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Exploring the fitness consequences of whole-genome multiplication (WGM) is essential for understanding the establishment of autopolyploids in diploid parental populations, but suitable model systems are rare. We examined the impact of WGM on reproductive traits in three major cytotypes (2x, 3x, 4x) of Pilosella rhodopea, a species with recurrent formation of neo-autopolyploids in mixed-ploidy populations. We found that diploids had normal female sporogenesis and gametogenesis, high fertility, and produced predominantly euploid seed progeny. By contrast, autopolyploids had highly disturbed developmental programs that resulted in significantly lower seed set and a high frequency of aneuploid progeny. All cytotypes, but particularly triploids, produced gametes of varying ploidy, including unreduced ones, that participated in frequent intercytotype mating. Noteworthy, the reduced investment in sexual reproduction in autopolyploids was compensated by increased production of axillary rosettes and the novel expression of two clonal traits: adventitious rosettes on roots (root-sprouting), and aposporous initial cells in ovules which, however, do not result in functional apomixis. The combination of increased vegetative clonal growth in autopolyploids and frequent intercytotype mating are key mechanisms involved in the formation and maintenance of the largest diploid-autopolyploid primary contact zone ever recorded in angiosperms.
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Fertilidade , Ploidias , Diploide , Reprodução , Sementes , PoliploidiaRESUMO
Herbarium collections shape our understanding of Earth's flora and are crucial for addressing global change issues. Their formation, however, is not free from sociopolitical issues of immediate relevance. Despite increasing efforts addressing issues of representation and colonialism in natural history collections, herbaria have received comparatively less attention. While it has been noted that the majority of plant specimens are housed in the Global North, the extent and magnitude of this disparity have not been quantified. Here we examine the colonial legacy of botanical collections, analysing 85,621,930 specimen records and assessing survey responses from 92 herbarium collections across 39 countries. We find an inverse relationship between where plant diversity exists in nature and where it is housed in herbaria. Such disparities persist across physical and digital realms despite overt colonialism ending over half a century ago. We emphasize the need for acknowledging the colonial history of herbarium collections and implementing a more equitable global paradigm for their collection, curation and use.
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Plantas , Humanos , Inquéritos e QuestionáriosRESUMO
Spatial segregation of cytotypes reduces the negative effect of frequency-dependent mating on the fitness of minority cytotype(s) and thus allows its establishment and coexistence with the majority cytotype in mixed-ploidy populations. Despite its evolutionary importance, the stability of spatial segregation is largely unknown. Furthermore, closely related sympatric cytotypes that differ in their life histories might exhibit contrasting spatial dynamics over time. We studied the temporal stability of spatial structure at a secondary contact zone of co-occurring monocarpic diploids and polycarpic tetraploids of Centaurea stoebe, whose tetraploid cytotype has undergone a rapid range expansion in Europe and became invasive in North America. Eleven years after the initial screening, we re-assessed the microspatial distribution of diploids and tetraploids and their affinities to varying vegetation-cover density in three mixed-ploidy populations in Central Europe. We found that overall, spatial patterns and frequencies of both cytotypes in all sites were very similar over time, with one exception. At one site, in one previously purely 2x patch, diploids completely disappeared due to intensive succession by shrubby vegetation. The remaining spatial patterns, however, showed the same cytotype clumping and higher frequency of 2x despite subtle changes in vegetation-cover densities. In contrast to the expected expansion of polycarpic tetraploids having higher colonization ability when compared to diploids, the tetraploids remained confined to their former microsites and showed no spatial expansion. Spatial patterns of coexisting diploids and tetraploids, which exhibit contrasting life histories, did not change over more than a decade. Such temporal stability is likely caused by relatively stable habitat conditions and very limited seed dispersal. Our results thus imply that in the absence of a disturbance regime connected with frequent human- or animal-mediated seed dispersal, spatial patterns may be very stable over time, thus contributing to the long-term coexistence of cytotypes.
