Nepenthes Rajah - Classification

Classification

Nepenthes rajah is not generally considered to be closely related to any other species, due to its unusual pitcher and leaf morphology. However, several attempts have been made to deduce natural groupings within the Nepenthes genus, which have grouped N. rajah with other species thought to share certain traits with it.

The Nepenthes were first split up in 1873, when Hooker published his monograph on the genus, titled "Nepenthaceae". Hooker distinguished N. pervillei from all other taxa based on its seeds, which lack the appendages typical of most Nepenthes. He placed it in the monotypic subgenus Anourosperma. All other species were subsumed in the second subgenus, Eunepenthes.

A second attempt to establish a natural subdivision within the genus was made in 1895 by Günther Beck von Mannagetta und Lerchenau in "Die Gattung Nepenthes". Beck kept the two subgenera created by Hooker, but divided Eunepenthes into three subgroups: Retiferae, Apruinosae and Pruinosae. Nepenthes rajah formed part of the Apruinosae (Latin: pl. of apruinosa: not frosted).

Nepenthes taxonomy was once again revised in 1908 by John Muirhead Macfarlane in his own monograph, "Nepenthaceae". Oddly, Macfarlane did not name the groups he distinguished. His revision is not generally considered to be a natural division of the genus.

In 1928, B. H. Danser published his seminal monograph, "The Nepenthaceae of the Netherlands Indies", in which he divided Nepenthes into six clades, based on observations of herbarium material. The clades were: the Vulgatae, Montanae, Nobiles, Regiae, Insignes and Urceolatae. Danser placed N. rajah in the Regiae (Latin: pl. of rēgia: royal). The Regiae clade as proposed by Danser is shown in the table to the right.

Most of the species in this clade are large plants with petiolate leaves, an indumentum of coarse reddish-brown hairs, raceme-like inflorescence, and funnel-shaped (infundibulate) upper pitchers. All bear a characteristic appendage on the lower surface of the lid near the apex. With the exception of N. lowii, the Regiae all have a mostly flattened or expanded peristome. The majority of species comprising Regiae are endemic to Borneo. Based on current understanding of the genus, Regiae appears to reflect the relationships of its members quite well, although the same cannot be said for the other clades. Despite this, Danser's classification was undoubtedly a great improvement on previous attempts.

The taxonomical work of Danser (1928) was revised by Hermann Harms in 1936. Harms divided Nepenthes into three subgenera: Anurosperma Hooker.f. (1873), Eunepenthes Hooker.f. (1873) and Mesonepenthes Harms (1936) (Latin: meso: middle; "middle" Nepenthes). The Nepenthes species found in the subgenera Anurosperma and Mesonepenthes differ from those in the Vulgatae, where Danser had placed them. Harms included N. rajah in the subgenus Eunepenthes together with the great majority of other Nepenthes; Anurosperma was a monotypic subgenus, while Mesonepenthes contained only three species. He also created an additional clade, the Distillatoriae (after N. distillatoria).

In his 1976 book, Nepenthes of Mount Kinabalu, Shigeo Kurata presented detailed photographs of lid nectar glands and the digestive glands of the trap interior. He divided the latter into the "lower", "upper" and "middle" parts.