Patterns of Distribution

Limits of distribution:

• barrier / corridor
• vary with taxonomic rank
• vary with areal scale

Correspondence of Scales

• Taxonomic rank
• Aerial scale
  
  • Correspondence of Global Boundaries with Barriers compare Good's, Sclater's and Wallace's Provinces.
  • Correspondence among unrelated taxa - Biomes
    example, North American Deserts

Barrier, example climate

• freezing limits for saguaros
  
  
• freezing limits for palm trees

Barrier, example climate

• freezing limits for saguaros
• freezing limits for palm trees

Overcoming Barriers - examples

• Collard Dove in England (food, nesting sites)
• Cattle Egret
• Bats in Tucson

• topographic barriers
  • temperature (correlation)
    • grey hair grass (Corynephorus canescens)
    • eastern phoebe (Sayornis phoebe)
  • moisture (Saguaro)
• CO₂
• light
• nutrients
  (aquatic)
• Oxygen
• pressure

Distributions along Gradients

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)

Complex environmental gradients

• Sow bugs temp., atm. humidity., light
• C3 C4 plants
  
  latitude - soil moisture, temperature
  historically - CO₂

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)

Overcoming Barriers - Disturbance

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

Overcoming Barriers
- distribution pathways

• Corridor
• Filter
• Sweepstakes Route

Corridors: favorable habitat connecting larger ones

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

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

Sweepstakes Routes: severe barrier that permits rare dispersals

• Asian snails in the South Pacific
• South American animals in the Galapagos

• Gondwanan flora introduced to Asia by Indian collision
• Terranes

Filter - American Interchange

• 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]

American Biotic Interchange

American Biotic Interchange

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

American Biotic Interchange

North American Mammalian Biota
1. Better Migrations
2. Better Speciators
3. Better Competitors

Biotic Interchange

• 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

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"

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

Different factors influence distributions on different scales

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

Different distributions within genera
British Isles "beta" & "gamma"

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

Disjunct Distributions - Evolutionary relicts

• Linnaeus, Gray - deciduous forest disjuncts
• Magnolia was widespread during late Cretaceous
• Range reduced during Pleistocene

Evolutionary disjunction

Evolutionary Disjunctions

Range-expansion, Migration, Speciation

• Patterns
  • Gondwanan Ratite Birds pic
  • Amphitropical plants
  • Habitat Specialists Uma
• Processes
  • ranges have contracted
    • Tertiary Camel
    • Pleistocene Plants

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
  

Endemism - isolation and stability

example: Sarcobatus Great Basin only picture
Taxonomic effect: Lower taxonomic ranks tend to be more narrowly distributed

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
  • Paleoendimic:
    • Ginkgo biloba
    • Ostrya knowltoni pic
    • Tertiary Relics
  • Neoendemic: Pleistocene or Holocene
    • Sarcobatus

• Animals
  • Homo sapiens sapiens
  • Falco peregrinus (peregrine falcon)
• Plants
  • Land Plants
    • Senecio (wind dispersed)
    • Pteridium (wind dispersed)
  • Aquatic Plants
    • Phragmites (wind dispersed)
    • Myriophyllum, Ceratophyllum (water-bird dispersed)
    • Azolla, Salvinia, Marsilea (water-bird dispersed)

Provincialism: patterns of endemism

• Geology
• Climate
• History

• Realms - Regions: example, Good's Floristic Regions
  • Subregions: example, Australian Subegion
    • Provinces: example South American Provinces
      • Districts ("big habitats")

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
    

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

Provincialism

• Marine Regions
  • Pelagic: Less pronounced than terrestrial
    • whales
  • Coastal: Provinces bounded by temperature and salinity changes
    • "Big Habitats"
    • Coastal California