Wu C I, Hollocher H, Begun D J, Aquadro C F, Xu Y, Wu M L
Department of Ecology and Evolution, University of Chicago, IL 60637, USA.
Proc Natl Acad Sci U S A. 1995 Mar 28;92(7):2519-23. doi: 10.1073/pnas.92.7.2519.
It is generally believed that Drosophila melanogaster has no closely related species with which it can produce the viable and fertile hybrids that are essential for the genetic analysis of speciation. Following the recent report of molecular differentiation between a Zimbabwe, Africa, population and two United States populations, we provide evidence that strong sexual isolation exists between the D. melanogaster population in Zimbabwe and populations of other continents. In the presence of males of their own kind, females from most isofemale lines of Zimbabwe would not mate with males from elsewhere; the reciprocal mating is also significantly reduced, but to a lesser degree. The genes for sexual behaviors are apparently polymorphic in Zimbabwe and postmating reproductive isolation between this and other populations has not yet evolved. Whole chromosome substitutions indicate significant genetic contributions to male mating success by both major autosomes, whereas the X chromosome effect is too weak to measure. In addition, the relative mating success between hybrid and pure line males supports the interpretation of strong female choice. These observations suggest that we are seeing the early stages of speciation in this group and that it is driven by sexual selection. The genetic and molecular tractability of D. melanogaster offers great promise for the detailed analysis of this apparent case of incipient speciation.
人们普遍认为，黑腹果蝇没有与之能够产生对于物种形成遗传分析至关重要的可存活且可育杂种的近缘物种。继最近关于非洲津巴布韦种群与两个美国种群之间分子分化的报道之后，我们提供证据表明，津巴布韦的黑腹果蝇种群与其他大陆的种群之间存在强烈的性隔离。在有同种雄性存在的情况下，津巴布韦大多数同雌系的雌性不会与其他地方的雄性交配；反过来的交配也显著减少，但程度较轻。性行为相关基因在津巴布韦显然是多态的，并且它与其他种群之间的交配后生殖隔离尚未进化。全染色体替换表明，两条主要常染色体对雄性交配成功都有显著的遗传贡献，而X染色体的影响太弱以至于无法测量。此外，杂种雄性和纯系雄性之间的相对交配成功率支持了强烈雌性选择的解释。这些观察结果表明，我们正在目睹这一群体物种形成的早期阶段，并且它是由性选择驱动的。黑腹果蝇在遗传和分子方面的易处理性为详细分析这一明显的初始物种形成案例带来了很大希望。
