The incredible diversity of Tropical Pitcher Plants (Nepenthes) becomes more evident each year as new species continue to be discovered across Southeast Asia. As recently as 1997, a total of only 82 Nepenthes were recognized, but in the past 15 years new findings and some taxonomic splits bring the world total to nearly 140 species today. Many of these new discoveries not only showcase the fascinating ecological adaptations and trap designs that make these carnivorous plants so successful, but they also help to shed light on their possible evolutionary relationships and biogeographical pathways.

I was fortunate to be able to contribute towards several papers in a recent publication “The New Nepenthes – vol. 1″ (Dec 2011) which compiles work from multiple authors and describes eight new Nepenthes species that have been found in recent years. Two of these, N. undulatifolia (below left) and N. nigra are from Sulawesi, an island with a relatively impoverished Nepenthes flora of only 11 species. The highly unusual N. undulatifolia was an exciting find for botanists because it could not be clearly grouped with any other closely related species.

The remote Hose Mountains in central Sarawak, an area where I had discovered two other endemic Nepenthes in 2001, yielded another new species, N. appendiculata (below right), during a study in 2011. This species was named for the remarkable swollen appendage protruding from the tip of the pitcher lid, a feature unlike any other species in the genus. Presumably an aid in the attraction of insect prey, this appendage is brightly colored and riddled with large nectar glands. Further field work may determine what types of insects this plant specializes in feeding on.

References:

Jebb, M. & M. Cheek (1997) A Skeletal Revision of Nepenthes (Nepenthaceae). Blumea 42: 1-106.

Lee, C.C., G. Bourke, W. Taylor, Y.S. Teck, K. Rembold (2011) Nepenthes appendiculata, a new Pitcher Plant from Sarawak. In The New Nepenthes, Redfern Natural History Publications Ltd. 1: 24-35.

Lee, C.C., A. Wistuba, J. Nerz, U. Zimmermann, A.P. Paserang, R. Pitopang (2011) Nepenthes undulatifolia, a new Pitcher Plant from South East Sulawesi. In The New Nepenthes, Redfern Natural History Publications Ltd. 1: 492-505.

Nerz, J., A. Wistuba, C.C. Lee, G. Bourke, U. Zimmermann, S. McPherson (2011) Nepenthes nigra, a new Pitcher Plant from Central Sulawesi. In The New Nepenthes, Redfern Natural History Publications Ltd. 1: 468-491.

In late 2010 I was fortunate to be able to join a team of researchers investigating animal interactions with the giant pitcher plant Nepenthes rajah. Endemic to the cool and mist-shrouded slopes of Mount Kinabalu and Mount Tambuyuon in northern Borneo, this is not only one of the world’s largest Nepenthes but also the source of the original stories of “rat-eating” carnivorous plants. There exist a number of confirmed incidents of this plant consuming small mammals which are unfortunate enough to fall within the voluminous pitchers. Recent research however, has shed light on a far more interesting and complex animal/plant relationship, and prior to our 2010 work it had been already shown that the Mountain Treeshrew (Tupaia montana) visits the pitchers of N. rajah (as well as several other Bornean Nepenthes) to feed on the sweet nectar exuding from beneath the pitcher lid. The plant benefits from these visits by frequently collecting the treeshrew’s scat which fall inside the pitcher and are a valuable source of nutrients.

During the field work it was observed that some of the animal droppings found on and in the pitchers appeared different than those left behind by the Mountain Treeshrew. However, despite many days of watching the plants during daylight hours, treeshrews were the only mammals seen to visit the plants. It wasn’t until camera equipment was left in place to monitor the plants during the night that we ascertained the presence of another animal, the Summit Rat (Rattus baluensis) at the pitchers. This is the first instance confirming a rodent/Nepenthes relationship, and it is presumed that it matches the treeshrew/Nepenthes mutualism albeit nocturnally. The photo here, the first ever to illustrate this interaction, shows an image I obtained at night by use of an infrared camera trap positioned adjacent to the pitcher and illuminated by multiple strobes.

Unlike the related Nepenthes lowii, another Bornean pitcher plant which has lost its means to trap insects and depends entirely on the treeshrew droppings for its nutrients, N. rajah retains its carnivorous apparati, a slippery peristome and smooth pitcher walls, and still consumes prey. It is quite likely that the records of rats and treeshrews having drowned in N. rajah pitchers were not instances of these mammals seeking out a source of water (as has been assumed in the past), but rather the result of unfortunate animals falling into their “toilet”.

References:

Chin, L.J., J.A. Moran, C. Clarke (2010) Trap geometry in three giant montane pitcher plant species from Borneo is a function of tree shrew body size. New Phytologist 186: 461–470.

Clarke, C.M., U. Bauer, C.C. Lee, A.A. Tuen, K. Rembold (2009) Tree shrew lavatories: a novel nitrogen sequestration strategy in a tropical pitcher plant. Biology Letters 5: 632–635.

Greenwood, M., C. Clarke, C.C. Lee, A. Gunsalam & R.H. Clarke (2011) A Unique Resource Mutualism between the Giant Bornean Pitcher Plant, Nepenthes rajah, and Members of a Small Mammal Community. PLoS ONE 6:6.