Higher species diversity explained by stronger spatial aggregation across six neotropical Drosophila communities

Spatial aggregation of competitors over resource patches is generally accep ted as an important mechanism maintaining coexistence of species in insect communities exploiting fragmented resources. However, its quantitative effe cts on local diversity, i.e. the relationship between the degree of aggrega tion in a community and community diversity, remain unexplored. In this pap er, we tested whether stronger spatial aggregation does lead to the predict ed higher local diversity. We compared six species rich Drosophila communit ies exploiting decaying fruits in central Panama, monitored over one full y ear (>25 generations). We found a clear positive relationship between the o verall degree of aggregation and community diversity. In addition, aggregat ion over fruit trees was found to contribute greatly to the overall degree of aggregation and was largely responsible for the observed relationship be tween aggregation and diversity across communities. In addition, both diver sity and aggregation strength were lower in communities in disturbed habita ts, which was explained by altered spatial distribution of fruiting trees. This study. shows that the aggregation model cannot only explain coexistenc e, but also differences in local diversity.