 | This article includes a list of general references, but it lacks sufficient corresponding inline citations .(May 2021) |
A biogeographic realm is the broadest biogeographic division of Earth's land surface, based on distributional patterns of terrestrial organisms. They are subdivided into bioregions, which are further subdivided into ecoregions. A biogeographic realm is also known as "ecozone", although that term may also refer to ecoregions.
The realms delineate large areas of Earth's surface within which organisms have evolved in relative isolation over long periods of time, separated by geographic features, such as oceans, broad deserts, or high mountain ranges, that constitute natural barriers to migration. As such, biogeographic realm designations are used to indicate general groupings of organisms based on their shared biogeography. Biogeographic realms correspond to the floristic kingdoms of botany or zoogeographic regions of zoology.
From 1872, Alfred Russel Wallace developed a system of zoogeographic regions, extending the ornithologist Philip Sclater's system of six regions. [1]
Biogeographic realms are characterized by the evolutionary history of the organisms they contain. They are distinct from biomes, also known as major habitat types, which are divisions of the Earth's surface based on life form, or the adaptation of animals, fungi, micro-organisms and plants to climatic, soil, and other conditions. Biomes are characterized by similar climax vegetation. Each realm may include a number of different biomes. A tropical moist broadleaf forest in Central America, for example, may be similar to one in New Guinea in its vegetation type and structure, climate, soils, etc., but these forests are inhabited by animals, fungi, micro-organisms and plants with very different evolutionary histories.[ citation needed ]
The distribution of organisms among the world's biogeographic realms has been influenced by the distribution of landmasses, as shaped by plate tectonics over the geological history of the Earth.
The "biogeographic realms" of Udvardy [2] were defined based on taxonomic composition. The rank corresponds more or less to the floristic kingdoms and zoogeographic regions.
The usage of the term "ecozone" is more variable. Beginning in the 1960s, it was used originally in the field of biostratigraphy to denote intervals of geological strata with fossil content demonstrating a specific ecology. [3] In Canadian literature, the term was used by Wiken [4] in macro level land classification, with geographic criteria (see Ecozones of Canada). [4] [5] Later, Schultz [6] would use it with ecological and physiognomical criteria, in a way similar to the concept of biome.
In the Global 200/WWF scheme, [7] originally the term "biogeographic realm" in Udvardy sense was used. However, in a scheme of BBC, [8] it was replaced by the term "ecozone".
The World Wildlife Fund scheme [8] [7] [9] is broadly similar to Miklos Udvardy's system, [2] the chief difference being the delineation of the Australasian realm relative to the Antarctic, Oceanic, and Indomalayan realms. In the WWF system, the Australasia realm includes Australia, Tasmania, the islands of Wallacea, New Guinea, the East Melanesian Islands, New Caledonia, and New Zealand. Udvardy's Australian realm includes only Australia and Tasmania; he places Wallacea in the Indomalayan Realm, New Guinea, New Caledonia, and East Melanesia in the Oceanian Realm, and New Zealand in the Antarctic Realm.
| Biogeographic realm | Area | Lands included | |
|---|---|---|---|
| million square kilometres | million square miles | ||
| Palearctic | 54.1 | 20.9 | The bulk of Eurasia and North Africa. |
| Nearctic | 22.9 | 8.8 | Greenland and most of North America. |
| Afrotropic | 22.1 | 8.5 | Trans-Saharan Africa, Madagascar and Arabia. |
| Neotropic | 19.0 | 7.3 | South America, Central America, the Caribbean, South Florida and the Falkland Islands. |
| Australasia | 7.6 | 2.9 | Australia, Melanesia, New Zealand, Lesser Sunda Islands, Sulawesi and the neighbouring islands. The northern boundary of this zone is known as the Wallace Line. |
| Indomalaya | 7.5 | 2.9 | The Indian subcontinent, Southeast Asia, southern China and most of the Greater Sunda Islands. |
| Oceania | 1.0 | 0.39 | Polynesia (except New Zealand), Micronesia, and the Fijian Islands. |
| Antarctic | 0.3 | 0.12 | Antarctica, Alexander Island, South Georgia and the South Sandwich Islands. |
The Palearctic and Nearctic are sometimes grouped into the Holarctic realm.
Following the nomenclatural conventions set out in the International Code of Area Nomenclature, Morrone [10] defined the next biogeographic kingdoms (or realms) and regions:
The applicability of Udvardy scheme [2] to most freshwater taxa is unresolved. [11]
The drainage basins of the principal oceans and seas of the world are marked by continental divides. The grey areas are endorheic basins that do not drain to the ocean.[ citation needed ]
According to Briggs [13] and Morrone: [14]
According to the WWF scheme: [15]
A biome is a distinct geographical region with specific climate, vegetation, and animal life. It consists of a biological community that has formed in response to its physical environment and regional climate. Biomes may span more than one continent. A biome encompasses multiple ecosystems within its boundaries. It can also comprise a variety of habitats.
