EDGE species

Evolutionarily Distinct and Globally Endangered (EDGE) species represent a disproportionate amount of unique evolutionary history. They have few close relatives, are often the only surviving member of their genus, and sometimes the last surviving genus of their evolutionary family. 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) 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. Recent research indicates that 70% of the world’s most threatened and evolutionarily distinct mammal species are currently receiving little or no conservation attention. If these species are not highlighted and conserved we will not only lose many of the world’s unique species and a disproportionate amount of biodiversity, but we may also greatly reduce the potential for future evolution. The Zoological Society of London (ZSL) has launched a new global conservation initiative, the EDGE of Existence Programme to raise awareness and funds for the conservation of these species.

Every species is given a score according to the amount of unique evolutionary history it represents, and its conservation status. These scores are used to identify EDGE species.

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.

In the phylogeny shown on the right, 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 disproportionate amount of unique evolutionary history would be lost forever.

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