Asexuals, Polyploids, Evolutionary Opportunists...: The Population Genetics of Positive but Deteriorating Mutations

Some genetic phenomena originate as mutations that are initially advantageous but decline in fitness until they become distinctly deleterious. Here I give the condition for a mutation–selection balance to form and describe some of the properties of the resulting equilibrium population. A characterization is also given of the fixation probabilities for such mutations.