Nepenthes Eustachya - Related Species

Related Species

Nepenthes eustachya differs from N. alata in a number of morphological features. Jebb and Cheek outlined these differences when they restored the former as a valid species. Nepenthes eustachya has a lanceolate lamina with a rounded to sub-peltate apex, whereas that of N. alata is lanceolate-ovate with an acute or attenuate apex. The petiole also serves to distinguish these species: in N. eustachya it is scarcely or not winged at all, whereas in N. alata it is broadly winged. The pitchers of N. eustachya bear a simple or bifurcate spur, compared to the simple and acutely pointed appendage of N. alata. Mature parts of N. eustachya are glabrous, while N. alata bears an indumentum of reddish or whitish hairs. Jebb and Cheek also compared the structure of the pitcher base: that of N. eustachya is angular and woody, being gradually attenuate towards the tendril. The base of N. alata traps, however, has a similar texture to the rest of the pitcher and is abruptly attenuate towards the tendril.

Nepenthes alata exhibits great variability across its range and it is inevitable that some plants will deviate from the characters outlined by Jebb and Cheek. However, the overall combination of morphological differences appears to be stable and it is this that demarcates these species.

Nepenthes eustachya bears a superficial resemblance to N. mirabilis. It can be distinguished from that species on the basis of its lower pitchers, which lack wings, its fimbriate leaf margins on short shoots, and coriaceous leaves, as opposed to chartaceous in the latter.

Charles Clarke notes that the upper pitchers of N. eustachya, which have a pronounced globose base, may resemble those of N. clipeata from Borneo and N. klossii from New Guinea. Nevertheless, it would be difficult to confuse these species as they have little else in common and are geographically isolated from each other.

In 2001, Clarke performed a cladistic analysis of the Nepenthes species of Sumatra and Peninsular Malaysia using 70 morphological characteristics of each taxon. The following is a portion of the resultant cladogram, showing "Clade 5". It comprises the sister pair of N. eustachya and N. mirabilis with 72% support, as well as a weakly supported subclade (69%) that includes N. longifolia and the sister taxa N. rafflesiana and N. sumatrana with 58% bootstrap support.