Fundamental Unit of Biogeography
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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
• 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 resource-driven
• 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
• Range of tolerance• Fundamental niche• Overlapping effects• Trade-offs for tolerance of given factor
Disturbance
• 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 20-36°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
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