Characteristics of Island

TDC Part III Paper—VII Group C Definition of Island

 An island is ‘a piece of land surrounded by water’ (Oxford English Dictionary).  Yet continents are also surrounded by water, but due to their large extension, they are not considered islands.  The largest island in the world is Greenland, but Australia, more than three times the size of Greenland, is the smallest continent of our planet.

Archipelago • An archipelago is a group of islands closely scattered in a body of water, usually a sea or ocean, but it can also be a lake or river.

• Indonesia, Andaman and Nicobar Islands, the Galápagos Islands, Japan, the Philippines, Maldives, the Balearic Isles, the Bahamas, the Aegean Islands, Hawaii, the Canary Islands, Malta, the Azores, Canadian Arctic Archipelago, Archipelago Finland) and the Shetland Islands are all examples of well-known archipelagos. Atoll • An atoll is generally ring-shaped and formed by a , island, or several islets which surround a body of water. The word key refers to a small, low island of ancient coral reef. Lagoon

• A lagoon presents a shallow body of water that may have an opening to a larger body of water, but is also protected from it by a sandbar or coral reef.  Fauna is all of the animal life present in a particular region or time. The corresponding term for plants is flora. Flora, fauna and other forms of life such as fungi are collectively referred to as biota.  Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess Shale fauna".  Paleontologists sometimes refer to a sequence of faunal stages, which is a series of rocks all containing similar fossils.  The study of animals of a particular region is called faunistics.  Fauna comes from the name Fauna, a Roman goddess of earth and fertility, the Roman god Faunus, and the related forest spirits called Fauns. All three words are cognates of the name of the Greek god Pan, and panis is the Greek equivalent of fauna.  Fauna is also the word for a book that catalogues the animals in such a manner.  The term was first used by Carl Linnaeus from Sweden in the title of his 1745 work Fauna Suecica. Australian and fauna. This image was likely first published in the first edition (1876–1899) of the Nordisk familjebok Insularity vs Isolation  Insularity, generally, refers to a physical condition of a place surrounded by water, mountains or desert.  Conversely, isolation is understood as a complete separation from other places or people.  Seas for example are sometimes an insuperable obstacle to plants, animals and people.  Isolation can refer to a distant, inaccessible place, as well as to a person or a community living a way of life without, or very limited, contact with other groups, or suffering from contagious disease, quarantine or detention.  Insularity and isolation have effects on biodiversity.  Island has shown that geological processes, colonization and geographical isolation have influenced biodiversity (MacArthur and Wilson, 1967).  The size of island and its distance from the mainland can influence biodiversity too.  Isolation, moreover, reduces the relationship of islands with the mainland, and with it the interchange of species and of dispersal events. Hence islands provide examples where evolution has produced patterns of endemic forms.  However some islands, if sufficiently old and isolated to have generated endemic forms, but close enough to continents, have been able to sustain dynamic interaction with diverse continental landmasses. This is the case of the West Indies and island chains in the Indian Ocean (e.g. , Comoros, and Mascarenes).  Noticeably, islands have developed isolated living communities, whether plant, animal or human, separated from, and differing to varying degrees from, mainland communities of the same kind Islands as ‘laboratories’  The concept of islands as laboratories has been proposed by several authors. Islands as laboratories for evolutionary processes have been recognized since the 19th Century with the works of Darwin on the Galapagos and Wallace in the Malay Archipelago.  Darwin suggested that due to isolation, species would follow an independent evolutionary process compare to their parent species on the mainland.  He showed that among the finches he studied in the Galapagos, most of them were peculiar to the islands, and some specific to particular islands of the Galapagos group, but different from the mainland South American species (Darwin, 1859).  The evolution and extinction of species, and the quantification of the variables involved in the colonization of islands by species, represent the reason for considering islands as laboratories for ecological processes and biogeography. Types of Islands • Islands surrounded by vast stretches of sea support unique fauna depending upon the location of the island and its history of connection and separation from the mainland. • Based upon the geography and history of the islands, they can be grouped into two categories, namely, Continental islands and oceanic islands. 1.Continental Islands • They are located in the continental self and separated from the mainland by sea that is less than 200 m deep. • They connect to the mainland during the ice age when sea level goes down by that measure and provide broad corridor to the animals to migrate. Hence their fauna shows similarities with the mainland fauna and is derived from it. A. Recent continental islands. Examples: Britain, Japan, Tasmania, Sumatra, Java, Borneo, Taiwan and Sri Lanka • The separating sea between the islands and the mainland is less than 200 m deep and they have been repeatedly connected and disconnected to the mainland. B. Ancient continental islands Examples: Madagascar and New Zealand. • They were connected to the mainland in the ancient past, sometime in the Mesozoic period but have never had any connection with the mainland ever since. • Sea separating them from the mainland is very deep and hence even lowering of the sea level during ice age does not connect them to the mainland. Characteristics of Continental islands

