Comparative evolutionary analysis of insects using mitochondrial genes

In this study, a comparative analysis of select insect mitochondrial DNA (mtDNA) representing five insect orders (Diptera, Lepidoptera, Hemiptera, Ephemeroptera and Coleoptera) consisting of 24 different species in an effort to study a common set of genes and to understand the evolution of mitochondrial genome with respect to Cytochrome Oxidase subunit 1 (CO1), 16srRNA and 12srRNA gene sequences was done. To compare the similarity between closely related insect mitochondrial genome sequences, pairwise distance matrix was constructed using the MEGA tool. CO1, 16srRNA and 12srRNA sequences were used to construct a phylogenetic tree to determine the relationship among five insect orders. All the three sequences yielded a tree with branching patterns reflecting the expected pattern as insect species belonging to different orders were put into separate clades with an exception S. graminum & M. destructor being branched together in to a separate group. Based on the sequence similarity, insect species belonging to five different orders in general appear to be closely related. The tRNA species were identical in most species with an exception that two of the twenty four species had an additional tRNA gene. Based on this study we conclude that, although the gene types are very similar across these insect orders, significant differences in GC content perhaps suggest multiple mitochondrial ancestors.