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Science Frontiers ONLINE No. 97: Jan-Feb 1995 |
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Fruit Dupe
Hakea trifurcata is a forlorn-looking shrub growing on rocky terrain in Western Australia, where it reaches a height of 2 meters. The fruits of this plant are enjoyed by the white-tailed black cockatoo -- if it can identify them ! Hakea trifurcata, you see, grows fruit that looks like its leaves, and this is very frustrating to the white-tailed black cockatoo:
"This shrub according to plant ecologist Byron Lamont of Curtin University of Technology in Perth, exhibits the first known case of self-mimicry in a plant: to avoid losing valuable seeds to predators, it disguises some of its leaves as fruits. Young plants produce only the long, needle-shaped leaves. But mature five-year-old shrubs also grow broad leaves that cluster around the slightly smaller, almost identical-looking green seed-filled fruits."
When offered branches stripped of real leaves and bearing just fruits, the cockatoos quickly demolished them. Normal branches bearing both leaves and fruit were attacked at first -- especially the larger leaves. But when the cockatoos found themselves duped a large proportion of the time, they gave up in obvious frustration.
(Anonymous; "Fruit Dupes," Discover, 15:16, August 1994.)
Comment. An even more amazing case of plant mimicry occurs among Passiflora species, which craft precise copies of the eggs of a butterfly, whose larvae decimate these plants. The butterflies see the fake eggs and go look for places to lay their eggs where there is less competition. (See SF#16)