Abstracts

Chrtek	1994	Chromosome numbers in selected Hieracium species in the Krkonoše Mts. (the West Sudeten)
Abstract: Chromosome numbers are given of 15 species of the genus Hieracium L. s str., representing seven species groups (in the sense of Flora Europaea, roughly corresponding to Zahn's ''species principales'') from the Krkonoše Mts., N. Bohemia and SW Poland. For the first time, chromosome numbers are reported for H. melanocephalum Tausch (2n=27), H. tubulosum Tausch (2n=36), H. schustleri Zlatník (2n=36), H. fritzei F. Schultz (2n=27), H. rohlenae Zlatník (2n=27), H. nigrescens Willd. (2n=36), H. decipiens Tausch (2n=36), H. atrellum Juxip in Shishkin et Bobrov (2n=27), H. subnigrescens (Fries ex Norrlin) Dahlst. (2n=36), H. sudeticum Sternb. (2n=36), H. pedunculare Tausch (2n=36), H. glandulosodentatum Uechtr. (2n=36), H. wimmeri Uechtr. (2n=27). In Hieracium alpinum L. s. str. the number 2n=27 has been confirmed. The results show a high proportion of tetraploid taxa; no diploids have been found.
Chrtek	1996	Chromosome numbers in selected Hieracium species (Compositae) in the Sudeten Mts and West and Ukrainian East Carpathians.
Abstract: Chromosome numbers are reported for 18 collections representing ten taxa of Hieracium L. Chromosome numbers are reported for the first time for H. chlorocephalum Uechtr. (2n = 4x = 36), H. stygium Uechtr. (2n = 36), H. silesiacum Krause (2n = 36), H. corconticum Knaf fil. ex Čelak. (2n = 27), H. conicum Arvet-Touvet (2n = 18), and H. chrysostyloides (Zahn) Chrtek jun. (2n = 5x = 45). The pentaploid chromosome number appears to be only the second count for any taxon of Hieracium s.str. above the level of tetraploid. In H. prenanthoides Vill. 2n = 27 was ascertained in populations from the Krkonoše Mts. (West Sudeten Mts.) and Vysoké Tatry Mts. (Western Carpathians). The mountain population of H. schmidtii Tausch from the Krkonoše Mts. (West Sudeten Mts.) was found to be triploid (2n = 27). In H. transsilvanicum Heuff. the number 2n = 18 was confirmed, and in H. nigritum Uechtr. 2n = 36 was ascertained.
Chrtek	1996	Rozšíření Hieracium halleri (okruh H. alpinum) v Západních Karpatech. [Distribution of Hieracium halleri (Hieracium alpinum agg.) in the Western Carpathians].
Abstract: The paper summarizes the geographical distribution of Hieracium halleri Vill. (Hieracium sect. Alpina, H. alpinum group) in the Western Carpathians (N Slovakia, S Poland). The species is confined to the subalpine and alpine belts of the Západné Beskydy Mts (rare), the Velká Fatra Mts (rare), the Tatry Mts (widespread) and the Nízke Tatry Mts (scattered). The differences between H. halleri and closely related H. alpinum s.str. ale briefly mentioned.
Chrtek	1997	Hieracium decipientiforme (Wołoszczak et Zahn) Šljakov (the Hieracium nigrescens group) - an interesting species of the Ukrainian Carpathians.
Abstract: Hieracium decipientiforme (Wołoszczak et Zahn) Šljakov, most probably an endemic taxon of the Ukrainian Carpathians, was found to be agamospermous tetraploid (2n=36). It occurs in mountain meadows, open places in krummholz stands and in subalpine grasslands in altitudes 1580-1900 m a.s.l. in the Gorgany Mts, the Čornohora Mts and the Marmaros Mts. Important distinguishing characters and relations to other related species groups are briefly discussed.
Chrtek	1997	Taxonomy of the Hieracium alpinum group in the Sudeten Mts. and the West and Ukrainian East Carpathians.
Abstract: A taxonomic revision of the Hieracium alpinum group (sensu Flora Europaea) in the Sudeten Mts., the West and the Ukrainian East Carpathians is provided. Six species ate distinguished in the area studied, viz. Hieracium alpinum, H. halleri, H. augusti-bayeri, H. melanocephalum, H. tubulosum, and H. schustleri. H. alpinum occurs throughout the mountain ranges studied, three other taxa are endemic to the Sudeten Mts. (H. melanocephalum, H. tubulosum, H. schustleri), one is confined to the West Carpathians (H. halleri, in addition to the Alps) and one is endemic to the Ukrainian East Carpathians (H. augusti-bayeri). A diploid cytotype (2n=18) was ascertained in H. alpinum from the Ukrainian East Carpathians and the same chromosome number was found for H. augusti-bayeri. An agamospermous mode of reproduction was confirmed for the triploid cytotype of H. alpinum, the triploid H. melanocephalum and H. halleri and the tetraploids H. tubulosum and H. schustleri; the diploid taxa were found to be sexual. Pollen production in diploid taxa is high and pollen grains are homogeneous in size; triploid species, as well as tetraploid H. tubulosum, do not produce pollen; tetraploid H. schustleri has pollen grains of variable size. Data on the ecology and distribution of the species are also given.
Chrtek & Marhold	1996	Lectotypification of the name Hieracium alpinum subsp. augusti-bayeri Zlatník (Compositae).
Abstract: The original material connected with the name Hieracium alpinum subsp. augusti-bayeri Zlatník, Práce Morav. Přír. Společ. 7/8:1-6, 1932, ut "Augusti Bayeri" is discussed and the lectotype of this name is designated. The authors consider as most appropriate the treatment on the level of species and the name in the appropriate new status is published.
Chrtek & Marhold	1998	Taxonomy of the Hieracium fritzei group (Asteraceae) in the Sudeten Mts. and the West Carpathians (Studies in Hieracium sect. Alpina II.)
Abstract: The Hieracium fritzei group is represented in the Sudeten mountains and the West Carpathians in the Czech Republic, Poland and Slovakia by the following species: H. fritzei F. Schultz (2n=27), H. uechtritzianum G. Schneid. (2n=?), H. schneiderianum Zlatník (2n=27), H. rohlenae Zlatnik (2n=27), H. nigrostylum Zlatník (2n=?), H. slovacum Chrtek jun. (2n=36), H. crassipedipilum (Pawł. & Zahn) Chrtek jun. (2n=36), H. pinetophilum (Degen & Zahn) Chrtek jun. (2n=27), and H. krivanense (Woł. & Zahn) Shlyakov (2n=?). For each of these taxa the description, synonymy, data on their distribution and representative specimens are provided. In several cases lecto- or neotypes for the correct names and synonyms are designated.
Chrtek & Plačková	2005	Genetic variation in Hieracium alpinum (Asteraceae) in the Krkonoše Mts (West Sudeten Mts, Czech Republic).
Abstract: Five enzyme systems (EST, LAP, PGM, SKD, 6PGDH) were studied in three populations of triploid (2n = 27) agamospermous Hieracium alpinum s. str. (H. alpinum subsp. alpinum) in the Krkonoše Mts (West Sudeten Mts, Czech Republic). Altogether, five different multilocus genotypes were found and both intra- and between-population variation were detected. Within-population variability was found in all the studied populations. Mean population diversity Gsp = 0.52, component of total variance attributed to variation among population Gst = 0.09). Chromosome number 2n = 27 was confirmed in all plants used in enzyme studies. Putative origins of genetic variation are briefly discussed.
Chrtek et al.	2004	Chromosome numbers in selected species of Hieracium s.str. (Hieracium subgen. Hieracium) in the Western Carpathians.
Abstract: Chromosome numbers of 23 species (including subspecies) of Hieracium s. str. from the Western Carpathians are presented. First chromosome numbers are reported for Hieracium kuekenthalianum (= H. tephrosoma, 2n = 36), H. praecurrens (2n = 27) and H. virgicaule (2n = 27); first counts from the Western Carpathians are given for H. atratum (2n = 27), H. bifidum (2n = 27, 36), H. carpathicum (2n = 36), H. inuloides (2n = 27), H. jurassicum (2n = 27), H. macilentum (= H. epimedium, 2n = 27), H. nigritum (2n = 36), H. pilosum (= H. morisianum, 2n = 27) and <>H. silesiacum (2n = 36). New ploidy level (tetraploid, 2n = 36) is reported for H. bupleuroides, hitherto published counts refer only to triploids (2n = 27). Previously published chromosome numbers were confirmed for several other species, i.e. H. alpinum (s.str., 2n = 27), H. bupleuroides (2n = 27), H. crassipedipilum (H. fritzei group, 2n = 27, 36), H. lachenalii (2n = 27), H. murorum (2n = 27), H. prenanthoides (2n = 27), H. racemosum (2n = 27), H. sabaudum (2n = 27), H. slovacum (H.fritzei group, 2n = 36), and H. umbellatum (2n = 18). Triploids and tetraploids predominate, diploids (2n = 18) were found in H. umbellatum. A comprehensive list of previously published chromosome numbers in Hieracium s. str. from the Western Carpathians is provided.
