Jindřich Chrtek

Rare recent natural hybridization in Hieracium s. str. – evidence from morphology, allozymes and chloroplast DNA

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 Muntii 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. × krasani Woł.

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, allozymes) 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, a 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.

Reconstruction of phylogenetic relationships in a highly reticulate group with deep coalescence and recent speciation (Hieracium, Asteraceae).

Phylogeny reconstruction based on multiple unlinked markers is often hampered by incongruent gene trees, especially in closely related species complexes with high degrees of hybridization and polyploidy. To investigate the particular strengths and limitations of chloroplast DNA (cpDNA), low-copy nuclear and multicopy nuclear markers for elucidating the evolutionary history of such groups, we focus on Hieracium s.str., a predominantly apomictic genus combining the above-mentioned features. Sequences of the trnV-ndhC and trnT-trnL intergenic spacers were combined for phylogenetic analyses of cpDNA. Part of the highly variable gene for squalene synthase (sqs) was applied as a low-copy nuclear marker. Both gene trees were compared with previous results based on the multicopy external transcribed spacer (ETS) of the nuclear ribosomal DNA. The power of the different markers to detect hybridization varied, but they largely agreed on particular hybrid and allopolyploid origins. The same crown groups of species were recognizable in each dataset, but basal relationships were strongly incongruent among cpDNA, sqs and ETS trees. The ETS tree was considered as the best approximation of the species tree. Both cpDNA and sqs trees showed basal polytomies as well as merging or splitting of species groups of non-hybrid taxa. These patterns can be best explained by a rapid diversification of the genus with ancestral polymorphism and incomplete lineage sorting. A hypothetical scenario of Hieracium speciation based on all available (including non-molecular) evidence is depicted. Incorporation of seemingly contradictory information helped to better understand species origins and evolutionary patterns in this notoriously difficult agamic complex.

Evolution of apomixis loci in Pilosella and Hieracium (Asteraceae) inferred from the conservation of apomixis-linked markers in natural and experimental populations

The Hieracium and Pilosella (Lactuceae, Asteraceae) genera of closely related hawkweeds contain species with two different modes of gametophytic apomixis (asexual seed formation). Both genera contain polyploid species, and in wild populations, sexual and apomictic species co-exist. Apomixis is known to co-exist with sexuality in apomictic Pilosella individuals, however, apomictic Hieracium have been regarded as obligate apomicts. Here, a developmental analysis of apomixis within 16 Hieracium species revealed meiosis and megaspore tetrad formation in 1 to 7% of ovules, for the first time indicating residual sexuality in this genus. Molecular markers linked to the two independent, dominant loci LOSS OF APOMEIOSIS (LOA) and LOSS OF PARTHENOGENESIS (LOP) controlling apomixis in Pilosella piloselloides subsp. praealta were screened across 20 phenotyped Hieracium individuals from natural populations, and 65 phenotyped Pilosella individuals from natural and experimental cross populations, to examine their conservation, inheritance and association with reproductive modes. All of the tested LOA and LOP-linked markers were absent in the 20 Hieracium samples irrespective of their reproductive mode. Within Pilosella, LOA and LOP-linked markers were essentially absent within the sexual plants, although they were not conserved in all apomictic individuals. Both loci appeared to be inherited independently, and evidence for additional genetic factors influencing quantitative expression of LOA and LOP was obtained. Collectively, these data suggest independent evolution of apomixis in Hieracium and Pilosella and are discussed with respect to current knowledge of the evolution of apomixis.

Diversity and endemism in deglaciated areas: ploidy, relative genome size and niche differentiation in the Galium pusillum complex (Rubiaceae) in Northern and Central Europe.

BACKGROUND AND AIMS Plants endemic to areas covered by ice sheets during the last glaciation represent paradigmatic examples of rapid speciation in changing environments, yet very few systems outside the harsh arctic zone have been comprehensively investigated so far. The Galium pusillum aggregate (Rubiaceae) is a challenging species complex that exhibits a marked differentiation in boreal parts of Northern Europe. As a first step towards understanding its evolutionary history in deglaciated regions, this study assesses cytological variation and ecological preferences of the northern endemics and compares the results with corresponding data for species occurring in neighbouring unglaciated parts of Central and Western Europe. METHODS DNA flow cytometry was used together with confirmatory chromosome counts to determine ploidy levels and relative genome sizes in 1158 individuals from 181 populations. A formalized analysis of habitat preferences was applied to explore niche differentiation among species and ploidy levels. KEY RESULTS The G. pusillum complex evolved at diploid and tetraploid levels in Northern Europe, in contrast to the high-polyploid evolution of most other northern endemics. A high level of eco-geographic segregation was observed between different species (particularly along gradients of soil pH and competition) which is unusual for plants in deglaciated areas and most probably contributes to maintaining species integrity. Relative monoploid DNA contents of the species from previously glaciated regions were significantly lower than those of their counterparts from mostly unglaciated Central Europe, suggesting independent evolutionary histories. CONCLUSIONS The aggregate of G. pusillum in Northern Europe represents an exceptional case with a geographically vicariant and ecologically distinct diploid/tetraploid species endemic to formerly glaciated areas. The high level of interspecific differentiation substantially widens our perception of the evolutionary dynamics and speciation rates in the dramatically changing environments of Northern Europe.

