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Human-assisted introduction of alien plants is causing ecosystem transformations worldwide and is considered an important threat to biodiversity. We provide a European assessment of habitat levels of invasion in heathlands and scrub and identify successful alien plants and invasion trends across biogeographical regions. We analysed a geographically stratified data set of 24,220 dwarf shrub and scrub vegetation plots sampled across Europe. Among the 6547 vascular plant taxa occurring in these plots, we identified 311 neophytes (4.8%, i.e. alien species introduced in Europe or its sub-regions after 1500 AD) and compared five metrics of the level of invasion in (i) EUNIS habitats, (ii) broad habitat groups and (iii) biogeographical regions of Europe. We related habitat-specific levels of invasion to elevation and climatic variables using generalized linear models. Among neophytes, phanerophytes of non-European origin prevailed. The most frequent neophytes in the plots were Prunus serotina, Robinia pseudoacacia and Quercus rubra among phanerophytes, Impatiens parviflora among therophytes, and Erigeron canadensis and Solidago gigantea among hemicryptophytes. Levels of invasion significantly differed among habitats and biogeographical regions. The most invaded habitat was Macaronesian lowland scrub, followed by riparian scrub, Rubus scrub and forest-clearing scrub of temperate Europe, and coastal dune scrub of the Atlantic region. The levels of invasion were low in the shrublands of the Arctic and Mediterranean regions and decreased with elevation within habitats. Results suggest that insularity, low elevation, frequent disturbances, and high availability or considerable fluctuation of resources promote neophyte invasions in European shrublands.

The Pladias (Plant Diversity Analysis and Synthesis) Database of the Czech Flora and Vegetation was developed by the Pladias project team in 2014-2018 and has been continuously updated since then. The flora section of the database contains critically revised information on the Czech vascular flora, including 13.6 million plant occurrence records, which are dynamically displayed in maps, and data on 120 plant characteristics (traits, environmental associations and other information), divided into the sections: (1) Habitus and growth type, (2) Leaf, (3) Flower, (4) Fruit, seed and dispersal, (5) Belowground organs and clonality, (6) Trophic mode, (7) Karyology, (8) Taxon origin, (9) Ecological indicator values, (10) Habitat and sociology, (11) Distribution and frequency, and (12) Threats and protection. The vegetation section of the database contains information on Czech vegetation types extracted from the monograph Vegetation of the Czech Republic. The data are supplemented by national botanical bibliographies, electronic versions of the standard national flora and vegetation monographs, a database of more than 19,000 pictures of plant taxa and vegetation types, and digitalmaps (shapefiles) with botanical information. The data from the database are available online on a public portal www.pladias.cz, which also provides download options for various datasets and online identification keys to the species and vegetation types of the Czech Republic. In this paper, we describe the general scope, structure and content of the database, and details of the data on plant characteristics. To illustrate the data and describe the main geographic patterns in selected plant characteristics, we provide maps of mean values of numerical characteristics or proportions of categories for categorical characteristics on the map of the country in a grid of 5 longitudinal × 3 latitudinal minutes (approximately 6.0 km × 5.5 km). We also summarize the main variation patterns in the functional traits in the Czech flora using the principal component analysis.

1. Niche filtering predicts that abundant species in communities have similar traits that are suitable for the environment. However, niche filtering can operate on distinct axes of trait variation in response to different ecological conditions. Here, we use a trait-based approach to infer niche filtering processes and (a) test if abundant and rare species in grassland communities are differently positioned along distinct axes of trait variation, (b) determine if these trait variation axes, as well as phylogenetic and functional similarities, drive species relative abundance (above-ground cover) within communities, and (c) explore whether these relationships vary across grassland types and macro-climatic gradients. 2. We analysed species abundance in vegetation plots from temperate grasslands in Central Europe as a function of species position along three axes of trait variation: the ‘Plant Size Spectrum’ (PSS), the ‘Leaf Economics Spectrum’ (LES) and the ‘Life span/Clonality Spectrum’ (LCS). We also used phylogenetic and functional similarities in the multi-dimensional trait space as predictors of species abundance. We compared our results among alpine, wet, mesic and dry grasslands and tested whether the effect of the predictors on species abundance was significant across macro-climatic gradients. 3. Compared to abundant species, rare species in grassland communities were more commonly annual and non-clonal, had lower stature and smaller leaves and seeds, and relied on more acquisitive leaf economics. Our predictors significantly explained species abundance in approximately one-third of the plots. LES was the most important predictor across all plots, with the most prominent effect in alpine and dry grasslands and areas with more extreme temperatures. In contrast, in mesic and wet grasslands and grasslands located in warmer and less seasonal regions, species abundance was best predicted by phylogenetic similarities between species, with Poaceae species becoming more abundant. 4. Our study explored trait–abundance relationships for different community types across a large area and broad macro-climatic gradients. We conclude that niche filtering, and particularly resource-acquisition trade-offs, drives species abundance in temperate grassland communities of Central Europe. Our findings emphasize the interaction between local environmental conditions and plant function in determining community assembly.

