It is hypothetically possible to have X number of alleles, pass them all along (i.e. do not select for any) and then add, say, 2 mutations to that set of alleles, and the result would be a information decrease. It seems that in reality, though, that selection acts much faster than mutation does (i.e. most mutations are disadvantageous and are generally deselected) and consequently information increases over time.
However, without mutation what exactly are you "selecting" for? This is an area I'm very interested in, but quite the "newbie". I understand that the more alleles one has the more importance/information if one is selected, but I am, initially, disagreeing with the selection w/o mutation...probably because I am not understanding what you've said very well.