An ecoregion is an ecologically and geographically defined area that is smaller than a bioregion, which in turn is smaller than a biogeographic realm. Ecoregions cover relatively large areas of land or water, and contain characteristic, geographically distinct assemblages of natural communities and species. The biodiversity of flora, fauna and ecosystems that characterise an ecoregion tends to be distinct from that of other ecoregions. In theory, biodiversity or conservation ecoregions are relatively large areas of land or water where the probability of encountering different species and communities at any given point remains relatively constant, within an acceptable range of variation . Ecoregions are also known as "ecozones", although that term may also refer to biogeographic realms.
The Nearctic realm is one of the eight biogeographic realms constituting the Earth's land surface.
The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropical terrestrial ecoregions of the Americas and the entire South American temperate zone.
Biogeography is the study of the distribution of species and ecosystems in geographic space and through geological time. Organisms and biological communities often vary in a regular fashion along geographic gradients of latitude, elevation, isolation and habitat area. Phytogeography is the branch of biogeography that studies the distribution of plants. Zoogeography is the branch that studies distribution of animals. Mycogeography is the branch that studies distribution of fungi, such as mushrooms.
The Palearctic or Palaearctic is the largest of the eight biogeographic realms of the Earth. It stretches across all of Eurasia north of the foothills of the Himalayas, and North Africa.
The Australasian realm is one of eight biogeographic realms that is coincident with, but not the same as, the geographical region of Australasia. The realm includes Australia, the island of New Guinea, and the eastern part of the Indonesian archipelago, including the island of Sulawesi, the Moluccas, and the islands of Lombok, Sumbawa, Sumba, Flores, and Timor, often known as the Lesser Sundas.
A marine ecoregion is an ecoregion, or ecological region, of the oceans and seas identified and defined based on biogeographic characteristics.
Zoogeography is the branch of the science of biogeography that is concerned with geographic distribution of animal species.
The following outline is provided as an overview of and topical guide to ecology:
The Western Palaearctic or Western Palearctic is part of the Palaearctic realm, one of the eight biogeographic realms dividing the Earth's surface. Because of its size, the Palaearctic is often divided for convenience into two, with Europe, North Africa, northern and central parts of the Arabian Peninsula, and part of temperate Asia, roughly to the Ural Mountains forming the western zone, and the rest of temperate Asia becoming the Eastern Palaearctic. Its exact boundaries differ depending on the authority in question, but the Handbook of the Birds of Europe, the Middle East, and North Africa: The Birds of the Western Palearctic (BWP) definition is widely used, and is followed by the most popular Western Palearctic checklist, that of the Association of European Rarities Committees (AERC). The Western Palearctic realm includes mostly boreal and temperate climate ecoregions.
All of the animals living in Asia and its surrounding seas and islands are considered the fauna of Asia. Since there is no natural biogeographic boundary in the west between Europe and Asia, the term "fauna of Asia" is somewhat elusive. Temperate Asia is the eastern part of the Palearctic realm, and its south-eastern part belongs to the Indomalayan realm. Asia shows a notable diversity of habitats, with significant variations in rainfall, altitude, topography, temperature and geological history, which is reflected in its richness and diversity of animal life.
The Western Indo-Pacific is a biogeographic region of the Earth's seas, comprising the tropical waters of the eastern and central Indian Ocean. It is part of the larger Indo-Pacific, which includes the tropical Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia. The Western Indo-Pacific may be classified as a marine realm, one of the great biogeographic divisions of the world's ocean basins, or as a subrealm of the Indo-Pacific.
The Temperate Northern Pacific is a biogeographic region of the Earth's seas, comprising the temperate waters of the northern Pacific Ocean.
Biogeographic classification of India is the division of India according to biogeographic characteristics. Biogeography is the study of the distribution of species (biology), organisms, and ecosystems in geographic space and through geological time. India has a rich heritage of natural diversity. India ranks fourth in Asia and tenth in the world amongst the top 17 mega-diverse countries in the world. India harbours nearly 11% of the world's floral diversity comprising over 17500 documented flowering plants, 6200 endemic species, 7500 medicinal plants and 246 globally threatened species in only 2.4% of world's land area. India is also home to four biodiversity hotspots—Andaman & Nicobar Islands, Eastern Himalaya, Indo-Burma region, and the Western Ghats. Hence the importance of biogeographical study of India's natural heritage.
Temperate Southern Africa is a biogeographic region of the Earth's seas, comprising the temperate waters of southern Africa, where the Atlantic Ocean and Indian Ocean meet. It includes the coast of South Africa and Namibia, and reaches into southern Angola. It also includes the remote islands of Amsterdam and Saint-Paul, to the east in the southern Indian Ocean.
Temperate South America is a biogeographic region of the Earth's seas, comprising the temperate and subtropical waters of South America, including both the Pacific and Atlantic coasts of the continent and adjacent islands. It also includes the remote Gough Island and Tristan da Cunha in the South Atlantic Ocean.