"Repeatome dynamics in the earliest evolutionary stages of apomictic plants"
J. Fehrer/P. Mráz Czech Science Foundation, 2017-2019
Abstract: Apomixis is tightly connected with hybridization and polyploidization. Despite a great potential in agriculture, the genetic mechanisms of apomixis are still poorly understood. Hybridization causes genetic instability including a restructuring of the repeatome, the fastest evolving part of plant genomes. Bursts of transposable elements due to hybridization-induced genomic shock may trigger a switch to apomixis. We will use sexual and apomictic parental Hieracium species in an extensive breeding program and compare artificial hybrids with natural apomicts of the same parentage / morphology as a model of hybrid speciation that may lead to the formation of apomictic lineages. Reproductive modes will be determined by flow cytometry, emasculation experiments and cytoembryological methods. We will analyze the repeatome by Next Generation Sequencing and use parental-specific repeats as cytogenetic markers to investigate genome repatterning following hybridization. The project will contribute to an understanding of mechanisms underlying the transition from sexual to apomictic reproduction.
"Remarkable cytotype co-existence of Pilosella echioides: the only known sexual system with triploid dominance"
P. Trávníček CSF 2013-2015
Abstract: Inter-cytotype interactions in mixed-ploidy populations are usually suppressed by various numbers of pre-zygotic isolation mechanisms because of the impact of strong post-zygotic barriers (e.g. triploid block). Contrary to this common scenario, our model group Pilosella echioides is supposed to be the first candidate of the system in plants with a strictly sexual mode of reproduction that behave differently. It is hypothesized that co-existence of up to five cytotypes of Pilosella echioides is mainteined by free mating interactions and absence of both pre- and post-zygotic isolation barriers. Moreover, occasional triploid dominace in mixed-ploidy populations marks a uniqueness of the system and deserves special attention.
"Phylogeny of subtribe Hieraciinae (Asteraceae) - a model example of contrasting evolutionary strategies in closely related lineages"
J. Chrtek/P. Bureš CSF 2010-2013
Abstract: Evolutionary patterns in related lineages with contrasting ploidy and reproductive mode are crucial topics of contemporary biology. Our model system, subtribe Hieraciinae (Asteraceae), combines features that are unique in plants: two different kinds of apomixis and the presence of a sexual sister genus. A multigene phylogeny based on complete or (in apomictic groups) representative sampling will serve as a backbone for interpretations on 1) historical biogeography: localization of evolutionary and diversity centres of the subtribe (connections of Iberian and North African floras, Macaronesian colonization, migration routes between Eurasia and North America); 2) genome size: diversification and evolution, responsible mechanisms at the genomic level (diversity and quantity of transposable elements), relation to ecogeographical and biological factors, adaptive role; 3) karyotype evolution: localization of transposable elements, especially in connection with the Avoidance of Meiosis Locus (LOA), and their potential influence on reproductive isolation and the origin of apomixis.
"Phylogeography and cytotype structure of Hieracium intybaceum (Asteraceae)"
J. Zahradníček GA CU 2009-2011
Abstract: Effects of climate changes on the genetic structure of populations and changes in distribution areas (fragmentation, retreat to lower altitudes and recolonization, differentiation, surviving in refugia) in the recent history of alpine species belong to very timely research areas as they contribute to our knowledge of the phylogeny in large mountain ranges. Hieracium intybaceum (Asteraceae) is a well defined, karyologically differentiated species (di-, tri- and tetraploids) that grows on silicate rocks in high altitudes in the Alps, Vosges and Schwarzwald Mts. Though traditionally recognised as a part of genus Hieracium (subgenus Hieracium), molecular data suggest an older isolated lineage; there are most likely some differences in reproduction, too. The proposed combination of molecular and flow-cytometry methods along with morphometrics and reproduction experiments will help to elucidate the phylogeographical pattern within and among cytotypes and the origin of new polyploid cytotypes. It can also contribute to the knowledge of main refugia and migration routes during the recolonization of high altitudes. Understanding the cytotype structure in the distribution area and ecological demands of particular ploidy levels along with the knowledge of reproduction can clarify the mechanisms helping the polyploid complexes to survive and evolve.
