Human-Time Speciation

Just a regular Culex pipiens mosquito.

We all know that random mutations and artificial selection is the mechanism that leads to that advent of new species. The problem is, it's so darn hard to observe in the wild because of how long it usually takes. This is a process that can take tens of thousands of years.

(Note: The definition of "species" I'm going with is a set of animals that can breed together and produce fertile offspring.)

However, it doesn't always have to take that long. Bill Nye wrote about a species that evolved over the course of what could be a human lifetime: a new form of mosquito.

This new species came into being as an isolated population of regular, ol' mosquitoes that made it into the London Underground. Of course, mosquitoes have lived on the British Isles for ages. But, scientists suspect that during the London Blitz of World War II, when citizens would seek refuge underground, mosquitoes followed them down and were capable of establishing a colony by breeding in the standing water that formed near the tracks.

With this steady supply of human blood and puddles for their eggs, these mosquitoes saw no reason to reemerge from underground. As a result, they stopped interbreeding with their above-ground counterparts.

Now, this is where the evolution takes place. Over time, the two groups began to change their habits. In the climate-controlled Tube, the underground mosquitoes dropped their ability to hibernate during the winter months. They reconfigured themselves to feed exclusively on mammals, mostly humans. Also, they gained the ability to breed in confined spaces, which the above-grounders can't do.

Physiologically, the two species are very similar. I guess only about fifty years isn't enough time to produce any really neat external changes in mosquitoes. However, over the course of those fifty years, the two have drifted genetically enough to the point where it's very hard for the two of them to mate successfully together.

Most of the time, the two groups cannot produce eggs at all. Sometimes, they'll produce eggs; but, that new generation is infertile (the mules of the mosquito world). While it's is probably open to interpretation, this seems close enough for me (a nobody on the internet) to declare them separate species.

Sources:
"Undeniable: Evolution and the Science of Creation" – Bill Nye
"Culex pipiens in London Underground tunnels: differentiation between surface and subterranean populations" – Katharine Byrne and Richard A. Nichols (Heredity 82, 1999)