Plants and animals have developed mutualistic relationships with each other in order to survive, or at the least in order to be more efficient. Previously we looked at the corpse plant, and how it evolved to emit the odor of rotting meat in order to attract carnivorous insects to use as pollinators. If you have not read it, you can find it here. Today, I want to look at how one particular pitcher plant has evolved to gain nutrients by digesting bat feces.
What is a Pitcher Plant?
A pitcher plant is a carnivorous plant that has evolved to capture its pray using a type of pitfall trap, making it one of the more unique plants. Essentially, the leaves develop to form a hollow pitcher that contains water or nectar that drowns the insects lured in by pigmentation and nectar. Once trapped, the insects are dissolved either by bacteria or enzymes that are produced by the plant, and absorbed. Some pitcher plants have a mutualistic relationship with insect larvae and even tree shrews, the former feeding on trapped insects and the latter feeding on nectar, both of which defecate into the pitcher. Sounds gross, but the feces left in the pitcher is actually good for the plant, supplying it with easy to get nitrogen. Today I want to talk about a specific species that has developed a similar relationship, Nepenthes hemsleyana.
N. hemsleyana has developed a mutualistic relationship with the Hardwicke’s woolly bat, very similar to the previously mentioned relationships. The plant has adapted to provide a roost for the woolly bat, in return for the privilege of feasting on the bats feces. In order to more effectively do this, the plant produces less nectar and contains less liquid in the bottom of the ‘pitcher’. One study found that N. hemsleyana was able to get 95% of its nitrogen demand from the feces dropped by the woolly bat. By not putting energy into producing a ton of nectar or trying to attract insects, the plant is able to put more energy into the development of leaves and other structural components.
The Woolly Bat
In addition to the lower production of nectar, the plant has developed a parabolic rear side, providing more volume and a better roost for the bat than other plants. Interestingly, the bats that roost within this plant have the highest vocalizations of any known bat species, and some scientists have hypothesized that this trait allows the bats to better find these plants within the foliage (because of the parabolic rear wall). While I’m at it, I also want to throw in that bats that roost in N. hemsleyana plants have a higher body condition and fewer parasites than bats that roost in other species of pitcher plants.
I guess that the take away here is that plants are incredibly more complicated and dynamic than meets the eye. I mean, I think everyone has heard about venus flytraps (that is awesome in itself), but not many people know about plants actually digesting feces. If there is any sort of ecological niche in this world that can be filled, rest assured that something has evolved to fill it. Other plants taking all of the pollinating bees away? OK, I will just smell like rotting flesh and attract flies to pollinate for me. Neighboring plants taking up too much nitrogen? No problem, I will just turn into a bat house. The ability that plants have to just survive is incredible, and there are so many that have yet to be discovered, hidden deep in the rainforest or maybe even in some dark cave somewhere. The unfortunate thing is that there are species out there that we have not discovered yet that are already extinct, due to us. But that’s a topic for another day.
Schöner, C. R., M. G. Schöner, T. U. Grafe, C. M. Clarke, L. Dombrowski, M. C. Tan, and G. Kerth. 2017. Ecological outsourcing: a pitcher plant benefits from transferring pre-digestion of prey to a bat mutualist. Journal of Ecology 105: 400–411.