Studies On The Comparative Mitochondrial Genomes And Phylogeny Of Some Subfamilies In Pteromalidae

Pteromalidae is an important group of parasitic wasps that can parasitize most insect orders and even spiders;meanwhile,they can parasitize all developmental stages including eggs,larvae,pupae and adults.They can be used for controlling pests in agriculture and forestry,playing an important role in maintaining ecological balance.The mitochondrial genomes follow the maternal inheritance,and in addition,they also have some other unique characteristics,such as relatively conservative gene arrangements,small size of genome and accerlated evolutionary rate.Therefore,it provides reliable molecular markers for phylogeny and evolution research.However,the mitochondrial genomes of only seven species of two subfamilies have been sequenced compared with the large number of species in Pteromalidae.Besides,the phylogenetic relationships within Pteromalidae were complicated and many of them remain unsolved.Therefore,it is of great significance to sequence and analyze mitochondrial genomes of more species in Pteromalidae,which will accerate exploreing the phylogenetic relationships within this family.The sequenced mitochondrial genomes of Pteromalidae extend to 34 species representing eight subfamilies,in which the mitochondrial genomes of 28 species in seven subfamilies of Pteromalidae were sequenced,annotated and analyzed in this study.Meanwhile,with the help of bioinformatics,we preliminarily analyzed the characteristics of the comparative mitochondrial genomes and the phylogenetic relationships of Pteromalidae.The main results are as follows:(1)The mitochondrial genomes of 28 species in seven subfamilies of Pteromalidae were sequenced and annotated,and their base composition,overlap and intergentic regions,gene rearrangements,evolutionary rate,and codon usages were analyzed.The sequenced lengths of mitochondrial genomes are 12,004–17,073 bp,with Asaphes suspensus and Chlorocytus murriensis ranking the longest and the shortest,respectively;A+T content ranges from 81.5% to 87.0%,of which the highest and the lowest A+T contents happen in Dipara sp.and Asaphes suspensus,respectively;all AT skews are positive,while GC skews are all negative,the highest AT skew occurs in Zolotarewskya longicostalia(0.1344)while the lowest AT skew in Pteromalus puparum(0.0201);the highest GC skew occurs in Dipara sp.(-0.001)while the lowest GC skew in Halticoptera crius(-0.2515).(2)There are short overlap and intergentic regions between genes in the mitochondrial genomes of Pteromalidae.Overlap frequently appears between ATP6-ATP8 and nad4-nad4 L,and the intergenic region is longer than the overlap region.Large-scale gene rearrangements often occur,among which the hot spots of tRNAs are mainly concentrated in tRNA clusters between nad2-nad3 and tRNA clusters between rrn S-nad2;as for gene rearrangement in protein-coding genes,the six protein-coding genes nad3-cox3-ATP6-ATP8-cox2-cox1 are all inverted.Ka/Ks of all species are greater than 1,indicating that the protein-coding genes of these species have been subjected to positive selection during the history of evolution.All protein-coding genes use ATN as a start codon,and most protein-coding genes stop with TAA,but a few protein-coding genes use incomplete TA,T or complete TAG as stop codons.The codon usages of mitochondrial protein coding genes are strongly biased,the average number of effective codons(ENC)is 40.424,and ENC is positively correlated with the third coding positions of GC contents.(3)The phylogenetic relationships among eight subfamilies of Pteromalidae was preliminarily analyzed based on the mitochondrial genome sequences.The phylogenetic trees constructed by different matrices and methods are slightly different,but all the results support that Pteromalinae is a polyphyletic group;the subfamilies Pteromalinae,Miscogastrinae and Diparinae are not monophyletic groups,and the subfamilies Miscogastrinae and Pteromalinae are closely related;the subfamily Diparinae is closely related to the subfamily Sycoryctinae and the family Eupelmidae;the subfamily Cleonyminae and Pireninae are sister group.Most results support that the subfamily Asaphinae and the family Trichogrammatidae,and the subfamily Ormocerinae and the family Eurytomidae are sister groups.(4)In our study,BI analyses yielded higher support values and more consistent topologies than ML analyses,and the results of heterogeneity comfirmed the topology reconstructed by PCG12 matrice using Bayesian analyses.