基于部分18S rDNA,28S rDNA和COI基因序列的索科线虫亲缘关系

Molecular phylogeny of entomopathogenic nematodes(Mermi-thidae) inferred from DNA sequences of 18S rDNA,28S rDNA and COI genes

通过PCR扩增获得我国常见昆虫病原索科线虫6属10种18S rDNA、28S rDNA(D3区)和COI基因序列,结合来自GenBank中6属10种索科线虫的18S rDNA同源序列,用邻接法和最大简约法构建系统进化树。结果显示:12属索科线虫分为三大类群,第一大类群是三种罗索属线虫(Romanomermis)先聚在一起,再与两索属(Amphimermis)和蛛索属(Aranimermis)线虫聚为一支;在第二大类群中,六索属(Hexamermis)、卵索属线虫(Ovomermis)和多索属(Agamermis)亲缘关系最近,先聚在一起,再与八腱索属(Octomyomermis)和Thaumamermis线虫聚为一支。第三大类群由索属(Mermis)和异索属(Allomermis)线虫以显著水平的置信度先聚在一起,再与蠓索属(Heleidomermis)和施特克尔霍夫索属(Strelkovimermis)线虫聚为一支。从遗传距离看,基于3个基因的数据集均显示索科线虫属内种间差异明显小于属间差异,武昌罗索线虫(R.wuchangensis)和食蚊罗索线虫(R.culicivorax)同属蚊幼寄生罗索属线虫,其种间的遗传距离最小。

Mermithidae is a group of nematodes which parasitise insects and which have diversified morphological characters and host specificity. Because of the biological control value of these entomopathogenic nematodes, it is necessary to study their genetic variation and evolution. However, research on their classificationand evolutionary relationships has always been hindered by the overwhelming number of species, global distribution, and the lack of morphological specializations traditionally used in nematode classification. These problems have brought much confusion not only to the study of the phyologenetic relationships among groups, but also to the biological control of the nematodes. In this study, to evaluate the phylogenetic relationships of Mermithidae, the 18S ribosomal DNA fragment sequences, 28S ribosomal DNA fragment sequences and COI gene of ten species within six genera of Mermithidae were amplified using PCR techniques. The resulting data were combined with homologous sequences of ten species within six genera of Mermithidae downloaded from GenBank to form the analysis matrix. Molecular phylogenetic trees were constructed by using Neighbor-Joining （N J） and Maximum Parsimony （MP）. Results indicate that the twelve genera of Mermithidae may be grouped into three distinct clusters. In the phylogenetic trees, the congeners Romanomermis wuchangensis, R. culicivorax and R. sichuanensis （mosquito parasites） grouped with Amphimermis sp. （Homoptera parasites） and Aranimermis （spider parasites） into one cluster. In the second cluster, Ovomerm/s sinensis and Hexamermis agrotis （Lepidoptera parasites） were grouped together first, then grouped with Agamermis changshaensis and Agamermis xianyangensis （ Homoptera parasites）,finally with Ocwmyomermis huazhongensis （mosquito parasites） and Thaumamermis cosgrovei （isopod parasites）. In the third cluster, Mermis nigrescens （Orthoptera parasites） and Allomermis solenopsii （ant parasites） were grouped together first, then with Heleidomermis sp. （ceratopogonid parasites） and Strelkovimermis spiculatus （mosquito parasites）. Genetic distances showed that the intra-generic relationships were closer than inter-genus.