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The strength of minority cytotype disadvantage in plant populations consisting of diploid and polyploid individuals
Pilneyová, Markéta ; Čertner, Martin (advisor) ; Chrtek, Jindřich (referee)
Mixed-ploidy populations, consisting of multiple cytotypes, are an optimal system for studying genome doubling consequences in plants. The role of frequency dependent selection, known as minority cytotype exclusion principle, is very important in them, but there are many factors limiting this selection. In my thesis, I evaluate the changes in cytotype frequencies and pattern in permanent plots in natural mixed-ploidy populations of three plant species - Butomus umbellatus, Knautia serpentinicola and Tripleurospermum inodorum and I also experimentally analyze partial aspects of frequency dependent selection towards minority cytotype in artificially established mixed-ploidy arrays of two plant species - Arabidopsis arenosa and Tripleurospermum inodorum. Varied changes in frequencies of minority cytotype ware revealed in permanent plots. Usually there was decrease, but in two plots there was increase in minority cytotype frequency and in one case it became dominant. Observed changes depend on initial frequencies of minority cytotype in populations, biological properties of species and particular environment of permanent plot. Relative indexes describing the frequency and the strength of disturbances and also the amount of soil nutrients was used to compare the environment of permanent plots across...
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Cytotype coexistence in plant populations, its mechanisms and temporal perspectives
Pilneyová, Markéta ; Čertner, Martin (advisor) ; Ptáček, Jan (referee)
Mixed-ploidy populations, consisting of multiple cytotypes, are an optimal model system for studying the consequences of genome doubling in plants. By comparing the polyploids with their diploid ancestors, we can discover the changes caused by polyploidization on both individual and population levels as well as understand the role polyploidization plays in plant evolution. In my thesis, I address the mechanisms affecting the coexistence of multiple cytotypes in mixed-ploidy populations. Minority cytotype exclusion principle and different breeding barriers between cytotypes (cytotype segregation, flowering phenology, pollinator fidelity, autogamy, gametophyte competition, triploid block) along with the effect of environment (disturbance, migration) on mixed-ploidy populations are described in this thesis. Particularly, I focus on the temporal persistence of mixed-ploidy populations due to its crucial role for our understanding of the polyploidization as an important evolutionary process.
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Processes determining the stability of cytotype coexistence in plant populations
Nedomová, Anežka ; Čertner, Martin (advisor) ; Urfus, Tomáš (referee)
Multiplication of nuclear genome is considered one of the most important processes in the plant evolution. Neopolyploids arise in a diploid population by merging of two unreduced gametes or through "triploid bridge". However establishment of a new polyploid in the current population is not easy. Polyploid has to overcome through various mechanisms (like a self-pollination, nonrandom pollination, etc.) "the minority cytotype exclusion" and increase their frequency in the population. Diploids and polyploids differ in ecological demands and competition abilities. There is no correlation between ploidy and wide ecological amplitude or competition abilities. With the current knowledge, we can not determine in which case is the mixed population stable. There is an assumption that the population contains two closely related species simply can not be stable, and therefore all cytotype mixed populations are unstable. Powered by TCPDF (www.tcpdf.org)
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