Patterns of Distribution

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Limits of distribution:

"inhospitable" environments
  • barrier / corridor
  • vary with taxonomic rank
  • vary with areal scale
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Correspondence of Scales

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Barrier, example climate

  • freezing limits for saguaros
    Saguaro
  • freezing limits for palm trees
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Barrier, example climate

  • freezing limits for saguaros
  • freezing limits for palm trees

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Overcoming Barriers - examples

  • Collard Dove in England (food, nesting sites)
  • Cattle Egret
  • Bats in Tucson
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Limiting Factors: anything that makes difficult survival, growth, or reproduction
  • topographic barriers
    • temperature (correlation)
    • moisture (Saguaro)
  • CO2
  • light
  • nutrients
    (aquatic)
  • Oxygen
  • pressure
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Distributions along Gradients

- Optimum Conditions
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Germination optima (summer temperature)
    Caryophyllaceae
  • Silene secundiflora - at lower temperater
      southern (drier) distribution
  • Lychnis flos-caculi - at higher temperature
      northern (cooler) distribution
  • Silene viscosa - broad temperature optimum
      grassland distribution (weed)
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Complex environmental gradients

  • Sow bugs temp., atm. humidity., light
  • C3 C4 plants

    latitude - soil moisture, temperature
    historically - CO2 next




Gradients and species interactions (competition)

  • barnacles (Chthamalus stellatus)
    • rare in subtidal
      Balanus balanoides competes
      Thais lapillus eats
    • low in supertidal (upper limit set by drying)
  • starlings (Sturnus vulgaris) 'urban' bird in North America
    • nesting space available (cities)
    • food scarce (countryside)
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Overcoming Barriers - Disturbance

  • Resistance to Invasion
    • Successful alien invaders a fraction of total introductions
    • Successful invaders depend on lower species diversity human-made habitats
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Overcoming Barriers
- distribution pathways

  • Corridor
  • Filter
  • Sweepstakes Route
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Corridors: favorable habitat connecting larger ones

  • Tethyan Sea (Pangean coastal faunas)
  • Bering Land Bridge [map]
  • Panama Isthmus [map]

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Filters: blocks or slows passage of some organisms

  • Arabian desert allows movement of animals between Africa and Asia
  • Sunda archipelago reptiles
  • Southwestern forest vertebrates [SW]
  • Panama Canal: freshwater separates Caribbean from Pacific
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Sweepstakes Routes: severe barrier that permits rare dispersals

  • Asian snails in the South Pacific
  • South American animals in the Galapagos
Plate Tectonics cheating!
  • Gondwanan flora introduced to Asia by Indian collision
  • Terranes
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Filter - American Interchange

Isthmus of Panama
  • Mammals evolve 220 Ma, before breakup of Pangea
  • K/T extinction 65 Ma, precedes Mammalian Diversification
  • Diverse S. American Fauna evolve
  • (140, 10) 3.5 Ma faunas invade S. America and diversify [map]
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American Biotic Interchange


Proportion of mammals that migrated (about 10%)

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(Webb and Marshall, 1982)




American Biotic Interchange


Diversification of mammals after migration (Webb and Marshall, 1982) next




American Biotic Interchange

  • Results of Faunal Exchange
    • Generic-level diversity of N. America remained unchanged
    • Generic-level diversity of S. America increased
    • Many S. American animals went extinct
        marsupial carnivores, eutherian herbivores
    • Current biota: 50% of S.American from North, 10% of N. American from South
(Webb and Marshall, 1982) next




American Biotic Interchange

    North American Mammalian Biota
    1. Better Migrations
    2. Better Speciators
    3. Better Competitors
(Webb and Marshall, 1982) next




Biotic Interchange

Vertebrates Other than Mammals
  • Bird and Reptile Fauna of S. America accumulated gradually rather than suddenly 3.5 Ma
  • 3.5 Ma invasion had more birds moving north than south
  • Northward migration of Ambhibians and Fish much greater than southward
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Lessepsian Exchange: The Suez Canal

  • Suez Canal, completed 1869
  • South to North: 50 fish, 20 crustaceans, 40 mollusks
  • North to South: 0
  • Hypotheses
    • Red Sea opening is saline so that biota can pass through salt lakes along canal
    • Red Sea fauna inhabits shallow sandy-muddy habitats, also like the canal "preadapted"
    • Red Sea fauna has better competitors (from the diverse Indian Sea fauna)
        "The bigger fauna wins"
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Distribution patterns and boundaries

