Polyploidy and hybridization are key events in plant evolution. Due to these events, complexes of species can be formed. Dysploidy, a frequent chromosome change in holocentric organisms, may add some difficulties to species delimitation, especially in Cyperaceae. The Eleocharis montana complex is known for its members with overlapping morpho-anatomical features and unclear circumscription. To understand its biological history, several tools were used to investigate different American populations, including morpho-anatomical analysis, genome size estimates, cytogenomic analysis, molecular marker characterization, and genomic in situ hybridization (GISH). Despite overlapping morphological features, it was possible to separate two groups, the first containing E. parodii and E. subarticulata, presenting diploid and dysploid karyotypes, respectively, and small DNA C-values. The second contained E. elegans, E. contracta, and E. montana, with large genomes created by polyploidy. All analyses suggest that E. montana with 2n = 40 is a cytotype of E. contracta with 2n = 20, and both evolved from a natural hybridization involving E. parodii (2n = 10) and a second progenitor that is yet unknown. Furthermore, the GISH results indicated that E. parodii may be an ancestor of E. elegans. All species occur in the probable center of diversification in Austral South America, where the hybridization zone is identified. Fieldwork and information obtained from herbaria indicate that diploid and dysploid species (E. subarticulata and E. parodii) do not occur beyond the center of diversification. However, E. elegans and specially E. montana occur more widely, occupying different flooded environments and landscapes.

中文翻译：

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Eleocharis montana 复合体（莎草科）全中心种的异源多倍体和基因组分化

多倍体和杂交是植物进化中的关键事件。由于这些事件，可以形成物种复合体。异倍体是全中心生物中频繁发生的染色体变化，可能会给物种定界增加一些困难，尤其是在莎草科中。Eleocharis montana 复合体以其具有重叠的形态解剖特征和不清楚的界限的成员而闻名。为了了解其生物学历史，使用了多种工具来研究不同的美国种群，包括形态解剖分析、基因组大小估计、细胞基因组分析、分子标记表征和基因组原位杂交 (GISH)。尽管有重叠的形态特征，但可以将两组分开，第一组包含 E. parodii 和 E. subarticulata，分别呈现二倍体和异倍体核型，和小的 DNA C 值。第二个包含 E. elegans、E. contracta 和 E. montana，具有由多倍体产生的大型基因组。所有分析都表明，2n = 40 的蒙大拿 E. contracta 是 2n = 20 的 E. contracta 的细胞型，并且两者都是从涉及 E. parodii (2n = 10) 和未知的第二祖细胞的自然杂交进化而来的。此外，GISH 结果表明 E. parodii 可能是 E. elegans 的祖先。所有物种都出现在南美洲南部可能的多样化中心，在那里确定了杂交区。从植物标本馆获得的实地调查和信息表明，二倍体和异倍体物种（E. subarticulata 和 E. parodii）不会出现在多样化中心之外。然而，E. elegans 尤其是 E. montana 出现得更广泛，