An experimental test of environmental filtering in zooplankton pond communities

Understanding the assembly of communities in separate patches with restricted connectivity is a central goal in spatial community ecology. In such meta-communities, several processes structure the local communities. Besides dispersal/drift and local processes, environmental filtering is often regarded as one important driver which refers to specific environmental characteristics of different patches that restrict the colonization and/or persistence of individual species. An aquatic example of a meta-community is a set of ponds scattered in the landscape. Many aquatic organisms disperse passively among ponds. As dispersal rates increase in a metacommunity, local environmental conditions primarily shape the zooplankton community structure. Local dynamics prevail and species generally exist in habitats where they are highly adapted to and in a few places where they are sub-optimally adapted (species sorting). Under high dispersal rates, spatial dynamics are more important to local densities than temporal, within-lake dynamics by frequently providing individual patches with immigrants (mass effects). We examine the influence of environmental filtering on the zooplankton community structure in a group of ponds within an agricultural landscape. We used an experimental approach to directly quantify environmental filtering and the potential local adaptation of individual species. We sampled four ponds in an agricultural matrix and measured the performance of the zooplankton community in their home and away environment. Common garden experiments revealed that the zooplankton communities developed differently in their home and away environment and there might have been some degree of local adaptation as some species were better adapted/had a higher fitness to their home habitat than away. However, the opposite case, lower abundance at home than away, was also found for some species. Thus, we found environmental filtering on the community level, but no consistent sign for local adaptation.