"Evolutionary processes within populations of facultative apomicts"
F. Krahulec/B. Trávníček CSF 2008-2012
Abstract: Two groups with facultative apomicts will be studied: the degree of residual sexuality is known at least at some members of Hieracium subgen. Pilosella, its degree at Rubus is estimated from population composition. The cpDNA will be studied at Hieracium hybrids in two different regions to test the possibility of extrapolation of findings on the high role of apomictic mothers for the formation of hybrids. The cytotype structure of Rubus populations will include also local types not studied yet. The importance of residual sexuality will be studied by analysis of progeny from experimental hybridisations as well as at selected mothers in the field; the results will confronted with the situation within populations. We shall use mostly experimental hybridisation of different cytotypes in Hieracium, and molecular markers in Rubus. We shall test the role of diploid hybrids as a switch for polyploidisation due to more often formation of unreduced gametes than at diploid parents with regular meiosis.
"Microevolutionary processes in marginal populations of plants with ploidy heterogeneity: Hieracium echioides as a model system"
P. Trávníček GA ASCR 2008-2010
Abstract: The project is aimed at elucidating diversity and evolutionary dynamics of marginal populations with ploidy polymorphism in a model diploid-polyploid plant Hieracium echioides. A number of interacting techniques of contemporary plant biology will be used, including molecular approaches (AFLP, cpDNA sequencing and PCR-RFLP) and flow cytometry. Three umbrella questions will be addressed: i) ploidy distribution at various spatial scale across Central Europe; ii) genetic diversity at population level with respect to cytotype composition, population size, and degree of isolation; and iii) origin of polyploids in the area investigated. The gathered data will provide novel and multifaceted insights into micro-evolutionary processes that shape variation in populations at the edge of their distribution and will contribute to a better understanding of the role of marginal populations in genesis, maintenance, and dynamics of diversity (of practical value in conservation biology).
"A molecular biosystematic study of the section Pilosellina and evolutionary aspects of its glacial origin"
T. Urfus GA CU 2008-2010
Abstract: The present project concerns a molecular biosystematic study of members of sect. Pilosellina (genus Pilosella Vaill., Asteraceae). The authors' objective is to determine the values of selected biosystematic characteristics (i.e., ploidy level, genome size, mode of reproduction) in a vast array of taxa and cytotypes from all over Europe and to address inter- and intraspecific relationships in this taxonomically rather troublesome section by morphometric analyses. The molecular part of the project is aimed at scrutinizing chloroplast haplotypes, their species specificity and geographic distribution. On the basis of the distribution of chloroplast haplotypes in the study area, more refined hypotheses will be formulated about the evolutionary and speciation processes taking place in the section Pilosellina in connection with the hypothetical distribution of the taxa during the glacial period. A synthesis of the data from both methodical approaches will be performed to determine the evolutionary relationships between the taxa under investigation and especially to look into the origin of Pilosella officinarum F. W. Schultz et Sch. Bip., which is the most common species of the genus in Europe as well as a remarkably invasive alien species in many parts of the world.
"Microevolutionary aspects of residual sexuality in plant apomicts: detection, rate and manifestation in populations of Hieracium subgen. Pilosella"
A. Krahulcová CSF 2007-2009
Abstract: Facultative apomixis combines usually dominant asexual seed production and occasional hybridization of maternal plants (residual sexuality). Advantages of both apomixis (conservation and spread of adapted genotypes) and sexuality (increase of progeny variation by recombination and segregation) often contribute to invasion of such biotypes to new habitats. Besides sexual biotypes, also facultative apomicts do hybridize (as seed or pollen parents) in our model system of Hieracium subgenus Pilosella. Thus, both recent hybrids and already stabilized hybridogenous taxa occur in nature. The project is aimed at 1) detection and quantification of hybrid progeny of apomitic mothers after experimental crosses and open pollination in the field, and 2) evaluation of progeny variation generated by apomictic versus sexual mothers in selected mixed populations. Comparison to actual population structures in the wild will provide an estimate of establishment of new biotypes originated in the same way and elucidate the role of natural selection.
