Factors Affecting Island Species Richness

Species richness on islands is influenced by several key ecological factors, primarily explained by the theory of island biogeography. The question asks which factors affect species richness on an island. Let's analyze the given options:

• (a) Area of the island: Larger islands generally support a greater number of species. This is because larger areas can provide more diverse habitats and resources, and can sustain larger populations, reducing the risk of extinction.
• (b) Distance from the mainland: Islands closer to a mainland source typically have higher species richness. This is due to easier colonization rates from the mainland for new species compared to distant islands.
• (c) Shape of the island: While often less emphasized than area and distance, island shape can also play a role. More complex or elongated shapes might increase edge habitat or offer varied microclimates, potentially influencing the number of species that can be supported.

According to the principles of island biogeography, both the physical size (Area) and the isolation (Distance from the mainland) are critical determinants of species richness. The shape of the island can also influence habitat diversity and edge effects, thus contributing to species richness.

Therefore, all three factors—area, distance from the mainland, and shape—can affect the species richness found on an island.

The correct option includes all three factors: (a), (b), and (c).