Benefit of transferred mutations is better predicted by the fitness of recipients than by their ecological or genetic relatedness.

The effect of a mutation depends on its interaction with the genetic background in which it is assessed. Studies in experimental systems have demonstrated that such interactions are common among beneficial mutations and often follow a pattern consistent with declining evolvability of more fit genotypes. However, these studies generally examine the consequences of interactions between a small number of focal mutations.

PolyAna: analyzing synonymous and nonsynonymous polymorphic sites.

PolyAna (available at http://www.biol.sc.