[lyner]

If you pick the right definition of successful you can make this a really odd concept.
For example, potatoes are enormously successful because they have trained humans to ensure that the potato is widely grown and will not become extinct if we can help it.
That makes the humble spud very successful.

And the tobacco plant!

[Bored chemist]

Not to mention papaver somniferum and a bunch of others; good point.

[DoctorBeaver (OP)]

Somehow I don't think that papaver somniferum can be a contributing factor to the success of the human race  []

[lyner]

No. It's quite the other way round!

[damiri]

The most "successful" living organisms on the planet got to be bacteria. (someone mentioned viruses but they are not usually considered to be alive).

I just can't think of another animal that is spread out to as many places or adapted to as many conditions.

D

[DoctorBeaver (OP)]

damiri - That is very true.