ON THE ORIGIN OF INCIPIENT REPRODUCTIVE ISOLATION - THE CASE OF DROSOPHILA-ALBOMICANS AND D-NASUTA
ON THE ORIGIN OF INCIPIENT REPRODUCTIVE ISOLATION - THE CASE OF DROSOPHILA-ALBOMICANS AND D-NASUTA
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DOI：
10.1111/j.1558-5646.1989.tb02612.x
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发表时间：
1989-12-01
期刊：
影响因子：
3.3
通讯作者：
AYALA, FJ
中科院分区：
文献类型：
--
作者：
CHANG, HY;AYALA, FJ
果蝇的nasuta亚组由12个已知的物种组成，被归类为移民组。D. nasuta和D. albomicans是广泛分布于印度-太平洋热带地区的两个姊妹种，尽管在形态上难以区分，但它们具有不同的中期染色体构型：D. Albomicans，因此大约60%的基因是性连锁的。我们的实验表明，至少在实验室里，这两个物种之间不存在性隔离、机械隔离或配子隔离。然而，杂种的“崩溃”表现在三个方面：1）每个培养物产生的F2杂种数量减少; 2）F2（雄性）和F3（雄性和雌性）杂种后代的育性降低; 3）某些地区品系之间杂交后代的性别比例异常。在实验种群中，这两个物种的核型仍然存在于20代后的相当大的频率，虽然这两种核型的频率取决于菌株的地理来源。我们的研究结果支持这一假设，在异地，后合子隔离的进化先于前合子隔离。线粒体DNA在两种D. nasuta和D.阿尔伯马人和他们之间相当相似。假设线粒体DNA进化的速度是典型的，这两个物种在大约50万年前就已经彼此分离了，而非洲和印度的D. nasuta（被一些作者认为是不同的亚种）可能在大约35万年前已经分化。
The nasuta subgroup of Drosophila consists of 12 known species classified within the immigrans group. D. nasuta and D. albomicans are two sibling species widely distributed throughout the Indo-Pacific tropics, which, although morphologically indistinguishable, have different metaphase-chromosome configurations: chromosomes X and 3 are attached in D. albomicans, so that about 60% of its genes are sex-linked. Our experiments show that, at least in the laboratory, there is no sexual, mechanical, or gametic isolation between the two species. There is, however, hybrid "breakdown" expressed in three ways: 1) reduction in the number of F2 hybrids produced per culture; 2) reduction in the fertility of F2 (males) and F3 (males and females) hybrid progenies; and 3) abnormal sex ratios in the progenies of crosses between strains of certain localities. In experimental populations, the karyotypes of both species are sill present in substantial frequencies after 20 generations, although the frequencies of the two karyotypes vary depending on the geographic origin of the strains. Our results support the hypothesis that, in allopatry, the evolution of postzygotic isolation precedes that of prezygotic isolation. The mtDNA is polymorphic in both D. nasuta and D. albomicans and fairly similar between them. Assuming typical rates of mtDNA evolution, the two species would have diverged from each other about 500,000 years ago, whereas the African and Indian populations of D. nasuta (considered to be different subspecies by some authors) might have diverged some 350,000 years ago.