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High reproductive assurance is regarded as a key advantage of uniparentally reproducing organisms for establishing a new population. This demographic benefit should especially be relevant for plants with autonomous apomixis, that is those which produce seeds completely independently from mates and pollinators. Indeed, many autonomous apomicts occupy larger distributional ranges when compared to their sexual relatives, showing geographical parthenogenesis patterns. However, uniparental reproduction advantage has only rarely been quantified in natural populations and results provided a mixed support, partly because allopatric sexual and asexual populations were exposed to different environmental and pollination conditions causing considerable between-population variation in the level of reproductive assurance. Here, we compared the level and stability of reproductive assurance between sexual self-incompatible and asexual autonomously apomictic plants of Hieracium alpinum (Asteraceae) cultivated in a sympatric low-density population with two levels of spatial clumping of sexual plants. Overall, we found that the realized seed set (i.e. proportion of well-developed seeds per capitulum) of asexuals was ca. 3 times greater than that of sexuals (83% vs. 27%), whereas the variance of this trait expressed as coefficient of variation was ca. 4 times smaller in asexuals compared with sexuals (19% vs. 83%). Solitary sexual plants had more than 2 times lower realized seed set when compared to clumps composed of two spatially close (20-30 cm) sexual plants (13% vs. 34%). Our study provides experimental evidence for benefit of uniparental reproduction of asexuals in a sympatric situation when the availability of mates is limited. This, together with unpredictability of pollinator environment could provide autonomous apomicts with an ultimate demographic superiority during colonization reflected in geographical parthenogenesis observed in this species.
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Apomixia , Apomixia/genética , Plantas , Pólen , Reprodução , Sementes , SimpatriaRESUMO
Molecular evolution of ribosomal DNA can be highly dynamic. Hundreds to thousands of copies in the genome are subject to concerted evolution, which homogenizes sequence variants to different degrees. If well homogenized, sequences are suitable for phylogeny reconstruction; if not, sequence polymorphism has to be handled appropriately. Here we investigate non-coding rDNA sequences (ITS/ETS, 5S-NTS) along with the chromosomal organization of their respective loci (45S and 5S rDNA) in diploids of the Hieraciinae. The subtribe consists of genera Hieracium, Pilosella, Andryala, and Hispidella and has a complex evolutionary history characterized by ancient intergeneric hybridization, allele sharing among species, and incomplete lineage sorting. Direct or cloned Sanger sequences and phased alleles derived from Illumina genome sequencing were subjected to phylogenetic analyses. Patterns of homogenization and tree topologies based on the three regions were compared. In contrast to most other plant groups, 5S-NTS sequences were generally better homogenized than ITS and ETS sequences. A novel case of ancient intergeneric hybridization between Hispidella and Hieracium was inferred, and some further incongruences between the trees were found, suggesting independent evolution of these regions. In some species, homogenization of ITS/ETS and 5S-NTS sequences proceeded in different directions although the 5S rDNA locus always occurred on the same chromosome with one 45S rDNA locus. The ancestral rDNA organization in the Hieraciinae comprised 4 loci of 45S rDNA in terminal positions and 2 loci of 5S rDNA in interstitial positions per diploid genome. In Hieracium, some deviations from this general pattern were found (3, 6, or 7 loci of 45S rDNA; three loci of 5S rDNA). Some of these deviations concerned intraspecific variation, and most of them occurred at the tips of the tree or independently in different lineages. This indicates that the organization of rDNA loci is more dynamic than the evolution of sequences contained in them and that locus number is therefore largely unsuitable to inform about species relationships in Hieracium. No consistent differences in the degree of sequence homogenization and the number of 45S rDNA loci were found, suggesting interlocus concerted evolution.
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This paper deals with the typification and taxonomy of five Mediterranean Cytisus species. Cytisus affinis, C. candidus, and C. spinescens nom. illeg., non Sieber ex Spreng. were described from Sicily by Karel Borivoj Presl, Cytisus spinescens was described from Apulia (southern Italy) by Curt Polycarp Joachim Sprengel, and C. villosus was described from southern France by Pierre André Pourret (1788). Lectotypes are here designated for Presl and Sprengel's names. A neotype is designated for C. villosus. The taxonomic revision of these five names confirmed that C. villosus Pourr. (= Cytisus affinis C.Presl) is the name to be used for the species occurring in the large part of the Mediterranean countries. Cytisus spinescens Sieber ex Spreng. (≡ C. candidus C.Presl = C. spinescens C.Presl, nom. illeg.) is the correct name for the amphi-adriatic species occurring in peninsular Italy, and along the NE coast of the Adriatic Sea. This species does not occur in Sicily and reference to this latter region in the protologues of both C. spinescens C.Presl and C. candidus C.Presl is a misinterpretation due, possibly, to exchange of labels.
