  We investigate various aspects of the (biallelic) Wright-Fisher diffusion
with seed bank in conjunction with and contrast to the two-island model
analysed e.g. in Kermany, Zhou and Hickey, 2008, and Nath and Griffiths, 1993,
including moments, stationary distribution and reversibility, for which our
main tool is duality. Further, we show that the Wright-Fisher diffusion with
seed bank can be reformulated as a one-dimensional stochastic delay
differential equation, providing an elegant interpretation of the age structure
in the seed bank also forward in time in the spirit of Kaj, Krone and Lascoux,
2001. We also provide a complete boundary classification for this
two-dimensional SDE using martingale-based reasoning known as McKean's
argument.
