Article by: Adam Manning
Edited by: Harry T. Jones and J. D. Dixon
Carnivorous plants are some of the most impressive plants that we have on this planet, encompassing at least 583 species across 20 genera, such as the Low’s pitcher-plant (Nepenthes lowii) and the Venus flytrap (Dionaea muscipula). To their insect prey, they are some of the most vicious predators on Earth, silently luring in their prey, then trapping and digesting them. However, there is a scarce number of carnivorous plants in the fossil record. So, what can we learn about the evolution of these most unlikely of predators?
Macrofossils of carnivorous plants are very rare, and many of those that have been reported have later been questioned. For example, Archaeamphora longicervia from the Early Cretaceous of China, a time when angiosperms (flowering plants) had just started to evolve and diversify, was thought to be a carnivorous pitcher plant when first discovered. When later re-investigated, scientists doubted that this was the case, instead suggesting it to be a previously reported gymnosperm with galls (growths) caused by insects. Similarly, Palaeoaldrovanda splendens from the Late Cretaceous of the Czech Republic was originally described as seeds having come from carnivorous plants, but when looked at again by another group, they reported they were in fact the eggs of insects.
One of the only certain examples of fossil carnivorous plants comes from Eocene Baltic amber. Leaves trapped in the amber show in exquisite detail the morphology of the plant, and bear a striking resemblance to the Roridula carnivorous plants found in South Africa today. It is hypothesised that, like its modern-day relatives, this fossil plant would have trapped insects using sticky, glue-like resin and ‘tentacles’ that restrict movement. Other insects would then arrive and feed on the imprisoned ones and the plant would absorb their excrement as nutrients.
Carnivorous plants are a fascinating topic, having developed across many genera, but they beg the question, why develop carnivorous behaviours at all? It is often assumed that plants get all their nutrients through photosynthesis and uptake from their roots, but sometimes the environment does not provide enough of those nutrients to sustain the plant. Carnivorous plants get around this problem by evolving ways to get nutrients from other sources, namely their insect prey. This allows them to survive in tougher environments and compete less with neighbouring plants for the same resources.
Whilst there are still many unanswered questions surrounding their origins, carnivorous plants are one of the most impressive forms of flora we have on our planet, and hopefully future discoveries will shed further light on the evolution of these brilliant, yet terrifying types of vegetation.
Image References
[1] A) Low’s pitcher plant, Nepenthes lowii; B) Venus flytrap, Dionaea muscipula; and C) Roridula gorgonias. Images by Jeremiah Harris; CC0 Public Domain; and Givnish (2015) respectively.
[2] Carnivorous leaves preserved in amber, dating back to the Eocene, with close-ups on the ‘tentacles’ that would have trapped prey. Taken from Sadowiski et al. (2014).
Information References and Further Sources
[1] Givnish, T. J. (2015). ‘New evidence on the origin of carnivorous plants’, PNAS, 112 (1), pp. 10-11. Accessed 17th October 2020. Click Here.
[2] Heřmanová, Z., and Kvaček, J. (2010). ‘Late Cretaceous Palaeoaldrovanda, not seeds of a carnivorous plant, but eggs of an insect’, Journal of the National Museum (Prague), 179 (9), pp. 105-118. Accessed 17th October 2020. Click Here.
[3] Li, H. (2005). ‘Early Cretaceous sarraceniacean-like pitcher plants from China’, Acta Botanica Gallica Botany Letters,152 (2), pp. 227-234. Accessed 17th October 2020. Click Here.
[4] Sadowski, E-M., Seyfullah, L. J., Sadowski, F., Fleischmann, A., Behling, H., and Schmidt, A. R. (2014). ‘Carnivorous leaves from Baltic amber’, PNAS, 112 (1), pp. 190-195. Accessed 17th October 2020. Click Here.
[5] Wong, W. O., Dilcher, D. L., Labandeira, C. C., Sun, G., and Fleischmann, A. (2015). ‘Early Cretaceous Archaeamphora is not a carnivorous angiosperm’, Frontiers in Plant Science, 6, pp. 326. Accessed 17th October 2020. Click Here.