EDGE species

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Evolutionarily Distinct and Globally Endangered (EDGE) species are animal species which have a high 'EDGE score', a metric combining endangered conservation status with the genetic distinctiveness of the particular taxon. Distinctive species have few closely related species, and EDGE species are often the only surviving member of their genus or even higher taxonomic rank. The extinction of such species would therefore represent a disproportionate loss of unique evolutionary history and biodiversity.

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Some EDGE species, such as elephants and pandas, are well-known and already receive considerable conservation attention, but many others, such as the vaquita (the world's rarest cetacean) [1] the bumblebee bat (arguably the world's smallest mammal) and the egg-laying long-beaked echidnas, are highly threatened yet remain poorly understood, and are frequently overlooked by existing conservation frameworks. [2]

The Zoological Society of London launched the EDGE of Existence Programme in 2007 to raise awareness and funds for the conservation of these species. As of 2019, the programme has awarded 97 fellows funds to help conserve 87 different species in over 40 countries.

Calculating EDGE Scores

ED

In this phylogenetic tree, species A has a higher ED score than either species B or C -- it represents a branch rather than a twig on the tree of life. If species A were to go extinct, there would be no similar species left on the planet and a larger amount of unique evolutionary history would be lost forever. Edge tree.png
In this phylogenetic tree, species A has a higher ED score than either species B or C — it represents a branch rather than a twig on the tree of life. If species A were to go extinct, there would be no similar species left on the planet and a larger amount of unique evolutionary history would be lost forever.

Some species are more distinct than others because they represent a larger amount of unique evolution. Species like the aardvark have few close relatives and have been evolving independently for many millions of years. Others like the domestic dog originated only recently and have many close relatives. Species uniqueness can be measured as an 'Evolutionary Distinctiveness' (ED) score, using a phylogeny, or evolutionary tree. ED scores are calculated relative to a clade of species descended from a common ancestor. The three clades for which the EDGE of Existence Programme has calculated scores are all classes, namely mammals, amphibians, and corals.

The phylogenetic tree has the most recent common ancestor at the root, all the current species as the leaves, and intermediate nodes at each point of branching divergence. The branches are divided into segments (between one node and another node, a leaf, or the root). Each segment is assigned an ED score defined as the timespan it covers (in millions of years) divided by the number of species at the end of the subtree it forms. The ED of a species is the sum of the ED of the segments connecting it to the root. Thus, a long branch which produces few species will have a high ED, as the corresponding species are relatively distinctive, with few close relatives. ED metrics are not exact, because of uncertainties in both the ordering of nodes and the length of segments.

GE

GE is a number corresponding to a species' conservation status according to the International Union for Conservation of Nature with more endangered species having a higher GE:

Conservation status CodeGE score
Extinct EX
Extinct in the wild EW
Critically endangered CR4
Endangered EN3
Vulnerable VU2
Near threatened NT1
Least concern LC0
Data deficient DD
Not evaluated NE

EDGE

The EDGE score of a species is derived from its scores for Evolutionary Distinctness (ED) and for Globally Endangered status (GE) as follows:

This means that a doubling in ED affects the EDGE score almost as much as increasing the threat level by one (e.g. from 'vulnerable' to 'endangered'). EDGE scores are an estimate of the expected loss of evolutionary history per unit time.

EDGE species are species which have an above average ED score and are threatened with extinction (critically endangered, endangered or vulnerable). There are currently 564 EDGE mammal species (≈12% of the total). Potential EDGE species are those with high ED scores but whose conservation status is unclear (data deficient or not evaluated).

Focal species

Focal species are typically selected from the priority EDGE species —the top 100 amphibians, birds, mammals and reptiles, top 50 sharks and rays, and top 25 corals— however, they also prioritise species outside these rankings. Such species can also have a very high ED but fall outside the top 100 EDGE rankings. These species are conserved by 'EDGE Fellows', who collect data on these species and develop conservation action plans. [3]

Top 20 2019/20 focal species

Numbers refer to EDGE rank

1. Largetooth sawfish (Pristis pristis)
2. Attenborough’s long-beaked echidna ( Zaglossus attenboroughi )
3. Chinese giant salamander ( Andrias davidianus )
4. Green sawfish ( Pristis zijsron )
5. Purple frog ( Nasikabatrachus sahyadrensis )
6. Seychelles palm frog ( Sooglossus pipilodryas )
7. Thomasset's Seychelles frogs ( Sooglossus thomasseti )
8. Hispaniolan solenodon ( Solenodon paradoxus )
9. Chinese crocodile lizard ( Shinisaurus crocodilurus)
10. Bengal florican (Houbaropsis bengalensis)
11. Black rhinoceros ( Diceros bicornis)
12. Mountainous star coral ( Orbicella faveolata)
13. Ganges river dolphin ( Platanista gangetica)
14. Bactrian camel ( Camelus ferus)
15. Philippine eagle ( Pithecophaga jefferyi)
16. Northern Darwin’s frog ( Rhinoderma rufum)
17. Hawksbill turtle ( Eretmochelys imbricata)
18. Gharial ( Gavialis gangeticus)
19. Chinese pangolin ( Manis pentadactyla)
20. Togo slippery frog ( Conraua derooi)

