Editing Island (section)

=== Evolution on island groups ===
[[File:Finchadaptiveradiation.png|thumb|[[Adaptive radiation]] of finch A (''[[Geospiza magnirostris]]'') into three other species of finches on the [[Galapagos Islands]]. Due to the absence of other birds, [[Darwin's finches]] adapted to new niches. Their seed-eating beaks evolved to handle foods such as nuts, fruits, and insects.]]
Species that colonize island archipelagos exhibit a specific property known as [[adaptive radiation]]. In this process, a species that arrives on a group of islands rapidly becomes more diverse over time, splitting off into new species or subspecies. A species that reaches an island ecosystem may face little competition for resources, or may find that the resources that they found in their previous habitat are not available. These factors together result in individual evolutionary branches with different means of survival.<ref name=":29">{{Cite web |last=Lovette |first=Irby |date=December 20, 2018 |title=Why Evolution Goes Wild on Islands: The Science of Adaptive Radiation |url=https://www.allaboutbirds.org/news/why-evolution-goes-wild-on-islands-the-science-of-adaptive-radiation/ |access-date=July 13, 2024 |website=All About Birds |language=en-US}}</ref>

The classical example of this is [[Darwin's finches]], a group of up to fifteen [[tanager]] species that are endemic to the Galápagos Islands.<ref>{{Cite journal |last=Sato |first=Akie |date=March 1, 2001 |title=On the Origin of Darwin's Finches |url=https://academic.oup.com/mbe/article/18/3/299/1073209 |access-date=July 13, 2024 |journal=Molecular Biology and Evolution |volume=18 |issue=3 |pages=299–311 |doi=10.1093/oxfordjournals.molbev.a003806|pmid=11230531 }}</ref> These birds evolved different [[beaks]] in order to eat different kinds of food available on the islands. The [[large ground finch]] has a large bill used to crack seeds and eat fruit. The [[Genovesa cactus finch]] prefers [[cacti]] as a food source, and has a beak adapted for removing pulp and flowers from cacti. The [[green warbler-finch]] (in the habit of true [[warbler]] species) consumes spiders and insects that live on plants.<ref name=":29" /> Other examples of this phenomenon exist worldwide, including in Hawaii and Madagascar, and are not limited to island ecosystems.<ref name=":29" />

==== The island rule ====

[[File:Dronte dodo Raphus cucullatus.jpg|alt=A plaster and wax model of a large bird with a beak.|thumb|The extinct [[Dodo]] is an example of island gigantism.]]

Species endemic to islands show a common evolutionary trajectory. [[Foster's rule]] (also known as the island rule), states that small mammals such as [[rodents]] evolve to become larger, known as [[island gigantism]]. One such example is the [[giant tortoise]] of the [[Seychelles]], though it is unknown if it grew in size before or after reaching the island. Larger animals such as the [[hippopotamus]] tend to become smaller, such as in the case of the [[pygmy hippopotamus]]. This is known as [[insular dwarfism]].<ref name=":30">{{Cite web |last=Tyson |first=Peter |date=November 1, 2000 |title=Gigantism & Dwarfism on Islands |url=https://www.pbs.org/wgbh/nova/article/gigantism-and-dwarfism-islands/ |access-date=July 13, 2024 |website=www.pbs.org |language=en-US}}</ref> In the case of smaller animals, it has been hypothesized that animals on islands may have fewer [[predators]] and competitors, resulting in selection pressure towards larger animals. Larger animals may exhaust food resources quickly due to their size, causing [[malnutrition]] in their young, resulting in a selection pressure for smaller animals that require less food. Having fewer predators would mean these animals did not need not be large to survive.<ref name=":30" />