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Aim s : Ecological theories predict that assembly processes are driven by two deterministic forces: environmental filtering and limiting similarity. Their relative importance under different environmental conditions is still not completely obvious. Therefore, in this paper the predictions of the stress–dominance hypothesis (SDH) are tested in several sites. Location: Kiskunság in Hungary, and Deliblato Sands in Serbia, Central Europe. Methods: We studied a productivity gradient from open sand grasslands to meadows. The cover of species was estimated visually in plots with a size of 2 m × 2 m, resulting in 344 vegetation plots. Four trait values (height, seed mass, specific leaf area, and leaf size) were collected from field measurements and databases. The weighted median of interspecies distances in traits (a robust alternative to Rao's quadratic entropy) was used to determine functional diversity. The convergence and divergence of each trait in communities were evaluated by randomization tests, and effect sizes were calculated for each plot. We used hierarchical general additive models (HGAM) to determine whether the trend of effect sizes along the productivity gradient is the same in different sites. Results: The HGAM approach indicated that trait variations follow global trends but are influenced by site‐specific effects. The exception is seed mass, whose variation did not have any trend. Both environmental filtering and limiting similarity exist in the communities, and mainly a shift from trait convergence to a divergence pattern along the productivity gradient was observed. Conclusion: The results are mainly congruent with theoretical expectations, but the results from the different sites did not lead to the same conclusion. Although traits follow a global trend, the site effect is not negligible. Critical evaluation of SDH using trait convergence/divergence patterns for exploring rules of community assembly points out the weaknesses of this hypothesis. Therefore, alternative ways of studying trait patterns should be found to better understand community organization. [ABSTRACT FROM AUTHOR]

The giant plantain (Plantago maxima Juss. ex Jacq.) is a highly protected member of the Hungarian indigenous flora. The survival of this species is threatened by several factors and therefore elaboration of a conservation strategy and its implementation is extremely important. A thorough understanding of the germination properties of this plant is inevitable for its in situ conservation and also for the establishment of a long-term ex situ population. As we are not aware of any prior studies on the germination biology of the species, we investigated it in a laboratory experiment. In this study, we examined the effects of cold treatment, the role of light and the impact of seed size on seed germination. We have set up a Petri-dish experiment with 3 replicates at +20 °C room temperature. According to our results, giant plantain seeds do not require cold treatment to germinate: mean germination percentage was 54.7% for the cold treatment and 52% for the control. Light has an important role in the seed germination of the species, accordingly, seeds are positive photoblastic (40.0% germinated in the light, while 2.7% under dark conditions). Seed size did not have a significant effect on germination percentage, but we found differences among seed lots originating from different mother plants: for seeds smaller than 0.83 mm, germination percentages were 58.2%, 79.2% and 61.7%, while for seeds larger than 0.83 mm these were 48.9%, 87.5% and 33.3%. [ABSTRACT FROM AUTHOR]