Perspectives on Evolution

[Anomalocaris]

What do you think there is when there is a population of creatures sharing sufficient genetic similarity such that they can interbreed and exchange genes amongst themselves, but not breed with those from outside the population, thus confining the interbreeding into discrete pools?

Each individual isn't sharing its genetic information with all the others.  It's not actually a communal property.

Of course we are.  That’s why we screw.  The more we screw around, the more broadly we share our genetic information.

To say we are not sharing genetic information with all the others is like saying when first adding a dye to a pool of water, the dye does not mix evenly with all parts of the pool.   Eventually the dye, if it does not have a chemical shelf life, will.   So the genetic material you share with your Partner will become part of your offspring, who will then share them with others.  Your genetic material, assuming it doesn’t have a equivalent of shelf life in the form of conferring reproductive handicap, will eventually mix thoroughly, but dilutely, like the dye into the entire gene pool.

If we do devolve into divergent species, would would happen to our reproductive compatibility?  I'd imagine that it would be something like bloodtype-- certain subsets of the species could interbreed with other certain subsets, and eventually those subsets if they continued to diverge would end up with breeding

The definition of divergent species is reproductive incompatibility.  So when species diverge, the stop being able to carry on sharing genes.  

It won’t be an abrupt cutoff.   Instead some limitations on reproductive compatibility first arise, and then these limitations become severe, until eventually it either becomes impossible for members of the two population to share genes through sexual reproduction at all, or the offspring carrying the shared genes are all infertile and the shared genes resulting from the interbreeding can not further mix back into each population.