Moderate Amounts of Epistasis are Not Evolutionarily Stable in Small Populations.
J Mol Evol
; 88(5): 435-444, 2020 07.
Article
in En
| MEDLINE
| ID: mdl-32350572
ABSTRACT
High mutation rates select for the evolution of mutational robustness where populations inhabit flat fitness peaks with little epistasis, protecting them from lethal mutagenesis. Recent evidence suggests that a different effect protects small populations from extinction via the accumulation of deleterious mutations. In drift robustness, populations tend to occupy peaks with steep flanks and positive epistasis between mutations. However, it is not known what happens when mutation rates are high and population sizes are small at the same time. Using a simple fitness model with variable epistasis, we show that the equilibrium fitness has a minimum as a function of the parameter that tunes epistasis, implying that this critical point is an unstable fixed point for evolutionary trajectories. In agent-based simulations of evolution at finite mutation rate, we demonstrate that when mutations can change epistasis, trajectories with a subcritical value of epistasis evolve to decrease epistasis, while those with supercritical initial points evolve towards higher epistasis. These two fixed points can be identified with mutational and drift robustness, respectively.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Epistasis, Genetic
/
Mutation Rate
Type of study:
Prognostic_studies
Language:
En
Journal:
J Mol Evol
Year:
2020
Document type:
Article
Affiliation country:
United States
Publication country:
ALEMANHA
/
ALEMANIA
/
DE
/
DEUSTCHLAND
/
GERMANY