Unparallel diversification in bacterial microcosms

Jabus Tyerman, Naomi Havard, Gerda Saxer, Michael Travisano, Michael Doebeli

Research output: Contribution to journalArticlepeer-review

31 Scopus citations


Adaptive speciation has gained popularity as a fundamental process underlying the generation of diversity. We tested whether populations respond to similar forms of disruptive selection by diversifying in similar or parallel ways by investigating diversified populations of Escherichia coli B evolved in glucose and glucose-acetate environments. In both environments, the populations have differentiated into two phenotypes, named for their characteristic colony morphologies: large (L) and small (S). Each type is heritable and this polymorphism (or 'diversified pair') appears to be maintained by negative frequency dependence. The L and S phenotypes from different environments are convergent in their colony morphology and growth characteristics. We tested whether diversification was parallel by conducting competition experiments between L and S types from different environments. Our results indicate that replicate diversified pairs from different environments have not diversified in parallel ways and suggest that subtle differences in evolutionary environment can crucially affect the outcome of adaptive diversification.

Original languageEnglish (US)
Pages (from-to)1393-1398
Number of pages6
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1570
StatePublished - Jul 7 2005


  • Adaptive diversification
  • Convergent evolution
  • Disruptive selection
  • Escherichia coli
  • Frequency-dependent selection
  • Parallel evolution


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