The
Strangler Fig is one of the most prominent trees in the
Neotropical forest. "Strangler Fig" in Spanish is "Matapalo"
( or “tree-killer”), and therefore both the English and the
Spanish have a very descriptive name for this glorious, yet
extremely competitive plant.
photo M. Noonan
Unlike many
trees, the Strangler Fig starts its life already high above
the ground, often nestled inbetween a tree branch and
trunk. From that position, the germinating seed will send
aerial roots to the ground and then send branches to the
canopy. Once the seedling has reached the canopy and has
the opportunity to absorb the highly-coveted sunlight, the
aerial roots continue to multiply, eventually surrounding
the host tree. These roots grow and begin to constrict the
trunk of the host tree, slowly and quietly strangling the
water and nutrient transportation inside the trunk. At the
same time, the Strangler Fig’s branches are intertwining
with the host branches and snatching up sunlight.
Eventually the host tree will die
and will rot inside the surrounding shell of the Strangler
Fig roots. Sometimes, Strangler Figs will fill this
internal tunnel with more roots completing its victory. The
amazing, yet murderous Strangler Fig can become the grandest
tree in the forest because of its cleverly adapted
lifestyle.
Amazing! Don't you
think?!
All forests
have plants, but the richness of the tropical rainforest
sets it apart from most other habitats. With over 13,020
plant species in the tropical rainforests of Costa Rica, the
diversity there is leaps and bounds over temperate forests.
Since there are simply too many to discuss, here we focus
on only a couple of different plants and plant types that
play a significant role in the tropical rainforest
community.
photo M. Noonan
photo M. Noonan
Trees from
the genus Cecropia are relatively easy trees to find in
Neotropical forests. Not only are they somewhat common, but
they have a characteristic open growth form that includes
widely spaced branches and large leaves that only grow at
the ends of branches. For this reason, one of the famous
creatures of the Neotropical forests can be found often in
these trees, the sloth. At one time there was a myth that
sloths only ate Cecropia tree leaves, but it has now been
determined that the relatively leaf-free branches of a
Cecropia tree just provide a better environment for us to
spot sloths.
photos M. Noonan
Considering that the Cecropia trees don’t have the
characteristic thick, light absorbing foliage of most
rainforest trees, how do they do so well? One reason may be
contributed to another creature which can be found in
Cecropia trees, the Azteca ant. At the base of the leaves
there is a small opening which allows these ants to enter
the bamboo like trunk which has large hollow chambers. The
Cecropia trees also produce specialized structures called
trichilia and Mullerian bodies which provide nutrients to
the ants.
So far, the ants have benefited from the Cecropia trees, but
how do the trees benefit from the ants? The Azteca protect
the tree from insects which would feed on the leaves or
wood. If a large disturbance occurs, the Azteca will stream
out from the inside of the tree and try to defend their home
with their tough jaws and caustic chemical secretions.
photos M. Noonan
Now just as the sloth is not dependant on Cecropia
trees, Cecropia are not dependant on the Azteca. But the
symbiotic relationship has improved the tree’s defenses
against predators and has created a home for these valiant
ants.
Epiphytes are simply defined as any plant that grows
attached to another plant or object merely for physical
support. Simplistic epiphytes like lichens, moss, and algae
can be found in temperate forests, but more complex
epiphytes seem to dominate the plant world of a tropical
rainforest. Epiphytes are responsible for much of the plant
diversity in the tropics and include ferns, mosses, cacti,
orchids, and bromeliads. In particular, the orchids and
tank bromeliads have particularly interesting stories to
tell.
There are over 1,400 different species of orchids in the
small Central American nation of Costa Rica. Most are
epiphytic and do not connect to the soil and therefore must
find innovative ways to store and maintain water. Orchids
can develop bulbous stems and thick leaves to hold water.
Also, they have developed an interesting schedule of only
opening the small holes (stomata) in their leaves during the
night when it is less hot and more humid. This adaptation (Crassulacean
acid metabolism) reduces the evaporation rate of the water
and is not used in most plants.
The tank bromeliads have also found an interesting way to
collect, store and maintain water. They have evolved into a
bushel-like form with long, crescent shaped leaves which
funnel towards the center stem. Where all these leaves
converge, up to two gallons of water can be stored.
Interestingly enough, these pools of water are not only
beneficial to the tank bromeliad, but also provide safe,
fish free breeding water for frogs!
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