A central hypothesis of ecology states that regional diversity influences local diversity through species-pool effects. Species pools are supposedly shaped by large-scale factors and then filtered into ecological communities, but understanding these processes requires the analysis of large datasets across several regions. Here, we use a framework of community assembly at a continental scale to test the relative influence of historical and environmental drivers, in combination with regional or local species pools, on community species richness and community completeness. Using 42,173 vegetation plots sampled across European beech forests, we found that large-scale factors largely accounted for species pool sizes. At the regional scale, main predictors reflected historical contingencies related to post-glacial dispersal routes, whereas at the local scale, the influence of environmental filters was predominant. Proximity to Quaternary refugia and high precipitation were the main factors supporting community species richness, especially among beech forest specialist plants. Models for community completeness indicate the influence of large-scale factors, further suggesting community saturation as a result of dispersal limitation or biotic interactions. Our results empirically demonstrate how historical factors complement environmental gradients to provide a better understanding of biodiversity patterns across multiple regions.

Alexandru Borza Botanical Garden Babeș Bolyai University Cluj Napoca Romania

cE3c Centre for Ecology Evolution and Environmental Changes Azorean Biodiversity Group Angra do Heroísmo Portugal

Center for Biodiversity Dynamics in a Changing World Aarhus University Aarhus Denmark

Department of Applied Ecology Faculty of Ecology and Environmental Sciences Technical University in Zvolen Zvolen Slovakia

Department of Botany and Biodiversity Research University of Vienna Vienna Austria

Department of Botany and Zoology Masaryk University Brno Czech Republic

Department of Botany School of Biology Aristotle University of Thessaloniki Thessaloniki Greece

Department of Environmental Biology Sapienza University of Rome Roma Italy

Department of Plant Biology and Ecology University of Basque Country UPV EHU Bilbao Spain

Department of Vegetation Ecology Botanical Garden University of Wroclaw Wrocław Poland

German Centre for Integrative Biodiversity Research Halle Jena Leipzig Leipzig Germany

Institute of Biology Geobotany and Botanical Garden Martin Luther University Halle Wittenberg Halle Germany

Institute of Forest Ecology Slovak Academy of Sciences Zvolen Slovakia

LERFoB INRA AgroParisTech Nancy France

Plant Science and Biodiversity Center Institute of Botany Slovak Academy of Sciences Bratislava Slovakia

Section for Ecoinformatics and Biodiversity Department of Bioscience Aarhus University Aarhus Denmark

VINCA Vienna Institute for Nature Conservation and Analyses Wien Austria

WSL Swiss Federal Research Institute Birmensdorf Switzerland

ZRC SAZU Institute of Biology Ljubljana Slovenia

References provided by Crossref.org

Evolutionary dynamics of Euphorbia carniolica suggest a complex Plio-Pleistocene history of understorey species of deciduous forest in southeastern Europe

Post-glacial range formation of temperate forest understorey herbs - Insights from a spatio-temporally explicit modelling approach

Global patterns of vascular plant alpha diversity