I’m not going to lose sleep over it…but Michael Dirr says all the species of gum live in Virginia and much of the east. The difference in Nyssa aquatica is it can live in flooded land just like cypress all year long. Nyssa sylvatica cannot. Most of the southern tupelo have larger leaves and fruit than Nyssa sylvatica. There is also a Chinese black gum.
The online encyclopedia can be interesting and a quick solution to some problems, but it’s not on the above quote.