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- Title
Understanding the Evolutionary Fate of Finite Populations: The Dynamics of Mutational Effects.
- Authors
Silander, Olin K.; Tenaillon, Olivier; Lin Chao
- Abstract
The most consistent result in more than two decades of experimental evolution is that the fitness of populations adapting to a constant environment does not increase indefinitely, but reaches a plateau. Using experimental evolution with bacteriophage, we show here that the converse is also true. In populations small enough such that drift overwhelms selection and causes fitness to decrease, fitness declines down to a plateau. We demonstrate theoretically that both of these phenomena must be due either to changes in the ratio of beneficial to deleterious mutations, the size of mutational effects, or both. We use mutation accumulation experiments and molecular data from experimental evolution to show that the most significant change in mutational effects is a drastic increase in the rate of beneficial mutation as fitness decreases. In contrast, the size of mutational effects changes little even as organismal fitness changes over several orders of magnitude. These findings have significant implications for the dynamics of adaptation.
- Subjects
BIOLOGICAL evolution; POPULATION; GENETIC mutation; BIOLOGICAL variation; ARTIFICIAL selection of animals; BIOLOGICAL adaptation
- Publication
PLoS Biology, 2007, Vol 5, Issue 4, p0922
- ISSN
1544-9173
- Publication type
Article
- DOI
10.1371/journal.pbio.0050094