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PREMISE: The origin of allopolyploids is believed to shape their evolutionary potential, ecology, and geographical ranges. Morphologically distinct apomictic types sharing the same parental species belong to the most challenging groups of polyploids. We evaluated the origins and variation of two triploid taxa (Hieracium pallidiflorum, H. picroides) presumably derived from the same diploid parental pair (H. intybaceum, H. prenanthoides). METHODS: We used a suite of approaches ranging from morphological, phylogenetic (three unlinked molecular markers), and cytogenetic analyses (in situ hybridization) to genome size screening and genome skimming. RESULTS: Genotyping proved the expected parentage of all analyzed accessions of H. pallidiflorum and H. picroides and revealed that nearly all of them originated independently. Genome sizes and genome dosage largely corresponded to morphology, whereas the maternal origin of the allopolyploids had no discernable effect. Polyploid accessions of both parental species usually contained genetic material from other species. Given the phylogenetic distance of the parents, their chromosomes appeared only weakly differentiated in genomic in situ hybridization (GISH), as well as in overall comparisons of the repetitive fraction of their genomes. Furthermore, the repeatome of a phylogenetically more closely related species (H. umbellatum) differed significantly more. CONCLUSIONS: We proved (1) multiple origins of hybridogeneous apomicts from the same diploid parental taxa, and (2) allopolyploid origins of polyploid accessions of the parental species. We also showed that the evolutionary dynamics of very fast evolving markers such as satellite DNA or transposable elements does not necessarily follow patterns of speciation.
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Evolução Biológica , Poliploidia , Diploide , Genoma de Planta , Genômica , Humanos , FilogeniaRESUMO
Background and Aims: Apomixis or asexual seed reproduction is a key evolutionary mechanism in certain angiosperms providing them with reproductive assurance and isolation. Nevertheless, the frequency of apomixis is largely unknown, especially in groups with autonomous apomixis such as the diploid-polyploid genus Hieracium. Methods: Using flow cytometric analyses, we determined the ploidy level and reproductive pathways (sexual vs. apomictic) for 7616 seeds originating from 946 plants belonging to >50 taxa sampled at 130 sites across Europe. Key Results: Diploid seeds produced by diploids were formed exclusively by the sexual pathway after double fertilization of reduced embryo sacs. An absolute majority of tri- and tetraploid seeds (99.6 %) produced by tri- and tetrapolyploid taxa were formed by autonomous apomixis. Only 20 polyploid seeds (0.4 %) were formed sexually. These seeds, which originated on seven polyploid accessions of four taxa, were formed after fertilization of either unreduced embryo sacs through a so-called triploid bridge or reduced embryo sacs, and frequently resulted in progeny with an increased ploidy. In addition, the formation of seedlings with increased ploidy (4x and 6x) was found in two triploid plants. This is the first firm evidence on functional facultative apomixis in polyploid members of Hieracium sensu stricto (s.s.). Conclusions: The mode of reproduction in Hieracium s.s. is tightly associated with ploidy. While diploids produce seeds exclusively sexually, polyploids produce seeds by obligate or almost obligate apomixis. Strict apomixis can increase the reproductive assurance and this in turn can increase the colonization ability of apomicts. Nevertheless, our data clearly show that certain polyploid plants are still able to reproduce sexually and contribute to the formation of new cytotypes and genotypes. The finding of functional facultative apomicts is essential for future studies focused on evolution, inheritance and ecological significance of apomixis in this genus.
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Apomixia , Asteraceae/fisiologia , Diploide , Fertilização , PoliploidiaRESUMO
PREMISE OF THE STUDY: Genome duplication is associated with multiple changes at different levels, including interactions with pollinators and herbivores. Yet little is known whether polyploidy may also shape belowground interactions. METHODS: To elucidate potential ploidy-specific interactions with arbuscular mycorrhizal fungi (AMF), we compared mycorrhizal colonization and assembly of AMF communities in roots of diploid and tetraploid Centaurea stoebe s.l. (Asteraceae) co-occurring in a Central European population. In a follow-up greenhouse experiment, we tested inter-cytotype differences in mycorrhizal growth response by combining ploidy, substrate, and inoculation with native AMF in a full-factorial design. KEY RESULTS: All sampled plants were highly colonized by AMF, with the Glomeraceae predominating. AMF-community composition revealed by 454-pyrosequencing reflected the spatial distribution of the hosts, but not their ploidy level or soil characteristics. In the greenhouse experiment, the tetraploids produced more shoot biomass than the diploids did when grown in a more fertile substrate, while no inter-cytotype differences were found in a less fertile substrate. AMF inoculation significantly reduced plant growth and improved P uptake, but its effects did not differ between the cytotypes. CONCLUSIONS: The results do not support our hypotheses that the cytotype structure in a mixed-ploidy population of C. stoebe is mirrored in AMF-community composition and that ploidy-specific fungal communities contribute to cytotype co-existence. Causes and implications of the observed negative growth response to AMF are discussed.
