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Geographical isolation in hot spring cyanobacteria

Authors

  • R. Thane Papke,

    Corresponding author
    1. Department of Microbiology, 109 Lewis Hall, Montana State University, Bozeman, MT 59717, USA.
      E-mail rpapke@dal.ca; Tel. (+1) 902 494 2968; Fax (+1) 902 494 1355.
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    • Present address: Department of Biochemistry and Molecular Biology, Dalhousie University, Sir Charles Tupper Building, Room 8C, 5859 University Ave., Halifax, NS, B3H 4H7, Canada.

  • Niels B. Ramsing,

    1. Department of Microbial Ecology, Institute of Biological Sciences, University of Aarhus, Ny Munkegade, Building 540DK-8000, Aarhus C, Denmark.
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  • Mary M. Bateson,

    1. Department of Land Resources and Environmental Sciences, Leon Johnson Hall, Montana State University, PO Box 173120, Bozeman, MT 59717, USA.
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  • David M. Ward

    1. Department of Land Resources and Environmental Sciences, Leon Johnson Hall, Montana State University, PO Box 173120, Bozeman, MT 59717, USA.
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E-mail rpapke@dal.ca; Tel. (+1) 902 494 2968; Fax (+1) 902 494 1355.

Summary

It has been proposed that free-living microorganisms exhibit ubiquitous dispersal, do not form geographically isolated populations and rarely (if ever) speciate via allopatry. We studied island-like hot spring cyanobacterial communities in which geographical isolation should be prominent and detectable if it influences the evolution of bacteria. The genetic diversity of cyanobacteria indigenous to North American, Japanese, New Zealand and Italian springs was surveyed by (i) amplification and cloning of 16S rRNA and 16S−23S internal transcribed spacer regions; (ii) lineage-specific oligonucleotide probing (used to verify the predominance of cloned sequences); and (iii) lineage-specific polymerase chain reaction (PCR) (used to search for possible rare genotypes). Phylogenetic and distribution patterns were found to be consistent with the occurrence of geographical isolation at both global and local spatial scales, although different cyanobacterial lineages were found to vary in their distribution. A lack of correspondence between biological patterning and the chemical character of springs sampled suggested that the geographical distribution of thermophilic cyanobacteria cannot be explained by the 20 potential niche-determining chemical parameters that we assayed. Thus, geographical isolation (i.e. genetic drift) must in part be responsible for driving the observed evolutionary divergences. Geographical isolation may be an important underestimated aspect of microbial evolution.

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