|
|
Wallaces's Line
Alfred Russel Wallace, the so-called father of animal geography, formulated his ideas on evolution by natural selection
while observing and collecting wildlife in the islands of Southeast Asia. He was particularly impressed by the sudden
difference in bird families he encountered when he sailed some twenty miles east of the island of Bali and landed on
Lombok. On Bali the birds were clearly related to those of the larger islands of Java and Sumatra and mainland Malaysia
while the birds on Lombok were related to New Guinean and Australian communities. He marked the channel between Bali and
Lombok as the divide between two great zoogeographic regions, the Oriental and Australian. In his honor this dividing
line, which extends northward between Borneo and Sulawesi, is still referred to today as Wallace's Line (see the map below).
"In this archipelago there are two distinct faunas rigidly circumscribed which differ as much as do those of Africa and
South America and more than those of Europe and North America; yet there is nothing on the map or on the face of the islands
to mark their limits. The boundary line passes between islands closer together than others belonging in the same group.
I believe the western part to be a separated portion of continental Asia while the eastern part is a fragmentary prolongation
of a former west Pacific continent."
Other biogeographers have since put the boundary between the Oriental and Australian provinces in slightly different
locations. As is true of most regions, the core areas of both provinces are clearly distinct, but things are a
little fuzzy on the periphery. Thus some biogeographers recognize the island region between Java and New Guinea as a
mixing zone and designate it Wallacea.
There were actually two 'Wallace Lines'. Wallace originally placed his boundary to the northwest of Sulawesi (Celebes),
but later relocated it to the southeast of this island. Without knowing it, Wallace had moved his line to a new position
that accurately matches the plate tectonic history of the archipelago. The Australia and Eurasia plates collided fifteen
million years ago, bringing two communities into contact that had been isolated from one another since the close of the
Cretaceous (65 million years ago). During glacial maxima, Sulawesi was in contact with the Eurasian mainland, while a
deep ocean trench separated Sulawesi from islands immediately to the southwest that were connected to Australia and New
Guinea. After Wallace, researchers drew a number of other 'lines' in this area - depending upon which animal group they
studied. Wallace used birds (especially parrots) but the dividing 'line' shifts across the archipelago depending upon
whether the subject studied was birds, mammals or freshwater fish. At present, biologists recognize that there is a
transition zone between the Eurasian and Australian communities. This biogeographic sub-region is known as Wallacea,
in recognition of Wallace's pioneering work.
|
Flora & Fauna
From the botanical standpoint the Wallace Line is less apparent, Sulawesi plants appear to be more closely related to
those of other dry parts of the archipelago.
Amongst the distinctive endemic animal species in the island are the rare anoa, tailless monkey and the inexplicable
babirusa, literally meaning "pig deer" (babiroussa babiroussa). The latter are considered the most peculiar
mammals of Sulawesi and are protected by law. There are 2 species of anoa (dwarf buffalo). One with smooth conical
horns is living in the mountains while the lowland anoa has rough horns. Despite their dog-sized body, their physical
appearances are like the placid water buffalo. Contrasting to the domesticated water buffalo, these species are
unpredictable, aggressive and sensibly feared by locals.
There are 7 species of Sulawesi black macaques, 3 of which occur in the province of North Sulawesi. They may be seen
at Tangkoko Batuangas – Dua Saudara Reserve on the northern tip of the island.
Also indigenous to Sulawesi are the maleo bird (which incubates its 250 gram eggs in mounds of soil warmed by sunlight,
hot springs or volcanic vents), tarsier (tarsius spectrum - world's smallest primate) with its head and body length of
just 10 cm, kuskus and the brightly colored Red-knobbed Hornbill. Many of these species may seen in Tangkoko Batuangus
Nature Reserve and Bogani Nani Wartabone (formerly known as Dumoga Bone) National Park. Several high-quality woods can
be found in these two natural reserves, such as Ebony, Ironwood, linggua, gopasa, nantu, meranti, etc. Rattan and
colorful orchids as well as various wild palms and other plant species grow in abundance in the forests throughout the region.
You may be aware that North Sulawesi lies firmly in the epicenter of marine biodiversity, but did you know that Bunaken National
Park is home to a living fossil fish whose body and habits have hardly changed over 400 million years of evolution? The coelacanth
(known locally as raja laut or "the king of the sea") is one of the most enigmatic fish known to man and was
long-considered a "missing link" between fishes and four-legged land animals.
So, what makes this mysterious fish so special? Coelacanths are large fish, reaching over 2m in length and weighing up to 100 kg.
They live in relatively deep, cold water averaging 150-200m in depth and 18° C in temperature, and seem to prefer steep volcanic
slopes with lava caves. During the day they rest in these caves in groups of up to 14, while at night they come out and drift
in the currents while searching for their prey (which includes small reef fish, cuttlefish, and even small bottom sharks).
Perhaps their most striking feature is their seven lobed fins, unique among living fishes. The paired pectoral and pelvic
fins are supported by girdles which resemble the pectoral and pelvic girdles of many land animals, and these paired fins are
moved in an alternating fashion which resembles a horse at a slow trot. Other interesting morphological features include an
intracranial joint and a hollow, oil-filled notochord instead of a backbone. The name coelacanth, which comes from the Greek
words for "hollow spine", refers to the hollow spines in the fish's fins.
