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Sources of Sorbus aria agg. variation
Bílá, Jana ; Urfus, Tomáš (advisor) ; Krahulec, František (referee)
The main drivers of microevolution in the genus Sorbus are interspecific hybridisation and polyploidy. The fate of new hybrid and polyploid taxa is determined by their mode of reproduction. Especially apomixis could be very advantageous for these new taxa. The S. aria agg. (subg. Aria) plays an important role within the genus since its members are involved in all hybridisation events and thereby is responsible for the substantial part of variation of the genus. Flow cytometry, molecular markers and multivariate morphological analyses were employed to evaluate the processes generating the variability in the S. aria group. Three ploidy levels were detected among species from subg. Aria in the Czech Republic. All of them could be found in the South Moravia, whereas only tetraploids occur in the Bohemia region. Moreover, most of the Czech taxa (5 out of 7) grow also only in the South Moravia which is therefore considered as a centre of diversity of the genus Sorbus in the Czech Republic. Flow cytometry seed screen revealed 7 modes of reproduction among the individuals from S. aria agg. A wide range of sexual and apomictic types of reproduction including reduced and unreduced gametes was detected. All of the diploid individuals are completely sexual. Among polyploid taxa, most of the species are...
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Mechanisms of asexual reproduction in reptiles
Augstenová, Barbora ; Kratochvíl, Lukáš (advisor) ; Abramjan, Andran (referee)
In the case of reptiles, there has been described an occurrence of an asexual reproduction, especially in the case of a group Squamata; the asexual reproduction of birds (Aves) has been observed, too. Multiple times the asexuality of reptiles has been originated. Occurrences of obligate and facultative asexual species have been described. Most obligate asexual species have theirs origin in one or more hybridization events between closely related species. However, within the family Xantusiidae two exceptions where asexuality apparently originated without hybridization were discovered. Facultative parthenogenesis was originally expected only among reptiles kept in captivity, where the females were separated from males for a long time. However, this assumption was later disproved. The majority of the specimens formed by facultative parthenogenesis has reduced viability, which can be caused by the imperfect mechanism of the formation of parthenogenetic offspring. The terminal fusion is considered to be the probable mechanism of creation of diploid oocytes in the case of facultative parthenogenesis reptiles. The cytological mechanism of the parthenogenetic offspring's genesis was described for the obligate parthenogenetic species just for genus Aspidoscelis. During oogenesis in this case is ploidy...
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Sources of Sorbus aria agg. variation
Bílá, Jana ; Urfus, Tomáš (advisor) ; Chumová, Zuzana (referee)
Genus Sorbus is a very complex group of vascular plants. Various genetic lineages which can be fixed by apomixis are driven by interspecific hybridisation and polyploidy. Species from S. aria agg. have the highest variation probably due to an extra mechanism - introgressive hybridisation. There are several concepts of the aggregate which are usually based on three main species: S. aria, S. umbellatta and S. graeca. Therefore, new microspecies are derived by genome doubling and hybridisation between the main species. Units of the aggregate are assessed differently as the distinction of taxa is very complicated due to the overlap of the morphological variability. The aggregate itself can be sometimes considered as a category for species of uncertain origin or identification. Four species from S. aria agg. occur in the Czech Republic. In addition, the conclusion offers questions that will be addressed in the master's thesis.
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Origin, inheritance and ecological sygnificance of apomixis in the genus Hieracium s.str.: the role of genetic and epigenetic mechanims
Pinc, Jan ; Mráz, Patrik (advisor) ; Hojsgaard, Diego (referee) ; Mandák, Bohumil (referee)
Apomixis (asexual reproduction by seeds) has the considerable potential in agriculture and crop breeding due to its ability to produce genetically identical progenies in a form of persistent propagules, i.e. seeds. However, the processes laying behind the origin of apomixis and connected molecular mechanisms are still unknown. Despite the fact, that apomicts are considered to be an evolutionary dead-ends, they are often more widely distributed than their sexual relatives (this phenomenon is commonly referred to as geographical parthenogenesis (GP). Although this phenomenon is studied for decades, its causes are still not fully understood. Importantly, several recent studies pointed out that apomicts with limited genetic variability can at some extent react to changing environment through changes in gene transcription by epigenetic modifications. It is generally assumed, that hybridisation and polyploidization played a crucial role in the emergence of apomixis. For this reason, presented studies test the putative origin of selected polyploid apomicts and if the interspecific hybridisation between diploid sexuals triggers polyploidization using predominantly polyploid and apomictic genus Hieracium s. str. Surprisingly, the presented study demonstrates the hybrid origin of almost all investigated...
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Mode of reproduction and reproductive assurance of diploid and polyploid hawkweeds (Hieracium s. str.)
