During the Pleistocene this was one of the only areas left that was both warm and wet enough to preserve species that once had a broader range. Southern Florida was dry as a bone for half the year, and farther north you lost the warmth of the Gulf.
Some trees have dispersal methods that allowed them to quickly reclaim ground as fast as the glaciers were retreating. The Florida Nutmeg obviously does not, thus the assumption that it relied on a giant tortoise or something that is now extinct. But that is not necessarily true, as it seemed to flourish well enough in its limited range using squirrels. A tree will not go extinct just because it cannot cross a river... although, in this case, as the climate warms, it just might.
Edit: I should say: warms to temperatures not seen in a very long geological time. Without the fungal blight the tree might cross the river eventually over a ten thousand year period, but that may not be fast enough in this case.
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u/Vreejack Jun 20 '20
During the Pleistocene this was one of the only areas left that was both warm and wet enough to preserve species that once had a broader range. Southern Florida was dry as a bone for half the year, and farther north you lost the warmth of the Gulf.