Biology Reference
In-Depth Information
Each evening back at camp, the botanists also shared their discoveries. Tropical botanists
often feel overshadowed on expeditions, perhaps because their quarry is stationary. Even if a
spectacular species is in flower or fruit, the display is ephemeral, unlike the headdress of the
bowerbird or the pelage of the golden-mantled tree kangaroo. But here in the Fojas, botanists
on the team came upon an eye-catching plant that rivaled anything found by the vertebrate
chasers. It was a rare white-flowered rhododendron and featured the largest bloom on record
for that genus, measuring almost eighteen centimeters across. (Wild rhododendron flowers
are seldom more than six centimeters in diameter.) The flower came from a canopy-living
shrub-like rhododendron that also appears as a shrub around bogs. Rhododendrons are com-
mon at high elevations, yet another example of adaptive radiation, this time in a common
genus of shrubs, trees, and climbers. In all, New Guinea is home to about 164 of the nearly
850 species of the genus
Rhododendron
; most are found in the uplands, as in such places as
the Fojas, where three unique species can be found.
The alpine zone above timberline in New Guinea's cordillera, including the Foja Moun-
tains, is quite small compared with those of the Himalayas and the Andes, so the alpine plants
endemic to this habitat would have very limited ranges. Robert Johns, one of the fathers of
botanical research in New Guinea, estimates that there may be as many as 15,000 to 20,000
species of plants endemic to New Guinea and its outer islands, or about 5 to 8 percent of all
vascular plants on Earth. About 70 to 80 percent of New Guinea plant species that are en-
demic have very limited ranges, most in the alpine zone. In contrast, the canopy tree species
in the lowland rain forests have wide ranges. The most common ones share an affinity for the
mainland tropical forests of peninsular Malaysia and the remnant rain forests of northeastern
Australia.
Plants offer yet another perspective on the link between endemism and rarity on islands
or other geographically isolated locales. Consider the plants on some more familiar islands:
Puerto Rico, Jamaica, Hispaniola, Cuba, the Galápagos, New Caledonia, New Zealand,
Hawaii, and even the Juan Fernández. Among all these islands, the Hawaiian chain, not the
fabled Galápagos, has the highest percentage of endemics. Hawaii has a flora of about 970
vascular plant species, with 91 percent found only on the islands. Right behind are New Zea-
land, with about 2,000 species and 81 percent endemism, and New Caledonia, with about
3,250 species, of which 76 percent are local. These three islands are in a class by themselves
globally, along with aforementioned New Guinea. Then there are the Juan Fernández Islands,
at about 200 native plant species and 62 percent endemism; Cuba, at 5,900 species and 46
percent; Hispaniola, at 5,000 species and 36 percent; and, bringing up the rear, the Galápa-
gos, at 700 and 25 percent; Jamaica, at 3,250 and 23 percent; and Puerto Rico, at 2,800 and
12 percent. The explanation for this pattern of rarity among islands, using endemic plants as
a rough indicator, would likely reflect distance from a mainland, topographic relief, variety
of habitats, and in the case of continental islands, the age of the island since separation. On
