Although reproductive assurance has been suggested to be one of the most important factors shaping the differential distributional patterns between sexuals and asexuals (geographic parthenogenesis), it has only rarely been studied in natural populations of vascular plants with autonomous apomixis. Moreover, there are almost no data concerning the putative relationship between the level of apomictic versus sexual plant reproduction on one hand, and reproductive assurance on the other. We assessed the level of sexual versus apomictic reproduction in diploid and triploid plants of Hieracium alpinum across its distributional range using flow cytometric analyses of seeds, and compared the level of potential and realized seed set, i.e. reproductive assurance, between the two cytotypes under field and greenhouse conditions. Flow cytometric screening of embryos and endosperms of more than 4,100 seeds showed that diploids produced solely diploid progeny sexually, while triploids produced triploid progeny by obligate apomixis. Potential fruit set was much the same in diploids and triploids from the field and the greenhouse experiment. While in the pollination-limited environment in the greenhouse apomictic triploids had considerably higher realized fruit set than sexual diploids, there was no significant difference between cytotypes under natural conditions. In addition, sexuals varied to a significantly larger extent in realized fruit set than asexuals under both natural and greenhouse conditions. Our results indicate that triploid plants reproduce by obligate apomixis, assuring more stable and predictable fruit reproduction when compared to sexual diploids. This advantage could provide apomictic triploids with a superior colonisation ability, mirrored in a strong geographic parthenogenesis pattern observed in this species.

• MeSH
• apomixie * MeSH
• Asteraceae genetika   fyziologie   MeSH
• diploidie MeSH
• endosperm fyziologie   MeSH
• ovoce růst a vývoj   MeSH
• průtoková cytometrie MeSH
• rozmnožování MeSH
• semena rostlinná růst a vývoj   MeSH
• triploidie * MeSH
• Publikační typ
• časopisecké články MeSH

BACKGROUND AND AIMS: Polyploidy is an important driver of plant diversification and adaptation to novel environments. As a consequence of genome doubling, polyploids often exhibit greater colonizing ability or occupy a wider ecological niche than diploids. Although elevation has been traditionally considered as a key driver structuring ploidy variation, we do not know if environmental and phenotypic differentiation among ploidy cytotypes varies along an elevational gradient. Here, we tested for the consequences of genome duplication on genetic diversity, phenotypic variation and habitat preferences on closely related diploid and tetraploid populations that coexist along approx. 2300 m of varying elevation. METHODS: We sampled and phenotyped 45 natural diploid and tetraploid populations of Arabidopsis arenosa in one mountain range in Central Europe (Western Carpathians) and recorded abiotic and biotic variables at each collection site. We inferred genetic variation, population structure and demographic history in a sub-set of 29 populations genotyped for approx. 36 000 single nucleotide polymorphisms. KEY RESULTS: We found minor effects of polyploidy on colonization of alpine stands and low genetic differentiation between the two cytotypes, mirroring recent divergence of the polyploids from the local diploid lineage and repeated reticulation events among the cytotypes. This pattern was corroborated by the absence of ecological niche differentiation between the two cytotypes and overall phenotypic similarity at a given elevation. CONCLUSIONS: The case of A. arenosa contrasts with previous studies that frequently showed clear niche differentiation between cytotypes. Our work stresses the importance of considering genetic structure and past demographic processes when interpreting the patterns of ploidy distributions, especially in species that underwent recent polyploidization events.

• MeSH
• Arabidopsis * MeSH
• ekosystém MeSH
• lidé MeSH
• ploidie MeSH
• polyploidie MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Evropa MeSH

Polyploidy is one of the major forces of plant evolution and widespread mixed-ploidy species offer an opportunity to evaluate its significance. We therefore selected the cosmopolitan species Urtica dioica (stinging nettle), examined its cytogeography and pattern of absolute genome size, and assessed correlations with bioclimatic and ecogeographic data (latitude, longitude, elevation). We evaluated variation in ploidy level using an extensive dataset of 7012 samples from 1317 populations covering most of the species' distribution area. The widespread tetraploid cytotype (87%) was strongly prevalent over diploids (13%). A subsequent analysis of absolute genome size proved a uniform Cx-value of core U. dioica (except for U. d. subsp. cypria) whereas other closely related species, namely U. bianorii, U. kioviensis and U. simensis, differed significantly. We detected a positive correlation between relative genome size and longitude and latitude in the complete dataset of European populations and a positive correlation between relative genome size and longitude in a reduced dataset of diploid accessions (the complete dataset of diploids excluding U. d. subsp. kurdistanica). In addition, our data indicate an affinity of most diploids to natural and near-natural habitats and that the tetraploid cytotype and a small part of diploids (population from the Po river basin in northern Italy) tend to inhabit synanthropic sites. To sum up, the pattern of ploidy variation revealed by our study is in many aspects unique to the stinging nettle, being most likely first of all driven by the greater ecological plasticity and invasiveness of the tetraploid cytotype.