Chrtek et al.	2002	Hieracium silesiacum Krause [Hieracium sparsum subsp. silesiacum (Krause) Zahn] v Západních Karpatech.
Abstract: Summary of published localities together with discoveries of new sites of Hieracium silesiacum Krause is presented. The hitherto known occurrence in the Western Carpathians is confined to the Nízke Tatry Mts., western part of the Vysoké Tatry Mts. and to both sides (Slovak and Polish) of the Západné Tatry Mts (Tatry Zachodnie Mts). Morphological comparison has been made between Western Carpathian plants and those of the Hrubý Jeseník Mts (Czech Republic), both referable to H. silesiacum. The paper also includes notes on ecology and habitat preferencies.
Chrtek et al.	2007	Chromosome numbers and DNA ploidy levels of selected species of Hieracium s. str. (Asteraceae)
Abstract:Chromosome numbers and /or ploidy levels are reported for 44 species and subspecies of Hieracium s.str. from the following European countries: Andorra, Austria, Bulgaria, Czech Republic, France, Italy, Montenegro, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland and Ukraine. The chromosome numbers/DNA ploidy levels of H. bocconei (2n ~ 4x), H. bupleuroides subsp. leviceps (2n = 27), H. caesioides subsp. caesioides (2n = 27), H. basifolium (H. caesium agg., 2n = 36), H. plumbeum (H. caesium agg., 2n = 36), H. glaucum subsp. nipholepium (2n = 27), H. gouanii (2n = 18), H. gymnocerinthe (2n = 27), H. ramondii (2n = 27), H. recoderi (2n = 18), H. stelligerum (2n = 18), and H. tomentosum (2n = 18, 2n ~ 2x, 2n ~ 3x) were determined for the first time. New ploidy levels are reported for H. cerinthoides s.str. (2n = 27), H. humile (2n = 36), and H. tommasinianum (2n = 27).
Chrtek et al.	2009	Genome size in Hieracium subgenus Hieracium (Asteraceae) is strongly correlated with major phylogenetic groups.
Abstract: Background and Aims Hieracium subgenus Hieracium is one of the taxonomically most intricate groups of vascular plants, due to polyploidy and a diversity of breeeding systems (sexuality vs. apomixis). The aim of the present study was to analyse nuclear genome size in a phylogenetic framework and to assess relationships between genome size and ploidy, breeding system and selected ecogeographic features. Methods Holoploid and monoploid genome sizes (C- and Cx-values) of 215 cultivated plants from 89 field populations of 42 so-called ‘basic’ Hieracium species were determined using propidium iodide flow cytometry. Chromosome counts were available for all analysed plants, and all plants were tested experimentally for their mode of reproduction (sexuality vs. apomixis). For constructing molecular phylogenetic trees, the external transcribed spacer region of nuclear ribosomal DNA was used. Key Results The mean 2C values differed up to 2.37-fold among different species (from 7.03 pg in diploid to 16.67 in tetraploid accessions). The 1Cx values varied 1.22-fold (between 3.51 and 4.34 pg). Variation in 1Cx values between conspecific (species in a broad sense) accessions ranged from 0.24% to 7.2%. Little variation (not exceeding the approximate measurement inaccurracy threshold of 3.5%) was found in 33 species, whereas variation higher than 3.5% was detected in seven species. Most of the latter may have a polytopic origin. Mean 1Cx values of the three cytotypes (2n, 3n and 4n) differed significantly (average of 3.93 pg in diploids, 3.82 pg in triploids and 3.78 pg in tetraploids) indicating downsizing of genomes in polyploids. The pattern of genome size variation correlated well with two major phylogenetic clades which were composed of species with western or eastern European origin. The monoploid genome size in the ‘western’ species was significantly lower than in the ‘eastern’ ones. Correlation of genome size with latitude, altitude and selected ecological characters (light and temperature) was not significant. A longitudinal component was only apparent for the whole data set, but absent within the major lineages. Conclusions Phylogeny was the most important factor explaining the pattern of genome size variation in Hieracium sensu stricto, species of western European origin having significantly lower genome size in comparison with those of eastern European origin. Any correlation with ecogeographic variables, including longitude, was outweighed by the divergence of the genus into two major phylogenetic lineages.
Fehrer et al.	2007a	Incongruent plastid and nuclear DNA phylogenies reveal ancient intergeneric hybridization in Pilosellahawkweeds (Hieracium, Cichorieae, Asteraceae).
Abstract: Phylogenetic relationships for Hieracium subgen. Pilosella were inferred from chloroplast (trnT-trnL, matK) and nuclear (ITS) sequence data. Chloroplast markers revealed the existence of two divergent haplotype groups within the subgenus that did not correspond to presumed relationships. Furthermore, chloroplast haplotypes of the genera Hispidella and Andryala nested each within one of these groups. In contrast, ITS data were generally in accord with morphology and other evidence and were therefore assumed to reflect the true phylogeny. They revealed a sister relationship between Pilosella and Hispidella and a joint clade of Hieracium subgenera Hieracium and Chionoracium (Stenotheca) while genus Andryala represented a third major lineage of the final ingroup cluster. Detailed analysis of trnT-trnL character state evolution along the ITS tree suggested two intergeneric hybridization events between ancestral lineages that resulted in cytoplasmic transfer (from Hieracium/Chionoracium to Pilosella, and from the introgressed Pilosella lineage to Andryala). These chloroplast capture events, the first of which involved a now extinct haplotype, are the most likely explanation for the observed incongruencies between plastid and nuclear DNA markers.
Fehrer et al.	2007b	Evolutionary aspects in Hieracium subgenus Pilosella
Abstract: The hawkweed subgenus Pilosella (Cichoriae, Asteraceae) is known for its notoriously complicated taxonomic structure due to ongoing reticulate evolution, combined with a facultatively apomictic mode of reproduction and allopolyploidy. Recently, molecular approaches at clone, population and species level have begun to shed some light on these processes. Geneflow across ploidy levels is common, and parental species of hybridogenous taxa often include apomicts, even as seed parents. Sexual taxa (diploid or polyploid) usually show high genetic variability. Apomicts vary from near clonality across large geographic distances to multiple origins on a small scale. Selection plays an important role in the establishment and fixation of particular cytotypes/genotypes in the field. A broad range of reproductive strategies and frequent hybridizations, combined with good colonization properties under low-competition conditions in their native Eurasian environment, provide an enormous evolutionary potential, which is also reflected by the group’s strong invasive behavior on other continents. Phylogenetic analyses reveal that Pilosella chloroplast haplotypes form two major groups with no correlation to morphology and taxonomic grouping whereas nuclear DNA sequences reflect species relationships. Incongruencies between molecular markers imply two ancient hybridization events predating most of the speciation observed in the subtribe Hieraciinae: one between the Hieracium/Chionoracium subgenera ancestor and partly differentiated Pilosella, and a subsequent event between this introgressed Pilosella lineage and the closely related Andryala genus ancestor. Distribution areas and numbers of Pilosella species belonging to one or the other haplotype group as well as the extinction of intermediate haplotypes suggest their differentiation in different glacial refuges. The introgressed Pilosella lineage gave rise to the majority of recent species which show an increased ecological amplitude. Secondary contact generated a large geographic overlap of haplotype groups with no apparent reproductive isolation between species. Phylogenetic, developmental genetic, biogeographic, and mechanistic aspects of the origin of polyploidy and apomixis in Pilosella are discussed, and guidelines for dealing with natural populations of apomictic groups are suggested. A comprehensive list of adventive Pilosella species, an updated map of their native range, and a preliminary map of Andryala distribution are provided.
Fehrer et al.	2005	Evolution, hybridisation, and clonal distribution of apo- and amphimictic species of Hieracium subgen. Pilosella (Asteraceae: Lactuceae) in a Central European mountain range.
Abstract: Hieracium subgenus Pilosella is an extremely difficult group taxonomically, as it combines apomixis with extensive hybridisation. The resultant vast number of morphological forms and cytotypes, which are extremely difficult to distinguish, has in the past deterred study of their microevolutionary relationships. We present here a multidisciplinary approach combining molecular techniques (DNA fingerprinting and the analysis of chloroplast DNA) with morphological-taxonomic studies, cultivation, experimental hybridisation, analysis of ploidy level and mode of reproduction. In a selected area, a transsect in the three-border land of Germany, the Czech Republic and Poland, eight species of a hybridogenous complex representing two morphological series were studied in detail at the clone, population and species level. Proper assignment of individual plants and populations to apomictic clones was achieved and provided the basis for further analysis. Different levels of variability were found in the apomictic species: from near uniformity across the study area to variability within the locality. These differences were related to the different ages and histories of the respective taxa. A partial biogeographic isolation between two mountain regions was suggested by the distribution of widespread clones. The chloroplast haplotypes formed two major groups that showed no correlation to geographic distribution, but matched the species' delimitation except in the case of a recent hybrid which was obviously produced by reciprocal crosses between parental species of different haplotype groups. Apart from that, each species including the intermediates possessed one haplotype indicating unidirectional transmission of the chloroplast DNA, despite multiple origins of most apomicts. Moreover, in the majority of the cases examined, the facultative apomict rather than the sexual species acted as seed parent. Thus, the residual sexuality of the apomicts seems to play a larger role in the speciation of this group than hitherto assumed. This study leads to a much better understanding of a variety of aspects of the group and will serve as a basis for future analyses.
