An endemic is an animal or plant that is found nowhere else. Islands are famous for their endemics because the animals and plants found there evolve in isolation, a process that is often accelerated by the 'founder effect' whereby any unusual characteristics of the original founders become widespread in the resultant population.
Endemism in Shetland is relatively rare because the plants and animals found here have all colonised the islands in the last 12,000 years, since the end of the last ice age. This is a relatively short length of time compared to, for example, the Canary Islands or the Galapagos Islands, both of which can boast dozens of endemic species.
There are 22 species and one subspecies of flowering plants which are only found in Shetland, although all bar one of these are dandelion-like plants.
Shetland Mouse-ear ('Edmondston's Chickweed') Cerastium nigrescens
Now recognised as a full species (it was formerly regarded as a subspecies), this plant was discovered by the 11 year-old Thomas Edmondston in 1837. It only grows on Unst, most famously on and around the Keen of Hamar National Nature Reserve on the edge of Baltasound. It grows on one other hill on Unst and was reported on two other hills on the island in the 19th century but not since. In 1993, Dr David Slingsby estimated that about 7000 plants grew on and around the Keen.
Dandelions Taraxacum spp.
Dandelions are one of several groups of plants that produce new species quite readily. Of the 65 different types of dandelion identified in Shetland, three are found nowhere else in the world: Taraxacum geirhildae grows in three sites in west and north Mainland and was first discovered by the eminent botanist W. H. Beeby in 1907, T. serpenticola grows only on Muckle Heog on Unst and was first found by Shetland botanist Walter Scott in 1980, while T. hirsutissimum grows in south Mainland as far as north as Cunningsburgh and was also discovered by Walter Scott, this time in 1968.
Shetland Mouse-ear Hawkweed Pilosella flagellaris bicapitata
This is an endemic Shetland subspecies of another dandelion-like plant which is found rather locally in central Scotland and central England. The Shetland race was found by Walter Scott in 1962 and it is known from three sites: Whiteness, West Burrafirth and Ronas Voe.
Hawkweeds Hieracium spp.
The hawkweeds speciate even more easily than the dandelions and there are many subtly different species, often termed microspecies. There are 18 species which are endemic to Shetland:
H. vinicaule is found mainly around St Magnus Bay on Mainland but also on Yell
H. northroense is found in North Roe and at one site in west Mainland
H. subtruncatum is found at several widespread sites on Mainland
H. dilectum is found at four sites in central and west Mainland
H. pugsleyi is found found at five locations between Yell and south Mainland
H. attenuatifolium is found only at Laxo in central Mainland
H. hethlandiae only grew at Mavis Grind on Mainland but is now extinct in the wild, although some plants survive in cultivation
H. praethulense only grows in north Mainland
H. australius is found around Loch of Cliff on Unst, beside the Wick of Tresta on Fetlar and in north Mainland
H. spenceanum is found in west Mainland
H. difficile is only known from Ocraquoy in south Mainland
H. gratum is found beside the Loch of Cliff on Unst and Whale Firth on Yell
H. breve is only found at Ronas Voe in north Mainland
H. zetlandicum is found in north Mainland and single sites in west and central Mainland
H. klingrahoolense is found in a few sites in central Mainland and on Yell
H. amaurostictum is found only at Semblisetter in west Mainland
H. scottii (named after Shetland botanist Walter Scott) grows near Sandness in west Mainland
H. ronasii only grows beside Ronas Voe in north Mainland
Some of the insects of Shetland have been reasonably well-studied, especially the moths which were the subject of much attention at the end of the 19th century when it was discovered that there were many unusual melanic (dark) forms in the islands. As well as several subspecies or varieties of moths there are two endemic or semi-endemic subspecies of bumblebee. The blackfly Simulium zetlandense was named for science based on a specimen from Shetland and was thought to be endemic, but it is now known to occur in Fennoscandia, while the a tiny weevil Protapion ryei (= Apion reyi ), which feeds on the flowerheads of Red Clover Trifolium pratense, was formerly thought to endemic, but is now believed to be present on other Scottish islands and is regarded as the extreme end of a cline (a gradual change over a long distance) and is, therefore, now regarded as belonging to the species Protapion assimile, a common species throughout Britain.
There are five named subspecies of moths which appear to be good Shetland endemics i.e. they are not found anywhere else in the world and all (or nearly all) of the the individuals in Shetland conform to the characteristics of the named subspecies.
Eupoecilia angustana thuleana
A small tortrid micro-moth which is common in grassy areas on Unst, Yell and Mainland and which flies in June and July It was originally described as a new species. It is much more heavily marked than the nominate subspecies which is found in the rest of Britain.
