Raskina Olga, Belyayev Alexander, Nevo Eviatar
Institute of Evolution, University of Haifa, Mt. Carmel, Haifa 31905, Israel.
Proc Natl Acad Sci U S A. 2004 Oct 12;101(41):14818-23. doi: 10.1073/pnas.0405817101. Epub 2004 Oct 4.
Data are presented on quantum speciation in the Sitopsis section of the genus Aegilops (Poaceae, Monocotyledones). Two small, peripheral, isolated, wild populations of annual cross-pollinated Ae. speltoides and annual self-pollinated Ae. sharonensis are located 30 m apart on different soil types. Despite the close proximity of the two species and their close relatedness, no mixed groups are known. Comparative molecular cytogenetic analysis based on the intrapopulation variability of rRNA-encoding DNA (rDNA) chromosomal patterns of individual Ae. speltoides geno-types revealed an ongoing dynamic process of permanent chromosomal rearrangements. Chromosomal mutations can arise de novo and can be eliminated. Analysis of the progeny of the investigated genotypes testifies that inheritance of de novo rDNA sites happens frequently. Heterologous recombination and/or transposable elements-mediated rDNA transfer seem to be the mechanisms for observed chromosomal repatterning. Consequently, several modified genomic forms, intermediate between Ae. speltoides and Ae. sharonensis, permanently arise in the studied wild population of Ae. speltoides, which make it possible to recognize Ae. sharonensis as a derivative species of Ae. speltoides, as well as to propose rapidness and canalization of quantum speciation in Sitopsis species.
本文展示了山羊草属（禾本科，单子叶植物纲）Sitopsis组的量子物种形成数据。一年生异花授粉的斯卑尔脱山羊草和一年生自花授粉的沙伦山羊草的两个小型、边缘、孤立的野生种群，位于不同土壤类型上，相距30米。尽管这两个物种距离很近且亲缘关系密切，但尚无混合群体的报道。基于单个斯卑尔脱山羊草基因型的rRNA编码DNA（rDNA）染色体模式的种群内变异性进行的比较分子细胞遗传学分析，揭示了一个正在进行的永久性染色体重排的动态过程。染色体重组可从头产生并可被消除。对所研究基因型后代的分析表明，从头rDNA位点的遗传很常见。异源重组和/或转座元件介导的rDNA转移似乎是观察到的染色体重新模式化的机制。因此，在斯卑尔脱山羊草的研究野生种群中，经常出现几种介于斯卑尔脱山羊草和沙伦山羊草之间的改良基因组形式，这使得将沙伦山羊草视为斯卑尔脱山羊草的衍生物种成为可能，同时也提出了Sitopsis物种量子物种形成的快速性和定向化。
