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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. Species - area relationships.

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island biogeography
Island biogeography

What controls the number of plant and animal species on this island?

Does size matter?


Habitat variation?

Environmental history?

Island in the Bay of Fundy

species area relationships
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


Small islands harbour fewer species.

The Forsters’ (father & son) collecting specimens in Tahiti

species area relationships3
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.

species area relationships4
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.

variations in value of c
Variations in value of c

e.g. insects


e.g. mammals

variations in the value of z
Variations in the value of z






macarthur and wilson s theory of equilibrium island biogeography 1967
MacArthur and Wilson’s“Theory of Equilibrium Island Biogeography” (1967)

= equilibrium species number

testing the macarthur and wilson theory
Testing the MacArthur and Wilson theory

A. Natural experiments - Krakatau/Rakata

Bird and mammaldiversity on the remnant islands of Krakatau vs. the biodiversity of neighbouring islands





rakata bird colonization
Rakata bird colonization

McArthur & Wilson’s equilibrium predictions from nearby islands:

30 bird species

40 yrs to equilibrium;

turnover: 1 species/yr.


Survey dates

testing the theory artificial experiments i defaunation and colonization
Testing the theory:artificial experimentsI: defaunation and colonization

Small mangrove islands in the Florida keys

extending the theory
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.

mountain islands
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.
vacant urban lots
Vacant urban lots

Vacant urban lot,


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

fragmented habitat islands
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