EDGE species
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Evolutionarily Distinct and Globally Endangered (EDGE) species are
Some EDGE species, such as
The
Calculating EDGE Scores
ED
Some species are more distinct than others because they represent a larger amount of unique evolution. Species like the
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 | Code | GE score |
---|---|---|
Extinct | EX | — |
Extinct in the wild | EW | — |
Critically endangered |
CR | 4 |
Endangered | EN | 3 |
Vulnerable | VU | 2 |
Near threatened |
NT | 1 |
Least concern |
LC | 0 |
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)
References
- ^ Gulf of California Harbor Porpoise/ Vaquita/ Cochito/ (Phocoena sinus). (2012). National Oceanographic and Atmospheric Administration Office of Protected Resources.
- PMID 17375184.
- ^ "Focal Species". EDGE of Existence. Retrieved 2019-12-12.