This name is a synonym of Oenothera siambonensis W. Dietr..
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 50220852) with original publication details: Ann. Missouri Bot. Gard. 64(3): 606–609, f. 98–99, 165 1977.
This name was in version 1 of The Plant List, record tro-50220852, and has not been changed.