Island Gigantism

Island gigantism is a biological phenomenon where the size of animals isolated on an island increases dramatically over generations. It is a form of natural selection in which bigger size provides a survival advantage (see Bergmann's Rule ). Large size in Herbivore s usually makes it harder to escape or hide from predators, but on islands, these are often lacking. Thus, island gigantism is not an evolutionary trend due to fundamentally new parameters determining fitness (as in Island Dwarfing ), but rather the removal of constraints. With the arrival of humans and associated predators (dogs, cats, rats, pigs), many giant island endemics have become Extinct . As opposed to island dwarfing, island gigantism is found in most major Vertebrate groups and in Invertebrates .

EXAMPLES

Examples of island gigantism include:

Mammal s

Rodents

--- Giant Rabbit s and Shrew s from Mediterranean islands (extinct)

--- Flores Giant Rat s

--- Giant Hutia s from the West Indies (extinct)

--- Majorcan Giant Dormouse and Minorcan Giant Dormouse (extinct)

Primates

---the extinct giant Lemur genera '' Archaeoindris , Palaeopropithecus '' and '' Megaladapis '' of Madagascar (strictly speaking, Madagascar is not an island but a mini-continent in the context of Biogeography )

Bird s

Ratites

---the Elephant Bird , the world's largest bird, formerly living on Madagascar (extinct)

---the extinct Moa of New Zealand .

Waterfowl

--- Moa-nalo s, extinct giant ducks from Hawai'i .

Wildfowl

---'' Sylviornis Neocaledoniae '' a huge extinct Megapode -like bird from New Caledonia

---some extinct Polynesia n megapodes.

Rails

---the Takahe from New Zealand and related species from Melanesia and Polynesia .

Seabirds

---the extinct Spectacled Cormorant from Bering Island .

Pigeons

--- Dodo and Rodrigues Solitaire from the Mascarenes

---the extinct flightless Viti Levu Giant Pigeon .

Birds of prey

--- the extinct Haast's Eagle and Eyles' Harrier of New Zealand.

Parrots

---the extinct Broad-billed Parrot from Mauritius, an undescribed huge extinct parrot from Easter Island , and the Kakapo of New Zealand.

Reptiles

Turtles

--- Giant Tortoise s on the Seychelles , Galápagos Islands and formerly the Mascarenes

Lizards

--- Komodo Dragon , a rare example of a giant insular carnivore (Islands tend to offer limited food and territories, thus island carnivores are usually smaller in size than continental ones)

--- San Esteban Chuckwalla (''Sauromalus varius'') of islands off Baja California

---'' Leiolopisma Mauritiana '' and '' Macroscincus Coctei '', two extinct Skink s from Mauritius and Cape Verde , and the rare New Caledonian skink '' Phoboscincus Bocourti ''

--- the extinct Rodrigues Giant Day Gecko and New Zealand Giant Gecko , and the extant New Caledonian Giant Gecko

Insects

Madagascar Hissing Cockroach

St. Helena Earwig

Conant's Giant Nihoa Tree Cricket

Lord Howe Island Phasmid

Giant Weta of New Zealand

Flora

Megaherb

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Island Gigantism