Biodiversity in the Amazon

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Lecture 11

• Biodiversity in the Amazon
• How did it get to be so diverse?
• Is is really a diverse ecosystem?
• The Future of this Biological Hotspot?

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Rainforest Facts

• Rainforests once covered 16 of land. Now, they
  only cover 6
• Nearly half of the world's species of plants,
  animals and microorganisms will be destroyed or
  severely threatened over the next quarter century
  due to rainforest deforestation.

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Rainforest Facts

• Experts estimates that 137 plant, animal and
  insect species are lost every single day due to
  rainforest deforestation.
• That equates to 50,000 species a year!
• While 25 of Western pharmaceuticals are derived
  from rainforest ingredients, less that 1 of
  these tropical trees and plants have been tested
  by scientists.

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The Amazon Rainforest

• A billion acres, encompassing areas in Brazil,
• Venezuela, Colombia and the Eastern Andean
• region of Ecuador and Peru.
• If Amazonia were a country, it would be the ninth
  
• largest in the world.

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The Amazon Rainforest
The Amazonian rainforest is the region with the
greatest biological diversity on Earth. Around
80,000 different types of plant and 30
million animal species are found there.
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Amazon Biodiversity

• One-fifth of the world's fresh water is in the
  Amazon Basin.
• A single pond in Brazil can sustain a greater
  variety of fish than is found in all of Europe's
  rivers.
• A 25-acre plot of rainforest in Borneo may
  contain more than 700 species of trees - a number
  equal to the total tree diversity of North
  America.

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Amazon Biodiversity

• The number of species of fish in the Amazon
  exceeds the number found in the entire Atlantic
  Ocean.
• A single rainforest reserve in Peru is home to
  more species of birds than are found in the
  entire United States.

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Biodiversity Facts

• The Amazon Forest holds some 2,500 tree species
  and 30,000 plant species
• (30 of all plant species).
• The Amazon's largest
• animal is the manatee,
• which can weigh half a ton
• and measure almost
• 10 feet in length.

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Biodiversity Source

• The Amazon Rainforest gets its life from the
  majestic Amazon River, the world's second largest
  river, which runs directly through the heart of
  the region.
• The rainforest itself is simply the drainage
  basin for the river and its many tributaries. The
  vast forest itself consists of
• four layers, each featuring its
• own ecosystems and specially
• adapted plants and animals.

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Cause of Species Richness in Amazonia

• Remains relatively unknown,
• scientists are just beginning to test many of the
• ideas.
• (Many are difficult to test).

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Cause of Species Richness in Amazonia

• Rivers responsible
• Stable Climate-which allowed speciation
• C. Great Climatic Change in the Past
• D. Underlying Geology in the Amazon Basin

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Biodiversity Source

• Rivers
• Geographic Speciation
• Refugia (Climate Change)

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Biodiversity Source

• Rivers

Alfred Wallace, 1850s (Father of
Biogeography) noted that range boundaries for a
number of animal species in the Amazonian rain
forest seemed to coincide with the region's many
rivers.
That observation marked the origin of one of the
leading hypotheses for why the Amazon harbors
such extraordinary biodiversity for its size.
In its modern form, this "riverine barrier
hypothesis" posits that the Amazon's major
rivers functioned as natural barriers to gene
flow between populations.
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Biodiversity Source
Wallace continued
As a result, the populations ultimately diverged.
This model has received a certain amount of
support from molecular studies in recent years.
Frog and small data suggest that the theory does
not fit with predictions based on riverbank
affiliation.
Rather the composition of these communities was
best predicted by geographic distance and habitat
type.
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Biodiversity Source
Wallace continued
Suggested recently that distributions of small
mammals terminated perpendicular to the river
and parallel to the Andes Mountains, which
suggests that the topography of the Amazonian
lowlands may generate the biodiversity.
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Biodiversity Source

• Speciation
• The evolutionary process whereby
• populations of a single species separate and,
• through being exposed to different forces of
• natural selection, gradually develop into
• distinct species.

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Geographic Speciation
Evolution of a new species. Three steps are
involved First, a species becomes split into two
populations over a period of time. These
populations are separated from another by some
geographical barrier (a mountain for example).
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Geographic Speciation
What are some types of geographic barriers? 1)
Mountains 2) Rivers, streams 3) Deserts 4)
Canyons 5) Lakes
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The strength of a geographic barrier (i.e., how
effective it is at reducing gene flow) is
dependent upon the dispersal abilities on the
organism.
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Secondly, as the species remain separated, they
evolve independently so that the two are now
genetically different. As the last step, the
barrier is removed and the species overlap in
their ranges, exploiting different niches and
surviving as separate species.
At this point we say that the species pass the
Test of Sympatry.
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Refugia Isolated areas of habitat in an
otherwise unstable environment. Haffers Refugium
Theory (1969) Proposed in 1969 by German
ornithologist Jurgen Haffer, attributes the
evolution of present-day biodiversity to plants
and animals having been geographically isolated
in the past (during the ice ages)
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Refugia

• Raised on modern biogeographic data but no
  reliable paeleocological data.
• Most recent manifestation is untestable as it has
  no time or habitat constraints (Haffer and Prance
  Amazoniana 2002).

