Summary1. Dispersal intensity is a key process for the persistence of prey-predator metacommunities. Consequently, knowledge of the ecological mechanisms of dispersal is fundamental to understanding the dynamics of these communities. Dispersal is often considered to occur at a constant per capita rate; however, some experiments demonstrated that dispersal may be a function of local species density. 2. Here we use aquatic experimental microcosms under controlled conditions to explore intra-and interspecific density-dependent dispersal in two protists, a prey Tetrahymena pyriformis and its predator Dileptus sp. 3. We observed intraspecific density-dependent dispersal for the prey and interspecific density-dependent dispersal for both the prey and the predator. Decreased prey density lead to an increase in predator dispersal, while prey dispersal increased with predator density. 4. Additional experiments suggest that the prey is able to detect its predator through chemical cues and to modify its dispersal behaviour accordingly. 5. Density-dependent dispersal suggests that regional processes depend on local community dynamics. We discuss the potential consequences of density-dependent dispersal on metacommunity dynamics and stability.

A soil transfer field experiment has been designed in order to study (i) whether and how Collembolan communities are affected by a sudden perturbation (a shift from agricultural land to heathland, and the reverse), and (ii) whether species do respond in the same direction and to the same extent according to their habitat preference (ascertained by controls). The study was conducted in the Parc Naturel Régional de la Brenne (Indre, France) in a private property where the land is shared between heathland and pasture. We showed that heathland differed from pasture in its species composition, which is not novel, but that both communities did not evolve in the same manner when transferred in another environment. The heathland community seemed more stable than the pasture community, although it was colonized by the surrounding fauna within two months, while the the pasture community seemed less stable when transferred to heathland.