Dispersal syndromes affect ecosystem functioning in ciliate microcosms

Dispersal is a key process mediating ecological and evolutionary dynamics. Its effects on the dynamics of spatially-structured systems, population genetics or species range distribution can depend on phenotypic differences between dispersing and non-dispersing individuals. However, scaling up the importance of resident-disperser differences to communities and ecosystems has rarely been considered, in spite of intraspecific phenotypic variability being an important factor mediating community structure and productivity. Here, we used the ciliate <em>Tetrahymena thermophila</em>, in which phenotypic traits are known to differ between residents and dispersers, to test (i) whether these resident-disperser differences affect biomass and composition in competitive communities composed of four other <em>Tetrahymena</em> species, and (ii) whether these effects are genotype-dependent. We found that dispersers led to a lower community biomass compared to residents. This effect was highly consistent across the twenty <em>T. thermophila</em> genotypes used, despite intraspecific variability in resident-disperser phenotypic differences. We also found a significant genotypic effect on biomass production, showing that intraspecific variability has consequences for communities. Our study suggests that individual dispersal strategy can scale up to community productivity in a predictable way, opening new perspectives to the functioning of spatially structured ecosystems.