Base-graphics plot of a hillred() result. For each diversity order q it
shows the per-sample neutral diversity (x) against phylogenetic/functional
diversity (y), overlaid with the fitted saturating curve
y = -a * 2^(-x / b) + c. A curve that bends sharply and plateaus well below
the points' spread indicates high redundancy; a near-linear fit indicates
low redundancy. This mirrors the profile plot of hillprof().
Usage
# S3 method for class 'hill_redundancy'
plot(x, ...)