Department of Biosphere-Geosphere Science, Faculty of Biosphere-Geosphere Science, Okayama University of Science, Ridai-cho 1-1, Kita-ku, Okayama-shi, Okayama, 700-0005, Japan,
J Plant Res. 2014;127(1):99-107. doi: 10.1007/s10265-013-0578-y. Epub 2013 Jul 16.
Carex (Cyperaceae) is one of the largest genera of the flowering plants, and comprises more than 2,000 species. In Carex, section Siderostictae with broader leaves distributed in East Asia is thought to be an ancestral group. We aimed to clarify the phylogenetic relationships and chromosomal variations within the section Siderostictae, and to examine the relationship of broad-leaved species of the sections Hemiscaposae and Surculosae from East Asia, inferred from DNA sequences and cytological data. Our results indicate that a monophyletic Siderostictae clade, including the sections Hemiscaposae, Siderostictae and Surculosae, as the earliest diverging group in the tribe Cariceae. Low chromosome numbers, 2n = 12 or 24, with large sizes were observed in these three sections. Our results suggest that the genus Carex might have originated or relictly restricted in the East Asia. Geographical distributions of diploid species are restricted in narrower areas, while those of tetraploid species are wider in East Asia. It is concluded that chromosomal variations in Siderostictae clade may have been caused by polyploidization and that tetraploid species may have been able to exploit their habitats by polyploidization.
薹草属（莎草科）是开花植物中最大的属之一，包含超过 2000 个物种。在薹草属中，叶片较宽分布于东亚的石薹草组被认为是一个祖先进化群。我们旨在阐明石薹草组内的系统发育关系和染色体变异，并从 DNA 序列和细胞学数据来研究东亚的宽叶石薹草组、弯喙薹草组和薹草组之间的关系。我们的研究结果表明，石薹草组是薹草族中最早分化的一个单系群，包括石薹草组、弯喙薹草组和薹草组。在这三个组中，观察到低染色体数（2n=12 或 24）和较大的染色体大小。我们的结果表明，薹草属可能起源于东亚或在此处残遗。二倍体物种的地理分布范围较窄，而四倍体物种的地理分布范围较宽。可以得出结论，石薹草组的染色体变异可能是由多倍化引起的，而四倍体物种可能通过多倍化能够更好地利用其生境。
