Impact of epistasis and pleiotropy on evolutionary adaptation
Author Affiliations
1Keck Graduate Institute of Applied Life Sciences, Claremont, CA 91711, USA
2Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48823, USA
3BEACON Center for the Study of Evolution in Action, Michigan State University, East Lansing, MI 48823, USA
4Department of Computer Science and Engineering, Michigan State University, East Lansing, MI 48823, USA
*Author for correspondence (ostman@msu.edu).
Abstract
Evolutionary adaptation is often likened to climbing a hill or peak. While this process is simple for fitness landscapes where mutations are independent, the interaction between mutations (epistasis) as well as mutations at loci that affect more than one trait (pleiotropy) are crucial in complex and realistic fitness landscapes. We investigate the impact of epistasis and pleiotropy on adaptive evolution by studying the evolution of a population of asexual haploid organisms (haplotypes) in a model ofN interacting loci, where each locus interacts with K other loci. We use a quantitative measure of the magnitude of epistatic interactions between substitutions, and find that it is an increasing function of K. When haplotypes adapt at high mutation rates, more epistatic pairs of substitutions are observed on the line of descent than expected. The highest fitness is attained in landscapes with an intermediate amount of ruggedness that balance the higher fitness potential of interacting genes with their concomitant decreased evolvability. Our findings imply that the synergism between loci that interact epistatically is crucial for evolving genetic modules with high fitness, while too much ruggedness stalls the adaptive process.
evolution, epistasis, gene networks, strong mutation
Received April 28, 2011.
Accepted June 2, 2011.This Journal is © 2011 The Royal Society
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