Novel gene rearrangement pattern in the mitochondrial genomes of Torleya mikhaili and Cincticostella fusca (Ephemeroptera: Ephemerellidae).

The mayfly family Ephemerellidae (Insecta: Ephemeroptera) is distributed around the world and has very high species diversity. However, its evolution pattern of mitogenome and phylogenetic relationships within Ephemeroptera remain unclear. In this study, the complete mitochondrial genomes (mitogenomes) of Torleya mikhaili (15,042 bp) and Cincticostella fusca (15,135 bp) were firstly determined and analyzed. Two ephemerellid mitogenomes shared similar gene organization with 37 typical genes as well as a putative control region. Compared with other reported mitogenomes of mayflies, the unique gene order (I'-CR-Q-M) was found in these two mitogenomes. Although the observed rearrangement pattern is novel within ephemeropteran mitogenomes, it could be explained presumably by the mechanisms of tandem duplication-random loss and recombination. The phylogenetic analyses using both Bayesian inference (BI) and maximum likelihood (ML) methods based on four nucleotide datasets placed three ephemerellid species together. Furthermore, the phylogenetic relationships of the three genera were recovered as ((Ephemerella + Cincticostella) + Torleya).