Situation in which a species or other taxonomic group (see classification; taxonomy) is restricted to a particular geographic region, due to factors such as isolation or response to soil or climatic conditions. Such a taxon is said to be endemic to that region. The size of the region in this context will usually depend on the status of the taxon: thus a family will be endemic to a much larger area than a species, all other things being equal. Reference is frequently made to ‘narrow endemics’, i.e. taxa with markedly restricted ranges. Some of these are evolutionary relics, such as the maidenhair tree (Ginkgo biloba), the only surviving species of the Ginkgoales, confined to Chekiang Province, China, where it was discovered in 1758.