Journal Article

Complex distribution patterns, ecology and coexistence of ploidy levels of <i>Allium oleraceum</i> (Alliaceae) in the Czech Republic

Martin Duchoslav, Lenka Šafářová and František Krahulec

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 105, issue 5, pages 719-735
Published in print May 2010 | ISSN: 0305-7364
Published online April 2010 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcq035
Complex distribution patterns, ecology and coexistence of ploidy levels of Allium oleraceum (Alliaceae) in the Czech Republic

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry

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Background and Aims

Despite extensive study of polyploidy, its origin, and ecogeographical differences between polyploids and their diploid progenitors, few studies have addressed ploidy-level structure and patterns of ecogeographical differentiation at various spatial scales using detailed sampling procedures. The pattern of coexistence of polyploids in the geophyte Allium oleraceum at the landscape and locality scale and their ecology were studied.

Methods

Flow cytometry and root-tip squashes were used to identify the ploidy level of 4347 plants from 325 populations sampled from the Czech Republic using a stratified random sampling procedure. Ecological differentiation among ploidy levels was tested by comparing sets of environmental variables recorded at each locality.

Key Results

Across the entire sampling area, pentaploids (2n = 5x = 40) predominated, while hexaploids (2n = 6x = 48) and tetraploids (2n = 4x = 32) were less frequent. The distribution of tetra- and hexaploids was partially sympatric (in the eastern part) to parapatric (in the western part of the Czech Republic) whereas pentaploids were sympatric with other cytotypes. Plants of different ploidy levels were found to be ecologically differentiated and the ruderal character of cytotypes increased in the direction 4x → 5x → 6x with the largest realized niche differences between tetra- and hexaploids. Most populations contained only one ploidy level (77 %), 22 % had two (all possible combinations) and 1 % were composed of three ploidy levels. The majority of 4x + 5x and 5x + 6x mixed populations occurred in sympatry with uniform populations of the participating cytotypes in sites with ecologically heterogeneous or marginal environment, suggesting secondary contact between cytotypes. Some mixed 4x + 6x populations dominated by tetraploids being sympatric and intermixed with uniform 4x populations might represent primary zones of cytotype contact. Almost no mixed accessions were observed on the fine spatial scale in mixed populations.

Conclusions

The results provide evidence for adaptive differences among ploidy levels, which may contribute to their complex distribution pattern. The prevalence of asexual reproduction, limited dispersal and equilibrium-disrupting processes may support local coexistence of cytotypes.

Keywords: Allium oleraceum; contact zones; Czech Republic; ecological differentiation; distribution; DNA ploidy level; ploidy mixture; polyploidy; spatial scales

Journal Article.  12303 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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