Functional complementarity between dominant and subordinate species drives community assembly and dynamic

1. Natural communities are dominated by a small number of species interacting with many low abundance and subordinate species. Understanding how dominant species interact and coexist with the many subordinate species is fundamental to anticipating biodiversity responses to ongoing global change. To address these modern challenges, assessing the contribution of dominant and subordinate species to community-level trait abundance distributions (TADs) can help to better understand how communities assemble in space and time.2. Here, we investigated the contribution of dominant and subordinate species to community-level trait distributions in semi-natural ecosystems. We studied trait abundance distributions in two complementary designs on Massif-central grasslands community: (i) time-series data from a long-term land use experiments and, (ii) observational data from extensively and intensively managed grasslands.3. Our results showed that subordinates and dominant species assemble in a complementary way, explaining the emergence of highly even and stable functional assemblages.4. We found common saptio-temporal patterns based on management intensity, which suggest that the complementarity between dominant and subordinate species is a common rule governing the dynamic and assemblage of semi-natural ecosystems. Overall, our study highlights the potential existence of general assembly rules that influence the way species interact and coexist.