Sekulová L., Hájek M., Hájková P., Mikulášková E. & Rozbrojová Z. (2011): Alpine wetlands in the West Carpathians: vegetation survey and vegetation–environment relationships. – Preslia 83: 1–24.
Wetland vegetation in the sub(alpine) zone of the West Carpathians (Poland, Slovakia) was studied with particular reference to the following questions: (i) What are the main types of (sub)alpine fen, bog and spring vegetation above the timberline in the West Carpathians? (ii) Which major environmental gradients are associated with the variation in floristic composition? (iii) What determines the α-diversity of bryophytes and vascular plants in the different vegetation types? Vegetation plots were sampled and direct measurements of certain environmental characteristics recorded. Cluster analysis was used to distinguish the vegetation types, DCA and CCA to reveal the main vegetation gradients and environmental factors, and general regression models to identify the factors determining the α-diversity. Classification at the level of 12 clusters was ecologically and syntaxonomically interpretable. Two associations not mentioned in the most recent vegetation survey of Slovakia were distinguished and the syntaxonomical positions of others revised. The synthesis of collected and published vegetation data for the two countries has modified the classification concept of (sub)alpine wetlands in the West Carpathians. Whereas pH predominantly determined floristic differences among classes, different factors governed the species composition within classes. While the diversity of the vegetation of springs (Montio-Cardaminetea) was mostly determined by water chemistry, altitude and geomorphology appeared to be more important within fens and bogs. The species richness of spring vegetation was more influenced by mineral richness than water pH and for bryophyte richness the slope inclination was also important. The species richness of fens and bogs increased with pH. It is concluded that the ecological gradients influencing the floristic composition and species richness of (sub)alpine wetlands are strongly habitat-dependent.

Rotreklová O., Bureš P., Řepka R., Grulich V., Šmarda P., Hralová I., Zedek F. & Koutecký T. (2011): Chromosome numbers of Carex. – Preslia 83: 25–58.
Chromosome numbers were determined for 97 samples of 95 sedge taxa (Carex) from the following countries: Austria (6 records), Bulgaria (1), the Canary Islands (Spain, 1), Cape Verde (1), the Czech Republic (51), Hungary (1), Italy (2), Norway (8), Russia (15), Slovakia (1), Sweden (1) and 9 North American plants cultivated in Czech botanical gardens. Chromosome numbers for Carex argunensis, C. callitrichos, C. campylorhina, C. flavocuspis subsp. krascheninnikovii, C. paniculata subsp. hansenii, C. pallida, C. quadriflora and C. xiphium are reported here for the first time. The first reports are presented for the European portion of the distribution area of Carex obtusata and for the Central European portion of the distributional areas of C. chordorrhiza, C. otrubae, C. rhizina and C. strigosa. New counts for the Czech Republic fill the gaps in the karyological data for this genus in relation to the Flora project in the Czech Republic.

Olšavská K., Perný M., Kučera J. & Hodálová I. (2011): Biosystematic study of the Cyanus triumfetti group in Central Europe. – Preslia 83: 59–98.
Multivariate morphometrics and an assessment of genetic diversity obtained using amplified fragment length polymorphism (AFLP) were used to determine the variability of the polymorphic group Cyanus triumfetti in Central Europe. The ploidy level of the populations studied was also determined; all individuals from the C. triumfetti group were diploid (2n ~ 2x ~ 22) and all those of the related C. montanus group were tetraploid (2n ~ 4x ~ 44). A multivariate morphometric study of 71 populations revealed that three species from the C. triumfetti group occur in Central Europe, namely ‘Cyanus axillaris’, C. strictus and C. dominii. Three subspecies are recognized within the latter species, namely C. dominii subsp. dominii, C. dominii subsp. slovenicus and C. dominii subsp. sokolensis. Morphological characters of leaves are the best features for delimiting these taxa; a shift in characters caused by cultivation did not affect the value of key characters and differences among the taxa remained. AFLP analysis of 38 populations from the C. triumfetti group and two from the C. montanus group revealed a contrasting pattern of genetic variation that was related to the geographic distribution of the populations rather than the morphological variation in the C. triumfetti group. The AFLP data revealed the following three genetically differentiated and allopatric groups: (i) C. triumfetti s.s. and C. montanus from the Western Alps, (ii) ‘C. axillaris’ from Austria and the Czech Republic (except the Carpathians) and (iii) ‘C. axillaris’, C. strictus and C. dominii from the Western Carpathians and Pannonia. The striking genetic gap between the Austrian-Czech and the W Carpathian-Pannonia groups and the high genetic diversity and weak genetic differentiation within the latter group are discussed in the light of potential glacial refuges, postglacial migration routes and/or the probability of hybridization events occurring during the evolutionary history of this group. An identification key for the taxa of the C. triumfetti group in Central Europe is presented.

Trávníček B. & Žíla V. (2011): Rubus silvae-bohemicae: a new species of bramble from Bohemia and Bavaria. – Preslia 83: 99–110.
Rubus silvae-bohemicae is described as a new regional apomictic species belonging to the subgen. Rubus sect. Rubus ser. Micantes Sudre. It is a nemophilous bramble occurring in south-western and southern Bohemia (Czech Republic) and adjacent parts of Bavaria (Germany). It differs from the somewhat similar species, R. indusiatus Focke, by having no stellate hairs on the undersides of the leaves and a lower number of shorter stalked glands and lower number of prickles on first-year stems. An illustration of the new species (including a photograph of the type specimen), a list of localities and a distribution map are presented.

