Divergent evolution during an experimental adaptive radiation. 2003

R Craig MacLean, and Graham Bell
Department of Biology, McGill University, 1205 Drive Penfield, Montreal, Quebec H3A 1B1, Canada. rmacle2@po-box.mcgill.ca

How repeatable a process is evolution? Comparative studies of multicellular eukaryotes and experimental studies with unicellular prokaryotes document the repeated evolution of adaptive phenotypes during similar adaptive radiations, suggesting that the outcome of adaptive radiation is broadly reproducible. The goal of this study was to test this hypothesis by using phenotypic traits to infer the genetic basis of adaptation to simple carbon-limited environments in an extensive adaptive radiation. We used a clone of the bacterium Pseudomonas fluorescens to found two sets of experimental lines. The first set of lines was allowed to adapt to one of 23 novel environments for 1100 generations while the second set of lines was allowed to accumulate mutations by drift for 2000 generations. All lines were then assayed in the 95 environments provided by Biolog microplates to determine the phenotypic consequences of selection and drift. Replicate selection lines propagated in a common environment evolved similar adaptive components of their phenotype but showed extensive variation in non-adaptive phenotypic traits. This variation in non-adaptive phenotypic traits primarily resulted from the ascendance of different beneficial mutations in different lines. We argue that these results reconcile experimental and comparative approaches to studying adaptation by demonstrating that the convergent phenotypic evolution that occurs during adaptive radiation may be associated with radically different sets of beneficial mutations.

UI MeSH Term Description Entries
D009154 Mutation Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations. Mutations
D010641 Phenotype The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment. Phenotypes
D011551 Pseudomonas fluorescens A species of nonpathogenic fluorescent bacteria found in feces, sewage, soil, and water, and which liquefy gelatin. Bacillus fluorescens,Bacillus fluorescens liquefaciens,Bacterium fluorescens,Liquidomonas fluorescens
D004777 Environment The external elements and conditions which surround, influence, and affect the life and development of an organism or population. Environmental Impact,Environmental Impacts,Impact, Environmental,Impacts, Environmental,Environments
D005075 Biological Evolution The process of cumulative change over successive generations through which organisms acquire their distinguishing morphological and physiological characteristics. Evolution, Biological
D000220 Adaptation, Biological Changes in biological features that help an organism cope with its ENVIRONMENT. These changes include physiological (ADAPTATION, PHYSIOLOGICAL), phenotypic and genetic changes. Adaptation, Biologic,Biological Adaptation,Biologic Adaptation
D012641 Selection, Genetic Differential and non-random reproduction of different genotypes, operating to alter the gene frequencies within a population. Natural Selection,Genetic Selection,Selection, Natural
D014644 Genetic Variation Genotypic differences observed among individuals in a population. Genetic Diversity,Variation, Genetic,Diversity, Genetic,Diversities, Genetic,Genetic Diversities,Genetic Variations,Variations, Genetic
D016000 Cluster Analysis A set of statistical methods used to group variables or observations into strongly inter-related subgroups. In epidemiology, it may be used to analyze a closely grouped series of events or cases of disease or other health-related phenomenon with well-defined distribution patterns in relation to time or place or both. Clustering,Analyses, Cluster,Analysis, Cluster,Cluster Analyses,Clusterings
D040961 Genetic Drift The fluctuation of the ALLELE FREQUENCY from one generation to the next. Evolution, Neutral,Drift, Genetic,Neutral Evolution

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