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Island Biogeography

Island Biogeography. Equilibrium Theory Explanation of community structure as a function of size and distance from species pool Dispersal Geographic Isolation Extinction Makes it applicable to more than true islands. Island Biogeography.

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Island Biogeography

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  1. Island Biogeography • Equilibrium Theory • Explanation of community structure as a function of size and distance from species pool • Dispersal • Geographic Isolation • Extinction • Makes it applicable to more than true islands

  2. Island Biogeography • MacArthur and Wilson used past island studies to develop the theory • Species-area relationships • Species turnover • Species Isolation

  3. Species-Area Relationship and Size

  4. Rare Species and Extinction Applies to Distance

  5. Isolation and Species Area

  6. Species Isolation

  7. Species Isolation

  8. Species Turnover

  9. Species Turnover

  10. Species Turnover

  11. Equilibrium Theory of Island Biogeography

  12. Criticisms of Island Biogeography • Interspecific differences and species interactions • Assumed immigration, extinction, and turnover as stochastic • Species richness not composition • Interdependence of immigration and extinction • Treated as independent processes • Does not account for recruitment of new individuals already on island

  13. Criticisms of Island Biogeography • Biogeographically meaningful measures of isolation • Sometimes difficult to identify source without studying systematics • Composition question • Biogeographically meaningful measures of island size • Spatial heterogeneity • Ecological and biogeographical history

  14. Criticisms of Island Biogeography • Importance of speciation • If species are derived on island, then model is violated • Speciation probably only important on large, isolated islands in terms of number of species • Disturbance (ecological and geological time scales) • Would prevent equilibrium

  15. Tests of Island Biogeography Estimates of turnover on southern California Channel Islands

  16. Krakatau Revisited – Colonization Curves

  17. Krakatau Revisited – I/E rates

  18. Krakatau Revisited – I/E rates

  19. Simberloff and Wilson (1970) Experiment

  20. Krakatoa Revisited – Plant Colonization Succession had to proceed to allow animal colonization

  21. Accounting for Succession/Recruitment • How does succession alter likelihood that immigrants will survive and reproduce? • F = failure rate (species failing to est. breeding population • C = I – F • C decreases over time

  22. Disturbance Events • How to account for disturbance effects? • Disturbanes at same temporal scale as island I and E might prevent equilibrium • Shorter time scale (fires, drought…..) probably only slow process

  23. Possible Effects of Speciation Effect of Area Effect of Distance

  24. “Island” Applications of Island Biogeography • Freshwater Lakes • North American lakes (Post-Pleistocene) relied on connections to other waters, including streams and rivers, for colonization • Not near saturation • Example – Great Lakes; large but not many species; lotic sources depauparate

  25. “Island” Applications of Island Biogeography • African lakes – much older; high diversity from speciation through adaptive radiation • North American lakes, including Great Lakes, show evidence of same but not much time has passed

  26. Species-Area Relationships

  27. Species-Area Relationship in Rivers • Greater diversity in N. Amer. rivers • N. Amer. rivers generally have N-S flow • Would allow dispersal in advance of glaciers

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