Global phylogenetic community structure and β-diversity patterns in surface bacterioplankton metacommunities

Abstract

We aimed to identify phylogenetic community patterns in abundant planktonic bacteria (Alpha-, Beta-, and Gammaproteobacteria, Actinobac- teria, Cyanobacteria, and Bacteroidetes) from a world- wide range of surface waters (lakes and seas — 34 sites and ca. 4500 16S rRNA gene sequences). At each site we assessed the number of observed bacterial groups and the genetic relatedness of the most abun- dant groups through a community phylogenetic meta- analysis approach in order to (1) explore which poten- tial ecological processes were consistent with the observed phylogenetic patterns in community assem- bly and (2) disentangle the effects of space and envi- ronment in β-diversity patterns for the different bacte- rial groups. Inland waters had significantly more bacterial groups and were more diverse than marine waters. Marine habitats showed a higher percentage of clustered sites than lakes, and bacterial communi- ties were more closely related than expected by chance. Phylogenetic β-diversity analyses revealed different patterns to both salt composition (marine vs. inland salt lakes) and salt concentration for the domi- nant bacteria. We observed that while β-diversity pat- terns for Bacteroidetes were mostly shaped by salinity concentration, patterns in Alphaproteobacteria and Gammaproteobacteria were controlled by salt compo- sition. Actinobacteria, Betaproteobacteria and Sphin- gobacteria were largely absent from marine habitats and from saline continental sites. In general and despite the lack of contextual metadata, environmen- tal similarity was more relevant than spatial distribu- tion for bacterial β-diversity patterns. However, we detected a geographic signal for some inland waters' groups (i.e. Actinobacteria, Beta-, and Gammapro- teobacteria). Overall, the analyses indicated differ- ences among phylogenetic groups and reflected pat- terns upon which further exploration of community assembly theory could be based.