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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What controls the number of plant and animal species on this island?
Does size matter?
Island in the Bay of Fundy
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
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.
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.
z = slope
c = intercept
= equilibrium species number
A. Natural experiments - Krakatau/Rakata
McArthur & Wilson’s equilibrium predictions from nearby islands:
30 bird species
40 yrs to equilibrium;
turnover: 1 species/yr.
Small mangrove islands in the Florida keys
“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.
Vacant urban lot,
Crowe, L. M. 1979.Lots of weeds: insular phytogeography of vacant urban lots. J. Biogeography 6: 169-181.
“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