"Molecular Phylogeny and Evolutionary Trends in Hieracium (Asteraceae, Lactuceae)"
J. Chrtek, J. Fehrer CSF 2005-2007
Abstract: Hieracium, representing one of the world's most species-rich plant genera, belongs to the most intricate groups of vascular plants with a highly complicated pattern of morphological variation as well as diversity in breeding systems and strategies (sexuals and different kinds of apomicts).
A molecular phylogeny based on three genetic markers - the chloroplast trnT-trnL intergenic spacer, the nuclear ribosomal ITS region and a single or low-copy nuclear gene - shall be established. Based on previous work covering subgenus Pilosella, the study will focus on the other subgenera, Hieracium and Chionoracium (Stenotheca), attempting to cover their entire genetic diversity at a coarse level as a prerequisite for further, more detailed studies. Relationships at infrageneric and intratribal level shall be elucidated, patterns of speciation inferred and correlated to changes in DNA content, reproductive systems, geographic distribution etc. The validity of present sectional and generic classifications and of the existing contradictory species concepts will be assessed.
The single or low-copy nuclear gene system to be established during our study is also expected to provide a new marker for Lactuceae/Asteraceae phylogenetic research.
The results will serve as a framework for further evolutionary studies and taxonomic revisions.
"Development of single copy nuclear markers for the Asteraceae"
K. Krak, J. Fehrer EU 2006
Abstract: The main objective of the project is to identify single or low- copy nuclear markers for its potential use in phylogenetic analyses in the family Asteracea at different taxonomic levels (genus to tribe). For the candidate markers Asteraceae specific primers will be developed and the variability of the target regions will be screened in a selection of diploid representatives, covering a spectrum of most distinct tribes of the family. The utility of the developed markers will be assessed (i.e. identification of pseudogenes and paralogs, intron-exon relation, genetic variability) at different taxonomic levels.
"The influence of environmental parameters on the genetic structure of the young agamic complex: Hieracium subgen. Pilosella"
F. Krahulec GA ASCR 2002-2006
Abstract: Agamic complexes form a substantial part of central European flora: in addition to old groups there are also young (early mature) complexes, developing under present conditions. Hieracium subgen. Pilosella consists of basic species, stabilized hybrids, as well as young hybrids originating at present. Sympatric taxa give rise to new types by hybridization with probable introgression with progeny diverse in reproduction modes and ploidy. The potential of the complex will be evaluated by intentional crosses and will be compared with types arising and existing in nature. The selection will be studied at different phases (seed formation and germination, seedling establishment, growth of adult plants). The analysis of within and among population variation will explain the processes (introgression, multiple origin of hybrids) and the existing pattern.
"Monograph of Hieracium s.str. (Compositae) in the Western and Ukrainian Eastern Carpathians"
J. Chrtek CSF 2003-2005
Abstract: Mountain taxa of the subgen. Hieracium belong to the most interesting members of the genus. They might serve as model groups in studies aimed at local differentiation, microevolution in isolated populations, gene flow in agamic complexes, or more generally at historical biogeography and florogenetic patterns in European mountains. The main aim is to complete draft treatment of mountain Hieracium taxa in the studied area. Some data collected in the course of the study will be further used in thinking about differentiation and speciation processes in this genus.