Pröll G., Dullinger S., Dirnböck T., Kaiser C. & Richter A. (2011): Effects of nitrogen on tree recruitment in a temperate montane forest as analysed by measured variables and Ellenberg indicator values. – Preslia 83: 111–127.
The UNECE-ICP Integrated Monitoring site Zöbelboden in the Northern Alps of Austria was established to assess the effects of air pollutants on forest ecosystems. Changes in recruitment of the dominant tree species may be among these effects but there is little information on how germination and juvenile growth of these species respond to changes in nutrient supply. This study focused on the effects of nitrogen availability on the performance of the early life history stages of Picea abies, Fagus sylvatica, Fraxinus excelsior and Acer pseudoplatanus based on measured soil variables and Ellenberg indicator values. For 106, 0.5 × 0.5 m plots, the pH-value, NH₄⁺, NO₃^–, gross and net N mineralization and C:N ratio ot the top mineral soil were analyzed. Additionally, incoming solar radiation and estimated number of seeds arriving in each plot were recorded. Recruitment and juvenile growth rates of the tree species were related to these variables and to mean Ellenberg indicator values calculated from the vascular plant species composition of the plots, respectively, using linear or generalized linear mixed models. Despite the relatively high correlations of Ellenberg indicator values with the three measured soil variables, namely pH, ammonium, and, in particular, gross N mineralization, models using measured variables and Ellenberg indicator values produced inconsistent results in most cases. In general, closer correlations were obtained between measured soil variables and tree performance than between Ellenberg indicator values and tree performance. Measured nitrogen variables had a significant effect on the recruitment and growth of Fagus sylvatica and Acer pseudoplatanus. However, whereas the growth of both species was similarly greater where NH₄ contents and gross mineralization rates were higher, their responses to soil nitrogen were clearly distinct in terms of recruitment. Finally, neither recruitment nor growth of Fraxinus excelsior are significantly correlated with any of the measured nitrogen variables. Partitioning of regeneration niches in terms of different nitrogen sources and supply rates might hence contribute to the co-existence of different tree species in such mixed mountain forests.

Svoboda D., Peksa O. & Veselá J. (2011): Analysis of the species composition of epiphytic lichens in Central European oak forests. – Preslia 83: 129–144.
This paper deals with the species composition of epiphytic lichens in Central European oak forests. A total of 192 oak trees at 48 localities in the Czech Republic, Slovakia and Hungary were investigated. In total, 104 lichen species were recorded and divided into three groups in accordance with their frequency of occurrence on trees within the area. The importance of abiotic factors affecting species composition was assessed by multivariate statistics. Principal component analysis illustrated that lichen assemblages reflected geographical distribution of localities and that the occurrence of many species is closely associated with several environmental factors. In particular there is a high negative association with pollution, and positive associations with precipitation, solar radiation and basic bedrock. The variation partitioning estimated the influence of environmental parameters, human impact and naturality factors on lichen composition. Cluster analysis recognized six communities of lichens, of which the members differed from those in the other communities in their autecological characteristics. Two of the communities can be assigned to Parmelion caperatae and Pertusarion amarae and seem to be similar to natural lichen communities of oak forests in Central Europe. Possible reasons for absence of several epiphytic lichen associations (Lobarion pulmonariae, Pertusarion hemisphaericae) in the forests studied is discussed and the species composition in Central Europe was compared with the lichen assemblages in oak forests in neighbouring regions (western Europe, Scandinavia). On the basis of these findings several indicative species of close to natural oak forest are suggested (Acrocordia gemmata, Bacidia rubella, Calicium spp., Caloplaca lucifuga, Cetrelia olivetorum s.l., Chrysothrix candelaris, Flavoparmelia caperata, Melanelia subargentifera).

Kováčik Ľ., Jezberová J., Komárková J., Kopecký J. & Komárek J. (2011): Ecological characteristics and polyphasic taxonomic classification of stable pigment-types of the genus Chroococcus (Cyanobacteria). – Preslia 83: 145–166.
Two differently coloured strains of the genus Chroococcus were isolated from a cyanobacterial assemblage collected from the stony littoral of a backwater of the Danube River in southern Slovakia. When grown after isolation, both subcultures were similar morphologically and their growth parameters did not differ substantially, but their pigment content (PC: PE and carotenoid ratios), details in their morphology during their life cycles and slime production were different. Identical and different characters of both morphotypes remained stable during cultivation on both agarized and liquid media, even when the cultivation parameters were changed. Both of the subcultures were studied using electron microscopy and almost their complete 16S rRNA genes were sequenced, which showed that in terms of their genetic relationship there was a 96.4% sequence similarity and certain taxonomic interspecific differences between both subcultures were confirmed. The various chromatic modifications recorded in cyanobacteria and their ecological consequences are discussed. The results yielded further data on the changes that occur during the cyanobacterial differentiation processes and their genetic stabilization.

Hašler P., Dvořák P., Ondřej V., Kitner M., Hloušková P. & Poulíčková A. (2011): The importance of the polyphasic approach in a comparative study of Nodularia (Nostocales, Cyanobacteria). – Preslia 83: 167–182.
This paper focuses on the morphology, taxonomy and ecology of the widespread cyanobacteria of the genus Nodularia Mertens ex Bornet & Flahault. In this study the benthic strain of N. sphaerocarpa, isolated from a sand-pit near Olomouc (Czech Republic), is compared with brackish and seawater strains. Changes in morphology and growth parameters (biomass and chlorophyll a) recorded in varying salinity gradients were studied and a 16S rRNA sequencing and AFLP analysis conducted. Morphological and ecophysiological characteristics found were in congruence with molecular data. Three major subgroups of the benthic Nodularia (N. sphaerocarpa, N. moravica and N. harveyana) were found using the polyphasic approach. The results of both the molecular and morphological study clearly separated N. moravica and N. sphaerocarpa, as freshwater species preferring a low salinity and the N. harveyana strains originating from a marine environment preferring a high salinity.

