Pitcher plant  (Nepenthes burbidgeae)

Classified as Endangered (EN) on the IUCN Red List (1) and listed on Appendix II of CITES (3)

Arguably the most beautiful of the Bornean pitcher plants, Nepenthes burbidgeae is a vine which climbs to a height of about fifteen metres. Modified pitcher-shaped leaves hang from coiled tendrils, into which insects and other invertebrates fall (2). Nepenthes burbidgeae has light green leaves fringed with brown hairs. The pitchers are deep red on the exterior surface and the base of pitcher is off-white with pink splashes. The inner surface is white and is often lightly covered with pink blotches (2). The trumpet-shaped pitchers of Nepenthes burbidgeae contain an acidic fluid, secreted by the many glands which cover the inside surface of the lower half of the pitcher (4). The smooth and waxy upper inner surface of the pitcher makes it impossible for captive insects to gain a foothold (4), and a ridge of hardened tissue lining the mouth of the pitcher, the peristome, bears downward pointing teeth, also preventing insects from escaping (2). A lid overhangs the mouth of the pitcher preventing rain water from diluting the pitcher fluid (2).

Endemic to Mount Kinabalu, Borneo, Indonesia (1) (5).

Nepenthes burbidgeae is restricted to growing in soil on top of igneous rock at altitudes between 1,200 and 2,250 metres (1) (5), inhabiting mossy montane forest on the tops of steep slopes and ridges (2).

Pitcher plants are dioecious, meaning that male and female flowers grow on separate plants (4), and only begin to flower once the upper pitchers are produced (5). The flowers produce large amounts of nectar during the early evening and night, which evaporates by the morning. This nectar attracts flies during the early evening and moths at night to aid pollination. Once fertilised, a fruit usually takes about three months to develop and ripen. The fruits of Nepenthes species produce between 100 and 500 very light, winged seeds, which can measure up to 30 millimetres long, and are thought to be dispersed by the wind (2) (6). Despite enormous numbers of seeds being produced, only a few manage to germinate and only a fraction of those survive to maturity (2).

Carnivorous pitcher plants are adapted to grow in soils low in nutrients. Although the plants do gain some nutrition through the soil, and energy through photosynthesis, they supplement this with a diet of invertebrates, usually consisting of ants, cockroaches, centipedes, flies and beetles. Insects are attracted to the pitchers by their bright colours and nectar, which is secreted by glands situated on the lid and the peristome of the pitcher. The insects fall into the acidic fluid at the base of the pitcher and, unable to escape, they drown. Digestive enzymes are then released to break down the captured prey (4).

Despite the hostile environment of the pitchers, they can be home to number of animals. The red crab spider (Misumenops nepenthicola) inhabits pitcher plants in Malaysia, Singapore and Indonesia, including some species in Borneo. This spider ambushes insects that crawl into the pitcher, and preys upon other insects, such as mosquitoes, as they emerge from larvae that live in the pitcher fluid (2).

Nepenthes species are threatened by a combination of over-collection and habitat loss (2). The biodiversity of Indonesia is significantly threatened by widespread habitat destruction, caused by illegal and commercial logging and large agricultural projects such as rubber and oil palm plantations (7). Nepenthes burbidgeae has a highly localised distribution making this species particularly susceptible to extinction throught habitat destruction or catastrophic environmental events, such as drought or fire. In addition, montane species, such as Nepenthes burbidgeae, take longer to recover than lowland plants after such events, as growth is slower (2).

Nepenthes burbidgeae is found only on Mount Kinabalu, which is situated within Kinabalu National Park. This region’s protected status, along with the inaccessibility of many areas, offers this species some degree of protection particularly from collectors (2). It is listed under Appendix II of the Convention on International Trade in Endangered Species (CITES) which limits the international export of this species (3). However, trade is very difficult to regulate, as there is no requirement for internationally traded Nepenthes to be identified down to species level, and plants simply labelled as Nepenthes accounted for 94 percent of all exported Nepenthes plants between 1988 and 1993. This needs to be remedied and urgent attention is required to close other trade loopholes (2). Nepenthes species, including Nepenthes burbidgeae, are being increasingly cultivated, helping to reduce the impact on wild populations. Conservation efforts can be made more effective not only by the implementation and enforcement of protective laws, but also by the encouragement of artificial propagation and the establishment of habitat reserves (8).

For more information on Nepenthes species see:

• Clarke, C. (1997) Nepenthes of Borneo. NaturalHistory Publications, Kota Kinabalu, Malaysia.