Loureiro J., Trávníček P., Rauchová J., Urfus T., Vít P., Štech M., Castro S. & Suda J. (2010): The use of flow cytometry in the biosystematics, ecology and population biology of homoploid plants. – Preslia 82: 3–21.
Over the last decade there has been a tremendous increase in the use of flow cytometry (FCM) in studies on the biosystematics, ecology and population biology of vascular plants. Most studies, however, address questions related to differences in genome copy number, while the value of FCM for studying homoploid plant groups has long been underestimated. This review summarizes recent advances in taxonomic and ecological research on homoploid plants that were made using FCM. A fairly constant amount of nuclear DNA within each evolutionary entity together with the often large differences between species means that genome size is a useful character for taxonomic decision-making. Regardless of the number of chromosomes, genome size can be used to delimit taxa at various taxonomic levels, resolve complex low-level taxonomies, assess the frequency of interspecific hybridization or infer evolutionary relationships in homoploid plant groups. In plant ecology and evolutionary biology, variation in genome size has been used for prediction purposes because genome size is associated with several phenotypic, physiological and/or ecological characteristics. It is likely that in the future the use of FCM in studies on taxonomy, ecology and population biology of homoploid plants will increase both in scope and frequency. Flow cytometry alone, but especially in combination with other molecular and phenotypic approaches, promises advances in our understanding of the functional significance of variation in genome size in homoploid plants.

Krahulcová A. & Rotreklová O. (2010): Use of flow cytometry in research on apomictic plants. – Preslia 82: 23–39.
This paper reviews recent use of flow cytometry in studies on apomictic plant taxa. The most of 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.

Šmarda P. & Bureš P. (2010): Understanding intraspecific variation in genome size in plants. – Preslia 82: 41–61.
Intraspecific variation in genome size makes it possible to study ongoing processes of genome size evolution. Although there are over 200 papers on intraspecific variation in genome size, there is still limited understanding of this phenomenon, especially as many of these papers are based on weak methodology and therefore report biased or false evidence of the extent of intraspecific variation. In this paper the recent progress in understanding the spatio-temporal dynamics of intraspecific variation in genome size caused by the gradual accumulation of mutations is reviewed. The results of the case studies on Microseris douglasii, Zea mays, Silene latifolia, Hordeum spontaneum and Lolium hybrids, and in particular that on Festuca pallens, are discussed. The variation in genome size that occurs within species is caused mainly by differences in the content of repetitive DNA, in particular it is a consequence of the dynamics of transposable elements. Variation may be induced and maintained polytopically. We assume that it is probably more frequent in groups of young radiating species. Even in the initial stages, the variation in genome size generated within a population seems to be restricted by selection, which is also important in stabilizing genome size within species. The long-term persistence of the variation within a population and its further accumulation may be enhanced by gametes with different genome sizes, produced by the segregation of unequally sized homeologous chromosomes. Over large geographical scales and across contrasting environmental gradients, the distribution of genome sizes within species may be influenced by the nucleotype effect, with smaller genomes being more successful at higher latitudes and altitudes and under stressful conditions. However, the small differences in genome size within species seem generally to be of minor importance relative to other components of plant fitness that may be selectively favourable under particular environmental or habitat conditions. The processes generating variation in genome size may be associated with phenotypic variation. While the shift in the genome size of a population through selection enables adaptive evolution of genome size in a newly arising species, the spatio-temporal variation in genome size within an ancestral species allows for a rapid multiple genome size divergence of related species through random drift in genome size (founder effect, bottleneck effect) during range fragmentation, hybridization and/or polyploidization.