Fitze & Fehrer	2000	PCR-RFLP studies of non-coding chloroplast DNA in European Hieracium subgen. Pilosella.
Abstract: As part of an ongoing project about the biodiversity, genetic structure and differentiation of Hieracium, subgenus Pilosella, the relationships of the species occurring in the borderland of Saxony (Germany), the Czech Republic and Poland have been investigated by PCR-RFLP analysis of the chloroplast trnT-trnF spacer region. As outgroups, species of Hieracium subgen. Hieracium and Chionoracium as well as of the closely related genus Andryala were included. The target region was PCR-amplified using the universal primers described by TABERLET et al. (1991. Plant Mol. Biol. 17: 1105-1109). Amplification products were submitted to restriction enzyme digestions. Out of 15 enzymes tested, only AluI, MboI, BclI, BglII and EcoRI yielded differences between the species and were therefore used for further analysis. No changes in restriction sites, but only length variations were observed. Fragment sizes were determined. Identical haplotypes were observed for representatives of the following species: H. cymosum/H. glomeratum, H. pilosella/H. piloselliflorum, H. bauhini/H. leptophyton, H. lactucella/H. floribundum/H. aurantiacum, the three subspecies of H. caespitosum (madarum, caespitosum and colliniforme), H. piloselloides ssp. obscurum/H. echioides ; H. sabaudum/H. umbellatum, H. schneiderianum/H. alpinum. In three cases (H. glomeratum, H. piloselliflorum, H. leptophyton), the species have previously been considered as presumed early generation hybrids based on their morphology, occurrence, DNA content and ploidy levels. Because of the maternal inheritance of the chloroplast DNA, evidence for the seed parent is now suggested. The result is in accordance with the assumed modes of reproduction. H. floribundum - although being a "main" species in the sense of NÄGELI & PETER (1885. Die Hieracien Mittel-Europas, Piloselloiden. München) - was suggested to be a hybrid between H. lactucella and H. caespitosum (KRAHULCOVÁ & KRAHULEC, 1999. Preslia 71: 217-234). Usually, the few sexual species (H. pilosella - tetraploid, H. cymosum and H. lactucella - diploid) served as the seed parent. In the case of H. bauhini, however, an unreduced chromosome set of this pentaploid apomict might have been pollinated by diploid (reduced) pollen of H. pilosella, yielding the heptaploid hybrid H. leptophyton. For the remaining haplotypes, no direct evidence from other sources is as yet available to explain the patterns. More data are needed to elucidate these relationships and homology of the length variations has to be established by DNA sequencing. Generally, the Hieracium species of all subgenera as well as of closely related Andryala showed only little sequence variation as judged by the missing RFLPs. Insertions/deletions seem to account for most variation as has also been shown recently for other Asteraceae of the Lactuca tribe (VIJVERBERG & BACHMANN, 1999. Amer. J. Bot. 86: 1448-1463). However, most variation was found between trnT-trnL in our case, but not in the trnL-trnF part of the amplified fragment, as indicated by a restriction site map and partial DNA sequencing.
Koltunow et al.	2011	Sexual reproduction is the default mode in apomictic Hieracium subgenus Pilosella, in which two dominant loci function to enable apomixis.
Asexual seed formation, or apomixis, in the Hieracium subgenus Pilosella is controlled by two dominantindependent genetic loci, LOSS OF APOMEIOSIS (LOA) and LOSS OF PARTHENOGENESIS (LOP). We examined apomixis mutants that had lost function in one or both loci to establish their developmental roles during seed formation. In apomicts, sexual reproduction is initiated first. Somatic aposporous initial (AI) cells differentiate near meiotic cells, and the sexual pathway is terminated as AI cells undergo mitotic embryo sac formation. Seed initiation is fertilization-independent. Using a partially penetrant cytotoxic reporter to inhibit meioisis, we showed that developmental events leading to the completion of meiotic tetrad formation are required for AI cell formation. Sexual initiation may therefore stimulate activity of the LOA locus, which was found to be required for AI cell formation and subsequent suppression of the sexual pathway. AI cells undergo nuclear division to form embryo sacs, in which LOP functions gametophytically to stimulate fertilization independent embryo and endosperm formation. Loss of function in either locus results in partial reversion to sexual reproduction, and loss of function in both loci results in total reversion to sexual reproduction. Therefore, in these apomicts, sexual reproduction is the default reproductive mode upon which apomixis is superimposed. These loci are unlikely to encode genes essential for sexual reproduction, but may function to recruit the sexual machinery at specific time points to enable apomixis.
Krahulcová et al.	1999	Autogamy in Hieracium subgen. Pilosella.
Abstract: The presence of autogamy in Hieracium subgen. Pilosella is reported for diploid H. lactucella and tetraploid H. pilosella. Self-compatibility is induced under the influence of pollen from another species (mentor effects).
Krahulcová & Krahulec	1999	Chromosome numbers and reproductive systems in selected representatives of Hieracium subgen. Pilosella in the Krkonoše Mts (the Sudeten Mts).
Abstract: Chromosome numbers and reproductive system are given for the following taxa of Hieracium subgen. Pilosella occurring in the Krkonoše Mts.: H. pilosella L. (2n=36, sexual), H. lactucella Wallr. (2n=18, sexual), H. caespitosum Dumort. (2n=36, the mode of reproduction unknown), H. aurantiacum L. (2n=36, apomictic), H. schultesii F.W. Schultz (2n=36, sexual; 2n=45, apomictic), H. macrostolonum G. Schneider (2n=54, the mode of reproduction unknown), H. glomeratum Froel. (2n=36, 45, both apomictic), H. floribundum Wimm. et Grab. (2n=36, apomictic), H. iseranum Uechtr. (2n=36, apomictic), H. apatelium Nägeli et Peter (2n=36, both sexual and apomictic; 2n=45, apomictic), H. piloselliflorum Nägeli et Peter (2n=36 the mode of reproduction unknown; 2n=45, 44, apomictic; 2n=54, apomictic), H. stoloniflorum Waldst. et Kit. (2n=54, apomictic), H. rubrum Peter (2n=54, apomictic). Chromosome numbers are reported for the first time for H. apatelium, H. iseranum, and H. piloselliflorum, a new chromosome number was determined for H. macrostolonum and H. schultesii. The group of species (H. caespitosum, H. glomeratum, H. floribundum, H. iseranum) has been found to have a single long marker chromosome in the karyotype; this fact supports the view of their relationship. The mode of reproduction is here examined for the first time in polyploid hybridogenous species H. iseranum, H. apatelium, H. piloselliflorum, H. stoloniflorum, H. rubrum and H. schultesii from nature; the apomictic reproduction of tetraploid H. floribundum and of pentaploid H. glomeratum is also a new information. The variation of Hieracium subgen. Pilosella in the Krkonoše Mts. is discussed in connection with the presence of at least four sexual types and diversity of reproductive systems. The occurrence of H. stoloniflorum in the Krkonoše Mts. is dealt with.
Krahulcová & Krahulec	2000	Offspring diversity in Hieracium subgen. Pilosella (Asteraceae): new cytotypes from hybridization experiments and from open pollination.
Abstract: The progeny derived from experimental crosses, in which the following species of the Hieracium subgen. Pilosella were used as parents, was analyzed with respect to chromosome numbers: diploid H. lactucella, tetraploid H. pilosella, H. caespitosum and H. aurantiacum, pentaploid H. glomeratum and H. piloselliflorum. In addition, some of selected F1 hybrids as well as the hexaploid hybridogenous species H. rubrum were open pollinated and their offspring was studied. In most crosses the sexuals served as seed parents, while the pollen donors were usually facultative apomicts. A considerable karyological diversity was recorded within the progeny of some of individual seed parents, hybridizing easily due to (at least facultative) sexuality. In addition, the haploid parthenogenesis and the fertilization of unreduced egg cell contributed to offspring diversity. These reproduction modes, together with apomictic reproduction and fertilization of reduced egg cell, caused the rise of extremely diverse progeny of H. rubrum. The haploid parthenogenesis connected with aneuploidy was recorded as a new observation. Although the aneuploids are very rare in nature in Europe, the abundant and viable aneuploid progeny can be easily obtained from experimental crosses. Similarly, the viable triploids arising frequently from the crosses between diploid and tetraploid species, are in contrast to sparse occurrence of triploid cytotypes in the field. The reasons for these disproportions are discussed. Whereas the reduced competitive ability is expected in polyhaploids in the field, the natural polyploids originated spontaneously from the fertilized unreduced egg cell may be more common. The possibilities to reveal the contribution of particular species comprising hybrid polyploids in the field are discussed.
Krahulcová et al.	2000	Variation in Hieracium subgen. Pilosella: what do we know about its sources?
