Non-insect-eating insectivorous plant

Probably the one thing one could guess about an insectivorous plant is that it ‘eats’ insects. Take for example one of the most iconic entomophagous botanics of them all, the Venus fly-trap (Dionaea muscipula). The clue’s clearly there in the name; it traps – and consumes – flies, i.e. insects. Yes, it does. But, first, there’s more than just one type of insect [in fact there are an estimated 5.5 million insect species (which includes 1.5 million beetle spp.)], and, second, the plant is actually quite a fussy eater – not all insects are treated equally as would-be food.

Dionaea muscipula flower
Dionaea muscipula flower. Image: Calyponte / Wikipedia.

That’s just as well, because, as a flowering plant that doesn’t use wind or water to transfer pollen from one flower to another, it relies on insects to perform that important service. It would therefore not be doing itself any favours if it snacked on those reproductively-helpful creatures – at least not until after they’d provided this sexual service. But, just because that behaviour would seem eminently sensible – for intelligent organisms such as human – is that what happens in nature? That is to say, is this what the plant does?

Short answer: Yes, according to the study of Elsa Youngsteadt et al.. Longer answer: They found that certain bee and beetle species are the most frequent flower visitors of D. muscipula, and since they carried pollen of that species, presumably therefore assisted in its pollination. Prey taxa were also invertebrates; spiders, beetles and ants were the most commonly caught. Although beetles both pollinate and feed the Venus fly-trap, few such species were shared between traps and flowers. Or, as the study’s authors’ phrase it, niche overlap for these potentially competing structures was near-zero.

Now whether this is accident or design on the part of the plant remains to be seen, but – as the authors also identify – the spatial separation of aerial flowers and near-ground level traps is likely to play a part in this behaviour. Nevertheless, it seems that the old adage “don’t bite the hand that feeds you” appears to apply as much to Dionaea as it does to humankind. Importantly, this sort of insight won’t appear in the recent review of carnivorous plants’ physiology, ecology, and evolution by Aaron Ellison and Lubomir Adamec.* Which serves to demonstrate that research on a given group of plants doesn’t stop just because a book’s been published on them; people continue to investigate and discover new facts about these curious plants. More power to the insectophagophytophiles.

* For more carnivorous plant information, why not look at the ‘blog of the book’ by Aaron Ellison? And for more specifically about the Venus flytrap, check out Rainer Hedrich and Erwin Neher’s review, or Sami Lehtinen’s more mathematical approach.

Reference List

Stork, N. E. (2018). How Many Species of Insects and Other Terrestrial Arthropods Are There on Earth? Annual Review of Entomology, 63(1), 31–45. https://doi.org/10.1146/annurev-ento-020117-043348

Youngsteadt, E., Irwin, R. E., Fowler, A., Bertone, M. A., Giacomini, S. J., Kunz, M., … Sorenson, C. E. (2018). Venus Flytrap Rarely Traps Its Pollinators. The American Naturalist, 191(4), 539–546. https://doi.org/10.1086/696124

Hedrich, R., & Neher, E. (2018). Venus Flytrap: How an Excitable, Carnivorous Plant Works. Trends in Plant Science, 23(3), 220–234. https://doi.org/10.1016/j.tplants.2017.12.004

Lehtinen, S. (2018). Understanding the Venus flytrap through mathematical modelling. Journal of Theoretical Biology, 444, 1–10. https://doi.org/10.1016/j.jtbi.2018.02.003