  We derive a unified stochastic picture for the duality of a
resampling-selection model with a branching-coalescing particle process (cf.
http://www.ams.org/mathscinet-getitem?mr=MR2123250) and for the self-duality of
Feller's branching diffusion with logistic growth (cf. math/0509612). The two
dual processes are approximated by particle processes which are forward and
backward processes in a graphical representation. We identify duality relations
between the basic building blocks of the particle processes which lead to the
two dualities mentioned above.