• MeSH
• biologická evoluce * MeSH
• délka genomu MeSH
• ekosystém MeSH
• fyziologická adaptace genetika   MeSH
• genom rostlinný * MeSH
• karyotypizace MeSH
• ploidie * MeSH
• selekce (genetika) MeSH
• Urtica dioica klasifikace   genetika   MeSH
• zeměpis MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Evropa MeSH
• západní Asie MeSH

BACKGROUND AND AIMS: Polyploidy has played an important role in the evolution of ferns. However, the dearth of data on cytotype diversity, cytotype distribution patterns and ecology in ferns is striking in comparison with angiosperms and prevents an assessment of whether cytotype coexistence and its mechanisms show similar patterns in both plant groups. Here, an attempt to fill this gap was made using the ploidy-variable and widely distributed Cystopteris fragilis complex. METHODS: Flow cytometry was used to assess DNA ploidy level and monoploid genome size (Cx value) of 5518 C. fragilis individuals from 449 populations collected over most of the species' global distributional range, supplemented with data from 405 individuals representing other related species from the complex. Ecological preferences of C. fragilis tetraploids and hexaploids were compared using field-recorded parameters and database-extracted climate data. KEY RESULTS: Altogether, five different ploidy levels (2x, 4x, 5x, 6x, 8x) were detected and three species exhibited intraspecific ploidy-level variation: C. fragilis, C. alpina and C. diaphana. Two predominant C. fragilis cytotypes, tetraploids and hexaploids, co-occur over most of Europe in a diffuse, mosaic-like pattern. Within this contact zone, 40 % of populations were mixed-ploidy and most also contained pentaploid hybrids. Environmental conditions had only a limited effect on the distribution of cytotypes. Differences were found in the Cx value of tetraploids and hexaploids: between-cytotype divergence was higher in uniform-ploidy than in mixed-ploidy populations. CONCLUSIONS: High ploidy-level diversity and widespread cytotype coexistence in the C. fragilis complex match the well-documented patterns in some angiosperms. While ploidy coexistence in C. fragilis is not driven by environmental factors, it could be facilitated by the perennial life-form of the species, its reproductive modes and efficient wind dispersal of spores. Independent origins of hexaploids and/or inter-ploidy gene flow may be expected in mixed-ploidy populations according to Cx value comparisons.

• MeSH
• ekologie MeSH
• hybridizace genetická MeSH
• kapradiny * MeSH
• lidé MeSH
• ploidie MeSH
• polyploidie MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Evropa MeSH

Polyploidisation has played an important role in plant diversification, and variation in ploidy level may be found not only between species of the same genus, but also within a single species. Although establishing the adaptive significance of polyploidy to explain the geographic distribution of cytotypes is challenging, the occurrence of different cytotypes in different ecological niches may suggest an adaptive role of genome duplication. We studied the adaptive significance of the geographic distribution of cytotypes across the entire distribution range of the endemic Erysimum mediohispanicum (Brassicaceae). For that, we have used climate variables, population elevation and soil properties to model ecological niches for the different cytotypes. In addition, we analysed the effect that ploidy level has on the floral phenotype. We found a clear geographic pattern in the distribution of cytotypes, with diploid individuals occurring in the southernmost part of the distribution range, while tetraploids were found in the northern area. A contact (mosaic) zone between both cytotypes was identified, but diploids and tetraploids occur in sympatry in only one population (although in a highly unbalanced proportion). Gene flow between different cytotypes seems to be negligible, as evident from an almost complete absence of triploids and other minority cytotypes. Niches occupied by both cytotypes showed subtle, but significant differences, even in the contact zone. Precipitation was higher in regions occupied by tetraploid individuals, which present wider corolla tubes and thinner but taller stalks than diploids. Our findings highlight the potential role of polyploidy in the ecological adaptation of E. mediohispanicum to both abiotic factors and biotic interactions.

