Metacommunity theory predicts that habitat size, connectivity, dispersal, biotic interactions (competition, trophic interactions), and abiotic environmental conditions jointly determine species occurrence and local community composition and diversity. We employ a trait-based approach in a natural metacommunity system, and integrate spatial heterogeneity, traits related to dispersal in space and time, biotic interactions and environmental filtering to understand plant community assembly and ecosystem functioning. Using a large-scale naturally fragmented grassland system in the archipelago of Southern Finland as a model system, we examine:

1. What is the influence of habitat heterogeneity (connectivity, size), species’ traits related to dispersal and competition, and environmental filtering on species occurrences, community composition and diversity?
2.  How are species’ dispersal abilities, both spatial and temporal, related to their distributions and diversity in a spatially heterogeneous system?                                                                                           
3. How dispersal distance, dispersal-related traits and competition-related traits affect community responses to global changes?