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（Bactrocera (Bactrocera) tryoni, Froggatt, 1897）隶属于实蝇科（Tephritidae），是澳大利亚境内危害多种果蔬作物的重大农业害虫。
本研究的目标物种为昆士兰果实蝇，其隶属于果实蝇属（Bactrocera）的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。鉴于这些物种形态极为相似，且部分类群可侵染相同寄主作物，因此亟需开发能够可靠区分该类群物种及其与其他实蝇物种的分子遗传学诊断方法。
基于样本矩阵中COI基因的现有测序数据，存在一个显著的遗传间隙——即种内与种间遗传距离之间存在明确间隔。然而在系统发育树（dendrogram）上，B. tryoni、B. aquilonis与B. neohumeralis聚为对应各自物种的进化支（clade），因此无法通过COI基因区域序列对这三者进行区分。不过依托该序列，可将分子遗传鉴定的范围缩小至这三个物种，因为它们与其他已研究的果实蝇属物种可清晰区分开。
基于16S基因的两两遗传距离分布图谱，其序列变异程度低于COI基因。在系统发育树上，B. tryoni、B. aquilonis与B. neohumeralis共同构成一个进化支，而其余物种则各自形成独立的进化支。后续需增加各物种的16S基因序列样本量，以优化分析结果。
综上，基于COI基因序列，可将B. tryoni、B. aquilonis与B. neohumeralis与本研究已分析的其他果实蝇属物种区分开来。若要深入研究B. tryoni物种复合群内部的系统发育关系，并筛选出可可靠区分该复合群各物种的基因序列，则需要选取另一个进化速率可能更快的基因作为分子标记。