• MeSH
• biologická evoluce MeSH
• ekosystém * MeSH
• Erysimum genetika   MeSH
• nadmořská výška MeSH
• podnebí MeSH
• polyploidie MeSH
• půda MeSH
• tetraploidie MeSH
• tok genů MeSH
• zeměpis MeSH
• Publikační typ
• časopisecké články MeSH

We present the karyotype characteristics of five cytotypes of mole rats (Nannospalax) with 56 chromosomes revealed by the C-banding and AgNOR staining analyses. We attempt to investigate if the specific distinction between the populations from Thrace (N. leucodon) and Anatolia (N. xanthodon) is reflected also in their karyotypic differentiation. The specimens from each of the five populations studied revealed a distinct karyotype which was different from those found in other populations. The fundamental number of autosomal arms varied from 68 to 72. The amount of C-heterochromatin was larger in the Thrace sample of N. leucodon compared to the Anatolian population of N. xanthodon. The active NOR sites were recorded on five autosomal pairs in N. leucodon, whereas only three or four pairs bearing NOR were observed in N. xanthodon. Differences between the studied populations were quantified in the analysis of the distribution pattern of the C-positive bands and the AgNOR sites in individual chromosomes which indicated a basal position of the Thrace sample of N. leucodon and its divergence from other studied populations. The karyotypes of the 56-chromosome populations of N. leucodon and N. xanthodon are thus distinctly different.

• MeSH
• druhová specificita MeSH
• karyotyp * MeSH
• mikroftalmičtí podzemní hlodavci MeSH
• pruhování chromozomů * MeSH
• savčí chromozomy genetika   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH
• Geografické názvy
• Turecko MeSH

BACKGROUND AND AIMS: Genome duplication is widely acknowledged as a major force in the evolution of angiosperms, although the incidence of polyploidy in different floras may differ dramatically. The Greater Cape Floristic Region of southern Africa is one of the world's biodiversity hotspots and is considered depauperate in polyploids. To test this assumption, ploidy variation was assessed in a widespread member of the largest geophytic genus in the Cape flora: Oxalis obtusa. METHODS: DNA flow cytometry complemented by confirmatory chromosome counts was used to determine ploidy levels in 355 populations of O. obtusa (1014 individuals) across its entire distribution range. Ecological differentiation among cytotypes was tested by comparing sets of vegetation and climatic variables extracted for each locality. KEY RESULTS: Three majority (2x, 4x, 6x) and three minority (3x, 5x, 8x) cytotypes were detected in situ, in addition to a heptaploid individual originating from a botanical garden. While single-cytotype populations predominate, 12 mixed-ploidy populations were also found. The overall pattern of ploidy level distribution is quite complex, but some ecological segregation was observed. Hexaploids are the most common cytotype and prevail in the Fynbos biome. In contrast, tetraploids dominate in the Succulent Karoo biome. Precipitation parameters were identified as the most important climatic variables associated with cytotype distribution. CONCLUSIONS: Although it would be premature to make generalizations regarding the role of genome duplication in the genesis of hyperdiversity of the Cape flora, the substantial and unexpected ploidy diversity in Oxalis obtusa is unparalleled in comparison with any other cytologically known native Cape plant species. The results suggest that ploidy variation in the Greater Cape Floristic Region may be much greater than currently assumed, which, given the documented role of polyploidy in speciation, has direct implications for radiation hypotheses in this biodiversity hotspot.

• MeSH
• biodiverzita MeSH
• chromozomy rostlin MeSH
• genetická variace * MeSH
• Magnoliopsida cytologie   genetika   MeSH
• ploidie * MeSH
• populační genetika MeSH
• průtoková cytometrie metody   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• jižní Afrika MeSH

The potential for gene exchange across ploidy levels has long been recognized, but only a few studies have explored the rate of gene flow among different cytotypes. In addition, most of the existing knowledge comes from contact zones between diploids and tetraploids. The purpose of this paper was to investigate relationships between diploid and hexaploid individuals within the Aster amellus aggregate. A. amellus is known to occur in diploid and hexaploid cytotypes in Europe, with a complex contact zone in central Europe. Patterns of genetic diversity were investigated using seven microsatellite loci at three different spatial scales: (1) in the single known mixed-ploidy population; (2) in populations at the contact zone and (3) in a wider range of populations across Europe. The results show clear separation of the cytotypes at all three spatial scales. In addition, analysis of molecular variance strongly supported a model predicting a single origin of the hexaploids, with no or very limited gene flow between the cytotypes. Some hexaploid individuals found in the mixed-ploidy population, however, fell into the diploid cluster. This could suggest recurrent polyploid formation or occasional cross-pollination between cytotypes; however, there are strong post-zygotic breeding barriers between the two cytotypes, making the latter less plausible. Overall, the results suggest that the cytotypes could represent two cryptic species. Nevertheless, their formal separation is difficult as they cannot be distinguished morphologically, occupy very similar habitat conditions and have largely overlapping distribution ranges. These results show that polyploid complexes must be treated with caution as they can hide biological diversity and can have different adaptation potentials, evolving independently.

