Intra-individual variability of ITS regions in entomopathogenic nematodes (Steinernematidae: Nematoda): implications for their taxonomy

The internal transcribed spacers of rDNA are among the most important molecular markers used in the taxonomy and phylogeny of entomopathogenic nematodes. However, their ease of use and the results they provide can be confounded by the presence of intra-individual variability. In the present study we screened 40 strains of S. feltiae and S. kraussei and nine strains from the glaseri group. In two selected strains of S. feltiae, and one strain each of S. kraussei and S. glaseri, PCR products of four virgin females were cloned, and five clones per individual female were sequenced and analyzed. In S. feltiae, intra-individual variability was compared with intraspecific variability. We revealed a high frequency of intra-individual variability, which reached 65 % in S. feltiae, 30 % in S. kraussei, and almost 90 % in the glaseri group. Analysis of the cloned products showed intra-individual variability in each of the tested strains and individuals. Maximum within-individual variability was over 1 % in S. feltiae and S. kraussei, and in S. glaseri reached up to 4 %. In S. feltiae, intra-individual variability equaled the variability among S. feltiae strains from different parts of the world. Our data show that intra-individual variability in the ITS regions is quite frequent in entomopathogenic nematodes. The implications of this fact to the group taxonomy are discussed.