Hájková P., Roleček J., Hájek M., Horsák M., Fajmon K., Polák M. & Jamrichová E. (2011): Prehistoric origin of the extremely species-rich semi-dry grasslands in the Bílé Karpaty Mts (Czech Republic and Slovakia). – Preslia 83: 185–204.
Bílé Karpaty Mts harbour some of the most species-rich managed grasslands in Europe, which contain a number of rare and disjunctly distributed species. Besides specific local environmental factors, the long Holocene history may explain the uniqueness of these grasslands. However, historical interpretations of the palaeoecological evidence from the region are far from unequivocal. While palaeomalacological data indicate persistence of open habitats throughout the entire Holocene, fragmentary pollen data support the hypothesis of a medieval origin of the grasslands. This paper reviews the available phytogeographical, archaeological and palaeoecological knowledge that provides indirect evidence for a prehistoric origin of the grasslands in the Bílé Karpaty Mts. High concentration of rare heliophilous species with a disjunct distribution in the south-western part of the Bílé Karpaty Mts suggest their long-term persistence. The archaeological findings provide evidence for the existence of prehistoric human settlement in this region since the Neolithic (Middle Holocene). Direct evidence for the existence of open human-influenced habitats before medieval times, based on the results of a multi-proxy analysis (macrofossils, molluscs and pollen) of an organic sediment dated back to Roman Age, is also provided. The results indicate the existence of an ancient cultural landscape with a mosaic of open grasslands, natural forests and fields. It is concluded that the evidence presented in this paper supports the hypothesis of prehistoric, rather than a medieval origin of the species-rich grasslands in the Bílé Karpaty Mts.

Bütof A. & Bruelheide H. (2011): Effects of an unspecialized soil pathogen on congeneric plant species with different geographic distributions. – Preslia 83: 205–217.
This study investigated the potential of a root rot causing fungal pathogen to affect the geographical distribution of plant species. A glasshouse experiment was conducted that compared the responses of congeneric plant species of contrasting range types to the presence or absence of a soil borne fungal pathogen at three different moisture levels. Five congeneric plant species pairs were selected, each with one species present and one absent in humid western Europe: Centaurea scabiosa–C. stoebe, Dianthus deltoides–D. carthusianorum, Inula conyzae–I. hirta, Potentilla neumanniana–P. cinerea and Scabiosa columbaria–S. ochroleuca. The oomycete Pythium ultimum was selected as the root rot causing soil borne pathogen because of its wide geographical distribution, wide host range and reported preference for high soil moisture. The response variables measured included relative growth rates of above- and belowground biomass, leaf number and the shoot-root ratio. Two plant species pairs (Dianthus and Scabiosa) showed a significant interaction of distribution type with presence of the pathogen. The species with a continental distribution suffered a greater reduction in growth due to the pathogen than the species with an oceanic distribution. However, across all species and genera the pathogen’s effect was not dependent on range type or soil moisture and affected only RGR of leaf number. The study revealed that unspecialized fungal pathogens might have an effect on the performance of some plant species and might affect continentally distributed species more than oceanic ones, which might put them at disadvantage when combined with, for example, competition. Nevertheless, this effect was not recorded for all genera tested. Given the little knowledge on the effects of unspecialized pathogens on wild plant species, further studies with different soil borne fungal pathogens causing root rot and an enlarged set of plant species are recommended.

Pinke G., Karácsony P., Czúcz B. & Botta-Dukát Z. (2011): Environmental and land-use variables determining the abundance of Ambrosia artemisiifolia in arable fields in Hungary. – Preslia 83: 219–235.
Ambrosia artemisiifolia is the most noxious invasive species of weed in Hungary. The aim of this study was to quantify the environmental and land-use factors that explain the variance in its abundance in arable fields. A survey of 243 arable fields was carried out across Hungary, and 19 environmental and 12 land-use factors were measured. These were used as explanatory variables in classification and regression tree models. The abundance of A. artemisiifolia was significantly higher at the edges than at the centres of fields. The most important land-use variables explaining the variance in abundance of A. artemisiifolia were crop type and crop cover, with the highest abundance recorded in sunflower fields and fields with low crop cover. The following explanatory environmental variables were associated with significantly higher A. artemisiifolia abundance: sandy or acidic soils, mean April precipitation > 39 mm, mean annual precipitation > 592 mm and mean May temperature < 15.5 °C. Ambrosia artemisiifolia was significantly less abundant in fields with soils containing high concentrations of Na, K and Mn. Both farmers and nature conservationists should be made aware of the conditions and practices that favour ragweed so that they can develop effective and selective ragweed control practices, particularly in arable habitats with a high diversity of weeds.

Daneck H., Abraham V., Fér T. & Marhold K. (2011): Phylogeography of Lonicera nigra in Central Europe inferred from molecular and pollen evidence. – Preslia 83: 237–257.
The phylogeographic pattern of the temperate shrub Lonicera nigra (Caprifoliaceae) in Europe was inferred from molecular and fossil data. Population samples and pollen data from most of the contemporary natural distribution were analysed. While chloroplast DNA sequences revealed no intraspecific variation, AFLP data show a non-random geographic pattern. Two genetically different groups, distinguished by Bayesian clustering, divided the distribution area of L. nigra into south-western and north-eastern regions with a contact zone situated approximately in the upper part of the Danube Valley. Iberian populations constitute an additional distinct genetic group. Pollen evidence supports the genetic data, indicating that L. nigra might have survived in glacial refugia located in Central Europe. Nevertheless, this evidence should be considered only as indicative and supplementary, as an unambiguous determination of the species is not possible based on the information on pollen in the literature.

Zalewska-Gałosz J. & Ronikier M. (2011): Potamogeton ×maëmetsiae: a new hybrid between linear-leaved pondweeds from Central Europe. – Preslia 83: 259–273.
The recognition of hybrids of linear-leaved taxa of Potamogeton (sect. Graminifolii) based on morphology is difficult and often debatable. As a consequence, currently only a few hybrid taxa are considered valid and many linear-leaved hybrids described in the past are not now recognized. On the other hand, the use of molecular tools has recently allowed more efficient tests of the origin of morphological forms and the tracking of hybridization events in Potamogeton systematics. In this paper, Potamogeton ×maëmetsiae Zalewska-Gałosz et M. Ronikier nothosp. nov. (Potamogetonaceae), a hybrid between two linear-leaved species, P. friesii and P. rutilus, is described and illustrated. Hybrid plants were collected from two Central-European populations growing in Lake Skaidrys (Lithuania) and Soitsjärv (Estonia). The hybrid origin of the new entity was identified based on a morphological survey and independently confirmed using nuclear (ITS, 5S-NTS) and chloroplast (rpl32-trnL intergenic spacer) DNA sequence data and AFLP analysis of genetic structure. Differences between P. ×maëmetsiae and similar taxa are outlined and other relevant details of the new hybrid discussed.