Abstract: The present paper reviews mechanisms producing complicated patterns of variation within Hieracium subgen. Pilosella. The taxonomic complexity of this subgenus is due to highly variable basic species and intermediate (hybridogenous) species. The most important sources of variation are polyploidy, hybridization and (mostly) facultative apomixis of the aposporous type. The combination of hybridization, apomixis and clonal growth leads to the maintenance of various hybrids having originated from backcrossing and hybridization among more than two species, which is possible because of the fertile pollen of apomictic hybrids. Ever since Mendel's experiments, some of F1 hybrids have been found to be highly variable, probably reflecting the high heterozygosity of some of the basic species. Variable progeny can also result from unreduced gametes, or the rare parthenogenetic development of gametes which have undergone meiosis. While these processes were detected in experiments, their role within field populations remains unknown. However, multiple origins of intermediate species, and introgression within basic species are highly likely to result in high levels of variation. While few population level studies have been undertaken in Europe, several such studies have been carried out on adventive populations in New Zealand, and these show a different pattern. Aneuploid plants, rare in Europe, are common in New Zealand, and there is frequently more than one ploidy level within a population.
Krahulcová et al.	2001	Chromosome numbers and reproductive systems in selected representatives of Hieracium subgen. Pilosella in the Krkonoše Mts (the Sudeten Mts) - 2.
Abstract: Chromosome numbers and reproductive systems of the following species are reported from the Krkonoše Mts (the Sudeten Mts): a) species not previously studied within this area: H. fuscoatrum Nägeli et Peter (2n=36, apomictic), H. blyttianum Fr. (2n=36, apomictic), H. tubulascens Norrl. (2n=36, apomictic), H. bauhini Besser (2n=45, apomictic), H. onegense (Norrl.) Norrl. (2n=18, sexual); b) new cytotypes recorded: H. floribundum Wimm. et Grab. (2n=18, sexual), H. apatelium Nägeli et Peter (2n=45, apomictic), H. iseranum Uechtr. (2n=45, apomictic), H. aurantiacum L. (2n=45, apomictic), H. stoloniflorum Waldst. et Kit. (2n=45); c) additional data on distribution and reproduction mode of species previously studied: H. pilosella L. (2n=36, sexual), H. lactucella Wallr. (2n=18), H. caespitosum Dumort. (2n=36, apomictic), H. aurantiacum L. (2n=36, apomictic), H. schultesii F. W. Schultz (2n=36, apomictic), H. glomeratum Froel. (2n=45, apomictic), H. floribundum Wimm. et Grab. (2n=36, apomictic), H. piloselliflorum Nägeli et Peter (2n=36, both sexual and apomictic; 2n=45, apomictic; 2n=54, apomictic). Chromosome numbers are given for the first time for H. fuscoatrum and H. tubulascens, the record of diploid sexual plants is a novelty for H. floribundum. New ploidy levels are also reported for H. apatelium and H. iseranum. The richness of the Krkonoše Mts in Hieracium subgen. Pilosella is discussed with respect to number of basic (4) and sexual (7) species. In the Czech Republic as well as in the Sudeten Mts, two species of this subgenus (H. fuscoatrum and H. tubulascens) were recorded for the first time.
Krahulcová et al.	2004	Reproduction mode in the allopolyploid facultatively apomictic hawkweed Hieracium rubrum (Asteraceae, H. subgen. Pilosella).
Abstract: The versatility of the breeding system in the hybridogenous hexaploid, Hieracium rubrum, was demonstrated in emasculation and crossing experiments. The flow-cytometric ploidy analysis of 1095 seedlings amongst its’ progeny enabled the determination and quantification of the reproductive pathway (apospory, haploid parthenogenesis, cross-fertilization of both reduced and unreduced female gametes) responsible for each progeny class. The progeny profiles were stable between two successive years. The percentage of hybrids arisen from crosses with tetraploid sexual H. pilosella was 7.9%. The rate of trihaploids generated by H. rubrum when crossed to H. pilosella was 3.95%, similar to that of pentaploid (n./n) and octoploid (2n./n) hybrids (3.95% and 3.39%). Unreduced pollen from H. pilosella contributed to hybridization much less frequently (0.56% of all progeny), than unreduced eggs of H. rubrum. The increased frequency of trihaploids formed by crossed compared to emasculated plants suggests an interaction between the presence of pollen and the autonomous development of meiotic embryo sacs. Although the environmental conditions (garden compared to unheated glasshouse) influenced the progeny following the emasculation, no corresponding response to environment was detected amongst the autonomously derived progeny following pollination with H. pilosella. However, there was an influence of pollen parent on progeny which varied under the different environmental treatments. The importance of residual sexuality in reproduction of apomicts is evident. The non-maternal progeny was generated with highly variable frequency especially in the glasshouse, with some capitula reaching up to 50%. Having an autonomous endosperm development, Hieracium subgen. Pilosella is almost unique among other aposporous genera, in which such variable reproduction mode is connected with pseudogamy.
Krahulcová & Suda.	2006	A modified method of flow cytometric seed screen simplifies the quantification of progeny classes with different ploidy levels.
Abstract:Flow cytometric analysis of ten bulked seeds is proposed to quantify particular embryo ploidy classes in Hieracium. The method is recommended 1) for the detection and quantification of residual sexuality in facultative apomicts, which can generate progeny from heteroploid crosses, 2) for the quantitative screening of pollen donors with different ploidy levels, based on the fertilization success of the maternal plant, and 3) for the screening of parents producing a high proportion of polyhaploids.
Krahulcová et al.	2009	The agamic complex of Pilosella (Asteraceae) in Bulgaria and in the southwestern Romania: variation in ploidy level and breeding systems..
Abstract: Chromosome numbers and breeding systems are given for a set of Pilosella species occurring in Bulgaria and SW Romania (Banat). All diploids were found sexual, most of polyploids apomictic.
Krahulcová et al.	2009	Enriching ploidy level diversity: the role of apomictic and sexual biotypes of Hieracium subgen. Pilosella (Asteraceae) that coexist in polyploid populations.
Abstract: The capacity to generate variation in ploidy and reproductive mode was compared in facultatively apomictic versus sexual maternal plants that coexist in two model populations. The population structure was studied in polyploid hybrid swarms comprised of Hieracium pilosella (usually sexual, less commonly apomictic), H. bauhini (apomictic), and their hybrids (sexual, apomictic, or sterile). Relationships among established biotypes were proposed on the basis of their DNA ploidy level/ chromosome number, reproductive mode and morphology. Isozyme phenotypes and chloroplast DNA haplotypes were assayed in the population that was richer in hybrids. The reproductive origin of seed progeny was identified in both sexual and apomictic mothers, using alternative methods: the karyological, morphological and reproductive characters of the cultivated progeny were compared with those of respective mothers, or flow cytometric seed screening was used. In both populations, the progeny of sexual mothers mainly retained a rather narrow range of ploidy level/chromosome number, while the progeny of facultatively apomictic mothers was more variable. The high-polyploid hybrids, which had arisen from the fertilization of unreduced egg cells of apomicts, mainly produced aberrant non-maternal progeny (either sexually and/or via haploid parthenogenesis). Apparently, such versatile reproduction resulted in genomic instability of the recently formed high-polyploid hybrids. While the progeny produced by both true apomictic and sexual mothers mostly maintained the maternal reproductive mode, the progeny of those ‘versatile’ mothers was mainly sexual. Herein, we argue that polyploid facultative apomicts can considerably increase population diversity.
Krahulcová & Rotreklová.	2010	Use of flow cytometry in research on apomictic plants.
Abstract: This paper reviews recent use of flow cytometry in studies on apomictic plant taxa. Most apomictic angiosperms are polyploid, often differing in ploidy level from their sexual counterparts within the agamic complex. Flow cytometry is widely used for screening the ploidy levels of mature plants and their seed generated both in the field and in experiments. Routine ploidy screening often accompanied by molecular markers distinguishing individual genotypes are used to reveal novel insights into the biosystematics and population biology of apomictic taxa. Apomixis (asexual seed formation) is mostly facultative, operating together with other less frequent reproductive pathways within the same individual. The diversity in modes of reproduction in apomicts is commonly reflected in the ploidy structure of their progeny in mixed-cytotype populations. Thus, flow cytometry facilitates the detection and quantification of particular progeny classes generated by different reproductive pathways. The specific embryo/endosperm ploidy ratios, typical of the different reproductive pathways, result from modifications of double fertilization in sexual/apomictic angiosperms. Thus, the reproductive origin of seed can be identified, including autonomous or pseudogamous apomixis, haploid parthenogenesis and sexual reproduction, involving either reduced or unreduced gametes. Collectively, flow cytometry has been used to address the following research topics: (i) assessing the variation in ploidy levels and genome sizes in agamic complexes, (ii) detection and quantification of different reproductive modes in facultative apomicts, (iii) elucidation of processes in populations with coexisting sexual and apomictic biotypes, (iv) evolution of agamic complexes, and (v) genetic basis of apomixis. The last topic is of paramount importance to crop breeding: the search for candidate gene(s) responsible for apomixis is the main objective of many research programmes. A list of the angiosperm taxa that could provide model systems for such research is provided.
Krahulcová et al.	2011	Expressivity of apomixis in 2n + n hybrids from an apomictic and a sexual parent: insights into variation detected in Pilosella (Asteraceae: Lactuceae).
