Morphological Characters and PCR-RFLP Markers in the Interspecific Hybrids between Bactrocera carambolae and B. papayae of the B. dorsalis Species Complex (Diptera: Tephritidae)

摘要

Morphological characters and PCR-RFLP markers of interspecific hybrids between Bactrocera carambolae and B. papayae (Diptera: Tephritidae) were investigated. Both species are economically important pests that belong to the Bactrocera dorsalis speciescomplex. They have never been found in Japan. For the present study, test insects were imported into Japan from Malaysia and Thailand, and they were maintained in the laboratory, with permission from the relevant authority. A pair of flies, B. carambolaefemale and B. papayae male, were crossed. The aculeus lengths of the F_1 and F_2 hybrids were found to be intermediate between those of the two parental species. In addition, the range of morphological variation was expanded in the F_2 hybrids. Therefore, aculeus length in these two species is considered to be determined by quantitative inheritance. In all F_1 hybrids, the restriction pattern of the PCR-RFLP fragments of mitochondrial DNA (mtDNA; 16S rRNA) was the same as that of the maternal species,and that for nuclear ribosomal DNA (rDNA; 5.8 S rRNA and ITS) contained the restriction fragments of both P_1 species in a heterozygous banding pattern (hybrid pattern). The frequency ratio in F_2 females of the B. carambolae pattern, the B. papayae pattern and the hybrid restriction pattern was 14 : 1 : 27. There was no correlation between the morphological characters and the rDNA markers in the F_2 hybrids. It is therefore suggested that in both species, the inconsistency between the morphological characters and the DNA markers, and the continuous variation of the aculeus length, were mainly caused by interspecific hybridization in the distribution area.