I'd like to ask a question about the mechanisms and the rates of evolution, just to clarify for everyone who is reading. When I think about what I've read about the mechanisms, I think of things like natural selection and genetic drift. However, we were having a conversation earlier about species that seem to be optimally adapted to their environment. Presumably if this is the case, they are unlikely to show much evidence of evolution until the environment itself changes, forcing them to either adapt or go extinct. "Living fossil" species such as crocodiles, jellyfish and cockroaches appear to be very well-adapted to their environments. On the other hand, very rapid evolution has been observed to occur in some species that are colonising or adapting to a new environment, such as this weed.

Just a few ideas to work on here, if no other replies are forthcoming. Apologies if I'm jumping the gun.