镞果实蝇亚属6种实蝇形态与线粒体基因组及系统发育分析OA

[Objective]Morphological characteristics,complete mitochondrial genomes,and phylogenetic relationships of 6 important species in the subgenera of Bactrocera and Zeugodacus were studied.[Methods]A phylogenetic tree was constructed using the maximum likelihood(ML)method with an approach that compared 6 species in the subgenus of fruit flies using the combination of morphological description,characteristic images,and complete mitochondrial genome determined based on high-throughput sequencing.DNA MAN was employed along with formulas AT skew=(A－T)/(A+T)and GC skew=(G－C)/(G+C)to calculate the base content and skew rate of the complete mitochondrial genome.[Results]The major differential morphology on the head,thorax,and abdomen of the 6 species included the following.(A)Having two black transverse bands on B.cilifer,one broad band on B.maculaus,and two facial spots on the other 4 species on the head.(B)The costal band of B.cucurbitae and B.synnephes extended beyond vein R2+3 but not to R4+5,which expanded at the wing apex with a brown band on the dm-cu crossvein on the thorax.By contrast,the costal band of B.maculaus was narrow that extended slightly beyond R2+3 and remained nearly uniform in width throughout.For B.cilifer,B.scutellaris,and B.yoshimotoi,the costal band was narrow and terminated at R2+3.And(C)B.cilifer had an entirely black abdomen,whereas the other 5 species had a yellowish-brown abdomen with black maculae.The length of mitochondrial genome of the 6 species ranged from 15 835 to 15 919 base pairs(bp)that contained 37 typical mitochondrial genes that included 13 protein-coding genes(PCGs),22 transfer RNA(tRNA)genes,2 ribosomal RNA(rRNA)genes,and 1 non-coding control region.The nucleotides in the mitochondrial genomes were adenine(A),cytosine(C),guanine(G),and thymine(T)in the contents of 38.3%~39.7%,15.9%~16.5%,9.8%~10.5%,and 34.3%~34.8%,respectively.The combined A+T content reached 72.9%~74.0%,indicating a significant AT bias.The positive AT skew ranged 0.051~0.074,while the negative GC skew ranged from －0.252 to －0.210.The nucleotide contents in the entire genome were consistently A>T>C>G.The codon usage analysis showed that leucine(L)was the highest usage frequency(N)amino acid.The N value ranged 600~611,the relative synonymous codon usage(RSCU)value ranged 15.98~16.69,and L accounted for 33.1%~39.66%of the total amino acid.A phylogenetic analysis based on the mitochondrial genome data indicated that all 6 species were stably clustered within the Zeugodacus subgenus clade,which clarified the taxonomic affiliation within the subgenus and the phylogenetic relationships with closely related species.[Conclusion]Major morphological characteristics of the 6 fruit fly species were examined with the genes determined and the sequences deposited in GenBank,and the basic structure of the complete mitochondrial genome unveiled.Additionally,the taxonomy and phylogenetic relationships of the 6 species were clarified to provide a basis for species identification,molecular marker development,and phylogenetic research on fruit flies.