Cunning carnivorous plants catch more prey by letting some go
Ranitomeya imitator poison dart frog from Peru. (Photo by R. Butler)
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plants grow year round in the tropical rainforest, they must continuously
defend themselves against an array of predators. Over
the course of millions of years of evolution, plants have developed
a variety of mechanical and biochemical defenses. Mechanical defenses
like thorns, spines, and stinging hairs appear to be secondary
protection to chemical compounds produced by plants, like alkaloids,
tannins, and toxic amino acids.
In response, like biochemical
warfare, herbivorous insects have adapted to these compounds and insects
that eat these plants are able to detoxify the chemicals. The result
is that any given insect species has adapted to feed on only a limited
number of plants species, while leaving these individual plant species
toxic to most other insects.
Through the rigorous process of natural selection, plant species have been perfecting various chemical defenses to ensure survival over millions of years of evolution, and are proving to be an increasingly valuable reservoir of compounds and extracts of substantial medicinal merit. These plants have synthesized compounds to protect against parasites, infections and herbivores, creating acutely powerful chemical templates with which pharmacologists can create new drugs.
Interesting associations have developed between plants and insects like
that of the Heliconid butterflies and passion flower vines of the genus
Passiflora. Passion flower vines contain cyanide-based compounds for
protection against predators. However, Heliconid caterpillars have adapted
to these compounds and are able to eat the vine's leaves. Therefore,
Heliconid butterflies lay their eggs directly on the passion flower
vine, so the larvae will have easy access to their food source. Passion
flowers have counter-adapted to the behavior by developing mechanisms
to discourage Heliconid butterflies from laying eggs on their leaves.
Some Passiflora have evolved structures (actually nectaries) that create
housing and produce excess nectar for ants. In return, the ants attack
anything, including butterfly eggs, that
intrudes on their host. One-
upping their predators, some Passiflora have structures that mimic the
eggs of Heliconid butterflies. Since a Heliconid butterfly will not
lay its eggs on leaves that already have (or appear to have) these eggs,
she will move on to another plant. In this manner, Passiflora deter
Heliconid butterflies without devoting any resources to the production
of nectar for a guard of ants, a technique of protection adopted by
many other plants as their primary means of defense. Heliconid caterpillars
that develop into butterflies retain the cyanide they consumed as larvae,
making the adult butterflies highly unpalatable to predators. The distinct
pattern and color of Heliconid butterflies acts as a sort of warning
for predators of its toxic composition. When a predator eats one of
these butterflies and experiences a foul taste and other ill effects,
it learns to associate the colors and patterns of the prey with the
bad experience. The next time the predator recognizes the color pattern,
it is likely to avoid that potential prey.
This use of warning coloration to advertise bad taste or toxic composition
is employed frequently in the rainforest by a variety of animals. The
toxic chemicals almost never kill the predator, but cause some irritation
to violent sickness. There would be no use if the poison killed the
predator, since the next predator that came along would make the same
mistake and eat the prey. By making the predator ill, the toxin causes
the predator to recognize and avoid the unpalatable prey and similar-looking
species known as mimics.
- Why are some rainforest animals (especially insects and frogs) brightly colored?
- How do plants protect themselves from predators?
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(02/25/2015) Pitcher plants (Nepenthes species) have long captivated our fascination. Typically growing in acidic and nutrient-poor soils, they have developed the ability to eat insects and other small prey to supplement their diets. Nepenthes grow modified leaf structures which form a saucer cup with a slippery rim lined with visual or edible bait. When an insect approaches to investigate the reward, they slip off the rim and into the cup which is usually filled with a viscoelastic fluid. Unable to escape, the prey is slowly digested and absorbed by the plant.
Facebook, Twitter to carry 24 hours of live rainforest animal sightings on Monday
(05/29/2014) Next week, the rainforests of Southeast Asia are going live. On June 2nd, 11 organizations in the region will be posting lives video, photos, and wildlife sightings over 24 hours on Facebook and Twitter (see #rainforestlive). Dubbed Rainforest: Live, the initiative hopes to raise awareness of quickly vanishing ecosystems and species.
Mother of God: meet the 26 year old Indiana Jones of the Amazon, Paul Rosolie
(03/17/2014) Not yet 30, Paul Rosolie has already lived a life that most would only dare dream of—or have nightmares over, depending on one's constitution. With the Western Amazon as his panorama, Rosolie has faced off jaguars, wrestled anacondas, explored a floating forest, mentored with indigenous people, been stricken by tropical disease, traveled with poachers, and hand-reared a baby anteater. It's no wonder that at the ripe age of 26, Rosolie was already written a memoir: Mother of God.