广东地区宽鳍鱲种群遗传变异和亲缘地理

POPULATION GENETIC VARIATION AND PHYLOGEOGRAPHY OF ZACCO PLATYPUS IN GUANGDONG REGION

通过分析88尾采自广东境内9条水系的宽鳍鱲(Zacco platypus)线粒体DNA(mtDNA)细胞色素b(Cytb)基因全序列,初步研究其种群遗传变异和地理格局。所测定的Cytb基因全序列长1140bp,其中变异位点98个,简约信息位点75个。共检测到33个单倍型,除鉴江种群只有1个单倍型外,其余8条水系均有多个单倍型。北江、流溪河、鉴江、北流河和罗定江等5个种群有共享单倍型Hap11,罗定江和北流河之间共享了单倍型Hap4,东江与流溪河共享Hap6,而韩江和榕江共享单倍型Hap29。种群单倍型多样性的平均值(h)为0.908,核苷酸多样性的平均值(π)为0.01961,表现出较高的遗传多样性。系统发育分析(NJ树)显示,宽鳍鱲种群33个单倍型可分为2个分支,其中来自珠江水系(北江、东江、流溪河、罗定江和北流河)和广东西部独立入海水系(鉴江和漠阳江)的宽鳍鱲种群聚为一支(分支A),广东东部独立入海水系(韩江和榕江)种群聚为另外一支(分支B)。2分支间的遗传距离和碱基差异率均较高(0.0517—0.0549,5.35%—6.49%),明显大于分支A内(0.0012—0.0099,0.26%—2.11%)和分支B内的值(0.0027,1.58%),但远小于宽鳍鱲与外类群间的遗传距离和碱基差异率(0.0945—0.1912,8.77%—17.11%)。这表明分支A与B之间已有明显的遗传分化,但分化程度未达到物种级水平。韩江和榕江的种群相对独立,推测可能与莲花山脉的阻隔有关。根据单倍型网络图推测,流溪河可能是广东中西部地区宽鳍鱲的扩散中心,分别向珠江水系的西江、北江和东江扩散,再向鉴江和漠阳江扩散;另外由扩散中心经东江到榕江再向韩江扩散。分子变异分析(AMOVA)表明,种群间的遗传变异占38.50%,种群内的遗传变异占66.24%。中性检验和歧点分布分析皆表明广东境内9条水系的宽鳍鱲在整个种群上保持相对稳定,没有发生明显的种群扩张。

The population genetic variation and phylogeographical patterns for 88 individuals of Zacco platypus from 9 drainage systems in Guangdong region were investigated preliminarily based on nucleotide sequences of mtDNA cytochrome b gene.The complete cytochrome b gene sequences were detected to be 1140 base pairs,with 98 variable sites,75 parsimony informative sites and 33 haplotypes.Only one haplotype was found in the population of the Janjiang River,while multiple haplotypes were shown in the populations of the rest 8 drainages.Hap11（BJ4_BL3_LX3_LD2_JJ1） were shared by the five populations in the Beijiang River,the Liuxi River,Luoding River,the Beiliu River and Jianjiang River,Hap4（LD1_BL1） were shared by the populations in the Luoding River and the Beiliu River,Hap6（DJ1_LX2） were shared by the populations in the Liuxi River and the Dongjiang River.Hap29（HJ4_RJ4） were shared by the populations in the Hanjiang River and the Rongjiang River.It showed a high genetic diversity,for the average value of haplotype diversity（h） and nucleotide diversity（π） were 0.908 and 0.01961,respectively.Phylogenetic tree estimated by neighbor-joining（NJ） method indicated that 33 haplotypes of Zacco platypus populations were divided into two lineages.Lineage A contained the populations in both the Pearl River drainage systems（including the Beijiang River,the Dongjiang River,the Liuxi River,the Luoding River and the Beiliu River） and the Western Guangdong drainage systems（in-cluding the Jianjiang River and the Moyang River）.The populations in the Eastern Guangdong drainage systems（including the Hanjiang River and the Rongjiang River） were composed of Lineage B.The genetic distance with the range from 0.0517 to 0.0549 and the percentage divergence of sequences with the scope from 5.35% and 6.49% between these two lineages were relatively higher than those within Lineage A（0.0012—0.0099,0.26%—2.11%）and Lineage B（0.0027,1.58%）.However,the value of the genetic distance and the percentage divergence of sequences between these two lineages were much lower than those between Zacco platypus and outgroups（0.0945—0.1912,8.77%—17.11%）.The result showed that there were a huge genetic differentiation between Lineage A and B,while the differentiation degree did not approach to the level of Species differentiation.Owning to the geographical obstruction of the Lianhua Mountains,the populations from the Hanjiang River and the Rongjiang River were relatively independent.According to the haplotype network,this fish from the middle and west regions in Guangdong Province had probably originated from the Liuxi River,and spread to the Xijiang River,the Beijiang River,and the Dongjiang River of the Pearl River drainage systems respectively,then continued to spread to the Jianjiang River and the Moyang River.In addition,the fish can also spread from the center,through the Dongjiang River to the Rongjiang River and the Hanjiang River.Analysis of molecular variance（AMOVA） revealed that genetic variation among the populations within regions was 38.50%,and that within the populations was 66.24%.Tests of neutrality and mismatch distribution suggested the whole population of Zacco platypus from 9 drainage systems in Guangdong region were relatively stable,without obvious population expansion.