Summary1. An international group of scientists has built an open internet data base of life-history traits of the Northwest European flora (the LEDA-Traitbase) that can be used as a data source for fundamental research on plant biodiversity and coexistence, macro-ecological patterns and plant functional responses. 2. The species-trait matrix comprises referenced information under the control of an editorial board, for ca. 3000 species of the Northwest European flora, combining existing information and additional measurements. The data base currently contains data on 26 plant traits that describe three key features of plant dynamics: persistence, regeneration and dispersal. The LEDA-Traitbase is freely available at www.leda-traitbase.org. 3. We present the structure of the data base and an overview of the trait information available. 4. Synthesis. The LEDA Traitbase is useful for large-scale analyses of functional responses of communities to environmental change, effects of community trait composition on ecosystem properties and patterns of rarity and invasiveness, as well as linkages between traits as expressions of fundamental trade-offs in plants.

We developed PAPPUS, a trajectory model for wind dispersal of plant diaspores under field conditions. The model considers the effects of topography, turbulence (including thermal updrafts), and different weather conditions on the dispersibility of diaspores by wind. In the model, the plant species are characterized by the initial release height and the falling velocity of their diaspores. The common problems in modeling turbulence, which limit the applicability of existing models in predicting long‐distance dispersal, are avoided by measuring the high‐frequency fluctuations of the wind vector and using these data to simulate the course of the wind vector in the model. Using PAPPUS, we simulated dispersal distance spectra and compared them with those observed during field experiments executed in open habitats. Within a broad range of landscapes and under different weather conditions, the results of the model represent the observed spectra reasonably well. Additionally, we compared the observed dispersal distance spectra with the predictions of an existing plume and trajectory model, respectively. PAPPUS was the only model capable of predicting the proportion of diaspores dispersed over long distances; the existing models were unable to predict that proportion. This is particularly true for sunny weather conditions with thermal turbulence and updrafts, because these conditions may result in a high proportion of long‐distance dispersal, even if the horizontal wind speed is low. In contrast, windy or stormy weather may be of much smaller importance for long‐distance dispersal than is commonly assumed, especially for non‐tree species with Vterm < 1.5 m/s. Horizontal wind speed was not correlated with the proportion of diaspores dispersing >100 m, whereas the frequency of updrafts was. Furthermore, the effects of landscape topography on dispersal distances were examined in simulations using PAPPUS. Differences in elevation and slope may affect the dispersal distance spectra considerably. The superior performance of PAPPUS in predicting long‐distance dispersal is mainly due to the new method of incorporating turbulence (especially thermal updrafts) and the consideration of topographic effects. Because other wind dispersal models applied to diaspore dispersal thus far do not consider thermal updrafts or topography, they may considerably underestimate the dispersibility of plant diaspores by wind. Corresponding Editor: M. L. Cain.

The influence of dispersal limitation on species ranges remains controversial. Considering the dramatic impacts of the last glaciation in Europe, species might not have tracked climate changes through time and, as a consequence, their present-day ranges might be in disequilibrium with current climate. For 1016 European plant species, we assessed the relative importance of current climate and limited postglacial migration in determining species ranges using regression modelling and explanatory variables representing climate, and a novel species-specific hind-casting-based measure of accessibility to postglacial colonization. Climate was important for all species, while postglacial colonization also constrained the ranges of more than 50 per cent of the species. On average, climate explained five times more variation in species ranges than accessibility, but accessibility was the strongest determinant for one-sixth of the species. Accessibility was particularly important for species with limited long-distance dispersal ability, with southern glacial ranges, seed plants compared with ferns, and small-range species in southern Europe. In addition, accessibility explained one-third of the variation in species' disequilibrium with climate as measured by the realized/potential range size ratio computed with niche modelling. In conclusion, we show that although climate is the dominant broad-scale determinant of European plant species ranges, constrained dispersal plays an important supplementary role.

Conventional plant dispersal classification systems use simple binary assignment schemes classifying each species as either being dispersed by means of a certain dispersal vector or not. However, because the dispersal potential ranges continually, this dichotomy appears to be rather artificial, and the existing systems may not be very useful for addressing ecological questions. To quantify gradual differences in the dispersal potential, we developed a system assessing wind dispersal potentials. Wind dispersal potential is defined as the proportion of diaspores exceeding a predefined reference distance under certain weather conditions, to acknowledge that wind dispersal potential is scale and context specific. The system is based on an independently validated simulation model of wind dispersal that was used to compute the proportion of diaspores exceeding predefined reference distances. On an ordinal scale, the proposed system allows one to assess the wind dispersal potential of any plant species with known falling velocity and release height of its diaspores without further computing. The system mainly relies on two traits characterizing the plant species (falling velocity and initial release height of the diaspores) and two context‐specific parameters (reference distance and weather conditions). We examined how wind dispersal potential is sensitive to these factors and found that it was most sensitive to weather conditions and falling velocity. The species‐specific traits interact with reference distance: the greater the reference distance and the lower the release height in relation, the more relevant a low falling velocity becomes for achieving a high wind dispersal potential. We subsequently applied the system to 335 plant species and found a considerable variation in their wind dispersal potentials. Many species commonly assumed to be wind dispersed exhibit only a low wind dispersal potential. Comparing the wind dispersal potentials to the morphology of the diaspores also reveals a considerable variation of the wind dispersal potential of species classified as the same morphological type. The results show that the conventional assignment of a plant species to a certain mode of dispersal, which is primarily based on the morphology of its diaspores, will often result in misleading conclusions regarding the dispersal potential of the respective species. Corresponding Editor: M. L. Cain.

Functional diversity within communities may influence ecosystem functioning, but which factors drive functional diversity? We hypothesize that communities assembled from many phylogenetic lineages show large functional diversity if assembly is random, but low functional diversity if assembly is controlled by interactions between species within lineages. We combined > 9000 descriptions of Dutch plant communities, a species-level phylogeny, and information on 16 functional traits (including eight dispersal traits). We found that all traits were conserved within lineages, but nevertheless communities assembled from many lineages showed a smaller variation in trait-states of most traits (including dispersal traits) than communities assembled from few lineages. Hence, within lineages, species are not randomly assembled into communities, contradicting Neutral Theory. In fact, we find evidence for evolutionary divergence in trait-states as well as present-day mutual exclusion among related, similar species, suggesting that functional diversity of communities increased due to past and present interactions between species within lineages.