Karyotype diversification and conservation in herbivorous drosophilids (Diptera: Drosophilidae) from Japan and Taiwan

Abstract We analyzed metaphase chromosomes of 13 herbivorous drosophilid species representing six genera of the tribe Drosophilini , including the first chromosomal description for Styloptera . Chromosome numbers ranged from 2n = 6 in Liodrosophila aerea , the lowest yet reported in Drosophilidae, to 2n = 14 in Scaptomyza hexasticha , the highest known. The so‐called “standard karyotype” (2n = 8: 1R, 2V, 1D; X = R), long associated with Drosophila melanogaster , was also observed in five independent herbivorous genera: Dichaetophora , Liodrosophila , Microdrosophila , Scaptomyza , and Styloptera . All species exhibited an XX/XY sex chromosome system, with a telocentric X except in Lo. chaolipinga and Lo. porrecta , where it was metacentric. The number of major chromosome arms was conserved within two genera, 14 in Lordiphosa and 10 in Scaptomyza . These results suggest that, despite interspecific variation in chromosome number, fundamental chromosomal elements have been repeatedly conserved as a common karyotype framework across herbivorous drosophilids, implying the presence of evolutionary constraints acting on karyotype organization within Drosophilini.