Related Research Articles

Porpoise Small cetacean of the family Phocoenidae

Porpoises are a group of fully aquatic marine mammals, similar in appearance to a dolphin, all of which are classified under the family Phocoenidae, parvorder Odontoceti. They are, however, more closely related to narwhals and belugas than to the true dolphins. There are seven extant species of porpoise, all among the smallest of the toothed whales. Porpoises are recognised from dolphins by their flattened, spade-shaped teeth distinct from the conical teeth of dolphins, and lack of a pronounced beak, although some dolphins also lack a pronounced beak. Porpoises, and other cetaceans, belong to the clade Cetartiodactyla with even-toed ungulates, and their closest living relatives are the hippopotamuses, having diverged from them about 40 million years ago.

Cuban solenodon Species of mammal

The Cuban solenodon, or almiquí, is a species of eulipotyphlan endemic to Cuba. It is the only species in the genus Atopogale. It belongs to the family Solenodontidae along with a similar species, the Hispaniolan solenodon. The solenodon is unusual among mammals in that its saliva is venomous.

Solenodon Family of mammals

Solenodons are venomous, nocturnal, burrowing, insectivorous mammals belonging to the family Solenodontidae. The two living solenodon species are the Cuban solenodon, and the Hispaniolan solenodon. Threats to both species include habitat destruction and predation by non-native cats, dogs, and mongooses, introduced by humans to the solenodons' home islands to control snakes and rodents.

Sawfish Family of fishes

Sawfish, also known as carpenter sharks, are a family of rays characterized by a long, narrow, flattened rostrum, or nose extension, lined with sharp transverse teeth, arranged in a way that resembles a saw. They are among the largest fish with some species reaching lengths of about 7–7.6 m (23–25 ft). They are found worldwide in tropical and subtropical regions in coastal marine and brackish estuarine waters, as well as freshwater rivers and lakes. They are also endangered.

Sooglossidae Family of amphibians

The Seychelles frogs (Sooglossidae) are a family of frogs found on the Seychelles Islands. Until recently, this family was believed to include the genera Sechellophryne, Nesomantis and Sooglossus, but following a major revision of amphibians in 2006, the genus Nesomantis was named a junior synonym of Sooglossus. Their closest relatives are the purple frogs (Nasikabatrachidae) of India.

Threatened fauna of Australia

Threatened fauna of Australia are those species and subspecies of birds, fish, frogs, insects, mammals, molluscs, crustaceans and reptiles to be found in Australia that are in danger of becoming extinct. This list is the list proclaimed under the Australian federal Environment Protection and Biodiversity Conservation Act 1999. The classifications are based on those used by the World Conservation Union (IUCN), however IUCN and Australian rankings do differ. Each state and territory has its own legislation relating to environmental protection]].

Ghost frog Family of amphibians

Heleophrynidae is a family of frogs, commonly known as ghost frogs. The family consists of two genera, Heleophryne and Hadromophryne, with seven species. Ghost frogs live in swift-moving mountain streams in South Africa. The common name of "ghost frogs" may have been coined because of their occurrence in Skeleton Gorge.

Sir Davids long-beaked echidna Species of monotreme

Sir David's long-beaked echidna, also known as Attenborough's long-beaked echidna or the Cyclops long-beaked echidna, is one of the three species from the genus Zaglossus that occurs in New Guinea. It is named in honour of Sir David Attenborough, the eminent naturalist. It lives in the Cyclops Mountains, which are near the cities of Sentani and Jayapura in the Indonesian province of Papua.

Eastern long-beaked echidna Species of monotreme

The eastern long-beaked echidna, also known as Barton's long-beaked echidna, is one of three species from the genus Zaglossus to occur in New Guinea. It is found mainly in the eastern half at elevations between 2,000 and 3,000 metres.

Hispaniolan solenodon Species of mammal endemic to Hispaniola

The Hispaniolan solenodon, is a solenodon endemic to the Caribbean island of Hispaniola. It was first described by Johann Friedrich von Brandt in 1833. A similar but smaller species, Marcano's solenodon (S. marcanoi), once lived on the island, but became extinct after European colonization. Along with the often sympatric Hispaniolan hutia, it is one of two extant native land mammals on Hispaniola.

