【摘要】 利用线粒体细胞色素氧化酶亚基I(cytochromeoxidaseI ,COI)基因序列对北京地区和江汉湖群部分湖泊萼花臂尾轮虫 (Brachionuscalyciflorus)种群遗传结构进行了初步分析。以特异引物进行PCR扩增 ,获得了 661bp的基因片断序列 ,所得序列与Genbank中B .calyci florusCOI序列的同源性为 82 %— 93%。在 6个种群中 ,共获得了 1 5种单元型。序列分析结果表明 ,不同季节单元型之间的遗传距离较大 ( 0 .2 4 8— 0 .2 63) ,而在同一季节单元型之间遗传距离较小 ( 0 .0 0 2— 0 .0 31 )。种群遗传结构分析表明 ,各种群之间无共享的单元型 ,同一季节不同湖泊种群之间存在着一定程度的遗传分化 ,但未按照地理位置形成明显的地理格局。按采样时间分组进行AMOVA分析 ,组间差异高达 94.0 9% ;DH I与其他种群之间存在着明显的遗传分化。同一湖泊不同季节样品之间 ,遗传变异较大 ,这表明在同一湖泊存在着不同基因型的轮虫休眠卵 ,当环境条件发生了变化后 ,不同基因型之间会发生更迭。更多还原

【Abstract】 Phylogeography structure of Brachionus calyflorious populations sampled from several lakes in Beijing and Jianghan lake region were studied on mitochondrial cytochrome oxidase subunit I gene (COI) partial sequences.661bp of the COI gene were amplified and sequenced.Sequences were moderately A+T rich (mean A+T content= 65.6% ),and the mean A+T contents were 56.8% , 58.3% and 81.4% in the first,second and third codon positions of the genetic codes,respectively.The A+T contents of DH-1 and DH-2 were lower than those of other haplotypes.15 haplotypes were identified from 37 samples with 163 variation sites.According to the sample time,these haplotypes could be divided into two groups,“March”and “October”.Most substitutions of nucleotides occurred between the “March”group and “October” group.On the contrary,there were fewer substitutions among haplotypes within the same group.Calculated with Kumur 2-parameters model by software MEGA,pairwise sequences genetic distances among sequences ranged from 0.002 to 0.263.Pairwise sequences genetic distances among haplotypes sampled in same season ranged from 0.002 to 0.031;however,genetic distances among haplotypes sampled in different seasons were rather high,ranging from 0.248 to 0.263.There was no shared haplotype among different populations.The population genetic structure among different populations was analyzed with AMOVA method using Arelequin software.The genetic divergences between the “March” and “October”group,among populations within same groups and among haplotypes within the same population were 94.09%(P<0.01),3.33%(P<0.01)and 2.58%(P<0.01),respectively.According to geographical position,populations sampled in October were divided into “Northern”and “Southern” groups.Genetic divergences between the “Northern” and “Southern”group,among populations within the same groups and among haplotypes within the same population were -32.77%(P<0.01),75.19%(P<0.01)and 57.58% (P<0.01),respectively.Most genetic variations occurred within the same groups.There were rather strong gene flows among B.calyflorus populations in Beijing and the lakes in Jianghan region.The results showed there was no positive correlation between genetic and geographic distances.Neighbor-joining tree phylograms also showed that there were apparent genetic divergences between the “March” group and the “October” group.Furthermore,the neighbor-joining phylogram of these sequences showed that there was no localized differentiation.The Beijing lakes are far from the lakes in Jianghan region and there is no direct surface connection between their water flows,suggesting the importance of other environmental factors in the gene flow process of the B.calyflorus populations.Future research should consider the role of waterfowls and winds on the gene flow of B.calyflorus.Some researchers have speculated that sometimes there is no direct relationship between population migrations and gene flows.When organisms enter new habitats,population growth was dominated by biotic and abiotic factors,if the environment proved unfavourable the population would decline or become extinct.The apparent genetic divergences between the “March” group and “October” group suggested that there were several kinds of genotypes of rotifer resting eggs,all acclimatized to different environments conditions in Donghu Lake,Wuhan.Along with varied enviromental conditions,resting eggs of given genotype would hatch in turn,so the genotypes of free-living rotifers would change in the lake accordingly.This hypothesis could be explained by the incomplete genetic discontinuity model and complete genetic discontinuity model.Researchers should,therefore,take into consideration the effect of sampling date on the phylogeographic structure of zooplankton when carrying out this type of investigation.更多还原