Hierarchical Analysis of Variation in the Mitochondrial 16SrRNA Gene among Five Different Insect Orders

Abstract

Nucleotide sequences from a 500 bp region of the 16SrRNA gene were analyzed for ten insect pests of five different orders to examine the patterns of variation within the gene fragment and the taxonomic levels for which it showed maximum utility in phylogeny estimation. A hierarchical approach was adopted in the study through comparison of levels of sequence variation among taxa at different taxonomic levels. Among them, partial 16SrRNA gene was amplified in ten insects of five different orders. As previously reported for many holometabolous insects, the 16SrRNA gene data is reported here for 5 different orders were highly AT-rich and exhibited strong site-to-site variation in substitution rate. The partial 16SrRNA genes of five out of ten insects were reported first time. Primers were made from blasting 2 different genera of the order Diptera. These primers were proven to be universal as it amplified the partial 16SrRNA gene in ten different insects across five different orders, Diptera, Coleoptera, Heteroptera, Lepidoptera and Hymenoptera. Later, a phylogenetic tree was also constructed for understanding and analyzing the relation of above five orders. This study resulted in unusual findings which were as follows: All the species of Drosophila of order Diptera were evolutionary more closely related to Dysdercus koenigii of order Heteroptera than Bactrocera cucurbitae of Drosophilan order, Diptera in terms of partial 16SrRNA gene sequence. Similarly, Spodoptera litura and Helicoverpa armigera belonged to same family Noctuidae whereas Pieris brassicae belonged to family Pieridae. All belonged to order Lepidoptera. The results showed that Spodoptera litura in terms of partial 16SrRNA gene sequence was evolutionary more close to Pieris brassicae than Helicoverpa armigera .