The New Neotropical Companion

concentration in older plants. This characteristic appears

to be generally true for most tropical plants. Tannin

levels are lower in plants grown in shade, indicating

that tannin production may be metabolically costly,

requiring full sunlight. In field experiments, low- tannin

plants experienced twice the level of herbivory as those

with high tannin levels. However, leaf production was

inversely correlated with tannin levels. The more leaves

on the tree, the lower the tannin per leaf, indicating that

tannin production, though perhaps protective, is likely

costly to the plant. Trees like Cecropia, experiencing

intense competition for light, may have to limit tannin

protection in favor of rapid growth, a situation termed

an evolutionary trade- off.

The role of phenolic compounds and tannins as

anti- herbivore adaptations is unclear. Some insects

have evolved enzymes that detoxify specific defense

compounds. Leaf- cutter ants (chapter 10) are apparently

undeterred by phenolic compounds, but of course they

do not actually eat leaves. Instead they “feed” the leaves to

A Very Toxic Toad: Do Not Lick This Animal

The Cane Toad (Rhinella marina, formerly Bufo marinus;

plate 11- 31), is a common resident on the forest floor

throughout the Neotropics. It has been introduced in

many places outside of its normal range, including south

Florida, much of the Caribbean and as far away as Fiji and

Australia, where it has become a serious pest species.

When a Cane Toad reaches adulthood, it is somewhere

between the size of a baseball and a softball. Even though

its appearance is relatively cryptic, its large size makes

it hard to miss. Once discovered, it does not hop very

quickly. So it would appear vulnerable, a big fat toad, and

a darned slow one. But it is well protected, and predators

avoid it. Cane Toad skin contains a milky bufotoxin (toad

toxin), secreted from the animal’s prominent parotoid

glands, the “warts” that appear on its back and behind the

head. This toxin, a kind of alkaloid called bufotenin, has

been shown to produce hallucinations in humans— some

of whom have apparently been known to lick toads just to

have this occur. Should an animal ingest the toad or even

just bite it, it risks illness and perhaps death. This is one

dangerous toad.

Wax- tail Hopper: Strange but True

Meet the Wax- tail Hopper (Pterodictya reticularis; plate

11- 30), an insect in the family Fulgoridae. At first glance it

appears to be a disheveled katydid. It is not a true katydid,

however, but it is relatively closely related to both the

katydids and the treehoppers. This odd insect feeds on

certain plant juices and metabolizes them in such a way

that it creates its own thick wax. This wax composes the

long white plumes that stream behind the abdomen.

Apparently the wax functions in two ways: First, it coats

the species’ eggs, helping protect them from parasites

and from drying out. Second, it protects the adult insect

by making it unpalatable to potential predators. At least

that is our best guess for the moment. In any case, it is just

another remarkable insect of the Neotropics for you to

strive to observe.

Plate 11- 31. This adult Cane Toad is well protected by its

chemical defenses. The large parotoid glands posterior

to the head, shown clearly in this image, secrete the toxin

bufotenin. Photo by Dennis Paulson.

Plate 11- 30. The Wax- tail Hopper is easy to see but may not

be so easy to eat. Photo by Dennis Paulson.

chapter 11 evolutionary arms races: more coevolution, more complexity 189