Macroecological patterns of marine bacteria on a global scale

Aim To test whether within-species and among-species patterns of abundance and latitudinal range in marine bacteria resemble those found for macro-organisms, and whether these patterns differ along latitudinal clines. Location Global pelagic marine environments. Methods Taxon-specific sequence abundance and location were retrieved from the open-access V6-rRNA pyrotag sequence data base VAMPS (http://vamps.mbl.edu/), which holds a massive collection of marine bacterial community data sets from the International Census of Marine Microbes sampling effort of global ocean water masses. Data were randomly subsampled to correct for spatial bias and for differences in sampling effort. Results We show that bacterial latitudinal ranges are narrower than expected by chance. When present in both Northern and Southern hemispheres, taxa occupy restricted ranges at similar latitudes on both sides of the equator. A significant and positive relationship exists between sequence abundance and latitudinal range, although this pattern contains a large amount of variance. Abundant taxa in the tropics and in the Northern Hemisphere generally have smaller ranges than those in the Southern Hemisphere. We show that the mean latitudinal range of bacterial taxa increases with latitude, supporting the existence of a Rapoport effect in marine bacterioplankton. Finally, we show that bacterioplankton communities contain a higher proportion of abundant taxa as they approach the poles. Main conclusions Macroecological patterns such as the abundancerange relationship, in general, extend to marine bacteria. However, differences in the shape of these relationships between bacteria and macro-organisms call into question whether the processes and their relative importance in shaping global marine bacteria and macro-organism distributions are the same.