Plants learned to eat animals at least twelve separate times
Meat-eating plants are not one odd family but a solution evolution reached repeatedly. True carnivory arose independently at least 12 times across five orders of flowering plants. Starved of nitrogen in soggy, sunny bogs, these plants lure, trap and digest insects, and occasionally even small mammals or birds.
Carnivorous plants live on every continent but Antarctica, usually in waterlogged, acidic places where the soil offers little nourishment. Charles Darwin took them seriously first: his 1875 book Insectivorous Plants summarised years of experiments. Today at least 800 species are known, with about three more described each year since 2000, plus over 300 protocarnivorous species that show only some of the traits. A 2020 assessment found roughly a quarter threatened by human activity.
They use five basic trap designs. Pitfall traps drown prey in a rolled leaf full of enzymes or bacteria. Bladderworts create a vacuum and suck victims in. Lobster-pot traps use inward-pointing hairs to herd prey towards digestion. Flypaper traps can be passive, like Triphyophyllum, whose sticky leaves stay still, or active, like sundews, whose tentacles curl by rapidly expanding individual cells rather than dividing them.
Pitchers alone evolved at least six times in unrelated families, a textbook case of convergent evolution. They tempt insects with nectar and flower-like colours, then waxy flakes send visitors sliding into the fluid below. Heliamphora, from rainy South American peaks such as Mount Roraima, has a gap in its leaf seam that drains excess water like a sink overflow. Sarracenia instead grows a lid-like hood, and Sarracenia flava spikes its nectar with coniine, the poison of hemlock, probably to stupefy prey.
Some tricks are almost devious. The cobra plant of California has a balloon-shaped hood dotted with clear patches that look like exits, so ants exhaust themselves against false windows before dropping into the tube. Tropical Nepenthes hang their pitchers from tendrils, and big species such as Nepenthes rajah occasionally catch small mammals and reptiles. Pooled water inside pitchers can even become a tiny habitat for other creatures, called a phytotelma.
Source: Carnivorous plant