Temsch E. M., Greilhuber J. & Krisai R. (2010): Genome size in liverworts. – Preslia 82: 63–80.
Liverworts are poorly represented in the record of DNA C-values. Data for not more than nine species are reported in the literature. Here we present flow cytometric measurements of genome size for 32 foliose and 11 thallose species from 22 out of 83 families. The main method used in this study was flow cytometry using propidium iodide as the DNA stain. Feulgen densitometrywas applied as a supplementary method but it proved less suitable because the rigid cellwalls of liverwort tissue are resistant to maceration and apparently often inhibit the diffusion of reagents, which results in low estimates of DNA content. The precise or approximate number of chromosomes were counted, where possible. Among the thallose liverworts, the lowest 1C-value was recorded for Marchantia polymorpha (0.293 pg) and the highest for diploid Pellia epiphylla (7.401 pg). Haploid P. epiphylla (1C = 3.803 pg) had the largest genome among the haploid thalloid liverworts. Among the foliose liverworts, Lejeunea cavifolia with a value of 0.211 pg (1C) was ranked the lowest and Mylia taylorii, a haploid with 7.966 pg (1C) and a large amount of dense heterochromatin, concentrated in one big spherical chromocentre, the highest. This 38-fold variation covers the extremes of the whole sample and exceeds the ca 12-fold variation recorded in mosses (0.174–2.160 pg, 1C). This variation is nevertheless low compared to the 2000-fold interspecific variation found in angiosperms. Several instances of intraspecific variation in DNA ploidy (x and 2x) were found – in Radula complanata, Pellia epiphylla and Metzgeria furcata. In Lophocolea heterophylla, accessions differed 3.37-fold in C-value at haploid chromosome number. This points to cryptic taxonomic differentiation and warns against premature statements about ploidy levels based only on DNA measurements. Significant intraspecific intraploidal variation in C-value was also observed in certain instances. In Frullania dilatata, female plants with two large heterochromatic sex-chromosomes have a 1.35-fold higher C-value than male plants with only one sex chromosome. In most other cases of intraspecific variation the role of sex differences remains to be clarified.

Kubešová M., Moravcová L., Suda J., Jarošík V. & Pyšek P. (2010): Naturalized plants have smaller genomes than their non-invading relatives: a flow cytometric analysis of the Czech alien flora. – Preslia 82: 81–96.
Genome size has been suggested as one of the traits associated with invasiveness of plant species. To provide a quantitative insight into the role of this trait, we estimated nuclear DNA content in 93 alien species naturalized in the Czech Republic, belonging to 32 families, by using flow cytometry, and compared it with the values reported for non-invading congeneric and confamilial species from the Plant DNA C-values database. Species naturalized in the Czech Republic have significantly smaller genomes than their congeners not known to be naturalized or invasive in any part of the world. This trend is supported at the family level: alien species naturalized in the Czech flora have on average a smaller genome than is the mean value for non-invading confamilials. Moreover, naturalized and non-invading species clearly differed in the frequency of five genome size categories; this difference was mainly due to very small genomes prevailing and intermediate to very large genomes underrepresented in the former group. Our results provide the first quantitative support for association of genome size with invasiveness, based on a large set of alien species across a number of plant families. However, there was no difference in the genome size of invasive species compared to naturalized but non-invasive. This suggests that small genome size provides alien plants with an advantage already at the stage of naturalization and need not be necessarily associated with the final stage of the process, i.e. invasion.

Suda J., Trávníček P., Mandák B. & Berchová-Bímová K. (2010): Genome size as a marker for identifying the invasive alien taxa in Fallopia section Reynoutria. – Preslia 82: 97–106.
DAPI and propidium iodide flow cytometry were used to determine the variation in genome size in 166 samples and of all taxa and ploidy levels of Fallopia section Reynoutria (knotweeds) recorded in the Czech Republic. Significant differences were detected in the amount of nuclear DNA, associated with the ploidy levels and taxonomic identity of the material. At each ploidy level, F. sachalinensis showed the lowest and F. japonica the highest fluorescence intensities. The fluorescence values for the hybridogenous F. ×bohemica were located in-between these two levels. In most cases, there was at least a four-percent gap in fluorescence values between the nearest neighbours belonging to a different taxon. Intraspecific variation in genome size was very low in all taxa except hexaploid F. ×bohemica; this could be due to the complex evolutionary history of this taxon. Our results indicate that the amount of nuclear DNA can be used as a reliable marker for the identification of homoploid knotweed species and their hybrids. Different evolutionary pathways for the origin of high polyploids and/or hybridogenous taxa are proposed based on genome size.

Šafářová L. & Duchoslav M. (2010): Cytotype distribution in mixed populations of polyploid Allium oleraceum measured at a microgeographic scale. – Preslia 82: 107–126.
Despite the substantial knowledge of the variation in cytotypes at large spatial scales for many plants, little is known about the rates at which novel cytotypes arise or the frequencies and distributions of cytotypes at local spatial scales. The frequency distribution, local spatial structure, and role of habitat differentiation of tetra-, penta- and hexaploid cytotypes of the bulbous geophyte Allium oleraceum were assessed in 21 populations sampled in the Czech Republic. The ploidy levels determined by flow cytometry confirmed that there was a mixture consisting of two or three cytotypes (i.e. 4x+5x, 4x+6x, 5x+6x, 4x+5x+6x). In addition, mixtures of cytotypes were found at sites previously considered to be cytotype-homogeneous. At all sites previously found to contain a mixture of two cytotypes, no plants with the third ploidy level were found. Although the relative frequencies of cytotypes varied considerably both among and within populations, mixed populations consisting of tetra- and hexaploids were usually dominated by tetraploids. This suggests that there are secondary contacts among cytotypes but there is little gene flow among them except for the rare formation of hexaploids in tetraploid populations. Cytotypes were not randomly distributed over the study area but were spatially segregated at either 47.6% or 61.9% of the sites investigated, depending on the statistical test (Mantel test or average distance test) used. When the composition of habitats at each of the sites is taken into account, cytotypes were more frequently spatially segregated at sites with a heterogeneous environment than a homogeneous environment. This implies that the cytotypes are ecologically differentiated. The frequent co-occurrence of cytotypes, with or without significant spatial segregation, at many sites with heterogeneous or homogeneous environments, however, suggests that niche differentiation alone is probably ineffective in determining co-occurrence. It is supposed that the prevailing vegetative reproduction associated with local dispersal, a high population density of the species in a landscape, and non-equilibrial processes influencing the establishment and extinction of A. oleraceum populations can also support the local co-occurrence of cytotypes.

Dušková E., Kolář F., Sklenář P., Rauchová J., Kubešová M., Fér T., Suda J. & Marhold K. (2010): Genome size correlates with growth form, habitat and phylogeny in the Andean genus Lasiocephalus (Asteraceae). – Preslia 82: 127–148.
Variation in genome size in a particular taxonomic group can reflect different evolutionary processes including polyploidy, hybridization and natural selection but also neutral evolution. Using flow cytometry, karyology, ITS sequencing and field surveys, the causes of variation in genome size in the ecologically and morphologically diverse high-Andean genus Lasiocephalus (Asteraceae, Senecioneae) were examined. There was a 1.64-fold variation in holoploid genome size (C-values) among 189 samples belonging to 20 taxa. The most distinct was a group of plants with large genomes corresponding to DNA triploids. Disregarding the DNA triploids, the remaining samples exhibited a pronounced (up to 1.32-fold) and rather continuous variation. Plants with the smallest genomes most likely represent intergeneric hybrids with the closely related and sympatric Culcitium nivale, which has a smaller genome than Lasiocephalus. The variation in genome size in samples of diploid Lasiocephalus was strongly correlated with several environmental and life history traits (altitude, habitat and growth form). However, all these factors, as well as genome size itself, were correlated with phylogeny (main split into the so-called ‘forest’ and ‘páramo’ clades), which most probably represents the true cause of the differentiation in intrageneric genome size. In contrast, relationships between genome size and phylogeny were not apparent at lower divergence levels. Instead, here we suggest that ecological conditions have played a role in driving shifts in genome size between closely related species inhabiting different environments. Collectively, this study demonstrates that various evolutionary forces and processes have shaped the variation in genome size and indicates that there is a need for multi-approach analyses when searching for the causes and consequences of changes in genome size.

Trávníček P., Eliášová A. & Suda J. (2010): The distribution of cytotypes of Vicia cracca in Central Europe: the changes that have occurred over the last four decades. – Preslia 82: 149–163.
The formation and maintenance of polyploids (via the development of various reproductive barriers) rank among the central questions of studies on polyploid evolution. However, the long time scale of most evolutionary processes makes the study of the dynamics of diploid-polyploid groups difficult. A suitable candidate for a targeted comparative study is Vicia cracca (Fabaceae), which in the late 1960s was subjected to a detailed cytotype screening in Central Europe. Re-sampling the original localities offers a unique opportunity to assess changes in the ploidy structure of the populations, which should reflect the cumulative effect of all the evolutionary forces acting on the plants. Using flow cytometry, the DNA ploidy levels of more than 6,500 individuals of V. cracca collected at 257 localities in Austria, the Czech Republic, Germany and the Slovak Republic were estimated. Three different cytotypes (2x, 3x and 4x) were detected. While tetraploids predominated in the western part of the area investigated (179 populations), the diploids had a more easterly distribution (62 populations). There is a secondary zone of cytotype contact near the boundary between the Czech and Slovak Republics. Sixteen populations (~6%) consisted of a mixture of 2x and 4x cytotypes. Triploids are very rare; only seven individuals were found in two otherwise diploid populations, indicating the existence of breeding barriers between diploids and tetraploids. The distribution of cytotypes is similar to that determined four decades ago using chromosome counts. Nevertheless, there are some discrepancies, namely the current absence of: (i) the diploid cytotype in southern Bohemia and (ii) the altitudinal segregation in the distribution of cytotypes, including two formerly recognized chromosomal races of diploids, perhaps a result of more representative sampling. Identical monoploid genome sizes (1Cx-values) of both the majority ploidy levels support an autopolyploid origin of the tetraploids.

Dúbravková D., Chytrý M., Willner W., Illyés E., Janišová M. & Kállayné Szerényi J. (2010): Dry grasslands in the Western Carpathians and the northern Pannonian Basin: a numerical classification. – Preslia 82: 165–221.
A syntaxonomical revision of dry grasslands of the alliances Bromo pannonici-Festucion pallentis, Festucion valesiacae and Koelerio-Phleion phleoidis (class Festuco-Brometea) in the natural biogeographical region of the Western Carpathians and northern Pannonian Basin is presented. A geographically stratified data set of 2686 relevés from the south-eastern Czech Republic, northeastern Austria, Slovakia and northern Hungary was divided into 25 clusters using a modified TWINSPAN algorithm. The proposed classification simplifies and unifies the previous syntaxonomical systems, which differ in these four countries. Main environmental gradients responsible for variation in species composition of theses grasslands were revealed by detrended correspondence analysis and interpreted using indicator values. The major pattern of variation reflects soil nutrient availability and moisture, which are negatively correlated with soil reaction.

Dudová L., Hájek M. & Hájková P. (2010): The origin and vegetation development of the Rejvíz pine bog and the history of the surrounding landscape during the Holocene. – Preslia 82: 223–246.
The Rejvíz bog is an extensive mire complex in Central Europe, with up to 7 m deep sediments and two natural lakes. Recent vegetation is one of the best preserved examples of Pinus uncinata subsp. uliginosa (syn. P. rotundata) bog woodland in Central Europe. The origin and development of the mire and changes in the surrounding landscape vegetation are reconstructed using sediment stratigraphy, radiocarbon dating, pollen analysis and plant-macrofossils analysis, with particular emphasis on the processes that resulted in the origin of Rejvíz bog and on pine woodland dynamics. Based on identified species the water level changes were reconstructed. The sediment started to accumulate more than 9000 years ago at an open mixed-woodland spring with Dichodontium palustre. Later, poor fen vegetation with sedges and horsetails developed. Around 6170 cal. yr BC the fen became inundated for 2000 years and (semi)aquatic vegetation thrived. Next step in the succession followed a decline in water level which resulted in the development of drier oligothrophic vegetationwith a high representation of pine and dwarf shrubs. After ca 1020 cal. yr BC the mire became the bog it is now. Three wooded stages appeared in both the minerotrophic and ombrotrophic developmental phases: before 6720 cal. yr BC, during ca 1960–1020 cal. yr BC and recently. The vegetation in the surrounding landscape developed without marked human interventions up till ca the last six or five centuries, when deforestation and later settlement took place. Comparison with published data from the Góry Bystrzyckie/Orlické hory Mts suggests that not only regional, but also local vegetation changed in a similar way across the middle-altitude eastern Sudetes, following oscillations in climate rather than local changes in mire water regime.

Csiky J., Mesterházy A., Szalontai B. & Pótóné Oláh E. (2010): A morphological study of Ceratophyllum tanaiticum, a species new to the flora of Hungary. – Preslia 82: 247–259.
Ceratophyllum tanaiticum Sapjegin, a species new to the flora of Hungary, was discovered at two localities in the Hungarian part of the Drava Plain in 2008. These are the westernmost, disjunct localities of this Pontic-Caspian endemic species. For characterization of the Hungarian specimens, nine morphological features of nine Ceratophyllum taxa were used in PCA, CVA analyses and UPGMA classification. In these analyses Hungarian and other C. tanaiticum samples always formed a cluster distinct from other Ceratophyllum taxa. These results confirm an earlier concept in which the character peduncle length contributed the highest loading value for separating C. tanaiticum from other 3–4 leaf-ordered species. Microscopic morphological features, including the number of longitudinally arranged lacunae in one row of parenchymatic tissue between the first and the second dichotomic branching, the length of the sequence between the first and second branching of leaves; number, morphology and width of bracts under the fruit of fresh Hungarian material are identified as new characters for C. tanaiticum, C. submersum and C. demersum.

Kaplan Z. (2010): Hybridization of Potamogeton species in the Czech Republic: diversity, distribution, temporal trends and habitat preferences. – Preslia 82: 261–287.
A revision of the diversity and distribution of Potamogeton hybrids in the Czech Republic is presented. Thorough examination of herbarium material and recent extensive field studies revealed the present and/or past occurrence of eight Potamogeton hybrids in the Czech Republic. In addition to morphological characters, stem anatomy and/or molecular analysis were used to identify some of the hybrids. All the hybrids detected are between broad-leaved species of the genus, suggesting that hybrids between linear-leaved species may be overlooked because of the overall morphological similarity of taxa within this group. Four of the hybrids identified, P. ×nitens, P. ×olivaceus, P. ×sparganiifolius and P. ×undulatus, are recorded for the first time from the Czech Republic. Four of the hybrids are now extinct in the Czech Republic and the extant hybrids are rare. The occurrence of P. ×lintonii was not confirmed; the previous record was based on extreme forms of P. gramineus. The name P. ×concinnitus, proposed for a putative hybrid combination “P. pusillus × P. crispus”, was lectotypified and reduced to a synonym of P. crispus. Although the absolute number of finds of specimens of Potamogeton hybrids per decade is increasing, this is not a result of more frequent hybridization but of an increase in recording activity. Most records for recent decades are associated with targeted research by a few experts. The typical habitat of Potamogeton hybrids in the Czech Republic are ponds that were previously drained in summer and allowed to dry out. Many historical localities disappeared when the traditional fishpond management was largely abandoned and fish farming become more intensive. In the 19th century in particular some hybrids were recorded also in rivers but these occurrences generally disappeared after the extensive channelling of rivers at the beginning of the 20th century. Many hybrids occur at the same localities as their parents but it is documented that hybrids can persist vegetatively in the absence of the parental species, presumably as relics of the previous presence of the parent plants. Although almost all Potamogeton hybrids are consistently sterile, a cultivation experiment showed that P. ×angustifolius set seeds that were fertile and successfully produced adult plants.

Doležal J., Mazůrek P. & Klimešová J. (2010): Oak decline in southern Moravia: the association between climate change and early and late wood formation in oaks. – Preslia 82: 289–306.
Pedunculate (Quercus robur) and sessile (Quercus petraea) oak, dominant species in European hardwood forests, are declining in many regions throughout Europe and extreme climatic events (summer drought, winter frost) are considered to be key factors contributing to this decline via a negative effect on wood formation. An extensive sampling of scattered oak trees within a landscape of small groves and flower meadows in the White Carpathians, a hilly chain in the warm south-eastern part of the Czech Republic, was undertaken in order to determine the association between growth in diameter and climate over the last 100 years. The association with climate was evaluated by comparing latewood, earlywood and total ring widths with monthly climatic data over the period 1900–2006, using a combination of response function and pointer year analyses. The two approaches clearly showed that late wood growth of oak trees, growing on deep calcium-rich soils, which dry out in summer, is mainly associated with rainfall in May–June, while early wood growth is associated with previous autumn and winter temperatures. Extreme growth years coincided with an abnormally wet or dry May–June periods, which are often associated with cool or hot Junes. Deficient water balances resulting from low rainfall and high temperatures during the summer period are negatively associated with late wood formation and hence total annual growth increment. The results provide support for a crucial role of climate change (decline in rainfall and increase in summer temperatures over the last three decades) among other external factors in the high number of oaks dying prematurely in the White Carpathian wooded grasslands. Prolonged periods of unfavourable climatic conditions cause attenuated trees to become prone to fungal attack and mistletoe hemiparasites, which predispose the oaks to damage or death, especially solitary pedunculate oaks.

