The evolutionary advantage of replacers in the Moran process.

A single neutral replacer invading a well-mixed Moran population of size N has fixation probability of order 1/N rather than the standard 1/N, boosting evolutionary success.

• Why it matters: Random birth–death steps can waste events when the same type is chosen twice, limiting fixation under neutral or deleterious mutations.
• What they did: The study introduces replacers that, upon reproduction, always replace an individual of another type if available, and analyzes their selective advantage in well-mixed populations and one-dimensional lattices.
• The result: Replacers substantially boost fixation probability of neutral and deleterious mutants and are better protected after fixation, dominating mutation–selection equilibrium even with substantial costs (relative reproductive rate as low as 1/e for large N and small mutation rates).