The Scottish Biodiversity List: Non-Marine Molluscs

In December 2005 the Scottish Biodiversity List (hereafter referred to simply as the List) was published. This is a “list of flora, fauna and habitats considered to be of principal importance for biodiversity conservation as required by the Nature Conservation (Scotland) Act 2004”. There are in fact four lists: Terrestrial and Freshwater Species; Terrestrial and Freshwater Habitats; Marine Species; and Species and Habitats identified as important by the Scottish public. Needless to say, the Scottish public did not identify any molluscs as important! In addition to these lists, there are various documents explaining how the Scottish Biodiversity List was produced.

For non-marine molluscs, the list was produced essentially by going through the Atlas of the Land and Freshwater Molluscs of Britain and Ireland (Kerney, 1999), and identifying species that were found in five or fewer 10 km squares in Scotland. A few species, such as the freshwater pearl mussel Margaritifera margaritifera are nevertheless included in the List because of the national and international importance of their Scottish populations, although they are found in more than five squares. I was asked to comment on this draft list of non-marine molluscs before publication, and was able to point out some changes since the Atlas was published.

The List as published (which uses the names given in the Atlas, rather than those proposed by Anderson (2005)) is given in Table 1, and includes 21 species. Some are rare throughout Britain, but others are rare only in Scotland, where they are at the limit of their ranges. In addition to the list of rare species, there are lists of “data deficient” and “extinct” species. No non-marine molluscs were put in the data deficient category.

A few species require further comment, either because of differences from the Atlas data, or because they could perhaps have been put in a different category. Most slugs of the Arion hortensis complex recorded in Scotland are actually A. distinctus and A. owenii, with very few A. hortensis s.s.. However, in view of the relatively recent separation of these species, and the small number of people investigating them, I would have been inclined to put A. hortensis in the “data deficient” category of the List.

Candidula gigaxii is represented in the Atlas by a single record from 1930, and thus might have been placed in the “extinct” category; however, I rediscovered it a few years ago (Kerney, 2002), and it seems to be holding its own along the coast at and near North Berwick. The mud snail Lymnaea glabra is the subject of a Scottish Action Plan (Macadam, 2005). Although the Atlas shows only four modern Scottish sites, the total has now been increased to at least nine by the Mud Snail Study Group. Because of its conservation interest, and the vulnerability of its habitats, however, it still seems appropriate to include it on the List.

Truncatellina cylindrica is only represented by old records in the Atlas, but was recently discovered by Gordon Corbet living in Fife on the north side of the Firth of Forth (Kerney, 2001).

The consultation process also allowed species to be removed from the draft list. Bithynia leachii is shown in the Atlas as being present in only two 10 km squares in Scotland, but my recent studies (Sumner, 2006, in press) have shown it to be widespread in the Forth & Clyde and Union Canals, as well as in Strathclyde Loch near Motherwell, so that it has now been recorded in at least twelve 10 km squares and thus no longer qualifies for the List.

Three species of non-marine molluscs are regarded as extinct in Scotland. Of these, Helicigona lapicida appears to have been a temporary Victorian introduction at Hawick in the Borders (Kerney, 1999). On the other hand, while there are no modern records for the shelled slugs Testacella haliotidea and T. scutulum in Scotland, these species are probably seriously underrecorded (Kerney, 1999), and should, perhaps, have been put in the “data deficient” category.

The Scottish Biodiversity List can be studied in full at www.biodiversity.scotland.gov.uk. It is intended to review it every five years. Meanwhile, it is regarded as “a tool for public bodies and others doing their Biodiversity Duty, and is an important source of information and guidance for all”. It will be used to develop priorities for species conservation, as well as developing Land Management Contracts. On the other hand, it is not intended to develop action plans for all the species and habitats on the List. Essentially the Scottish Biodiversity List is an attempt to define what species (and habitats) are rare and/or important in a Scottish context, and thus point out that these need special consideration.

References

Anderson, R. (2005) An annotated list of the non-marine mollusca of Britain and Ireland. Journal of Conchology 38, 607–637.

Kerney, M. (1999) Atlas of the Land and Freshwater Molluscs of Britain and Ireland

Kerney, M.P. (2001) Recorder’s report: non-marine Mollusca. Journal of Conchology 37, 239–240.

Kerney, M.P. (2002) Recorder’s report: non-marine Mollusca. Journal of Conchology 37, 417–420.

Macadam, C. (2005) Mad about mud snails. BRISC Recorder News No. 59, pp 2–3. (Obtainable at www.brisc.org.uk)

Sumner, A. T. (2006) Distribution of certain molluscs in the lowland canals of Scotland. Journal of Conchology, in press

Table 1. Non-marine molluscs on the Scottish Biodiversity List