Spatial patterns in pond invertebrate communities: separating environmental and distance effects

Abstract

1. The nature and extent of spatial pattern in communities has important implications for their dynamics and conservation. Previous studies of pond ecosystems, over relatively small spatial scales, have found little evidence of spatial autocorrelation of community composition. Patterns in community composition over greater spatial distances have not been documented. 2. Here, data on macroinvertebrate communities and physico-chemical characteristics of 102 ponds over a 60 x 6.0km area of Oxfordshire, UK, were used to examine evidence for spatial autocorrelation in community composition and to separate the effects of environmental similarity and physical distance on community similarity. 3. Overall similarity between communities was low, but showed significant positive spatial autocorrelation. There was evidence for both environmental and physical distance effects on spatial autocorrelation of community similarity. Community similarity was negatively related to differences in environmental conditions, but effects were only significant for large environmental differences. 4. When environmental effects were accounted for, there was significant positive spatial autocorrelation of community composition over inter-site distances of up to 13 km. These results suggest that interactions between pond sites, potentially through dispersal, are evident over larger spatial scales than has previously been appreciated, and emphasize the need to consider spatial issues when developing strategies for pond conservation.