title: Parallelism in adaptive radiations of experimental Escherichia coli populations.
abstract: Adaptive radiations are major contributors to species diversity. Although the underlying mechanisms of adaptive radiations, specialization and trade-offs, are relatively well understood, the tempo and repeatability of adaptive radiations remain elusive. Ecological specialization can occur through the expansion into novel niches or through partitioning of an existing niche. To test how the mode of resource specialization affects the tempo and repeatability of adaptive radiations, we selected replicate bacterial populations in environments that promoted the evolution of diversity either through niche expansion or through niche partitioning, and in a third low-quality single-resource environment, in which diversity was not expected to evolve. Colony size diversity evolved equally fast in environments that provided ecological opportunities regardless of the mode of resource specialization. In the low-quality environments, diversity did not consistently evolve. We observed the largest fitness improvement in the low-quality environment and the smallest the glucose-limited environment. We did not observe a change in the rate of evolutionary change in either trait or environment, suggesting that the pool of beneficial mutations was not exhausted. Overall, the mode of resource specialization did not affect the tempo or repeatability of adaptive radiations. These results demonstrate the limitations of eco-evolutionary feedbacks to affect evolutionary outcomes.
authors.affiliation: Department of Biology and Biochemistry, University of Houston, Houston, Texas, 77204. gerdasaxer@gmail.com.|Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada. gerdasaxer@gmail.com.|Department of BioSciences, MS 140, Rice University, 6100 Main Street, Houston, Texas, 77005. gerdasaxer@gmail.com.|Current Address: Industrial Biosciences, E.I. du Pont de Nemours and Company, Experimental Station, PO Box 8352, Wilmington, Delaware, 19803. gerdasaxer@gmail.com.
authors.forename: Gerda
authors.initials: G
authors.lastname: Saxer
authors.affiliation: Department of Biology and Biochemistry, University of Houston, Houston, Texas, 77204.|Department of Ecology, Evolution and Behavior, University of Minnesota, 100 Ecology, 1987 Upper Buford Circle, St. Paul, Minnesota, 55108.
authors.forename: Michael
authors.initials: M
authors.lastname: Travisano
mesh_terms: D000085:Acetates / Q000378:metabolism; D000220:Adaptation, Biological; D005075:Biological Evolution; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D056084:Genetic Fitness; D014644:Genetic Variation; D005947:Glucose / Q000378:metabolism
chemical_list: D000085:Acetates; D005947:Glucose
keywords: Divergence; diversification; eco-evolutionary feedbacks; niche expansion; niche partitioning; repeatability