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Centaurea/genética , Centaurea/microbiologia , Micorrizas/crescimento & desenvolvimento , Diploide , Fertilizantes , TetraploidiaRESUMO
Species may become invasive after introduction to a new range because phenotypic traits pre-adapt them to spread and become dominant. In addition, adaptation to novel selection pressures in the introduced range may further increase their potential to become invasive. The diploid Leucanthemum vulgare and the tetraploid L. ircutianum are native to Eurasia and have been introduced to North America, but only L. vulgare has become invasive. To investigate whether phenotypic differences between the two species in Eurasia could explain the higher abundance of L. vulgare in North America and whether rapid evolution in the introduced range may have contributed to its invasion success, we grew 20 L. vulgare and 21 L. ircutianum populations from Eurasia and 21 L. vulgare populations from North America under standardized conditions and recorded performance and functional traits. In addition, we recorded morphological traits to investigate whether the two closely related species can be clearly distinguished by morphological means and to what extent morphological traits have changed in L. vulgare post-introduction. We found pronounced phenotypic differences between L. vulgare and L. ircutianum from the native range as well as between L. vulgare from the native and introduced ranges. The two species differed significantly in morphology but only moderately in functional or performance traits that could have explained the higher invasion success of L. vulgare in North America. In contrast, leaf morphology was similar between L. vulgare from the native and introduced range, but plants from North America flowered later, were larger and had more and larger flower heads than those from Eurasia. In summary, we found litte evidence that specific traits of L. vulgare may have pre-adapted this species to become more invasive than L. ircutianum, but our results indicate that rapid evolution in the introduced range likely contributed to the invasion success of L. vulgare.
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Asteraceae/anatomia & histologia , Asteraceae/genética , Espécies Introduzidas , Aclimatação , Asteraceae/fisiologia , Evolução Biológica , Biomassa , Europa (Continente) , Inflorescência/genética , Inflorescência/fisiologia , Modelos Lineares , Oriente Médio , América do Norte , Fenótipo , Folhas de Planta/anatomia & histologia , Folhas de Planta/genética , Análise de Componente PrincipalRESUMO
PREMISE OF THE STUDY: The phenotype of an individual can be modified by the environment experienced by its predecessors, a phenomenon called transgenerational or maternal effects. These effects are studied mostly across sexual generations and are thought to be mediated also by epigenetic variation. However, we do not know how important transgenerational effects are across asexual generations of clonal plants. METHODS: We investigated the role of different drought intensities and durations experienced by parental plants of Trifolium repens on the growth of offspring ramets after transplantation of clonal cuttings to control conditions. We also treated half of the plants with 5-azacytidine, which is a demethylating agent, to test the potential role of DNA methylation on transgenerational effects. KEY RESULTS: Transgenerational effects were manifested as increased biomass of offspring ramets if parental plants experienced medium drought applied for a short period and decreased biomass of offspring ramets if parental plants experienced intense drought for a short period. These transgenerational effects were not observed for offspring of parents from the same treatments if these were treated with 5-azacytidine, whose application significantly decreased the amount of 5-methyl-2'-deoxycytidine in plants. CONCLUSIONS: Transgenerational effects might play an important role in the clonal plant Trifolium repens and are probably mediated by epigenetic variation. The growth and behavior of clonal plants might be affected not only by the ambient environment but also by environments that are no longer present at the time of clonal reproduction. This phenomenon can have yet unacknowledged ecological and evolutionary implications for clonal plants.
