Research
Water-crowfoots (Ranunculus subgen. Batrachium)
Water-crowfoots is a lineage of white-flowered buttercups (Ranunculus) that is specialized to aquatic life. The main adaptations involve formation of specialized finely divided submerged leaves and marked heterophylly (formation of both divided submerged and flat aerial leaves in some species, depending on the site conditions). These plants are well-known also for their huge phenotypic plasticity (not only heterophylly but also peculiar terrestrial forms). Hybridization is frequent within the group and often is connected to polyploidization (i.e., allopolyploidy). Water-crowfoots also show variation in breeding systems (both allo- and autogamy and their combination) and wide range of habitats occupied by individual species. Due to reticulate evolution and overall close relatedness of the species, phylogeny of the group is little known. All these features make water-crowfoots an interesting model group.
Currently, in cooperation with colleagues from the Institute of Botany of the Czech Academy of Sciences, we survey a variation of water-crowfoots in central Europe using morphological analysis, flow cytometry (genome size estimation), chromosome counting and sequencing of several regions of nuclear and chloroplast DNA. We are also using next generation sequencing (PacBio platform) to describe variation of the ITS region and we are testing the use of microsatellites (SSRs) as the basic population-genetic marker. Various aspects of systematics or genetic variation of water-crowfoods may become topics of the students theses at all degrees (Bc., MSc., Ph.D.).
Taxonomy of the genus Centaurea (especially the sect. Jacea but also other groups)
We study morphological variation and its plasticity (based on statistical analysis of multiple populations), chromosome numbers, ploidy levels and genome sizes (both using classical chromosome counting and flow cytometry), hybridization, distribution of the species and their habitat requirement. Hybridization is particularly pronounced in this genus; to understand their frequency and distribution, we combine both field surveys and crossing experiments. We use morphology, genome size data (flow cytometry) and molecular methods to detect the hybrids. Only based on compilation of all this information, we may propose a revised taxonomy of the group and following nomenclature changes (if necessary).
In the past decade I focussed mainly on the area of Czechia and Slovakia. For a near future, the main objective might be the C. phrygia group in the East a South Carpathians (Ukraine, Romania) as well as several other groups (west-European C. nigra group, Alpine and south-European C. nigrescens , the C. jacea group as a whole and generally all taxa in the Balkans and east of the Carpathians). A revision of C. scabiosa group on the eastern margin of the Alps is needed (incl. putative endemic species, unknown hybridization within this group, distribution of Pannonian and Balkan elements in the area; a collaboration with Austrian colleagues is proposed).
Results of morphometric and flow cytometry analysis of central European populations of C. jacea are currently being prepared for publication. Flow cytometry in general is a promising tool to distinguish individual species groups and detect hybrids between them. Concerning molecular methods, sequencing of ITS region and several chloroplast regions has been tested but the overall variation and resolution of the data is low. The testing of AFLP method gave promising results; I also plan testing some NGS-based methods, such as RADseq. I seek for students who can join me in the Centaurea-research, possible topics of the theses are here.
Phenotypic plasticity of (Centaurea jacea)
This species comprises several morphology-defined taxa (subspecies or micro-species) in central Europe (and even more in the southern Europe). However, it seems that the morphology (= important determination characters) is partly determined by habitat conditions and thus it is unclear whether the reported taxa are real units (of independent origin and having its own morphological and genetic features) or if all are only extreme forms of one highly variable taxon, which arise repeatedly in similar habitat conditions.
The problem has already been studied as a part of one MSc. Thesis using transplant experiments as well as field data (correlation of morphological characters and selected habitat conditions). We also tested the ISSR molecular method. However, the results were compromised by relatively low amount of data. Thus, additional field data are needed and more reliable molecular methods (such as AFLPs) should be tested to address this problem.
Hybridization, polyploidy and their interactions (Centaurea as a model)
Origin of polyploids and their establishment in a maternal diploid population are among the most popular current research topics. Centaurea sect. Jacea is a suitable model group. Within a grant project from the Czech Science Foundation (2008–2011) we studied frequency of inter-ploidy crosses, the role of unreduced gametes and their frequency among different individuals, and other processes that involve cytotype coexistence in mixed populations. We also performed crossing experiments and compared the result with those from natural populations (such quantitative comparisons being only rarely performed).
The following research, e.g. as a student thesis may quantify the frequency of mixed populations and frequency of hybrids among them on a landscape level. Within the section Jacea, pairs of species of the same ploidy level as well as pairs of species of different ploidy levels may be studied and compared. Besides the polyploidy research, the results may also contribute to still open methodological question how to describe and quantify the "intensity" of hybridization.
Distribution mapping and determination keys
Within the PLADIAS project I contribute to mapping of vascular plants in Czechia: I collect field data for all species and prepare maps (based on revised herbarium specimens and a selection of reliable literature and database data) of species of Centaurea and several related genera (e.g. Arctium and Echinops), and of Ranunculus sect. Batrachium.
I also authored the genus Centaurea in the 2nd edition of the Key to the Czech Flora and 4th edition to the Key (Exkursionsflora) for Austria and the East Alps (both being prepared for print now). I will also contribute to the planned Key to the flora of Slovakia and one of the volumes of Flora of Slovakia.
Breeding systems in Sorbus
The genus Sorbus includes sexual as well as apomictic species (apomictic = seeds are formed without fertilization and are a genetic copy of the maternal individual). Such plant groups are often species rich and taxonomically difficult (other well-known examples are Rubus, Taraxacum or Hieracium). Apomictic Sorbus species have often small distributions (in an extreme case a single locality) and rank among a few endemics of the Czech flora. The aim of our study is not a taxonomic description (this has already been done in past decades) but understanding the reproduction biology of these unique plants – whether they are fully apomictic or if some residual sexuality is present. The residual sexuality seem to be an important evolutionary factor that allows hybridization and formation of new lineages (potential new species). The breeding system is inferred from ploidy levels of embryo and endosperm from mature seeds (flow cytometric seed screen, FCSS). Additional information on species origin and genetic variation may be analysed using molecular marker; microsatellites (SSR) are available for the genus Sorbus.
The study is done in collaboration with Martin Lepší (South Bohemian Museum, České Budějovice) and other experts. Currently, we offer one student thesis focussed on the peculiar alpine species Sorbus chamaemespillus.
Salix appendiculata in the Šumava Mts
Salix appendiculata is one of the most rare willow species in the Czech flora. Its occurrence in the Šumava Mts is an outpost of the distribution in the Alps. The aim of study is a revision of its populations in the Šumava Mts (population sizes, sex ratio) and detecting hybridization (i.e., possible genetic erosion) with other species. For the latter, we study morphology and genome sizes (using flow cytometry); use of molecular methods should be tested.
Flora of villages
Human settlements host a specific flora. Nowadays, structure of villages is changing due to changing life style of people, and the flora is changing accordingly. Some species newly appear while some that were common in the past become endangered and included into Red lists. This projects follow the long-time tradition of floristic studies of villages carried out by the members of South Bohemian branch of the Czech Botanical Society. In the last years, one MSc. Thesis focussed on the flora of villages on a climatic gradient from the Budějovická pánev Basin to Šumava Mts. and analysed factors that may determine the flora composition, such as altitude, village size and type (closed versus sparse, amount of abandoned land within a village, etc.) and type of surrounding landscape; the result are being prepared for publication.
