In 1997, Matthew Jebb and Martin Cheek published their monograph "A skeletal revision of Nepenthes (Nepenthaceae)", in which they referred to N. dubia specimens from Mount Talang (Kurata s.n. SING) and the mountains of the Tjampo region near Payakumbuh (Meijer 6949 L).
Nepenthes eustachya × N. longifolia has been recorded from a number of locations near Payakumbuh and Sibolga, where its parent species are sympatric.