When total diversity in the neutral model became small (similar to the number of continents), a significant increase in diversity is observed as a result of continental drift. This is because in the extreme case of low speciation rate, after a sufficiently long period of time, a fragmented set of continents necessarily maintains a separate species in each, whereas a single supercontinent would only contain one species. As the speciation rate decreases still further, the system ultimately converges to a state where there is still only one global species, because the speciation event bringing it into existence is pushed back to a time when the continents were still connected. Explanation:
