Evol Ecol Res 12: 803-820 (2010)     Full PDF if your library subscribes.

Variation in the propensity to diversify in experimental populations of Escherichia coli: consequences for adaptive radiation

Jabus Tyerman¹ and Michael Doebeli^1,2

¹Department of Zoology, University of British Columbia, Vancouver, BC, Canada and ²Department of Mathematics, University of British Columbia, Vancouver, BC, Canada

Correspondence: J. Tyerman, Department of Zoology, University of British Columbia, 2370–6270 University Boulevard, Vancouver, BC V6T 1Z4, Canada.
e-mail: jabustyerman@gmail.com

ABSTRACT

Question: Does genotype regulate diversification during adaptive radiation?

Hypothesis: Experimental populations initiated from different genotypes vary in their propensity to undergo analogous adaptive radiations in the same environment.

Organisms: We used slow-switcher and fast-switcher genotypes (reflecting different specialized metabolic phenotypes) derived from the bacterium Escherichia coli B.

Methods: In a previous evolution experiment, we observed the generation of novel, specialist genotypes (slow- and fast-switchers) evolved under adaptive radiation. We isolated these genotypes and assessed their propensity to further evolve and diversify in the same evolutionary conditions that gave rise to them. Specifically, we wished to determine whether these genotypes could recapitulate the original diversity produced during the first bout of adaptive radiation. We assessed metabolic diversification using kinetic growth profiles.

Conclusions: Slow-switchers could recapitulate the original diversity, while fast-switchers never did. Thus, some genotypes appear constrained in their ability to generate mutations that would otherwise be selected during adaptive radiation. This demonstrates the importance of variational input as a regulator of diversification.

Keywords: adaptive radiation, character displacement, diversification, Escherichia coli, growth curve analysis, metabolism, mutational bias.

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