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Island biogeography

Island biogeography

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Island biogeography

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  1. Island biogeography What controls the number of plant and animal species on this island? Does size matter? Isolation? Habitat variation? Environmental history? Island in the Bay of Fundy

  2. Species - area relationships Johann Reinhold Forster (1729-98) served as a botanist with Captain Cook. After exploring the islands of the southern Pacific he observed: “Islands only produce a greater or less number of species as their circumference is more or less extensive”. Small islands harbour fewer species. The Forsters’ (father & son) collecting specimens in Tahiti

  3. Species-area relationships Arrhenius (1921) “Species and Area” Gleason (1922) “On the relation between species and area”. Ecology, 3. Gleason censused the plants in 240 1m2 plots in an aspen wood in northern Michigan. He found 27 species in total, with an average of 4 species per quadrat.

  4. Species-area relationships Preston (1962) “The canonical distribution of commonewss and rarity”. Ecology, 43. Preston introduced the ‘Arrhenius equation’: S = cAz where S is number of species, A is plot area, and c and z are constants.

  5. Applying the Arrhenius equation to Gleason’s data: z = slope c c = intercept

  6. Variations in value of c e.g. insects plants e.g. mammals

  7. Variations in the value of z real world cases (0.26- 0.33)

  8. What controls the species-area curve?

  9. What do these have in common? 1 3 2 4

  10. West Indian avifaunas

  11. Avifaunal evidence from oceanic islands 1000 100

  12. MacArthur and Wilson’s“Theory of Equilibrium Island Biogeography” (1967) = equilibrium species number

  13. The effects of island size

  14. Species-area curve, Galapagos Islands

  15. Galapagos plant diversity and microclimate: area is a proxy for habitat variability <300 m >500 m

  16. Plant diversity in the south Pacific: is the variability controlled by habitat variation?

  17. The effects of island distance

  18. Probability of success with target distance (metaphor)

  19. Dispersal probability with island distance

  20. Avifaunal diversity in the south Pacific: the effects of distance from PNG

  21. Real-world variations

  22. Testing the MacArthur and Wilson theory A. Natural experiments - Krakatau/Rakata

  23. Bird and mammaldiversity on the remnant islands of Krakatau vs. the biodiversity of neighbouring islands Rakata remnants neighbours Rakata

  24. Rakata bird colonization McArthur & Wilson’s equilibrium predictions from nearby islands: 30 bird species 40 yrs to equilibrium; turnover: 1 species/yr. ? Survey dates

  25. Rakata:plant colonization

  26. Rakata: plant immigration and extinction

  27. Testing the theory:artificial experimentsI: defaunation and colonization Small mangrove islands in the Florida keys

  28. Testing the theory:artificial experimentsII: colonization of artificial substrates Fouling panels

  29. Variations in turnover rate at equilibrium

  30. Extending the theory “Insularity is moreover a universal feature of biogeography. Many of the principles graphically displayed in the Galapagos Islands and other remote archipelagos apply in lesser or greater degree to all natural habitats” e.g. mountain-top alpine areas; islands of trees at the arctic treeline, urban parks, lakes, bogs, desert oases, clearcuts, islands of fragmented habitat, and even individual rocks, plants, etc.

  31. Lake and bog islands

  32. Mountain islands • Distribution of alpine tundra ecosystems in BC; an archipelago formed by hundreds of ± discrete islands separated by forest and prairie in the neighbouring valleys.

  33. Mountain islands

  34. Vacant urban lots Vacant urban lot, Philadelphia Crowe, L. M. 1979.Lots of weeds: insular phytogeography of vacant urban lots. J. Biogeography 6: 169-181.

  35. Fragmented habitat islands 1830 1882 “the breakup of a large landmass into smaller units would necessarily lead to the extinction or local extermination of one or more species and the differential preservation of others” Alphonse de Candolle, 1855 True for all habitats; e.g. Wisconsin woodlands 1902 1950

  36. Urban parks:breeding birds, Madrid (Spain)