Aim The first comprehensive checklist of European phytosociological alliances, orders and classes (EuroVegChecklist) was published by Mucina et al. (2016, Applied Vegetation Science, 19 (Suppl. 1), 3-264). However, this checklist did not contain detailed information on the distribution of individual vegetation types. Here we provide the first maps of all alliances in Europe. Location Europe, Greenland, Canary Islands, Madeira, Azores, Cyprus and the Caucasus countries. Methods We collected data on the occurrence of phytosociological alliances in European countries and regions from literature and vegetation-plot databases. We interpreted and complemented these data using the expert knowledge of an international team of vegetation scientists and matched all the previously reported alliance names and concepts with those of the EuroVegChecklist. We then mapped the occurrence of the EuroVegChecklist alliances in 82 territorial units corresponding to countries, large islands, archipelagos and peninsulas. We subdivided the mainland parts of large or biogeographically heterogeneous countries based on the European biogeographical regions. Specialized alliances of coastal habitats were mapped only for the coastal section of each territorial unit. Results Distribution maps were prepared for 1,105 alliances of vascular-plant dominated vegetation reported in the EuroVegChecklist. For each territorial unit, three levels of occurrence probability were plotted on the maps: (a) verified occurrence; (b) uncertain occurrence; and (c) absence. The maps of individual alliances were complemented by summary maps of the number of alliances and the alliance-area relationship. Distribution data are also provided in a spreadsheet. Conclusions The new map series represents the first attempt to characterize the distribution of all vegetation types at the alliance level across Europe. There are still many knowledge gaps, partly due to a lack of data for some regions and partly due to uncertainties in the definition of some alliances. The maps presented here provide a basis for future research aimed at filling these gaps. This project was funded by the Czech Science Foundation (grant no. 19-28491X). LM was supported by Iluka Chair of Vegetation Science & Biogeography, Murdoch University, Perth; IB, JAC and JL by the Basque Government (IT936-16); TMH by the European Social Fund (POCH and NORTE 2020) and National Funds (MCTES) through Fundacao para a Ciencia e a Tecnologia postdoctoral fellowship (SFRH/BPD/115057/2016) and project UIDB/04033/2020; AC and FK by the Slovenian Research Agency (P1-0236 to AC and program for Young Researchers to FK); SR by the University of Latvia (AAp2016/B041/Zd2016/AZ03); and KS by the Institute of Botany of the Czech Academy of Sciences (RVO 67985939).

Aims: Biodiversity is traditionally studied mostly at the species level, but biogeographical and macroecological studies at higher taxonomic levels can provide valuable insights into the evolutionary processes at large spatial scales. Our aim was to assess the representation of vascular plant families within different vegetation formations across Europe. Location: Europe. Methods: We used a data set of 816,005 vegetation plots from the European Vegetation Archive (EVA). For each plot, we calculated the relative species richness of each plant family as the number of species belonging to that family divided by the total number of species. We mapped the relative species richness, averaged across all plots in 50 km × 50 km grid cells, for each family and broad habitat groups: forests, grasslands, scrub and wetlands. We also calculated the absolute species richness and the Shannon diversity index for each family. Results: We produced 522 maps of mean relative species richness for a total of 152 vascular plant families occurring in forests, grasslands, scrub and wetlands. We found distinct spatial patterns for many combinations of families and habitat groups. The resulting series of 522 maps is freely available, both as images and GIS layers. Conclusions: The distinct spatial patterns revealed in the maps suggest that the relative species richness of plant families at the community level reflects the evolutionary history of individual families. We believe that the maps and associated data can inspire further biogeographical and macroecological studies and strengthen the ongoing integration of phylogenetic, functional and taxonomic diversity concepts., MV, IA, JPC, ZL, IK, AJ and MC were funded by the Czech Science Foundation, programme EXPRO (project no. 19-28491X); JDi by the Czech Science Foundation (18-02773S); IB and JAC by the Basque Government (IT936-16); AČ by the Slovenian Research Agency (ARRS, P1-0236); AK by the National Research Foundation of Ukraine (project no. 2020.01/0140); JŠ by the Slovak Research and Development Agency (APVV 16-0431); KV by the National Science Fund (Contract DCOST 01/7/19.10.2018).

