The diversity plot _should_ show how many variants a gene lasts over time. In the web one, because of perf you cant have alot of population and steps(mating to make new ones) it looks kinda flat :) If you increase the population and steps substantially, it will run _much_ slower and take alot longer for a generation, but you should end up with more diversity.
Id really only recommend doing this on the desktop version :)
I'll check to make sure thats all working properly. I havent looked at this for a while.