page_title: Island ecology
section_title: Speciation
hierarchical_section_title: Island ecology / Ecological processes on islands / Speciation
context_page_description: Island ecology is the study of island organisms and their interactions with each other and the environment. Islands account for nearly 1/6 of earth’s total land area, yet the ecology of island ecosystems is vastly different from that of mainland communities. Their isolation and high availability of empty niches lead to increased speciation. As a result, island ecosystems comprise 30% of the world’s biodiversity hotspots, 50% of marine tropical diversity, and some of the most unusual and rare species. Many species still remain unknown.
  The diversity of species on islands is highly impacted by human activities such as deforestation and introduction of the exotic species. In response, ecologists and managers are directing attention towards conservation and restoration of island species. Because they are simple systems, islands provide an opportunity to study processes of extinction that can be extrapolated to larger ecosystems.
context_section_description: The formation of new islands and their isolation from the mainland provides many unoccupied niches for species to adapt to.  Since immigration of predators and competitors is limited, many organisms are able to persist in these new niches.  This results in a high occurrence of endemism, where species are unique to a localized area.  For example, 50% of endemic bird areas are found on islands.
  
  Endemism is often the result of adaptive radiation.  Adaptive radiation is when a single specie colonizes an area and rapidly diversifies to fill all of the available niches.  A common example is the assemblage of finch species documented by Charles Darwin in the Galapagos Islands.  Darwin’s finches exhibited adaptive radiation by evolving different beak sizes to exploit the diversity of seeds present on the different islands.  
  Because the distributions of these populations are limited by their island habitats, they tend to have fewer individuals than their mainland counterparts and lower genetic variation.  This, along with the behavioral and ecological factors mentioned above, makes island species more vulnerable to extinction.
caption: The palila, one of several endangered honeycreepers that evolved through adaptive radiation and are endemic to the Hawaiian Islands.
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