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River valleys are considered natural corridors for migration of plant species; however, there is a lack of studies confirming higher colonisation rates of plant species in these areas. We compare plant species richness between ancient and recent forests (developed during and after the nineteenth century) and those located in a river valley with those located outside the river valley. We hypothesise that, close to a river, higher plant species richness will be associated with recent forests, thus indicating a higher colonisation rate. The study area includes parts of the Elbe River Valley and a landscape outside the river valley in the Czech Republic. We sampled an equal number of recent and ancient forests (20/20), but lying at different distances from the river. We used generalised linear models to test the effect of distance from the river in dependence upon forest continuity (recent/ancient forest) on two plant species richness categories, i.e. richness of forest species and overall species richness. Outside the river valley, higher richness of forest species was associated with ancient forests, whereas overall species richness was comparable. In the river valley, richness of forest species as well as overall species richness was higher in the recent forests. Recent forests in the river valley were more saturated by plant species than those outside the river valley, indicating that in the river valley, the colonisation rate of plant species is higher. These results confirm the importance of river valleys as natural corridors for migration of plant species.

The biogeographic origin of the species‐rich steppe grasslands in central Europe has long been debated. The alternative hypotheses are long‐term species persistence in situ versus immigration from the south‐east, either after the last glacial maximum (LGM) or after the Neolithic landscape deforestation. We ask whether macroclimate‐based models of habitat suitability support either of these hypotheses and search for macroclimatically suitable ‘source areas' from which species could colonise the areas occupied in Europe today. We modelled habitat suitability for 104 species of the central European steppes and projected these models to 10 periods between the LGM and the present using downscaled CCSM3 simulations. By simulating postglacial migration, we identified potential source areas for each species in the LGM and mid‐Holocene and examined whether their location differed among three ecological and five chorological species groups. The central European macroclimate during the cold phases of the Late Pleistocene was suitable for species now typical of Asian desert steppes, whereas the warmer Bølling–Allerød and Holocene macroclimates supported the occurrence of present‐day central European steppe flora. The models suggest that the LGM source areas of these species ranged from south‐eastern France through the Adriatic region and the Balkan Peninsula to the Black‐Sea region but extended to central Europe in the mid‐Holocene. Their locations differed considerably among ecological and chorological groups in both periods. Therefore, our models support the hypothesis that during the Pleistocene cold periods, the largest populations of these species occurred in southern and south‐eastern Europe and some of them may have later colonised central Europe. If some populations occurred in central Europe during the LGM, as suggested by recent genetic analyses, they were likely restricted to microrefugia embedded in the landscape matrix of species‐poor cold steppe. The precipitation‐rich mid‐Holocene climate had no direct negative impact on the central European steppe flora.

Reticulate evolution is characterized by occasional hybridization between two species, creating a network of closely related taxa below and at the species level. In the present research, we aimed to verify the hypothesis of the allopolyploid origin of hexaploid C. album s. str., identify its putative parents and estimate the frequency of allopolyploidization events. We sampled 122 individuals of the C. album aggregate, covering most of its distribution range in Eurasia. Our samples included putative progenitors of C. album s. str. of both ploidy levels, i.e. diploids (C. ficifolium, C. suecicum) and tetraploids (C. striatiforme, C. strictum). To fulfil these objectives, we analysed sequence variation in the nrDNA ITS region and the rpl32-trnL intergenic spacer of cpDNA and performed genomic in-situ hybridization (GISH). Our study confirms the allohexaploid origin of C. album s. str. Analysis of cpDNA revealed tetraploids as the maternal species. In most accessions of hexaploid C. album s. str., ITS sequences were completely or nearly completely homogenized towards the tetraploid maternal ribotype; a tetraploid species therefore served as one genome donor. GISH revealed a strong hybridization signal on the same eighteen chromosomes of C. album s. str. with both diploid species C. ficifolium and C. suecicum. The second genome donor was therefore a diploid species. Moreover, some individuals with completely unhomogenized ITS sequences were found. Thus, hexaploid individuals of C. album s. str. with ITS sequences homogenized to different degrees may represent hybrids of different ages. This proves the existence of at least two different allopolyploid lineages, indicating a polyphyletic origin of C. album s. str.

