The six whole mitochondrial genomes for the species: features, evolution and phylogeny.

In this study, the complete mitogenomes of three species ( ZM79-3, ZM33-4 and sp. ZM41-5) were sequenced, assembled and compared with the other three previously sequenced mitogenomes ( VNIIKR SE Dcaul3, MSPL 10-6 and VNIIKR SE Dps12). The six mitogenomes were found to be circular DNA molecules, with lengths ranging from 53,646 bp to 108,865 bp. The mitogenomes of the six species mainly comprised the same set of 15 core protein-coding genes (PCGs), two rRNAs, and a certain number of tRNAs and unidentified open reading frames (ORFs). The PCG length, AT skew and GC skew showed large variability among the 15 PCGs in the six mitogenomes. The gene had the least K2P genetic distance of the 15 core PCGs among the 13 species, indicating that this gene was highly conserved. The Ka/Ks values for all 15 core PCGs were < 1, suggesting that these genes were all subject to purifying selection. Comparative mitogenome analysis showed that introns contributed the most to the size variation of mitogenomes. Frequent intron loss/gain events were detected to have occurred in the gene during the evolution of the mitogenomes. Although the mitogenomes of 13 species from had undergone large-scale gene rearrangements, six mitogenomes of species had identical gene arrangements. Phylogenetic analysis based on combined mitochondrial gene datasets showed that the six species formed well-supported topologies. To our knowledge, this study is the first report on the mitogenomes of ZM33-4 and sp. ZM41-5, as well as the first comparison of mitogenomes among species. Our findings will further promote investigations of the genetics, evolution and phylogeny of the species.