Chromosome numbers of 23 species (including subspecies) of Hieracium s. str. from the Western Carpathians are presented. First chromosome numbers are reported for Hieracium kuekenthalianum (= H. tephrosoma, 2n = 36), H. praecurrens (2n = 27) and H. virgicaule (2n = 27); first counts from the Western Carpathians are given for H. atratum (2n = 27), H. bifidum (2n = 27, 36), H. carpathicum (2n = 36), H. inuloides (2n = 27), H. jurassicum (2n = 27), H. macilentum (= H. epimedium, 2n = 27), H. nigritum (2n = 36), H. pilosum (= H. morisianum, 2n = 27) and H. silesiacum (2n = 36). New ploidy level (tetraploid, 2n = 36) is reported for H. bupleuroides, hitherto published counts refer only to triploids (2n = 27). Previously published chromosome numbers were confirmed for several other species, i.e. H. alpinum (s.str., 2n = 27), H. bupleuroides (2n = 27), H. crassipedipilum (H. fritzei group, 2n = 27, 36), H. lachenalii (2n = 27), H. murorum (2n = 27), H. prenanthoides (2n = 27), H. racemosum (2n = 27), H. sabaudum (2n = 27), H. slovacum (H. fritzei group, 2n = 36), and H. umbellatum (2n = 18). Triploids and tetraploids predominate, diploids (2n = 18) were found in H. umbellatum. A comprehensive list of previously published chromosome numbers in Hieracium s. str. from the Western Carpathians is provided.
Liverworts are poorly represented in the record of DNA C-values. Data for not more than nine species are reported in the literature. Here we present flowcytometric measurements of genome size for 32 foliose and 11 thallose species from 22 out of 83 families. The main method used in this study was flow cytometry using propidium iodide as the DNA stain. Feulgen densitometrywas applied as a supplementary method but it proved less suitable because the rigid cellwalls of liverwort tissue are resistant to maceration and apparently often inhibit the diffusion of reagents, which results in low estimates of DNA content. The precise or approximate number of chromosomes were counted, where possible. Among the thallose liverworts, the lowest 1C-value was recorded for Marchantia polymorpha (0.293 pg) and the highest for diploid Pellia epiphylla (7.401 pg). Haploid P. epiphylla (1C = 3.803 pg) had the largest genome among the haploid thalloid liverworts. Among the foliose liverworts, Lejeunea cavifolia with a value of 0.211 pg (1C) was ranked the lowest and Mylia taylorii, a haploid with 7.966 pg (1C) and a large amount of dense heterochromatin, concentrated in one big spherical chromocentre, the highest. This 38-fold variation covers the extremes of the whole sample and exceeds the ca 12-fold variation recorded in mosses (0.174–2.160 pg, 1C). This variation is nevertheless low compared to the 2000-fold interspecific variation found in angiosperms. Several instances of intraspecific variation in DNA ploidy (x and 2x) were found – in Radula complanata, Pellia epiphylla and Metzgeria furcata. In Lophocolea heterophylla, accessions differed 3.37-fold in C-value at haploid chromosome number. This points to cryptic taxonomic differentiation and warns against premature statements about ploidy levels based only on DNA measurements. Significant intraspecific intraploidal variation in C-value was also observed in certain instances. In Frullania dilatata, female plants with two large heterochromatic sex-chromosomes have a 1.35-fold higher C-value than male plants with only one sex chromosome. In most other cases of intraspecific variation the role of sex differences remains to be clarified.
Gymnadenia densiflora was recently either misinterpreted or not accepted as a distinct taxon by several authors. To resolve its taxonomic position and differentiation from the related G. conopsea, a detailed study of the morphology, chromosome numbers and distribution of these two taxa in the Czech Republic, Slovakia and neighbouring areas was carried out. Chromosome counts showed an invariable diploid chromosome number (2n = 40) for G. densiflora, while G. conopsea is diploid, tetraploid and rarely also pentaploid (2n = 40, 80, 100). Results of morphometric analyses (principal component analysis, cluster analysis, classificatory and canonical discriminant analysis) confirmed a good morphological separation between G. densiflora and G. conopsea. Characters such as the width of the second lowermost leaf, height of the plant, number of flowers in the inflorescence, number of leaves, and the ratio of height of the plant and distance from the stem base to the base of the uppermost sheathed leaf contributed most to this separation. Our study supports the recognition of G. densiflora as a distinct species.
