Seeds of annual plants in stochastic environments like deserts, 
may remain dormant in the soil for years. This adaptive mechanism, 
called dormancy, has be shown to be an evolutionarily stable strategy (ESS).
The standard model to find the ESS in this system predicted that at any
point in time the germination rate of the seeds should be the same for
all seeds in the bank.
     However, empirical data indicated that there should be variation 
in germination rate depending on factors like seasons quality or age 
of seeds.  This implies that at each point in time the seed bank should
contain seeds with different germination probabilities. To find the ESS
is therefore necessary to introduce a class structure in the seed bank
and to compute the ESS of every class. In this talk I will show how 
to compute the ESS for two cases: an age structured seed bank, and for 
a 'maternal' structure that takes into account the maturation environment.
I will also point to some theoretical open problems.

Recent publications:

K. Tielboerger, A. Valleriani "Can seeds predict their future?
Germination strategies of density-regulated desert annuals", OIKOS 111,
235 (2005)

A. Valleriani "Algebraic determination of the evolutionary stable
germination fraction" Theoretical Population Biology 68, 197 (2005)

A. Valleriani, K. Tielboerger "Effect of age on germination of dormant
seeds", accepted for publication in Theoretical Population Biology.