Disturbance-mediated colonization-extinction dynamics in experimental protist metacommunities.

Colonization-extinction dynamics and species sorting among habitats deter- mine the distribution of species within metacommunities. Theory suggests that disturbances reduce the importance of species sorting and enhance spatial patterning and stochastic effects, however this has not yet been experimentally shown. We examined how extinctions in a heterogeneous landscape of patches affects the influence of environmental, spatial, and stochastic factors on community composition in a simple two-species, two-habitat, protist metacommunity where each species dominates in a different habitat type. We imposed four different levels of random extinctions on local patches and monitored changes in the metacommunity through time. We found that near-steady state patterns of community variability developed relatively rapidly (within nine colonization-extinction cycles) and that increased extinction rate produced altered patterns of community regulation by reducing environmental control and increasing spatial and stochastic effects. Our results indicate a possible explanation for the combination of environmental, spatial and stochastic effects observed in natural metacommunities.