PDF of recent "Open Access" PNAS paper on bacterial biogeography. The paper (of which I am an author) made use of rRNA PCR to survey bacteria in salt marshes. The bacteria were surveyed broadly (using broadly targeted PCR primers) and narrowly (using primers that focused on specific taxonomic subgroups) across samples collected from a nested design that covered many different spatial scales. From the abstract: "Our data are consistent with the idea that dispersal limitation at local scales can contribute to β-diversity, even though the 16S rRNA genes of the relatively common taxa are globally distributed. These results highlight the importance of considering multiple spatial scales for understanding microbial biogeography."