Deschampsia P. Beauv. is a cosmopolitan grass genus, which grows in cold and temperate regions, including about 15 species growing in South America and Antarctica. The species delimitation is difficult due to the high phenotypic plasticity and the likely occurrence of hybridization which generates species complexes with high morphological affinity. This work aims to describe the cytogenetic traits of the South American species of Deschampsia, highlighting similarities and differences in a phylogenetic context. We report the chromosome number of seven species of Deschampsia and Deyeuxia eminens for the first time, verifying that basic chromosome number x = 13 is shared by all the species. We found that the phylogenetic relationships are in agreement with the morphological affinities described in the species revisions, and the species of Deschampsia and Deyeuxia Sect. Stylagrostis form a well-supported clade. Despite the variation from x = 13 reported for populations of Deschampsia in the northern hemisphere, all the South American and Antarctic taxa studied here have a conserved basic chromosome number. Polyploids were found in several species, which suggests that genomic duplication is a recurrent process in the evolutionary history of Deschampsia. In contrast with the conserved chromosome morphology, the rDNA pattern showed high intra- and inter-specific variability and it is related to the phylogeny. Particularly, the complex of D. cespitosa is polymorphic for the distribution pattern of rDNA, as was also seen for molecular and morphological traits. Our results suggest that the common ancestor between Deschampsia and Deyeuxia sec. Stylagrostis could have had chromosomal characteristics currently shared by both. The incorporation of new chromosomal, molecular, and morphological data in Deyeuxia species will allow clarification of the close phylogenetic relationship with Deschampsia, in which reticulation and hybridization events cannot be excluded.

Deschampsia P.Beauv。是世界性的草属，生长在寒冷和温带地区，包括在南美和南极洲生长的约15种。由于高的表型可塑性和可能发生杂交而产生高形态学亲和力的物种复合物，很难对物种进行划界。这项工作旨在描述南美洲Deschampsia物种的细胞遗传学特征，突出系统进化背景下的异同。我们报告了德尚和德约克夏七种物种的染色体数首次验证所有物种共有基本染色体数x = 13。我们发现，系统发育关系与物种修订以及德尚和德约克夏科中描述的形态亲和力相符。剑兰形成支撑良好的进化枝。尽管报告的北半球Deschampsia种群的x = 13有所不同，但此处研究的所有南美和南极分类群均具有保守的基本染色体数。在几个物种中发现了多倍体，这表明基因组重复是德尚的进化历史中的一个复发过程。与保守的染色体形态相反，rDNA模式显示出较高的种内和种间变异性，并且与系统发育有关。特别地，切丁头孢菌的复合物对于rDNA的分布模式是多态的，如在分子和形态学特征上也可见。我们的结果表明，德尚和德约西亚之间有共同的祖先。香菇可能具有目前由双方共享的染色体特征。在Deyeuxia物种中纳入新的染色体，分子和形态学数据将有助于阐明与Deschampsia密切的系统发育关系，其中不能排除网状和杂交事件。