1. Lecture 16: Biogeography
Geographic dist’n of organisms (Wallace, Darwin)
Historical Ecological
Explanation complementary Explanation
- past current
- large scale small scale
Want to find distribution of monophyletic groups

2. Ratite Birds – Monophyletic
Once thought convergent
But, movement of continents
ostrich rhea emu
Africa S. America Aust.
cassowary kiwi tinamou
Aust. / N. Guinea N. Z Neotropical

3. Geographic Distribution
Endemic
Restricted Range
Cosmopolitan
Wide Distribution
Description of distribution depends on taxonomic rank
e.g. Warblers
Relictual: very narrow range
e.g. Tuatara (only New Zealand)

4. Range Expansion 1. Dispersal A) Active : locomotion B) Passive:
edible fruit with resistant seeds
resistant eggs on feet of water birds.
parasitic stages in the life cycle.
wind, water currents
e.g. cockleburs

5. All organisms are mobile at some stage
Mobility
All organisms are mobile at some stage
Ferns & Fungi:
fine spores: wide distribution
Fresh-water Fish:
motile: restricted in distribution
need geologic changes for dispersal
Marine Fish :
planktonic eggs & larvae
widely dispersed by ocean currents.

6. True Range Expansion Peripheral Colonization (range expansion) vs.
Satellite Populations (accidental dispersal)

7. Barriers to Dispersal unsuitable habitat strong competitor
severe predation
Probability of accidental dispersal :
mobility & type of border
maple seed
fern spore

8. Ways to Expand Range other than Dispersal:
2) Adaptive Radiation :
adaptation to formerly unsuitable habitat
e.g. progressive drought resistance:
eventual dispersal across desert
3) Geological & Climatological Changes: elimination of dispersal barrier

9. Dispersal vs. Vicariance
Range Expansion
Speciation
Vicariance
Splitting Range
Extinction of Middle population X

10. Vicariance: Pleistocene glaciations
2 million - 10,000 years ago
Cold adapted Cold adapted
Warm adapted Warm adapted
Time
Refugia

11. Continuity of Distribution
Vicariance : disjunct
Dispersal : disjunct or continuous
Disjuct Distributions:
Tapir : Malaysia, neotropics
Cacti : N & S. America, Madagascar
Alligators: Asia, North America

12. Biogeographical Patterns
Congruent Distributions are common among endemic taxa
e.g. South America
Suboscine Birds, Edentates, Platyrrhine Primates, Caviomorphs

13. Geographical History
Patterns in biogeography often demonstrate history
e.g. Biogeographical realms reflect breakup of supercontinent
Wallace’s line

14. New Zealand Narrow endemism
New Zealand & New Caledonia from Australia.
~ 80 million years ago.
Australia from Antarctica:
~ 50 million years ago.
Antarctica from South America:
~ 60 million years ago

15. Convergence Common in similar habitats across realms
e.g. Desert Bipedal Rodents
North America Asia Australia
Heteromyidae Dipodidae Muridae

16. Distributions Elephantidae: Origin: Africa (Pliocene 5mya)
Dispersed: N. Amer. (Bering land bridge)
mammoths: extinct
Camels:
Origin: N. Amer. (Eocene)
Dispersed: Eurasia (Bering)
: S. Amer. (Isthmus)
Extinct in all but S. Amer., N. Africa, Asia