Biology Reference
In-Depth Information
percentage is much lower, often as low as 10 percent, and most tree seeds are dispersed by
wind, water, or gravity. Left relatively undisturbed and undiscovered by the seed predators
congregating at the base of the parent, a distant seed would germinate and prosper. This phe-
nomenon also contributes to tropical canopy trees growing far apart from one another.
For George and Sue, knowing the distribution of the trees that were important resources
for the macaws and monkeys was a vital research question. So, like many before them, they
worked with teams of botanists to map the distributions. There was one simple but pervasive
problem, though: how to identify all those trees in the first place. Until the late 1980s, a lack
of reliable identification guides to nonflowering and nonfruiting plants had held back pro-
gress in field tropical biology. Botanists relied on flowers and fruits to identify species, but
few plants were ever in a reproductive phase at the same time, and the leaves of many species
all seemed to converge on the same basic shape—narrow, without teeth on the margins, and
with an elongated tip. Not much to go on.
Then came Alwyn Gentry, a curator at large with the Missouri Botanical Garden. While in
the field he noticed subtle features that escaped the attention of most collectors and curators,
many of whom had prematurely decided that leaves alone, or other vegetative features, would
be of little value in on-the-spot species identification. Gentry worked with another fine trop-
ical botanist, Robin Foster, to identify tropical trees and shrubs, including many rare ones, re-
lying only on parts on display every day—leaves, stipules, glands, twigs, bark, thorns, trunk,
or exposed roots. The clues to identifying species from these features never appeared in a
botanical text. That comprehensive field guide lived in Gentry's head.
“Fortunately, he started to write it all down for the rest of us,” said Adrian Forsyth, who
helped finance the publication of Gentry's magnum opus,
AFieldGuidetotheFamiliesand
GeneraofWoodyPlantsofNorthwestSouthAmerica(Colombia,Ecuador,Peru)
. While the
topic was in its final editing stage in 1993, Gentry's small plane crashed into a mountainside
in western Ecuador. Gentry died at the age of forty-eight, approaching the apex of his career.
Raul Tupayachi is a top Peruvian botanist and the head of George's botany field team.
Raul's uncle had worked for Gentry and handed down his inside knowledge. On the second
day of field-work, George, Raul, and I hiked on a trail through the Tambopata forest to join
the plant collectors. En route, we came upon a carpet of beautiful white blossoms resembling
pincushions. I stopped to pick up some of the fragrant
Inga
flowers that had fallen from a tall
tree. “You know, Eric,” Raul said, “we've already recorded twenty-two species of
Inga
, and
we may have twenty-five. It's the most diverse group of trees in this part of the Amazon.”
This was a striking instance of the interplay of rarity and abundance in the tropics.
What's more, many of those
Inga
species could be found on the same hectare. According
to standard textbook niche theory, the reason so many tree species, and so many within the
same genus, can share the same hectare of forest is that the trees divide up the available
niches in microvariations of their environment. These variations occur among many different
