APES Notes 2.3 - Island Biogeography

Summary

In this video, Mr. Smeads explains the theory of island biogeography, focusing on how island size and proximity to the mainland influence species richness and evolution. Larger islands support more species due to higher ecosystem diversity, while islands closer to the mainland experience easier colonization. The video also covers adaptive radiation, where species evolve rapidly to occupy different ecological niches, as seen in the Galapagos finches. The concepts are illustrated through diagrams and examples, offering a clear understanding of how island biogeography affects species evolution and diversity.

Takeaways

• 🌍 Island biogeography studies the ecological relationships and community structures on both physical islands and figurative habitat islands.
• 🏝️ Larger islands support higher species richness due to greater ecosystem diversity, more food sources, and a larger number of ecological niches.
• 🚢 Islands closer to the mainland have higher species richness because it is easier for colonizers (organisms from the mainland) to migrate there.
• 🔬 Increased genetic diversity results from easier migration to closer islands, making species more resilient to environmental disturbances.
• 📈 There is a positive correlation between island size and species richness: as island size increases, species richness also increases.
• 📉 An inverse relationship exists between the distance from the mainland and species richness: the further an island is from the mainland, the fewer species it will support.
• 🦜 Larger islands can support bigger populations, which are more genetically diverse and less likely to go extinct from disturbances like droughts or hurricanes.
• 🪴 The Galápagos Islands showcase adaptive radiation, where one species rapidly evolves into multiple species to utilize different resources and reduce competition.
• 🔄 Evolution on islands is shaped by limited space and resources, leading to species adapting to narrower ecological roles.
• 🐦 Different bird species on the Galápagos Islands evolved distinct beak sizes to exploit various food resources, illustrating how adaptive radiation supports greater species diversity.

Q & A

What is island biogeography?

Island biogeography is the study of ecological relationships and community structure on islands, both actual islands (land surrounded by water) and figurative islands (habitats surrounded by developed human environments).

How does island size affect species richness?

Larger islands support more total species due to higher ecosystem diversity, which provides more food and habitat sources, and creates more ecological niches for species to fill.

Why does the distance of an island from the mainland affect species richness?

Islands closer to the mainland have higher species richness because it's easier for colonizers to travel to the island, increasing genetic diversity and promoting population growth and resilience.

What is the role of colonizers in island biogeography?

Colonizers are organisms that move from the mainland to an island and establish a population there. Their arrival brings genetic diversity and supports the establishment of species on the island.

How does ecosystem diversity contribute to species richness on islands?

Higher ecosystem diversity on larger islands provides a wider variety of habitats and food sources, supporting a greater number of species with different ecological roles.

What is the relationship between island size and population size?

Larger islands support larger populations, which are more genetically diverse. This makes the populations more resilient to disturbances and less likely to go extinct.

What is adaptive radiation, and how does it relate to island biogeography?

Adaptive radiation is when a single species evolves into several new species to use different resources, reducing competition. This often occurs on islands with diverse microhabitats and limited resources.

How does distance from the mainland create an inverse relationship with species richness?

As the distance from the mainland increases, species richness decreases because fewer species are able to migrate and colonize the more distant islands.

What role do microhabitats play in the evolution of species on islands?

Microhabitats create different environmental conditions and food resources, which lead to the evolution of species with specialized traits, such as different beak sizes in Galapagos finches.

What is the significance of describing trends as positive or inverse relationships in island biogeography?

Describing trends helps in understanding the correlation between variables. For instance, island size has a positive correlation with species richness, while distance from the mainland has an inverse relationship with species richness.