Pitcher plant  (Nepenthes fusca)

Classified as Vulnerable (VU) on the IUCN Red List (1) and listed on Appendix II of CITES (3).

Nepenthes fusca belongs to a group of spectacular carnivorous plants known as tropical pitcher plants (Nepenthes), which are equipped with large, modified, pitcher-shaped leaves that trap and digest small organisms (4). These deadly traps hang from coiled tendrils, and are filled with acidic digestive juices. In order to prevent the digestive liquid from being diluted by rainwater, the pitchers are covered by small lids as they grow, which open up when the pitchers are fully developed (4). Nepenthes fusca typically has very slender, pipe-shaped lower pitchers, and more funnel-shaped upper pitchers (5), with distinctive, narrow, triangular-shaped lids (6). The colour of the pitchers varies, but is often dark green heavily marked with maroon (5), and the brim (peristome) around the mouth of the pitcher’s opening can be reddish to nearly black, often with conspicuous pale and dark stripes (5) (7).

Found only on the island of Borneo, in Brunei Darussalam, Kalimantan (Indonesia), and Sabah and Sarawak (Malaysia) (1).

This pitcher plant is found growing in mossy forests on ridge tops at between 1,200 and 2,500 metres above sea level (1). This is primarily an epiphytic species, meaning that it naturally grows upon other plants, but without deriving any nourishment from them (2).

Nepenthes pitcher plants have evolved carnivorous habits as the answer to growing in extremely nutrient-poor habitats (2) (4). The plants are able to break down and absorb nitrogen and other nutrients from animals, usually invertebrates such as insects, that fall into the pitchers. This supplements any nutrition gained from the soils and therefore allows these plants to survive where others may not. Nepenthes plants attract their prey with nectar, aromas and visual signals such as colour (4). The brim of the pitcher, the peristome, produces the highest amount of nectar, and animals stepping on the slippery, waxy surface of the peristome often fall in. There, unable to escape, they drown in the pitcher fluid and their bodies are broken down by digestive enzymes (2).

Nepenthes are dioecious, meaning that there are separate male and female plants. Likely pollinators include flies, moths, beetles, bugs and ants, which have all been observed visiting the flowers. The fruit takes around three months to develop, and can contain 500 or more seeds, which are very light and have long wings, and are carried by the wind to aid dispersal (2).

The main threat to tropical pitcher plants (Nepenthes) is habitat destruction. However, as popular ornamental plants, they are also widely collected from the wild, and due to their low population numbers, commercial collection and illegal trade has had a serious impact (4).

All Nepenthes species are listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), which restricts the legal trade of these plants. Methods have also been developed to produce tropical pitcher plants from tissue culture, and the horticulture and cultivation of plants produced by this process may significantly help reduce the impact on wild populations (4).