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Secas , Reprodução Assexuada , Estresse Fisiológico , Trifolium/fisiologia , Biomassa , Fenótipo , Trifolium/crescimento & desenvolvimentoRESUMO
BACKGROUND AND AIMS: Spotted knapweed (Centaurea stoebe s.l., Asteraceae) is native to Europe, where it occurs as a diploid (2xEU) and tetraploid cytotype (4xEU), but so far only the tetraploid has been reported in the introduced range in North America (4xNA). In previous studies, significant range shifts have been found towards drier climates in 4xEU compared with 2xEU, and in 4xNA when compared with the native range. In addition, 4x plants showed thicker leaves and reduced specific leaf area compared with 2x plants, suggesting higher drought tolerance in 4x plants. It is thus hypothesized that the 4x cytotype might be better pre-adapted to drought than the 2x, and the 4xNA better adapted than the 4xEU due to post-introduction selection. METHODS: Plants of the three geocytotypes (2xEU, 4xEU and 4xNA ), each represented by six populations, were subjected to three water treatments over 6 weeks in a greenhouse experiment. Plasticity and reaction norms of above- and below-ground biomasses and their ratio, survival rate, stomatal conductance and carbon isotope discrimination were analysed using linear and generalized linear mixed effect models. KEY RESULTS AND CONCLUSIONS: Above-ground and total biomasses of European tetraploids were slightly less affected by drought than those of European diploids, and 4xEU plants maintained higher levels of stomatal conductance under moderate drought than 4xNA plants, thus supporting the pre-adaptation but not the post-introduction evolution hypothesis. Plasticity indexes for most of the traits were generally higher in 2xEU and 4xNA than in 4xEU plants, but these differences were not or were only marginally significant. Interestingly, the effect of population origin and its interaction with treatment was more important than the effects of geocytotype and range. Population means for the control treatment showed several significant associations either with latitude or some aspect of climatic data, suggesting evolution of local adaptations, especially within the 2xEU and 4xEU geocytotypes.
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Adaptação Fisiológica , Centaurea/fisiologia , Secas , Espécies Introduzidas , Biomassa , Clima , Geografia , Modelos Lineares , Dinâmica Populacional , Análise de Regressão , ÁguaRESUMO
BACKGROUND AND AIMS: In a mixed-ploidy population, strong frequency-dependent mating will lead to the elimination of the less common cytotype, unless prezygotic barriers enhance assortative mating. However, such barriers favouring cytotype coexistence have only rarely been explored. Here, an assessment is made of the mechanisms involved in formation of mixed-ploidy populations and coexistence of diploid plants and their closely related allotetraploid derivates from the Centaurea stoebe complex (Asteraceae). METHODS: An investigation was made of microspatial and microhabitat distribution, life-history and fitness traits, flowering phenology, genetic relatedness of cytotypes and intercytotype gene flow (cpDNA and microsatellites) in six mixed-ploidy populations in Central Europe. KEY RESULTS: Diploids and tetraploids were genetically differentiated, thus corroborating the secondary origin of contact zones. The cytotypes were spatially segregated at all sites studied, with tetraploids colonizing preferentially drier and open microhabitats created by human-induced disturbances. Conversely, they were rare in more natural microsites and microsites with denser vegetation despite their superior persistence ability (polycarpic life cycle). The seed set of tetraploid plants was strongly influenced by their frequency in mixed-ploidy populations. Triploid hybrids originated from bidirectional hybridizations were extremely rare and almost completely sterile, indicating a strong postzygotic barrier between cytotypes. CONCLUSIONS: The findings suggest that tetraploids are later immigrants into already established diploid populations and that anthropogenic activities creating open niches favouring propagule introductions were the major factor shaping the non-random distribution and habitat segregation of cytotypes at fine spatial scale. Establishment and spread of tetraploids was further facilitated by their superior persistence through the perennial life cycle. The results highlight the importance of non-adaptive spatio-temporal processes in explaining microhabitat and microspatial segregation of cytotypes.
