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:
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?
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
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.
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.
c Applying the Arrhenius equation to Gleason’s data: z = slope c = intercept
Variations in value of c e.g. insects e.g. mammals plants
Variations in the value of z real world cases (0.26- 0.33)
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.
Vacant urban lots Crowe, L. M. 1979. Lots of weeds: insular phytogeography of vacant urban lots. J. Biogeography 6: 169-181. Vacant urban lot, Philadelphia
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 1902 1950 1830 1882