How Plants Evolved into Carnivores

Feb 6, 2017

By Ewen Callaway

Any insect unlucky enough to land on the mouth-like leaves of an Australian pitcher plant will meet a grisly end. The plant’s prey is drawn into a vessel-like ‘pitcher’ organ where a specialized cocktail of enzymes digests the victim.

Now, by studying the pitcher plant’s genome—and comparing its insect-eating fluids to those of other carnivorous plants—researchers have found that meat-eating plants the world over have hit on the same deadly molecular recipe, even though they are separated by millions of years of evolution.

“We’re really looking at a classic case of convergent evolution,” says Victor Albert, a plant-genome scientist at the University of Buffalo, New York, who co-led the study, published in Nature Ecology and Evolution on February 6.

Carnivorous plants occur across the flowering-plant family tree. The Australian pitcher plant (Cephalotus follicularis)—native to a sliver of coastline in Southwest Australia—is closer kin to the starfruit (Averrhoa carambola) than to other species of pitcher plants found in the Americas and southeast Asia. This suggests that carnivory has evolved repeatedly in plants, probably to cope with the nutrient-scarce soils in which they grow, Albert says. “What they’re trying to do is capture nitrogen and phosphorus from their prey.”

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One comment on “How Plants Evolved into Carnivores”

  • @OP – Gaining the ability to eat an insect is of little use if a plant cannot first entrap one, and here evolution has come up with more diverse solutions,
    Albert notes. Venus fly-traps ensnare their prey, whereas bladderworts immobilize their victims using tiny suction cups.
    In his 1875 book Insectivorous Plants, Charles Darwin included detailed drawings of the tentacles that sundews use to pin insects to their leaves.
    “It’s no wonder Darwin wrote an entire book on carnivorous plants,” Albert says.

    The co-evolution of mechanical systems is also interesting.

    Flowering plants have various moving parts.
    Some flowers open during the day and close at night.
    Others (usually bat or moth pollinated) in hot dry climates, open at night and close during the day to conserve moisture.
    Some flowers even entrap insects and release them later, to ensure they are well covered with pollen, after fertilising that individual flower and before moving on to the next plant.

    It is not only petals which move.
    Many broad-leaved trees have leaves which track the sun as the angles change during the day.
    Some climbing plants also have stems or tendrils which entwine around supports.

    Some carnivorous plants such as Venus Fly-traps, Sundews and Butterworts, use movement to entrap insects.
    The Sundews and Butterworts combine this with sticky adhesives to hold the insect in place while the trap closes slowly, whereas the fly-trap uses speed and the force from the torque in its spring loaded mechanism, to physically over-power its victims.
    The Pitchers go the opposite way, with a static trap, waxy lubricant, and downward-facing hairs to ensure a one-way slide into the lethal digestive swimming pools inside their traps.

    Many people are unaware of plant movement, because apart from a few exceptions such as the Venus Fly-trap and exploding seed-pods, plant movement is usually slow.

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