Inter- and intra-specific variation in prey assemblages and inhabitant communities in Nepenthes pitchers in Sumatra

Abstract

Prey assemblages and inhabitant communities in pitchers were compared among 10 Nepenthes Linnaeus 1753 species with various pitcher morphologies in West Sumatra, Indonesia. There were significant differences in the number of prey organisms trapped per pitcher among Nepenthes species and among pitcher ages but no significant differences among localities nor between the vertical positions of pitchers. Prey assemblages of eight Nepenthes species were predominated by ants. Nepenthes bongso Korthals 1839 and N. albomarginata Lobb 1849 had prey assemblages characterized by high frequencies of midges and termites, respectively. Pitchers captured prey organisms not by random trapping but by attracting specific groups of organisms.

Inhabitant fauna was largely similar among Nepenthes species except for N. bongso which fostered no inhabitants. The typical inhabitant community was composed of Toxorhynchites Theobald 1901 larvae as aquatic predators, culicid larvae as filter feeders and ceratopogonid larvae as detritus feeders. There were significant differences in the number of inhabitants per pitcher both among Nepenthes species and among pitcher ages, but not among localities nor between the vertical positions of pitchers. An ecological role of inhabitants in accelerating nutrient cycling in a pitcher ecosystem and the mutual relationship between Nepenthes species and their inhabitants were discussed.

Key Words:

• Nepenthes
• community structure
• pitcher ecosystem
• prey trapping
• Sumatra