Largetooth sawfish Species of cartilaginous fish

The largetooth sawfish is a species of sawfish, family Pristidae. It is found worldwide in tropical and subtropical coastal regions, but also enters freshwater. It has declined drastically and is considered critically endangered.

Smalltooth sawfish Species of cartilaginous fish

The smalltooth sawfish is a species of sawfish in the family Pristidae. It is found in shallow tropical and subtropical waters in coastal and estuarine parts of the Atlantic. Reports from elsewhere are now believed to be misidentifications of other species of sawfish. It is a critically endangered species that has disappeared from much of its historical range.

Longcomb sawfish Species of cartilaginous fish

The longcomb sawfish, narrowsnout sawfish or green sawfish is a species of sawfish in the family Pristidae, found in tropical and subtropical waters of the Indo-West Pacific. It has declined drastically and is now considered a critically endangered species.

Chile Darwins frog Species of amphibian

The Chile Darwin's frog, also called the northern Darwin's frog, is one of only two members of the family Rhinodermatidae. It is endemic to central Chile, although it might well be extinct.

EDGE of Existence programme

The EDGE of Existence programme is a research and conservation initiative that focuses on species deemed to be the world’s most "Evolutionarily Distinct and Globally Endangered" (EDGE). Developed by the Zoological Society of London (ZSL), the programme aims to raise awareness of these species, implement targeted research and conservation actions to halt their decline, and to train in-country conservationists to protect them.

Rondo dwarf galago Species of primate

The Rondo dwarf galago or Rondo bushbaby is a species of primate in the family Galagidae. The dwarf galagos are the smallest members of the genus Galagoides. It weighs less than 100 grams, making it the smallest known galago. It is endemic to Tanzania where its natural habitat is subtropical or tropical dry forests. It lives in an area reported in 2012 to be less than 100 square kilometers and is threatened by habitat loss due to logging. While it was discovered in the 1950s, the Rondo dwarf galago was deemed data deficient until 1996. In 1996, the Rondo bushbaby was fully described as a species. It is now listed as one of "The World's 25 Most Endangered Primates." In 2010, it was also added to the Zoological Society of London's list of genetically distinct and endangered mammals.

<i>Pristis</i> Genus of cartilaginous fishes

Pristis is a genus of sawfish of the family Pristidae. These large fish are found worldwide in tropical and subtropical regions in coastal marine waters, estuaries, and freshwater lakes and rivers. Sawfish have declined drastically and all species are considered seriously threatened today.

Wildlife of the Philippines Flora and fauna of the Philippines

The wildlife of the Philippines includes a significant number of endemic plant and animal species. The country's surrounding waters reportedly have the highest level of marine biodiversity in the world. The Philippines is considered one of the seventeen megadiverse countries as well as global biodiversity hotspot. In the 2000 Red List of the International Union for the Conservation of Nature and Natural Resources (IUCN), 418 of the country's 52,177 species were listed as threatened.

Wildlife of Haiti

The wildlife of Haiti is important to the country because of its biodiversity. According to the World Conservation Monitoring Centre, Haiti is considered to be "one of the most biologically significant countries of the West Indies". With an estimated 5,600 plant species on the island of Hispaniola, some of which only occur in Haiti, 36% are considered as endemic to the island. A mountainous area country, it is situated in the western three-eighths of Hispaniola and shares a border with the Dominican Republic. There are nine life zones, from low desert to high cloud forests, as well as four mountain ranges, and hundreds of rivers and streams and the coral reefs in the seas that surround the islands. Issues of environmental damage, expanding population, deforesting and erosion are of concern; less than 2% of the original forest remains on account of deforestation. This degradation is traced from the 17th century to 19th century starting with the French colonization of the Haiti and population explosion during the 20th century and for the purpose of forestry and sugar-related industries, degraded the forests. and the environment.

References

  1. Gulf of California Harbor Porpoise/ Vaquita/ Cochito/ (Phocoena sinus). (2012). National Oceanographic and Atmospheric Administration Office of Protected Resources.
  2. Isaac, N. J. B.; Turvey, S. T.; Collen, B.; Waterman, C. (2007). "Mammals on the EDGE: conservation priorities based on threat and phylogeny". PLOS ONE. 2 (3): e296. Bibcode:2007PLoSO...2..296I. doi: 10.1371/journal.pone.0000296 . PMC   1808424 . PMID   17375184.
  3. "Focal Species". EDGE of Existence. Retrieved 2019-12-12.