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Dive into the research topics where Jana Krejčíková is active.

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Featured researches published by Jana Krejčíková.


Molecular Ecology | 2012

Extensive range persistence in peripheral and interior refugia characterizes Pleistocene range dynamics in a widespread Alpine plant species (Senecio carniolicus, Asteraceae)

Pedro Escobar García; Manuela Winkler; Ruth Flatscher; Michaela Sonnleitner; Jana Krejčíková; Jan Suda; Karl Hülber; Gerald M. Schneeweiss; Peter Schönswetter

Recent evidence suggests that survival of arctic‐alpine organisms in peripheral or interior glacial refugia are not mutually exclusive and may both be involved in shaping an organism’s Pleistocene history, yet potentially at different time levels. Here, we test this hypothesis in a high‐mountain plant (diploid lineage of Senecio carniolicus, Asteraceae) from the Eastern European Alps, in which patterns of morphological variation and current habitat requirements suggest survival in both types of refugia. To this end, we used AFLPs, nuclear and plastid DNA sequences and analysed them, among others, within a graph theoretic framework and using novel Bayesian methods of phylogeographic inference. On the basis of patterns of genetic diversity, occurrence of rare markers, distribution of distinct genetic lineages and patterns of range connectivity both interior refugia in the formerly strongly glaciated central Alps and peripheral refugia along the southern margin of the Alps were identified. The presence of refugia congruently inferred by markers resolving at different time levels suggests that these refugia acted as such throughout several glacial cycles. The high degree of range persistence together with gradual range expansion, which contrasts with the extent of range shifts implied for other Alpine species, is likely responsible for incipient lineage differentiation evident from the genetic data. Replacing a simplistic peripheral vs. interior refugia dualism by more complex models involving both types of refugia and considering different time levels will help identifying common phylogeographic patterns with respect to, for instance, location of refugia and colonization routes and elucidating their underlying genetic and/or ecological causes.


Annals of Botany | 2013

High ploidy diversity and distinct patterns of cytotype distribution in a widespread species of Oxalis in the Greater Cape Floristic Region

Jana Krejčíková; Radka Sudová; Magdalena Lučanová; Pavel M. Travnicek; Tomáš Urfus; Petr Vít; Hanna Weiss-Schneeweiss; Bożena Kolano; Kenneth C. Oberlander; L.L. Dreyer; Jan Suda

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 worlds 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.


PLOS ONE | 2013

Parental Ploidy Strongly Affects Offspring Fitness in Heteroploid Crosses among Three Cytotypes of Autopolyploid Jacobaea carniolica (Asteraceae)

Michaela Sonnleitner; Birgit Weis; Ruth Flatscher; Pedro Escobar García; Jan Suda; Jana Krejčíková; Gerald M. Schneeweiss; Manuela Winkler; Peter Schönswetter; Karl Hülber

Reproductive interactions among cytotypes in their contact zones determine whether these cytotypes can co-exist and form stable contact zones or not. In autopolyploids, heteroploid cross-compatibilities might depend on parental ploidy, but tests of this hypothesis in autopolyploid systems with more than two ploidies are lacking. Here, we study Jacobaea carniolica, which comprises diploid, tetraploid, and hexaploid individuals regularly forming contact zones. Seeds obtained from in situ cross-pollinations within and among cytotypes were subjected to DNA flow cytometry and greenhouse germination experiments. Hybrid fitness and parental effects on hybrid fitness were tested with regression models comparing fitness parameters of early life stages. Irrespective of the direction of crosses, seed viability and seedling survival in diploid-polyploid crosses were substantially lower than in tetraploid-hexaploid crosses. In contrast, seedling growth traits indicated neither transgressive character expression nor any selection against hybrid offspring. Congruent with a model of genome dosage effects, these traits differed between reciprocal crosses, especially of diploids and tetraploids, where trait values resembled those of the maternal parent. The strong effect of parental ploidy on offspring fitness in heteroploid crosses may cause contact zones involving exclusively polyploid cytotypes to be less stable over longer terms than those involving diploids and polyploids.


Ecology and Evolution | 2015

Ecological differentiation, lack of hybrids involving diploids, and asymmetric gene flow between polyploids in narrow contact zones of Senecio carniolicus (syn. Jacobaea carniolica, Asteraceae).

