Fundamental Unit of Biogeography
Geographic Range
Conveying Range – Outline Maps
Range of Sooty Butterfly (Zegris eupheme)
Conveying Range – Outline Maps
Range of Racoon (Procyon lotor)
Conveying Range – Outline Maps
Range of Three-ridge Mussel (Amblema plicata)
Conveying Range – Outline Maps
Bird Map
Conveying Range – Dot Maps
Locations for emerald shiner (Notropis atherinoides)
Conveying Range – Dot Maps
Locations for brown trout (Salmo trutta) –
dot and outline map
Conveying Range – Dot Maps
Blue jay distribution in 20th precentile contours
Conveying Range – Contour Maps
Blue jay distribution as relative abundance
Limitations
• Outline – not across entire range (clumped
disperson)
• Dots – inaccuracies of locale information
• Contour – spotty data
• BUT
– Georeferencing
– Geostatistics
– GIS – integration of data
Patchy Nature of Range - Spatially
Patchy Nature of Range - Temporal
Factors Affecting Distribution of Species
• Limiting abiotic factors (range of tolerance)
• Biotic interactions
• Hutchisonian niche – n-dimensional
hypervolume
Niche Dimensions and Range
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Fundamental niche
Realized niche
Fundamental geographic range
Realized geographic range
Distribution of the barnacle Chthamalus stellatus (Connel 1961)
Gaps in Distribution
• Metapopulations
– Sink and source subpopulations
– Atlantic snail
• Barriers
Other Source and Sink Distributions
• Migration – temporal and resourcedriven
• Irruptions
Red locust (Nomadacris
septemfasciata) – source
(black) and sink (gray)
range
Of Note
• Any fluctuations of population size will
influence the realized geographic range
All winter at high latitude –
will extend range with
resource shortage
Variation over Range
Abiotic Limiting Factors
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Range of tolerance
Fundamental niche
Overlapping effects
Trade-offs for tolerance of given factor
Disturbance
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Limit/expand range of species
Patch dynamics
Intermediate disturbance hypothesis
Bluff and Great Lakes Examples
Pupfishes (Cyprinodon nevadensis)
• Adults tolerate 0 –
42°C
• Found in cold to hot
springs across range
• Eggs develop at 2036°C
• Need access to a sink
habitat to persist
Biotic Factors - Competition
• Exploitative
• Interference
• Ranges are often reflection of “ghosts of
competition” past – example Connell’s
barnacle study
Kangaroo Rats (Didymops spp.) – was it
competition?
• Same niche
• Two disjunct species
• Realized niche of 3
species segregated by
substrate
• Competitive exclusion?
• Resource partitioning?
• Parapatric speciation?
• No evidence of
competition on edges
Biotic Effects - Predation
• Community regulator
• Coevolutionary mechanism
Loss of Barriers
Keystone Predator
Implications outside range of otter?
Mutualism – Correlate to Distribution?
Diffuse Competition
• MacArthur (1972) – southern limits of
many N. Amer. Birds not attributable to
– Abiotic factors
– Habitat limitation
– Competition or Predation
• 202 land birds in Texas, only 29 found in
Panama; Panama 564 land bird species
Yellow warbler (Dendroica petechia) – one of the 29 found in both.
Insectivore, limited to mangrove swamps and islands in tropics