Microbial Ecology

, Volume 78, Issue 1, pp 33–41 | Cite as

Ecological Divergence with Gene Flow in a Thermophilic Cyanobacterium

  • Scott R. MillerEmail author
  • Darla Carvey
Environmental Microbiology


How ecological diversity is maintained and distributed within populations is a longstanding question in microbial ecology. In the thermophilic cyanobacterium Synechococcus B′, high observed levels of recombination are predicted to maintain ecological variation despite the simultaneous action of diverse selective pressures on different regions of the genome. To investigate ecological diversity in these bacteria, we directly isolated laboratory strains of Synechococcus B′ from samples collected along the thermal gradients of two geothermal environments in Yellowstone National Park. Extensive recombination was evident for a multi-locus sequence data set, and, consequently, our sample did not exhibit the sequence clustering expected for distinct ecotypes evolving by periodic clonal selection. Evidence for local selective sweeps at specific loci suggests that sweeps may be common but that recombination is effective for maintaining diversity of unlinked genomic regions. Thermal performance for strain growth was positively associated with the temperature of the environment, indicating that Synechococcus B′ populations consist of locally adapted ecological specialists that occupy specific thermal niches. Because this ecological differentiation is observed despite the absence of dispersal barriers among sites, we conclude that these bacteria may freely exchange much of the genome but that barriers to gene flow exist for loci under direct temperature selection.


Diversity Recombination Adaptation Selective sweep Thermophile 



Field work was conducted under National Park Service research permit YELL-5482. We thank two anonymous reviewers for comments on an earlier version of the manuscript.

Funding Information

This work was supported by National Science Foundation award EF-0801999 to SRM.

Supplementary material

248_2018_1267_MOESM1_ESM.pdf (252 kb)
Supplementary Fig. 1 (PDF 251 kb)
248_2018_1267_MOESM2_ESM.docx (73 kb)
Supplementary Table 1 (DOCX 72 kb)


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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Division of Biological SciencesThe University of MontanaMissoulaUSA

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