  • does current distribution = fundamental niche?
  • relict - former widespread range reduced by environmental change
  • vicariance - former widespread range disrupted by environmental change
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Different factors influence distributions on different scales

Example Tree Groundsels
Clematis fremontii (Erickson, 1945)
    a. local "alpha"
    • ecological tolerance
    • competition
    • predation
    • seed dispersal
    b. regional "beta" & "gamma"
    • suitable habitats
    • geomorphic development
    • geological history
    c. global "gamma"
    • major environmental patterns
    • climatic change
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Different distributions within genera
British Isles "beta" & "gamma"

Dragonflies
  • Enallagma cyathigerum eurytopic
    • circumboreal - southward extnesion prevented by lack of ponds, and competition
  • Sympetrum sanguineum stenotopic
    • larvae only on Typha and Equisetum
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Disjunct Distributions - Evolutionary relicts

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Evolutionary disjunction

Southern Beech Nothofagus, veg. canopy map pollen
Geological
Time
New
Guinea
New
Caldonia
Australia New
Zealand
Antarctica Chile
Argentina
Pleistocene            
Pliocene            
Upper Miocene            
Lower Miocene            
Oligocene            
Eocene            
Paleocene            
Upper
Cretaceous
           
Schlinger, E.I. 1974. Continental drift, nothofagus and some ecologically associated insects. Annual Review of Entomology 19:323-343. next




Evolutionary Disjunctions
    Range-expansion, Migration, Speciation

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Disjunct Distributions - Climatic relicts

  • Springtails - Arctic, Pyrenees, Tatara Mts (but not Alps)
  • Artemisia norvegica Norway Scotland Urals
  • Aphodius holdereri (Himalayan) fossils in southern England
  • Arbutus unedo "migrated northward along coasts before English Channel flooded"
  • Gorillas 2 populations separated by climate change
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Endemism - isolation and stability

occurring nowhere else, unique to a particular area
    example: Sarcobatus Great Basin only picture
    Taxonomic effect: Lower taxonomic ranks tend to be more narrowly distributed

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Classification of Endemics

  • Place of origin
    • Autochthonous: originated within its current range
    • Allochtonous: originated elsewhere - relicts (epibiotics) example: tautara
  • Taxonomy
    • Taxonomic Relics: survivor of once-important taxon (family)
  • Biogeography
    • Biogeographic Relics: Once common and widespread species. example, Latemaria Crossopterygian fish: widespread during Paleozoic
  • By Age
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Cosmopolitan: Occurring throughout the world next




Provincialism: patterns of endemism

Terrestrial Regions
Biogeographic Provinces a product of
  • Geology
  • Climate
  • History

Hierarchy ~scale next




Provincialism - boundaries

  • Biogeographic Lines: rapid turnover at edge of provinces
    exact position usually indistinct
    Examples:
    • Indonesian (Oriental/Austrlian)
      Wallace, Murray, Muller, Sclater, Weber, Mayr
    • Panama
      Mammals, Fishes
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Provincialism - Islands

  • Island Biogeographic Classifications
    • Oceanic Islands: far from continents & never connected
      • Hotspots and Fracture Zones
        Hawaiian Islands, Marquesas Islands
      • Island Arcs
        Aleutians, Solomons
      • Midocean Ridge
        Azores, Faeroes
    • Continental Islands: at one time near to continent
      • Separated by Tectonic Rifting
        Madagascar, New Zealand
      • Connected during glacial sea-level lowering
        Tasmania, Falklands, New Guinea
      • Chain of Islands, Some with Pleistocene Connections
        Aleutians, Canary Islands, Philippines
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Provincialism

  • Marine Regions
    • Pelagic: Less pronounced than terrestrial
    • Coastal: Provinces bounded by temperature and salinity changes
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Similarity Indices

objective and repeatable means of comparison
  North America West Indes South America Africa
North America   40 55 8
West Indes 67   33 11
South America 81 73   3
Africa 31 27 25  
Flessa et al., 1979. Geology 7: 15.
       white generic similarity
       blue family.
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