Not that I doubt a long course of "competitive highness" will ultimately make the organisation higher in every sense of the word; but it seems most difficult to test it.

Look at the Erigeron canadensis on the one hand and Anacharis (70/3.

Anacharis (Elodea canadensis) and Erigeron canadensis are both successful immigrants from America.) on the other; these plants must have some advantage over European productions, to spread as they have.

Yet who could discover it?
Monkeys can co-exist with sloths and opossums, orders at the bottom of the scale; and the opossums might well be beaten by placental insectivores, coming from a country where there were no monkeys, etc.
I should be sorry to give up the view that an old and very large continuous territory would generally produce organisms higher in the competitive sense than a smaller territory.

I may, of course, be quite wrong about the plants of Australia (and your facts are, of course, quite new to me on their highness), but when I read the accounts of the immense spreading of European plants in Australia, and think of the wool and corn brought thence to Europe, and not one plant naturalised, I can hardly avoid the suspicion that Europe beats Australia in its productions.