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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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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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Microevolutionary processes and inter-cytotype interactions in mixed-ploidy populations
Trávníček, Pavel ; Suda, Jan (advisor) ; Frajman, Božo (referee) ; Zozomová, Judita (referee)
[Abstract] This thesis is aimed at better understanding of cytotype co-existence in mixed- ploidy populations with an emphasis on a microevolutionary processes behind it. Our past knowledge was based on a few thoroughly investigated model taxa like Chamerion angustifolium and Heuchera grossulariifolia, but some generalizations seem to be premature in the light of new findings. A detailed research of other taxa included in the thesis showed that polyploid complexes can vary dramatically in their ability to cope with the co-existence of cytotypes in mixed-ploidy popu- lations. Whereas mixed-ploidy populations are virtually lacking in some species (an example being Vicia cracca, Paper III.), ploidy-heterogeneous populations are very common in others, maintained by free mating interactions and the absence of reproductive isolation among cytotypes (e.g. Pilosella echioides, Paper II.). The strenght and cumulative effect of various breeding barriers (both pre- or post- zygotic) govern the position of a particular multi-ploidy complex between these two extremes and co-determine the type of cytotype co-existence in its mixed- ploidy populations. Despite the fact that the number of studies revealing cytotype co-existence has been increasing rapidly, evolutionary background and consequences of such co-...
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