Definition

Island Biogeography is the study of the distribution, diversity, and richness of species on islands and isolated habitats. It explores how ecological and evolutionary processes shape island ecosystems, focusing on colonization, extinction, and species equilibrium.

Key Concepts

1. Species-Area Relationship

  • The number of species increases with island size.
  • Larger islands support more habitats and resources.

2. Distance Effect

  • Islands closer to the mainland receive more colonizing species.
  • Isolation reduces immigration rates.

3. Equilibrium Theory (MacArthur & Wilson, 1967)

  • Species richness on islands is a dynamic balance between immigration and extinction.
  • Immigration rate decreases as more species arrive (fewer new arrivals).
  • Extinction rate increases with more species (competition, limited resources).

Island Biogeography Diagram

Processes Influencing Island Biodiversity

Process Description
Immigration Arrival of new species from the mainland or other islands
Extinction Loss of species due to competition, predation, or stochastic events
Speciation Evolution of new species due to isolation and unique selection pressures
Adaptive Radiation Rapid evolution of diverse species from a common ancestor

Types of Islands

  • Oceanic Islands: Never connected to mainland; formed by volcanic activity (e.g., Hawaii).
  • Continental Islands: Once connected to mainland; separated by rising sea levels (e.g., Madagascar).
  • Habitat Islands: Isolated patches within a different habitat (e.g., forest fragments in farmland).

Mathematical Models

Species Equilibrium Model

  • S = cA^z
    • S: Number of species
    • A: Area of island
    • c, z: Constants determined empirically

Rate Curves

  • Immigration and extinction rates plotted against species number.
  • Equilibrium point: where the two curves intersect.

Three Surprising Facts

  1. Small islands can have higher extinction rates even if they are closer to the mainland, due to limited resources and smaller populations.
  2. Some species undergo “island gigantism” or “island dwarfism” due to unique evolutionary pressures, such as the now-extinct dwarf elephants of Mediterranean islands.
  3. Habitat fragmentation on continents creates “island-like” effects, making Island Biogeography relevant for conservation in urban and agricultural landscapes.

Recent Research & Developments

  • 2021 Study (Nature Communications): “Global patterns and drivers of avian extinctions on islands” found that invasive species and habitat loss remain the primary drivers of bird extinctions on islands, emphasizing the ongoing relevance of Island Biogeography for conservation planning.
    Read the study

Case Studies

1. Krakatau (Indonesia)

  • After the 1883 eruption, all life was wiped out.
  • Studied colonization and succession of plant and animal species over decades.
  • Demonstrated the principles of immigration, extinction, and equilibrium.

2. Galápagos Islands

  • Famous for Darwin’s finches.
  • Showcases adaptive radiation and speciation due to isolation.

3. Florida Keys Experiment

  • Mangrove islands were fumigated to remove arthropods.
  • Researchers observed recolonization, supporting equilibrium theory.

Island Biogeography in Conservation

  • Designing Nature Reserves: Insights help determine size and connectivity for reserves.
  • Habitat Corridors: Reduce isolation effects for fragmented habitats.
  • Predicting Extinction Risk: Smaller, isolated reserves may lose species faster.

Teaching Island Biogeography in Schools

  • Secondary Schools: Introduced in biology/ecology modules, often via case studies or simulation games.
  • Fieldwork: Visits to local “habitat islands” (e.g., ponds, woodlands) to observe species diversity.
  • Interactive Models: Use of computer simulations to demonstrate immigration/extinction rates.
  • Project-Based Learning: Students design their own “islands” and predict species richness.

Career Connections

  • Conservation Biologist: Applies island biogeography to design protected areas and manage endangered species.
  • Ecological Modeler: Develops mathematical models for species distribution.
  • Environmental Consultant: Assesses impacts of habitat fragmentation.
  • Wildlife Manager: Plans corridors and reserves based on island principles.

Quantum Computing Connection

  • Quantum computers use qubits, which can be both 0 and 1 at the same time (superposition).
  • Island Biogeography models can be enhanced using quantum algorithms to simulate complex ecological networks and predict biodiversity outcomes under different scenarios.

Revision Checklist

  • [ ] Define Island Biogeography and key theories.
  • [ ] Explain species-area and distance relationships.
  • [ ] Describe equilibrium theory and its mathematical basis.
  • [ ] Identify real-world case studies.
  • [ ] Understand conservation implications.
  • [ ] Connect to career paths and modern technology.

Further Reading

Island Species-Area Relationship