Biogeography of thermophilic cyanobacteria: insights from the Zerka Ma'in hot springs (Jordan).

The thermal springs of Zerka Ma'in, with waters emerging at temperatures up to 63 degrees C, have been of interest to biologists already from the beginning of the 19th century. These waters, springing out from below ground and flowing into the hypersaline Dead Sea, form an isolated environment from a biogeographic point of view. We have investigated the molecular diversity of the cyanobacteria in the springs. The diversity discovered was large, defining operational taxonomic units (OTUs) by a cutoff of 97% similarity; 10 major OTUs were found, including an as yet unidentified cluster of cyanobacteria. The various patterns of similarities of our sequences to others obtained from different thermal environments worldwide led us to rethink the common theories in biogeography. Based on the data obtained, we suggest that there is no constant geographical separation of microorganisms; however, local speciation does occur at a rate dictated mainly by local community dynamics and the rate of entrance of new organisms into the ecosystem.