91. 7%- 99. 8%（ CO Ⅰ）,90. 2%- 99. 8%（ 16S）respectively. Meretrix meretrix from Mie had the largest difference. Phylogenetic trees were constructed by MEGA5. 03 using adjacent connection method（ NJ） with Meretrix lyrata as outgroup. Five Meretrix meretrix populations from China coast areas were clustered into one clade and separated from Meretrix meretrix from Mie,Japan,bootstrapping value was 67%（ 18S）,99%（ CO Ⅰ） and 98%（ 16S） respectively; among the five populations from China coast areas,Meretrix meretrix from Liaoning,Jiangsu,Fujian clustered together first,and then the population from Guangxi,the last was the population from Guangdong. Results indicated that： Meretrix meretrix from Liaoning,Jiangsu,Fujian had a higher homology and their genetic relationship was the closest; a larger genetic difference was found among Meretrix meretrix from Guangxi,Guangdong and other populations from China,and their geographic genetic differentiation was obvious; Meretrix meretrix from Mie,Japan and China coast areas could be described as two geographic subspecies.