This name is a synonym of Populus tacamahacca var. lanceolata (Marshall) Farw..
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 50298276) with original publication details: Arbust. Amer. 108 1785.
This name was in version 1 of The Plant List, record tro-50298276.