Game designer Laukosargas Svarog has created a virtual ecosystem in Second Life:

She’s noticed some limited forms of emergence (the holy grail of artificial life developers) particularly in the development of her plant life.

“It’s very sensitive to very small changes,” she says, “like if a gene emerges which gives a plant an extra seed in its lifetime, that can cause huge growth in its locale. And the opposite of course, one less causes thinning growth. I’ve also seen the same color become a dominant gene so all the meadow cup plants became blue once. Simple things like that emerge quite often.”
[Link]

Via boingboing