Rozbrojová Z., Hájek M. & Hájek O. (2010): Vegetation diversity of mesic meadows and pastures in the West Carpathians. – Preslia 82: 307–332.
A phytosociological study of the West Carpathian mesic hay meadows and pastures (order Arrhenatheretalia elatioris) was performed and is the first unified investigation into the vegetation diversity in the area, which is situated in three countries (Slovakia, Czech Republic and Poland). Because of the differences in the current classification systems used in different countries it was not possible to make a single selection of the Arrhenatheretalia relevés from the databases, so a data set containing relevés originally assigned to three orders encompassing this vegetation in hay meadows and pastures in the area (Arrhenatheretalia elatioris, Molinietalia and Nardetalia strictae) was established. This data set was classified using cluster analysis. Only the cluster corresponding to the order Arrhenatheretalia elatioris at the level of three clusters was further classified in the same way as the whole data set. The ecological interpretation of the classification was based on altitude, Ellenberg indicator values and geological bedrock. The clusters were also compared with the syntaxonomical assignment of the relevés by their authors. The classification at the level of 12 clusters reflected the most widespread vegetation types of mesicmeadows and pastures recorded in the area. The vegetation of extensive pastures, corresponding to the association Anthoxantho odorati-Agrostietum tenuis, seemed to be more similar in floristic composition to the mesic meadows of Arrhenatherion elatioris than to the intensive pastures of Cynosurion cristati, where it was traditionally classified, which has important conservation consequences because of the different position of these units in conservation systems such as Natura 2000. Higher altitude meadows were divided into four vegetation types including meadows corresponding to the association Gladiolo imbricati-Agrostietum capillaris, which is a frequent community in the Polish Carpathians that does not occur in the other regions. Montane meadows currently classified in Polygono bistortae-Trisetion flavescentis were less clearly distinguished, probably because of their patchy distribution in the West Carpathians. The differences in vegetation diversity of meadows and pastures between particular countries were confirmed, with Gladiolo imbricati-Agrostietum capillaris occurring predominantly in the northern part of the West Carpathians and Anthoxantho odorati-Agrostietum tenuis virtually absent here. The ecological determinants of variation in montane meadows are discussed.

Trnková R., Řehounková K. & Prach K. (2010): Spontaneous succession of vegetation on acidic bedrock in quarries in the Czech Republic. – Preslia 82: 333–343.
Variability in vegetation, participation of target and non-target species and the role of the local species pool in the spontaneous succession on acidic bedrock were studied in quarries. The study was conducted in the Českomoravská vrchovina uplands (central Czech Republic). A total of 135 relevés, 5 × 5 m in size, were used to sample 41 quarries that were abandoned from 1 to 92 years ago. Three types of sites were distinguished: mesic, wet and periodically flooded. Species cover (seven point Braun-Blanquet scale) was visually estimated. The following characteristics were noted: steep rocky slopes, bottoms and levels, dumps and screes as habitat types; age; proportion of the main land-cover categories (arable land, ruderal and urban, grassland, woodland and wetland) in the surroundings up to 100 m and 1 km from each quarry; and the occurrence of target (grassland, woodland, wetland) and non-target (ruderal, alien) species up to 100 m from each quarry. Ordination indicates that the spontaneous succession of vegetation results in the formation of mixed woodland, Alnus and Salix carrs, or tall sedge and Typha beds with scattered Salix, depending on the wetness of a site, surrounding vegetation and land cover. Restoration of target vegetation in the quarries by spontaneous succession is possible and can occur within about 25 years, especially if the target species are present close by.

Bruun H. H., Valtinat K., Kollmann J. & Brunet J. (2010): Post-dispersal seed predation of woody forest species limits recolonization of forest plantations on ex-arable land. – Preslia 82: 345–356.
Reforestation of ex-arable land in temperate regions increases the area of potential habitat for forest plants. However, the herbaceous plant layer of these plantations contains fewer forest species than comparable plantations at continuously forested sites. One of the reasons for this might be differences in recruitment. The present study addresses post-dispersal seed predation, mainly of woody plants, as the factor limiting the recolonization of young oak plantations in southern Sweden. Our objectives were to investigate differences in dispersal and post-dispersal seed predation between first-generation forest plantations on ex-arable land and re-planted clear-cuts on continuously forested land. There was no recruitment following the experimental sowing of six commonwoody species (Alnus glutinosa, Betula pendula, Frangula alnus, Sambucus nigra, Sorbus aucuparia and Sorbus intermedia). Thus, the colonization of forest plantations by native shrubs and trees appears to be habitat-limited; the only exception being Rhamnus catharticus, for which poor dispersal ability may be more important. Post-dispersal seed predation of forest shrubs and trees was marked, especially in relatively small and isolated plantations on ex-arable land. There was a high seed predation of Crataegus monogyna, Sorbus aucuparia and Viburnum opulus on ex-arable land, while that of Frangula alnus and Sambucus racemosa was not associated with site placement and land-use history. Seed predation is probably a more important factor limiting restoration of near-natural forests than previously thought.

Ekrt L. & Hrivnák R. (2010): Asplenium platyneuron, a new pteridophyte for Europe. – Preslia 82: 357–364.
Eleven plants of Asplenium platyneuron (ebony spleenwort) were found in disturbed serpentine woodland in south-central Slovakia (Central Europe). This find represents a new addition to the fern flora of Europe. It is probably the result of long-distance spore dispersal. The nearest known sites for this species are those in eastern North America, about 6500 km away. The important determination characters of A. platyneuron are described, the Slovakian locality characterized and an overview of the ecology and a map of the worldwide distribution of this species provided.