Jónsdóttir I. S. (2011): Diversity of plant life histories in the Arctic. – Preslia 83: 281–300.
It is argued in this paper that the diversity of plant life histories in the Arctic is much greater than indicated by general descriptions in the literature. Three basic types of life cycle are suggested as a fundamental trait-based framework for exploring the diversity of plant life histories in the Arctic: (i) annual, (ii) non-clonal perennial and (iii) clonal perennial. An overview of current understanding of traits of arctic plant life histories is provided within this framework. Based on the overview it is concluded that (i) there is a substantial diversity of plant life histories in the Arctic, and (ii) there is no single life-history trait that is specific for arctic plants. Furthermore, it is proposed that because arctic environments differ in many respects from other environments, unique combinations of life-history traits are selected among arctic plants. Consequently, arctic plants should express a unique spectrum of life histories. It is also recognized that there are large gaps in the knowledge on arctic plant life-history traits and that fine-tuned trait–habitat relationships may be offset by historical, biogeographical or ecological factors, which may hamper analyses of life history–habitat relationships. On the other hand, it may be rewarding in terms of an improved understanding of functional and evolutionary responses of arctic plants to climate and other environmental changes to identify potential life history syndromes (strategies) among them.

Eriksson O. (2011): Niche shifts and seed limitation as mechanisms determining seedling recruitment in clonal plants. – Preslia 83: 301–314.
This is a review of the evidence on seedling recruitment patterns in clonal forest plants, based on a previously used typology in which the occurrence of seedling recruitment is related to the performance of adult genets: repeated seedling recruitment (RSR), initial seedling recruitment (ISR), recruitment at windows of opportunity (RWO) and systematic spatial variation in seedling dynamics among local populations (RSR/ISR). Generally, seedling recruitment in clonal populations is common and the majority of species have the capacity to recruit within established adult populations. All four recruitment patterns are documented in studies, which include both genetic and demographic evidence that support the existence of a range of variation in seedling recruitment among clonal plants. However, it is suggested that this four-category typology should be replaced by a framework based on two continuously varying factors: the degree of niche overlap between juvenile and adult life cycle stages (uncoupling of juvenile and adult niches implies “niche shifts”) and of seed limitation during recruitment. This creates a hypothetical continuous space within which all recruitment patterns are placed and stimulates research to focus on identifying mechanisms determining the variation in the recruitment of clonal plants. Some further implications of this framework are briefly discussed.

de Bello F., Doležal J., Ricotta C. & Klimešová J. (2011): Plant clonal traits, coexistence and turnover in East Ladakh, Trans-Himalaya. – Preslia 83: 315–327.
To what extent does plant clonality contribute to the assemblage of species in communities? Two apparently contrasting, and largely untested, hypotheses envisage the potential role of plant clonal traits in community assembly: (i) environmental filters constrain coexisting species to have functionally similar traits (i.e. trait convergence); (ii) niche differentiation selects for functionally dissimilar species (i.e. trait divergence) allowing them to exploit different spatial and temporal niches. These hypotheses are assessed using a large dataset of 369 plots (100 m²) covering altitudes between 4100 and 5800 m a.s.l. and including the major vegetation types found in Ladakh, NW Himalaya. Patterns of clonal traits, coexistence and turnover were assessed using a functional diversity partitioning framework in the context of different null models. Functional diversity was expressed both for morphologically delimited clonal growth forms (17 categorical growth forms) and for functionally delimited clonal characters (combining 16 different traits differentiating the 17 growth forms). PERMANOVA revealed that both α (within-plots) and β (between-plots) functional diversity varied across environmental conditions and vegetation types highlighting a filtering effect on clonal traits. Alpha diversity, however, was more stable across habitats than β diversity. Despite the significant turnover of clonal traits across habitats, most of the diversity of clonal traits was found within plots, with a higher trait divergence than expected by chance, which suggests that niche differences determine species coexistence. While both trait convergence and trait divergence were detected, convergence was stronger when using null models that shuffled all species in the regional pool across plots and functional diversity expressed in terms of different clonal growth forms. Divergence, in contrast, was detected mostly when using null models that shuffled species cover across species co-occurring in given plots and considering functional diversity in terms of clonal traits. By detecting both trait convergence and trait divergence this study supports both initial hypotheses and brings new evidence on the relevance of clonal traits as a function of species that both inhabit different environments and coexist.

Schamp B., Hettenbergerová E. & Hájek M. (2011): Testing community assembly predictions for nominal and continuous plant traits in species-rich grasslands. – Preslia 83: 29–346.
We investigated patterns of trait-based community assembly in grasslands sampled along a moisture gradient (216 species) using three continuous species-level traits (maximum species height, minimum species height, seed mass), as well as seven nominal traits (flowering phenology, fruit type, pollen vector, clonal growth organs – CGOs, branching type, leaf distribution, lateral spread), some of which are unusual in that a species may possess more than one state per trait simultaneously (e.g. CGO). Additionally, this study tests whether patterns of assembly vary with plot biomass and moisture using both presence-absence and abundance-weighted analyses (two plot sizes: 25 × 25 cm, 75 × 75 cm). Plant species in these grasslands were randomly organized with respect to both maximum and minimum species height; however, coexisting plant species had a significantly smaller mean seed mass than expected by chance, and were significantly convergent in seed mass, consistent with observations from one previous study, and with theory related to environmental or competitive filtering. These patterns were consistent across plot sizes, and were similar whether analyses were abundance-weighted or not, although partitioned analyses show that these patterns are most pronounced in wet grasslands. Grasslands were non-randomly assembled with respect to five of our ten traits including seed mass, fruit type, CGO, branching type and leaf distribution. Among these, only patterns of branching type clearly conformed to the predictions from Limiting Similarity Theory, suggesting that variation in this trait may contribute to species coexistence in these grasslands. In two cases (fruit type, branching type), results differed in significance depending on whether analysis used presence-absence or abundance data; incorporating abundance may be more relevant, however, cover-based abundance measures in small plots can bias trait representation in favour of size over ramet number. In general, patterns were consistent across the two plot sizes. For four traits (seed mass, flowering phenology, leaf distribution and lateral spread) plot-level effect sizes of our tests varied significantly with plot-level biomass production; the slope of these relationships was positive for seed mass, but negative for flowering phenology, leaf distribution and lateral spread. For seven of ten traits, plot-level effect sizes varied significantly with plot-level soil moisture, with positive regression slopes for some traits (flowering phenology, leaf distribution), and negative slopes for others (minimum height, seed mass, fruit type, pollen vector, CGO). These results indicate that community assembly rules related to different functional traits can be responsive to variation in either biomass or soil moisture, or both.