Brown (1991)
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THE REFUGIA HIPOTHESIS
Haffer, J. 1969. Speciation in Amazonian forest
birds
Speciation of birds in the Amazon had been
produced by cycles of expansion and contraction
of forest environments during the Pleistocene
During glacial periods, reduced temperature and
humidity in the lowlands of South America left
relatively small islands of tropical
rainforests surrounded by xeric habitats
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THE REFUGIA HIPOTHESIS
Haffer, J. 1969. Speciation in Amazonian forest
birds
-six hypothetic forest refugia, which were
hypothesized to be the centers of biotic
diversification during Pleistocene Glaciations
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THE REFUGIA HIPOTHESIS
He reasoned that a cool, dry climate during
Pleistocene glacial periods would have allowed
vast expanses of arid grasslands to fragment the
previously continuous tropical rainforest.
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THE REFUGIA HIPOTHESIS
He reasoned that a cool, dry climate during
Pleistocene glacial periods would have allowed
vast expanses of arid grasslands to fragment the
previously continuous tropical rainforest.
Populations trapped in pockets of rainforest, or
refuges, would accumulate genetic variations and
eventually diverge into new species.
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THE REFUGIA HIPOTHESIS
He reasoned that a cool, dry climate during
Pleistocene glacial periods would have allowed
vast expanses of arid grasslands to fragment the
previously continuous tropical rainforest.
Populations trapped in pockets of rainforest, or
refuges, would accumulate genetic variations and
eventually diverge into new species.
Based on Darwinian ideas, the hypothesis caught
on quickly despite sparse geologic and climatic
data from the Amazon, a region that is still
difficult to study.
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THE REFUGIA HIPOTHESIS
Supporting Evidence?
Palynological Evidence
Paul Colinvaux et al. 1996 (One site in
north-western Amazon) Western Amazon was
forested in the Pleistocene as it is now
nothing but forest all the way through, the
record" Colinvaux
Hoorn C. 1997
(Amazon Fan)
Palynological data give no indication of major
vegetational changes in the drainage basin (of
the Amazon)
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THE REFUGIA HIPOTHESIS
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Four Layers of Amazon

• Forest Floor - lowest region.
• Receive 2 of the sunlight.
• Rich with rotting vegetation and the bodies of
  dead organisms, which are quickly broken down
  into nutrients integrated into the soil.
• Tree roots stay close to these available
  nutrients and decomposers such as millipedes and
  earthworms use these nutrients for food.

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Four Layers of Amazon

• Understory next layer above the forest floor.
• Receive 2-5 of sunlight
• Many of the plants have large, broad leaves to
  collect as much sunlight as possible. The
  understory is so thick that there is very little
  air movement.
• As a result, plants rely on insects and animals
  to pollinate their flowers.

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Four Layers of Amazon

• Canopy - where the action occurs
• Filter 80 of sunlight
• Many canopy leaves have specially adapted leaves
  which form "drip tips".
• Drip tips allow water to flow off the leaves
  which prevents mosses, fungi, and lichens from
  occupying the leaves.
• The canopy is where the wealth of the
  rainforest's fruits and flowers grow. Bromeliads,
  cup-like plants, provide drinking pools for
  animals and breeding locations for tree frogs.

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Four layers of Amazon

• Emergent layer - above the canopy
• Trees may reach 200 feet.
• Leaves in the emergent layer are small and
  covered with a special wax to hold water.
• Seeds are blown to other parts of the forest.
  Trees which rise to the emergent layer are
  massive.
• Trunks can be 16 feet in circumference. Many
  animals that survive in the emergent layer never
  touch the ground.

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Future of the Rainforest?
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Future of the Rainforest
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Future of the Rainforest
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Future of the Rainforest
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Future of the Rainforest
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Future of the Rainforest

• If deforestation continues at current rates,
  scientists estimate nearly 80 to 90 percent of
  tropical rainforest ecosystems will be destroyed
  by the year 2020.
• This destruction is the main force driving a
  species extinction rate unmatched in 65 million
  years.

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Loss of Biodiversity

• Once a vast sea of tropical forest, the Amazon
  rainforest today is scarred by roads, farms,
  ranches, and dams.
• Brazil is gifted with a full third of the world's
  remaining rainforests unfortunately, it is also
  one of the world's great rainforest destroyers,
  burning or felling more than 2.7 million acres
  each year. More than 20 percent of rainforest in
  the Amazon has been razed and is gone forever.

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Why the destruction?

• Rainforest is used for logging timber,
  large-scale cattle ranching, mining operations,
  government road building and hydroelectric
  schemes, military operations, and the subsistence
  agriculture of peasants and landless settlers.

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Conservation Efforts
Conservation Efforts? Is is worth
preserving? -Unknown factor (so much more to
know). -Home to a multitude of plants, animals
and people! -Important role to play in drug
(pharmaceutical) industry -Posterity-to ensure
that future generations will get to Appreciate
what a rich biologically diverse area is
etc. -Carbon sink (pulls CO2 out of the
atomsphere).
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Conservation Efforts
Impact of Human Activities in the Amazon (1980)
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Credits

• greatestplace.org (monkey background)
• rain-tree.com (wildlife collage)
• junglephotos.com (destruction collage)
• rainforesteducation.com (layers collage)
• worldwildlife.org (sounds)
• www.rain-tree.com (interesting facts)