Moravcová L., Pyšek P., Jarošík V., Havlíčková V. & Zákravský P. (2010): Reproductive characteristics of neophytes in the Czech Republic: traits of invasive and non-invasive species. – Preslia 82: 365–390.
This paper describes the reproductive characteristics of 93 neophytes (alien species introduced after 1500 A.D.) of the flora of the Czech Republic and compares trait values between naturalized invasive and naturalized non-invasive neophytes. Species were sampled and seed collected in the field from multiple localities in the Czech Republic. Traits related to seed production (propagule number per plant and per population), dispersal (propagule size, length/width ratio and weight; buoyancy; epizoochory; terminal velocity) and establishment (germination; seedling relative growth rate; seedling establishment) were measured for each species either in the field, in a common garden experiment or in the laboratory. Invasive species significantly differ from naturalized non-invasive species in propagule length/width ratio (by having lower ratio, i.e. more rounded propagules) and fecundity (invasive species are more fecund, both per individual plant and in terms of the population propagule production). Invasive species have proportionally fewer seedlings establishing in the autumn and better capacity for dispersal by wind than non-invasive species. The results for several traits differ depending on whether or not the effect of phylogeny is included in analytical models. Considering species relatedness expressed as a taxonomic hierarchy, invasive species have lighter propagules and higher population propagule numbers, and marginally significantly differ in producing more propagules per plant and having higher capacity for dispersal by water. We found that most variation in invasiveness is linked to variation among species within genera. This distribution of relatedness means that predictions of whether a species will become invasive cannot be based on traits of the relatives of the given species at higher taxonomic levels. The distinction made in this paper, i.e. invasive species vs. naturalized but non-invasive species, can potentially contribute to a deeper understanding of the role of traits associated with invasiveness because the crucial transition from the naturalized to invasion stage is rarely addressed in invasion ecology.

Bureš P., Šmarda P., Rotreklová O., Oberreiter M., Burešová M., Konečný J., Knoll A., Fajmon K. & Šmerda J. (2010): Pollen viability and natural hybridization of Central European species of Cirsium. – Preslia 82: 391–422.
Pollen viability was analysed causally between and within Central European Cirsium species and their hybrids to determine (i) how frequently hybrids are fertile and produce viable pollen; (ii) how the pollen viability of hybrids and their parents are related and how this is affected by the genetic distance between parents; (iii) how species promiscuity relates to species pollen viability; (iv) to what extent the pollen viability of a hybrid may predetermine its frequency in nature; (v) how the pollen viability of a hybrid and sympatricity of its parental species are related; and (vii) how the frequency of females in populations of gynodioecious species may affect the observed pollen viability. Altogether, the viability of 656,363 pollen grains was analysed using Alexander’s staining (1185 flowers from 301 plants from 67 field populations of 13 pure species and 1693 flowers from 345 plants from 96 field populations of 16 natural hybrids). The particular characters potentially related with pollen viability were estimated using following methods: natural hybrid frequency and species interfertility (by herbarium data), genetic distance (by AFLP), sympatricity (in local scale based on herbaria and literature data; on a global scale using the similarity between digitized maps of natural ranges). The strengths of pre- or postzygotic isolation were estimated for hybridizing species pairs using geographical data and pollen viability analyses. All hermaphrodite plants of the Cirsium hybrids had viable pollen, generally at lower levels than those found in pure species. The pollen viability of a hybrid generally decreased with increasing genetic distance between the parents and when the parental species had lower pollen viability. The pollen viability was decreased in frequently hybridizing species where occasionally individuals of pure species morphology may show decreased pollen viability. In some instances these might represent some unrecognized hybrid backcrosses. In populations of gynodioecious species where females co-occurred, pollen viability (in hermaphrodites) was also lower, indicating some degree of inbreeding depression. Hybrids between sympatric species exhibited higher post-pollination isolation (decrease of pollen viability), which suggests that the reproductive isolation had been increased by natural selection (effect similar to the Wallace effect). The strength of the postzygotic barrier (based on pollen viability) was generally stronger than that of the prezygotic barrier (based on distribution overlap) in studied hybridizing species pairs.

