• 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

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

Hotspots of Endemism

• Australia, southern Africa, Madagascar, New Zealand, New Caledonia

• Other islands• Distinctive habitats (e.g., Devil’s Hole

pupfish – Fig. 10.3)

• Not so hotspots• Europe, North America, southern Atlantic

Ocean

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

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

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

Australian Region

• Two subregions– Eyrean – central 2/3 of

continent; arid/semiarid; no mtn. ranges or internal barriers

– Torresian – wetter fringes

Australian Region• 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

Plants – more regions but fits well with divisions of animal regions

Provinces of NA freshwater fishes;#s are: families, species, % endemic species

Provinces correspond to major basins

Are Boundaries Clear Separations

• Many biogeographic lines originally drawn to mark limits of species

• Are significant– Wallace’s 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

Lines are reversed

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

Large flightless birds originating on Gondwanaland

Same genus found in California and Europe

Disjunction by dispersal

Pupfish of SW US are another example

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

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?

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

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

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