Long-term adaptation of epistatic genetic networks.
Gene networks are likely to govern most traits in nature. Mutations at these genes often show functional epistatic interactions that lead to complex genetic architectures and variable fitness effects in different genetic backgrounds. Understanding how epistatic genetic systems evolve in nature remains one of the great challenges in evolutionary biology. Here we combine an analytical framework with individual-based simulations to generate novel predictions about long-term adaptation of epistatic networks. We find that relative to traits governed by independently evolving genes, adaptation with epistatic gene networks is often characterized by longer waiting times to selective sweeps, lower standing genetic variation, and larger fitness effects of adaptive mutations. This may cause epistatic networks to either adapt more slowly or more quickly relative to a nonepistatic system. Interestingly, epistatic networks may adapt faster even when epistatic effects of mutations are on average deleterious. Further, we study the evolution of epistatic properties of adaptive mutations in gene networks. Our results show that adaptive mutations with small fitness effects typically evolve positive synergistic interactions, whereas adaptive mutations with large fitness effects evolve positive synergistic and negative antagonistic interactions at approximately equal frequencies. These results provide testable predictions for adaptation of traits governed by epistatic networks and the evolution of epistasis within networks.
Yukilevich
Roman
R
Department of Ecology and Evolution, State University of New York, Stony Brook, New York 11794, USA. yukilevi@life.bio.sunysb.edu
Lachance
Joseph
J
Aoki
Fumio
F
True
John R
JR
D000220:Adaptation, Biological; D000483:Alleles; D003198:Computer Simulation; D004843:Epistasis, Genetic; D019143:Evolution, Molecular; D053263:Gene Regulatory Networks; D014644:Genetic Variation; D008957:Models, Genetic; D009154:Mutation; D012641:Selection, Genetic; D013997:Time Factors