Abstract: Reproductive variation was studied in the tetraploid Pilosella aurantiaca, hexaploid P. rubra (both species with facultative autonomous apospory) and in their 2n + n hybrids, which were obtained by crossing with a sexual pollen parent (tetraploid P. officinarum). The different DNA content in P. aurantiaca and P. officinarum demonstrated the actual 2n + n origin, both spontaneous from the field and through experimental crosses, of their hexaploid hybrids. The octoploid 2n + n progeny were recovered from an experimental cross of P. rubra and P. officinarum. The reproductive pathways operating in two maternal facultatively apomictic species and in the hybrids were quantified using a flow cytometric analysis of seeds obtained from either open-pollinated or emasculated plants. Whereas both maternal species displayed a high penetrance of apomixis, the level of apomixis among the majority of 2n + n hybrids was much lower and variable. Some of the hexaploid hybrids had a reduced seed set. Compared to the respective maternal parents, the decrease in apomixis due to haploid parthenogenesis and/or n + n mating was evident in almost all unreduced hybrids, irrespective of their field/experimental origin and ploidy. Hence, the reproductive behaviour in the apomictic maternal parent was profoundly different from that of the 2n + n hybrids with a sexual parent in spite of the preservation of the complete maternal genome in the hybrids. The regulatory interactions in hybrid genomes, such as effects of modifiers, heterochrony, and epigenetic control, may be consistent with the different expressivity of apomixis observed under different genetic backgrounds.
Krahulec et al.	2001	Jestřábníky podrodu Pilosella Krkonoš. [Species of Hieracium subgen. Pilosella within the Krkonoše Mts.].
Abstract: The present paper summarizes results of the project studying the diversity of Hieracium subgen. Pilosella species within the Krkonoše Mts (western part of the Sudeten Mts range). The list of species studied is given in Table 1 together with their somatic chromosome numbers, and breeding system. The high diversity of Hieracium flora is related to high number of sexual types (7). In spite of the fact that the main habitat type (montane grasslands) are without regular management at many places, there is a possibility of Hieracium protection. Two most important localities concentrating almost all species are given. History of research of Hieracium within this mountain range is discussed mainly in connection with species found in the past, but absent at present.
Krahulec et al.	2004	The Sudetic group of Hieracium subgen. Pilosella from the Krkonoše Mts: a sythetic view.
Abstract: The present paper summarizes the results of research of Hieracium subgen. Pilosella done by using different methods. The apomictic complex of Hieracium subgen. Pilosella found in the Krkonoše Mts, consists of the following basic species: H. lactucella (2x, sexual), H. onegense (2x, sexual), H. pilosella (4x, sexual), H. caespitosum (4x, apomictic) and H. aurantiacum (4x and 5x, apomictic). These species are considered to be the parents of a further set of mostly apomictic hybridogenous types. The ploidy level, breeding system, isozyme phenotypes, chloroplast haplotypes and geographic distribution of this whole complex was analysed. The different hybridogenous types have different frequencies in the field and differ in the frequency of isozyme phenotypes (a conservative estimate of the number of genotypes). Most have uniform chloroplast haplotypes, but some haplotypes could have originated from reciprocal crosses. The comparison of chloroplast haplotypes suggests that apomictic species were not only pollen donors, but also contributed seed and gave rise to several hybridogenous types, illustrating the importance of the residual sexuality of apomicts in this group. H. pilosella is a central species in this group and is connected with other parental species, H. floribundum, H. lactucella and H. aurantiacum by a set of hybridogenous species that have a similar genetic structure. Some of the distinct hybridogenous types within the complex are of multiple origin. In contrast, crosses between the same parental types may generate diverse progenies, which can often be classified as distinct taxa. All taxa recorded in the past are surveyed and discussed with respect to present knowledge. We suggest that the taxonomy and origin of particular entities of this and other such complexes is best resolved using information from morphological, genetical, cytological and ecological studies.
Krahulec & Krahulcová.	2006	Population based approaches in the study of Pilosella Hill (Asteraceae): A new view of its taxonomy?
Abstract: We present a structure of the Pilosella populations occurring in the Krkonoše Mts., northern Czech Republic. Each basic species, hybridogenous species and recent hybrid is documented by its frequency, cytotypes, breeding system, and chloroplast haplotypes. We compare this structure with the situation in another mountain range, the Šumava Mts. in the south western Czech Republic. Both regions have the same structure of hybridising species, but the resulting population are different. We deduce that random phenomena in the past and the residual sexuality of apomictic species has influenced the present population composition. Our results are discussed in connection with existing approaches to the taxonomy of Pilosella.
Krahulec et al.	2006	Ploidy level selection during germination and early stages of seedling growth in the progeny of allohexaploid facultative apomict, Hieracium rubrum (Asteraceae).
Abstract: Selection within progeny of a facultative apomict, Hieracium rubrum was studied using flow cytometry of embryos in seeds (a modified method of Flow Cytometric Seed Screen) and seedlings. Flow-cytometric screening of particular progeny classes was based on distinct ploidy categories, reflecting the way of their origin. The results of both estimations of progeny composition significantly differed, which makes direct comparison of proportions detected in seeds or seedling stage impossible. The results suggest that progeny originated from reduced egg cells have higher mortality during germination and early establishment phase than that arisen from unreduced egg cells. Within the progeny of emasculated plants, the proportion of polyhaploid progeny decreased in favor of apomictically derived plants. Within the progeny of plants pollinated by H. pilosella, the proportion of polyhaploid progeny decreased significantly in favor of apomictically derived plants and 2n + n hybrids. It is argued that at least a proportion of the sexually derived progeny of this facultatively apomictic maternal parent plant has a lower survival rate vitality than apomictically derived progeny.
Krahulec et al.	2008	The agamic complex of Hieracium subgen. Pilosella in the Šumava Mts.: Its structure and comparison with other regions in Central Europe.
Abstract: We studied the agamic complex of Hieracium subgen. Pilosella in the Šumava/Böhmerwald, the borderland between the Czech Republic and Germany. Their DNA ploidy levels/chromosome numbers, breeding systems, chloroplast haplotypes as well as the clonal structure of apomicts were determined. The complex consists of the following basic and intermediate species and recent hybrids. Basic species: H. aurantiacum L. (tetraploid and pentaploid, both apomictic), H. caespitosum Dumort. (tetraploid, apomictic), H. lactucella Wallr. (diploid, sexual), H. pilosella L. (tetraploid, sexual); intermediate species: H. floribundum Wimm. et Grab. (tetraploid, apomictic), H. glomeratum Froel. (tetraploid and pentaploid, both apomictic), H. scandinavicum Dahlst. (tetraploid, apomictic); recent hybrids: H. floribundum × H. pilosella (partly corresponding to H. piloselliflorum – tetraploid and hexaploid; tetraploid sexual or apomictic), H. glomeratum × H.pilosella (aneuploid, 2n = 38), H. aurantiacum × H. floribundum (tetraploid, almost sterile or apomictic), H. lactucella × H. pilosella (H. schultesii, triploid sterile, tetraploid sexual), H. aurantiacum × H. pilosella (H. stoloniflorum, tetraploid, sexual), H. aurantiacum > H. pilosella (H. rubrum, hexaploid). The hexaploid hybrids between H. pilosella and H. floribundum or H. aurantiacum produced mainly polyhaploid progeny. Two trihaploid plants were found growing in the neighbourhood of their putative hexaploid maternal parent H. rubrum, which is the first record of polyhaploids of this subgenus in the field. Comparison with other mountain ranges (especially the Krušné hory/Erzgebirge, and Krkonoše) with an almost identical composition of basic species, revealed that the structure of the agamic complexes differ.
Křišťálová et al.	2010	Populations of species of Pilosella in ruderal habitats in the city of Prague: frequency, chromosome numbers and mode of reproduction.
Abstract: Populations of Pilosella (Hieracium subgenus Pilosella) at ruderal localities were investigated in an urban area (Prague City) with respect to their distribution, variation in DNA ploidy level/chromosome number and mode of reproduction. The following species, hybridogenous species or hybrids (with ploidy level/chromosome number and mode of reproduction) were found: P. aurantiaca, P. caespitosa (4x, 5x), P. cymosa subsp. vaillantii (5x), P. officinarum (2n = 36, sexual; 2n = 54, sexual; 2n = 63), P. piloselloides subsp. bauhinii (2n = 45, 54; both apomictic), P. piloselloides subsp. praealta (5x; apomictic), P. brachiata (4x; sterile), P. densiflora, P. flagellaris, P. floribunda, P. erythrochrista, P. glomerata (5x; apomictic), P. leptophyton (5x; apomictic), P. rothiana (4x, apomictic), P. setigera, P. visianii (4x; apomictic), P. ziziana (4x, apomictic) and the previously undescribed hybridogenous type P. piloselloides x P. setigera (5x, apomictic). Pilosella visianii is reported from the Czech Republic for the first time. New habitats resulting from highway construction are suitable for Pilosella species. Many previously rare types, such as P. rothiana, can colonize these habitats and spread, not only locally, but also throughout the whole country.
Morgan-Richards et al.	2004	Interspecific hybridization among Hieracium species in New Zealand: evidence from flow cytometry.
