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HISTORICAL
BIOGEOGRAPHY
Historical Biogeography
How do we reconstruct the
origin, dispersal, and
extinction of taxa?
Historical Biogeography
How historical events have
affect the biology on the
planet?
Historical Biogeography
Changing
climate and
physical
conditions
Historical Biogeography
Historical Biogeography
Rearrangements
of the
continents and
ocean basins
Extinctions
Proliferation of
flowering plants
Proliferation of fish, mollusks,
& crustaceans
Catastrophic
collisions with
asteroids
➊
➋
➌➍
➎
Diversity has generally increased over the past several hundred million years
Historical Biogeography
An exclusive focus on
local environmental
conditions will yield an
incomplete
understanding of diversity
Historical Biogeography
Where or how to find
basic explanations
for geographic patterns in
species distributions and
communities?
Historical Biogeography
Related species: different places
How to explain?
Creation theory: Multiple
centers of creation
Evolution theory: common
center for ancestor
?
Historical Biogeography
Historical Biogeography
There are several fundamental processes
in biogeography
Isolation and
Evolution
Center
of origin
Evolution
Speciation
Extinction
Dispersal
Isolation and
Evolution
These are the processes by which organisms respond to changes in
the geographic template.
Isolation and
Evolution
The relative importance of movement, or dispersal, has been the
subject of great debate.
Historical Biogeography
Historical Biogeography
The early
“dispersalists”
included Darwin,
Alfred Russel Wallace
and Asa Gray.
Wallace
They argued that
disjunctions (a situation in
which two closely related
populations are separated
by a wide geographic
distance) could be best
explained as the result of
long distance dispersal.
Gray
Darwin
Historical Biogeography
The dispersalists were
opposed by the
“extremists”, who
believed that disjunctions
had resulted from
movement along ancient
corridors that had
disappeared.
Historical Biogeography
Lyell
Hooker
Among the leaders of the
extensionist movement
were Charles Lyell and
Joseph Hooker.
Historical Biogeography
Historical Biogeography
Historical Biogeography
No evidence was
ever discovered for the
lost corridors proposed
by the extensionists.
Historical Biogeography
Historical Biogeography
However, evidence surfaced in the 20th
Century for a new, powerful means of
continental drift
.
dispersal:
The movement of continents could raft
populations away from each other and
separate them in vicariant events
(tectonic, climatic, or oceanographic
occurrences that isolate previously
connected populations).
Historical Biogeography
What is dispersal?
Simply, the movement of
organisms away from their
birthplace.
Often, confined to a
particular life history stage.
As a result, the debate
between dispersalists and
extensionists has been
replaced by a debate
between dispersalists and
vicariance biogeographers
Don’t confuse with
dispersion, which refers to
the position of individual
organisms with respect to
others in the population.
Historical Biogeography
The role of dispersal in
biogeography is different.
Dispersal
Species B
Species A’
Biogeographers are
interested in those
dispersal events in which
species change their
range by dispersing over
long distances.
These events are rare,
and largely random.
Ancestral population
Geographic isolation
Speciation
Historical Biogeography
Dispersal and Range Expansion
In order to expand its range through dispersal,
an organism must be able to:
They are, however, critical
to understanding the
distribution of organisms.
Historical Biogeography
Dispersal and Range Expansion
Biogeographers often distinguish three types of
dispersal events that can accomplish this:
• Reach a new area.
• Survive the potentially harsh conditions
occurring during the passage.
1. Jump dispersal (“sweepstakes”)
• Survive and reproduce in the new area to the
extent that a new population is established.
3. Secular migration.
2. Diffusion.
How do they operate?
Historical Biogeography
Historical Biogeography
Jump dispersal
Definition:
Movement of individual organisms across great distances, followed
by the successful establishment of a population of the original
disperser's descendants at the destination.
This usually takes place over a time period less than the life span of
the individual and often over inhospitable terrain.
Historical Biogeography
Jump dispersal
Species “skips” over area outside its range to new location
Island colonisation
Some species lacking from islands – limited ability to disperse
(mammals, amphibians, freshwater fishes)
Also occurs across continents
Historical Biogeography
The sheepshead minnow
(Cyprinodon variegatus)
Estuaries and mangrove
swamps throughout the
Caribbean
It has been able to colonize these
habitats by dispersing many
hundreds of miles across ocean
water.