Zdvořák, Pavel ; Mráz, Patrik (advisor) ; Krahulcová, Anna (referee)
The mode of reproduction can greatly influence the demography and the evolutionary success of the taxon. In the case of autonomous asexual formation seeds are apomictic taxa fully independent of pollinators and compatible partners. For sexual taxa with strict autoincompatibility it is the opposite, i.e. sexual taxa need pollinators and compatible partners for birth of offspring. Therefore, in marginal population and for more extreme situation with lower pollinating activity will have apomictic taxa a higher level of reproductive assurance than sexual taxa vascular plants. This hypothesis was tested in natural populations of apomictic and sexual taxa. In the diploma thesis we therefore investigate the method mode of reproduction and reproductive assurance of 52 taxa of the genus Hieracium s. str. (family Asteraceae) in Europe. Of these, 12 were diploid sexually diploid taxa and 42 polyploid apomictic reproductive taxa. From these taxa we harvested seeds from fully developed capitulum and we determined the potential (total number of seeds in the capitulum) and the realized (the percentage of well-developed seeds at the capitulum). The ploidy of the offspring (the embryos and the seedling) and method origins of seeds we examined using flow cytometry. The results show that the plants of diploid species...
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Transgenerational effect of nutrient treatment on progeny of an apomitic plant
Vlk, Lukáš ; Mráz, Patrik (advisor) ; Skálová, Hana (referee)
Environmental conditions can influence epigenetic variability of clonal organisms. These environmentally induced changes have potential to persist in following generations. In theory, this transgenerational memory could allow clonal (and especially apomictic) plants to partly compensate reduced genetic variability and could enhance adaptative ability of apomictic populations. According to Muller's ratchet model, asexual organisms amass deleterious mutations, which could lead to their extinction. Possible transgenerational memory could partly compensate for this. It could also account for longtime survivorship of asexual organisms in environment. This thesis deals with transgenerational memory of triploid apomictic populations of Hieracium alpinum, with completely missing sexuality and thus genetically uniform offspring. Transgenerational effect in Hieracium alpinum was studied on clonal lineages originated from 5 populations (Norway, Austria, Bosnia and Herzegovina and Slovakia). Seeds were planted in cultivation experiment I in 3 treatments (control, added nutrients, added salicylic acid) and vegetative and generative traits were measured. Plants responded to nutrient addition but not to salicylic acid. Treatment with nutrient addition increased biomass, number of leaves and SLA (specific leaf...
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Mechanisms of asexual reproduction in reptiles
Augstenová, Barbora ; Kratochvíl, Lukáš (advisor) ; Abramjan, Andran (referee)
In the case of reptiles, there has been described an occurrence of an asexual reproduction, especially in the case of a group Squamata; the asexual reproduction of birds (Aves) has been observed, too. Multiple times the asexuality of reptiles has been originated. Occurrences of obligate and facultative asexual species have been described. Most obligate asexual species have theirs origin in one or more hybridization events between closely related species. However, within the family Xantusiidae two exceptions where asexuality apparently originated without hybridization were discovered. Facultative parthenogenesis was originally expected only among reptiles kept in captivity, where the females were separated from males for a long time. However, this assumption was later disproved. The majority of the specimens formed by facultative parthenogenesis has reduced viability, which can be caused by the imperfect mechanism of the formation of parthenogenetic offspring. The terminal fusion is considered to be the probable mechanism of creation of diploid oocytes in the case of facultative parthenogenesis reptiles. The cytological mechanism of the parthenogenetic offspring's genesis was described for the obligate parthenogenetic species just for genus Aspidoscelis. During oogenesis in this case is ploidy...
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Hybridization within genus Sorbus in Central Europe
Ondříčková, Klára ; Urfus, Tomáš (advisor) ; Knotek, Adam (referee)
The genus Sorbus is a very complicated group. Thanks to mikroevolutionary processes such as interspecific hybridization, polyploidy and apomixis produce large quantities of genetically distinct lineages. Hybridization between basic species (S. aria agg., S. torminalis, S. aucuparia, S. chamaemespilus) formed hybridogenous group which speciation is often associated with just polyploidy and apomixis formation, often only optional. Another type of reproduction is observed vegetative layering. The whole group is mophological very variable and taxonomic categorization of certain groups is not solved yet. The work also includes an introduction to the group Sorbus sudetica agg., which representative S. sudetica is endemic to Giant Mountains. At the end there are the current results and the methods that will be used for the master's thesis.
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Sources of Sorbus aria agg. variation
Bílá, Jana ; Urfus, Tomáš (advisor) ; Krahulec, František (referee)
The main drivers of microevolution in the genus Sorbus are interspecific hybridisation and polyploidy. The fate of new hybrid and polyploid taxa is determined by their mode of reproduction. Especially apomixis could be very advantageous for these new taxa. The S. aria agg. (subg. Aria) plays an important role within the genus since its members are involved in all hybridisation events and thereby is responsible for the substantial part of variation of the genus. Flow cytometry, molecular markers and multivariate morphological analyses were employed to evaluate the processes generating the variability in the S. aria group. Three ploidy levels were detected among species from subg. Aria in the Czech Republic. All of them could be found in the South Moravia, whereas only tetraploids occur in the Bohemia region. Moreover, most of the Czech taxa (5 out of 7) grow also only in the South Moravia which is therefore considered as a centre of diversity of the genus Sorbus in the Czech Republic. Flow cytometry seed screen revealed 7 modes of reproduction among the individuals from S. aria agg. A wide range of sexual and apomictic types of reproduction including reduced and unreduced gametes was detected. All of the diploid individuals are completely sexual. Among polyploid taxa, most of the species are...
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