Metaphase karyotypes of fruit flies of Thailand. IV. Evidence for six new species of the Bactrocera dorsalis complex

Abstract

Wild samples of larvae of 6 new fruit fly species belonging to the Bactrocera dorsalis complex have been temporarily designated as species I, J, K, L, M and N, based on cytological evidence. The flies are also morphologically distinguishable as adults. The larvae of these species seem to specifically infest fruits of different host plants. Cytological examination of larvae of these new species has revealed distinct patterns of metaphase karyotypes on the basis of different amounts and distribution of constitutive heterochromatin in sex chromosomes and autosomes. Thus the mitotic karyotype of species I is somewhat similar to that of B. dorsalis and is classified into Group 1. On the other hand, species L, M and N exhibit mitotic karyotypes of Group 4 showing specific patterns of heterochromatin in the centromeric regions of the X chromosome. Species J and K show a general feature of the mitotic karyotype of Group 3, which exhibits distinctive patterns of heterochromatin in sex chromosomes. These findings support the important role of constitutive heterochromatin in karyotypic evolution of these members of the B. dorsalis complex. Such a gross difference in heterochromatin is also a useful tool in cytotaxonomic study of closely related species of the fruit flies of Thailand.