Nepenthes Longifolia - Related Species

Related Species

Nepenthes longifolia is thought to be most closely related to N. sumatrana; the stem and lamina of these species are virtually identical in appearance. Nevertheless, N. longifolia can be distinguished from N. sumatrana on the basis of a number of significant and stable morphological differences. The tendrils on rosette leaves of N. longifolia are exceptionally long, reaching 110 cm, while those of N. sumatrana are not known to exceed 60 cm. As a result, the lower pitchers of N. longifolia are usually around 1/10 the length of the tendril, compared to 1/5 in the case of N. sumatrana. Although the lower pitchers on immature rosettes are similar in general morphology, the species differ in the shape of lower pitchers on rosettes sprouting from mature plants. Those of N. sumatrana are ovoid throughout, with an orbicular lid and the hip immediately beneath the peristome, and are contracted at an angle of 45° to the mouth. Those of N. longifolia are ovoid in the lower parts, having the hip around the middle and an ovate lid. In addition, the upper pitchers of N. longifolia do not give off a noticeable smell, whereas those of N. sumatrana have a sweet, fruity fragrance. In addition, the upper pitchers of N. longifolia are only infundibular in the lower parts, compared to the wholly infundibular aerial pitchers of N. sumatrana. Furthermore, the peristome of N. longifolia, although distinctly notched, is never raised at the front like in N. rafflesisna, unlike that of N. sumatrana, which has a very pronounced raised section. In their description of N. longifolia, Nerz and Wistuba also used the structure of the inflorescence to distinguish these taxa, but subsequent observations have shown that both species produce one- and two-flowered partial peduncles.

Nepenthes longifolia is also closely related to N. rafflesiana. It can be distinguished from that species on the basis of its fringed leaf margins, very long tendrils of rosettes, upper pitchers that are cylindrical above the hip, and the notched peristome which is not greatly expanded near the lid as in N. rafflesiana.

Plants that resemble the type of N. longifolia grow along the road from Sibolga to Tarutung in North Sumatra. They are atypical of the species in that the leaf bases are not decurrent along the internode, some of the hairs lining the leaf margins are caducous, and the plants grow in both exposed sites and amongst dense vegetation. This taxon is also similar to, and may be conspecific with, the obscure N. beccariana.

Nepenthes beccariana was described by John Muirhead Macfarlane in 1908 based on a specimen collected on Nias, an island located approximately 120 km from the port town of Sibolga. Twenty years later, B. H. Danser synonymised the taxon with N. mirabilis in his seminal monograph "The Nepenthaceae of the Netherlands Indies", although he did not see the type specimen of N. beccariana. In 2000, Jan Schlauer and C. Nepi examined the type specimen of N. beccariana and noted significant differences between it and N. mirabilis, suggesting that it should be restored as a distinct species. Charles Clarke agrees that N. beccariana appears to be distinct from both N. mirabilis and N. sumatrana but notes that if N. beccariana is found to be conspecific with N. longifolia, the latter taxon would become a junior synonym of the former. However, observations of N. beccariana at the type locality would need to be carried out to resolve this taxonomic confusion, since the type specimen of N. beccariana only consists of fragments of three leaves and three pitchers (two rosette pitchers and one upper pitcher) and is in a damaged state; the leaves are separated from the stem such that their attachment is unknown.

In 2001, Clarke published a cladistic analysis of the Nepenthes species of Sumatra and Peninsular Malaysia based on 70 morphological characteristics of each taxon. The following is a portion of the resultant cladogram, showing part of "Clade 5", which has 69% bootstrap support. The sister pair of N. rafflesiana and N. sumatrana has 58% support. N. beccariana was not included in this study.

Seedlings of N. adnata and N. longifolia are virtually indistinguishable, although mature plants have few morphological features in common. Clarke writes that N. longifolia is likely to be one of the closest relatives of N. adnata.