Polyploidie (přítomnost více než dvou kompletních sad chromozómů) je důležitou silou (hybatelem) v evoluci krytosemenných rostlin. Současná molekulární data ukazují, že všechny krytosemenné rostliny, až na rod Amborella, prošly během své evoluce jednou nebo více duplikacemi celého genomu .Tyto děje byly rozhodující pro vznik mnoha důležitých vývojových a řídících genů, a pravděpodobně byly spouštěcím mechanismem (odrazovým můstkem) ekologické dominance krytosemenných během křídového období. and Polyploidy (the presence of more than two complete chromosome sets) is an important force in angiosperm evolution. Recent molecular data have shown that all angiosperms, with the exception of the Amborella genus, underwent one or more whole-genome duplications in their evolutionary history. These events were crucial for the creation of many important developmental and regulatory genes and perhaps also triggered a mechanism resulting in the ecological dominance of angiosperms during the Cretaceous.
The formation and maintenance of polyploids (via the development of various reproductive barriers) rank among the central questions of studies on polyploid evolution. However, the long time scale of most evolutionary processes makes the study of the dynamics of diploid-polyploid groups difficult. A suitable candidate for a targeted comparative study is Vicia cracca (Fabaceae), which in the late 1960s was subjected to a detailed cytotype screening in Central Europe. Re-sampling the original localities offers a unique opportunity to assess changes in the ploidy structure of the populations, which should reflect the cumulative effect of all the evolutionary forces acting on the plants. Using flow cytometry, the DNA ploidy levels of more than 6,500 individuals of V. cracca collected at 257 localities in Austria, the Czech Republic, Germany and the Slovak Republic were estimated. Three different cytotypes (2x, 3x and 4x) were detected. While tetraploids predominated in the western part of the area investigated (179 populations), the diploids had a more easterly distribution (62 populations). There is a secondary zone of cytotype contact near the boundary between the Czech and Slovak Republics. Sixteen populations (~6%) consisted of a mixture of 2x and 4x cytotypes. Triploids are very rare; only seven individuals were found in two otherwise diploid populations, indicating the existence of breeding barriers between diploids and tetraploids. The distribution of cytotypes is similar to that determined four decades ago using chromosome counts. Nevertheless, there are some discrepancies, namely the current absence of: (i) the diploid cytotype in southern Bohemia and (ii) the altitudinal segregation in the distribution of cytotypes, including two formerly recognized chromosomal races of diploids, perhaps a result of more representative sampling. Identical monoploid genome sizes (1Cx-values) of both the majority ploidy levels support an autopolyploid origin of the tetraploids.
In order to uncover patterns and processes of segregation of co-existing cytotypes, we investigated a zone in the eastern Alps (Austria) where diploid and hexaploid individuals of the alpine herb Senecio carniolicus Willd. (Asteraceae) co-occur. Linking the fine-scale distribution of cytotypes to environmental and spatial factors revealed segregation along an ecological gradient, which was also reflected in the cytotype-associated plant assemblages. Compared to diploids, hexaploids are found in more species-rich and denser communities. This may be due to their better competitive ability and lower tolerance of abiotic stress compared to the diploids. The lack of any intermediate cytotypes suggests the presence of strong reproductive isolation mechanisms, whose nature is, however, elusive.
DAPI and propidium iodide flow cytometry were used to determine the variation in genome size in 166 samples and of all taxa and ploidy levels of Fallopia section Reynoutria (knotweeds) recorded in the Czech Republic. Significant differences were detected in the amount of nuclear DNA, associated with the ploidy levels and taxonomic identity of the material. At each ploidy level, F. sachalinensis showed the lowest and F. japonica the highest fluorescence intensities. The fluorescence values for the hybridogenous F. ×bohemica were located in-between these two levels. In most cases, there was at least a four-percent gap in fluorescence values between the nearest neighbours belonging to a different taxon. Intraspecific variation in genome size was very low in all taxa except hexaploid F. ×bohemica; this could be due to the complex evolutionary history of this taxon. Our results indicate that the amount of nuclear DNA can be used as a reliable marker for the identification of homoploid knotweed species and their hybrids. Different evolutionary pathways for the origin of high polyploids and/or hybridogenous taxa are proposed based on genome size.
