Genetic Divergence and Fitness Convergence under Uniform Selection in Experimental Populations of Bacteria
AUTOR(ES)
Korona, R.
RESUMO
Replicate populations of bacteria were propagated for 1000 generations in the laboratory. The growth substrate was periodically renewed, so that during most generations (cell doublings) it was not limiting. The final clones demonstrated about a 40% fitness increase when competed against their common ancestor. This increase was uniform both among and within populations despite extensive differentiation in correlated traits: cell size, resistance to starvation and dry mass of culture. It is suggested that genetic diversity developed because selection promoted any changes directing cell activity toward a higher maximum growth rate. Evolution of this trait halted at a similar level when some basic constraints on bacterial metabolism were met. The selective values of emerging mutations must have depended on the genetic background. They would be beneficial early in evolution but ineffective near the limit of adaptation. This hypothesis was tested for one mutation that affected both fitness and colony morphology. In some clones it was the first adaptive mutation and provided a third of the total fitness increase, but it was not assimilated by the clones that reached the adaptive ceiling in some other way. Near the limit of adaptation, epistasis levels off the fitnesses of genetically variable clones.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1207325Documentos Relacionados
- Genetic Divergence under Uniform Selection. II. Different Responses to Selection for Knockdown Resistance to Ethanol among DROSOPHILA MELANOGASTER Populations and Their Replicate Lines
- Divergence in Fitness and Evolution of Drug Resistance in Experimental Populations of Candida albicans
- Selection in Finite Populations with Multiple Alleles. III. Genetic Divergence with Centripetal Selection and Mutation
- Genetic Gain in Populations of TRIBOLIUM CASTANEUM under Uni-Stage Tandem Selection and under Restricted Selection Indices
- Genetic Loads and Fitness of Populations: I. the Effects of the Gene Stubble on Fitness of Experimental Populations of DROSOPHILA MELANOGASTER