Because adaptability is based on similarity of the performance curves expx and
exp0, which are directly comparable, it makes sense to define a euclidean
distance measure for adaptability:
expx curve tracks exp0 curve as closely as possible if environmental
conditions at t are worse in expx than exp0.
expx curve proportionally larger than exp0 curve if environmental conditions
at t are better in expx than exp0.
Because adaptability is based on similarity of the performance curves expx and exp0, which are directly comparable, it makes sense to define a euclidean distance measure for adaptability: