Ethan White and Allen Hurlbert (University of North Carolina) just had a paper on The Combined Influence of the Local Environment and Regional Enrichment on Bird Species Richness published online at American Naturalist. The research shows that combining local environmental influences with measures of the regional species pool provides improved prediction of local species richness over either set of predictors alone. An analysis of these patterns at different temporal scales suggests that this results from communities being composed two groups of species (source and sink) whose richness are regulated by different processes.
Thanks to American Naturalist's policy of making E-articles open access, anyone can freely access this paper via the link above.