Transcript History of Biogeography

Biogeography
Study of distribution of organisms
Biogeography
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Comparative observational science
Experiments – limited utility
Multiple scales
Comparative has uses, though
Synthetic science
Subjects Used in Biogeography
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Anatomy
Physiology
Taxonomy
Developmental
Evolution
Geology
Geography
Ecology
Climatology, Paleontology……
Relevance of Biogeography
• What enables a species to live where it doe,
and what prevents it from colonizing other
areas?
• What are a species closest relatives and
where can they be found? Where did its
ancestors live?
• How have historical events shaped a species’
distribution?
Overarching question: What shapes global
patterns of biodiversity?
The Importance of Time
• Historical biogeography
• Ecological biogeography
• Paleoecology
“While the process of science owes much to
admirable human traits……..it is also
retarded by characteristics such as
prejudice, jealousy, short-sightedness, and
stupidity.”
History of Biogeography
• Roots from questions that developed during
the “Age of Exploration”
• Shares common lineage with ecology
• Early questions
– From where did life come?
– How did it diversify across the planet?
Persistent Themes in Biogeography
• Classifying geographic regions based on their
biota
• Reconstructing historical development or lineages
and biota, including their origin, spread, and
diversification
• Explaining differences in numbers and types of
species among geographic areas, and along
geographic gradients
• Explaining geographic variation in characteristics
of individuals and populations of closely related
species
Age of Exploration
• 250 yr ago, only 1% of species known today
identified
• Mission – reveal mysteries of creation by
learning of the diversity of life
• Prevailing view – stasis
• With increasing identification of species,
was a clear need for organization
Carolus Linneaus (1707 – 1778)
• Understanding organization
would lead to knowing
Creator’s plan
• Took static view of Earth
• Explain origin and spread of
life
• Challenge was to explain
diversity and distribution
Carolus Linneaus (1707 – 1778)
• How could life have spread from Paradise
then landing spot of the Ark
• Linnaeus – “Paradisical Mountain” – a
mountain island life along the slopes,
perfectly adapted for biotic and abiotic
conditions at their “station”
• Based on known conditions of tropical
mountains
• Later formation of land allowed spread
Comte de Buffon (1707 – 1788)
• Contemporary of Linaeus
• Disagreed with his view of
spread of life (living and
fossil specimens)
• Places with same climate had
different species
• Inhospitable environment
around Mount Ararat
• Proposed origin in northern
Europe
• Buffon’s hypothesis – climate was cooler at time
allowing species to move to new areas and change
• Key points – climate and species were dynamic (central
to modern biogeographic theory and precursor to
development of evolutionary theory)
Comte de Buffon (1707 – 1788)
• Buffon’s Law –
Environmentally similar but
separated regions have
different species of birds and
mammals
• Considered first principle of
biogeography
• Later studies by Joseph
Banks and Johann Forster
found Buffon’s Law applied
to plants
Phytogeography
• End of 18th century –
natural theology still
primary biological theory
• Willdenow (1765-1812) and
Humboldt (1769-1859) –
phytogeography –
geographic distribution of
plants
• Studies of plant distribution
on Andes mountain (5,600
m elevation
Mt. Chimbaruzo
Phytogeography
• Identified floristic belts
from tropical to arctic
• Observed plant
communities closely
associated with local
climate
• Hints at competition
(Candolle)
Mt. Chimbaruzo
Biogeography of 19th Century
• First three themes established
– Classifying geographic regions based on their
biota
– Reconstructing historical development or
lineages and biota, including their origin,
spread, and diversification
– Explaining differences in numbers and types of
species among geographic areas, and along
geographic gradients
Biogeography of 19th Century
• Buffon’s Law
– Early biogeographers tested
– Classify regions based on biota (theme 1)
– Reconstructing origin and spread of life
(theme 2)
– Changes along gradients (theme 3)
– Established approachs still used
• Perception of static earth and life to
dynamic
Limitations
• Number of local species increased with
area
WHY??????
• Number of species decreased from
equator
• Needed to move to next step (rigorous
testing) but first needed
Needs for Better Understanding
• Better estimate of age of Earth (natural
theology and 6,000 yr)
• Understanding of dynamic nature of
continents and oceans
• Understanding of spread and
diversification – dispersal, vicariance,
extinction, evolution)
Early Advances of 19th Century
• Borngniart – father of paleobotany
• Lyell – father of geology
• Both used fossil record to conclude climate
changes over time (life forms of tropical climates
in northern Europe
• Lyell – changes in sea level and the lifting and
erosion of mountains; extinction
• New species arose through new creations after
extinctions; new species created for new climate
Early Advances of 19th Century
• Lyell proposed uniformitarianism
• Also, realization that processes occur slowly
(gradualism)
• Time needed for geological processes +
continual replacement of biota = Earth
much older than 6,000 years
Four British Scientists
• Charles Darwin, Joseph Hooker, Philip
Sclater, Alfred Russell Wallace
• Naturalists, traveling the world and
discovering diversity
• Shared their observations, building a
broader image of life
• Did not agree on all points
Darwin
• Origin of Species – contribution is obvious
• Proposed ideas on dispersal of life
(countering Agassiz’s view of point near
creation)
• The “dispersalist” view made dispersal
dynamic
• Disagreement then moved to mechanisms of
dispersal (dispersalists vs. extensionists)
Extensionists &
Land Bridges
Further Contributions
• Hooker – study of southern hemisphere
plant distributions lead to development of
vicariance biogeography
• Sclater – used distribution of passerine
(perching) birds to develop a system of six
biogeographic regions still used today
• Also developed zones based on marine
mammals (Fig. 2.8)
Wallace
• Greatest contributions to biogeography
(father of zoogeography)
• Expanded view provided by Sclater’s zones
• Established many of the basic principles of
biogeography (see Box 2.1)
• Observed a distinct change in fauna of
Southeast Asia and Australasia (Wallace
Line)
Other 19th Century Contributions
• Bergmann’s rule – homeotherms, body size,
and surface-to-volume ratio from poles
• Allen’s rule – limbs of birds and mammals
become shorter and stouter as move from
equator.
• Cope’s rule – groups tend to increase in size
during their evolution
• Limitation of generalities but open new
thoughts
Other 19th Century Contributions
• Merriam’s life zones
• Study of elevational changes – found
vegetation types and species composition
are similar to longitudinal patterns
• Confirmed Humboldt’s work
Twentieth Century
• Burdgeoning info from paleontology
• Origin, dispersal, radiation, and decline of
terrestrial vertebrates
• Development of phylogenies
– New groups rise
– Increase in number of species
– Radiate to fill niches and expand range
• Still – question of how dispersed
Twentieth Century
• Relationships between geological and
ecological properties of environment
• Patterns of morphological variation
• Coincided with Modern Synthesis
• Linking lead to formulation of biological
species concept (Ernst Mayr)
• Also identified allopatric speciation
Continental Drift
• Earth’s crust believed fixed until 1960s
• Continental drift 1st proposed 1858
• Resurfaced by Wegener and Taylor using
geological and ecological evidence
• Criticized and denied until evidence became
overwhelming
• Changed dispersal from land bridges to
movements of continents
New Phylogenetic Methods
• Continental drift lead to study of
disjunctions
• Vicariance biogeography
• Examination and revision of phylogenies
Further Aids
• Computers
• Geographic information systems
• Geostatistics