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Evolution of the genus Malus with a particular reference to old and local cultivars
Polcar, Václav ; Urfus, Tomáš (advisor) ; Macková, Lenka (referee)
The following work deals with the genus Malus in terms of the significant diversity that this genus represents. It summarizes a basic knowledge about the taxonomic position and world centers of the genus evolution. Part of the thesis also discussed reproductive mechanisms as a source of the genus diversity. The thesis then focuses on the species Malus domestica, its evolution and the hybrid origin. In this context, old varieties of apple trees, their significance and pomologically important regions of the Czech Republic are presented. An integral part of this work is also devoted to the protection of old varieties, its limits and possibilities. The protection of old varieties also encompasses the extensive orchard as an important agroecosystem. Finally, different Czech regions are compared with respect to the quantity of reported old varieties.
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Hybridization as a source of threat to Urtica kioviensis
Pekařová, Michaela ; Urfus, Tomáš (advisor) ; Štěpánek, Jan (referee)
Hybridization can have a negative impact on native taxa, which means a risk to plant biodiversity. Urtica kioviensis (2x) is a rare species of that grows in mixed populations together with two cytotypes (2x and 4x) of the closely related taxon Urtica dioica (stinging nettle). The presence of hybrids has been described in the past. Here I studied hybridization at localities in the Czech Republic (PR Plačkův les a říčka Šatava, NPR Ranšpurk), Slovakia (PR Jurský Šúr), and Hungary (Kóny, Fehér-tó). These taxa and their hybrids were studied by flow cytometry and morphometric analysis. Both methods provided evidence of ongoing hybridization. The continuous pattern at the diploid level suggests homoploid hybridization and subsequent introgression affecting mainly U. kioviensis. The possibility of backcrossing at the diploid level was also confirmed by analyses of pollen fertility or staining. Triploid individuals were also detected, showing differences in relative genome sizes and different positions relative to the parental taxa in morphometric analyses. Based on these results, it's not possible to reliably determine their origin. Heteroploid hybridization is likely to occur, but its presence cannot be definitely confirmed or excluded. Hybrids are common in mixed populations of U. kioviensis and mean a...
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Speciation mechanisms and the role of reinforcement in mammals
Horký, Jakub ; Hulva, Pavel (advisor) ; Reifová, Radka (referee)
Speciation, the process of the formation of new species, comprises a diverse range of microevolutionary mechanisms acting in unison, which lead to the gradual formation of reproductive barriers between populations. The study of speciation has significantly progressed since its origins around the midpoint of the nineteenth century, owing to progressively improving analytical methods and the data said methods obtained, allowing us to observe previously invisible patterns and form new hypotheses on their basis. From traditional to modern research, this review's goal is to describe the contemporary understanding of speciation's concepts and mechanisms, focusing on those which are most relevant to mammals. Modern understanding of spatial contexts, prezygotic and postzygotic isolating mechanisms, and character displacement, including a type of reproductive character displacement dubbed reinforcement, are discussed. Significant emphasis is placed on the topics of maladaptive and adaptive hybridization, which, together with reinforcement and development of new genomic methods, has this review identified as the current frontier of speciation research. Keywords: reproductive isolating mechanisms, microevolution, character displacement, hybridization, reinforcement, speciation
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triggers of asexual reproduction: on the crosslink between hybridization, asexuality, polyploidy and speciation on example of Cobitidae loaches
Marta, Anatolie ; Janko, Karel (advisor) ; Arai, Katsutoshi (referee) ; Trachtulec, Zdeněk (referee)
(in English) Sexual reproduction is considered a nearly universal feature of all eukaryotic organisms and has been hypothesized to be their ancestral state. Sexual reproduction is mainly represented by meiotic division, recombination, production of haploid gametes and fertilization. Although molecular and cytological mechanisms underlying meiosis are highly conservative they may be disrupted in numerous ways leading to the emergence of so-called asexual lineages. The proximate origins of asexuality may differ for particular taxa. In vertebrates, asexuality frequently is triggered by interspecific hybridization. Nowadays "classical" theories predict that asexuals should not be able to persist on a long-term evolutionary scale. However, the hybrid lineages have to overcome short-term disadvantages, such as postzygotic barriers ranging from complete hybrid sterility to altered meiosis resulting in asexual reproduction and even ploidy elevation. Despite that hybrid sterility is one of the most common outcomes of interspecific hybridization, however various lineages found their ways to alleviate these problems and produce viable clonal gametes. The knowledge about proximate mechanisms of unreduced gamete formation in asexual lineages is very limited as many studies were restricted due to methodological...
