Studies On The Comparative Mitochondrial Genomics And Phylogeny Of Staphylinidae

The family Staphylinidae,belonging to Coleoptera,contains over 61,000 described extant species distributed worldwide,which is one of the families with most abundant species on earth.At present,The studies of Staphylidae mainly focused on the systematic and phylogenetic studies based on morphological features,nuclear genes and partial mitochondrial genes.In recent years,mitochondrial genome is one of the most popular markers,widely used in the entomological molecular systematics studies,due to its characteristic properties,relatively simple geneome structure,high mutation rate,maternal inheritance.This study reconstructed the phylogenetic analysis of Staphylinidae based on mitochondrial genome data to provide scientific data about the phylogenetic relationship of Staphylinidae and verify the phylogenetic relationship based on morphological characteristics and other molecular data.This study determined nine nearly complete mitochondrial genomes of Staphylinidae by NGS(next-generation sequencing),including seven Staphylininae insects,one Osoriinae insect(first determined)and one Paederinae insect.This study analyzed the characteristics and evolution of the mitochondrial genomes of Staphylinidae using comparative genomic and bioinformatics methods based on nine determined mitochondrial genomes and 90 mitochondrial genomes of Staphylinidae in Gen Bank,and reconstructed a high level phylogeny analysis of Staphylinidae utilizing Maximum Likelihood method and Mr Bayes inference based onmitochondrial genomes sequences.Main conclusions were drawn as follows:(1)At present,the mitochondrial genomes of Staphylinidae have no gene rearrangement and gene deletion except incompletely sequencing.(2)Most of the mitochondrial genomes of Staphylinidae present obvious AT-skew and CG-skew.(3)Gene overlap is associated with specific genes.There exist stable overlapping regions Among the mitochondrial genomes of Staphylinidae,the region of atp8-atp6,the region of nad4-nad4 L,overlapped by 7 bases(ATGATAG/ATGATAA),respectively.(4)Intergenic spacer sequences of the mitochondrial genomes of Staphylinidae mainly distributed in the region of tRNA-Arg-tRNA-Asn and the region of tRNA-Ser2-nad1.The lengths of the region of tRNA-Arg-tRNA-Asn are 50~228 bp.The intergenic spacer sequences of tRNA-Ser2-nad1 are about 20 bp,which is considered to be the signal site for transcription termination during the transcription of the mitochondrial genome.(5)Cox1 and nad1 start with special initiation codon AAT,TTG,respectively.nad4,nad5,cox2 and cox3 use T as incomplete stop codon.(6)Codon usage bias had a significant negative correlation with GC content of genes and more significant negative correlation with GC content of the third position of codon,(7)tRNA-Ser1 can't form a stable stem-loop structure but a simple loop due to lack the dihydrouracil arm(DHU arm).In addition,the anticodon for tRNA-Ser1 is UCU rather than usual GCU.(8)The evolutionary rate of atp8 was fastest,but cox1 was most conservative.Nucleotide substitution rate of protein-coding genes existed a significant negative correlation with GC content of genes.(9)Phylogeny analyses based on amino acid sequences and the sequence of first and second codons had certain differences,but all analyses don't support monophyletic groups of four staphylinid groups: Omaliine Group,Tachyporine Group,Oxyteline Group,Staphylinine Group.Steninae,Oxytelinae and Scaphidiinae were recovered as monophyletic.but Omaliinae and Tachyporinae were nonmonophyletic.The phylogenetic analyses validated previous study results based on morphological features.The phylogenetic relationship based on the nucleotide sequence of 37 genes also support the monophylies of Staphylininae and Aleocharinae,which is consistent with previous studies.The possible reason for the difference of the phylogenetic analysis based on amino acid sequence is that the amino acid sequence is too conservative and has no enough systematic information to solve the systematic relationship among the recently divided species.The possible reason for the difference of the phylogenetic analysis based on the sequence of first and second codons is that third codon site also contains the systematic informationl,so should not be deleted.(10)Paederinae and Habrocerinae gathered for a clade,which constitute a sister group with Staphylininae.Therefore,this denied the sister group relationship both Paederinae and Staphylininae.In addition,Pselaphinae is paraphyly in this study,which is different from some researchs that support Pselaphinae as monophyly.These results need to be explored by phylogenetic analysis based on more samples and molecular marker data.