Since the islands of Oceania were never connected by land to a continent, the flora and fauna of the islands originally reached them from across the ocean (though at the height of the last ice age sea levels were much lower than today and many current
seamounts were islands, so some now isolated islands were once less isolated). Once they reached the islands, the ancestors of Oceania's present flora and fauna adapted to life on the islands. Larger islands with diverse ecological niches encouraged floral and faunal
adaptive radiation, whereby multiple species evolved from a common ancestor, each species adapted to a different ecological niche; the various species of
Hawaiian honeycreepers (Family
Drepanididae) are a classic example. Other adaptations to island ecologies include gigantism, dwarfism, and among birds, loss of flight. Oceania has a number of
endemic species; Hawaii in particular is considered a global
center of endemism, with its forest
ecoregions having one of the highest percentages of endemic plants in the world.
Flora Land
plants disperse by several different means. Many plants, mostly ferns and mosses but also some flowering plants, disperse on the wind, relying on tiny spores or feathery seeds that can remain airborne over long distances notably
Metrosideros trees from New Zealand spread on the wind across Oceania. Other plants, notably
coconut palms and
mangroves, produce seeds that can float in salt water over long distances, eventually washing up on distant beaches, and thus
Cocos trees are ubiquitous across Oceania.
Birds are also an important means of dispersal; some plants produce sticky seeds that are carried on the feet or feathers of birds, and many plants produce fruits with seeds that can pass through the digestive tracts of birds.
Pandanus trees are fairly ubiquitous across Oceania. Botanists generally agree that much of the flora of Oceania is derived from the
Malesian Flora of the
Malay Peninsula,
Indonesia, the
Philippines, and
New Guinea, with some plants from Australasia and a few from the
Americas, particularly in Hawaii.
Easter Island has some plants from
South America such as the
totora reed.
Fauna (
Branta sandvicensis), a native goose from
Hawaii Dispersal across the ocean is difficult for most land
animals, and Oceania has relatively few indigenous land animals compared to other realms. Certain types of animals that are ecologically important on the continental realms, like large land
predators and grazing mammals, were entirely absent from the islands of Oceania until humans brought them.
Birds are relatively common, including many
seabirds and some species of land birds whose ancestors may have been blown out to sea by storms. Some birds evolved into flightless species after their ancestors arrived, including several species of
rails. A number of islands have indigenous
lizards, including
geckoes and
skinks, whose ancestors probably arrived on floating rafts of vegetation washed out to sea by storms. With the exception of
bats, which live on most of the island groups, there are few if any indigenous non-marine
mammals in Oceania. ==Impact of settlement==