The relative importance of metacommunity processes in structuring pond communities: A multi-group approach

Background/Question/Methods The role of metacommunity processes in shaping local communities has been of core interest lately. Up to now, only a limited number of studies on metacommunities have included multiple groups of organisms, but these either cover different study areas, and are therefore impeded by differences among spatial scale or habitat type, or are based on a restricted number of sample locations. In this study we assessed the relative importance of both local environmental (physico-chemical and morphometric variables) and regional processes (spatial factors) for a wide range of functional groups originating from the same ecosystem. We studied in total 100 farmland ponds distributed over the entire territory of Belgium (surface area: 30.500 km²) and sampled 12 different groups of organisms (from bacteria to fish). The relative importance of spatial versus environmental factors in explaining community structure was studied using variation partitioning techniques. Spatial predictors were calculated using principal coordinates of neighbour matrices (PCNM) and a forward selection procedure was used to obtain the most parsimonious subset of environmental and spatial variables.

Results/Conclusions The community composition of the different functional groups, except bacteria, was significantly explained both by spatial and environmental factors, independently of each other. Overall, the relative importance of the independent spatial component was linked with the dispersal capacity and body size of the organisms. Passive dispersers, like phytoplankton, benthic diatoms, zooplankton and aquatic vegetation, were better predicted by local environmental factors than by spatial ones. Conversely, large and less motile vertebrate organisms, like amphibians and fish, revealed a strong association with spatial factors. Most macroinvertebrates (e.g. coleopteran, chironomids, molluscs and heteropterans) showed an intermediate response, which was in general better described by the spatial component. Bacterial communities did not show any association with spatial factors and were only significantly explained by environmental variables, indicating efficient species sorting along the environmental gradients. Within this studied landscape and habitat type, most organisms, except bacterial communities, were affected by dispersal limitation. The relative importance of spatial and environmental factors in explaining the community structure furthermore largely depended on dispersal ability and body size of the organisms.