Karl Hülber; Michaela Sonnleitner; Jan Suda; Jana Krejčíková; Peter Schönswetter; Gerald M. Schneeweiss; Manuela Winkler

Areas of immediate contact of different cytotypes offer a unique opportunity to study evolutionary dynamics within heteroploid species and to assess isolation mechanisms governing coexistence of cytotypes of different ploidy. The degree of reproductive isolation of cytotypes, that is, the frequency of heteroploid crosses and subsequent formation of viable and (partly) fertile hybrids, plays a crucial role for the long-term integrity of lineages in contact zones. Here, we assessed fine-scale distribution, spatial clustering, and ecological niches as well as patterns of gene flow in parental and hybrid cytotypes in zones of immediate contact of di-, tetra-, and hexaploid Senecio carniolicus (Asteraceae) in the Eastern Alps. Cytotypes were spatially separated also at the investigated microscale; the strongest spatial separation was observed for the fully interfertile tetra- and hexaploids. The three main cytotypes showed highly significant niche differences, which were, however, weaker than across their entire distribution ranges in the Eastern Alps. Individuals with intermediate ploidy levels were found neither in the diploid/tetraploid nor in the diploid/hexaploid contact zones indicating strong reproductive barriers. In contrast, pentaploid individuals were frequent in the tetraploid/hexaploid contact zone, albeit limited to a narrow strip in the immediate contact zone of their parental cytotypes. AFLP fingerprinting data revealed introgressive gene flow mediated by pentaploid hybrids from tetra- to hexaploid individuals, but not vice versa. The ecological niche of pentaploids differed significantly from that of tetraploids but not from hexaploids.


Biological Invasions | 2013

Cytogeography of Oxalis pes-caprae in its native range: where are the pentaploids?

Jana Krejčíková; Radka Sudová; Kenneth C. Oberlander; L.L. Dreyer; Jan Suda

Due to its instantaneous effects on the genetics, phenotype, physiology and/or ecology of a plant, polyploidy can play an important role in facilitating plant invasions. Understanding the determinants of invasiveness in species with multiple ploidy levels requires a detailed knowledge of ploidy composition in native versus invaded ranges. Using DNA flow cytometry, we performed representative ploidy screening (277 localities, 333 individuals) across the native range of Oxalis pes-caprae and compared the data with those from invaded ranges. Both ranges showed striking differences in ploidy composition: whereas tetra- and especially pentaploids successfully colonized secondary areas, only di-, (very rare) tri- and tetraploids (dominant) were found in the native range of this species. Disregarding the diploid var. sericea, diploids and tetraploids of the nominate variety showed largely parapatric distribution in the native range, with a zone of overlap in the Northern Cape Province. Our results challenge the conventional scenario of the introduction of pentaploid individuals from the Greater Cape Floristic Region. The origin of the pentaploid cytotype is unclear and molecular tools applied in a large scale screening are needed to understand the invasion history of the species.


PLOS ONE | 2015

Evolutionary and Taxonomic Implications of Variation in Nuclear Genome Size: Lesson from the Grass Genus Anthoxanthum (Poaceae)

Zuzana Chumová; Jana Krejčíková; Terezie Mandáková; Jan Suda; Pavel M. Travnicek

The genus Anthoxanthum (sweet vernal grass, Poaceae) represents a taxonomically intricate polyploid complex with large phenotypic variation and its evolutionary relationships still poorly resolved. In order to get insight into the geographic distribution of ploidy levels and assess the taxonomic value of genome size data, we determined C- and Cx-values in 628 plants representing all currently recognized European species collected from 197 populations in 29 European countries. The flow cytometric estimates were supplemented by conventional chromosome counts. In addition to diploids, we found two low (rare 3x and common 4x) and one high (~16x–18x) polyploid levels. Mean holoploid genome sizes ranged from 5.52 pg in diploid A. alpinum to 44.75 pg in highly polyploid A. amarum, while the size of monoploid genomes ranged from 2.75 pg in tetraploid A. alpinum to 9.19 pg in diploid A. gracile. In contrast to Central and Northern Europe, which harboured only limited cytological variation, a much more complex pattern of genome sizes was revealed in the Mediterranean, particularly in Corsica. Eight taxonomic groups that partly corresponded to traditionally recognized species were delimited based on genome size values and phenotypic variation. Whereas our data supported the merger of A. aristatum and A. ovatum, eastern Mediterranean populations traditionally referred to as diploid A. odoratum were shown to be cytologically distinct, and may represent a new taxon. Autopolyploid origin was suggested for 4x A. alpinum. In contrast, 4x A. odoratum seems to be an allopolyploid, based on the amounts of nuclear DNA. Intraspecific variation in genome size was observed in all recognized species, the most striking example being the A. aristatum/ovatum complex. Altogether, our study showed that genome size can be a useful taxonomic marker in Anthoxathum to not only guide taxonomic decisions but also help resolve evolutionary relationships in this challenging grass genus.


