Genetic relatedness of six South Indian agriculturally important moth species (Lepidoptera: Noctuoidea) based on 28S rRNA-D2 region sequence analysis

Molecular phylogenetic evidence from 28S rRNA-D2 expansion segment was used to facilitate differentiation of six different pest species of moths from the superfamily Noctuoidea. The expansion segment of the large ribosomal subunit of 28S rRNA-D2 region was amplified, sequenced and used to construct a phylogenetic tree on the basis of N-J phylogeny method. The topology on the basis of this phylogenetic tree supported a large monophyly for Helicoverpa armigera Hub. and Spodoptera litura Fab. in one cluster, Euproctis fraterna More, Amsacta albistriga Walker and Pericallia ricini Fab. in another cluster, and Earias vitella Fab. in third cluster. The rRNA sequences were also analyzed for the genetic variation using the predicted secondary structure models for all the six species. This analysis revealed variation in the structure of D2 expansion segments at its various arms. Though the multiple sequence alignment showed one large cluster with three subclusters and 96% homology among these pest species, the predicted secondary structure models did not show any such close relationships. These results reflect the functional diversity occurred due to the changes acquired slowly at the rRNA structure to perform their function during evolution rather than the homology in the nucleotide sequences or rRNA morphometry among different species of insects.