It’s ability to tolerate wide ranges of
salinity makes this possible.
Historical Biogeography
Historical Biogeography
Contrast
Jump dispersal is simply the colonisation of new areas over long distance.
An example can be seen in the rapid recolonisation of Krakatau after all life was
wiped out by the volcanic explosion of 1883
The many species of
sunfish (Lepomis
spp.) of the
southeastern United
States, lacking this
tolerance, were
unable to disperse to
Caribbean islands.
Historical Biogeography
We can see the same thing over
longer distances and greater
time periods for many other
archipelagoes.
The Galapagos lie 800 km west
of Ecuador in the Pacific Ocean.
The Hawaiian Islands lie 4000
km west of Mexico.
In both cases, there is
indisputable evidence of many
groups of organisms reaching the
islands by dispersal.
Historical Biogeography
Diffusion
Definition:
Diffusion is the gradual movement of populations across hospitable
terrain for a period of many generations.
Species that steadily expand their ranges can be said to be diffusing.
Gradual spread of of individuals outward from the margins of a species’
range.
It is a slower form of range expansion involving not just individuals, but
populations.
Historical Biogeography
Historical Biogeography
The cnidarians Velella and Physalia have sails
or floats that allow them to drift across the
surface of the ocean. In both cases, the
orientation of the sail causes them to drift
either to the right or left.
Historical Biogeography
Range expansion
Historical Biogeography
Dispersal
Dispersal of foraminifera
Secular migration
Paleogeographic reconstruction for late Pliocene (ca.
Movement of species - may be active (flying) or passive
(wind-transport, drifting on a log)
Definition:
Secular migration is diffusion taking place so slowly that the diffusing
species undergoes appreciable evolutionary change during the process.
The range of the species expands or shifts over long time intervals
(thousands or millions of years). The environments themselves may
change and natural selection acts on the descendant populations.
Evolutionary divergence through range expansion.
Evolutionary time scale.
Sexton P F , Norris R D Geology 2008;36:899-902
©2008 by Geological Society of America
Historical Biogeography
Historical Biogeography
Diffusion and Secular migration
Range extension:
the species is at first
found only in area A. It
later gradually extends
its range of distribution
into the neighbouring
area. However, in the
absence of any barrier
between the two
areas, it cannot
differentiate into a new
separate species.
Cox, C. B. & Moore, P. D. (2005). Biogeography. An ecological and evolutionary approach. Oxford: Blackwell
Scientific Publications, London.
Historical Biogeography
Vicariance
Ancestral population
Geographic isolation
Speciation
Shift happens
Historical Biogeography
Historical Biogeography
VICARIANCE?
VICARIANCE?
Isthmus of Panama closed ~ 3.1 MYA
Split ~150 “geminate” (twin) species
Vicariance :
Species distributions are determined by geological and
climatological events: continental drift, Pleistocene
glaciation etc
Historical Biogeography
Historical Biogeography
A. formosus
A. nuttingi
P6
Knowlton et al.(1993) created a
phylogeny of Pacific (P) and Caribean
(C) species pairs of Alpheus
P6
C6
P3
In 6 out of 7 cases, the closest
relative of a species was on the other
side of the Isthmus
Atlantic Ocean
C3
C3
P5
C5
Isthmus of Panama
P4
C4
Pacific Ocean
Allopatric speciation
in snapping shrimp
Alpheus –
sibling species
P7
P7
A. panamensis
A. millsae
53
P1
C1
P2
C2
Historical Biogeography
Historical Biogeography
VICARIANCE?
Vicariance: a species originally occupies
the whole of area A and B, but these
two areas become separated from
one another by a barrier. The original
species then differentiates, by
gradual genetic change, into two
separate species that are separated
by the barrier.
Jump dispersal: the species is at first
restricted to area A by a barrier that
separates if from area B, and only
later disperses across the barrier. The
two populations of the species now
each diferentiate into separate
species.
Cox, C. B. & Moore, P. D. (2005). Biogeography. An ecological and evolutionary approach. Oxford: Blackwell
Scientific Publications, London.
The final results of vicariant speciation
and of jump dispersal are identical.
Historical Biogeography
BARRIERS
The nature of long-distance
dispersal means that
organisms often have to
survive for periods of time in
environments that are hostile
to them.
These environments
constitute physical and
biological barriers to
dispersal.
