But you've put yourself in the position of either insisting that there's a naturalistic means by which the island could have been uniquely repopulated in the last few thousand years, or repudiating the Word of God. When God sits in judgment before you, He won't accept the dodge that you weren't talking about that at the time. You're really safer if you accept the naturalistic explanation.
I'm proving the title of this thread ....
There are still two things you haven't shown: A) that the island was necessarily devoid of both coral and palms during the last ice age, and B) that 10,000 years is insufficient for these to repopulate the island and diversify. (Furthermore, such diversification is not integral to the explanation, as the "distinctive" species could have arrived from elsewhere in essentially their modern form, with the parent stocks dying out in the interim.)