 Islands that have been connected with the nearby mainland at one time or other . Through the sinking of the land or by a rise in the sea level they must have become separated from the continent by a stretch of the sea.  The sea, separating the two may be narrow like the straits of Dover which separates the continental islands of Great Britain form the continent of Eurasia or may be wide like the Formosa strait which separates the island of Formosa from mainland China  Are close to the mainland and they resemble each other geologically  Great Britain is a young continental island Borneo, Formosa and Japan are older  The fauna of the continental island as well as the mainland are more or less identical and always include certain proportion of and amphibia.  The terrestrial fauna of the continental island must have reached the island across the dry land when the island was still connected with the continent  The difference that one notices in the faunal content of the island and the mainland depends upon the length of time a continental island has been independent form the mainland  If the island is an old one it will be lacking in animals which are comparatively new comers to mainland and secondly the animals in the island would have undergone extensive adaptive radiation resulting in the production of a wide variety of species unknown in the mainland  Some of the peculiar forms present in the continent islands are mainly due to the evolution of the new forms under changed insular conditions  Sometimes continental islands have preserved some of the species which have become extinct on the mainland  The survival of such forms on the continental islands is due to lack of competition from the more progressive forms and hence they are shielded from the hazardous effects of natural selection 2. Oceanic Islands • Examples: St. Helena, Galapagos, Easter Islands, Fiji, Azores, Bermuda, Mauritius, Seychelles, Tristan da Cunha and Andaman-Nicobar Islands. • They are generally the islands of volcanic origin far away in the sea which never had land connection with the continents. • Strong winds prevail on these islands forcing to become wingless. Islands have very few or no flying insects, because strong winds trans port the insects out to sea. • Flora and fauna is different from the nearest mainland, although some of it may have been derived from there. Freshwater , and mammals are rare or absent. • Most likely mammals on these islands are , rats and . • also have a tendency to become flightless as in the case of Dodo in Mauritius. Some birds of oceanic islands, for example, the , flightless rails, and the Ha waiian cormorant, have lost the ability to fly, and their wings have been reduced . This adaptation is due to the absence of and mammals.

• and turtles have a tendency to become giants as on the Galapagos Islands. Characteristics of Oceanic Islands  Islands which never had a connection with a continent  They may be of volcanic origin or may be formed by the building up of coral reef or by a combination of both methods  They are often far removed from the nearest mainland  The oceanic islands always include a chance assemblage of animals composed of a haphazard collection of diverse animals groups  Invariably the oceanic island fauna is quite conspicuous by the entire absence of terrestrial mammals and amphibians  The fauna of an oceanic island must be derived from across the sea The direction from which the fauna comes will be determined to some extent by the prevailing wind and ocean currents  Only forms which can cross the ocean either by active flight or with high natatory (swimming) capacity or by some means of dispersal such as logs of wood, ice blocks, etc., will be able to reach the oceanic islands colonise them . Birds tend to lose the bright colour of their mainland relatives, evolving into either white or dark forms.  Hence the fauna of an Oceanic island is likely to be poor in basic groups • If introduced by man animals tend to flourish in Oceanic island because of the lack of competition • The Oceanic island differs from the mainland in climate, vegetation and fauna • Animals tend to develop into sizes like the giant of Galapagos and giant found in Galapagos and Seychelles. Large mammals, such as the tamarau and the pony, usually do not reach their fu llest possible development on islands. Island birds and (rails, monitors, turtles) often exhibit insular gigantism.

