Pitcher plant port-a-potties

The last ecology post was about typical carnivorous plants, but now it’s time to talk about some atypical pitcher plants. Imagine the side of a mountain in Borneo. As you hike to higher elevations, it gets colder and there are fewer insects. When pitcher plants at these high elevations exude a sugary fluid as an insect lure, few, if any, insects come, and even fewer fall into the trap. However, this is a harsh environment, and everything that lives here is looking for any advantage that it can get. Fruit-eating shrews are attracted to the floral and fruity scents coming from the pitchers, and sometimes come to the pitcher plants to lick the sweet, fluid insect lure. If they spend some time near the pitcher plants, they may poop, providing needed fertilizer to the pitcher plants. The pitcher plants that are the most attractive to shrews grow better and produce more seeds. Over time, small differences in pitchers that lead to more efficient fertilization grow more frequent in the plant population. That, my friends, is how the pitcher plant port-a-potty came to be.

This is one of the great and beautiful oddities of nature: a pitcher plant shaped like a shrew toilet, which provides a convenient place for screws to squat while they lick a white, buttery exudate secreted from glands on the underside of a leaf (see video here). No one knows if the exudate has laxative properties, but given the diversity of potential plant secondary compounds found in nature I would not be at all surprised if the plants increase their odds of receiving a “donation” when a shrew stops by.

Fun Fact: Shrews mark plants that they have drained, possibly to mark territory or possibly to show which plants they have already drained so they don’t waste time re-visiting empty plants until there is time for leaf glands to exude more shrew-bait. The shrews accomplish this marking by rubbing their genitals all over the pitcher, which is an order of magnitude more disgusting than licking things to claim them as your own.

You may think that these weirdo plants would be the only ones trying to corner the poop market, but then you’d be wrong. Another group of pitcher plants in Borneo create safe, daytime roosting sites for woolly bats. The relationship is very specialized. The pitchers have reflector leaves that bounce back the bats’ echolocation calls, allowing the bats to easily find pitchers in dense foliage. One or two bats can fit in at once, and the morphology of the pitcher is such that the bats can’t fall into the low level of digestive liquid at the narrow bottom of the pitcher. The plants benefit from bat poo and pee, receiving about 34% of their nitrogen from these sources.

Pitcher plant port-a-potties: brought to you by adaptation via natural selection.

Screen Shot 2017-06-25 at 11.38.24 AM
Figure from Grafe et al. 2011.

 

 

Featured image credit: Ch’ien Lee

 

Resources

Bryner, J. 2009. Pitcher plant doubles as a toilet. Live Science. Available at: https://www.livescience.com/9666-pitcher-plant-doubles-toilet.html

Clarke, C. M., Bauer, U., Ch’ien, C. L., Tuen, A. A., Rembold, K., & Moran, J. A. 2009. Tree shrew lavatories: a novel nitrogen sequestration strategy in a tropical pitcher plant. Biology Letters, 5(5), 632-635.

Clarke, C., Moran, J. A., & Chin, L. 2010. Mutualism between tree shrews and pitcher plants: perspectives and avenues for future research. Plant signaling & behavior, 5(10), 1187-1189.

Grafe, T. U., Schöner, C. R., Kerth, G., Junaidi, A., & Schöner, M. G. 2011. A novel resource–service mutualism between bats and pitcher plants. Biology Letters, 7(3), 436-439.

Pappas, S. 2015. How hungry pitcher plants get the poop they need. Live Science. Available at: https://www.livescience.com/51501-pitcher-plants-lure-pooping-bats.html

Schöner, M. G., Schöner, C. R., Simon, R., Grafe, T. U., Puechmaille, S. J., Ji, L. L., & Kerth, G. 2015. Bats are acoustically attracted to mutualistic carnivorous plants. Current Biology, 25(14), 1911-1916.

Wells, K., Lakim, M. B., Schulz, S., & Ayasse, M. 2011. Pitchers of Nepenthes rajah collect faecal droppings from both diurnal and nocturnal small mammals and emit fruity odour. Journal of Tropical Ecology, 27(04), 347-353.

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