Abstract: Hieracium pilosella (Asteraceae) was accidentally introduced to New Zealand about 100 years ago. Since then it has become an aggressive weed, and an unexpected degree of genetic and genome size variation has been detected; features that might result from interspecies hybridization. We investigated the possibility that H. pilosella has hybridized with related taxa. Of the four other subgenus Pilosella species introduced to New Zealand, H. praealtum is the most abundant and, on morphological and distributional evidence, most likely to be the other parent. Flow cytometry was used to estimate relative genome size for 156 Hieracium plants collected from the wild. Plants assigned to either parental or hybrid morphotypes were found to comprise tetraploid and pentaploid individuals using genome size measurements, and this was confirmed with direct mitotic chromosome counts for a subset of plants. The haploid DNA content of H. praealtum was approximately 22% larger than that of H. pilosella. Putative hybrids that were tetraploid had mean genome sizes equivalent to two H. pilosella and two H. praealtum haploid chromosome sets, implying they were hybrids arising from the fertilization of two reduced gametes. Similar results were obtained from tetraploid hybrids produced by controlled pollination. However, the majority of field hybrids were pentaploid with a genome size equivalent to four H. pilosella and one H. praealtum haploid chromosome sets. We infer that these are not first-generation hybrids but represent successful backcrossing with H. pilosella and/or hybrid-hybrid crossing, and that sexual tetraploid hybrids have been the parents. We note that populations putatively of H. pilosella often comprise apomictic pentaploid hybrids. Significantly, our data indicate the emergence of sexual hybrids that provide further opportunity for gene flow among taxa in this complex.
Mráz et al.	2011	Interspecific hybridization in the genus Hieracium (s. str.) – evidence for bidirectional gene flow and spontaneous allopolyploidization.
Abstract Although reticulation has indisputably played an important role in the evolutionary history of the genus Hieracium s. str. (Asteraceae), convincingly documented cases of recent interspecific hybridization are very rare. Here we report combined evidence on recent hybridization between two diploid species, Hieracium alpinum and H. transsilvanicum. The hybrid origin of the plants from the Romanian Eastern Carpathians was supported by additive patterns of nuclear ribosomal DNA polymorphism (ITS), an intermediate position of hybrid plants in principal coordinate analysis based on amplified fragment length polymorphism phenotypes (AFLP), and additivity at one allozyme locus. Flow cytometric analyses and chromosome counting showed that two hybrids were diploid (2n = 2x = 18) while one was surprisingly tetraploid (2n = 4x = 36). To our knowledge, this is the first record of spontaneous polyploidization following interspecific crossing in the genus. Allozyme data, especially the presence of unbalanced heterozygosity at one locus suggest the origin of this tetraploid via a triploid-bridge with subsequent backcrossing to H. alpinum. According to PCR-RFLP analyses of the trnT-trnL intergenic spacer, all H. x krasani hybrids examined had the H. alpinum haplotype while H. transsilvanicum served as a pollen donor. The hybrids occurred at the locality with abundant H. alpinum plants while paternal H. transsilvanicum was missing. Previously reported instances of interspecific hybridization between the same parental taxa showed an opposite direction of crossing and relative abundance of parental taxa. This suggests that the direction of hybridization might be influenced by the frequency of parental taxa at the locality.
Mráz et al.	2009	Geographical parthenogenesis, genome size variation and pollen production in the arctic-alpine species Hieracium alpinum.
Abstract: Hieracium alpinum L. (Asteraceae) is an arctic-alpine species distributed throughout Europe with both diploid and triploid cytotypes. We determined the ploidy levels of plants from 23 populations from Austria, Bosnia and Herzegovina, Finland, Italy, Norway, Romania, Slovakia, Switzerland and Ukraine. Data showed a nonoverlapping pattern of cytotype distribution: sexually reproducing diploids (2n = 2x = 18) occur solely in the Eastern and Southern Carpathians, while apomictic triploids (2n = 3x = 27) cover the rest of the range. Such clear-cut allopatry is rather rare in vascular plants with geographical parthenogenesis. Comparison of absolute genome size indicates genome downsizing (by on average 3.7%) of haploid DNA amount in triploids relative to diploids. Genome size further correlated with longitude and latitude in the Alps, with decreasing absolute DNA content from west to east, and from south to north. While previously published data indicated complete male sterility of triploid plants, we found that plants from the Alps and Bosnia and Herzegovina commonly produced some pollen, whereas populations from the Western Carpathians and Scandinavia seemed to be almost completely pollen sterile. Scenarios about the evolution of geographical parthenogenesis in H. alpinum are discussed.
Mráz et al.	2008	Cytogeography of Pilosella officinarum (Compositae): Altitudinal and Longitudinal Differences in Ploidy Level Distribution in the Czech Republic and Slovakia and the General Pattern in Europe
Abstract: Background and Aims: Pilosella officinarum (syn. Hieracium pilosella) is a highly structured species with respect to the ploidy level, with obvious cytogeographic trends. Previous non-collated data indicated a possible differentiation in the frequency of particular ploidy levels in the Czech Republic and Slovakia. Therefore, detailed sampling and ploidy level analyses were assessed to reveal a boundary of common occurrence of tetraploids on one hand and higher ploids on the other. For a better understanding of cytogeographic differentiation of P. officinarum in central Europe, a search was made for a general cytogeographic pattern in Europe based on published data. Methods: DNA-ploidy level and/or chromosome number were identified for 1059 plants using flow cytometry and/or chromosome counting on root meristem preparations. Samples were collected from 336 localities in the Czech Republic, Slovakia and north-eastern Hungary. In addition, ploidy levels were determined for plants from 18 localities in Bulgaria, Georgia, Ireland, Italy, Romania and Ukraine. Key Results: Four ploidy levels were found in the studied area with a contrasting pattern of distribution. The most widespread cytotype in the western part of the Czech Republic is tetraploid (4x) reproducing sexually, while the apomictic pentaploids and mostly apomictic hexaploids (5x and 6x, respectively) clearly prevail in Slovakia and the eastern part of the Czech Republic. The boundary between common occurrence of tetraploids and higher ploids is very obvious and represents the geomorphologic boundary between the Bohemian Massif and the Western Carpathians with the adjacent part of Pannonia. Mixed populations consisting of two different ploidy levels were recorded in nearly 11% of localities. A statistically significant difference in a vertical distribution of penta- and hexaploids was observed in the Western Carpathians and the adjacent Pannonian Plain. Hexaploid populations tend to occur at lower elevations (usually below 500 m), while the pentaploid level is more or less evenly distributed up to 1000 m a.s.l. For the first time the heptaploid level (7x) was found on one site in Slovakia. In Europe, the sexual tetraploid level has clearly a sub-Atlantic character of distribution. The plants of higher ploidy level (penta- and hexa-) with mostly apomictic reproduction prevail in the northern part of Scandinavia and the British Isles, the Alps and the Western Carpathians with the adjacent part of Pannonia. A detailed overview of published data shows that extremely rare records on existence of diploid populations in the south-west Alps are with high probability erroneous and most probably refer to the closely related diploid species P. peleteriana. Conclusions: The recent distribution of P. officinarum in Europe is complex and probably reflects the climatic changes during the Pleistocene and consequent postglacial migrations. Probably both penta- and hexaploids arose independently in central Europe (Alps and Carpathian Mountains) and in northern Europe (Scandinavia, Great Britain, Ireland), where the apomictic plants colonized deglaciated areas. We suggest that P. officinarum is in fact an amphidiploid species with a basic tetraploid level, which probably originated from hybridizations of diploid taxa from the section Pilosellina.
Mráz et al.	2005	Rare recent natural hybridization in Hieracium s.str. - evidence from morphology, allozymes and chloroplast DNA.
Abstract: The first proven data on natural hybridization in the genus Hieracium s. str. are presented. Plants with intermediate morphological characters between the diploids H. alpinum and H. transsilvanicum were found in the Munţii Rodnei (Romanian Eastern Carpathians) in 2001 and in the Chornohora Mts (Ukrainian Eastern Carpathians) in 2003. While plants of intermediate morphology between usually so called basic species are usually tri- or tetraploid in Hieracium s.str., these plants were diploid (2n=18) like both parental species in this region. The Romanian plant did not produce fertile achenes in free pollination and in control backcrosses with H. transsilvanicum, two hybrids from Ukraine were completly seed sterile in free pollination and reciprocal crosses. Pollen stainability as an indirect measure of male fertility was quite high in the studied Ukrainian hybrid plants and similar to the parental taxa. Evidence from allozyme analysis also confirmed the hybrid origin of the studied plants. Sequencing and PCR-RFLP analyses of the trnT-trnL intergenic spacer revealed that all hybrid plants had the H. transsilvanicum chloroplast DNA haplotype. Maternal inheritance of chloroplast DNA in this particular cross was proved with artificial hybrids from reciprocal experimental crosses between H. alpinum and H. transsilvanicum. In both localities, the natural hybrid plants were found in disturbed habitats, exceptionally allowing contact of the otherwise ecologically vicariate parental species. Morphologically, the hybrid plants belong to H. x krasani Woł.
