Comparative Mitochondrial Genomics Studies In Ants Of The Genus Ostonia

Animal mitochondrial genomes are usually covalently closed circular double-stranded DNA molecules.They are normally compact,intron-free,relatively conserved in gene composition and structure,higher in evolutionary rate as compared to nuclear genomes,maternally inherited,and nearly free from genetic recombination.Hence,mitochondrial DNA has become an ideal tool for population genetics and evolutionary studies.However,it should be noted that there are exceptions to these characteristics.For example,mitochondrial gene rearrangement has been frequently in many animal taxa.Ants of the genus Stenamma(Formicidae:Myrmicinae)are natively distributed in most regions of the Northern Temperate Zone,Central America and northeastern South America.To date,no reports are publicly available about their mitogenomics.The present study represents a data mining of the previously published high-throughput sequencing data.In all,mitochondrial genomes of five Stenamma species(incl.S.diecki,S.expolitum,S.impar,S.megamanni&S.murall a)were assembled and annotated,and compared in depth.The major findings are summarized as follows:(1)All five mitochondrial genomes harbor the same panel of 37 typical animal mitochondrial genes and the noncoding control region.The light and heavy strands encodes 23 genes(9 protein-coding&14 tRNA genes)and 14 genes(4 protein-coding,8 tRNA and 2 rRNA genes),respectively.All mitochondrial genomes uses the typical ATN as the start codon,and most protein-coding genes adopt TAA as the stop codon with the few exceptional use of TAG and the incomplete codon T.A total of three unique mitochondrial gene arrangement patterns were revealed,and are different from all those previously uncovered in other formicid taxa.The five mitochondrial genomes differs markedly in size,ranging from 16,097(S.impar)to 18,695 bp(S.muralla),which is largely attributed to the obviously variable sizes of the noncoding regions.All mitochondrial genomes exhibit obvious A+T bias in base composition.(2)Bayesian phylogenetic analysis corroborates the subfamily-level taxonomic framework of the family Formicidae.The phylogenetic relationships among the six relevant subfamilies are uncovered as(((Myrmicinae+Formicinae)+Ponerinae)+Dolichoderinae)+(Dorylinae+Pseudomyrmicinae).The inter-relationships of the five Stenamma species is uncovered as((S.megamanni+S.muralla)+ S.expolitum)+(S.diecki+S.impar).(3)A total of 13 distinct gene arrangements were uncovered for 54 species from six subfamilies.In association with phylogenetic analysis,the primitive gene arrangement patterns were inferred for the whole family and for each subfamily as well.The present study appears to support that mitochondrial gene arrangements are phylogenetically meaningful at lower taxonomic scales within the family Formicidae,and that they have occurred multiple times independently in each subfamily.However,a larger sample size is necessary to confirm such inferences.