Introduction
Rubiaceae
Asclepiadaceae
Nepenthaceae
Bromeliaceae
Orchidaceae
Polypodiaceae
Ecology and
evolution
Cultivation
References
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Nepenthaceae
The Nepenthes vines of Asia are the largest and most spectacular carnivorous plants. Several species have a symbiotic relationship with ant colonies (Joel, 1988). Foraging ants visit Nepenthes plants to feed on the nectar produced at the mouth of the pitchers. Some of the ants are trapped and digested by the plant, but the majority return safely to the nest. Since only non-breeding workers are consumed, this ant-plant relationship can be considered mutualistic. The colony as a whole, including the breeding queen, benefits from the nectar, even though a few individual ants are lost. The Nepenthes benefits from having a regular source of insect prey.
One species of Nepenthes is a true ant-house plant. The Bornean Nepenthes bicalcarata has hollow tendrils connecting pitcher to leaf blade that are inhabited by a species of Camponotus (Clarke and Kitching, 1995). These ants easily run up and down the walls of the pitchers and swim in the digestive fluid. They have even been observed hunting mosquito larvae that live in the pitcher. In an interesting twist on the usual ant-plant relationship, the Camponotus help Nepenthes bicalcarata not by feeding the plant, but by removing some of the prey. When N. bicalcarata pitchers catch large insect prey, the insect begins to decay before the digestion process is complete. This putrefaction can spread to the pitcher and shorten its lifespan. The ants ignore small prey, but laboriously haul larger items up the wall of the pitcher. Once they have dragged the prey up under the peristome (i.e. the lip) of the pitcher, they break it into pieces and eat it. Some of the pieces fall back into the pitcher, but they are now small enough to be completely digested by the plant (Clarke and Kitching, 1995).
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