THEORY OF ISLAND BIOGEOGRAPHY

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THEORY OF ISLAND BIOGEOGRAPHY:

THEORY OF ISLAND BIOGEOGRAPHY

THEORY OF ISLAND BIOGEOGRAPHY:

THEORY OF ISLAND BIOGEOGRAPHY E.O. Wilson & Robert (1960) The theory was developed to explain species richness of actual island. The basic theory says that on larger island have large number of species, while smaller island have less species diversity . “number of species on island reflects a balance between the rate at which new species colonize it and the rate at which populations of established species become extinct .”

ISLAND:

ISLAND

ISLAND:

ISLAND Island is any area of suitable habitat surrounded by an expanse of unsuitable habitat. This may be a traditional island, a mass of island surround by water. The term may also be applied to many untraditional ‘island’ such as peak of mountains, isolated springs in the desert.

The Basic Explanation of Island Biogeography :

The Basic Explanation of Island Biogeography Every island has an equilibrium for the optimum number of species it can support. Species diversity mainly depends on 3 things 1)Extinction 2)Immigration 3)Emigration

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Other things that affect species diversity. Time Isolation Climate The distance of an island from other habitats is an important contributor to the level of immigration & emigration. Example: an island close to large mainland will have more animals arriving from the mainland to colonize for the island than an isolated island from many miles from other land will.

THE IMPLICATIONS OF ISLAND BIOGEOGRAPHY:

THE IMPLICATIONS OF ISLAND BIOGEOGRAPHY To understand species today & help endangered species. conservation of biology. Helps people understand species distribution around world. Assists in preservation of ecosystem

Factors :

Factors The Theory of Island Biogeography is determined by two factors. 1) The first is the effect of distance from the mainland . 2 )The mainland is where new immigrant species originally inhabited. The second is the effect of island size, These two factors establish how many species an island can hold at equilibrium. The equilibrium species number is the species richness of an island at which immigration balances extinction and which remains roughly constant

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Island Patterns - Species-Area Relationship On oceanic islands diversity less but area-effect stronger (curve steeper)

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Area and Abundance Oceanic islands are a special case of species-abundance relationship (Preston, 1962) Most Species are rare and only a few species are dominant Lognormal Distrubution Oceanic islands = smaller populations = fewer populous species

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Isolation and Speciation Low Immigration Rates Permit Speciation (vacant niches) Speciation increases diversity

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Establishment of Immigrants Population-Ecology Life Strategies r-Selected : disturbed ecosystems, broad ecological tolerance, rapid population growth K-Selected : mature ecosystems, stable population

Extinction :

Extinction The rate at which species might become extinct on island would be related to the number that have become residents .when an island is nearly empty, the extinction rate is necessarily low because of few species are available to become extinct . The rate at which additional species will establish population will be high when island is relatively empty ,and the rate at which resident population go extinct will be when island is relatively full. Example:

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Extinction of Birds in the Hawaiian Islands Selective extinction of ground-dwelling and carnivorous birds

Case study::

Case study : Fungi, Leaves, and the Theory of Island Biogeography John H. Andrews, 1 Linda L. Kinkel, ~ Flora M. Berbee,~ and Erik V. Nordheim 2 “Species dynamics of fungi (filamentous fungi and yeasts) on apple leaves were studied within the framework of the theory of island biogeography by following "immigration" and "extinction" patterns on individual apple leaf "islands" over time

Cont….:

Cont…. Analyses based on both the natural and the surface-sterilized systems showed that an equilibrium in species number was reached and turnover in species composition occurred in both species present on each island. The balance between immigration and extinction implies that species number on leaves and "real" (oceanic) islands is determined by a common mechanism, and emphasizes the need to regard leaf microbial communities as dynamic.

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