1015 Round-mouthed whorl snail Vertigo genesii
Description and ecological characteristics
The round-mouthed whorl snail Vertigo genesii is a tiny boreal and alpine species. In the UK, it is found in calcareous flushes (e.g. 7230 Alkaline fens) including rich assemblages of local plants, often with an arctic-alpine element, confirming the status of the species as a relict of the fauna and flora of the late glacial period. Post-glacial climatic change and forest growth led to a dramatic contraction of its range, and the small, isolated nature of the sites where it survives makes the populations vulnerable to accidental damage or natural events such as prolonged drought. In general, sites supporting Vertigo genesii are subject to light grazing, but heavy grazing is detrimental to the species. Like all Annex II Vertigo species, it is highly dependent on maintenance of existing local hydrological conditions.
European status and distribution
Vertigo genesii is a boreal and alpine species that is virtually restricted to the Alps and the mountains of central Scandinavia. It is very local throughout its range, and the UK populations are probably at the climatic edge of the species' range.
UK status and distribution
Seven populations of Vertigo genesii are known in the UK. Most of the known populations have been found in two upland regions: Upper Teesdale, in Durham, and the Blair Atholl area in Perthshire. It has also been recorded farther north in Scotland on the Black Isle at the lower altitude of 90 m.
Site selection rationale
The three sites selected for this species contain a high proportion of the total known UK population, and represent the two regions of Britain in which it is found (northern England and central Scotland).
Moor House - Upper Teesdale
Cumbria, Tees Valley and Durham
In Upper Teesdale round-mouthed whorl snail Vertigo genesii lives amongst moss, low-growing sedges and a rich assemblage of rare and local arctic-alpine plants such as bird’s-eye primrose Primula farinosa and Scottish asphodel Tofieldia pusilla. V. genesii is found at a number of base-rich flushes around the slopes of Widdybank Fell and at isolated flushes further east on Cronkley Fell and Holwick Fell, at altitudes between 400 m and 525 m. The snail is locally abundant at some flushes and dominates the molluscan fauna at many of them.
Tulach Hill and Glen Fender Meadows
The round-mouthed whorl snail Vertigo genesii occurs at an altitude of 315–430 m in several base-rich flushes at this central Scottish site. In some of these flushes it has been recorded with another Annex II species, 1013 Geyer’s whorl snail Vertigo geyeri. The flushes contains a rich assemblage of arctic-alpine plants, including false sedge Kobresia simpliciuscula and Scottish asphodel Tofieldia pusilla.
SACs where this Annex II species is a qualifying feature, but not a primary reason for site selection
- Beinn a' Ghlo Eastern Scotland
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