Of some key species of land and freshwater mollusca in the Republic of Ireland.

Ireland has an impoverished molluscan fauna compared to Britain, with approximately 75% of British species of land and freshwater snails. While island biogeography dictates that Britain must enjoy a lower range of species than mainland Europe, Ireland is even more isolated, and has less habitat diversity compared to Britain. Most noticeably missing are those species of the south-east of England which enjoy the drier, warmer climate (e.g. Helicodonta obvoluta, Monacha cartusiana), species of dry calcareous grassland (e.g. Truncatellina spp.) and those of native woodland (e.g. Ena montana, Limax tenellus). The geological "soup-bowl" shape of Ireland (the low-lying calcareous midlands are surrounded by acidic mountain ranges) has acted as an extra barrier to species spread. However, the building of the Royal and Grand Canals from the mid-eighteenth century onwards aided species to spread throughout the wet, calcareous centre of Ireland. One of the manifestations of the profusion of wetland habitats found in Ireland compared with its virtual absence of old calcareous woodland and grassland habitats is that the characteristic habitats of some mollusc species in Ireland are different to those in Great Britain. A good example is Leiostyla anglica, a common wetland snail in Ireland, which is a declining species in Britain and an indicator of ancient woodland there (Kerney, 1999).

Ireland has five species that are protected under the European Union Habitats and Species Directive, three Vertigo species V. geyeri, V. moulinsiana and V. angustior, the freshwater pearl mussel Margaritifera margaritifera, and the Kerry slug Geomalacus maculosus.

Recent surveys (1995-1998) carried out by Duchas, the Heritage Service (Ireland's conservation authority) have shown Vertigo geyeri to be more widespread than previously thought, with 8 populations being recorded in 6 different counties. Vertigo moulinsiana was found to have good populations in a number of key sites within short distances of the canals and navigation systems connected to them. A number of new sites for Vertigo angustior have been found in recent surveys (1995-1999) of westerly dune systems, suggesting it is the most common of the protected vertiginids in Ireland. By comparison, these surveys have underlined the rarity of other Vertigo species in the country, namely V. lilljeborgi and V. pusilla.

A total of 149 rivers were surveyed for pearl mussels (1991-1995). Living mussels were found in 26 of these, in 50 out of 526 sites sampled. Young mussels (less than 5 years old) were only found in 8 of these sites.

Evelyn A. Moorkens

evel...@eircom.net

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