[Review of mtDNA in molecular evolution studies]

Evolution of the Neopsylla hongyangensis Mitogenome: Insights Into the Mitogenomic Evolution of the Orders Siphonaptera and the Phthiraptera

The evidence that parasitic animals exhibit elevated mitogenomic evolution rates is inconsistent and limited to Arthropoda. Neopsylla hongyangensis Li, Bai et Chen, 1986 (Siphonaptera: Ctenophthalmidae) feeds on the host's blood and is an important medical insect with plague transmission. In this study, we sequenced the N. hongyangensis mitogenome and explored the mitogenomic evolution of Siphonaptera and Phthiraptera, which both belong to the Insecta on warm-blooded animals. The mitogenomes of Siphonaptera are closed-circular double-stranded DNA molecules and exhibit highly conserved structural features. In contrast, the mitogenomes of most Phthiraptera species exhibit extensive fragmentation and comprise multiple minichromosomes. We performed a comparative analysis of nucleotide composition, Ka/Ks ratios, and codon usage patterns in Siphonaptera and Phthiraptera mitogenomes. Compared to Phthiraptera with low locomotory capacity, Siphonaptera with high locomotory capacity have higher AT content, slower evolution, and greater influence from natural selection (i.e., micro-habitat). The mitogenomic evolution of Siphonaptera and Phthiraptera was influenced by locomotory capacity and life history. Phylogenetic analysis based on 13 PCGs showed that Ceratophyllidae, Leptopsyllidae, and Ctenophthalmidae were paraphyletic, and Vermipsyllidae, Hystrichopsyllidae, Pulicidae, and Pygiopsyllidae were monophyletic. This study provides new insights into the phylogenetic relationships and mitogenomic evolution of Siphonaptera.

The complete mitochondrial genome of Trabala vishnou guttata (Lepidoptera: Lasiocampidae) and the related phylogenetic analyses

The bluish yellow lappet moth, Trabala vishnou guttata is an extraordinarily important pest in China. The complete mitochondrial genome is sequenced and determined firstly, which is based on traditional PCR amplification and primer walking methods with a length of 15,281 bp, including 13 protein-coding (PCG) genes, 22 transfer RNA (rRNA) genes, two ribosomal RNA (tRNA) genes, and an A + T-rich region. The gene order and orientation of the T. vishnou guttata mitogenome were identical to the other sequenced Lasiocampidae species. The overall nucleotide composition of T. vishnou guttata is A (40.27 %), T (40.59 %), C (11.58 %) and G (7.56 %), respectively. All the PCGs initiate with the three orthodox start codons ATN except for coxI with CGA start codon. Three PCGs (coxI, coxII and nad4) used incomplete stop codon T, while the other 10 PCGs terminate with complete stop codon TAA. All tRNA genes have a typical clover-leaf structure except for the absence of a dihydrouridine arm in trnS (AGN). The length of A + T-rich region is 383 bp. Phylogeny is established to reveal the genetic relationship between T. vishnou guttata and other lepidopteran species based on 13 PCGs nucleotide sequences of the sequenced species (32 taxa) by Maximum likelihood and Bayesian methods. Phylogenetic analyses presents that T. vishnou guttata and its closely related species (Dendrolimus taxa) are clustered on Lasiocampidae group. It is a sister clade relationship between Lasiocampidae and other families in Bombycoidea with a bootstrap value of 83 % and a posterior probability of 0.75. This study supports that Lasiocampidae may be independent from Bombycoidea.