Cyanobacterial diversity in geographically related and distant host plantsof the genus Gunnera

The diversity among 45 cyanobacterial isolates from II different Gunnera sp ecies originating from different geographical areas was examined. By means of polymerase chain reaction (PCR) fingerprinting with short tandemly repea ted repetitive (STRR) sequences as primers, ten groups of symbiotic cyanoba cteria and five unique isolates not belonging to a particular group were id entified. Most groups were restricted to one geographical area, indicating a limited distribution of related cyanobacterial strains. An extensive cyan obacterial diversity was found both within and between the 11 different Gun nera species. Within a particular plant and even within the same stem gland , more than one cyanobacterial strain at a time could be present. These res ults indicate a low specificity in Gunnera-Nostoc symbiosis.