Journal Article

Cytotype distribution at a diploid–hexaploid contact zone in <i>Aster amellus</i> (Asteraceae)

S. Castro, J. Loureiro, T. Procházka and Z. Münzbergová

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 110, issue 5, pages 1047-1055
Published in print October 2012 | ISSN: 0305-7364
Published online August 2012 | e-ISSN: 1095-8290 | DOI:
Cytotype distribution at a diploid–hexaploid contact zone in Aster amellus (Asteraceae)

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


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Background and Aims

The present study aims to assess the diversity and distribution of cytotypes of Aster amellus in central and eastern Europe, contributing with data to improve understanding of the evolutionary dynamics of the contact zone between diploids and hexaploids of this polyploid complex.


Large-scale cytotype screening of 4720 individuals collected in 229 populations was performed using 4′,6-diamidino-2-phenylindole (DAPI) flow cytometry. Fine-scale cytotype screening was performed in the mixed-ploidy population. Reproductive variables, such as number of florets per flower head, seed set and seedling emergence, as well as ploidy level of seeds and seedlings were recorded in this population.

Key Results

The diploid–hexaploid contact zone is large and complex, reaching the Czech Republic in the west, Austria in the south, Poland in the north-east and Romania in the extreme east of the surveyed areas. Most populations presented only one cytotype, either diploid or hexaploid. In several areas of the contact zone both cytotypes were found to grow in parapatry. One mixed-ploidy population of diploids and hexaploids was detected for the first time, but no signs of hybridization were detected. In this population, diploids had a significantly lower reproductive success, and significantly higher production of intercytotype offspring, being in reproductive disadvantage in comparison with hexaploids.


The contact zone of diploid and hexaploid A. amellus in central and eastern Europe seems to be highly dynamic and diffuse, with both primary and secondary contacts being possible. The obtained results suggest the origin of hexaploids through diploids, overall supporting previous hypotheses that this species is autopolyploid. Data from the only mixed-ploidy population detected so far suggest that the minority cytotype exclusion is an important evolutionary mechanisms driving the prevalence of single-cytotype populations, and thus contributing to the current distributional patterns of the cytotypes of A. amellus.

Keywords: Aster amellus; contact zone; cytotypes; diploids; DNA ploidy level; flow cytometry; hexaploids; hybridization; polyploid aggregate; spatial distribution; tetraploids

Journal Article.  5679 words.  Illustrated.

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

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