Red Carpet Xanthorhoe decoloraria hethlandica
A common geometrid moth found throughout the islands, usually recorded at light at night from June to October, but mainly in July and August. The Shetland race is orange-brown in colour and not white and dull red like the subspecies found in the rest of Britain.
Silver-ground Carpet Xanthorhoe montanata shetlandica
A common geometrid moth found throughout the islands, sometimes found flying by day, but most often recorded at light at night. It is particularly common in the northern isles of Shetland. It flies from June to August. The Shetland race is slightly smallerthan the Mainland race, usually with a less distinct bar.
Netted Pug Eupithecia venosata fumosae
A locally frequent moth, found in the vicinity of beaches throughout the islands, wherever the foodplant Sea Campion Silene maritima is found. It flies in May and June but is rarely seen unless traps are run close to beaches, although larvae (caterpillars) are easily found by examining Sea Campion seed pods. The Shetland subspecies is darker than the form on the British Mainland. It is probably endemic to Shetland but moths resembling this race are occasionally found in Orkney.
Grass Rivulet Perizoma albulata subfasciaria
A locally common but probably declining geometrid moth found throughout the islands, except Fair Isle. It is usually seen by day around the food plant Yellow Rattle Rhinanthus minor and is seen from June to August. The Shetland race is smaller and darker than the race found in the rest of Britain.
Four more named subspecies appear to form the majority of the Shetland population, but are also found elsewhere. It may be that populations elsewhere could be best regarded as belonging to different, as yet un-named, subspecies otherwise the subspecies would probably be paraphyletic - in other words, the populations have different origins and do not share a common ancestor - which is not acceptable in modern taxonomics.
Ghost Moth Hepialus humuli thulensis
A common moth found throughout the islands, except Fair Isle. Most males are dark, sometimes exceptionally so, although pale specimens also occur. The species flies from May to August, but mainly July, and it may often be seen flying at dusk in the 'simmer-dim' (summer nights). Larvae (caterpillars) feed on roots, possibly for up to two years, and are frequently dug up in gardens. The moths found in the Faroe Islands are also included in thulensis and it is possible that Faroe was colonised via Shetland, in which case common ancestry is possible. Some moths in Orkney, but only a minority, are as dark as Shetland specimens.
Yellow Shell Camptogramma bilineata atlantica
A frequent, but very local, moth found on on Mainland, Muckle Roe, Fair Isle and Unst. It flies from June to August and may be seen by day or attracted to light. The race atlantica , which is darker and duller yellow than the Mainland British form, is found in Shetland but is also said to occur in the Outer Hebrides; it seems unlikely that these two populations share a common ancestor.
Dark Marbled Carpet Chloroclysta citrata pythonissata
A locally frequent moth throughout the islands, except Fair Isle. It may be seen by day or at light from July to September but mainly in August. The Shetland race is also found in Orkney and, as Shetland was probably colonised via Orkney, common ancestry is likely.
The Exile Apamea zeta [exulis]
A locally common on moorland on Mainland, Muckle Roe and Unst, but there is one undated record from Yell and an unconfirmed record from Fair Isle. It flies in July and early August and is attracted to light or sugar. It was originally thought to be endemic species, Apamea exulis, but was later regarded as being part of a widespread northern European species which includes the Northern Arches Apamea zeta assimilis, which is found in northern Scotland. Most recently, the Shetland population has lost its status as an endemic subspecies and has been treated as the only British population of the widespread Scandinavian subspecies A. z. marmorata. Some authorities, including Dr Svend Kaaber who has seen the species in Denmark, Faroe and Shetland, still believe that the Shetland population deserves subspecific status.
Five more species have named forms which are only found in Shetland (two currently recognised as subspecies), but as these are often found alongside typical individuals and they often only form a small proportion of the population, they can be regarded as no more than forms or varieties. There are, arguably, some other forms which are arguably as distinct as some of these, but without official names.
Map-winged Swift Hepialus fusconebulosa f. zetlandicus
A common moth found throughout the islands, often seen flying at dusk or attracted to light, mainly in June in July but recorded from May to August. The Shetland form, which is bright and variegated, only forms a small proportion of the population and is one of three forms found in the islands.
Garden Carpet Xanthorhoe fluctuata f. thules
A frequent moth throughout the islands and the only Shetland macromoth with a regular second brood. Consequently it can be found from April to September. The Shetland form is a dark, but a melanic form may also found in towns and cities on Mainland Britain and f. thules only forms a small proportion of the population in Shetland.
Twin-spot Carpet Perizoma didymata [hethlandica]
A locally common but declining moth found throughout the islands and flying from July to September. Although still accepted as a named subspecies, browner and duller than the Mainland British race, moths of this form only seem to constitute a small proportion of the Shetland population, so the race is not really valid.
