Chapter 14 April 18th, 2012

Island Biogeography Loss of dispensability, the development of gigantism or dwarfism, the loss of antipredator defensive features and behaviors, the development of woody shrubs and trees from species that occur as soft-stemmed herbs on continents, and the development of highly specialized niches

Theory of Island Biogeography MacArthur and Wilson 1967 Constructs linkages between species-area relationships on islands to dispersal and extinction processes Large islands support more plants and animals than smaller islands Examples: Hawaii and Caribbean Nested pattern of insular communities Endemics

Islands that are closer to continents have higher species richness than those farther away Theory of Island Biogeography

Immigration balanced by extinction Species turnover

Small Island Effect – islands are too small to impact extinction rates Rescue Effect – populations of species on islands on the brink of extinction are rescued by the arrival of new immigrants of the same species Target Area Effect – size matters as much as distance Theory of Island Biogeography

Problems with Theory: –Treats all species the same in terms of immigration and extinction –Doesn’t take into account the impact that plants and animals might have in facilitating immigration by other species –Extinction of some species may make immigration for other impossible –Excludes speciation and evolution Theory of Island Biogeography

Problems with Theory: –Volcanic disturbances, invasive species, competition, ocean and wind currents, historical land connections, doesn’t account for humans not taken into account –Doesn't take migratory animals into account Theory of Island Biogeography

Island Rule The smaller the mammal, the larger it gets on islands; the larger the mammal, the smaller it gets on islands –Massive rodents on islands –Dwarf elephants on Mediterranean Islands