Questions: The human-related spread of alien plants has serious environmental and socioeconomic impacts. Therefore, it is important to know which habitats are most threatened by invasion and why. We studied a wide range of European grasslands to assess: (a) which alien species are the most successful invaders in grasslands; (b) how invasion levels differ across European regions (countries or their parts) and biogeographical regions; and (c) which habitat types are the most invaded. Location: Europe. Methods: We selected 97,411 grassland vegetation plots from the European Vegetation Archive (EVA) and assigned a native or alien status to each of the 8,212 vascular plant species found in these plots. We considered only neophytes (alien species introduced after 1500 AD), which we further divided according to their origin. We compared the levels of invasion using relative neophyte richness in the species pool, relative neophyte richness and cover per plot, and percentages of invaded plots among regions and habitats. Results: Only 536 species, representing 6.5% of all grassland vascular plant species, were classified as neophytes. These were mostly therophytes or hemicryptophytes with low habitat specificity. Most of them were present in very few plots, while only three species were recorded in more than 1% of all plots (Onobrychis viciifolia, Erigeron annuus and Erigeron canadensis). Although invasion levels were generally low, we found more invaded plots in the Boreal and Continental regions. When considering only non-European neophytes, the Pannonian region was the most invaded. Among different grassland habitats, sandy grasslands were most invaded, and alpine and oromediterranean grasslands least invaded. Conclusions: In general, natural and semi-natural European grasslands have relatively low levels of neophyte invasions compared with human-made habitats or alluvial forests, as well as with grasslands on other continents. The most typical neophytes invading European grasslands are species with broad ecological niches., IA, VK, JDa, MV, IK and MC were supported by the Czech Science Foundation (EXPRO grant no. 19-28491X), PP and JP by the Czech Science Foundation (EXPRO grant no. 19-28807X), JDa, PP and JP by the Czech Academy of Sciences (long-term research development project RVO 67985939), IB by the Basque Government (IT936-16), RGG by REMEDINAL network (S2018/EMT-4338), AL by Komarov Botanical Institute, RAS (AAAA-A19-119031290052-1) and AK by the National Research Foundation of Ukraine (grant no. 2020.01/0140). JCS considers this work a contribution to his VILLUM Investigator project “Biodiversity Dynamics in a Changing World” funded by VILLUM FONDEN (grant 16549).

[Questions] European woodlands harbor at least 386 alien plant species but the factors driving local invasions remain unknown. By using a large vegetation-plot database, we asked how local richness and abundance of alien species vary by regions, elevation, climate, soil properties, human disturbance, and habitat types., [Location] Western, central and southern Europe., [Methods] We linked consolidated data from the European Vegetation Archive (16,211 plots) to a habitat classification scheme, climate, soil properties and human disturbance variables. In addition, we used 250 km × 250 km regional grid cells to test whether local patterns differ among regions. We used generalized additive models (GAMs) and quantile GAMs to explore how relative alien species richness and the sum of alien species covers per plot relate to predictors. Random Forest analyses (RFs) were employed to assess the importance of individual predictors that were not multicollinear., [Results] Relative alien species richness and the sum of alien species covers varied across regions and habitat types, with effects being more pronounced at the maximum rather than average responses. Both response variables declined with increasing elevation and distance to the nearest road or railroad and increased with the amount of sealed soil. Maxima in fitted functions matched plots from regional invasion hotspots in northwestern and central Europe. RFs accounted for 39.6% and 20.9% of the total variation in relative alien species richness and the sum of alien species covers, respectively, with region and habitat being the most important variables., [Conclusions] The importance of maximum response quantiles and the prevalence of regional hotspots point to invasion debt in European woodlands. As alien plants expand further, their species richness and abundance in woodlands will be likely driven by the shared effects of the introduction and planting history, differences in the invaded habitat types, and dispersal corridors., VW initiated this study as a part of the InvasEVe project financed by the SoMoPro II program and considers it as part of her Discovery Grant from the Canadian Natural Science and Engineering Research Council. VW's research leading to these results has acquired a financial grant from the People Program (Marie Curie Action) of the Seventh Framework Program of the EU according to REA Grant Agreement No. 291782, and it was further co-financed by the South-Moravian Region. MV and MC were supported by the Czech Science Foundation (19-28491X). PP and JP were supported by the Czech Science Foundation (19-28807X) and the Czech Academy of Sciences (RVO 67985939). JCS considers this work a contribution to his VILLUM Investigator project “Biodiversity Dynamics in a Changing World” funded by VILLUM FONDEN (grant 16549). IB and JAC were funded by the Basque Government (IT936-16). FFG was funded by the Plan Propio of the UCLM (2020-GRIN-29214)

