Resident-disperser differences and genetic variability affect communities in 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 Tetrahymena thermophila, 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 Tetrahymena species, and (ii) whether these effects are genotype-dependent. We found that dispersers led to lower community biomass compared to residents. This effect was highly consistent across the twenty T. thermophila 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.