The fig enigma remains unsolved. The possibility
that pathogens reduce germination and kill seedlings
near adult congeners should be tested. Work in Borneo
indicated that ants take many fig seeds, particularly
from fig trees (Laman 1994). Future studies should
include tracking individual fig seedlings planted in
conspecific soil cavities for a period of time that
would allow observation of possible pathogen attack
or fusion with the host. DNA fingerprinting studies
would also be of interest.MUCUNA URENS.A TROPICAL LIANA
Gary W. Dil'ler O'Dellianas, woody perennial vinelike plants, abound
in tropical forests. One species, Mucuna urens
(Fabaceae), is a conspicuous component of sec-
ondary forests in Monteverde. Its local name, "ojo de
buey" or "bull's eye," derives from its hard black seeds.
The seeds contain toxic compounds that defend them
against predators such as bruchid beetles, although
large rodents such as agoutis ("guatusa," Dasyprocta
puncata) readily eat and store seeds and serve as the
major dispersers of Mucuna seeds. Apparently the 2.5-
cm seeds can remain dormant in the soil for more than
10 years. Anyone who has handled the seed pods of
Mucuna will appreciate its other common name, "pica-
pica" or "itch-itch." Dangling on long sterns from the
canopy, the pods are covered by a velvety coat of fine
urticating hairs that lodge in the skin (Fig. 3.11). Me-
dicinal uses of the seeds include relief from hem-
orrhoids. The urticating hairs, mixed with honey, are
believed to combat intestinal parasites.
Following germination, Mucuna actively grows
toward and up small understory trees, ultimately
reaching lengths of more than 70 m and heights of
more than 20 m in the canopy. Favored hosts include
Conostegia spp. (Melastomataceae) and hemiepi-
phytes such as Clusia spp. and members of the Arali-
aceae. Its long tangled vines provide canopy path-
ways for squirrels (Sciurus spp.) and other arboreal
mammals and perches for sit-and-wait predators
such as forest falcons (Micraster spp.) and night-
ingale thrushes (Catharus spp.). Pollination of the
greenish yellow flowers is carried out by long-tongued
bats such as Glossophaga spp., which visit the pen-
dent candelabra-like inflorescence. Among the insects
that feed on Mucuna leaves are the caterpillars of the
iridescent blue morpho butterfly (Morpho peleides).
Lianas and vines represent a sizable fraction of
all plant species and play an important but under-
appreciated role in neotropical forests. Besides serv-
ing as a food source for rodents, nectar-feeding bats,
and butterflies, lianas and vines influence food webs
in tropical forests. Some liana species, such as Mu-
cuna, enrich tropical soils through their mutualistic
interaction with nitrogen-fixing bacteria (Rhizobium
spp.) that inhabit the plants' root nodules. Their
leaves may make up as much as 30% of the dead
leaves on the forest floors in the tropics.
Not all of their impacts on other species are posi-
tive. Lianas and vines cover nearly half of all canopy
trees. In strong winds or heavy rains, they can dam-
age their host plants by breaking branches and pro-
viding sites for attack by plant viruses and other
pathogens. As a result, they may indirectly create
opportunities for shade-intolerant species to colonize
light gaps. Because of their impact on the structure
and dynamics of tropical forests, lianas and vines
should be included in conservation planning.EPIPHYTES
Stephen W, Ingrampiphytes are plants that depend on trees and
other plants for mechanical support but not nu-
trition. Unlike lianas and vines, epiphytes are
typically rooted or anchored on a tree and are free of
terrestrial connections for at least a portion of theirlife cycle. In the upper forest canopy, epiphytes are
subject to more frequent cycles of wetting and dry-
ing, more sunlight, and more air movement than un-
derstory plants (Bohlman et al. 1995). Epiphytes dif-
fer from forest understory trees and shrubs in their72 Plants and VegetationL
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