Diploids and tetraploids commonly coexist at all spatial scales and exhibit considerable temporal stability in local ploidy mixtures. Mixed-ploidy populations containing fertile triploid hybrids probaby act as effective generators of cytogenetic novelty and may facilitate inter-ploidy gene flow. Neopolyploid mutants were incapable of local establishment.

The sixth part of the series on the distributions of vascular plants in the Czech Republic includes grid maps of 112 taxa in the genera Athyrium,

Aim While environmental conditions are reported as important determinants of cytotype distribution patterns in some mixed‐ploidy plant species, in others they seem to play no role. One reason for such inconsistency might be how and at what spatial scale the ecology of different cytotypes is compared. To address this issue, we adopted several complementary approaches to assess ecological requirements of cytotypes in a single species across wide‐range of spatial scales. Location Europe. Taxon Tripleurospermum inodorum (Asteraceae). Methods WorldClim extracted data were used for comparing climatic niches of T. inodorum diploids and tetraploids at continental and subcontinental scales and for predicting climatic suitability of habitats in Europe. Within the contact zone of cytotypes, at the regional scale, ecological preferences of cytotypes were assessed independently in three regions. Habitat types and ecological indicators inferred from species composition of vegetation in both uniform‐ploidy and mixed‐ploidy populations were used for ecological niche reconstructions. Results The two cytotypes differed in their climatic niches. However, due to considerable niche overlap, diploids and tetraploids were predicted to co‐occur in an extensive contact zone in Europe. Within the contact zone, cytotypes had identical ecological preferences but varied in their frequency at particular habitat types. The ecological niches of mixed‐ploidy and uniform‐ploidy populations were undistinguishable. Main conclusions Cytotype distribution patterns may be shaped by multiple environmental forces, each operating at a different spatial scale. In T. inodorum, climate is an important driver of cytotype distribution patterns at continental scale, however, at finer scales within the contact zone, the founder effect and non‐random migration patterns caused by human activities seem to be more important than environmental heterogeneity. The use of independent replicates and/or across‐scale comparisons can significantly improve the performance of ecological niche assessments.

The patterns of morphological variation and distribution of the rare Central European endemic Spergularia echinosperma were investigated. Morphometric analyses revealed the existence of two distinct morphotypes differing each other mainly in seed color, which is either brown or black. Other differences are in density of the seed surface papillae, height and shape of the papillae, seed width, pedicel/capsule and internode/leaf ratios, and leaf length. A geographic separation of the morphotypes also exists. The black-seeded morphotype occurred nearly exclusively in drained fishponds in the south-western part of the Czech Republic, the brown-seeded morphotype was found in drained fishponds in the eastern part of the Czech Republic and in alluvial pools and river deposits of the Elbe River (Germany). We hypothesize that the black-seeded morphotype may have been indigenous in former natural lakes which were widespread in the SW-Czech Republic and they were frequently transformed into fishponds. The brown-seeded morphotype may have its origin in river alluvia of the Elbe (Germany) and possibly also of other rivers in the Czech Republic. Since the two morphotypes are morphologically and geographically well separated, we propose to describe the brown-seeded morphotype as a new subspecies for science, S. echinosperma subsp. albensis subsp. nov.