• The characteristics of island fauna are more sharply expressed on oceanic islan ds that are far from the mainland (for example, Easter Island, the Galápagos Isl ands, Hawaii, and St. Helena). The fauna on such islands is especially meager, because it consists only of animals that originally came from the mainland or fr om the closest islands by air or water. • An absence of mammals, amphibians, and snakes characterizes oceanic islands and old continental islands. • Very intensive species formation occurs on these islands according to the princi ple of adaptive radiation of certain endemic groups (Hawaiian honeycreepers, g round finches of the Galápagos Islands and of Madagascar). Oceanic or Continental? It is not always easy to determine whether an island is Oceanic or Continental. The difficulty is mainly due to the fact that in the ancient islands differences between the two types of faunae disappear or Oceanic island may receive animals by transportation and this may alter the faunal relationships • Galapagos Islands reoffered to as Oceanic islands by Darwin, Wallace, Hesse, Alee and Schmidt while many others regard it as Continental island • New Zealand for example is regarded as Continental island by Wallace while Wlikens, the well known geologist, regards it as Oceanic These environmental difference lead to divergence on the part of the inhabitants when compared with the mainland relatives The islands, among themselves, differ considerably in their climate, vegetation and fauna but have certain common features: A. Vegetation and fauna tend to be sparse, B. Mammals, amphibia and strictly fresh water fishes are totally absent The absence of carnivorous forms leads to certain general trends in the evolution of other island inhabitants From example the birds tend to loose the power of flight, become large and flightless like the Dodo which lived on the island of Mauritius where there were no native mammals • The characteristics of island fauna are less strongly expressed on conti nental islands, including the West Indies, Japan, the Malay Archipelag o, the British Isles, and Sakhalin. • When these islands separated from the mainland, their fauna was alrea dy the same as that of neighboring parts of the mainland; it subsequent ly became more sparse owing to extinction of some species. Species f ormation is less intensive on these islands than on oceanic islands. • Man effects rapid changes in island fauna: the fauna loses its initial fo rm, particularly on oceanic islands. The fauna of certain isolated mainl and areas or areas with unique natural conditions, such as the Crimean Mountains and Kamchatka, has features of island fauna. Fauna of St. HelenaIsland  This is a 10 mile long oceanic island in the south Atlantic ocean and is located 1000 miles west of .  Fauna is poor and sparse. There are no native mammals, reptiles, amphibians and fishes. Sheep were introduced by Portuguese in 1593. African plover is the only resident . Land mollusks include snails, which perhaps have reached here through their eggs carried stuck on the legs of migratory birds. Plants resemble those of , whose seeds must have also been carried by birds. Fauna of Galapagos Islands

 This is a group of 15 oceanic islands located 600 miles west of Ecuador in South America. They are dry and bare, containing thorny bushes and cacti. There are tall trees towards the middle of islands.  There are no freshwater fishes and amphibians. Two species of giant iguana lizards occur, of which one is cactus feeding on land and the other dives in the sea to feed on sea-weed. Tortoises are giant, their shell about a meter in diameter. There are two species of snakes and two species of . Few bird species exist and resemble South American birds. Darwin’s finches are famous for their varied adaptations. There are flightless cormorants and one species of penguin, the only one that managed to come out of Antarctica region. Mammals are represented by bats and rice rats. Fauna of Madagascar • This is an ancient continental island, 260 miles east of Africa and supports dense tropical vegetation. The fauna lacks the variety of Africa. • Mammals. Only 5 mammalian orders are present, namely, Insectivora (one family), Chiroptera (bats), (3 families of Prisemians, lemurs and aye-aye), Rodentia and that is represented by civets. • Birds. There is large number of endemic birds and 4 families are exclusive which include helmet birds, and roteoles. , secretary birds, hornbills, woodpeckers of the mainland • Africa are absent here. • Reptiles. There are , spiny lizards and rough-tailed (Uropeltidae). Agamid and Lacertid lizards, turtles and poisonous snakes are absent. • Amphibia. There are only tree frogs (Polypedatidae) which are shared with Africa but 4 genera are endemic. • Fishes. There are no freshwater fishes here. Fauna of New Zealand  This is an ancient continental island, 1000 miles south-east of Australia.  There is absence of many mainland animals and relics of ancient vertebrates are present.  Mammals. There are no native mammals except 2 families of murid bats which have reached here through flight.  Aves. The flightless birds include kiwi, rails and owl parrot (Kakapo). There is a flesh-eating kea bird that feeds on the kidneys of sheep by making a hole on the back. Giant moas have become extinct recently in 13th century. Flightless goose and wrens are also extinct. Wattle birds are endemic.  Reptilia. The living fossil Sphenodon, commonly called Tuatara exists here. There are no snakes but geckos and are present.  Amphibia. Amphibians are represented by the frog, Liopelma.  Fishes. Strictly freshwater fishes are absent. Fauna of the BritishIslands • This is a group of recent continental islands which got separated from the mainland Europe • about 7000 years ago. • Mammals. There are hedgehogs, shrews, moles, red fox, wild cat, two species of deer that includes • red deer • (Cervus elephas scoticus), hares, one , and bats. However, there are no hamsters, lemmings, bears, ibex, wolves, beavers and reindeers of the mainland. • Aves. Only red grouse (Lagopus) is endemic. Other birds are migratory in nature. • Reptiles. There are 3 species of snakes that include grass snake, adder and smooth snake and two species of lizards (brown and green sand lizard and limbless lizard (Anguis). There are no crocodiles and turtles. • Amphibia. Only 6 species of amphibians are present, namely, 3 species of salamanders, 2 species of toads and one species of frog. • Fishes. Perches, pikes, carps and loaches are present.