Schleicher A., Peppler-Lisbach C. & Kleyer M. (2011): Functional traits during succession: is plant community assembly trait-driven? – Preslia 83: 347–370.
Little is known about changes in the significance of environmental filtering and neutral processes during the succession of plant communities. Generally, a succession is expected to be trait-driven and a shift is predicted from high importance of seed dispersal ability in initial phases to importance of strong competitive ability in later stages. In this study, we consider a community assembly trait-driven in the case of a shift in functional traits during succession and randomly assembled in the case there is no shift in functional traits during succession. We therefore tested whether urban plant communities show trait convergence or trait divergence in relation of successional stage, water and nutrient availability. At two scales (100 × 100 cm and 10 × 10 cm), we analysed traits relevant to seed dispersal, stress tolerance and competitive ability and compared real data with null models. We subsequently used regression trees to associate convergence and divergence to plot age and stress due to low water and soil nutrient availability. Most traits were neither significantly convergent nor divergent and the variance explained by the regression trees was often lower than 20%. We found divergence in seed number instead of the expected convergence towards high seed number. In accord with expectations we found low seed terminal velocity and annual life span in early succession. Convergence in seed bank longevity occurred at intermediate plot age, and convergence in the combination of life span and lateral spread showed the relevance of competition filtering in the most fertile plots. On the other hand, competition-induced convergence in canopy height or specific leaf area was not supported by our results. We concluded that, based on the traits considered in this study, the overwhelming evidence was that community assembly during the first 40 years of succession was driven by trait-neutral mechanisms.

de Witte L. C., Scherrer D. & Stöcklin J. (2011): Genet longevity and population age structure of the clonal pioneer species Geum reptans based on demographic field data and projection matrix modelling. – Preslia 83: 371–386.
Genet life span is a key demographic trait for understanding life history of plants. However, the longevity of clonal plants is hard to determine, especially when inter-ramet connections are short-lived and plants subsequently move independently of one another in space by means of an expansive growth strategy. In this study we estimated genet life span in the clonal pioneer species Geum reptans, living on glacier forelands, by using a projection matrix model based on demographic field data of ramets collected at two sites and in three subsequent years. We then calculated genet age structure at different population ages using multiple simulations, including a maximum carrying capacity and density-dependent mortality. Additionally, we estimated the age of the two field populations by comparing results from simulations with population structure recorded in the field. According to our simulations, more than half of the genets die within the first three decades. However, a considerable proportion survived more than 50 years and some genets even became immortal as they produced so many ramets that the risk of the entire genet becoming extinct was zero. Simulated genet age structures were strongly left skewed with many young and a few very old genets. The rather low carrying capacity was reached only after 350 years, after which density-dependent mortality started to influence genet age structure considerably. The age of the two field populations was estimated to be 250 and 450 years, respectively. Results indicate that in clonal plants, genet immortality can potentially lead to unlimited persistence of established populations. In the case of G. reptans, old populations may experience competition and increased mortality due to the ongoing succession in older parts of the glacier foreland that will prevent populations reaching their maximum carrying capacity. But due to the ability of this plant to colonize new sites and follow retreating ice on glacier forelands, populations of G. reptans can be very old as recorded here for the two field populations in the Swiss Alps.

Erschbamer B., Unterluggauer P., Winkler E. & Mallaun M. (2011): Changes in plant species diversity revealed by long-term monitoring on mountain summits in the Dolomites (northern Italy). – Preslia 83: 387–401.
Vegetation on mountains is expected to react in a highly sensitive way to climate change and species losses are predicted in the near future. By means of monitoring studies changes in species diversity can be continuously recorded. In this paper the results of a 7-year study in the Southern Alps are reported. As part of the worldwide network GLORIA (The Global Observation Research Initiative in Alpine Environments) four summits, at altitudes ranging from the treeline to the alpine-subnival ecotone (2199, 2463, 2757 and 2893 m a.s.l.) in the Dolomites (northern Italy) were studied. Sites on the four summits were used to determine the effects of climate warming and observe changes in the numbers of species of vascular plants, frequency and composition. It is hypothesized that ‘thermophilization’ is likely to occur over a period of 7 years (i.e. species from lower altitudes are expected to migrate to the summits due to climate warming). It is also hypothesized that nival, alpine-subnival and endemic species might decrease due to competitive displacement by species from lower altitudes. The summit areas were comprehensively sampled (from the highest point down to the 10 m contour line) in 2001, 2006 and 2008. In addition, 4 × 1 m ² permanent plots located 5 m below the highest summit point on the north, south, east and west sides of each summit were sampled. The results of revisiting the summits indicate that the number of species increased on all four summits, with the greatest gains (15% and 18%) recorded on the two highest summits and moderate gains (4% and 9%) on the two lower summits. Species’ frequencies within the 1 m² plots also increased during the 2001–2008 period. A thermophilization trend was demonstrated in which species with distribution centres in the montane or tree line zones were found for the first time on three of the summits. On the lowest summit, the vigorous growth of trees and establishment of new saplings indicate an upward migration of the forest boundary. Species that disappeared from the four summits belonged to species with different altitudinal ranges; however, nival and subnival-alpine species remained. One endemic species, Potentilla nitida, disappeared from the highest summit. Further changes and clearer trends are expected in the next decade.

