Island Biogeography

Summary

This lecture by Dr. Kloor explores island biogeography, focusing on how species numbers on islands are influenced by immigration and extinction rates. Larger islands tend to support more species due to lower extinction rates and higher immigration rates, while smaller islands have the opposite effect. The principles of island biogeography also apply to land habitats fragmented by human development, where maintaining biodiversity requires fostering movement between populations through habitat corridors. The lecture underscores the importance of understanding these dynamics for conservation efforts.

Takeaways

• 📚 Island biogeography studies the number of species on an island and how it changes over time.
• 🌍 Two key factors determining species on an island are immigration rates (new species arriving) and extinction rates (species disappearing).
• 📉 As the number of species on an island increases, the immigration rate tends to decrease since the chances of new species arriving diminish.
• ⚖️ The equilibrium point is when the number of new species arriving equals the number of species going extinct on the island.
• 🏝️ Larger islands tend to have lower extinction rates and higher immigration rates than smaller islands.
• 🦅 Dispersing animals are more likely to find larger islands, leading to higher immigration rates compared to small islands.
• 📊 Data from the Caribbean confirms that larger islands support more species than smaller islands.
• 🏗️ Human development causes habitat fragmentation, turning landscapes into isolated 'islands' of habitat, which can impact biodiversity.
• 🔄 Metapopulations consist of interconnected populations, allowing for species movement between habitat fragments, helping maintain biodiversity.
• 🌿 Habitat corridors between fragments can promote species movement and prevent local extinctions in fragmented landscapes.

Q & A

What is island biogeography?

Island biogeography is the study of islands and the factors that determine the number of species present on an island, including the rates of immigration and extinction.

What are the two major factors that determine the species presence on an island?

The two major factors are the rate of immigration (the arrival of new species) and the rate of extinction (the loss of species from the island).

How does the number of species on an island affect the immigration rate?

As the number of species on an island increases, the immigration rate decreases because the chances of a new species being introduced diminish, as many species may already be present.

Why does the extinction rate increase as the number of species on an island grows?

The extinction rate increases as the number of species grows because competition for resources intensifies, leading to the local extinction of some species.

What is the equilibrium point in island biogeography?

The equilibrium point is where the rate of immigration equals the rate of extinction, predicting a stable number of species on the island.

How does island size influence the number of species?

Larger islands support more species due to lower extinction rates and higher immigration rates, as they offer more resources and are easier to find for dispersing species.

What does habitat fragmentation mean in the context of human development?

Habitat fragmentation occurs when human activities, such as urbanization and agriculture, break natural landscapes into smaller isolated patches, affecting biodiversity in these fragments.

How can we maintain biodiversity in fragmented habitats?

Biodiversity can be maintained by creating habitat corridors that allow species to move between fragments, increasing immigration rates and supporting metapopulations.

What are metapopulations, and why are they important?

Metapopulations are interconnected populations that have some level of movement between them. They are important because they help maintain biodiversity by reducing local extinction in fragmented habitats.

Why are habitat corridors useful in fragmented landscapes?

Habitat corridors are useful because they provide pathways for species to move between isolated patches, helping to sustain populations and prevent local extinctions.