5种蚌螨ITS2基因片段序列及其系统发育分析

Analysis gene sequences of ribosomal ITS2 and phylogeny from five unionicolid mites species(acari:unionicolidae:unionicola)

对5种蚌螨ITS2基因片段进行了序列测定,经比对后发现序列长度为258 bp（含gap）;其中保守位点186个,可变位点57个,总变异率达到22.1%,种间变异率在7.4%~14.9%之间;转换位点11个,颠换位点18个,转换颠换比值为0.61。A,G,C,T4种碱基的平均含量分别为29.5%、17.2%、18.1%、35.2%,平均嘧啶含量（64.7%）明显高于嘌呤含量（35.3%）,说明蚌螨的碱基偏向于AT。弯弓蚌螨（Unionicola arcuata）与Y纹蚌螨（U.ypsilophora）的种间遗传差异为16.2%,这个遗传差异的结果可以支持V idrine将沃蚌螨亚属从寄蚌螨亚属中分离的修订。以细羽螨（Proctophyllodes stylifer）作为外类群,使用邻接法（NJ）和最大似然法（ML）构建系统树,结果显示：5种蚌螨中的Y纹蚌螨（U.ypsilophora）可能是较早从祖先种分化出来的种;系统树的结果可以支持V idrine对寄蚌螨亚属的修订。

A nucleotide sequence analysis of ribosomal internal transcribed spacer 2（ITS2） gene fragment from five species unionicolid mites was performed.It was found that the aligned nucleotide fragment is 258 bp（including gap） in length,including 186 conserved sites,57 variable sites.The total variable rate is 22.1% and interspecific variable rate values vary from 7.4% to 14.9%.There are 11 transition sites and 18 transversion sites,and the ration of transition/transversion is 0.61.In the nucleotide sequence,the contents of A,G,C and T bases are 29.5%、17.2%、18.1%、35.2%,respectively.The percentages of A and T（64.7%） apparently higher than G and C（35.3%）.The result also indicated that there is a strong AT bias in bases for unionicolid mites.16.2% genetic divergences between Unionicola arcuata and U.ypsilophora,might support Vidrine＇s revision of the subgenus Parasitatax that Wolcottatax was divided from the subgenus Parasitatax.Using Proctophyllodes stylifer as outgroup,to make NJ and ML inferences,it revealed that U.ypsilophora may be the prior separation from ancestral species in five unionicolid mites species,which might also back Vidrine＇s taxon on the subgenus Parasitatax.