Konvalinková P. & Prach K. (2010): Spontaneous succession of vegetation in mined peatlands: a multi-site study. – Preslia 82: 423–435.
This study was conducted at 17 peatlands in the Czech Republic mined either by the traditional block-cut method or industrially. Phytosociological reléves of 5 × 5 m were carried out in representative parts of successional stages in disturbed peatlands. Age and environmental characteristics were assessed for each relevé (position of water table, water pH, substratum chemistry, geographical area) or each locality (altitude, average annual temperature and precipitation). Phytosociological reléves recorded in natural vegetation, representing the respective target stages, were included into some analyses. Altogether, 210 relevés were analysed by the DCA ordination. Separately, relevés from milled and block-cut sites were elaborated by CCA with marginal and partial effects calculated. Despite the great variability in vegetation, especially among industrially harvested sites, there is a general tendency for peatland vegetation to recover spontaneously, especially at traditionally harvested sites, which all were, however, older than 50 years. The vegetation at the younger industrially harvested sites exhibited only a tendency to recover. All environmental variables investigated had at least some significant effect on the vegetation pattern, among them, soil pH, water table, nitrates, successional age and geographical location were most important. Abiotic site factors together and geographical location appeared to be more important in determining species composition than successional age.

Křišťálová V., Chrtek J., Krahulcová A., Bräutigam S. & Krahulec F. (2010): Populations of species of Pilosella in ruderal habitats in the city of Prague: frequency, chromosome numbers and mode of reproduction. – Preslia 82: 437–464.
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 × 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.

Phillips M. L., Murray B. R., Pyšek P., Pergl J., Jarošík V., Chytrý M. & Kühn I. (2010): Plant species of the Central European flora as aliens in Australia. – Preslia 82: 465–482.
The Central European flora is an important source pool of plant species introduced to many regions throughout the world. In this study, we identified a total of 759 plant species of the Central European flora that are currently recognized as alien species in Australia. We explored temporal patterns of introduction of these species to Australia in relation to method of introduction, growth form, naturalization status and taxonomy. Across all species, substantially larger numbers of species were introduced between 1840 and 1880 as well as between 1980 and the present, with a small peak of introductions within the 1930s. These patterns reflect early immigration patterns to Australia, recent improvements in fast and efficient transportation around the globe, and emigration away from difficult conditions brought about by the lead up to the Second World War respectively. We found that the majority of species had deliberate (69%) rather than accidental (31%) introductions and most species have not naturalized (66% casual species, 34% naturalized species). A total of 86 plant families comprising 31 tree species, 91 shrub species, 533 herbaceous species and 61 grass species present in Central Europe have been introduced to Australia. Differential patterns of temporal introduction of species were found as a function of both plant family and growth form and these patterns appear linked to variation in human migration numbers to Australia.

Viard-Crétat F., Gross N., Colace M.-P. & Lavorel S. (2010): Litter and living plants have contrasting effects on seedling recruitment in subalpine grasslands. – Preslia 82: 483–496.
In the internal French Alps, subalpine grasslands become dominated by the tussock grass, Festuca paniculata, when mowing ceases. Does litter or living plants affect seedling recruitment in these subalpine communities, and does this vary between mown and unmown grasslands? Can the vegetation patterns observed in the field be related to the effects of F. paniculata? These hypotheses were tested using both a field and pot experiment. Seedlings of Bromus erectus, a subordinate species in these grasslands, were used as phytometers in both experiments. At both mown and unmown subalpine grassland sites in the French Alps, a removal experiment was established. This field experiment included removal of litter and living vegetation in order to differentiate their respective effect on seedling establishment. Vegetation and litter had contrasting effects. Vegetation affected the recruitment success of B. erectus by limiting seedling growth at the mown site and survival at the unmown site. Litter modified recruitment only at the unmown site, where it increased survival but limited growth. Survival and growth of seedlings responded to different environmental factors. Survival was determined more by soil moisture, while growth probably depended more on light availability. Where there is a thick litter layer, as is the case in unmown subalpine grasslands, the competitive effect of vegetation can be counterbalanced by an increase in soil moisture due to the litter reducing rate of evaporation of water. The effect on seedlings of the presence of Festuca paniculata, the dominant species at these sites, was also quantified using a pot experiment, including a cutting treatment. This experiment showed that the competitive effect of the vegetation could be largely explained by the inhibitory effect on growth of the dominant species, F. paniculata. This study provides a better understanding of the processes that result in conservative plants, such as F. paniculata, becoming dominant in these subalpine environments upon cessation of traditional management practices.

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