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The patterns of local adaptation to serpentine bedrock in plant populations
David, Jan ; Čertner, Martin (advisor) ; Konečná, Veronika (referee)
The most important abiotic factors of serpentine habitats are lack of water, low content of main nutrients, high magnesium content and a high concentration of heavy metals. Thus, serpentine soils are a very stressful environment for most plant. For their exceptional characteristics, serpentine sites are suitable for the study of evolutionary processes. The present literary review contains a summary of the main topics related to the issue of plant populations growing on serpentine bedrock. In addition, the mechanisms of the local adaptation and the conditions that allows these processes are analyzed. At the end of the thesis, the ecological aspect of the habitats is discussed, which can serve as areas with reduced competition and provide the living space to the competitively weaker species. Due to the specific conditions at the serpentine areas, these areas are characterized by a higher level of endemism and often serve as a refuge for relict species. Keywords: Serpentinophyte, serpentine, serpentine endemism, local adaptation, substratum specialization
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Microevolutionary processes in mixed-ploidy populations of plants
Čertner, Martin ; Kolář, Filip (advisor) ; Ramsey, Justin (referee) ; Duchoslav, Martin (referee)
Polyploidization (whole-genome duplication) is widely considered one of the most important evolutionary forces driving the diversification of flowering plants. Polyploids tend to originate recurrently and many plant species retain individuals of two or more different ploidy levels in certain parts of their distributional range of even within their populations. The main aim of this thesis was to address the understudied aspects of polyploid speciation by employing new, convenient methods and/or studying plant model systems with unique features. Difference in monoploid genome size of Tripleurospermum inodorum (Asteraceae) cytotypes provided a unique opportunity for addressing the rate of spontaneous polyploidization in natural populations by enabling the easy distinction of neopolyploid mutants from long-established polyploids in routine flow-cytometric analyses. Repeated ploidy screening in mixed-ploidy populations of annual T. inodorum have been, to our knowledge, the very first attempt to document temporal changes in cytotype composition in situ. In spite of considerable between- year oscillations in cytotype frequencies, both diploids and tetraploids usually persisted locally for several consecutive years. The common incidence of such ploidy mixtures along with a partial fertility of triploid...
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The patterns of local adaptation to serpentine bedrock in plant populations
David, Jan ; Čertner, Martin (advisor) ; Prančl, Jan (referee)
For sessile organisms such as plants, substrate specialization acts a very important role, because plants have no choice when choosing a suitable substrate. Plants can respond very specifically to substrate, and local adaptations often begin to emerge, especially if their substrate composition is completely different from the parent substrate in which the plant grows usually. The thesis deals specifically with the problem of serpentine populations, the challenges that these plants have to deal with, and the local adaptations that arise in these populations. Keywords: Serpentinophyte, serpentine, serpentine endemism, local adaptation
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The origin and evolutionary significance of triploid hybrids in diploid-tetraploid contact zone in Tripleurospermum inodorum
Ryšavá, Hana ; Čertner, Martin (advisor) ; Chrtek, Jindřich (referee)
The presence of triploid individuals, whether hybrids arising from crosses of diploid and tetraploid plants, or spontaneously generated triploid hybrids diploid populations, is increasingly important in plant populations. However, the possible evolutionary role of the triploid hybrids is closely connected to the frequency of their occurrence, to their relative fitness (compared to parental cytotype) and fertility. As a model plant I choosed Tripleurospermum inodorum, in which a relatively frequent occurrence of triploid hybrids was documented in mixed populations of tetraploids and diploids. This annual plant achieves realy quick its reproductive maturity and is easily cultivated, making it an ideal model for cultivation and pollinating experiments. Compared to parental cytotypes, the triploid hybrids of T. inodorum take approximately the same (mostly mediated) fitness values. In vitro conditions were cultivated to measure of germination rates. Germination rate of triploid seeds was comparable to diploid parental cytotype. In the subsequent comparative cultivation, nearly 150 plant individuals (2x, 3x, 4x, and aneuploid cytotype) in the greenhouse showed that the triploids had intermedial values of their parental cytotypes or close to one of the parents. Thus, the vitality of the triploid plants is...
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Mechanisms driving di- and tetraploid coexistence in mixed-ploidy populations of Tripleurospermum inodorum
Nedomová, Anežka ; Čertner, Martin (advisor) ; Dostálek, Tomáš (referee)
Genome duplication plays a significant role in plant evolution. Formation of new polyploids is generally considered to be rare. Nevertheless, under natural conditions mixed-ploidy populations occur in relatively large numbers. Only the observations in the cytotype contact zone can identify all the factors affecting the stability or instability of the population. Number of research focusing on study of cytotype coexistence in natural mixed-ploidy populations is still low. As a model system for the study of mechanisms governing cytotype coexistence was chosen the Tripleurospermum inodorum. Research focused on natural mixed-ploidy populations and also on planted mixed-ploidy populations. Permanent plots were located in south, west, northwest and north Bohemia. Field observations were supplemented by cultivation experiments carried out in the greenhouse. Several phenomena were discovered at the level of whole populations. Cytotype distribution in the plot was random. The spatial structure of natural populations was quickly changing even within a single season. Even between single plot evaluations the cytotype ratios varied. Three percent of all plants were triploid hybrids. Most often detected cytotype in soil seed bank was diploid cytotype. The study of population dynamics shows, that tetraploids are...
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Polyploidy in natural populations of Arabidopsis
Bayerová, Jana ; Kolář, Filip (advisor) ; Čertner, Martin (referee)
This thesis deals with polyploidy in natural populations in the genus Arabidopsis. It summarizes information about the relatives of Arabidopsis thaliana, a prominent model organism for research on genetics and plant physiology. Literature shows that polyploidy affects ecological, climate and soil requirements, as well as mating system of the plants in genus Arabidopsis. Most of the published studies is focused on the study of artificial polyploid hybrids created by crossing experiments - especially with the Arabidopsis thaliana. In contrast, my thesis deals with the natural polyploids observed within the genus. In particular, I focus on the nearly unstudied di- polyploid complex of high-altitude populations of Arabidopsis arenosa in the Tatra Mountains. This complex represents a unique model system for studying the effects of polyploidization in the wild - thanks to the high morphological and ecological diversity of the hybrids, and to the relative genetic similarity of the parental populations. Key words: allopolyploid, Arabidopsis, Arabidopsis arenosa, autopolyploid, hybridization, polyploidization, Tatry
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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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The role of triploid hybrids in mixed-ploidy populations of Tripleurospermum inodorum (Asteraceae)
Jirsáková, Hana ; Čertner, Martin (advisor) ; Kolář, Filip (referee)
The doubling of the nuclear genome is considered to be one of the main ways in which new sympatry plant species can arise. Polyploidy is also generally a significant source of new evolutionarily advantageous abilities. However, it is not always that way, polyploids with an odd number of chromosome sets have often limited viability and fertility. In cytotype mixed populations of diploids and tetraploids, or in diploid populations alone with the contribution of high rate of unreduced gametes formation may produce triploid hybrids. In some cases, their vitality is even comparable with parental cytotypes but they produce only a small number of offsprings and in addition of different ploidy levels. Although it has been recently thought that they have no evolutionary significance, now based on many experimental works it is known with confidence that they can significantly participate in the new polyploid formation. If triploids occur in the population with sufficient frequency, they may play a role in stabilizing of the common coexistence of diploid and tetraploid cytotypes. Triploid hybrids may despite their limited fertility contribute to the bi-directional gene flow between their parents, and thus overcome the barrier of their different ploidy levels. A suitable model to study the role which can the triploid...
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