Institut Botànic de Barcelona (IBB-CSIC-ICUB), Passeig del Migdia s.n., Parc de Montjuïc, 08038 Barcelona, Catalonia, Spain.
Genome. 2012 Jul;55(7):529-35. doi: 10.1139/g2012-041. Epub 2012 Jul 13.
Island radiation constitutes a playground for species diversification, which has long fascinated researchers and still does today. Because only a small subset of taxa within the pool of island colonizers is concerned by this process, the question is raised on whether some factors could make a taxon prone to radiate. Cheirolophus is the only genus of Centaureinae subtribe to have experienced a radiation in the Canary Islands. Cytogenetic characterization through FISH of 5S and 35S ribosomal RNA genes in eight Cheirolophus species from continent and Canary Islands revealed an unusually high number of 35S predominantly at terminal position, together with a single interstitial 5S rDNA locus in all the studied taxa. Such an abundance of 35S rDNA signals is unique among Centaureinae and predates Cheirolophus arrival in Canary Islands. The possible link of the rDNA profile with radiation process is discussed through a comparison with two other case studies, the closely related Rhaponticum group and the genus Centaurea.
岛屿辐射构成了物种多样化的游乐场，长期以来一直吸引着研究人员的兴趣，直到今天依然如此。由于只有一小部分在岛屿殖民者群体中的分类单元受到这个过程的影响，因此就产生了这样一个问题，即是否存在某些因素会使一个分类单元更容易辐射。在加那利群岛，Cheirolophus 是唯一经历辐射的 Centaureinae 亚科属。通过 FISH 在来自大陆和加那利群岛的 8 种 Cheirolophus 物种中对 5S 和 35S 核糖体 RNA 基因进行细胞遗传学表征，发现 35S 基因在末端位置的数量异常高，而所有研究的分类单元都只有一个单一的 5S rDNA 基因座。在 Centaureinae 中，这种丰富的 35S rDNA 信号是独一无二的，而且早于 Cheirolophus 到达加那利群岛。通过与另外两个案例研究（密切相关的 Rhaponticum 组和 Centaurea 属）进行比较，讨论了 rDNA 图谱与辐射过程之间的可能联系。