The effectiveness of such
barriers in preventing
dispersal depends not only
on the nature of the barrier,
but also on the organism
dispersing.
Historical Biogeography
Pacific
Pacific
Pacific
Rise of the
Isthmus of Panama
Atlantic
Atlantic
Atlantic
Molecular phylogeny and geographical distribution of the intertidal snails, Cerithideopsis californica and C. pliculosa. A
maximum-likelihood tree was constructed based on 873 bp of the CO1 gene.
The major clades are categorized as clades A, B and the detailed subclades are within. Numbers near nodes are the support values
for the clade from the different analyses (ML/BI). The scale bar represents the phylogenetic distances expressed as units of expected
nucleotide substitutions per site. The distributions of the major genetic clades are shown at the right side of the figure. Numbers
near the geographical points indicate sample size. Letters indicate sampling sites.
Historical Biogeography
VICARIANCE / DISPERSAL
Bannerfishes(Chaetodontidae)
IAA:Indo-AustralianArchipelago
PeterF.Cowman
BIOTIC EXCHANGE AND DISPERSAL ROUTES
Corridors
Filters
Sweepstake routes
DISPERSAL: OVERCOMING BARRIERS
dispersal
corridor
dispersal
filter
sweepstakes
dispersal
A
A
A
B
B
B
corridor
habitats
A to B
dispersal
wide
variety
easy
limited
array
(oases)
difficult;
only certain
organisms
make it
none
occasional
migrants
Biogeographers often distinguish three kinds of dispersal routes based on
how they effect biotic interchange.
1. Corridors. Allow dispersal by permitting movement Contemporary
examples. Historical – account for related of different species or even
same species in widely separated regions
2. Filters. Conditions fall outside range of physiological tolerance.
Restrictive dispersal pathway. Conditions restrictive to some species,
not others. Can be biotic or abiotic
3. Sweepstakes routes. Hazardous or accidental dispersal mechanisms
by which animals move from place to place. The standard examples are
island hopping and natural rafts. Many land vertebrates live in the
Caribbean Islands, and (if their biogeography is correctly explained by
dispersal) they might have moved from one island to other, perhaps
being carried on a log or some other sort of raft.
Corridors are dispersal routes that
allow movement of most taxa from
one region to another. They do not
selectively discriminate against one
form, but rather allow a balanced
assemblage of plants and animals to
cross them.
The areas at the two ends of a
corridor should contain a fairly similar
assemblage of organisms.
The Bering Land Bridge which existed some 20,000 years ago likely functioned as a
corridor which allowed organisms to pass from northern Eurasia to North America
with very little selection of the types that could pass. Conditions along the corridor
would have differed little from those on either end.
Historical Biogeography
A filter is a dispersal route that
exercises some selection over the
types of organisms that can pass
through it.
As a result, the colonists are a
somewhat biased subsets of those
that could potentially pass.
The Arabian subcontinent acts as a
filter in that only certain mammals,
reptiles and ground birds can disperse
between northern Africa and central
Asia.
1. species originate in “centers of origin”
The Lesser Sunda Islands form a twoway filter for the reptilian fauna of
southeastern Asia and Australia. This
region is sometimes known as
“Wallacea”, and is bisected by
Wallace’s Line.
Historical Biogeography
Historical Biogeography
1. species originate in “centers of origin”
1. species originate in “centers of origin”
2. speciation follows
2. speciation follows
3. new species evolve and disperse, thus displacing
more primitive species to the periphery of the
center of origin
Historical Biogeography
1. species originate in “centers of origin”
2. speciation
3. new species evolve and disperse, thus displacing
more primitive species to the periphery of the
center of origin.
4. organisms disperse as far away as permitted by
their abilities and their physical conditions.
Historical Biogeography
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
Historical Biogeography
Burgeoning 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
Historical Biogeography
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
Historical Biogeography
Continental drift lead to study of
disjunctions
Vicariance biogeography
Examination and revision of
phylogenies
Approaches to investigating
historical biogeographic patterns
Phylogeography or historical biogeography
1. Emphasizes hypothesis testing
2. Uses phylogenies (many of which are
developed with molecular data)
3. Uses area cladograms
4. Uses fossil and geological data
Historical Biogeography
Computers
Geographic information systems
Geostatistics
HISTORICAL BIOGEOGRAPHY
VICARIANCE
DISPERSAL
END