Agouti in Panama. Click image for more pictures of agouti. (Photo by R. Butler)
SYMBIOTIC RELATIONSHIPS IN THE RAINFOREST
INTERDEPENDENCE AND COMPLEX SYMBIOTIC RELATIONSHIPS
Interdependence—whereby all species are to some extent
be dependent on one another—
is a key characteristic of the rainforest ecosystem. Biological interdependency
takes many forms in the forest, from species relying on other species
for pollination and seed dispersal to predator-prey relationships to
Agouti in forest clearing
Brazil nut pods
Brazil nut tree
relationships have been developing for millions of years and form the
basis for the ecosystem. Each species that disappears from the ecosystem
may weaken the survival chances of another, while the loss of a keystone species
—an organism that links many other species together, much like the keystone
of an arch—could cause a significant disruption in the
functioning of the entire system.
For example, Brazil nut trees (Bertholletia excelsa
) are dependent
on several animal species for their survival. These large canopy trees
found in the Amazon rainforest rely on
the agouti, a ground-dwelling rodent, for a key part of their life cycle.
The agouti is the only animal with teeth strong enough to open their
grapefruit-sized seed pods. While the agouti eats some of the Brazil
nut's seeds, it also scatters the seeds across the forest by burying
caches far away from the parent tree. These seeds then germinate and
form the next generation of trees. For pollination, Brazil nut trees
are dependent on Euglossine orchid bees. Without these large-bodied
bees, Brazil nut reproduction is not possible. For this reason, there
has been little success growing Brazil nut trees in plantations—they only appear to grow in primary rainforest.
Life in the rainforests is competitive and countless species have developed
complex symbiotic relationships with other species in order to survive.
A symbiotic relationship is a relationship where both participant species
benefit mutually. Symbiotic relationships appear to be the rule and
not the exception in the rainforest. For example, ants have symbiotic
relationships with countless rainforest species including plants, fungi,
and other insects. One symbiotic relationship exists between ants and
caterpillars. Certain caterpillar species produce sweet chemicals from
"dew patches" on their backs, upon which a certain ant species will feed. In return, the ants vigorously protect the
caterpillar and have even been observed carrying the caterpillar to
the nest at night for safety. This relationship appears to be species
specific in that only one caterpillar species will cater to a particular
All tropical rainforests are characterized by tremendous biological
diversity. Section 3
concentrates on the diversity
of the tropical rainforest.
- What is a symbiotic relationship?
- What is a keystone species?
- Why are agoutis important in the rainforest ecosystem?
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