Nepenthes macrophylla (Marabini) Jebb & Cheek

Clarke, C. & Moran, J. A., 2011, Incorporating ecological context: a revised protocol for the preservation of Nepenthes pitcher plant specimens (Nepenthaceae), Blumea 56 (3), pp. 225-228 : 226

Nepenthes macrophylla (Marabini) Jebb & Cheek – an example of a controversial taxon that is resolved through its ecological traits

Nepenthes villosa Hook.f. is a spectacular montane Nepenthes species that is endemic to Mt Kinabalu and Mt Tambuyukon in northern Sabah, Borneo ( Fig. 1a ). Along with the giant N. rajah Hook.f. , it generated substantial public and botanical interest when it was described in 1852 (see Phillipps et al. 2009), as the extraordinary degree of development of the peristome ribs was unlike that of any other pitcher plant known at that time. A few years later Hooker (1859) described a remarkably similar species from the same two mountains: Nepenthes edwardsiana H.Low ex Hook.f. ( Fig. 1b ). This species was distinguished from N. villosa by its elongated, tubular pitchers, simpler peristome structure, ebracteolate pedicels and sparser indumentum. Danser (1928) was of the opinion that these characteristics were insignificant, and reduced N. edwardsiana to a synonym of N. villosa . In contrast, Harms (1936) reinstated N. edwardsiana .

More recently, Marabini (1987) described N. edwardsiana subsp. macrophylla , which is confined to the summit region of Mt Trusmadi, approximately 60 km SE of Mt Kinabalu. This taxon was distinguished from N. edwardsiana by its very large, ovate leaf blades and ovoid pitchers with broad, concave pitcher lids and less well-developed peristome teeth ( Fig. 1c ). Despite these marked differences, Marabini (1987) did not feel that they were significant enough to warrant distinction of the two taxa at specific rank. Jebb & Cheek (1997) disagreed and raised N. edwardsiana subsp. macrophylla to specific rank, an interpretation that has been adopted by subsequent authors, but not without some reservations (see Clarke 1997).

On the basis of pitcher characteristics alone, the competing interpretations of N. macrophylla cannot be resolved objectively. However, Chin et al. (2010) demonstrated that N. macrophylla belongs to an extraordinary group of three Nepenthes species (the other two are N. rajah and N. lowii ) that trap the faeces of mountain tree shrews ( Tupaia montana Thomas ( Scandentia )) for nutritional benefit. Tree shrews visit the pitchers to feed on nectar produced by glands on the pitcher lid, and the concave structure of the lid results in the nectar being accessible only if the tree shrews sit astride the pitcher ( Fig. 1d ). Tupaia montana marks the location of valuable resources with faeces, and as pitcher nectar appears to be an important food source, these animals frequently defecate into the pitchers ( Clarke et al. 2009, Chin et al. 2010).

Chin et al. (2010) also demonstrated that the trap geometry of N. villosa is significantly different to that of N. macrophylla and that its pitchers do not trap tree shrew faeces. Field observations by C. Clarke indicate that the same applies to N. edwardsiana . Clearly, T. montana distinguishes N. macrophylla from N. edwardsiana and N. villosa as a source of food, providing a compelling argument (in addition to the morphological characteristics listed by Jebb & Cheek (1997)) for the recognition of the former taxon as a distinct species. While it is clear that field observations are essential to the elucidation of the relationship between N. macrophylla and tree shrews, it is likely that this association would have been detected much earlier if herbarium specimens included longitudinally dissected pitchers and brief notes about their contents, as this information is obscured when the pitchers are pressed.

Figures

Fig. 1 Pitchers of a. N. villosa; b. N. edwardsiana; c. N. macrophylla; d. N. rajah; showing Tupaia montana feeding at the inner surface of the pitcher lid. — Photo a, c, d: C. Clarke; b: C.C. Lee.