title: Unparallel diversification in bacterial microcosms.
abstract: 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.
authors: Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia, Canada V6T 1Z4. tyerman@zoology.ubc.ca
authors: Jabus
authors: J
authors: Tyerman
authors: Naomi
authors: N
authors: Havard
authors: Gerda
authors: G
authors: Saxer
authors: Michael
authors: M
authors: Travisano
authors: Michael
authors: M
authors: Doebeli
mesh_terms: D000085:Acetates; D000222:Adaptation, Physiological; D005075:Biological Evolution; D015169:Colony Count, Microbial; D004777:Environment; D004926:Escherichia coli / Q000254:growth & development* / Q000378:metabolism; D005947:Glucose; D010641:Phenotype; D012641:Selection, Genetic
chemical_list: D000085:Acetates; D005947:Glucose