Institute of Botany, Slovak Academy of Sciences, Dúbravská cesta 9, SK-845 23 Bratislava, Slovak Republic.
Ann Bot. 2010 Feb;105(2):249-64. doi: 10.1093/aob/mcp282. Epub 2009 Dec 10.
Intraspecific ploidy-level variation is an important aspect of a species' genetic make-up, which may lend insight into its evolutionary history and future potential. The present study explores this phenomenon in a group of eastern Asian Cardamine species.
Plant material was sampled from 59 localities in Japan and Korea, which were used in karyological (chromosome counting) and flow cytometric analyses. The absolute nuclear DNA content (in pg) was measured using propidium iodide and the relative nuclear DNA content (in arbitrary units) was measured using 4,6-diamidino-2-phenylindole fluorochrome.
Substantial cytotype diversity was found, with strikingly different distribution patterns between the species. Two cytotypes were found in C. torrentis sensu lato (4x and 8x, in C. valida and C. torrentis sensu stricto, respectively), which displays a north-south geographical pattern in Japan. Hypotheses regarding their origin and colonization history in the Japanese archipelago are discussed. In Korean C. amaraeiformis, only tetraploids were found, and these populations may in fact belong to C. valida. C. yezoensis was found to harbour as many as six cytotypes in Japan, ranging from hexa- to dodecaploids. Ploidy levels do not show any obvious geographical pattern; populations with mixed ploidy levels, containing two to four cytotypes, are frequently observed throughout the range. C. schinziana, an endemic of Hokkaido, has hexa- and octoploid populations. Previous chromosome records are also revised, showing that they are largely based on misidentified material or misinterpreted names.
Sampling of multiple populations and utilization of the efficient flow cytometric approach allowed the detection of large-scale variation in ploidy levels and genome size variation attributable to aneuploidy. These data will be essential in further phylogenetic and evolutionary studies.
种内倍性水平的变化是物种遗传组成的一个重要方面，它可能为物种的进化历史和未来潜力提供深入的了解。本研究探讨了东亚碎米荠属物种中的这一现象。
从日本和韩国的 59 个地点采集植物材料，用于染色体（染色体计数）和流式细胞分析。使用碘化丙啶测量绝对核 DNA 含量（pg），并使用 4,6-二脒基-2-苯基吲哚荧光染料测量相对核 DNA 含量（任意单位）。
发现了大量的细胞型多样性，物种之间的分布模式明显不同。在广义的碎米荠（C. torrentis sensu lato）中发现了两种细胞型（4x 和 8x，分别在 C. valida 和 C. torrentis sensu stricto 中），它们在日本呈南北地理分布模式。讨论了它们在日本群岛的起源和殖民历史的假说。在韩国的 C. amaraeiformis 中，只发现了四倍体，这些种群实际上可能属于 C. valida。在日本，C. yezoensis 发现了多达六种细胞型，从六倍体到十二倍体不等。倍性水平没有明显的地理模式；在整个范围内经常观察到含有两种到四种细胞型的混合倍性水平的种群。北海道特有种 C. schinziana 具有六倍体和八倍体种群。对以前的染色体记录也进行了修订，表明它们主要基于错误识别的材料或错误解释的名称。
对多个种群的采样和利用高效的流式细胞分析方法，检测到了大规模的倍性水平和由非整倍体引起的基因组大小变异。这些数据将是进一步进行系统发育和进化研究的基础。
