Are ground beetles neutral?

The neutral model approach to community ecology is currently intensively discussed but has mainly been tested for its ability to mimic observed patterns like species-abundance or abundance-occupancy distributions. Less well studied is the question whether neutral models are able to explain these distributions and other ecological patterns like species co-occurrences simultaneously. Here we use a random draw and a spatially explicit neutral model to test whether both models are able to predict patterns of island colonisation by ground beetles. We show that island colonisation is not a simple random draw from the mainland metacommunity. The neutral model was able to mimic basic patterns of species diversity, island occupancy, and island abundances. Both models, however, were unable to produce observed non-random patterns of species co-occurrences and nestedness while predicting random distributions of species across islands. The neutral model produced patterns of nestedness and abundance-occupancy relationships that were intermediate between the observed patterns and the predictions from a simple random draw. Our results add further to the view that a neutral model might be the appropriate null model for the study of ecological communities. Its ability to mimic basic patterns of biodiversity helps to sharpen our perception of niche differences and competitive effects that might cause deviations from the model. It seems better suited to distinguish between random effects and species interactions than simple random draw models. (c) 2006 Gesellschaft fur Okologie. Published by Elsevier GmbH. All rights reserved.