Molecular evolution of tephritid fruit flies in the genus Bactrocera based on the cytochrome oxidase I gene

Fruit flies of the genus Bactrocera (Diptera: Tephritidae) are one of the major economically important insects in Asia and Australia. Little attention has been given to analyses of molecular phylogenetic relationships among Bactrocera subgenera. By using mitochondrial cytochrome oxidase I gene (COI) sequences, the phylogenetic relationships among four subgenera, Asiadacus, Bactrocera, Hemigymnodacus, and Zeugodacus, were investigated. Nucleotide diversity within subgenera ranged from 11.7 to 12.4%, and the net divergence among subgenera ranged from 11.2 to 15.7%. Phylogenetic trees calculated from both maximum parsimony and neighbor-joining phylogenetic analysis methods were highly congruent in terms of tree topologies. Phylogenetic analysis of mitochondrial COI sequences suggests that tephritid fruit fly species, which attack cucurbit plants, that is, Asiadacus, Hemigymnodacus and Zeugodacus, were more closely related to each other than to fruit fly species of the subgenus Bactrocera, which attack plants of numerous families. Our data supports previous classification of Bactrocera based on morphological characters. However, the phylogenetic tree showed the polyphyletic of fruit flies in subgenus Zeugodacus. Possible causes of speciation among fruit flies species in this genus were also discussed.