中文摘要：

通过测定北美五倍子蚜（Melaphis rhois）3个种群共32个个体的mtDNACOI基因部分序列,分析北美倍蚜种群的遗传结构和变异。在测得的683bp COI基因序列中有75个变异位点（占所测核苷酸序列的11.0%）,4种核苷酸T、C、A、G的组成分别为40.2%、15.0%、32.5%和12.3%,具有较高的A＋T含量72.7%。M.rhois 32个个体的COI基因序列共产生10个单倍型,其中两个单倍型为主体单倍型,除阿肯色的一个个体与新泽西的6个个体共享一个单倍型外,其余单倍型单独或由同一种群的个体共享。AMOVA分析显示,五倍子蚜种群内核苷酸多样度低,种群间的遗传变异较高,分化显著。TCS网络图和聚类关系显示,五倍子蚜不同单倍型按地理分布形成明显的簇群,其中俄亥俄种群的单倍型单独构成一个分支,与其余两个种群关系较远;俄亥俄种群与其他两种群间的遗传距离也比较大,该种群可能属于五倍子蚜的一个亚种或新种。

英文摘要：

The population genetic differentiation of the species Melaphis rhois was examined by using mtD- NA COI gcne sequenccs. The 683bp sequences wcrc obtained from 32 individuals of three populations, a- mong which there are 75 variable sites, accounting for about 11.0% of the total measured nucleotide se- quence. The nucleotide composition were 40.2%, 15.0%, 32.5% and 12.3% for T, C, A and G, respec- tively, with a higher A＋T content （72.7%）. The total of 10 haplotypes were detected from 32 COI DNA sequences, among which two haplotypes were main haplotypes. Except that one individual from Arkansas USA shared the same haplotype with other six individuals from New Jersey, USA, the other haplotypes were shared by the different individuals from the same population, respectively. The analysis of AMOVA showed that the nucleotide diversity in M. rhois populations was low, and the population genetic differenti- ation was very significant. The NJ/MP phylogenetic trees and TCS network suggested that the haplotypes grouped into different clusters according to the geographical distribution, and the haplotypes from the Ohio population formed a single branch and had a farther relationship with the other two populations. Combined the analysis on the genetic distance between the Ohio population and the other two populations, it was con- sidered that the samples from the Ohio population might be a subspecies or a new species.