Koutecká E. & Lepš J. (2011): Performance of three closely related Myosotis species in an experiment in which substrate quality and competition were manipulated. – Preslia 83: 403–420.
Closely related species can be used for studying the ecological significance of their traits. The response in terms of survival, clonal growth and vegetative and generative characteristics of three related Myosotis species to competition and soil characteristics were studied in a three year pot experiment. Plants from four populations per species were cultivated in a factorial combination of substrate (nutrient-rich soil and mixtures with sand) and competition (with or without Holcus lanatus) treatments. Survival, clonal growth and the majority of the growth characteristics of all three Myosotis species were reduced by competition. The effect of substrate was less pronounced, and variable for various traits: the soil with sand mixture was more suitable for survival, clonal growth and seed germination whereas in the nutrient-rich soil plants were taller, but this effect was modified by competition. The differences among species corresponded well to expectation based on their known habitat preferences. Myosotis caespitosa, a species typical of short-term habitats such as emerged bottoms of ponds, exhibited the shortest life span and was also the most sensitive to competition: all plants of this species died in the competition treatment before the end of the second season. Nevertheless, the surviving plants (in the no-competition treatment) were able to form several daughter rosettes or stolons; some of them spread clonally till the third year. Myosotis palustris subsp. laxiflora, which inhabits the banks of rivers and brooks often disturbed by torrential floods, survived best and had the highest potential for clonal growth and spreading. Most plants of this species produced rhizomes and stolons and spread the furthest of all the three species. Myosotis nemorosa, which lives mostly in meadows, the most stable habitat of the studied congeners, but also a habitat with a strongly competitive matrix of species, was intermediate in terms of survival, and clonal growth, forming mainly short rhizomes. This species exhibited the highest among-population variability in all recorded characteristics, which might be due to its local adaptation to a wide spectrum of habitats. We argue that the details of prevailing disturbance regime, rather than some general disturbance intensity explain the clonal behaviour of the species compared.

Poschlod P., Hoffmann J. & Bernhardt-Römermann M. (2011): Effect of grassland management on the age and reproduction structure of Helianthemum nummularium and Lotus corniculatus populations. – Preslia 83: 421–435.
Dry calcareous grasslands are among the most species-rich and endangered ecosystems in the Central- European landscape. They are of anthropogenic origin and mainly a result of grazing by domestic animals. Due to land-use changes in the last century, particularly in the 1960s, they were often abandoned or afforested. Therefore, in 1975 long-term experiments were started in the southwestern Germany (Baden-Württemberg) to determine the effectiveness of alternative management treatments in maintaining grasslands and their species composition. The aim of this study was to assess the effect of grazing (reference management treatment), mowing once a year, mulching twice a year, mulching every second year, burning once a year and succession (abandonment) on the population structure (in terms of density, age structure, reproduction mode) and seasonal germination niche of a dwarf shrub, Helianthemum nummularium, and a herbaceous plant, Lotus corniculatus. To study the age structure, annual ring analyses were applied. The classification of the reproduction mode, either by seed or vegetatively, was carried out by differentiating the central under-ground organ either as a root (in this case the individual has established from seed) or rhizome (the individual has developed from clonal multiplication). The seasonal germination niche was derived from the age structure. Management clearly affected population density and age structure. Highest density of individuals was found in the grazing and the lowest in the succession treatment. In the mulching every second year and succession treatments populations were senescent. Management also affected reproduction mode in H. nummularium. Regeneration by seed was especially enhanced by mowing and burning but was inhibited by mulching twice and succession. In the latter treatments H. nummularium reproduced only clonally. Helianthemum nummularium germinated mainly in autumn but burning by breaking the dormancy of seeds initiated germination in spring. A similar pattern was detected in L. corniculatus: burning increased germination rate in spring. Comparing population characters (density, age, reproduction mode) to the traditionally used grazing treatment, mowing was most similar and for L. corniculatus additionally burning. This is in contrast to the assessment of the vegetation of the management treatments where mowing and mulching twice per year maintain a similar floristic composition. Finally, the analysis of the population structure revealed important mechanisms behind population and vegetation dynamics.

Klimešová J., Janeček Š., Horník J. & Doležal J. (2011): Effect of the method of assessing and weighting abundance on the interpretation of the relationship between plant clonal traits and meadow management. – Preslia 83: 437–453.
The role of clonal traits in a plant’s response to changes in management of semi-natural grasslands is poorly known and the few studies examining their importance have yielded contradictory results. For a better understanding of the role of plant functional traits in determining competitive ability and clonal growth in response to early changes in management, we mowed and applied fertilizer to 22 wet meadows in the Železné hory Mts, Czech Republic. We used two methods of assessing abundance (plant cover and species frequency) to determine whether changes in frequency induced by changes in management are better predicted by clonal traits while changes in cover are mainly determined by competitive traits such as plant height. We evaluated (i) the response of individual species to changes in management and (ii) the response of the whole community, with and without taking abundance of individual plants into account, in order to separate the effect of local extinction and immigration from changes in abundance. The plant functional traits tested were generally found to be important soon after the changes in the management of the semi-natural grasslands occurred: competitively superior resident species (possessing tall erosulate, monocyclic shoots) that are able to spread far and multiply clonally (having a high clonal index) were favoured by applying fertilizer and/or suppressed by mowing. Some other traits supposed to be important in the response to changes in management did not change (persistence of connection between ramets). Results for the two methods of assessing abundance differed; however, neither was better at detecting the response of particular types of traits (i.e. relevant to clonal growth and competitive ability). The initial response of the whole community, with and without taking abundance of individual plants into account, was consistent indicating that species that went extinct possessed the same traits as those that decreased in abundance. The clonal index proved to be a useful characteristic of meadow plants. Our results further imply that (i) the method used to assess abundance significantly affects the output of analyses of the response of functional traits, and (ii) a comparison of analyses based on weighting abundance and unweighted means resulted in a deeper insight into the changes in the spectra of functional traits that occurred after changes in meadow management.

