Listen to Episode 105 on PodBean, YouTube, Spotify, or wherever podcasts are provided!
Most plants are content to sit still and take in sunlight and soil nutrients, but when conditions are tough, some plants get hungry! The habit of devouring animal prey has evolved in plants numerous times. In this episode, we discuss the varied strategies and evolutionary history of Carnivorous Plants.
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Plants With Appetites
Most plants get their energy from photosynthesis, and they also need to maintain their bodies with nutrients like nitrogen, phosphorus, and potassium, which they typically get from the soil. But when the local soil is poor in nutrients, some plants turn to another source: animals!
Image: Beatriz Moisset / CC BY-SA 4.0
Carnivorous plants include a variety of species that have developed strategies to attract, trap, kill, digest, and absorb nutrients from small animals, usually insects and other invertebrates. Pitfall traps, like those seen in pitcher plants, are leaves folded into slippery pools full of digestive juices; flypaper traps are leaves covered in sticky goo, like those of sundews; snap traps – think Venus flytraps – are hinged leaves that snap shut over prey; the bladder traps of bladderworts suck prey into a digestive bladder; and lobster-pot traps are inescapable corkscrew-shaped channels.
Right: Bladderwort. Image: Veledan / Public Domain
All in all, carnivory is thought to have evolved independently nine times in five different orders of angiosperms, and carnivorous plants are found on every continent except Antarctica.
Shadowy Past
Not much is known about the evolutionary history of carnivorous plants. Molecular (DNA) studies suggest that carnivory in plants first evolved as far back as the Late Cretaceous, but there’s plenty of uncertainty. The fossil record isn’t much help, either: carnivorous plants tend to be soft-bodied plants (unlike, say, trees) that live in places with low fossilization potential, making them rare in the fossil record. And on top of that, most of the carnivorous attributes of these plants are found on their leaves, which aren’t fossilized often and which aren’t commonly used to identify fossil plants.
Fossil carnivorous plants are almost unheard of. There have been a few suspected carnivorous plant fossils from the Cretaceous Period that have turned out to probably not be carnivorous at all, such as Archaeamphora and Palaeoaldrovonda. More promising are pollen and seeds from relatives of living carnivorous plants from back in the Paleogene. The oldest definitive example of carnivory in plants are some flypaper-trap leaves preserved in Eocene Baltic amber.
have been found fossilized in amber from the Eocene.
Image: NoahElhardt / CC BY-SA 3.0
Learn More
Carnivorous and Insectivorous Plants, Botanical Society of America
International Carnivorous Plants Society
Givnish 2015. New evidence on the origin of carnivorous plants (technical)
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If you enjoyed this topic and want more like it, check out these related episodes:
- Episode 57 – The Evolution of Flowering Plants (Angiosperms)
- Episode 38 – Grass
- Episode 73 – Trees
- Episode 70 – Convergent Evolution
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The Common Descent Podcast 
I loved your episode on carnivorous plants, but I was a little surprised that you overlooked these two examples:
Carnivorous seeds:
Shepherd’s purse (Capsella bursa-pastoris) is a small plant in the mustard family. According to findings presented in Nature, nematodes are attracted to the seeds of this plant, get stuck in the sticky mucilage coating the seeds, and eventually die, fertilizing the soil around the plant. The researchers found that plants germinated in soil containing nematodes did better than those germinated in soil without nematodes, especially if the soil was nutrient-deficient.
The sheep-eating plant:
Puya chilensis is a tree-like bromeliad that grows in the Andes. P. chilensis has very sharp, outwardly-pointing spines. Sheep sometimes get their wool entangled by the spines of these plants and, if not rescued, they may die and decompose at the base of the plant, which is, of course, a great boon for the plant. For this reason, P. chilensis is sometimes called the “sheep-eating plant”.
Awesome podcast!
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Very cool plants! Alas, we can only fit so much in one discussion. Guess we’ll just have to talk more about them in the future!
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Carnivorous Plants Podcast was epic. You folks ate a hoot. Loved your guest. Keep up the great work.
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Thanks!
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After carnivorous plants, perhaps an episode on parasitic plants?
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Still catching up… I often think of topics I’d like to request, but have left it for now because a bunch of the things have probably been covered.
Carnivorous Plants is totally one of those topics and I cheered audibly when it came up. Now I really hope you do a Spook-E for Audrey II.
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If you haven’t already, you should definitely check out Spook-E 2021
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