Pitcher plants go batty, as described in reports in Biology Letters 26 January 2011, doi: 10.1098/rsbl.2010.1141 and ScienceNOW 25 January 2011 and BBC Earth News 26 January 2011. Pitcher plants are so named because they have elongated goblet shaped leaves that attract insects with aroma and visual patterns and then trap them in fluid in the base of the pitcher. Because the plants get nutrients from digested insects they are able to grow in acid bogs that would not otherwise provide enough nutrients for the plants. When studying pitcher plants in Borneo in the 1980s, ecologist Jonathan Moran noticed an unusual pitcher plant with long narrow pitchers that lacked aroma and patterns and caught fewer insects than other pitcher plants, but still grew well in the nutrient poor soils.
A group of biologists led by Ulmar Grafe of the University Brunei Darussalam have now followed up Moran’s observation and discovered that the plant is used as roosting place by bats, and the plants feed on bat droppings. The bats wedge themselves in the narrow mid section of the pitcher above the liquid in the bottom of the trap. Mother bats with young will also settle down in the pitchers and suckle their young. Following chemical analysis of the leaves the researchers concluded the plants get about one third of their nutrients from bat droppings and urine. This plant is not the first pitcher plant shown to feed on animal droppings. Recently scientists discovered the giant montane pitcher plant attracts tree shrews with nectar secreted on the lid of the pitchers. While they are feeding on the nectar their backsides protrude over the pitcher. The ScienceNOW article reports: “Indeed, pitcher plants are turning out to be less carnivorous than biologists once believed—another species digests leaf litter. Moran predicts that the plants will yield more surprises ‘that we can’t even dream of yet’.”
Editorial Comment: We agree with Moran – when pitcher plants are fully investigated we predict there will be more surprises – but why would we? Recent research has shown they have far more complex interactions with other living things than just a simple predator and prey relationship. A recent review article in the Annals of Botany, entitled Traps of carnivorous pitcher plants as a habitat: composition of the fluid, biodiversity and mutualistic activities gives the following background information: “Carnivorous pitcher plants (CPPs) use cone-shaped leaves to trap animals for nutrient supply but are not able to kill all intruders of their traps. Numerous species, ranging from bacteria to vertebrates, survive and propagate in the otherwise deadly traps. (Ann Bot doi: 10.1093/aob/mcq238) The article also points out that not all pitcher plant fluid is toxic or contains sufficient digestive enzymes to kill all the insects that land in it, and the organisms that live in the pitchers dispose of the prey providing both them and the plant with nutrients.
The plant that digests leaf litter is Nepenthes ampullaria and it lives in rainforests where there is plenty of leaf litter to fall on it and provide it with nutrients. Pitcher plants living in more open settings can’t get enough nutrients from leaf litter. Our prediction is based on the fact that God made everything very good with no death as Genesis reads, so the original function of pitcher plants would not have been to eat animals no matter where they grew. These new research findings give this more support to the thesis that in a very good world “carnivorous” plants recycled leaf litter and animal droppings – a very good function. (Ref. ecology, botany, food chain, prediction)
Evidence News 2 March 2011