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Lecture 16: Biogeography

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. Ratite Birds – Monophyletic.

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Lecture 16: Biogeography

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  1. Lecture 16: Biogeography Geographic dist’n of organisms (Wallace, Darwin) Historical Ecological Explanation complementaryExplanation - 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. Endemic Restricted Range Cosmopolitan Wide Distribution Geographic 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. 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 Range Expansion Speciation Vicariance Splitting Range Extinction of Middle population Dispersal vs. Vicariance 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

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