Biogeographic patterns of aerobic anoxygenic phototrophic bacteria reveal an ecological consistency of phylogenetic clades in different oceanic biomes

In marine environments, aerobic anoxygenic phototrophic (AAP) bacterial assemblages vary in space and along environmental gradients but the factors shaping their diversity and distribution at different taxonomic levels remain poorly identified. Using sets of sequences encoding the M sub-unit of the photosynthetic apparatus from different oceanic regions, we prioritized the processes underlying AAP bacterial biogeographical patterns. The present analysis offers novel insights into the ecological distribution of marine AAP bacteria and highlights that physiological constraints play a key role in structuring AAP bacterial assemblages at a global scale. Salinity especially seems to favor lineage-specific adaptations. Moreover, by inferring the evolutionary history of habitat transitions, a substantial congruence between habitat and evolutionary relatedness was highlighted. The identification of ecological cohesive clades for AAP bacteria suggests that prediction of AAP bacterial assemblages is possible from marine habitat properties.