We reconstructed the historical pattern of postglacial biogeographic range expansion of the boreal tree species Alnus incana in Europe. To assess population genetic structure and diversity, we performed a combined analysis of nuclear microsatellite loci and chloroplast DNA sequences (65 populations, 1004 individuals). Analysis of haplotype and microsatellite diversity revealed that southeastern refugial populations situated in the Carpathians and the Balkan Peninsula did not spread north and cannot be considered as important source populations for postglacial recolonization of Europe; populations in Eastern Europe did not establish Fennoscandian populations; populations in Fennoscandia and Eastern Europe have no unique genetic cluster, but represent a mix with a predominant cluster typical for Central Europe; and that colonization of Fennoscandia and Eastern Europe took place from Central Europe. Our findings highlight the importance of an effective refugium in Central Europe located outside classical southern refugia confirming the existence of northern refugia for boreal trees in Europe. The postglacial range expansion of A. incana did not follow the model established for Picea abies. Fennoscandian populations are not derived from Eastern European ones, but from Central European ones.

AIM: Formalized classifications synthesizing vegetation data at the continental scale are being attempted only now, although they are of key importance for nature conservation planning. Therefore, we aim to provide a vegetation classification and to describe the main biogeographical patterns of floodplain forests and alder carrs in Europe. LOCATION: Europe. METHODS: A database of more than 40 000 vegetation plots of floodplain forests and alder carrs across Europe was compiled. After geographic stratification, 16 392 plots were available for classification, which was performed using the supervised method Cocktail. We also searched for new associations using semi‐supervised K‐means classification. The main biogeographic patterns and climate‐related gradients in species composition were determined using detrended correspondence analysis and cluster analysis. RESULTS: Thirty associations of floodplain forests and alder carrs were distinguished, which belong to five alliances. The Alnion incanae includes riparian, seepage and hardwood floodplain forests in the nemoral and hemiboreal zones (dominated by Alnus glutinosa and Fraxinus excelsior) and in the boreal zone (dominated by A. incana). The Osmundo‐Alnion represents oceanic vegetation dominated by Alnus glutinosa, Fraxinus angustifolia and F. excelsior distributed mostly on the Iberian Peninsula and composed of species with Atlantic distribution and Iberian endemics. The Populion albae comprises floodplain forests frequently dominated by Fraxinus angustifolia, Populus alba and P. nigra that are widespread in floodplains of large rivers under summer‐dry climates in the Mediterranean region. The Platanion orientalis represents eastern Mediterranean floodplain forests dominated by Platanus orientalis. The Alnion glutinosae includes forest swamps dominated by Alnus glutinosa distributed mostly in the nemoral and hemiboreal zones. The main biogeographic patterns within European floodplain forests and alder carrs reflect the climatic contrasts between the Mediterranean, nemoral, boreal and mountain regions. Oceanic floodplain forests differ from those in the rest of Europe. The hydrological regime appears to be the most important factor influencing species composition within regions. CONCLUSIONS: This study is the first applying a formalized classification at the association level for a broad vegetation type at the continental scale. The proposed classification provides the scientific basis for the necessary improvement of the habitat classification systems used in European nature conservation.

Heterocarpy enables species to effectively spread under unfavourable conditions by producing two or more types of fruit differing in ecological characteristics. Although it is frequent in annuals occupying disturbed habitats that are vulnerable to invasion, there is still a lack of congeneric studies addressing the importance of heterocarpy for species invasion success. We compared two pairs of heterocarpic Atriplex species, each of them comprising one invasive and one non-invasive non-native congener. In two common garden experiments, we (i) simulated the influence of different levels of nutrients and population density on plants grown from different types of fruits and examined several traits that are generally positively associated with invasion success, and (ii) grew plants in a replacement series experiment to evaluate resource partitioning between them and to compare their competitive ability. We found that specific functional traits or competitiveness of species cannot explain the invasiveness of Atriplex species, indicating that species invasiveness involves more complex interactions of traits that are important only in certain ecological contexts, i.e. in specific environmental conditions and only some habitats. Interestingly, species trait differences related to invasion success were found between plants growing from the ecologically most contrasting fruit types. We suggest that fruit types differing in ecological behaviour may be essential in the process of invasion or in the general spreading of heterocarpic species, as they either the maximize population growth (type C fruit) or enhance the chance of survival of new populations (type A fruit). Congeners offer the best available methodical framework for comparing traits among phylogenetically closely related invasive and non-invasive species. However, as indicated by our results, this approach is unlikely to reveal invasive traits because of the complexity underlying invasiveness.

