Identification of invasive species Frankliniella occidentalis and native species F. intonsa based on double gene markers.
Rapid and accurate species identification is crucial in natural enemy screening and management of pest insects by biological control. Two closely related thrips species, Frankliniella occidentalis (an invasive thrips species) and F. intonsa (a native thrips species), always occur simultaneously at the same district, during the same period or even on the same host plant. Since both thrips species are small in size and morphologically similar, it is very difficult to distinguish between the two of them rapidly. In the present study, the mitochondrial cytochrome c oxidase subunit I (COI) and internal transcribed spacer 2 (ITS2) genes were used to identify F. occidentalis and F. intonsa, collected from 10 different districts of seven provinces in China. The results based on COI and ITS2 genes indicated that the genetic distance between the two thrips species was 0.221 and 0.113, respectively, which were 22.1 and 18.8 times as high as the corresponding values within species, and no overlap was detected between inter-and intra-species genetic distances. The identification based on phylogenetic trees was consistent with those based on morphological characteristics for F. occidentalis and F. intonsa, indicating that both COI and ITS2 genes can be used to identify closely related species effectively. Moreover, when the COI gene sequence was analyzed, all the haplotypes from F. occidentalis assembled into two clades corresponding to glasshouse strain and lupin strain of this thrips. The results can benefit identification of closely related species accurately and rapidly, as well as screening and exploiting specialist natural enemies and evaluating their control efficacy.