Populations of Pilosella (Hieracium subgenus Pilosella) at ruderal localities were investigated in an urban area (Prague City) with respect to their distribution, variation in DNA ploidy level/chromosome number and mode of reproduction. The following species, hybridogenous species or hybrids (with ploidy level/chromosome number and mode of reproduction) were found: P. aurantiaca, P. caespitosa (4x, 5x), P. cymosa subsp. vaillantii (5x), P. officinarum (2n = 36, sexual; 2n = 54, sexual; 2n = 63), P. piloselloides subsp. bauhinii (2n = 45, 54; both apomictic), P. piloselloides subsp. praealta (5x; apomictic), P. brachiata (4x; sterile), P. densiflora, P. flagellaris, P. floribunda, P. erythrochrista, P. glomerata (5x; apomictic), P. leptophyton (5x; apomictic), P. rothiana (4x, apomictic), P. setigera, P. visianii (4x; apomictic), P. ziziana (4x, apomictic) and the previously undescribed hybridogenous type P. piloselloides × P. setigera (5x, apomictic). Pilosella visianii is reported from the Czech Republic for the first time. New habitats resulting from highway construction are suitable for Pilosella species. Many previously rare types, such as P. rothiana, can colonize these habitats and spread, not only locally, but also throughout the whole country.
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.
The present paper summarizes the results of research of Hieracium subgen. Pilosella done by using different methods. The apomictic complex of Hieracium subgen. Pilosella found in the Krkonoše Mts, consists of the following basic species: H. lactucella (2x, sexual), H. onegense (2x, sexual), H. pilosella (4x, sexual), H. caespitosum (4x, apomictic) and H. aurantiacum (4x and 5x, apomictic). These species are considered to be the parents of a further set of mostly apomictic hybridogenous types. The ploidy level, breeding system, isozyme phenotypes, chloroplast haplotypes and geographic distribution of this whole complex was analysed. The different hybridogenous types have different frequencies in the field and differ in the frequency of isozyme phenotypes (a conservative estimate of the number of genotypes). Most have uniform chloroplast haplotypes, but some haplotypes could have originated from reciprocal crosses. The comparison of chloroplast haplotypes suggests that apomictic species were not only pollen donors, but also contributed seed and gave rise to several hybridogenous types, illustrating the importance of the residual sexuality of apomicts in this group. H. pilosella is a central species in this group and is connected with other parental species, H. floribundum, H. lactucella and H. aurantiacum by a set of hybridogenous species that have a similar genetic structure. Some of the distinct hybridogenous types within the complex are of multiple origin. In contrast, crosses between the same parental types may generate diverse progenies, which can often be classified as distinct taxa. All taxa recorded in the past are surveyed and discussed with respect to present knowledge. We suggest that the taxonomy and origin of particular entities of this and other such complexes is best resolved using information from morphological, genetical, cytological and ecological studies.
A population of a hybrid between Tragopogon porrifolius and T. pratensis (T. ×mirabilis), which occurs in SW part of the town of Roudnice nad Labem, N part of Central Bohemia, was analysed with respect to its morphology, fertility, life history, ploidy level and DNA content. Both parental species vary relatively little morphologically; they are biennials (monocarpic perennials) and diploids. T. pratensis is a native species in the Czech Republic, T. porrifolius was cultivated there in the past. The hybrid plants are extremely morphologically variable, with variation ranges of some characters overlapping those of the parental species (e.g. ligules are often longer than involucral bracts, peduncles are often lanate). Only diploids were found within the hybrid population; however, they have substantially lower DNA content than both parents (18% lower than T. pratensis, 42% lower than T. porrifolius). The plants of the Roudnice hybrid population are polycarpic perennials in contrast to the monocarpic perennial (mostly biennial) parents. The distribution is described in detail; it shows that the hybrid plants are spreading and at present even occur outside the town. The long-persisting population of fertile diploid hybrid plants in Roudnice nad Labem is an alternative evolutionary pathway to that of the allotetraploid Tragopogon species known from North America.