Endemism

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• Endemism taxa occuring in one geographic place
  and nowhere else Cosmopolitan taxa that widely
  distributed throughout the world
• Disjunction closely related taxa that occur in
  widely separated areas with no individuals in
  region between
• Note use of taxa part of perspective of
  hierarchical scale applied in examining
  distribution

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Heteromyidae kangaroo rats and mice. Family
endemic to New World. Genus Didymops broad
distribution but Microdipodops endemic to Great
Basin
Two species of Didymops (kangaroo rats). D.
ordii covers most of genus range. D. ingens
endemic to San Joaquin Valley
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Hotspots of Endemism

• Australia, southern Africa, Madagascar, New
  Zealand, New Caledonia
• Other islands
• Distinctive habitats (e.g., Devils Hole pupfish
  Fig. 10.3)
• Not so hotspots
• Europe, North America, southern Atlantic Ocean

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Cosmopolitanism

• No truly cosmopolitan species although some come
  close
• Key is ability to disperse and adaptability
• Peregrine falcon
• Bat Family Vespertilionidae
• Aquatic Daphnia, water milfoil (Myriophyllum),
  duckweed (Lemna sp.)
• Very few genera found in all oceans

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Relict Endemics

• Taxonomic relicts sole survivor of once diverse
  group
• Biogeographic relict species with a narrow
  geographic range for a group once diverse

Paleozoic
Mesozoic
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Terrestrial Regions and Provinces

• Distinctive biogeographic areas are arranged
  hierarchically
• Regions largest of biogeographic areas
  continental in scope 10 regions
• Subregions smaller scale within regions
  distinctive within regions
• Provinces distinct areas with subregions
• District smallest scale distinct within
  provinces

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Australian Region

• Two subregions
• Eyrean central 2/3 of continent arid/semiarid
  no mtn. ranges or internal barriers
• Torresian wetter fringes

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• Torresian 3 provinces
• Torresian tropical belt with plants and animals
  with affinities for New Guinea and some SE Asia
  many from Pleistocene land bridge
• Bassian animals and plants adapted to cool,
  mesic climate relict species dating to
  Gondwanaland
• Westralia many endemics shares taxa with South
  Africa

Australian Region
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Plants more regions but fits well with
divisions of animal regions
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Provinces of NA freshwater fishes s are
families, species, endemic species Provinces
correspond to major basins
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Are Boundaries Clear Separations

• Many biogeographic lines originally drawn to mark
  limits of species
• Are significant
• Wallaces line follows Sunda Shelf (exposed
  during Pleistocene)
• Isthmus of Panama last area formed for
  Nearctic-Neotropical land bridge
• Obvious overlap due to dispersal
• Still see that most species do not venture far
  past

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Lines are reversed
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Disjunctions

• Closely related organisms living in widely
  separated areas
• Three likely scenarios leading to disjunctions
• Tectonic once on a joined land mass (e.g.,
  Gondwanaland
• Extinction of species in the area between current
  ranges
• Disjunction by dispersal

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Large flightless birds originating on Gondwanaland
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Same genus found in California and Europe
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Disjunction by dispersal
Pupfish of SW US are another example
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Maintenance of Distinct Biota

• Plenty of examples of biotic exchanges
• How have biogeographic regions been able to
  maintain distinct biota?
• Limitations of dispersal
• Ecological barriers species already present
• Physiological barriers needed to cross
  unfavorable habitats to get to favorable habitats
  in another region

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Biotic Exchange

• Introduction of non-natives shows it is possible
• Other examples already discussed
• Fossil evidence limited example Gondwanaland
  biota of India all Eurasian were they pushed to
  extinction or adaptation?

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Great American Interchange

• Mammalian exchange provides excellent example
• Mammals evolved 220 mya Pangaea still intact
• Taxa dispersed across land mass before began to
  break up
• K-T mass extinction lead to rapid diversification
• S. America separated 160 mya, largely isolated
  until 3.5 mya

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Great American Interchange

• Was imbalance in exchange
• 10 of N. Amer. species of South American
  ancestry
• Almost 50 of S. American species of N. American
  ancestry
• Filtering of some sort

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Possible Reasons Northern Species Held Fast

• Better migraters
• Only three extent S. Amer. sp. in N. Amer.
• Several survive in tropical forests of southern
  Mexico
• Better survivors and speciators
• Many N. American species diversified in S. Amer.
  example - camel
• Better competitors
• Radiation of genera and species from N. Amer.
  Ancestors shows strong evidence