Nepenthes Inermis - Related Species

Related Species

Nepenthes inermis belongs to a group of closely related montane Sumatran species that includes N. dubia, N. flava, N. jacquelineae, N. jamban, N. talangensis, and N. tenuis. These species are characterised by infundibular upper pitchers and highly viscous pitcher fluid.

Nepenthes inermis is thought to be most closely related to N. dubia. However, it is easily distinguished from that species as it completely lacks a peristome in its upper pitchers unlike the latter. The pitchers are also usually green, while those of N. dubia tend to be yellow to orange in colour.

In 2001, Charles Clarke performed a cladistic analysis of the Nepenthes species of Sumatra and Peninsular Malaysia using 70 morphological characteristics of each taxon. The following is part of the resultant cladogram, showing "Clade 1", which has 51% bootstrap support. Its most strongly supported subclade is the sister pair of N. inermis and N. dubia, having 95% support.

In his description of the Bornean species N. campanulata, botanist Shigeo Kurata suggested that it may be closely related to N. inermis. However, other taxonomists disagree with this hypothesis. While these two species are similar in general stature and pitcher morphology, they are not only separated by great geographical distance, but also occur in completely different habitats; N. campanulata is a lowland species endemic to limestone substrates, whereas N. inermis usually grows as an epiphyte at elevations of 1500 to 2600 m.