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Temperate flora of Patagonia and specific points of its evolution
Koubek, Matěj ; Ptáček, Jan (advisor) ; Šrámková, Gabriela (referee)
Patagonia is one of the few regions in the Southern Hemisphere with a temperate climate, and therefore provides a unique environment for studying the evolution of the local flora. Patagonian plants, like their temperate counterparts in the Northern Hemisphere, show higher rates of polyploidy. Polyploidy is a widespread condition among plants that plays a key role in the adaptation of species to various extreme stress conditions. Climatic characteristics, glaciations or volcanic activity, for example, are factors influencing the distribution of organisms. This work focuses on the study of the Patagonian flora, in particular on alpine and steppe species and their biogeography in relation to the climate and geology of the area. It also discusses the relationship between polyploidy and this distribution. Specifically, this work focuses on the widely distributed model species Azorella prolifera, which exhibits three ploidy levels. However, we have zero knowledge of the occurrence of individual cytotypes. The distribution and properties of polyploids have not been studied to a sufficient level in the Southern Hemisphere. Only a fraction of the papers dealing with this issue focus specifically on Patagonian plants. A more comprehensive insight into this topic may lead to a better understanding of the...
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Floral biology of tropical alpine plants
Holzbachová, Lucie ; Sklenář, Petr (advisor) ; Ptáček, Jan (referee)
Tropical alpine environments are characterised by specific environmental conditions to which the local plants adapted through evolution. The specificity is especially in a strong diurnal climate with temperatures falling below zero at nights. At the same time, this environment lacks thermal seasonality, which allows growth and flowering throughout the year. While floral biology is relatively well described in temperate regions, it has only been studied sporadically in the tropics. This study summarises the knowledge of floral biology in tropical alpine environments with a focus on zoophily plants. The principal part of this work is dedicated to floral traits, focusing on flowering phenology, which is diversified for every species during the year. In this way, plants face competition, especially for their pollinators, which decrease in abundance with altitude. Although not all phenological strategies have been studied so far, we can find several main flowering schemes. This literature review points to unexplored research topics about floral biology of plant inhabiting tropical mountains that might provide a basis for future studies.
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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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Microevolutionary processes in Cystopteris fragilis agg.
Ptáček, Jan ; Urfus, Tomáš (advisor) ; Chrtek, Jindřich (referee)
Polyploidization and hybridization are the main microevolutionary processes, which take place within pteridophytes and dominantly participate in their variability and further speciation. Reproductive strategies are also related with above mentioned processes, especially various type of apomictic reproduction, which play an important role within ferns (compared to Angiosperms). Polyploidization and hybridization take part in Cystopteris fragilis (L.) Bernh. (common fragile fern) and both are also recently participating in origin of new cytotype (mirrored by enormous proportion of mixed populations consisting off tetraploids to octoploids). The main goal of this diploma thesis is cytotype structure of particular stages within the life cycle of common fragile fern with evaluation of sporogenesis (viability, exospore length and number of spores), together with testing reproductive strategies of individual cytotype using flow cytometry. Moreover, an experimental hybridization is supplementing above mentioned aims of the diploma thesis. The main sources of variability seem to be restricted to tetraploids and pentaploids, whereas hexaploids produce only uniform progeny. Tetraploids form both diploid reduced and tetraploid unreduced spores (but only 1,97 % of total amount of spores). Pentaploids have variable...
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Reproductive modes and hybridization within Cystopteris fragilis agg.
Ptáček, Jan ; Urfus, Tomáš (advisor) ; Šrámková, Gabriela (referee)
Cystopteris fragilis agg. is taxonomically very complicated group of homosporous ferns. There are 4 species of the aggregate in Europe (C. fragilis, C. dickieana, C. alpina and C. diaphana), which are morfologically similar and their taxonomic status is still unresolved. Polyploidization, hybridization and the resulting reticulate patterns of evolution together contribute to enormous variation within the complex. Apomictic reproduction through apogamy is a very common phenomenon among ferns and it was also recorded in C. fragilis in the past. Gametophyte and sporophyte culture is commonly used to the study of reproductive modes. Pilot results and methods of following diploma thesis are presented in separeted chapter.
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