  Epistasis is a key concept in the theory of adaptation. Indicators of
epistasis are of interest for large system where systematic fitness
measurements may not be possible. Some recent approaches depend on information
theory. We show that considering shared entropy for pairs of loci can be
misleading. The reason is that shared entropy does not imply epistasis for the
pair. This observation holds true also in the absence of higher order
epistasis. We discuss a refined approach for identifying pairwise interactions
using entropy.
