The ecology, biogeography and systematics of the Austro-Papuan Nepenthes pitcher plants

Gary working in difficult conditions

Gary W Wilson, Australian Tropical Herbarium and School of Marine & Tropical Biology, James Cook University

Nepenthaceae is an Old World taxon of carnivorous plant containing a single genus, Nepenthes, characterised by lidded pitchers on the end of a twining prolongation of the leaf. The name is derived from the Greek 'nepenthe' meaning 'without grief', and refers to the passage in Homer’s Odyssey describing Helen adding the drug ‘nepenthe’ to wine offered to guests to relieve their cares. The genus contains c. 120 species. They are charismatic taxa and trade in and poaching of them is a concern.

Surprisingly little is known about the status, ecology and relationship of the species in Austro-Papuan region which extends from northern Queensland across the Trans-Fly Ecoregion in Papua New Guinea and West Papua, south of Good’s Line, which delineates the northern margin of the Australian plate.

Study Area

Three species of Nepenthes are recognised as occurring in Australia. Nepenthes mirabilis extends from the Wet Tropics through to China, but Nepenthes rowaniae and N. tenax, are known only from swamps in northern Cape York and not from New Guinea despite its proximity and similarity of habitat. This raises the question of where and when they evolved and if they have been overlooked on New Guinea. In addition, Nepenthes of uncertain status also occur in Queensland and warrant further investigation, single collections from Cape York in the National Herbarium are identified as N. alata, otherwise only in the Philippines, and N. alicae, reduced to a synonym of N. mirabilis by Danser in 1928, and their identity requires clarification, and we have no knowledge of the ecology of any species in the study area. A suite of species occurs on New Guinea; however, only N. mirabilis is known from the TransFly. This is surprising given the number of species on the island and presence of N. tenax and N. rowaniae in nearby Australia.

Nepenthes mirabilis with emerging flower
Photo © Gary Wilson

I am describing the ecology, systematics and biogeography of species in the study area, attempting to explain the evolutionary processes involved in the rise of them, and provide data for the better management of them. In addition, I plan to revise the IUCN status for N. tenax, N. rowaniae, enhance knowledge including that of Traditional Owners of Nepenthes, assist in the reduction of illegal take of and trade in Nepenthes by education and extension activities, and promote Nepenthes as a focus of nature-vased tourism in the study area (as is done on Borneo).

Studying Nepenthes in Australia is often challenging, e.g. N. tenax and N. mirabilis occur in swamps and many plants are submerged in the Wet Season and subjected to wildfires in the Dry Season. It is further complicated as the species hybridize and undescribed entities also occur. One, colloquially known as ‘mini-tenax’, occurs far into the swamps and is proving particularly difficult to study; crocodiles have little respect for botanists loitering in waist-deep water or pre-packed in aluminium containers.

Nepenthes mirabilis with spider prey
Photo © Gary Wilson

To define species, describe the ecology, understand the evolution, and determine the status of Austro-Papuan taxa and contribute to a wider study of Nepenthes being coordinated by Dr Charles Clarke in Kuala Lumpur I am collecting morphological, morphometric, ecological and gene sequence data. Duplicates of collections are being deposited in state and national herbaria and sequence data in the international database Genbank.

In 2011, I sampled populations of three species and undetermined taxa in a range of habitats in Queensland, and commenced ecological studies of N. mirabilis at a study site near Babinda. I published two articles in popular magazines and a scientific paper has been submitted for publication. I presented a Poster paper at the International Botanical Conference (IBC) in Melbourne, have presented two public seminars on the study, and featured in several press releases and radio interviews on the topic. My field work continues, I am about to commence laboratory work to extract DNA for sequencing, and am planning for the 2012 field season in Cape York, Papua New Guinea and West Papua.

Nepenthes mirabilis Photo © Gary Wilson

Nepenthes rowaniae Photo © Gary Wilson

Nepenthes tenax Photo © Gary Wilson

Green tree ants on N. mirabilis Photo © Gary Wilson

Nepenthes tenax with wasp Photo © Gary Wilson