• MeSH
• analýza hlavních komponent MeSH
• Aster genetika   MeSH
• Bayesova věta MeSH
• diploidie * MeSH
• fylogeografie MeSH
• genetická variace MeSH
• mikrosatelitní repetice MeSH
• modely genetické MeSH
• polyploidie * MeSH
• rostlinné geny MeSH
• tok genů * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Evropa MeSH

BACKGROUND AND AIMS: One of the prerequisites for polyploid research in natural systems is knowledge of the geographical distribution of cytotypes. Here inter- and intrapopulational ploidy diversity was examined in the Gymnadenia conopsea aggregate in central Europe and potential explanations and evolutionary consequences of the observed spatial patterns investigated. METHODS: DAPI flow cytometry supplemented by confirmatory chromosome counts was used to determine ploidy in 3581 samples of the G. conopsea aggregate from 43 populations. The fine-scale spatial pattern of cytotype distribution (intra- and interploidy associations) was analysed with univariate and bivariate K-functions. KEY RESULTS: Gymnadenia tissues undergo a progressively partial endoreplication, which accounts for about 60 % and 75 % of the total genome in G. conopsea and G. densiflora, respectively. Flow cytometric profiles are therefore species-specific and can be used as a marker for rapid and reliable species recognition. Two majority (4x, 8x) and three minority (6x, 10x, 12x) cytotypes were found, often in mixed-ploidy populations (harbouring up to all five different ploidy levels). The scarcity of the minority cytotypes (about 2·7 %) suggests the existence of strong pre- or postzygotic mating barriers. Spatial structure was observed in plots of populations with the highest cytotype variation, including clumping of individuals of the same ploidy and negative association between tetra- and octoploids. CONCLUSIONS: The remarkable ploidy coexistence in the G. conopsea aggregate has reshaped our perception of intrapopulational ploidy diversity under natural conditions. This system offers unique opportunities for studying processes governing the formation and establishment of polyploids and assessing the evolutionary significance of the various pre- and postzygotic mating barriers that maintain this ploidy mixture.

• MeSH
• chromozomy rostlin MeSH
• DNA rostlinná genetika   MeSH
• genetická variace MeSH
• genom rostlinný MeSH
• Orchidaceae klasifikace   genetika   MeSH
• polyploidie MeSH
• průtoková cytometrie MeSH
• tetraploidie MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Česká republika MeSH
• Slovenská republika MeSH

BACKGROUND AND AIMS: A detailed knowledge of cytotype distribution can provide important insights into the evolutionary history of polyploid systems. This study aims to explore the spatial distribution of different cytotypes in Pilosella echioides at various spatial scales (from the whole distributional range to the population level) and to outline possible evolutionary scenarios for the observed geographic pattern. METHODS: DNA-ploidy levels were estimated using DAPI flow cytometry in 4410 individuals of P. echioides from 46 populations spread over the entire distribution range in central Europe. Special attention was paid to the cytotype structure in the most ploidy-diverse population in south-west Moravia. KEY RESULTS: Five different cytotypes (2x, 3x, 4x, 5x and 6x) were found, the last being recorded for the first time. Although ploidy-uniform (di- or tetraploid) sites clearly prevailed, nearly one-quarter of the populations investigated harboured more (up to all five) cytotypes. Whereas penta- and hexaploids constituted only a minority of the samples, a striking predominance of the triploid cytotype was observed in several populations. CONCLUSIONS: The representative sampling confirmed previous data on cytotype distribution, i.e. the spatial aggregation of mixed-ploidy populations in south-west Moravia and Lower Austria and the predominance of ploidy-uniform populations in other parts of the area investigated. Recurrent origin of polyploids from diploid progenitors via unreduced gametes and their successful establishment are considered the key factors promoting intrapopulational ploidy mixture ('primary hybrid zones'). As an alternative to the generally accepted theory of cytotype co-existence based on the development of different means of inter-ploidy reproductive isolation, it is suggested that a long-term ploidy mixture can also be maintained in free-mating populations provided that the polyploids originate with a sufficient frequency. In addition, the prevalence (or subdominance) of the triploid cytotype in several mixed-ploidy populations represents the first evidence of such a phenomenon in plant systems with exclusively sexual reproduction.

• MeSH
• Asteraceae genetika   fyziologie   MeSH
• biologická evoluce MeSH
• chromozomy rostlin genetika   MeSH
• DNA rostlinná genetika   MeSH
• fylogeografie MeSH
• genetická variace MeSH
• ploidie MeSH
• průtoková cytometrie MeSH
• rozmnožování MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Evropa MeSH