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Hybridization and polyploidization as significant evolutional aspects in the tribe Triticeae
Urfusová, Romana ; Mahelka, Václav (advisor) ; Escudero, Marcial (referee) ; Štech, Milan (referee)
Hybridization and polyploidization, two vastly important evolutionary mechanisms, have been well studied experimentally within the Triticeae, but the specific consequences of both phenomena under natural conditions remain poorly defined. This is due to the variability of natural populations, whether in species composition, genetic and cytogenetic diversity, abiotic conditions, or their interaction. Each population is thus unique in its own way, with specific parameters of hybridization, polyploidization or reproductive mode. The latter mechanism is both influenced by and influences the former. For example, it is known that self-incompatibility can be broken by the presence of foreign pollen (a phenomenon known as the mentor effect). To study these processes, I chose Central European species of the genus Elymus: E. hispidus, E. repens, and marginally also E. caninus. All three species are allopolyploid. Whereas E. hispidus and E. repens are predominantly allohexaploid, E. caninus is allotetraploid. The former two have been found to hybridize and produce higher polyploid cytotypes. The role of E. caninus has not yet been studied. Methodologically, I have used flow cytometry (analysis of absolute and relative genome size), morphometrics, experimental hybridization, cytology (chromosome counting) and...
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Morphological and ecological differentiation and distribution of taxa in the Galium mollugo group
Talpová, Julie ; Kaplan, Zdeněk (advisor) ; Štech, Milan (referee)
My thesis deals with three taxa of the polyploid complex Galium mollugo that occur in the Czech Republic. These are diploid G. mollugo and tetraploid G. album subsp. album and G. album subsp. pycnotrichum. These taxa are very similar to each other, their identification is difficult and exact values of the quantitative characters used for their separation are unknown. To date, there has been no study based on flow cytometry (FCM) and classical morphometrics analysis in this complex. By using them I wanted to bring new results and fill the gaps in scientific research. Primarily, I was investigating whether the individual cytotypes can be distinguished based on different genome size using FCM analyses. Another aim was to determine whether it is possible to define morphological and ecological differences between diploid and tetraploid taxa. The morphometrics included ordination and discrimination methods. I observed whether taxa could be distinguished by the naked eye and determined by measurement which characters are most suitable for identification. FCM analyses proved to be suitable to distinguish the two ploidy levels. I have been able to demonstrate by statistical methods that diploid and tetraploid taxa differ from each other, and I have also refined the characters that are most suitable for...
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Population structure and evolutionary history of Central European bellflowers from the Campanula rotundifolia agg.
Šemberová, Kristýna ; Schmickl, Roswitha Elisabeth (advisor) ; Tribsch, Andreas (referee) ; Štech, Milan (referee)
6 Abstract For understanding extant species diversity, knowledge about processes acting at the population level is crucial. Besides mutations generating de novo genetic variation, three major processes, i.e., polyploidy, hybridization and local adaptation, notably impact population structure and cause evolutionary novelty. Campanula rotundifolia agg. was chosen as a model group for the joint study of these processes because it represents a polyploid complex with three major cytotypes (2x, 4x, 6x), a hitherto unknown ability to hybridize, and a pleiad of putative species that have undergone local adaptation to different conditions. In particular, polyploidization in the complex is acknowledged for generating morphological variation, facilitating long-distance dispersal and shifts in the environmental niche. It also creates a reproductive barrier, thus enabling sympatric speciation. Prerequisites for local adaptation are morphological variation and strong selection pressures leading to adaptive divergence and the rise of many endemic taxa, mainly at the extremes of environmental gradients. On the other hand, for locally adapted or endemic taxa, hybridization with a widespread taxon is one of the main existential threats. Here, I focused on C. rotundifolia agg. populations in Central Europe its hypothetical...
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Evolutionary processes responsible for complexity in aquatic vascular plants
Prančl, Jan ; Kaplan, Zdeněk (advisor) ; Oberprieler, Christoph (referee) ; Štech, Milan (referee)
Aquatic plants are a heterogeneous assemblage of species that, although surviving in similar habitats, have evolved from very different genetic and ecological backgrounds. However, many aquatics share a number of anatomical, morphological, metabolic and reproductive adaptations, which have arisen independently in remarkable similarities (through convergence and parallelisms) in many unrelated groups. Despite their evolutionary uniqueness, aquatic plants are markedly underrepresented in contemporary biosystematic studies. Moreover, the taxonomic evaluation of numerous aquatic plant groups is intricate due to the strong morphological reduction and a high degree of phenotypic plasticity. This thesis focuses on two notoriously challenging aquatic plant groups, Callitriche and Ranunculus sect. Batrachium. The combination of several approaches (genome size estimation, chromosome counting, sequencing of nrDNA ITS and plastid trnT-trnL regions, examination of herbarium collections) was applied in order to improve our knowledge on principal evolutionary processes such as hybridization, polyploidization and cryptic variation and demonstrate their role on the shaping of overall aquatic plant diversity. The distribution of particular species in the Czech Republic was mapped for the first time. For both groups,...
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Influence of climatic fluctuations in Neogene/on evolution of ecologically diverse plant genus: an example of Hippophae L. (Elaeagnaceae)
Jia, Dongrui ; Bartish, Igor (advisor) ; Štech, Milan (referee) ; Comes, Hans-Peter (referee)
The Neogene geologic processes and climatic changes had tremendous impact on evolution of biota in different regions of Northern Hemisphere (NH). The Qinghai- Tibetan Plateau (QTP) was a central part of these processes. Migrations from the QTP to other temperate regions represent one of the main biogeographic patterns for Northern Hemisphere. However, this 'out-of-QTP' hypothesis has never been tested through a phylogeographic analysis of a widely distributed species and the ages and routs of these migrations are largely not resolved. On the other hand, climate change played an important role in shaping the amount and structure of intraspecific genetic diversity, which provide the main basic substrate for any evolutionary change. Therefore, a detailed understanding of the effects of historic climate alterations on intraspecific genetic diversity can provide valuable insights into the evolutionary consequences of past climate changes and predicting the likely direction of global warming effects on sustainability of extant populations and species. In this thesis, I first studied the phylogeography of Hippophae rhamnoides to test the 'out-of-QTP' hypothesis (Chapter II). Then, I performed phylogenetic, dating and biogeographic analyses of the genus Hippophae (Chapter III). Finally, I studied the...
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