Biogeographical barriers formed by natural forces over billions of years have been substantially disrupted by human activity, particularly in recent centuries. In response to these anthropogenic changes, global homogenization of biota is observed at an ever‐increasing rate, causing environmental and economic losses as well as emerging health risks. Identifying factors underlying alien species richness is essential for prevention of future introductions and subsequent spread. In this study, we examined the effects of environmental and human‐related factors on distribution of alien animal species richness in the Czech Republic (Central Europe). We compiled a set of maps showing the level of invasion of six categories of alien animal species in each of 628 grid cells (ca. 12.0 × 11.1 km) covering the Czech Republic. Relationships between alien species richness and 12 variables characterizing climatic conditions, topography, land cover, and human population size were calculated using the generalized least squares method. Species richness of all alien species, of invertebrates, and of terrestrial species showed the strongest positive relationship with mean annual temperature, while the number of black and grey (proposed prominent invaders) and aquatic species was most closely related to the presence of large rivers. Alien vertebrates showed a strong negative relationship with annual precipitation. The highest alien animal species richness was found in and near large population centers and in agricultural landscapes in warm and dry lowlands. The gateways for alien aquatic species are rather large rivers over sport fishing and aquaculture import. Compiled maps create a powerful visual communication tool, useful in development of programs to prevent future introductions.

Aim The former continental‐scale studies modelled coarse‐grained plant species‐richness patterns (gamma diversity). Here we aim to refine this information for European forests by (a) modelling the number of vascular plant species that co‐occur in local communities (alpha diversity) within spatial units of 400 m2; and (b) assessing the factors likely determining the observed spatial patterns in alpha diversity. Location Europe roughly within 12°W–30°E and 35–60°N. Taxon Vascular plants. Methods The numbers of co‐occurring vascular plant species were counted in 73,134 georeferenced vegetation plots. Each plot was classified by an expert system into deciduous broadleaf, coniferous or sclerophyllous forest. Random Forest models were used to map and explain spatial patterns in alpha diversity for each forest type separately using 19 environmental, land‐use and historical variables. Results Our models explained from 51.0% to 70.9% of the variation in forest alpha diversity. The modelled alpha‐diversity pattern was dominated by a marked gradient from species‐poor north‐western to species‐rich south‐eastern Europe. The most prominent richness hotspots were identified in the Calcareous Alps and adjacent north‐western Dinarides, the Carpathian foothills in Romania and the Western Carpathians in Slovakia. Energy‐related factors, bedrock types and terrain ruggedness were identified as the main variables underlying the observed richness patterns. Alpha diversity increases especially with temperature seasonality in deciduous broadleaf forests, on limestone bedrock in coniferous forests and in areas with low annual actual evapotranspiration in sclerophyllous forests. Main conclusions We provide the first predictive maps and analyses of environmental factors driving the alpha diversity of vascular plants across European forests. Such information is important for the general understanding of European biodiversity. This study also demonstrates a high potential of vegetation‐plot databases as sources for robust estimation of the number of vascular plant species that co‐occur at fine spatial grains across large areas., M.V., J.D., I.K., M.Ř. and M.C. were supported by the Czech Science Foundation (Centre of Excellence Pladias; project no. 14–36079G). I.B. and J.A.C. were supported by the Basque Government (IT936‐16). B.J.‐A. was supported by the Marie Curie Clarín‐COFUND program of the Principate of Asturias and the European Union (ACB17‐26). J.‐C.S. considers this work a contribution to his VILLUM Investigator project “Biodiversity Dynamics in a Changing World” funded by VILLUM FONDEN (grant 16549) and his Danish Council for Independent Research | Natural Sciences TREECHANGE project (grant 6108‐00078B).