中国云南果蝇属暗果蝇种组的核型分化

观察了新近发现于我国云南的果蝇属暗果蝇种组(Drosophila obscura species group)种类D．luguensis、D．dianensis和D．limingi的有丝分裂中期核型，并将3个种的核型与各自的近缘种类进行了比较。D．luguensis具2n=12条染色体，包括3对中央着丝粒(V形)染色体、2对近端着丝粒(棒状)染色体以及1对微小(点状)染色体。其中X和Y染色体均为中央着丝粒染色体。D．dianensis和D．limingi具2n=10条染色体，包括1对大的V形常染色体，1对小的V形常染色体，2对J形(亚中着丝粒型)常染色体和1对点状染色体。其中X染色体为J形，Y染色体为短棒状。基于核型比较的结果以及D．sinobscura亚组地理分布的资料，结合种间系统发育关系研究结果，认为D．luguensis可能保留了该亚组祖先种类的核型。D．sinobscum的核型(2n=12：2V，1J，2R，1D)可能由一个pre-“sinobscura-hubeiensis”谱系的一个分支通过臂间倒位演化而来，而D．hubeiensis的核型(2n=10：4V，1D)可能由该谱系的另一分支通过着丝粒融合(2对近端着丝粒常染色体的融合)而形成。推测在D．dianensis和近缘欧洲种D．subsilvestris(2n=12：3V，2R，1D)间、D．limingi和东亚近缘种D．tsukubaensis(2n=12：3V，2R，1D)间的物种分化过程中，可能有相似的染色体变异类型发生。

Karyotype Differentiation in Newly Discovered Members of the Drosophila obscura Species Group from Yunnan,China

We examined mitotic chromosomes of three newly found members of the Drosophila obscura species group, D. luguensis, D. dianensis and D. limingi from Yunnan and compared their karyotypes to those of respective related species. D.luguensis possessed a diploid number of 12 chromosomes, comprising 3 pairs of metacentrics (Vshaped), 2 pairs of acrocentrics (rod-like) and 1 pair of micro-chromosomes (dot-like). Both the X and Y were metacentrics. D. dianensis and D. limingi possessed a diploid number of 10 chromosomes, comprising 1 pair of large Vshaped, 1 pair of moderate-sized V-shaped, 2 pairs of submetacentric (J-shaped) chromosomes, and 1 pairs of dot-like chromosomes, with their X chromosomes were J-shaped and Y chromosomes were short rod-like ones. Based upon the results of chromosomal comparisons, geographic information of the sinobscura subgroup, as well inter-specific phylogenetic relationship deduced elsewhere, D. luguensis was considered to retain an ancestral form of the karyotype within this subgroup. The present observations have also implied that D. sinobscura (2n = 12: 2V, 1J, 2R, 1D) might have derived from a sub-lineage of a pre- "sinobscura-hubeiensis" lineage by pericentric inversion of moderate-sized metacentric autosomes and D. hubeiensis (2n = 10: 4V, 1D) from another sub-lineage of the same lineage by centric fusion of 2 pairs of acrocentric autosomes. Similar chromosomal changes of centric fusion, centric fission and/or pericentric inversion might have occurred during the course of species divergences between D. dianensis and D.subsilvestris (2n = 12: 3V, 2R,1D), an European member closely related to D. dianensis, and between D. limingi and D. tsukubaensis (2n = 12: 3V,2R, 1D), an East Asian member near to D. limingi.