|
| |
|
|
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.
|
|
| |
|
|
Taxonomy and variability of selected Sorbus taxa
LEPŠÍ, Martin
This thesis is a biosystematic study focusing on the taxonomy and variability of selected taxa of the genus Sorbus, one of the most diverse and taxonomically complicated plant groups in Europe. Classical and modern biosystematic methods - comparative study, chromosome counting, analysis of nuclear microsatellite markers, flow cytometry, and traditional multivariate and outline morphometric analyses were used to assess the morphological, karyological and genetic variability of the genus. The final synthesis of these approaches led to the description of several new taxa (species, hybrids and a subgenus) and the correction of several taxonomic misinterpretations. To reveal ongoing evolutionary processes responsible for the generation of the observed variability, the reproductive modes of 42 Sorbus taxa were examined using flow-cytometric seed and pollen screens. Apart from revealing major trends, the study estimates the frequency of rare events and provides several novel conclusions that are relevant both specifically to Sorbus/Rosaceae and to apomixis in general.
|
guest ::
