Dune Soapberry (Deinbollia oblongifolia)
Source tree from Top Tropicals, Dec 2016
This is not a Longan, even though I am listing it in the same category as Longans. Dune Soapberry is related to Longan, Lychee (Litchi), and Rambutan. But this tree is native to Africa and is much more heat and drought tolerant. Mine is still small (1-2 ft tall) and is planted on the south side of my Longans. It does not get full sun, but the sun it does get does not seem to faze it.