Question

Why do small islands that are distant from a mainland tend to have fewer plant species than large islands that are close to a mainland?

1) Distant islands are colonized more often by non-native plants that outcompete native plants.
2) Distant islands are harder to get to and require specialized seed dispersal strategies.
3) Small islands may have fewer types of plant habitats than large islands.
4) Small islands support smaller plant populations that are more prone to extinction.
5) Small islands are more often round-shaped which gives them a higher ratio of edge habitat for plants.

Answer 1

Small islands that are distant from a mainland tend to have fewer plant species than large islands that are close to a mainland due to several factors, including colonization by non-native plants, difficulty in seed dispersal, limited variety of plant habitats, smaller plant populations prone to extinction, and a higher ratio of edge habitat on small islands.

Step-by-step explanation:

The reason why small islands that are distant from a mainland tend to have fewer plant species than large islands that are close to a mainland can be attributed to several factors:

1. Distant islands are colonized more often by non-native plants that outcompete native plants. When islands are far from a mainland, they are more likely to receive seeds or spores of non-native plants through long-distance dispersal mechanisms such as wind, water currents, or birds. These non-native plants, being free from the natural predators and competitors of their native habitat, can quickly colonize the new island and outcompete native plants for resources, leading to a decrease in plant diversity.
2. Distant islands are harder to get to and require specialized seed dispersal strategies. Islands that are far from a mainland may lack easily accessible means of propagule (seed, spore, or other reproductive structures) dispersal. Many plant species rely on animals or other agents for seed dispersal, and if these agents are unable to reach the distant island, it limits the establishment of new plant species, resulting in lower plant diversity.
3. Small islands may have fewer types of plant habitats than large islands. Large islands typically have a greater variety of habitats, such as forests, grasslands, wetlands, and coastal areas. These diverse habitats provide different ecological niches that can support the existence of a wider range of plant species. In contrast, small islands may have fewer types of habitats, limiting the number of plant species that can thrive in the available environments.
4. Small islands support smaller plant populations that are more prone to extinction. Small islands generally have limited land area, which restricts the availability of suitable habitats for plants. This results in smaller plant populations that are more vulnerable to environmental disturbances or random events, such as storms or disease outbreaks, leading to a higher probability of extinction.
5. Small islands are more often round-shaped which gives them a higher ratio of edge habitat for plants. Small islands tend to have a higher ratio of edge habitat compared to their total land area. Edge habitats, where two different ecosystems meet, can provide unique conditions that support plant survival and growth. The higher proportion of edge habitat on small islands may contribute to the presence of certain plant species that are adapted to these specific conditions, while limiting the establishment of species that prefer interior habitats.