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

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Presentation on theme: "Island biogeography Island in the Bay of Fundy What controls the number of plant and animal species on this island? Does size matter? Isolation? Habitat."— Presentation transcript:

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

2 Species - area relationships Johann Reinhold Forster ( ) 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 1m 2 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 = cA z where S is number of species, A is plot area, and c and z are constants.

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

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

7 Variations in the value of z real world cases ( )

8 What controls the species- area curve?

9 What do these have in common?

10 West Indian avifaunas

11 Avifaunal evidence from oceanic islands

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 mammal diversity on the remnant islands of Krakatau vs. the biodiversity of neighbouring islands 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 experiments I: defaunation and colonization Small mangrove islands in the Florida keys

28 Testing the theory: artificial experiments II: 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 Crowe, L. M Lots of weeds: insular phytogeography of vacant urban lots. J. Biogeography 6: Vacant urban lot, Philadelphia

35 Fragmented habitat islands “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

36 Urban parks: breeding birds, Madrid (Spain)


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