Mráz et al.	2001	Genetic variation in the Hieracium rohacsense group (Hieracium sect. Alpina).
Abstract: Five isozyme systems (AAT, ADH, LAP, PGM, SKD) were studied in two tetraploid apomictic taxa of the Hieracium rohacsense group (Hieracium sect. Alpina). No intra- and inter-population variation was found in H. rohacsense Kit., endemic to the West Carpathians, which is in accordance with its narrow morphological variation. In contrast, a probably still unnamed tetraploid taxon from Mt. Pop Ivan (Ukrainian East Carpathians) belonging to the H. rohacsense group was represented by three phenotypes detected in one population. The role of diploid sexual taxa occurring in the alpine and subalpine belts of the Ukrainian East Carpathians in maintainig genetic variability is discussed. Apart from morphological characters the two closely related taxa included in this study can be separated also by their patterns of Pgm-1 locus.
Peckert & Chrtek		Mating interactions among coexisting diploid, triploid and tetraploid cytotypes of Hieracium echioides (Asteraceae).
Abstract: Experimental crosses between diploids, triploids and tetraploids of Hieracium echioides were made to examine mating interactions. Specifically, cytotype diversity in progeny from experimental crosses, intercytotype pollen competition as a reproductive barrier between diploids and tetraploids and differences in seed-set between intra- and intercytotype crosses were studied. Only diploids were found in progeny from 2x × 2x crosses. The other types of crosses yielded more than one cytotype in progeny, however, one cytotype predominated in each cross type: diploids (92%) in 2x × 3x crosses, tetraploids (88%) in 3x × 2x, triploids (96%) in 2x × 4x crosses, triploids (90%) in 4x × 2x crosses, tetraploids (60%) in 3x × 3x crosses, pentaploids (56%) in 3x × 4x crosses, triploids (80%) in 4x × 3x crosses and tetraploids (88%) in 4x × 4x crosses. No aneuploids were detected among karyologically analysed plants. Unreduced egg cells production was detected in triploids and tetraploids, on the contrary, formation of unreduced pollen was recorded only in two cases in triploids. Triploid plants produced x, 2x and 3x gametes, however, in male gametes predominated x (92%) gametes whereas in female gametes predominated 3x (88%) gametes. Cytotype diversity in progeny from crosses where diploids and tetraploids were pollinated by mixture of pollen from diploid and tetraploid plants suggested intercytotype pollen competition to serve as a prezygotic reproductive barrier. No statistically significant difference in seed-set obtained from intra- and intercytotype crosses between diploids and tetraploids were observed suggesting absence of postzygotic reproductive barriers among cytotypes.
Peckert et al.	2005	Genetic variation in agamospermous populations of Hieracium echioides in southern Slovakia and northern Hungary (Danube Basin).
Abstract: Six populations of Hieracium echioides subsp. echioides var. tauscheri from the Danube Basin between Bratislava and Budapest (locations: Balinka, Čenkov, Devín, Dorog, Győr, Pilis) were analysed using allozyme and karyological analysis. Five allozyme systems (EST, LAP, 6PGDH, PGM, and SKDH) were used to analyse the genetic structure of the examined populations. Analyses revealed low genetic variation both within- and among populations. Four multilocus allozyme phenotypes were detected; three populations (Čenkov, Devín and Győr) possessed phenotype I exclusively, while phenotype IIwas found only in the Balinka and Dorog populations. Two different phenotypes were found in the population of Pilis (phenotypes III and IV). However, due to the complex banding patterns generated for EST, allelic interpretationwas not possible, and the Balinka and Dorog populations appeared to possess different phenotypes. All populations proved to be tetraploid (2n = 36) and agamospermous. The geographic distribution pattern of the analysed populations (one allozyme phenotype at several isolated localities) may reflect a more common occurrence of the taxon in the past. Landscape changes, caused by changes in human management of the country,may have resulted in a loss of suitable localities, mainly open sandy habitats. These changes may have caused the reduction and fragmentation of H. *tauscheri habitat.
Petřík et al.	2003	Jestřábníky (Hieracium podrod Pilosella) Ještědského hřbetu. [Hieracium subgen. Pilosella in the Ještědský hřbet mountain ridge.]
Abstract: Localities of the hawkweeds (Hieracium subgen. Pilosella) from the Ještědský hřbet Ridge (Jeschkengebirge) are given. Seven "basic species" (H. aurantiacum, H. bauhini, H. caespitosum, H. cymosum subsp. cymigerum, H. lactucella, H. pilosella, H. piloselloides) and seven "intermediate species" (H. arvicola, H. dubium, H. glomeratum, H. iseranum, H. macranthelum, H. stoloniflorum and H. zizianum) were found. Three species collected here in the past (H. brachiatum, H. floribundum and H. sciadophorum) were not refound. Occurrence of H. piloselliflorum is known from the near Jizerské hory Mts., and it might be discovered in the study area. Habitat changes (abandonment of mown meadows) generally account for loss of Hieracium populations, and therefore the mowing of meadows is recommended.
Rotreklová et al.	2002	Chromosome numbers and breeding systems in some species of Hieracium subgen. Pilosella from the Central Europe.
Abstract: Chromosome numbers are given for 16 taxa (and one interspecific hybrid) of Hieracium subgen. Pilosella originating from Central Europe: H. apatelium Nägeli et Peter (2n = 45), H. aurantiacum L. (2n = 36), H. bauhini Besser (2n = 36, 45, 54), H. brachiatum Bertol. ex DC. (2n = 45, 48, 63, 72), H. densiflorum Tausch (2n = 36), H. echioides Lumn. (2n = 18, 27, 36), H. floribundum Wimm. et Grab. (2n = 36, 45), H. glomeratum Froel. (2n = 36, 45), H. guthnickianum Hegetschw. (2n = 54), H. lactucella Wallr. (2n = 18), H. onegense (Norrl.) Norrl. (2n = 18), H. pilosella L. (2n = 36, 45, 54), H. piloselliflorum Nägeli et Peter (2n = 36, 45), H. piloselloides Vill. (2n = 36), H. rothianum Wallr. (2n = 36), H. schultesii F. W. Schultz (2n = 45), and the hybrid H. floribundum × H. aurantiacum (2n = 36). New chromosome numbers are reported for H. brachiatum and H. floribundum. The octoploid cytotype (2n = 72), recorded in H. brachiatum, is the highest ploidy level ever found in plants from the subgen. Pilosella originating from the field. Aneuploidy, rare in this subgenus in Europe, occurs in this hybridogenous species as well: it was recorded in one plant (2n = 48) collected in a hybrid swarm H. pilosella × H. bauhini. The breeding system in H. bauhini, H. brachiatum, H. densiflorum, H. echioides, H. pilosella, H. piloselloides, and H. rothianum was studied. The sexual reproduction of pentaploid H. pilosella is a new observation: it means an increase of diversity in possible reproduction modes of those cytotypes having odd chromosome numbers.
Rotreklová et al.	2005	Chromosome numbers and breeding systems in some species of Hieracium subgen. Pilosella from Europe.
Abstract: Chromosome numbers (ploidy levels) were recorded in the following 25 taxa of Hieracium subgen. Pilosella: H. arvicola Nägeli et Peter (2n = 45), H. aurantiacum L. (2n = 36, 45), H. bauhini Besser (2n = 36, 45), H. bifurcum M. Bieb. (2n = 45), H. brachiatum Bertol. ex DC. (2n = 36, 45), H. caespitosum Dumort. (2n = 36), H. cymosum L. (2n ~ 4x), H. densiflorum Tausch (2n = 36, ~ 4x), H. echioides Lumn. (2n = 18, 45), H. fallacinum F.W. Schultz (2n = 36, 45), H. floribundum Wimm. et Grab. (2n = 36, ~ 4x, 45,), H. glomeratum Froel. in DC. (2n = 45), H. iseranum Uechtr. (2n = 36), H. kalksburgense Wiesb. (2n ~ 5x), H. lactucella Wallr. (2n = 18), H. macranthum (Ten.) Ten. (2n = 18), H. onegense (Norrl.) Norrl. (2n = 18), H. pilosella L. (2n = 36, 45, 54), H. piloselliflorum Nägeli et Peter (2n = 45), H. pilosellinum F.W. Schultz (2n = 36, 45), H. piloselloides Vill. (2n = 27, 36, ~ 4x, 45, ~ 5x), H. pistoriense Nägeli et Peter (2n = 27), H. rothianum Wallr. (2n ~ 3x), H. schultesii F.W. Schultz (2n = 36, 45, ~ 5x), H. zizianum Tausch (2n = 27, 36, 54), and one hybrid, H. onegense × H. pilosella (2n = 36). Besides chromosome counts in root-tip meristems, flow cytometry was used to determine the DNA ploidy level in 83 samples of 9 species. The presence of a long marker chromosome was confirmed in tetraploid H. caespitosum and H. iseranum, in pentaploid H. glomeratum, and in both tetraploid and pentaploid H. floribundum. The documented mode of reproduction is sexual (H. densiflorum, H. echioides, H. piloselloides) and apomictic (H. brachiatum, H. floribundum, H. pilosellinum, H. piloselloides, H. rothianum, H. zizianum). Hieracium bifurcum and H. pistoriense are sterile. The chromosome number and/or mode of reproduction of H. bifurcum (almost sterile pentaploid), H. pilosellinum (apomictic pentaploid), H. piloselloides (apomictic triploid), H. pistoriense (sterile triploid), H. rothianum (apomictic triploid) and H. zizianum (apomictic triploid) are presented here for the first time. The sexual reproduction recorded in the pentaploid H. echioides is the second recorded case of this mode of reproduction in a pentaploid cytotype of Hieracium subgenus Pilosella. A previously unknown occurrence of H. pistoriense (H. macranthum - H. bauhini) in Slovakia is reported.
