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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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Molecular evolution of meiosis in diploids and tetraploids of Arabidopsis arenosa
Holcová, Magdalena ; Schmickl, Roswitha Elisabeth (advisor) ; Mozgová, Iva (referee)
Meiosis is functionally conserved across eukaryotes, thus not expected to vary considerably among different species, and even less so among lineages within a species. However, recent studies showed that this is not necessarily the case in Arabidopsis arenosa. Genome scanning identified an excess differentiation in meiosis genes between A. arenosa diploids and tetraploids, interpreted as meiosis adaptation to the whole genome duplication in tetraploids and differentiation was also found between two diploid lineages. Thus, I present a population-based analysis of positive selection acting on meiosis proteins across multiple lineages of A. arenosa. I showed that meiosis proteins were under positive selection in all diploid lineages, mainly in the Pannonian and South-eastern Carpathian lineage. The evidence for positive selection in diploid lineages suggested differential pathways of meiosis adaptations in the species, probably reflecting the necessity to adapt to local environments, among all to temperature. The highest enrichment of amino acid substitutions (AASs) under positive selection was identified in tetraploids, in consistence with previous genome-scan results. As several interacting meiosis proteins were under positive selection in the same A. arenosa lineage, I hypothesize that the close...
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Phylogenetic Studies in the Polyploid Genus Curcuma L.
Záveská, Eliška ; Fér, Tomáš (advisor) ; Schmickl, Roswitha Elisabeth (referee) ; de Boer, Hugo (referee)
1 Phylogenetic Studies in the Polyploid Genus Curcuma L. SUMMARY Curcuma is genetically one of the most complex genera within the tropical family Zingiberaceae, with hybridization and polyploidization being the major forces in its evolution. In this thesis, I have focused mainly on the genetic background of Curcuma species variation, relationships and overall genome structure, as a key to solve long standing taxonomic problems. Results of my molecular studies on the genus Curcuma performed since 2007 represent an extension of ongoing taxonomic and nomenclatural work started by Jana Leong- Škorničková in 2000. The first part of the thesis consists of a broad, general introduction to the subject to reflect the current state of knowledge, formulate the major problems to be confronted within the genus, and summarise the major results of the studies presented in the second part of the thesis. As the main obstacles in studying Curcuma are consequences of its reticulate evolution, it is also outlines the importance of understanding the genetic background and species relationships using molecular markers. Common molecular methods used for assessing phylogenetic relationships on the intraspecific and infrageneric levels - AFLP and sequencing of selected markers from cpDNA, nrDNA and nDNA - are described, with the...
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Autopolyploids: particularly hopeful monsters
Holcová, Magdalena ; Schmickl, Roswitha Elisabeth (advisor) ; Mráz, Patrik (referee)
Autopolyploidy, genome duplication per se, is a severe mutation which presents both great challenge and great opportunity for the species which has undergone it. First, a whole series of initial challenges has to be overcome, e.g., establishment within diploid parental population, proper functioning of the cell with doubled genetic information and restoration of proper mitosis and meiosis. The population genetic changes can become beneficial afterwards as the two times higher effective population size and polysomic inheritance increase heterozygosity and genetic variability within the new polyploid lineage. It also reduces negative impacts of genetic drift and inbreeding depression. In evolutionary context, having two genomes allows selection to be more relaxed, thus genes can quickly diversify into alleles with new function or sub-function. To better understand the molecular mechanisms of selection on a population level, I choose example of meiosis genes evolution in a polyploid Arabidopsis arenosa (Brassicaceae) species complex. This only diploid-autotetraploid member of the plant leading model genus Arabidopsis provides an ideal system for addressing general questions on the triggers and consequences of genome duplication in plants. In contrast to other members of the genus, A. arenosa remained...
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