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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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Ecological and evolutionary consequences of edaphic differentiation in plant polyploid systems
Kolář, Filip ; Suda, Jan (advisor) ; Tribsch, Andreas (referee) ; Krahulec, František (referee)
The thesis deals with evolutionary and ecological consequences of edaphic speciation (adaptation to different soil types) and genome duplication (polyploidization), acting in concert. Using a wide range of ecological, karyological and molecular approaches, several hypotheses of general importance have been examined in three model angiosperm systems (ploidy variable species or species aggregates occurring both on and off specific substrates, including serpentines and calcareous soils). In the Knautia arvensis group (Caprifoliaceae) a unique cryptic diploid lineage in central Europe was identified to be restricted to serpentine and limestone outcrops, which served as refugia during environmental changes (forest spread, human impact) in the Holocene. These refugial populations exhibited strong evolutionary potential because they were able to polyploidize and escape beyond the borders of their original edaphically-conditioned refugia owing to hybridization with surrounding widespread homoploid genotypes. Survival of both Knautia cytotypes on serpentine soils was facilitated by their high tolerance to chemical stress factors such as high Ni concentrations and low Ca/Mg ratios. In the Galium pusillum group (Rubiaceae), a striking cytological, ecological, and taxonomic, diversity was revealed in northern and...
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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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Processes governing sympatric coexistence of di- and tetraploid cytotypes in primary contact zone of Knautia arvensis agg.
Hanzl, Martin ; Kolář, Filip (advisor) ; Duchoslav, Martin (referee)
Intensive cytotype screening in the primary contact zone of relict serpentine Knautia arvensis agg. revealed a striking predominance of the derivative tetraploid (81 % of subpopulations) over the diploid maternal race. Eleven mixed-ploidy subpopulations with the close spatial proximity of both cytotypes were identified. Flow cytometric analyses of almost 5 000 individuals led to discovery of two extremely rare minority cytotypes (3x, 6x). Vegetation analyses were made at two different spatial scales and in both cases confirmed the absence of distinctions in habitat preferences of cytotypes. Slight microhabitat segregation of cytotypes was however apparent at the finest spatial scales. Cytotype distribution within mixed-ploidy sites was not random. Striking patterns of cytotype clumping into cytotype uniform patches and negative spatial correlations between diploid and tetraploid individuals were apparent at all sites. Distribution of life cycle stages of diploids and tetraploids within the mixed-ploidy subpopulations were significantly different. The clonality was the most common mode of reproduction in the subpopulations of both cytotypes. Seedlings accounted for only 7 % of new plants. Significant distinctions in the plant vigour between the cytotypes were showed during the in situ comparison in...
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Evolutionary history of polyploid complex Galium pumilum in Central Europe
Knotek, Adam ; Kolář, Filip (advisor) ; Urfus, Tomáš (referee)
The thesis summarizes current knowledge about the polyploid complex of Galium pummilum agg. in Central Europe. This work should provide a theoretical background for a following diploma thesis. Most species of the aggregate are difficult to be determined due to considerable morphological variability and a complex evolutionary history probably involving recurrent polyploidization and hybridization events. Currently, new molecular methods are changing our opinion on the taxonomical classification within the group. Except for G. pumilum MURRAY, the other species show rather disjunctive distribution and are found on relict habitats. This could be caused by postglacial migration and subsequent area fragmentation. Most of the previous studies focused on Galium were published by Friedrich Ehrendorfer, who since the 50th defined division of the complex on the basis of chorological, karyological and morphological data. With new molecular methods, his hypotheses are now exposed to verification. Galium sudeticum TAUSCH. represents an enigmatic and vulnerable taxon of the Czech flora, that raises various interesting questions from both evolutionary and conservation points of view. It has a remarkable disjunct distribution in the Giant mountains (Krkonoše) and in one serpentine area in western Bohemia...
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Genome size evolution in the Zingiberaceae
Pospíšilová, Monika ; Fér, Tomáš (advisor) ; Kolář, Filip (referee)
The purpose of this study is to evaluate the existing knowledge on the evolution of genome size and also to focus on genome in the phylogenetic context. Among angiosperms we find a wide range of C-values (1C = 0.63 pg ? 1C = 127.4 pg), but the modal value is 0.6 pg. We still do not know much about the nature and mechanisms of plant genome size evolution, but we are learning more and more every year. There are already dozens of studies dealing with the dynamics of genome size of smaller taxonomic groups and on four of these they demonstrate possible approaches. Researching within higher taxonomic groups such as families is difficult and so more valuable. New research on the evolution of genome size in the family Zingiberaceae has started and my master thesis dealing with the Globbeae tribe should be part of it.
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Ecological and evolutionary processes in primary contact zone of cytotypes of Knautia arvensis agg.
Hanzl, Martin ; Urfus, Tomáš (referee) ; Kolář, Filip (advisor)
Genome duplication events have played a crucial role in plant evolution. According to recent estimates, nearly all the angiosperms are ancient polyploids. However, establishment of new polyploid lineages within diploid populations seemed to be very unlikely, based on theoretical analyses. Reproductive interactions between the cytotypes (so-called "minority cytotype exclusion") and resource competition might eventually lead to polyploid extinction. On the other hand, the whole variety of factors may compensate both processes under natural conditions (e.g. autogamy, assorative mating, spatial separation of cytotypes). Polyploid establishment in sympatry with diploid progenitor might thus not be as restricted, as previously thought. Subsequent cytotype coexistence may represent a stable equilibrium, or just a transition leading to extinction of one chromosomal race. It is usually almost impossible to discriminate between these alternatives. Polyploid range expansions are usually accompanied by competitive exclusion of diploid cytotype or colonization of new areas and habitats. When two cytological races meet, zones of contact are often formed. Contact zones could be divided into primary and secondary ones. Primary contact zones arise as a consequence of new polyploid emergence within the progenitor's...
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