AustinG writes:
I pose this question: How will we know speciation when we see it?
Our best bet for observing animal populations on the cusp of speciation is in creatures with very short generation gaps (like 2 weeks) in environments that are known to be new (usually due to our own activities).
The London Underground mosquitoes are a well known example of this. They were first noticed in the war, during the blitz, when people sleeping in the underground were being bitten by them. They don't breed easily with their above ground parent group.
Here's a paper which shows, interestingly, that reproductive isolation seems to be more advanced in the north of the city than the south. Evolution in action!
Culex pipiens in London Underground tunnels: differentiation between surface and subterranean populations | Heredity
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