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THE STRANGLER FIG
Perhaps the most famous hemiepiphyte is the towering strangler fig tree which starts life as
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Strangler Fig, Brazil 1999
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a tiny seed in the canopy. The roots grow down to the forest floor where they take root and begin to take nutrients
from the soil. Gradually the roots wrap around the host tree, widen, and slowly form a lattice-work that surrounds
the host's trunk. The fig's crown grows foliage which soon overshadows the tree. Eventually, the host tree dies
leaving the fig with a hollow trunk—which is easily climbed thanks to the many openings in the trunk. Figs are
often the only tree species remaining after forest clearing, since their knotted and twisted wood is shunned by
loggers.
Almost ironically, this agent of death provides an important niche and food source to many rainforest creatures.
Its hollow trunk, with an abundance of nooks and crannies, provides an important home to thousands of invertebrates,
rodents, bats, reptiles, amphibians, and birds. Many other species are attracted to the fig tree because of its
production of large amounts of good-tasting fig fruits. These fruits are packed with seeds, many of which are not
destroyed when they are consumed, and are passed out in the dung of animals far from the mother tree. In many forests
the fig tree is considered a keystone species since during parts of the year it is virtually the only tree producing
fruit. During these lean times, many primates and birds feed almost exclusively on fig fruit.
The fig tree is a successful forest species, with some 900 species of Ficus distributed around the world thanks
to its excellent means of dispersal (abundant, good-tasting fruit). But its reproduction is limited by a mutual
evolutionary pollination relationship with the gall wasp. The fruits (figs) of the ficus tree grow in clusters
on short stems that spring directly from the tree trunk. Each fig has a tiny hole, an entrance just large enough
for the female gall wasp, full of eggs, to enter. As she squeezes through the entrance, she loses both her wings
and is unable to leave after entering. She deposits the pollen that she has carried and lays her eggs in the stigma
of the flowers within the fig seed. Then she dies, and the hole in the fig wall closes. After a few days, the young
male wasps—which develop faster than females—hatch and chew open the eggs of the females and mate with them. The
males then chew a hole in the wall of the fig fruit and proceed to die. On the way out, the winged females are
tagged with pollen. The female wasps, now full of eggs, can only make one flight with their delicate wings. In
that one flight, the female must not only find the right species of fig, but one in the right stage of development.
If she fails, she will not have the strength to make another flight. If she happens upon the correct species with
the right characteristics, she will reenact the process of her mother, ensuring another generation of wasps, and
hence another generation of Ficus.
Continued: Rainforest Overstory
This article was written by Rhett A. Butler [bibliographic citation for this page] and was last updated on the most recent date listed in the column on the right side.
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