Suda et al.	2007	Genome size variation and species relationships in Hieracium subgen. Pilosella (Asteraceae) as inferred by flow cytometry.
Abstract: Background and Aims: Hieracium subgen. Pilosella (hawkweeds) is a taxonomically complicated group of vascular plants, whose structure is substantially influenced by frequent interspecific hybridization and polyploidization. Two kinds of species, ‘basic’ and ‘intermediate’ (i.e., hybridogenous) are usually recognized. In this study, we investigated genome size variation in a representative set of Central European hawkweeds in order to assess the value of such a dataset for species delineation and inferring evolutionary relationships. Methods: Holoploid and monoploid genome sizes (C- and Cx-values) were determined using propidium iodide flow cytometry for 376 homogeneously cultivated individuals of Hieracium subgen. Pilosella, including 24 natural species (271 individuals), five recent field hybrids (seven individuals), and experimental F1 hybrids of four parental combinations (98 individuals). Supplementary chromosome counts were available for more than half of the plant accessions. Base composition (proportion of AT/GC bases) was cytometrically estimated in 73 individuals. Key Results: Seven different ploidy levels (2x-8x) were detected, with intraspecific ploidy polymorphism (up to four different cytotypes) occurring in 11 wild species. Mean 2C-values varied from 3.53 pg in diploid H. hoppeanum to 15.30 pg in octoploid H. brachiatum, spanning approximately 4.3-fold range. 1Cx-values ranged from 1.72 pg in H. pilosella to 2.16 pg in H. echioides (difference 1.26-fold). DNA content of (high) polyploids was usually proportional to DNA values of their diploid/low polyploid counterparts, indicating lack of processes altering genome size (i.e., genome down-sizing). Most species showed constant nuclear DNA amounts, exceptions being three hybridogenous taxa, in which introgressive hybridization was suggested as a presumable trigger of genome size variation. Monoploid genome sizes of hybridogenous species were always located between corresponding values of their putative parents. In addition, there was a good congruency between actual DNA estimates and theoretical values inferred from putative parental combination as well as between DNA values of experimental F1 hybrids and corresponding established hybridogenous taxa. Conclusions: Significant differences in genome size between hawkweed species from hybridogenous lineages involving the small-genome H. pilosella document the usefulness of nuclear DNA content as a supportive marker for reliable delineation of several of the most problematic Hieracium subgen. Pilosella taxa (incl. classification of borderline morphotypes). In addition, genome size data were shown to have a good predictive value for inferring evolutionary relationships and genome constitution (i.e., putative parental combination) in hybridogenous species.
Šingliarová et al.	2008	Loss of genetic diversity in isolated populations of an alpine endemic Pilosella alpicola subsp. ullepitschii: effect of long-term vicariance or long-distance dispersal?
Abstract: Pilosella alpicola subsp. ullepitschii (Asteraceae) is a strictly allogamous, diploid Carpathian endemic. Its distribution range comprises two areas separated by about 600 km. While in the Western Carpathians (Slovakia and Poland) the taxon occurs in numerous sites, only four localities of man-made origin are known from the Eastern and Southern Carpathians (Romania). We used allozyme markers to test two likely possible scenarios for the origin of this disjunction: long distance dispersal and vicariance. Our data indicate a significant loss of genetic diversity in the isolated Eastern and Southern Carpathian populations in following genetic parameters (averaged per region): percentage of polymorphic loci (38.9% found in the Eastern and Southern Carpathians versus 58.3% in the Western Carpathians), allelic richness (1.4 vs. 1.6), expected heterozygosity (0.134 vs. 0.235), mean number of distinguishable multilocus genotypes (4.3 vs. 10.6) and proportion of distinguishable multilocus genotypes (0.34 vs. 0.68). Higher proportion of homozygous loci found in the Eastern and Southern Carpathian populations might indicate a higher rate of inbreeding due to non-random mating. We assume that these genetically depauperate populations have experienced a very strong genetic bottleneck, probably due to a founder effect. Although our data suggest that the long-distance dispersal model is most likely, more discriminate genetic markers should be used to test this further.
Štorchová et al.	2000	An improved method of DNA isolation from plants collected in the field and conserved in saturated NaCl/CTAB solution.
Abstract: A simple method for isolation of genomic DNA from wild plants sampled in remote field areas is presented. The protocol combines NaCl/CTAB leaf preservation with sorbitol extraction of secondary compounds which often contain inhibitors of Taq DNA polymerase activity. The obtained DNA is suitable for random amplified polymorphic DNA (RAPD) analysis of plant populations as well as for specific amplification of chloroplast DNA sequences. The NaCl/CTAB leaf preservation is a powerful alternative to silica gel drying-based preservation.
Štorchová et al.	2002	Genetic variation in agamospermous taxa of Hieracium sect. Alpina (Compositae) in the Tatry Mts. (Slovakia).
Abstract: The mode of reproduction, pollen production, chromosome numbers, genetic variation (RAPD, isozymes) and overall similarity were studied in 6 species of Hieracium sect. Alpina in the Tatry Mts. (the Western Carpathians, Slovakia). All species were confirmed to be agamospermous and, except of H. krivanense and H. slovacum, lacking pollen grains. For the first time, chromosome number is reported for H. krivanense (2n=4x=36). Considerable genetic variation was revealed in H. alpinum and a correlation between geographic and genetic distances was found in this species. Between-population variation in RAPD and allozyme phenotypes was found in H. pinetophilum and H. crassipedipilum. In all other species, allozyme and RAPD variation was low or absent. With few exceptions, the species differ in their allozyme as well as RAPD patterns. The relatedness of one population of endemic H. slovacum and H. halleri was confirmed. It is shown, that Carpathian species of the H. fritzei group are derived from at least two ancestors.
Trávníček et al.	2011	Bridging global and microregional scales: ploidy distribution in Pilosella echioides (Asteraceae) in central Europe.
Abstract: A detailed knowledge of cytotype distribution can provide important insights into the evolutionary history of polyploid systems. This study aims to explore the spatial distribution of different cytotypes in Pilosella echioides at various spatial scales (from the whole distributional range to the population level) and to outline possible evolutionary scenarios for the observed geographic pattern. DNA-ploidy levels were estimated using DAPI flow cytometry in 4410 individuals of P. echioides from 46 populations spread over the entire distribution range in central Europe. Special attention was paid to the cytotype structure in the most ploidy-diverse population in south-west Moravia. Five different cytotypes (2x, 3x, 4x, 5x and 6x) were found, the last being recorded for the first time. Although ploidy-uniform (di- or tetraploid) sites clearly prevailed, nearly one-quarter of the populations investigated harboured more (up to all five) cytotypes. Whereas penta- and hexaploids constituted only a minority of the samples, a striking predominance of the triploid cytotype was observed in several populations. The representative sampling confirmed previous data on cytotype distribution, i.e. the spatial aggregation of mixed-ploidy populations in south-west Moravia and Lower Austria and the predominance of ploidy-uniform populations in other parts of the area investigated. Recurrent origin of polyploids from diploid progenitors via unreduced gametes and their successful establishment are considered the key factors promoting intrapopulational ploidy mixture (‘primary hybrid zones’). As an alternative to the generally accepted theory of cytotype co-existence based on the development of different means of inter-ploidy reproductive isolation, it is suggested that a long-term ploidy mixture can also be maintained in free-mating populations provided that the polyploids originate with a sufficient frequency. In addition, the prevalence (or subdominance) of the triploid cytotype in several mixed-ploidy populations represents the first evidence of such a phenomenon in plant systems with exclusively sexual reproduction.
Wilson et al.	2006	A new invasive hawkweed, Hieracium glomeratum (Lactuceae, Asteraceae), in the Pacific Northwest.
Abstract: During the summer of 2001, a new species of exotic hawkweed (Hieracium glomeratum Froel.) was identified from specimens collected in southeastern British Columbia and eastern Washington state. The specimens had at first been erroneously identified as the closely related H. caespitosum Dumort. A survey of flora and herbaria records revealed H. glomeratum is a new species record for North America. DNA fingerprints of plants from different localities proved to be identical. Their clonality along with a spot-like distribution indicates that this apomictic species probably originated from a single introduction from Europe which subsequently spread. This species adds to the complex of 14 other exotic Hieracium species belonging to the Eurasian subgenus Pilosella that are adventive in the United States and Canada. A distribution map of the native and adventive range of H. glomeratum and a key to distinguish it from related species in subgenus Pilosella that occur in North America is provided. The evolutionary and invasive potential of H. glomeratum is discussed.