Up until 1998, living coelacanths were known only from the western Indian Ocean. Three specimens had been captured from South
Africa, Mozambique, and Madagascar, respectively, but these individuals were considered "strays" from the true home
of Latimeria chalumnae in the Comoros Archipelago - where almost 200 specimens have been captured since 1952. This view
was shattered on July 30, 1998, when Mr. Lameh Sonatham captured a living coelacanth off the volcanic island of Manado Tua in
Bunaken National Park, almost 10,000 km from the Comoros!
|
The Manado Tua specimen was eventually found to represent a distinct
species, Latimeria menadoensis, and has since been formally listed as a protected species, both within Indonesia and
internationally.
So, you may ask, what are my chances of seeing a coelacanth while diving in Bunaken? Truthfully, quite low! Because of their
preference for deep, cold water, coelacanths are generally below the depth range of recreational scuba divers. In fact, until
recently, living coelacanths had only previously been observed in their natural habitat by scientists in research submarines.
This changed dramatically in October of 2000 when a team of trimix technical divers succeeded in locating a group of coelacanths
at a depth of 104m in Sodwana Canyon, St. Lucia Marine Reserve in South Africa. Several dive operators in Manado are currently
exploring options of starting technical diving operations within Bunaken National Park, so the day may come when you can join
a special group and dive for coelacanths and other bizarre animals of the deep in North Sulawesi's biodiversity hotspots.
Until that time, you'll have to be content drifting along Bunaken's famous walls, peering into her eerie depths, and wondering just
how many other as-yet-undiscovered sea monsters glide beneath you. Buy a locally-crafted coelacanth handkerchief or coconut shell
carving from your dive operator and support local conservation efforts...
Dr. Mark Erdmann
Dr. Mark Erdmann is a coral reef ecologist who currently works to support the management of Bunaken National Park.
Source:
"What's Happening?"
Manado Safari Tours Newsletter
|
|
|
Alfred Russel Wallace
(1823-1913)
English naturalist. From his study of comparative biology in Brazil and in the East Indies, he evolved a concept of evolution
similar to that of Charles Darwin. Like Darwin, he was greatly influenced by the writings of Malthus and Lyell and based his
theories on careful observation. His special contribution to the evidence for evolution was in biogeography; he systematized
the science and wrote The Geographical Distribution of Animals (2 vol., 1876) and a supplement, Island Life (1881).
His research in this field is commemorated in the name Wallace's Line. He assisted H. W. Bates in evolving an early
concept of mimicry. His other works include Contributions to the Theory of Natural Selection (1870), Darwinism (1889),
Social Environment and Moral Progress (1913), and an autobiography (2 vol., 1905).
Recommended Reading:
 Where Worlds Collide
by Penny Van Oosterzee
|
It is quiet along the black sand beach of Tangkoko forest. The light from the quarter moon seeps through the thick rainforest
canopy casting moonbeams across the forest floor. Two high-pitched squeaks emanate somewhere within a fig tree, and a tiny
tennis-ball sized tarsier emerges from the tree hole. Suddenly, he flies through the air with its long tail trailing behind,
cuts across moon beams and lands on a gecko. It stomps on the gecko's tail and while grabbing its neck with its right hand,
with a quick jerk of the hand, the gecko's neck is snapped, and dinner is served.
Their owl-like eyes, mobile ears, haunting songs, and nocturnal habits reinforce the tarsier's image as gremlins. These
gremlins of the forest are found throughout Asia. But the species found in Sulawesi, T. dianae, T. spectrum, T. pelengensis,
T. pumilus, and T. sangirensis are found only in Sulawesi. Sulawesi is a haven for evolutionary scientists and wildlife
enthusiasts. Sulawesi is an evolutionary mongrel bringing together plants and animals from neighboring biological regions,
Asia which includes Borneo and Australasia which includes Irian Jaya. As a result of this mix and a long period of isolation,
Sulawesi has created an enormous amount of evolutionary originals.
Tarsiers are often found in forest understorey where they search for insects and small reptiles. They perch about a meter
off the forest floor and scan the ground for prey, and leap incredible lengths. This leaping ability comes from the elongation
of their tarsal (ankle) region and fusion of the two lower leg bones, hence the name tarsius. They can turn their head a full
180 degrees; so that they can leap backwards without running flat into a tree trunk. Often found in a family unit, a mother,
father, and infant, the mother and father search for food while leaving the infant in the tree nest. Once hunting chores
are finished and the day breaks, the family reunite for daytime slumber. Although they do not require large forest areas,
they face threats common to all tropical rainforest animals. Their populations are negatively affected by habitat loss and
disturbance, and capture for trade. You can help tarsier conservation efforts by supporting or writing to conservation
organizations such as the Wildlife Conservation Society.
Dr. Robert J. Lee
Dr. Lee is a wildlife ecologist and Country Director for the Wildlife Conservation Society Indonesia Program.
Source:
"What's Happening?"
Manado Safari Tours Newsletter
|
|
