Chromosomal variation of the leaf-mining Liodrosophila castanea (Diptera, Drosophilidae), with the results of crossing experiments (生物進化研究のモデル生物群としてのショウジョウバエ)

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Chromosomal variation was found in three insular populations of Liodrosophila castanea (Diptera, Drosophilidae). Both Yakushima and Okinawa strains possessed 2n＝12 chromosomes, 5 pairs of acrocentric autosomes and sex chromosomes, in the metaphase plates of larval brain cells. Of them a pair of middle-sized autosomes were heteropyknotic from the prophase to early metaphase during the cell division. Tsushima strain had 2n＝10 chromosomes, 4 pairs of acrocentric autosomes and sex chromosomes. All nuclear plates of Tsushima strain contained small supernumerary chromosomes ranging from 2 to 9 in number and lacked any heterochromatic autosome. Morphologically, any discriminative character was not found between different chromosomal strains, excepting the nearly bare cercus in Yakushima and Okinawa strains (pubescent in Tsushima's). Male flies mated well with different strain females in crossing experiments without any mating preference, and produced fertile F1 males and females in both directions of crosses. The present results demonstrate that these insular strains with different karyotypes should be regarded as chromosomal races of Liodrosophila castanea.生物進化研究のモデル生物群としてのショウジョウバエ. 北海道大学低温科学研究所編