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ISLAND BIOGEOGRAPHY What is Island Biogeography? • A field within biogeography the study of the distribution of species spatially and temporally • Establishment and explanations of the factors which affect species richness of natural communities History • Founded by Robert MacArthur and E.O Wilson (ecologists) in the 1960s “The Theory of Island Biogeography” • Intention of predicting the number of species that would exist on a newly created island • Began on islands extends over to other biomes “Because islands are small geographic units with distinct boundaries, they serve as useful models to illustrate the mechanisms of biogeographic phenomena. Intensive ecological studies on islands have provided key insights into invasion and colonization patterns, dispersal mechanisms, and extinction rates.” - Encyclopedia Britannica Isolated populations can become genetically and morphologically distinct from the original ('source‘) population on the mainland over a period of time, whether through natural occurrences or in relation to the new environment. Principle of Island Biogeography “No island will contain the species of the mainland which served as the sources for colonization (MacAuthur 1972).” Immigration of species Biodiversity of an island is always build on the species from its Mainland. - - Terrestrial species(difficult) Aquatic species (easy) Hence, the Mainland contains bigger Biomass Two significant factors that contribute to the rate of species change are: 1) the area of the island 2) It’s distance from the mainland source. Formation of ‘new species’ New species migrate from other areas (usually mainland) and sometimes result in the extinction of the existing species • Competition • Genetic inbreeding Reaching Equilibrium The species on the island reaches dynamic equilibrium in population size and species diversity through the process of migration and extinction. • Once equilibrium is achieved: – the biomass of the island stays the same – the composition of species will change • Evolution is a significant process only on islands that are large and stable • On an unstable island, species cannot survive longer to undergo natural adaptation How can we use these principles when designing conservation areas?