同域分布二倍体和四倍体泥鳅群体的遗传结构

Genetic structure of sympatric diploid and tetraploid loach (Misgurnus anguillicaudatus) populations

采用SRAP标记和线粒体DNA控制区测序方法对武汉和洞庭湖2个二倍体和四倍体泥鳅同域分布区4个泥鳅群体的遗传结构进行研究。SRAP分析结果表明,18对多态性引物组合在4个泥鳅群体中共检测到534个位点,每对引物组合检测的位点数为23～40个;各群体的Nei's基因多样性(h)和Shannon's信息指数(I)平均值分别为0.205～0.218和0.324～0.341,4个群体间的h以及I差异不明显;基于Nei's无偏遗传距离构建的UPGMA树显示,洞庭湖二倍体和四倍体泥鳅群体亲缘关系最近,先聚为一支,再与武汉四倍体泥鳅聚为一支,而武汉二倍体泥鳅聚为单独一支。测定了4个泥鳅群体40个个体线粒体DNA控制区序列片段(932～935bp),发现47个变异位点,共计29种单倍型。洞庭湖四倍体和二倍体泥鳅群体的核苷酸多样性(π)分别为0.898%和0.872%,明显大于武汉四倍体(π=0.465%)和二倍体(π=0.675%)。在同域分布二倍体和四倍体泥鳅群体中,洞庭湖四倍体遗传多样性略大于洞庭湖二倍体,武汉二倍体则明显大于武汉四倍体。AMOVA分析表明,泥鳅群体的遗传变异主要来自群体内(62.68%),群体间的变异达到37.32%;群体间成对固定指数FST及Kimura 2-parameter遗传距离均显示,洞庭湖四倍体与二倍体泥鳅群体无明显分化,其余群体间均存在显著分化。控制区序列单倍型Bayesian系统树与SRAP分析所揭示的4个泥鳅群体的亲缘关系相似。

SRAP（Sequence-related amplified polymorphism） markers and mitochondrial DNA control region sequencing were used to investigate genetic structure of four loach（Misgurnus anguillicaudatus） populations from two sympatric distribution areas of natural diploid and tetraploid loach-Dongting Lake（DT） and Wuhan city（WH） in China.The results from SRAP showed that a total of 534 loci were detected in four loach populations by 18 pairs of polymorphic primer combinations,and the numbers of amplified loci per primer pair ranged from 23 to 40.The averages of Nei＇s gene diversity（h） and Shannon＇s information index（I） of each population were from 0.205 to 0.218 and from 0.324 to 0.341,respectively,and there were no significant difference among h-values or I-values of four populations.UPGMA dendrogram tree,which was constructed based on the Nei＇s unbiased genetic distances,showed that DT diploid and DT tetraploid populations were firstly clustered into one branch and their relationships were the nearest,then WH tetraploid population was clustered to the branch.And the other branch contained only WH diploid population.Partial sequences of mitochondrial control region（932-935 bp） of 40 individuals representing four loach populations were sequenced.A total of 47 nucleotides were variable,resulting in a total of 29 haplotypes.Nucleotide diversities（π） of DT tetraploid and DT diploid within populations were 0.898% and 0.872%,respectively,and they were significantly larger than those of WH tetraploid（π=0.465%） and WH diploid（π=0.675%）.Within the sympatric diploid and tetraploid loach populations,genetic diversity of DT tetraploid was larger than that of DT diploid,and the genetic diversity of WH diploid was significantly larger than that of WH tetraploid.Analysis of molecular variance（AMOVA） indicated that the genetic variation mainly occurred within populations（63.55%）,and 37.32% of variation occurred among populations.Significant population subdivision was supported by both pairwise FST values and Kimura 2-parameter genetic distances between populations,except for no apparent subdivision between DT tetraploid and DT diploid.Phylogenetic tree through Bayesian inference from the control region sequence haplotypes was similar to the genetic relationship among four loach populations revealed by SRAP analysis.