Evolutionarily Distinct and Globally Endangered (EDGE) species are threatened species that have few or no close relatives on the tree of life. EDGE species are usually extremely distinct in the way they look, live and behave as well as in their genetic make-up. If they disappear, there will be nothing like them left on the planet.
How to Identify an EDGE Species
Every species in a particular taxonomic group (e.g. mammals or amphibians) is scored according to the amount of unique evolutionary history it represents (Evolutionary Distinctiveness, or ED), and its conservation status (Global Endangerment, or GE). These scores are used to identify EDGE species.
Evolutionarily Distinct
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 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. A phylogeny is a diagram showing how all the species in a particular taxonomic group are related to one another.
In the example phylogeny below, species A would have 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 disproportionate amount of unique evolutionary history would be lost forever. Assuming that resources for conservation are limited and each species is equally threatened, it is therefore reasonable to give priority to species A.
The world’s most Evolutionarily Distinct mammal is the aardvark. The most distinct amphibian is the Mexican burrowing toad.
Follow the links to view the world’s most Evolutionarily Distinct mammals, amphibians and corals.
Globally Endangered
Globally Endangered (GE) scores for each species are based on the IUCN Red List Categories (Critically Endangered, Endangered, Vulnerable, Near Threatened and Least Concern). The IUCN Red List of Threatened Species is the world's most comprehensive assessment of the conservation status of plant and animal species. Species which are Critically Endangered receive a higher score than less threatened species, which in turn, receive a higher score than those not currently in danger of extinction.
Download the EDGE scientific paper to find out more about how EDGE scores are calculated.
EDGE Scores
The ED and GE scores are combined to produce an overall EDGE score for each species. EDGE scores are calculated by multiplying ED and GE together. In mathematical terms, EDGE scores are an estimate of the expected loss of evolutionary history per unit time.
Follow the links to find out more about the top 100 EDGE mammals and amphibians, and the top EDGE corals.
EDGE Species
EDGE species are species that have an above average ED score and are also threatened with extinction (Critically Endangered, Endangered or Vulnerable on the IUCN Red List). There are currently 502 EDGE mammal species (~9% of the total) and 799 EDGE amphibian species (~%14 of the total). Potential EDGE species are those with high ED scores but whose conservation status is unclear.Follow the links to view potential EDGE mammals, amphibians and corals.
Focal Species
Many EDGE species are not being adequately protected by existing conservation measures. This suggests that a disproportionate amount of evolutionary history is likely to be lost in the near future. To redress this balance, we have initiated projects for a subset of top 100 EDGE species.
Follow the links to view the Focal EDGE mammals, amphibians and corals.
Updating EDGE Lists
EDGE lists are updated as soon as possible following the publication of new data on species' threat status or evolutionary relationships. The EDGE mammals list was originally launched in 2007 but was updated in 2010, following the Global Mammal Assessment and the 2009 publication of an updated mammal supertree. Both datasets affected the EDGE scores. The EDGE mammals list was updated a second time in 2011 when the methods were adapted to incorporate polytomy uncertainty into ED score generation .
Download the EDGE scientific paper to find out more about how EDGE scores are calculated.
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Learn more about:
EDGE Mammals
EDGE Amphibians
EDGE Coral Reefs
