Tropical Biology

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Tropical Biology
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The Tropics

• the tropics are not a plot of convenient
  forest in Costa Rica they are an enormous realm
  of patchiness, and any theoretical thinking based
  on presumed general properties is bound to become
  an in-group exercise in short-lived futility
• Paulo Vanzolini

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Tropical Paradigm
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Also tropical
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Paradigm Shift

• Temperate View of Tropics a place where
  hummingbirds migrate to escape the harsh winters
  of the temperate zone
• Tropical View of Temperate Zone a place where
  tropical hummingbirds go to utilize the seasonal
  abundance of flowers with few competitors

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Donde?
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The Tropicsclimate

• Relatively constant temperatures (warm..highs
  about 31oC and nighttime low of about 22oC)
• How much sun does Manus get a yr? How much does
  NY get?
• The tilt and rotation of the earth
• The intensity of sunlight

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The Tropicsclimate

• Relative humidity high (rarely
• Relative constant temperatures (e.g. generally
  
• Relatively constant daylength
• Can rain almost any day, but seasonality is
  generally the dominant theme
• Annual averages vary dramatically (e.g. Amazon
  200cm, western Chile almost 0)

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El Niño

• There are dramatic events that happen
  periodically
• Originally near Christmas
• Unpredictable warming of the eastern Pacific
  Ocean surface waters near equator
• Occurs about every 2-7 years, it destroys the
  stable weather of westward blowing tradewinds

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El Niño trade winds
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El Niño

• Resulting change in wind can breakdown ocean
  currents and even reverse flows
• Ultimately, not only changes weather patterns in
  S Am, but all over the globe

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Seasonality

• Despite the relative constantness of so many
  climatic variables, there is a strong and
  important seasonality to the tropics

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Rainfall Variability
Andagoya 709cm
177cm
263cm
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Seasonality

• Although rain may fall in every month, there is
  usually a distinct wet/dry season
• Sometimes there are additional mini wet and dry
  seasons occurring within each other (e.g. Brazil
  cerrado-March)
• When dry period becomes too pronounced, may shift
  to a tropical deciduous forest

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Seasonality

• The seasonality impacts most organisms in the
  tropics ranging from flowering phenology, seed
  production, plant germination, timing of
  breeding, animal migration, fruiting, spawning
  for riverine species, grazing rates (why and
  when?), dietary shifts (e.g. ants to termites),
  behavioral movements

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The Importance of Mountains

• a bad earthquake at once destroys out oldest
  associations the earth, the very emblem of
  solidarity, has moved beneath our feet like a
  thin crust over a fluid one second of time has
  created in the mind a strange idea of insecurity,
  which hours of reflection would not have
  produced
• Charles Darwin

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Mountains

• Mountains can impact weather patterns by forming
  giant walls which act to keep moisture in and
  prevent it from escaping
• For example, up to 75 of precipitation in the
  central Amazon basin is directly from
  evapotranspiration from the rainforest itself

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Mountainsa giant bathtub
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Mountainsrain shadow
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Mountains

• Rain shadow

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Mountains

• There can be strong zonation patterns associated
  with mountains
• For example, lowland rainforest transition to
  deciduous forest, to cloud forest, to an extreme
  form of elfin forest. After that, it can continue
  to an alpine shrubland, and an alpine grassland.

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Mountain Zones

• In general, temperature drops about 1.5oC for
  every 300m rise in elevation
• Tropical forests rarely exceed 1,700m being
  replaced by subtropical forest (1,700-2,600m)
  above which only shrubland or grassland habitat
  persists

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Zonation on Two Axes
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Mountain Biology

• Mountains also create fantastic opportunities for
  isolation and localized specialization
• Speciation!!

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Mountain Biology

• Mountains also create fantastic opportunities for
  isolation and localized specialization
• Speciation!!
• Consequently, mountain zones have some of the
  highest biodiversity in the world

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Tropical Habitats

• Subtropical Arid
• Subtropical Moist/Humid
• Tropical Arid
• Tropical Moist
• Savannah
• Coastal
• What about areas in between?
• These are frequently the areas with strong
  seasonal effects (e.g. tropical deciduous)

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Subtropical Moist
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Sub- and Tropical Arid
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Tropical Moist
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Tropical Savannah
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Tropical Coastal Ecosystems

• Many of the same systems occur in the tropics as
  temperate (e.g. lakes and rivers), but have very
  different abiotic influences, which strongly
  impact the biotic communities inhabiting them
• There are also distinctly tropical (or
  subtropical) systems (e.g. mangrove, coral reef,
  seagrasses)

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Coastal Ecosystemsmangroves

• Forests of mangrove line tropical coasts,
  lagoons, and offshore islands
• Mangrove is not a taxonomic term, but is based
  upon physical attributes (34 sp., 8 sp. in
  Neotropics)
• Tend to exhibit aerial roots, strongly adapted to
  high salinity, and are taxonomically distinct
  from terrestrial relatives
• Range in size from shrublike to 10-20m tall

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Coastal Ecosystems
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Coastal Ecosystemsmangrove distribution
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Coastal Ecosystemsmangrove distribution
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Coastal EcosystemsSeagrasses

• Closely associated with mangroves, seagrass beds
  are vast floats that inhabit the clear, shallow
  sea
• True flowering plants, not algae
• Spread via rhizomes
• System is very productive (higher than most
  terrestrial or marine systems)
• Productivity quickly moves from above water into
  water

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Coastal EcosystemsSeagrasses

• How? Fallen leaves or sticks quickly colonized by
  bacteria, fungi, and protozoans, concentrating
  protein
• These leaves now grazed by shrimp, worms, crabs
  and various fish (e.g. juvenile snapper and
  grunts). Process continues again on smaller
  pieces.

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Coastal Ecosystems
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Coastal Ecosystems
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Coastal Ecosystems
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Coastal EcosystemsCoral Reefs

• Found in tropical seas surrounding islands and
  paralleling coastlines
• Confined to warm (20oC, 68oF) waters
• Actually an animal (Coelenterata/Cnideria)
• Incredibly productive
• Lacks large plants, one-celled algaes
• Neotropics richness poor (60 vs 700 in
  Indo-Pacific 500 Bahamas vs. 1,500 GBR vs. 2000
  Philippines)
• Alpha diversity vs. beta diversitysimilar

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Coral Reef vs. Rainforest

• High productivity (but low plant diversity)
• High S of animals, including predators
• Territoriality and sexual selection evident
• Extensive examples of co-evolution
• E.g. cleaners false cleaners
• Many cryptic species, warning coloration
• Strong importance of periodic disturbance
  (Connells intermediate disturbance hypothesis)

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Coral Reef Distribution
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Coastal Ecosystemscoral reef distribution
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