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Mechanisms of reproductive isolation between two hybridizing passerine species, the common nightingale and the thrush nightingale
Poignet, Manon ; Reifová, Radka (advisor) ; Choleva, Lukáš (referee) ; Kratochvíl, Lukáš (referee)
iv - ABSTRACT (in English) - A key step in the origin of new species is the evolution of the reproductive isolation mechanisms separating the gene pools of newly emerging species. Despite a growing number of studies, we still know very little about the molecular, physiological and genetic mechanisms underlying reproductive isolation. Hybrid zones represent useful examples of ongoing species differentiation and can provide information about the nature of reproductive isolation separating the species and mechanisms facilitating or limiting the hybridization. Using two naturally hybridizing passerine species, the common nightingale (Luscinia megarhynchos) and the thrush nightingale (L. luscinia), we evaluated several mechanisms of reproductive isolation at the chromosomal, phenotypic, and genetic levels, with a focus on postmating prezygotic (PMPZ) and postzygotic isolation mechanisms. These nightingale species diverged ~1.8 Mya and currently hybridize in a secondary contact zone running across Central and Eastern Europe. First, we analysed the genetic composition of the secondary contact zone, demonstrating that parental forms are predominant in the hybrid zone, with few F1 hybrids (3.4%), early backcross hybrids (3.1%) and the absence of F2 hybrids. This suggests strong but incomplete reproductive isolation....
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Určování říčních populací lakušníku štítnatého (\kur{Ranunculus peltatus)}
DOLEJŠEK, Vojtěch
In some Czech rivers hybridogenous populations of pond water-crowfoot (Ranunculus peltatus) were detected. These populations are morphologicaly similar to the parental pond water-crowfoot and it is sometimes difficult to tell them apart. Such hybridogenous populations are not detectable via flow cytometry and are only detectable via sequencing. In this thesis I was trying to find out whether the hybridogenous populations could be clearly distinguished based on their morphology from the parental species pond water-crowfoot.
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Reproduction and hybridization in ferns
HORNYCH, Ondřej
This thesis studies several aspects of fern reproduction and hybridization. Aspects of multiple stages in the fern life cycle are analyzed. Specifically, rates of spore abortion and antheridiogen usage are assessed and compared between various groups. Own cultivation and spore assessment data are compared extensively with existing literature. Finally, the rate of hybridization in natural populations and the symmetry of hybridization is analyzed in buckler ferns (Dryopteris carthusiana group).
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Invasiveness and hybridisation in evolution of closely related species
Gruntová, Martina ; Hojka, Jakub (advisor) ; Urfus, Tomáš (referee)
Plant invasiveness, or the extensive spreading of a plant species into new and non-native areas, is an important and frequently discussed process in botany, influenced by many internal and external factors that determine how a plant will spread and how successful will the spreading be. One of the important factors affecting the level of invasiveness is the ability to hybridise and also ability to become polyploids, because via those processes plants acquire genetic variation that can provide advantageous predispositions for their dispersal. Plants and their spreads are also influenced by external ecological factors, i.e. the environment in which they grow, other species sharing the same habitat, and e.g. climate change or human activity, which change the environmental characteristics and therefore also the areas of distribution. The aim of this thesis is to find links between hybridisation and the success of plant dispersal, and subsequent invasiveness (i.e. the spread of a plant in a non-native range), by using the genus Rorippa as a model. The Central European lineage of lowland species of the genus Rorippa represents a suitable group to study these processes due to the frequency of hybridisation, the variability of ploidy levels and the previously detected invasiveness of one of the species (R....
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The formation and maintenance of odd ploidy level cytotypes in the heteroploid system and their contribution to the heteroploid gene flow in invasive perennial species
Dýbová, Markéta ; Slovák, Marek (advisor) ; Šrámková, Gabriela (referee)
Polyploidy is one of the crucial evolutionary factors in the evolution of vascular plants. Polyploid cytotypes are mostly reproductively isolated from their diploid counterparts; however, there exists the possibility of gene exchange between different ploidies/species via heteroploid geneflow. The heteroploid gene exchange might be mediated through the odd and aneuploid cytotypes, which evolved via hybridisation but also de novo via the fusion of reduced and unreduced gametes. The primary focus of the thesis will be to review knowledge about the formation of odd cytotypes in heteroploid systems and evaluate their contribution to gene exchange between given ploidies. The particular focus will be on gene flow between higher ploidy levels in perennial invasive species complexes. Attention will also be paid to mechanisms enabling their maintenance in the population and the consequence of their long term persistence on between ploidy (species) hybridisation on their invasive potential. Key words: odd ploidy level, invasive plants, hybridization, life strategy
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