The spatial distribution of cytotypes can provide valuable insights into the evolution of polyploid complexes. Previously, only tetraploid Allium oleraceum was reported from Slovakia. Analysing 863 individuals from 93 populations from Slovakia revealed an extensive variation in the DNA ploidy levels of Allium oleraceum (3x, 4x, 5x and 6x). Of the main cytotypes, the penta- and tetraploids had strongly overlapping distributions, although the pentaploids exhibited a tendency to occur more frequently in the southern and the tetraploids had a tendency to occur in the northern regions of Slovakia. A triploid cytotype was found in one population in the southern part of Slovakia, which is the third locality worldwide for this cytotype. The hexaploid cytotype was rare and sparsely occurred in western and southern Slovakia. Sixteen per cent of the populations sampled consisted of more than one ploidy level; the most common was a combination of penta- and tetraploids. The cytotypes differed with respect to altitude; the tetraploids were found significantly more frequently at higher altitudes than the penta- and hexaploids. When compared with reanalysed altitudinal distribution data from the Czech Republic divided into two geographic areas (Carpathian and Herzynian) the pattern found in the Carpathian part of the Czech Republic was similar to that in Slovakia, with tetraploids at the higher altitudes. The distribution in the Herzynian part (Bohemian Massif) was just the opposite: the tetraploids were more often found at lower altitudes than the penta- and hexaploids. Both tetra- and pentaploid cytotypes occurred in a wide and similar spectrum of habitats, while hexaploids were limited to human-influenced habitats. A local-scale distribution of cytotypes analysed in detail in the Slovak Karst area, showed surprising differences in the distribution of cytotypes on particular karst plains, which can be related to different land uses. Concerning the contrasting altitudinal differentiation of tetraploids in the regions compared, the results suggest that at least two different types of tetraploids occur in Central Europe. The apparent cytotype diversity in the surrounding Slovak Karst area may suggest the existence of a primary contact zone.
Despite the substantial knowledge of the variation in cytotypes at large spatial scales for many plants, little is known about the rates at which novel cytotypes arise or the frequencies and distributions of cytotypes at local spatial scales. The frequency distribution, local spatial structure, and role of habitat differentiation of tetra-, penta- and hexaploid cytotypes of the bulbous geophyte Allium oleraceum were assessed in 21 populations sampled in the Czech Republic. The ploidy levels determined by flow cytometry confirmed that there was a mixture consisting of two or three cytotypes (i.e. 4x+5x, 4x+6x, 5x+6x, 4x+5x+6x). In addition, mixtures of cytotypes were found at sites previously considered to be cytotype-homogeneous. At all sites previously found to contain a mixture of two cytotypes, no plants with the third ploidy level were found. Although the relative frequencies of cytotypes varied considerably both among and within populations, mixed populations consisting of tetra- and hexaploids were usually dominated by tetraploids. This suggests that there are secondary contacts among cytotypes but there is little gene flow among them except for the rare formation of hexaploids in tetraploid populations. Cytotypes were not randomly distributed over the study area but were spatially segregated at either 47.6% or 61.9% of the sites investigated, depending on the statistical test (Mantel test or average distance test) used. When the composition of habitats at each of the sites is taken into account, cytotypes were more frequently spatially segregated at sites with a heterogeneous environment than a homogeneous environment. This implies that the cytotypes are ecologically differentiated. The frequent co-occurrence of cytotypes, with or without significant spatial segregation, at many sites with heterogeneous or homogeneous environments, however, suggests that niche differentiation alone is probably ineffective in determining co-occurrence. It is supposed that the prevailing vegetative reproduction associated with local dispersal, a high population density of the species in a landscape, and non-equilibrial processes influencing the establishment and extinction of A. oleraceum populations can also support the local co-occurrence of cytotypes.
This paper deals with the flora and vegetation of stony walls (wall tops, vertical wall surfaces) in East Bohemia. In total, 207 species of vascular plants and 60 mosses were identified in 114 recorded relevés. Flora of walls is composed of a high number of accidental species. Only two species (Poa compressa, Taraxacum sect. Ruderalia) were frequently recorded on walls. Differences in species’ traits (life strategy, life form, dispersal) and ecological requirements of plants (light, moisture) were analysed between vertical wall surfaces and wall tops. Due to high floristic heterogeneity, many communities can be classified only at the level of higher syntaxa. In total, 10 communities were reported on the studied walls. Communities on wall tops were dominated by Poa compressa, P. palustris subsp. xerotica, P. nemoralis subsp. rigidula, Conyza canadensis and Syringa vulgaris. Four communities dominated by Corydalis lutea, Cymbalaria muralis, Asplenium ruta-muraria and Cystopteris fragilis were identified on vertical wall surfaces. Their structure, species composition, ecology and distribution are briefly discussed.
Perennial grasses belonging to the genus Molinia are widespread in most of Europe and consist of a polyploid complex of closely related taxa with a confusing taxonomy. Based on extensive sampling at 241 localities in Europe, four cytotypes were identified based on chromosome counts and results of flow cytometry: tetraploids (2n = 36), hexaploids (2n = 54), octoploids (2n = 72) and dodecaploids (2n = 108). While tetra- and dodecaploids were commonly recorded, octoploids were less common and only two hexaploid individuals were identified. Previously reported decaploid counts (2n = 90) from central Europe are probably erroneous and refer to 2n = 108. The tetraploid cytotype is distributed throughout Europe and broadly sympatric with other cytotypes. Octo- and dodecaploids were spatially separated with dodecaploids occurring in the western, central and south-central part of Europe and octoploids in the east-central and southeastern part of Europe. All quantitative characters measured (lengths of lemmas, anthers, caryopses and stomata, lengths of the longest hair on the callus and diameter of the culm below the panicle) showed a linear trend across ploidy levels. Tetra-, octo- and dodecaploid cytotypes formed almost non-overlapping groupings in principal component and discriminant analyses of morphological characters. The following taxonomic concept of this complex is proposed: Molinia caerulea (L.) Moench is a predominantly tetraploid taxon incorporating very rarely reported hexaploid and perhaps also diploid plants; higher cytotypes (2n = 8x, 12x) are considered to be M. arundinacea Schrank, consisting of two subspecies: a dodecaploid subspecies occurring in the southern and western part of central Europe and the octoploid Molinia arundinacea subsp. freyi Dančák in east-central and southeastern Europe.