Analysis Of Whole Mitochondrial Genome And Geographic Population Variation In Andricus Mairei

Mitochondrial genomes have been widely used in comparative and evolutionary genomics,molecular evolution,phylogeny,and population genetics.However,there is very limited information on the mitochondrial genome of Cynipidae,with only one known species,Synergus sp.,Trichagalma acutissimae and Dryocusmus liui.In this paper,we sequenced the whole mitochondrial genome of five different geographical populations of this species with walking-primer method,described the basic characteristics and variation of different geographical populations,and analyzed the gene rearrangement and phylogeny of the genome.The main results are as follows:(1)The A.mairei mitochondrial genome length is 16,504-16,578bp,containing the typical 37 genes.13 PCGs,2 rRNA,2 CRs,22 tRNA.Except trnS1,21 tRNA genes fold into clover-shaped secondary structures.Two control regions(CRs)were detected in all five geographical populations,with a inverted repeat in the two CRs.(2)According to the genetic distance map of coxl and cytb,the genetic distance between the cox1 gene of A.mairei ILV89 and other gall wasps other than A.mairei SC is 0.0015-0.0168(<0.2),However,the genetic distance in the cytb gene was from 0.0647 to 0.0787,The genetic distance between coxl and cytb is very large;The genetic distance of the cox1 gene of A.mairei ILV91 from A.mairei SC was 0.0018,The two are very closely related;however,the genetic distance at cytb is 0.0719.Two subregions,AT-rich and non-tandem repeats,were found in the CR region of the GD,QY,SG,and ZN populations,whereas only AT-rich was found in the SC population.Sliding window and genetic distance analysis of SC and GD showed low nucleotide diversity in 13 protein-coding genes and 2 rRNA,relatively low evolutionary rates of cox1,nadl and nad4,and high variability of nad3,cox3 and cytb.(3)In a comparison with the putative ancestral mitogenome,gene rearrangements were found in transfer RNA(tRNA)genes,protein-coding genes and ribosomal RNA(rRNA)genes.Consistent with other Cynipidae species,the gene rearrangement of A.mairei had four obvious characteristics:trnE and trnF had inverted and swapped positions;rrnL and rrnS genes had moved into the cob-nad1 junction;a novel tRNA gene cluster trnL1-trn1-trnL2-trnW-trnM-trnQ had been formed between nadl and nad2;and trnV had inverted and moved to the nad2-cox1 gene junction.Furthermore,A.mairei had two types of mitochondrial circular DNA molecules.type-Ⅱ differed from type-Ⅰ in an inverted rearrangement of a large fragment,including two CRs and two rRNA genes.(4)Combining BI and ML trees constructed from different matrices of cox1,CRs,PCG123+2rRNA and PCG12+2rRNA,we identified the SC population as new species related to A.mairei.In the phylogenetic analysis of A.mairei,we assessed the influence of inclusion/exclusion of third codon positions.The results showed that the topologies were stable whereas node support varies with datasets.