Veeneklaas R., Bockelmann A., Reusch T. & Bakker J. (2011): Effect of grazing and mowing on the clonal structure of Elytrigia atherica: a long-term study of abandoned and managed sites. – Preslia 83: 455–470.
Physical disturbance by large herbivores can affect species diversity at the community level and concurrently genetic diversity at the species level. As seedling establishment is rarely observed in clonal plants, short-term experiments and demographic studies are unlikely to reveal the response of clonal plants to disturbances. A long-term (30-year) field experiment and the availability of molecular markers allowed us to investigate the clonal structure of populations of Elytrigia atherica subjected to different management regimes. The long-term field study provided us with five replicated blocks that had been subjected to three different management regimes, grazing by cattle, mowing and abandonment. In this study we examined the effects of herbivore grazing and mowing on clonal richness and genetic diversity of populations in salt marshes using multilocus microsatellite genotypes. In addition, phenotypic traits and spatial positions of E. atherica ramets were determined for 20 samples in a 5 × 10m plot in each of the blocks. Abundance and phenotypic traits were affected by the management regimes, resulting in a higher abundance in abandoned fields and plants having shorter and narrower leaves in managed fields. Biomass removal did affect the clonal structure of populations and increased the genetic diversity compared to that in abandoned fields. However, no distinct difference was found between the two management regimes, mowing and grazing. Although seedling recruitment has rarely been observed, the present study shows that such rare events have occurred within the populations studied. Thus, molecular tools can greatly increase our understanding of vegetation dynamics and processes within populations growing under different conditions.

Krahulec F., Krahulcová A., Rosenbaumová R. & Plačková I. (2011): Production of polyhaploids by facultatively apomictic Pilosella can result in the formation of new genotypes via genome doubling. – Preslia 83: 471–490.
Haploid parthenogenesis in facultatively apomictic Pilosella generated polyhaploid progeny (with half the maternal chromosome set) both in natural populations and garden experiments. Production of polyhaploids varied considerably among different species, hybridogenous species and hybrids. In the field (14 localities), the highest frequency of polyhaploids exceeded 80% of the total seed progeny produced by some recent hybrids. A similar diversity in the production of polyhaploids was also recorded in garden experiments. A two-step process by which new genotypes of both P. aurantiaca (tetraploid) and P. rubra (hexaploid) were formed under garden conditions during a polyploid–polyhaploid–polyploid cycle is described. In the first step, the maternal plants generated dihaploid and trihaploid F₁ progeny, respectively. Although a substantive part of this polyhaploid progeny was either non-viable or sterile, the apomictic polyhaploids occasionally doubled their genome. Consequently, the F₂ progeny resulting from the second step had a double ploidy level, identical to that of the original maternal parent. The complete process was autonomous, without contribution of pollen from parent genotype. This cycle necessarily implicates increasing homozygosity in F₂ progeny compared to the original maternal polyploid plant. The probabilities of particular steps of this process occurring in Pilosella and the variation in polyhaploids are estimated and described, and the ability of polyhaploid plants to survive under field conditions discussed. Probability of the complete cycle (haploid parthenogenesis followed by doubling of the genome), which occurred under garden conditions in P. rubra, is estimated to be in the order of hundredths of percent. Despite this low probability, it can result in the production of new homozygous genotypes in populations of apomicts, especially in those occurring in disturbed habitats with little competition.

Kirschner J. & Štěpánek J. (2011): Dandelions in Central Asia: a revision of Taraxacum section Stenoloba. – Preslia 83: 491–512.
On the basis of rich material from Asia, a recently described group of dandelions, Taraxacum sect. Stenoloba Kirschner et Štěpánek, is revised taxonomically. Four previously described species are recognized: T. sinomongolicum, newly typified, T. mongoliforme, with a lectotype replacing the original holotype now not extant, and a new epitype, T. scariosum, a new combination of Leontodon scariosus Tausch, replacing the frequently confused names, T. asiaticum, newly typified, and T. stenolobum, and T. multisectum, a taxon for the first time compared with other members of the section. Three new species are described: T. abax occupies a large range from S Siberia and Mongolia to NE China, T. abalienatum and T. odibile are known from Mongolia and SE Siberia. Taraxacum abax and T. abalienatum represent core species of the section Stenoloba, whilst T. odibile exhibits a mixture of characters of sections Stenoloba and Leucantha. All the known members of the section Stenoloba are agamosperms. Taraxacum mongoliforme, T. abax and T. scariosum proved to be triploid with 2n = 24. This account includes detailed descriptions and an identification key.

Šafářová L., Duchoslav M., Jandová M. & Krahulec F. (2011): Allium oleraceum in Slovakia: cytotype distribution and ecology. – Preslia 83: 513–527.
The spatial distribution of cytotypes can provide valuable insights into the evolution of polyploid complexes. Previously, only tetraploid Allium oleraceum was reported from Slovakia. Analysing 863 individuals from 93 populations from Slovakia revealed an extensive variation in the DNA ploidy levels of Allium oleraceum (3x, 4x, 5x and 6x). Of the main cytotypes, the penta- and tetraploids had strongly overlapping distributions, although the pentaploids exhibited a tendency to occur more frequently in the southern and the tetraploids had a tendency to occur in the northern regions of Slovakia. A triploid cytotype was found in one population in the southern part of Slovakia, which is the third locality worldwide for this cytotype. The hexaploid cytotype was rare and sparsely occurred in western and southern Slovakia. Sixteen per cent of the populations sampled consisted of more than one ploidy level; the most common was a combination of penta- and tetraploids. The cytotypes differed with respect to altitude; the tetraploids were found significantly more frequently at higher altitudes than the penta- and hexaploids. When compared with reanalysed altitudinal distribution data from the Czech Republic divided into two geographic areas (Carpathian and Herzynian) the pattern found in the Carpathian part of the Czech Republic was similar to that in Slovakia, with tetraploids at the higher altitudes. The distribution in the Herzynian part (Bohemian Massif) was just the opposite: the tetraploids were more often found at lower altitudes than the penta- and hexaploids. Both tetra- and pentaploid cytotypes occurred in a wide and similar spectrum of habitats, while hexaploids were limited to human-influenced habitats. A local-scale distribution of cytotypes analysed in detail in the Slovak Karst area, showed surprising differences in the distribution of cytotypes on particular karst plains, which can be related to different land uses. Concerning the contrasting altitudinal differentiation of tetraploids in the regions compared, the results suggest that at least two different types of tetraploids occur in Central Europe. The apparent cytotype diversity in the surrounding Slovak Karst area may suggest the existence of a primary contact zone.

