Theory of island biogeography

Definition

The theory of island biogeography explains how the size and distance of islands from the mainland influence the diversity of species found on those islands. It highlights the balance between immigration and extinction rates, where larger islands closer to the mainland tend to support more species due to greater habitat variety and increased opportunities for species to migrate.

5 Must Know Facts For Your Next Test

1. The theory was developed by Robert MacArthur and Edward O. Wilson in the 1960s, laying the groundwork for modern conservation biology.
2. Island size is a critical factor; larger islands can support more species because they offer diverse habitats and resources.
3. Distance from the mainland affects species richness; islands closer to the mainland have higher immigration rates, leading to greater biodiversity.
4. The theory has practical applications in understanding biodiversity loss in fragmented habitats, such as urban areas and nature reserves.
5. Invasive species can disrupt the balance of immigration and extinction, often leading to decreased native biodiversity on islands.

Review Questions

• How does the theory of island biogeography explain the relationship between island size and species richness?
  • The theory of island biogeography posits that larger islands can support more species because they provide a greater variety of habitats and resources. This increased habitat diversity leads to lower extinction rates since larger populations are less vulnerable to random events. Additionally, larger islands offer more opportunities for new species to arrive through immigration, thereby enhancing overall biodiversity compared to smaller islands.
• Discuss how the concepts of immigration and extinction rates play a role in maintaining biodiversity on islands according to the theory of island biogeography.
  • The theory emphasizes that biodiversity on islands is maintained through a dynamic balance between immigration and extinction rates. When new species immigrate, they increase diversity, while extinctions reduce it. The equilibrium occurs when these two processes reach a balance, allowing for a stable number of species on an island. This interaction is heavily influenced by factors such as island size, distance from the mainland, and habitat availability.
• Evaluate the implications of the theory of island biogeography in understanding current conservation challenges, particularly regarding habitat fragmentation and invasive species.
  • The theory of island biogeography provides critical insights into contemporary conservation issues by highlighting how habitat fragmentation can mimic island conditions, leading to reduced biodiversity. As habitats become isolated, species face challenges similar to those on physical islands, such as decreased immigration opportunities and higher extinction risks. Additionally, invasive species can further disrupt these dynamics by outcompeting native organisms for resources, thereby complicating conservation efforts aimed at preserving biodiversity in fragmented landscapes.

Related terms

Species-Area Relationship: A principle that shows that larger areas tend to have more species due to increased habitat diversity and fewer extinction rates.

Equilibrium Theory:

The concept that species richness on an island reaches a stable state where immigration and extinction rates balance out.

Endemism:

The ecological state of being unique to a defined geographic location, often observed in island species due to isolation.