Separating the determinants of phylogenetic community structure.

The role of competition in forbidding similar species from co-occurring has long been debated. A difficulty in identifying this repulsion of similar species is that similar species share similar environmental requirements and hence show an attraction to communities where these requirements are met. To disentangle these opposing patterns, we use phylogenetic relatedness as an objective metric of species similarities. Studying 11 sunfishes (Centrarchidae) from 890 lakes, we first show no phylogenetic pattern in the raw community data. We then regressed sunfish presence/absence against seven environmental variables and show that lakes with similar water clarity and latitude likely contain closely related species. After statistically removing the environmental effects, phylogenetic repulsion was apparent, with closely related sunfishes less likely to co-occur. Thus, both phylogenetic attraction, driven by environmental filtering, and phylogenetic repulsion, possibly caused by competition, simultaneously occur and obscure one another in the overall phylogenetic structure of sunfish communities.