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Centaurea/genética , Diploide , Ecossistema , Hibridização Genética , Tetraploidia , Áustria , Evolução Biológica , Fluxo Gênico , Variação Genética , Filogeografia , Dinâmica Populacional , EslováquiaRESUMO
Spotted knapweed (Centaurea stoebe) occurs from Western Asia to Western Europe both as diploid and tetraploid cytotypes, predominantly in single-cytotype populations with higher frequency of diploid populations. Interestingly, only tetraploids have been recorded so far from its introduced range in North America where they became highly invasive. We performed phylogenetic and network analyses of more than 40 accessions of the C. stoebe and C. paniculata groups and other related taxa using cloned internal transcribed spacer (ITS) and sequences of the chloroplast trnT-trnL and atpBrbcL regions to (i) assess the evolutionary origin of tetraploid C. stoebe s.l., and (ii) uncover the phylogeny of the C. stoebe group. Both issues have not been studied so far and thus remained controversial. Cloned ITS sequences showed the presence of two slightly divergent ribotypes occurring in tetraploid cytotype, while only one major ribotype was present in diploid C. stoebe s.str. This pattern suggests an allopolyploid origin of tetraploids with contribution of the diploid C. stoebe s.str. genome. Although we were not able to detect the second parental taxon, we hypothesize that hybridization might have triggered important changes in morphology and life history traits, which in turn may explain the colonization success of the tetraploid taxon. Bayesian relaxed clock estimations indicate a relatively recent--Pleistocene origin of the tetraploid C. stoebe s.l. Furthermore, our analyses showed a deep split between the C. paniculata and C. stoebe groups, and a young diversification of the taxa within the C. stoebe group. In contrast to nrDNA analyses, the observed pattern based on two cpDNA regions was inconclusive with respect to the origin and phylogeny of the studied taxa, most likely due to shared ancient polymorphism and frequent homoplasies.
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Centaurea/genética , DNA de Cloroplastos/genética , DNA Espaçador Ribossômico/genética , Evolução Molecular , Filogenia , Ploidias , Ásia Ocidental , Teorema de Bayes , Centaurea/classificação , Clonagem Molecular , Europa (Continente) , Variação Genética , Hibridização Genética , América do Norte , Ribotipagem , Análise de Sequência de DNARESUMO
BACKGROUND AND AIMS: Pilosella officinarum (syn. Hieracium pilosella) is a highly structured species with respect to the ploidy level, with obvious cytogeographic trends. Previous non-collated data indicated a possible differentiation in the frequency of particular ploidy levels in the Czech Republic and Slovakia. Therefore, detailed sampling and ploidy level analyses were assessed to reveal a boundary of common occurrence of tetraploids on one hand and higher ploids on the other. For a better understanding of cytogeographic differentiation of P. officinarum in central Europe, a search was made for a general cytogeographic pattern in Europe based on published data. METHODS: DNA-ploidy level and/or chromosome number were identified for 1059 plants using flow cytometry and/or chromosome counting on root meristem preparations. Samples were collected from 336 localities in the Czech Republic, Slovakia and north-eastern Hungary. In addition, ploidy levels were determined for plants from 18 localities in Bulgaria, Georgia, Ireland, Italy, Romania and Ukraine. KEY RESULTS: Four ploidy levels were found in the studied area with a contrasting pattern of distribution. The most widespread cytotype in the western part of the Czech Republic is tetraploid (4x) reproducing sexually, while the apomictic pentaploids and mostly apomictic hexaploids (5x and 6x, respectively) clearly prevail in Slovakia and the eastern part of the Czech Republic. The boundary between common occurrence of tetraploids and higher ploids is very obvious and represents the geomorphologic boundary between the Bohemian Massif and the Western Carpathians with the adjacent part of Pannonia. Mixed populations consisting of two different ploidy levels were recorded in nearly 11% of localities. A statistically significant difference in a vertical distribution of penta- and hexaploids was observed in the Western Carpathians and the adjacent Pannonian Plain. Hexaploid populations tend to occur at lower elevations (usually below 500 m), while the pentaploid level is more or less evenly distributed up to 1000 m a.s.l. For the first time the heptaploid level (7x) was found on one site in Slovakia. In Europe, the sexual tetraploid level has clearly a sub-Atlantic character of distribution. The plants of higher ploidy level (penta- and hexa-) with mostly apomictic reproduction prevail in the northern part of Scandinavia and the British Isles, the Alps and the Western Carpathians with the adjacent part of Pannonia. A detailed overview of published data shows that extremely rare records on existence of diploid populations in the south-west Alps are with high probability erroneous and most probably refer to the closely related diploid species P. peleteriana. CONCLUSIONS: The recent distribution of P. officinarum in Europe is complex and probably reflects the climatic changes during the Pleistocene and consequent postglacial migrations. Probably both penta- and hexaploids arose independently in central Europe (Alps and Carpathian Mountains) and in northern Europe (Scandinavia, Great Britain, Ireland), where the apomictic plants colonized deglaciated areas. We suggest that P. officinarum is in fact an amphidiploid species with a basic tetraploid level, which probably originated from hybridizations of diploid taxa from the section Pilosellina.