Mating interactions between coexisting dipoloid, triploid and tetraploid cytotypes ofHieracium Echioides (Asteraceae)

Experimental crosses between diploids, triploids and tetraploids ofHieracium 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, but one cytotype predominated in each cross type: diploids (92%) in 2x × 3x crosses, tetraploids (88%) in 3x × 2x crosses, 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 have been detected among karyologically analyzed plants. Unreduced egg cell production was detected in triploids and tetraploids, but formation of unreduced pollen was recorded only in two cases in triploids. Triploid plants produced x, 2x and 3x gametes: in male gametes x (92%) gametes predominated whereas in female gametes 3x (88%) gametes predominated.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 was observed, suggesting the absence of postzygotic reproductive barriers among cytotypes.

Can We Distinguish Plant Species that are Rare and Endangered from Other Plants Using Their Biological Traits

Understanding the factors responsible for species rarity is crucial for effective species conservation. One possible approach to obtaining information about causes of species rarity is to compare rare and common species. We analyzed the biological and ecological traits of critically endangered (CR) plant species of the Czech Republic. We compared the vegetative, generative and ecological traits of CR species with: i) common closely related species (a form of phylogenetic correction), ii) common closely related species sharing the same habitat (i.e., excluding pairs not sharing the same habitat, because many differences in species traits can be caused by adaptation to a specific habitat type) and iii) all plants of the Czech Republic. Information about species traits was mainly obtained from literature and databases. Comparison with common closely related species showed that CR species are smaller, flower for shorter periods, and have higher proportions of self-compatibility and higher terminal velocities. CR species also differ in their mode of dispersion, and their ecology and distribution. Comparison with species from the same habitat gave similar results. Comparison with the whole flora produced slightly different results, with additional differences in pollination mode and seed mass. The results of all three types of comparison suggest that critically endangered species of the Czech Republic are small, competitively inferior species, with some differences in the generative part of their life cycle, and occur mainly in open, unproductive habitats.

Veronica sect. Beccabunga in Egypt

Species of the genus Veronica L. sect. Beccabunga (Hill) Dumort. were studied in Egypt. Key, description, taxonomic notes, and phytocartograms of the following taxa are given: V. anagalloidesGuss. subsp. taeckholmiorumChrtek et Osbornová-Kosinová, V. catenataPennell subsp. pseudocatenataChrtek et Osbornová-Kosinová, V. anagallis-aquatica L., V. kaiseriTäckholm V. in Laurent-Täckholm et Drar, and V. scardicaGriseb. subsp. africanaChrtek et Osbornová-Kosinová. V. scardicaGriseb. was misidentified previously as V. beccabunga L., which, as the study reveals, does not occur in Egypt.

Notes on the synanthropic plants of Egypt 3.Grammica campestris and other species of familyCuscutaceae

Species of familyCuscutaceae belonging to three genera, viz.Grammica, Monogynella andCuscuta s. str. were studied in Egypt, some of them also in Iraq. Descriptions, keys, tables with comparisons of main morphological features, as well as taxonomic, chorological, and ecological notes, and also phytocartograms of the following taxa growing or expected in Egypt are given:Grammica campestris(Yuncker) Hadač etChrtek,G. chinensis(Lam.) Hadač etChrtek,Monogynella monogyna(Vahl) Hadač etChrtek,Cuscuta pedicellataLedeb.,C. epilinumWeihe exBoenn.,C. palaestinaBoiss. (incl.C. balansaeBoiss. etReuter exYuncker),C. planifloraTen. (incl.C. approximataBabingt.), andC. brevistylaA. Rich. A new variety ofMonogynella monogyna, var.hadacii, was described from Iraq. A new combination,Monogynella monogyna subsp.esquamata(Engelm.) Chrtek etOsbornová, was made. Main attention was given toGrammica campestris, the species that is nowadays expanding in Egypt.

Notes on the synanthropic plants of Egypt

Red and blue flowered pimpernels commonly referred toAnagallis arvensis s. 1. were studied in Egypt, Iraq, and adjacent territories. Key, description, taxonomic, chorological, ecological notes, and phytocartograms of the following taxa growing or expected in Egypt are given:Anagallis arvensis L. var.arvensis, A. latifolia L.,A. arvensis L. var.caerulea (L.)Gouan, andA. foeminaMill. New hybridAnagallis×hadidiiChrtek etOsbornová-Kosinová (A. arvensis L. var.arvensis × A. latifolia L.) is described.