"Genome size - a key to the knowledge of relationships among Central European taxa from Hieracium subg. Pilosella"
J. Suda, A. Krahulcová, R. Rosenbaumová & T. Peckert GA UK (GA CU) 2003-2004
Abstract: The project was targeted on flow-cytometric determination of genome sizes (2C- and 2Cx-values) and proportions of AT / GC base pairs in selected species from Hieracium subg. Pilosella (16 taxa, 29 cytotypes, 225 individuals representing both "basic" and hybridogenous types). The homoploid genome size in "basic" species varied from 1.72 pg to 2.16 pg, amounting to 25.5 % difference. Cx-values of hybridogenous taxa were located between the estimates for their putative parents, although often closer to the parental species with lower DNA amount. Certain tendency towards a reduction of Cx-values was detected in higher cytotypes of multiploid species. Only very low intraspecific variation in genome size occurred in "basic" species, slightly higher variation (up to 5.7 %) found in hybridogenous taxa might support their multiple independent origins. The ratio of AT / CG bases was stable within all the group (maximum difference 1.2 %). In summary, genome size data yield useful information for the evaluation of taxa relationships, and facilitate reliable determination of several closely related species.
"Biodiversity, genetic structure and differentiation of Hieracium species in the border area Saxony/Czech Republic/Poland"
J. Fehrer, S. Bräutigam GSF (DFG) 1999-2001
Abstract: Based on morphological work on hawkweeds (Hieracium subgenus Pilosella), species of the three-boarder region of Saxony, Poland and the Czech Republic shall be analyzed by molecular methods in order to determine their diversity, relationships and the correlation between morphological and genetic variability. As many Hieracium species are apomictic and thus represent model organisms for the transition between reticulate and bifurcate evolution, the influence of the reproduction mode on the population structure shall be elucidated. Using two morphological series as examples, questions on the delimitation of species, infraspecific and geographical structure as well as on the influence of hybridization and introgression on speciation shall be addressed. The observed patterns shall be related to differences in the species' mode of reproduction, distribution, ploidy level and ecology.
"Plant community as a selection factor within hybridogenous complex: Hieracium subgen. Pilosella in meadows of the Krkonoše Mts."
A. Krahulcová GA ASCR 1998-2000
Abstract: The ecological and biosystematic studies devoted to the closely related species and hybrid complexes allow us to understand better the mechanisms of their evolution and success in the selective processes. The detailed examination of selected cases is also important with respect to recent emphasis on biodiversity protection. The members of Hieracium subg. Pilosella may serve as a unique case where recent hybridization is connected with the formation of apomictic stabilized types which characters may be related to habitat factors. Plant community may function as habitat factor; its structure we consider as selective factor influencing the size of plants and the type of clonal growth. The research will be be focused on conditions allowing the hybridization and hybrid establishment, study of their reproductive systems, and detailed comparison of apomictic and sexual cytotypes.
"Differentiation of high mountain taxa of vascular plants - model study of Hieracium (Compositae) in Central and Eastern Europe"
J. Chrtek CSF 1996-1998
Abstract: Extensive set of data on morphological variation, chromosome numbers, breeding systems, geographic distribution and genetic structure (RAPD and allozyme analyses) in selected taxa of Hieracium sect. Alpina (Compositae) was gathered. Most of data refers to the Hieracium alpinum, H. fritzei and H. nigrescens species groups. Taxonomic treatments of the H. alpinum and H. fritzei groups in the Sudeten Mts. and the Western and Ukrainian Eastern Carpathians, together with hypotheses concerning differentiation processes in the section Alpina are the principal outputs. In Hieracium alpinum (s. str.), two vicariant cytotypes (diploid and triploid) were found. While the triploid one has been reported from many sites throughout the nearly all arcto-alpine distribution area, diploid cytotype was found as a new one for the Eastern Carpathians (where triploids most probably did not occur). Sexual reproduction and high genetic variation at both intra- and interpopulation levels were detected in the diploids. On the other hand, triploids are agamospermous. Nevertheless, some genetic variation showing geographic pattern was also found in this cytotype. Other studied species are polyploid (3x, 4x, very rarely 5x), genetically more or less uniform (except of H. pinetophilum and H. crassipedipilum, both the H. fritzei group). Occurrence of unique alleles in both H. slovacum and H. halleri indicates their close reletionships.