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).
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In 2009, Adrian Y. Wartono observed a putative cross between N. dubia and N. jamban in an area where these two species grew with N. lingulata and N. rhombicaulis.
In the wild, N. izumiae is known to form natural hybrids with N. dubia and N. jacquelineae.
Specimens of a putative natural cross between N. dubia and N. jacquelineae have also been recorded.
Nepenthes clipeata | Nepenthes bokorensis | Nepenthes | Nepenthes rajah | Nepenthes mantalingajanensis | Nepenthes klossii | Nepenthes faizaliana | Nepenthes epiphytica | Nepenthes abgracilis | Nepenthes rigidifolia | Nepenthes mira | Nepenthes khasiana | Nepenthes kerrii | Nepenthes deaniana | Nepenthes cid | Nepenthes aristolochioides | Nepenthes viridis | Nepenthes ovata | Nepenthes mirabilis | Lindernia dubia | Nepenthes spathulata | Nepenthes rhombicaulis | Nepenthes pitopangii | Nepenthes × kinabaluensis | Nepenthes holdenii | Nepenthes × harryana | Nepenthes dubia | Nepenthes burbidgeae | Nepenthes bellii | ''Lindernia dubia'' var. ''inundata'' |