Upload
arthur-tate
View
218
Download
1
Embed Size (px)
Citation preview
Chapter 14
April 27th, 2010
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
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
SLOSS Debate• Single Large Or Several Small
• Debate over whether a single large reserve is better than several small reserves for conservation of biodiversity