Autumnal Rustic Eugnorisma glareosa f. edda
A common species throughout the islands, usually found at light and recorded in August and September. The dark form edda is also occasionally found outside Shetland but it is commonest in the islands where it increases from less than 5% of the population in the south Mainland to over 95% on Unst.
Ingrailed Clay Diarsia mendica [thulei]
An abundant moth found throughout the islands, from June to October but mainly in July and early August. A highly variable species, moths conforming to the description of the Shetland subspecies form only a tiny part of the population, so the race is not valid.
Small Heath Bumblebee Bombus jonellus vogti
Scarce on moorland on Mainland, Muckle Roe and Unst at least, flying from April to September. The race breeding in Shetland has a yellow tip to the abdomen, rather than the white tip found in most other races.
Shetland Bumblebee Bombus muscorum agricolae
Very common throughout the islands, flying from April to October. It is much more colourful than its mainland British counterpart (which is known as Moss Carder Bee), with a bright orange thorax and a yellow abdomen. It is also said to occur in the Outer Hebrides, but it seems unlikely that these two populations share a common ancestor, so it may be best to separate the populations as different subspecies under the rules of paraphyly.
There are no species of vertebrates (fish, amphibians, reptiles, birds or mammals) which are only found in Shetland, although there are three subspecies of two species of birds and at least three subspecies of one species of mouse. In addition, there are several distinctive Shetland breeds of domestic animals.
Shetland Wren Troglodytes troglodytes zetlandicus
Shetland Wrens are slightly larger and darker than the Wrens found in the rest of Britain or on mainland Europe. They also have louder and more varied songs, which are thought to be an adaptation to help males get heard on boulder beaches, which are one of the favoured habitats in Shetland. When population levels are high birds also breed 'inland', along streams or around areas of bushes (the latter being the typical habitat in the rest of Britain). Shetland Wrens breed throughout the islands except on Out Skerries, where they only breed occasionally, and on Fair Isle, where there is a different subspecies. The only estimate of the breeding population is from the beginning of the 21st century, when there were estimated to be between 1,500 and 3,000 pairs.
Fair Isle Wren Troglodytes troglodytes fridariensis
Fair Isle Wren is not as dark as Shetland Wren, but it is still darker and larger than Wrens found in the rest of Britain or on mainland Europe. The song is also distinct. As it is only found on Fair Isle and nowhere else in the world, the population is tiny, varying between 10 and 50 pairs, nearly all breeding on boulder beaches.
Shetland Starling Sturnus vulgaris zetlandicus
The Shetland Starling is only very slightly different to the Common Starling which breeds over most of the rest of Europe. It has a slightly larger bill and the juveniles are usually very dark. Shetland Starlings breed throughout the islands although birds breeding on Fair Isle are the least distinctive. The only estimate of the breeding population is from the beginning of the 21st century, when there were estimated to be between 10,000 and 20,000 pairs. Birds from the Outer Hebrides have been included in zetlandicus, which would mean this race is not endemic to Shetland, but the most recent analysis concluded that this treatment was not valid and that only Shetland birds should be named zetlandicus.
Shetland Field Mouse Apodemus sylvaticus granti, A. s. thuleo, A. s. fridariensis
This mouse is normally known as the Wood Mouse over most of Britain, but is more appropriately known as the 'Hill Mouse' or 'Field Mouse' in Shetland. Like all terrestrial mammals in Shetland, mice were brought to the islands by humans; in this case accidentally. It was once thought that mice arrived in Shetland with the Vikings, but it is now known that they were here long before this. Shetland Field Mice are larger and darker than mice found in the rest of Britain or on mainland Europe. Shetland Field Mice breed on all islands inhabited by humans. The named subspecies are A. s. granti described from Yell, A. s. thuleo from Foula and A. s. friadriensis from Fair Isle. The races found elsewhere in Shetland are unknown - it is likely that the race described from Yell is found elsewhere but it is possible that new races are awaiting description on other islands.
Domestic animals are subject to more selection pressure than wild animals as they are deliberately selected by man to show certain traits. Nevertheless, the breeds of animals found in Shetland do show adaptations to the Shetland environment.
Shetland Goose - very unusually, the goose is always grey and white and gander is white
Shetland Duck - typically black with a white breast
Shetland Cattle - a small tough breed, in several colour varieties but often black and white
Shetland Sheep - a small tough breed, in several colour varieties but usually white these days
Shetland Pony - the world famous small pony
Shetland Pig - long extinct, but probably most similar to a small Tamworth
Shetland Sheepdog - a debatable breed, the Kennel Club variety probably differing significantly from the dogs that were used in Shetland in the past.