Variation in genome size in a particular taxonomic group can reflect different evolutionary processes including polyploidy, hybridization and natural selection but also neutral evolution. Using flow cytometry, karyology, ITS sequencing and field surveys, the causes of variation in genome size in the ecologically and morphologically diverse high-Andean genus Lasiocephalus (Asteraceae, Senecioneae) were examined. There was a 1.64-fold variation in holoploid genome size (C-values) among 189 samples belonging to 20 taxa. The most distinct was a group of plants with large genomes corresponding to DNA triploids. Disregarding the DNA triploids, the remaining samples exhibited a pronounced (up to 1.32-fold) and rather continuous variation. Plants with the smallest genomes most likely represent intergeneric hybrids with the closely related and sympatric Culcitium nivale, which has a smaller genome than Lasiocephalus. The variation in genome size in samples of diploid Lasiocephalus was strongly correlated with several environmental and life history traits (altitude, habitat and growth form). However, all these factors, as well as genome size itself, were correlated with phylogeny (main split into the so-called ‘forest’ and ‘páramo’ clades), which most probably represents the true cause of the differentiation in intrageneric genome size. In contrast, relationships between genome size and phylogeny were not apparent at lower divergence levels. Instead, here we suggest that ecological conditions have played a role in driving shifts in genome size between closely related species inhabiting different environments. Collectively, this study demonstrates that various evolutionary forces and processes have shaped the variation in genome size and indicates that there is a need for multi-approach analyses when searching for the causes and consequences of changes in genome size.
Koniklece (rod Pulsatilla) patří mezi nápadné, časně zjara kvetoucí rostliny otevřených stanovišť. V naší květeně se vyskytuje pět původních druhů, všechny jsou však vzácné a mizejí, a proto figurují mezi zvláště chráněnými rostlinami. Hlavní příčinu jejich ústupu lze spatřovat v sukcesních změnách na stanovištích (především zarůstání) v důsledku upuštění od tradičních forem obhospodařování. Na příhodných lokalitách, na nichž mohou růst pohromadě různé druhy konikleců, přistupuje další riziko a tím je mezidruhové křížení. Nebezpečí hybridizace spočívá zejména v jejím často obtížném odhalení, které se neobejde bez použití moderních botanických technik. Ty se ukázaly být velice užitečné i při studiu našeho nejčastěji udávaného hybridního taxonu – koniklece Hackelova. and The genus Pulsatilla (pasque flower) contains about 30 species distributed mainly in the mountains of the northern hemisphere. Several species can grow in sympatry and be involved in interspecific hybridization. High phenotypic variation of parental taxa, however, precludes unambiguous hybrid determination. Genome size was found to be a~reliable species-specific marker which can elucidate patterns and processes in mixed populations.
Genome size has been suggested as one of the traits associated with invasiveness of plant species. To provide a quantitative insight into the role of this trait, we estimated nuclearDNAcontent in 93 alien species naturalized in the Czech Republic, belonging to 32 families, by using flow cytometry, and compared it with the values reported for non-invading congeneric and confamilial species from the Plant DNA C-values database. Species naturalized in the Czech Republic have significantly smaller genomes than their congeners not known to be naturalized or invasive in any part of the world. This trend is supported at the family level: alien species naturalized in the Czech flora have on average a smaller genome than is the mean value for non-invading confamilials. Moreover, naturalized and non-invading species clearly differed in the frequency of five genome size categories; this difference was mainly due to very small genomes prevailing and intermediate to very large genomes underrepresented in the former group. Our results provide the first quantitative support for association of genome size with invasiveness, based on a large set of alien species across a number of plant families. However, there was no difference in the genome size of invasive species compared to naturalized but non-invasive. This suggests that small genome size provides alien plants with an advantage already at the stage of naturalization and need not be necessarily associated with the final stage of the process, i.e. invasion.
Hvozdík písečný český (Dianthus arenarius ssp. bohemicus) patří mezi endemické a kriticky ohrožené druhy české flóry. Vyskytuje se pouze na písčitých půdách nedaleko obce Kleneč ve středních Čechách. Záchranný program se v posledním desetiletí zaměřoval hlavně na zvýšení početnosti na jediné známé lokalitě (včetně např. výsevů). Riziko mezidruhového křížení se sympatricky rostoucím hvozdíkem D. carthusianorum bylo prověřováno průtokovou cytometrií. Prokázáno bylo pouze několik případů kříženců, které lze poměrně dobře rozeznat podle několika intermediátních znaků na vegetativních částech rostlin i na květech (např. zbarvení). and Dianthus arenarius ssp. bohemicus ranks among the endemic and critically endangered species of Czech flora. It is restricted to sandy soil near the village of Kleneč in Central Bohemia. Conservation carried out during the last decade at the only known locality led to an increase in the number of individuals (incl. seedlings). The risk of interspecific hybridization with sympatric D. carthusianorum was assessed using flow cytometry. Only a few primary crosses were detected that showed intermediate values of several vegetative and generative characters (petal colour and fringe depth in particular).