Study of the possibility of differentiating species of the Bactrocera tryoni complex based on regions of the mitochondrial genes COI and 16S

The Queensland fruit fly Bactrocera (Bactrocera) tryoni (Froggatt, 1897) is a member of the Tephritidae family and is a serious pest of a wide range of fruit and vegetable crops in Australia. The object of this study, Bactrocera tryoni, belongs to the complex of B. tryoni species, which, in addition to it, includes the species Bactrocera aquilonis (May, 1965), Bactrocera neohumeralis (Hardy, 1951), and Bactrocera melas (Perkins & May, 1949). Since these species are morphologically very similar and some may infect similar products, there is a need for molecular genetic diagnostic methods that will reliably distinguish these species from other species and among themselves. According to the obtained data on the COI gene generally in the sample matrix, there is a hiatus - a gap between intra- and interspecific distances. However, the species B. tryoni, B. aquilonis, and B. neohumeralis on the dendrogram form clades corresponding to the same species, therefore, it is impossible to distinguish them using the sequences of the COI gene region. However, based on this sequence, it is possible to narrow down the identification by molecular genetic methods to these three species, since they are well separated from other studied species. According to the graph of the distribution of pairwise genetic distances for the 16S gene, there is a lower variability than for the COI gene. On the dendrogram, the species B. tryoni, B. aquilonis, and B. neohumeralis form the one clade, but other species formed separate clades. It is necessary to increase the number of 16S gene sequences in the sample for each species. Thus, based on the COI gene sequence, it is possible to separate the species B. tryoni, B. aquilonis, and B. neohumeralis from other species of the genus Bactrocera studied by us. To study the relationships within the complex of B. tryoni species and search for a gene sequence by which it will be possible to reliably differentiate the B. tryoni species, another, possibly more rapidly evolving gene is required.

昆士兰果实蝇（Queensland fruit fly）*Bactrocera (Bactrocera) tryoni*（Froggatt, 1897）隶属于实蝇科（Tephritidae），是澳大利亚境内多种果蔬作物的重大害虫。本研究的靶标物种*Bactrocera tryoni*隶属于*B. tryoni*物种复合群，该复合群除本种外，还涵盖*Bactrocera aquilonis*（May, 1965）、*Bactrocera neohumeralis*（Hardy, 1951）以及*Bactrocera melas*（Perkins & May, 1949）三个物种。
由于上述物种形态特征极为相似，且部分类群可侵染相同寄主产品，因此亟需开发能够可靠区分该复合群物种与其他实蝇物种、且可在复合群内部实现物种分辨的分子遗传诊断方法。
基于样本中COI基因（COI gene）的现有测序数据，存在显著的遗传距离间隙——即种内与种间遗传距离之间存在明确分界。然而，在系统发育树（dendrogram）上，*B. tryoni*、*B. aquilonis*与*B. neohumeralis*各自形成对应物种的演化支（clade），因此无法仅通过COI基因区域序列对这三个物种进行区分。
但依托该基因序列，可将分子遗传鉴定的范围缩小至该三物种复合群，因为它们与本研究中其他已测序的实蝇属（Bactrocera）物种存在清晰的区分度。
通过16S基因（16S gene）的成对遗传距离分布图谱可见，其序列变异程度低于COI基因。在系统发育树中，*B. tryoni*、*B. aquilonis*与*B. neohumeralis*仍共同构成一个单一演化支，而其余研究物种则各自形成独立演化支。当前样本中各物种的16S基因序列数量有待进一步扩充。
综上，依托COI基因序列，可将*B. tryoni*、*B. aquilonis*与*B. neohumeralis*与本研究中其他已测序的实蝇属物种区分开来。若要解析*B. tryoni*物种复合群内部的演化关系，并寻找可可靠区分该复合群各物种的基因标记，则需要选取另一种进化速率可能更快的基因开展后续研究。