Abstract: The method of SAFLP (single-enzyme amplified fragment length polymorphism) was optimized for Mermithidae in this study. The genetic relationships among 11 species or subspecies belonging to six genera of Mermithidae and common in China were detected using this method. Two kinds of restriction endonucleases were used in this study, and the results showed that EcoRⅠ was more suitable than MseⅠ for SAFLP analysis of Mermithidae. In total 225 bands (form 250 to 1 650 bp) were amplified using three EcoRⅠ primers each with three selective bases. Nei's similarity coefficients and genetic distance (0.1980－0.4554） were calculated by NTsys-PC2.1 software and the phylogenetic tree was constructed with the method of UPGMA. The results indicated that the eleven species/subspecies of Mermithidae could be distinguished with SAFLP markers and were grouped into two distinct clusters. Two major groups of genera are observed in the phylogenetic tree: Romanomermis + Octomyomermis;  ((Hexamermis+Ovomermis) + Agamermis)+Amphimermis. Comparatively, the genetic distance of different species or subspecies, which are from closer area in the same genera, is smaller in Octomyomermis and Amphimermis. The result of this experiment is similar to that of the morphologic taxonomy system and provides further evidence for the studies of phylogenetic relationship among species or genera of Mermithidae. The results suggest that this optimized SAFLP is suitable for analysis of phylogenetic relationship and taxonomy among species of Mermithidae.

Key words: Entomopathogenic nematodes, Mermithidae, SAFLP, phylogenetic tree, phylogenetic relationship, China