Recently, new palaeoecological records supported by molecular analyses and palaeodistributional modelling have provided more comprehensive insights into plant behaviour during the last Quaternary cycle. We reviewed the migration history of species of subgenus Alnus during the last 50,000 years in Europe with a focus on (1) a general revision of Alnus history since the Last Glacial Maximum (LGM), (2) evidence of northern refugia of Alnus populations during the LGM and (3) the specific history of Alnus in particular European regions. We determined changes in Alnus distribution on the basis of 811 and 68 radiocarbon-dated pollen and macrofossil sites, respectively. We compiled data from the European Pollen Database, the Czech Quaternary Palynological Database, the Eurasian Macrofossil Database and additional literature. Pollen percentage thresholds indicating expansions or retreats were used to describe patterns of past Alnus occurrence. An expansion of Alnus during the Late Glacial and early Holocene periods supports the presence of alders during the LGM in southern peninsulas and northerly areas in western Europe, the foothills of the Alps, the Carpathians and northeastern Europe. After glaciers withdrew, the ice-free area of Europe was likely colonized from several regional refugia; the deglaciated area of Scandinavia was likely colonized from a single refugium in northeastern Europe. In the more northerly parts of Europe, we found a scale-dependent pattern of Alnus expansion characterised by a synchronous increase of Alnus within individual regions, though with regional differences in the times of the expansion. In southern peninsulas, the Alps and the Carpathians, by contrast, it seems that Alnus expanded differently at individual sites rather than synchronously in whole regions. Our synthesis supports the idea that northern LGM populations were important sources of postglacial Alnus expansion. The delayed Alnus expansion apparent in some regions was likely a result of environmental limitations.

Premise Microsatellite markers were developed for the perennial herb Salvia pratensis (Lamiaceae), a species representative of European dry grasslands. The development of microsatellite markers is needed for genetic and phylogeographical studies of species from the genus Salvia. Methods and Results We used low‐coverage Illumina sequencing to identify microsatellite loci. Based on these data, we have developed 18 polymorphic microsatellite markers with the number of alleles per locus ranging from two to 15. The levels of observed and expected heterozygosity ranged from 0.05 to 0.95 and from 0.05 to 0.89, respectively. The majority of the markers successfully cross‐amplified in other Salvia species. Conclusions The markers were shown to be suitable for population genetic and phylogeographic studies in S. pratensis as well as in related species (S. aethiopis, S. austriaca, S. glutinosa, S. nemorosa, S. nutans, and S. verticillata) and will be used in the broader context to trace the origins of European dry grasslands.

Premise A set of polymorphic nuclear microsatellite loci was developed and tested for use in population genetic analyses of Anthericum ramosum (Agavaceae) and related species. Methods and Results Sequences of 110 primers were extracted in silico from Illumina MiSeq genome skimming data. The degree of polymorphism of 19 loci was tested in four A. ramosum populations collected in Central and Eastern Europe. The average number of alleles per loci ranged from two to 17, and levels of observed and expected heterozygosity ranged from 0.000 to 1.000 and from 0.100 to 0.900, respectively. Primers were successfully amplified in the closely related species A. liliago (12 loci) and Chlorophytum comosum (six loci), whereas they mostly failed to amplify in the phylogenetically more‐distant species Muscari comosum (three loci) and M. tenuiflorum (no amplification). Conclusions This newly developed set of polymorphic nuclear microsatellite markers will be useful for population genetic investigation of A. ramosum and closely related species.

Questions: What is the relative importance of landscape variables compared to habitat quality variables in determining species composition in floodplain forests across different physiographic areas? How do species composition and species traits relate to effects of particular landscape variables? Do lowland and mountain areas differ in effects of landscape variables on species composition? Location: Southern Czech Republic. Methods: A total of 240 vegetation relevés of floodplain forests with measured site conditions were recorded across six physiographic areas. I tested how physiographic area, habitat quality variables and landscape variables such as current land-cover categories, forest continuity, forest size and urbanization influenced plant species composition. I also compared how mountain and lowland areas differ in terms of the relative importance of these variables. To determine how landscape configuration affects the distribution of species traits, relationships of traits and species affinity with landscape variables were tested. Results: Among landscape variables, forest continuity, landscape forest cover and distance to nearest settlement altered the vegetation. These variables also influenced the distributions of species traits, i.e. life forms, life strategies, affinity to forest, dispersal modes, seed characteristics, flooding tolerance and Ellenberg indicator values for nitrogen, light, moisture and soil reaction. Nevertheless, physiographic area and habitat quality variables explained more variation in species composition. Landscape variables were more important in lowland areas. Forest continuity affected species composition only in lowlands. Conclusions: Although habitat quality and physiographic area explained more vegetation variability, landscape configuration was also a key factor influencing species composition and distribution of species traits. However, the results are dependent on forest geographical location, with lowland forests being more influenced by landscape variables compared to mountain forests.