Mitochondrial Genome And Phylogenetic Evolution Analysis Of Two Species Of The Genus Lipotactes

The subfamily Lipotactinae Ingrisch,1995 belongs to Insecta,Orthoptera,Ensifera,Tettigoniidea.The species of this subfamily are active carnivorous insects that are only distributed in Southeast Asia and southern China.Lipotactinae was recorded 2 genera and 31 species in the world,only 1 genus?Lipotactes Brunner von Wattenwyl,1898?and 6 species were reported in China.The mitochondrial genomes of insect have abundant genetic information,rapid rate of evolution,and stable structural.It is widely used in the study of phylogeny.The molecular clock is based on the linear rate of gene replacement,corrects the possible evolutionary speed of the genes through information,and then extrapolates the time of species differentiation.This study was based on L-PCR and Sub-PCR amplification strategies,obtained the complete mitochondrial genome sequences of Lipotactes vietnamicus Gorochov,1993 and Lipotactes truncatus Shi&Li,2009,analyzed the genomic arrangement,basic constitution and codon usage of the two mtDNA of Lipotactinae and compared with the whole mitochondrial genome sequence of Lipotactes tripyrga Chang,Shi&Ran,2005 that reported in NCBI.Finally,combining with the whole sequences of 71Ensifera mitochondrial genomes known in the NCBI and the whole mitochondrial genomes sequence of Prophalangopsis obscura?Walker,1869?obtained from this study,the BI and ML trees were constructed with different datasets?dataset PCG:13PCGs,dataset PCG+R:13PCGs+2rRNA?to construct phylogenetic relationships of Ensifera,and after calibrating with 5 fossil records,the molecular clock was constructed,in order to infer the differentiation time of the high order of the Ensifera.The conclusions were as follows:1.Two whole mitochondrial genome sequences were obtained in this study:Lipotactes truncatus and Lipotactes vietnamicus.The results of the annotation indicated that the genes encoded in the two mitochondrial genomes were identical to the typical insect mitochondria,but had the same rearrangement as the Lipotactes tripyrga:trnR-trnS^AGN-trnA-trnN-trnG-nad3.This may be a homologous sign in this subfamily.2.The whole mitochondrial genomes of Lipotactes truncatus and Lipotactes vietnamicus were compact and had a few number of overlaps and intergenic regions.The intergenic regions of Lipotactes vietnamicus were 325bp,longer than Lipotactes truncatus.The maximum overlap region of Lipotactes truncatus was 13bp,between nad3 and trnE and the maximum intergenic region was 36bp,between trnS^AGNGN and trnA.The maximum overlap region of Lipotactes vietnamicus was 7bp,between atp8and atp6 or nad4 and nad4L,and the maximum intergenic region was 81bp,between nad3 and trnE.3.Initiation codon of PCGs in Lipotactes truncatus and Lipotactes vietnamicus mitogenomes were typical ATN codon,except cox1 was CAA.11 complete TAA and2 incomplete single T were as stop codon in Lipotactes truncatus and Lipotactes vietnamicus.4.Among Lipotactes truncatus and Lipotactes vietnamicus mitogenomes,the most frequent codon of PCGs were all comprise with A and T,and Leu?Ile?Phe?Met and Gly were used as most frequently amino acids and the least was Cys.5.The mitochondrial genomes of Lipotactes truncatus,Lipotactes vietnamicus and Lipotactes tripyrga mitogenomes were all AT-biased,from 71.97%to 72.17%.In the analysis of genetic distances,the closest relationship was between Lipotactes truncatus and Lipotactes tripyrga,and the farthest relationship was between Lipotactes truncatus and Lipotactes vietnamicus.Ka and Ks analysis showed that in13 PCGs,the Ka/Ks values were significantly different,but the Ka/Ks values of the same gene among the three species was not significantly different,except atp8.Among them,the Ka/Ks values of atp8 and nad6 were slightly large,while the Ka/Ks values of cox1,cox2,cox3,nad1,and cytb were nearly small.6.In the phylogenetic trees,the topological structure of the ML tree and the BI tree constructed by dataset PCG were quite different,and the support rate of some base nodes were very low.The topology structure of ML tree and BI tree constructed by dataset PCG+R were basically the same,and the monophyletic of the superfamilies were supported,except Schizodactyloidea.In all phylogenetic trees,Lipotactinae was belonging to Tettigoniidae,and in the BI tree,it had the closest relationship with the Bradyporinae,while in the ML tree,it had the closest relationship with the Conocephalinae.However,only in the ML tree constructed by dataset PCG+R,the differentiation node of this subfamily obtained a high node support rate?94.1%?.7.According to the molecular clock,the conclutions were as follows:the differentiation of the superfamilies generally occurred in the Triassic period;the differentiation of the Tettigoniidae and Phaneropteridae occurred in the middle Jurassic period.The differentiation of the Lipotactinae and others occurred in the late Cretaceous period.