BMC Evolutionary Biology | 2017

Cytotype coexistence in the field cannot be explained by inter-cytotype hybridization alone: linking experiments and computer simulations in the sexual species Pilosella echioides (Asteraceae)

Jindřich Chrtek; Tomáš Herben; Radka Rosenbaumová; Zuzana Münzbergová; Zuzana Dočkalová; Jaroslav Zahradníček; Jana Krejčíková; Pavel M. Travnicek

BackgroundProcesses driving ploidal diversity at the population level are virtually unknown. Their identification should use a combination of large-scale screening of ploidy levels in the field, pairwise crossing experiments and mathematical modelling linking these two types of data. We applied this approach to determine the drivers of frequencies of coexisting cytotypes in mixed-ploidy field populations of the fully sexual plant species Pilosella echioides. We examined fecundity and ploidal diversity in seeds from all possible pairwise crosses among 2x, 3x and 4x plants. Using these data, we simulated the dynamics of theoretical panmictic populations of individuals whose progeny structure is identical to that determined by the hybridization experiment.ResultsThe seed set differed significantly between the crossing treatments, being highest in crosses between diploids and tetraploids and lowest in triploid-triploid crosses. The number of progeny classes (with respect to embryo and endosperm ploidy) ranged from three in the 2x-2x cross to eleven in the 3x-3x cross. Our simulations demonstrate that, provided there is no difference in clonal growth and/or survival between cytotypes, it is a clear case of minority cytotype exclusion depending on the initial conditions with two stable states, neither of which corresponds to the ploidal structure in the field: (i) with prevalent diploids and lower proportions of other ploidies, and (ii) with prevalent tetraploids and 9% of hexaploids. By contrast, if clonal growth differs between cytotypes, minority cytotype exclusion occurs only if the role of sexual reproduction is high; otherwise differences in clonal growth are sufficient to maintain triploid prevalence (as observed in the field) independently of initial conditions.ConclusionsThe projections of our model suggest that the ploidal structure observed in the field can only be reached via a relatively high capacity for clonal growth (and proportionally lower sexual reproduction) in all cytotypes combined with higher clonal growth in the prevailing cytotype (3x).


Botanical Journal of the Linnean Society | 2013

Genome size variation in Orchidaceae subfamily Apostasioideae: filling the phylogenetic gap

Jana Jersáková; Pavel M. Travnicek; Barbora Kubátová; Jana Krejčíková; Tomáš Urfus; Zhong-Jian Liu; Anthony Lamb; Jan Ponert; Katharina Schulte; Vladislav Čurn; Jan Vrána; Ilia J. Leitch; Jan Suda


South African Journal of Botany | 2013

The spatio-ecological segregation of different cytotypes of Oxalis obtusa (Oxalidaceae) in contact zones

Jana Krejčíková; Radka Sudová; Kenneth C. Oberlander; L.L. Dreyer; Jan Suda


Phytotaxa | 2013

Two new species of Oxalis (Oxalidaceae) from the Greater Cape Floristic Region

Jan Suda; Jana Krejčíková; Radka Sudová; Kenneth C. Oberlander; L.L. Dreyer

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Jan Suda

Charles University in Prague

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Radka Sudová

Academy of Sciences of the Czech Republic

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L.L. Dreyer

Stellenbosch University

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Tomáš Urfus

Charles University in Prague

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