National Repository of Grey Literature 6 records found  Search took 0.01 seconds. 
Seasonal dynamics of mats composed by green alga Zygnema (Zygnematophyceae)
Trumhová, Kateřina
The mats formed by Zygnema spp. are well known and frequently found in streams, puddles, seepages, and ponds. Owing to the low and inconsistent water quantity of these biotopes, algae are periodically subjected to stresses like desiccation, freezing, or strong solar radiation. Recent studies have revealed that Zygnema survives various stresses in pre-akinetes, modified resistant vegetative cells. However, earlier experiments mostly aimed at osmotic stress and desiccation. Moreover, the mats formed by these algae have seasonal dynamics that have been observed several times, not only in temperate conditions but also in the Arctic. Field observations revealed that most of the biomass is periodically lost, and new mats are formed every year. Simultaneously, we know little about the genetic composition of the mats and how it changes over time; previous work has focused mainly on the mats as an entirety. Therefore, this work mainly aimed to subject the mats formed by the algae Zygnema spp. to long-term observation and subsequent experiments. We selected a region in the Austrian Alps, which we visited several times a year, and sampled two sites with different water regimes. Further research in collaboration with colleagues occurred in the Arctic. Zygnema spp. strains were subsequently isolated from the...
Seasonal dynamics of mats composed by green alga Zygnema (Zygnematophyceae)
Trumhová, Kateřina ; Pichrtová, Martina (advisor) ; Remias, Daniel (referee) ; Žárský, Jakub (referee)
The mats formed by Zygnema spp. are well known and frequently found in streams, puddles, seepages, and ponds. Owing to the low and inconsistent water quantity of these biotopes, algae are periodically subjected to stresses like desiccation, freezing, or strong solar radiation. Recent studies have revealed that Zygnema survives various stresses in pre-akinetes, modified resistant vegetative cells. However, earlier experiments mostly aimed at osmotic stress and desiccation. Moreover, the mats formed by these algae have seasonal dynamics that have been observed several times, not only in temperate conditions but also in the Arctic. Field observations revealed that most of the biomass is periodically lost, and new mats are formed every year. Simultaneously, we know little about the genetic composition of the mats and how it changes over time; previous work has focused mainly on the mats as an entirety. Therefore, this work mainly aimed to subject the mats formed by the algae Zygnema spp. to long-term observation and subsequent experiments. We selected a region in the Austrian Alps, which we visited several times a year, and sampled two sites with different water regimes. Further research in collaboration with colleagues occurred in the Arctic. Zygnema spp. strains were subsequently isolated from the...
Diversity of the Micrasterias papillifera / M. radiosa (Desmidiales) species complex
Trumhová, Kateřina ; Šťastný, Jan (advisor) ; Mareš, Jan (referee)
This Master's thesis deals with diversity within the Micrasterias papillifera/ M. radiosa (Desmidiales) species complex. Both species are inhabitants of endangered biotops, like peat-bogs and, like other desmids, are used for biomonitoring. Many described varieties for both of them can be found in taxonomic literature, but their morphology is overlapping and revision of this species complex seemed to be necessary. All strains were isolated from peat-bogs and lakes across Europe and my dataset was properly completed by strains from algal collections. Results of phylogenetic analysis of sequences for ITS and psaA showed, that the real intraspecific diversity of Micrasterias papillifera Brébisson ex Ralfs was overestimated. Although I could find a little intraspecific diversity within the ‚papillifera' lineage in the phylogenetic tree based on ITS sequences, it did not correspond with a morphology of isolates. M. papillifera possess unexpected morphological plasticity and also some isolates designated as Micrasterias radiosa Ralfs were present in this lineage. On the contrary, there were only a few isolates in the lineage ‚radiosa'. This species seems to be relatively rare and probably has limited distribution. Both species are morphologically well delimited from each other on the basis of several characters...
Diversity, distribution, phylogeny and ecology of the genus Micrasterias (Desmidiales)
Trumhová, Kateřina ; Šťastný, Jan (advisor) ; Bestová, Helena (referee)
The genus Micrasterias comprises one of the most beautiful organisms. It attracts, due to its spectacularly shaped cells, the attention of scientist and amateur biologist almost for almost 200 years. This thesis summarizes the current knowledge about these extraordinary organisms. The first part deals with the morphology and the life cycle of these algae. They share a unique type of reproduction (conjugation) with the other representatives of the class Zygnematophyceae. The second part concerns phylogeny of this genus. Several morphologically distinct species have been revealed with the aid of molecular phylogenetic methods to belong to the genus Micrasterias. A polyphasic evaluation of three species complexes within this genus also revealed an extensive hidden diversity. The last chapters summarize the knowledge about the influence of hidden diversity and accelerated morphological evolution on our understanding of diversity and biogeography of these organisms.
Diversity of the Micrasterias papillifera / M. radiosa (Desmidiales) species complex
Trumhová, Kateřina ; Šťastný, Jan (advisor) ; Mareš, Jan (referee)
This Master's thesis deals with diversity within the Micrasterias papillifera/ M. radiosa (Desmidiales) species complex. Both species are inhabitants of endangered biotops, like peat-bogs and, like other desmids, are used for biomonitoring. Many described varieties for both of them can be found in taxonomic literature, but their morphology is overlapping and revision of this species complex seemed to be necessary. All strains were isolated from peat-bogs and lakes across Europe and my dataset was properly completed by strains from algal collections. Results of phylogenetic analysis of sequences for ITS and psaA showed, that the real intraspecific diversity of Micrasterias papillifera Brébisson ex Ralfs was overestimated. Although I could find a little intraspecific diversity within the ‚papillifera' lineage in the phylogenetic tree based on ITS sequences, it did not correspond with a morphology of isolates. M. papillifera possess unexpected morphological plasticity and also some isolates designated as Micrasterias radiosa Ralfs were present in this lineage. On the contrary, there were only a few isolates in the lineage ‚radiosa'. This species seems to be relatively rare and probably has limited distribution. Both species are morphologically well delimited from each other on the basis of several characters...
Diversity, distribution, phylogeny and ecology of the genus Micrasterias (Desmidiales)
Trumhová, Kateřina ; Šťastný, Jan (advisor) ; Bestová, Helena (referee)
The genus Micrasterias comprises one of the most beautiful organisms. It attracts, due to its spectacularly shaped cells, the attention of scientist and amateur biologist almost for almost 200 years. This thesis summarizes the current knowledge about these extraordinary organisms. The first part deals with the morphology and the life cycle of these algae. They share a unique type of reproduction (conjugation) with the other representatives of the class Zygnematophyceae. The second part concerns phylogeny of this genus. Several morphologically distinct species have been revealed with the aid of molecular phylogenetic methods to belong to the genus Micrasterias. A polyphasic evaluation of three species complexes within this genus also revealed an extensive hidden diversity. The last chapters summarize the knowledge about the influence of hidden diversity and accelerated morphological evolution on our understanding of diversity and biogeography of these organisms.

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