Again from Discovery Channel, this time about... toads:http://dsc.discovery.com/news/briefs/20060213/toad_ani.html
A breed of toads is slowly invading Australia (well, not invading, but just spreading out into a new area... but you get the idea). They breed quickly, can poison potential predators (They are named 'Toxic Cane Toads', guess why), and eat lots of insects.
The really interesting bit is, that the ones _at the front_ of the invasion line have longer legs then their already settled colleagues. Once settled in, the mutation dies out - it is useful to be first on the frontier, where no toad has jumped before.
The whole 'invasion' has begun only some seventy years ago. Around 1950, the speed of their spreading was some seven miles per year - today it is 30 miles per year.
This only says that, given the right conditions, some species may be able to evolve much faster than is usually thought possible.