Oceanic islands are much less diverse than otherwise comparable continental ecosystems, and there are well-defined and continuous gradients in population- and species-level diversity among islands as a function of island size, age and distance from source areas. Additionally, many islands (particularly volcanic and coral islands) offer a consistent geological background for studies of ecosystem- and landscape-level diversity. Accordingly, island ecosystems offer unique opportunities for studies evaluating interactions between biological diversity and ecosystem function.
Interactions between biological diversity and ecosystem function could be evaluated in terms of (1) effects of diversity on ecosystem pattern and process near steady state, (2) effects of diversity on ecosystem resistance to, or resilience following, disturbance, and (3) effects of diversity on rates of invasion/extinction, and on their consequences for ecosystem function. Our knowledge has advanced farthest in the third area; there is clear evidence that biological invasions alter whole-ecosystem function substantially on many islands, and there is substantial progress towards understanding the number and consequences of extinctions on oceanic islands.
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