Carranza M. L., Ricotta C., Carboni M. & Acosta A. T. R. (2011): Habitat selection by invasive alien plants: a bootstrap approach. – Preslia 83: 529–536.
Even though there is no doubt that an invasion of a landscape by plants is a function of the abundance and spatial arrangement of different types of habitat, to the best of our knowledge, there has been no analysis of the relation between the patterns of plant invasion and the availability of specific habitats within landscapes invaded. The application of habitat selection functions (HSFs) provides a quantitative measure for determining if specific habitats are more likely to be invaded by a given species. The remarkable dynamics of spread of invasive alien plants makes them an ideal species pool for applying HSFs. This paper discusses the possible application of a bootstrap test of significance for identifying habitat types where the incidence of alien species is higher (preferred) or lower (avoided) than would be expected from a random null model for which all habitat types are invaded in proportion to their availability. In order to demonstrate the usefulness of the proposed approach we explored the habitat selection of a coastal alien plant, Carpobrotus aff. acinaciformis, in the Tyrrhenian coastal dunes of central Italy. According to this bootstrap test of significance, some important habitats of European conservation interest were more readily invaded by Carpobrotus than expected. From an applied research perspective, the use of an HSF approach can help identify the most invasion-prone habitats and, therefore, may facilitate the development of a clear and targeted prevention policy to control the introduction and spread of alien species in a landscape, for example, coastal dune habitats.

Štěpánek J., Kirschner J., Jarolímová V. & Kirschnerová L. (2011): Taraxacum nigricans, T. alpestre and allies in the Taraxacum sect. Alpestria: taxonomy, geography and conservation status. – Preslia 83: 537–564.
A long-standing problem with the taxonomic status and synonymy of the names Taraxacum nigricans (Kit.) Reichenb. and T. alpestre (Tausch) DC. is resolved. These two names, the oldest ones referable to high mountain dandelions in Central Europe, are typified, and a detailed comparison of these species’ morphology, genotype make-up, karyotypes and distribution is provided, together with a discussion of other cases of similar and probably closely related agamospermous taxa of Taraxacum and Hieracium. Taraxacum nigricans (2n = 32) and T. alpestre (2n = 32) are endemic to the Nízke Tatry Mts, Slovakia, and the Krkonoše/Karkonosze Mts, Czech Republic/ Poland, respectively. These are shown to differ in a series of minor but constant morphological, allozyme and karyotype features, and their treatment as separate agamospermous species is supported. A detailed analysis of cultivated and wild material from the Carpathians revealed the existence of a sexual taxon very close to the above two species and endemic to the region of the Bucegi Mts, Romania. It is described as a new species, T. carpaticum Štěpánek et Kirschner. Two new agamospermous species, apparently allied to T. nigricans, are described: T. rupicaprae Štěpánek et Kirschner, a species characterized by orange-ochraceous achenes and confined to the High Tatra Mts, and T. elegantissimum Štěpánek et Kirschner (2n = 24), which has substantially broader outer bracts and is known from the Rodna, Retezat and Fagaras Mts, Romania. Another three species are described that are morphological similar to T. carpaticum: T. pastorum (the Fagaras Mts, Romania), T. iucundum (the Retezat Mts, Romania) and T. pseudoalpestre (the Fagaras Mts, Romania).

Rooks F., Jarolímová V., Záveská Drábková L. & Kirschner J. (2011): The elusive Juncus minutulus: a failure to separate tetra- and hexaploid individuals of the Juncus bufonius complex in a morphometric comparison of cytometrically defined groups. – Preslia 83: 565–589.
Screening of nuclear genome size was carried out on ca 2400 plants from over 120 mainly Central- European localities of the Juncus bufonius group. Besides the diploid level, corresponding to known diploid species (in this case J. ranarius, J. hybridus and J. sorrentini), two polyploid cytotypes were detected, conforming with the tetraploid and hexaploid levels treated by some authors as separate species: J. minutulus and J. bufonius s. str. The relationship between nuclear DNA content and the number of chromosomes was verified by chromosome counting. Polyploidy, as opposed to agmatoploidy can, therefore, account for the karyological variation. The 2C values of diploid, tetraploid and hexaploid individuals were ca 0.65, 1.18±2.8% and 1.84±1.6% pg 2C DNA, respectively. No other cytotype or statistically significant variation in nuclear genome size was found. To asses the utility of hitherto published morphological characters distinguishing J. minutulus from J. bufonius s. str., measurements of seven floral and three vegetative quantitative characters were obtained (no less than 10 measurements per flower, 30 per plant) for 358 mature plants of known ploidy level from 47 localities. Diverse ordination and clustering techniques did not indicate the presence of any grouping in the dataset. Canonical discriminant analysis and stepwise variable selection indicated that inner tepal length followed by mean capsule width and mean capsule length were the most useful characters for identifying the two ploidy levels; however, the estimated 10-fold cross-validation error rate of a simple k nearest neighbour classification analysis was 0.45. Other analyses corroborated this result. No new morphological character that would allow successful separation of tetraploids from hexaploids was discovered. This provides independent support for the opinion of some previous authors that J. bufonius L. is best treated as a single variable species comprising two cytotypes that are inseparable using hitherto suggested diagnostic characters until convincing proof to the contrary is available.

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