Hi RAZD

The key is that diversity has begun the moment that two populations cease to share genes. If they later coalesce back into a common population then this just adds some new variations to the mix.

True enough but speciation I think has to wait until they are separated by more than distance or physical barriers, there has to be a genetic component at least in mate choice behaviours if not direct genetic incompatibility before they can be counted as separate species.

So they [meme’s] may hitchhike as well as be either +/-/neutral?

Yes though if they are indeed replicators in a Darwinian sense then they will spread and evolve based on their abilities to spread and evolve above their utility to the organisms which carry them. Obviously a meme that killed it’s host is not going to get passed on so there are limits to this and meme’s that are useful are likely to get a boost in organism capable of realizing the limits of the meme’s.

Russell