Kerry Slug
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| Geomalacus maculosus Allman, 1843 |
The Kerry Slug (Geomalacus maculosus) is a species of slug in the Arionidae family.
It is listed as an Annex II and Annex IV species of the European Habitats Directive.
The Kerry slug was originally described from specimens collected in Ireland. William Andrews sent material he had found at Caragh Lake, Co Kerry to Allman in 1842. Allman (1843) then introduced it to science as a new species.
[edit] Distribution
Despite its "discovery" at Caragh Lake, Ireland is not at the centre of the slug’s distribution. This is centred upon continental Iberia, where it ranges over a large contiguous area in north-west Spain (Galicia) and northern Portugal [1]. Its occurrence in southwest Ireland is atypical and something of a mystery because of its apparent absence from any intermediate localities. The Kerry slug, along with a range of other fauna and flora, including several heather species, the strawberry tree and at least one other mollusc the Pyrenean glass snail Semilimax pyrenaicus, constitute a distinct faunal and floral element in Ireland, usually called ‘Lusitanian’ (for the supposed land are off south-west Ireland present during the last glaciation, but now under the sea). The reference to Lusitania denotes an early theory that there was an ice-free refugium to the south-west of Ireland during the Quaternary (last) glaciation. In this, supposedly, relic fauna and flora from a previous ice-free period survived until the present warmer interstadial period. This theory is not now accepted but the term Lusitanian is still used for fauna such as the Kerry slug.
A better explanation of the occurrence of the slug in south-west Ireland has been developed recently. This is exemplified by two recent discoveries: the genetic similarity of much of Ireland’s fauna to that of northern Spain; the genetic similarity of much of Ireland’s human population to that of northern Spain. Mascheretti et al. (2003)[2] examined the genotypes of Eurasian Pygmy Shrew, a small mammal, across its range in Europe. The Irish population showed close genetic affinity to a population from Andorra but not to that of Britain or other places in Europe. The genetic structure of the population further showed that the entire Irish population had originated from a single founder event. The authors concluded that it had been introduced in the early (Palaeolithic) or middle (Mesolithic) Stone Age, by boat, probably from south-west Europe. This coincides with work on human populations which found[3][4] a strong similarity in make-up between populations in western Ireland and in northern Spain. This is explained by the migration of peoples from Spain to Ireland in the late Paleolithic or early Mesolithic. It seems increasingly likely that much of Ireland’s Lusitanian fauna is an artefact of this era of human expansion in the early part of the Postglacial era i.e. introduced accidentally with trade items or goods brought by boat from Iberia.
[edit] European Protection
Because of its perceived rarity and restricted distribution, Geomalacus maculosus was protected under the Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention), EIS Bern Invertebrates Project. This was backed by studies of its distribution and ecology in Ireland[5] which concluded that evidence of a decline in Iberia plus uncertainty over its status in Ireland supported its inclusion in the Convention. Platts & Speight (1988) noted that it occurs in only three protected sites in Ireland: Glengariff Forest, West Cork; Uragh Wood Nature Reserve, South Kerry; and Killarney National Park, North Kerry. They concluded that it could not be adequately safeguarded with only three sites and supported inclusion in the Bern list to which the Irish government is a signatory.
[edit] Reference
- Mollusc Specialist Group 1996. Geomalacus maculosus. 2006 IUCN Red List of Threatened Species. Downloaded on 18 July 2007.
- ^ Castillejo, J. (1998) Guia de las babosas Ibericas. Real Academia de Ciencias, Santiago de Compostela. 154 pp.
- ^ Masheretti, S., Rogatcheva, M. B., Gündüz, I., Fredga, K. & searle, J. B. (2003) [How did pygmy shrews colonize Ireland? Clues from a phylogenetic analysis of mitochondrial cytochrome b sequences] [1] Proc. Roy. Soc. B 270: 1593-1599.
- ^ Hill, E. W., Jobling, M. A. & Bradley, D. G. (2000) Y chromosome variation and Irish origins. Nature 404: 351.
- ^ McEvoy, B., Richards, M., Forster, P. & Bradley, D. G. (2004) The longue durée of genetic ancestry: multiple genetic marker systems and Celtic origins on the Atlantic facade of Europe. Am. J. Hum. Genet. 75: 693-702.
- ^ Platts, E. A. & Speight, M. C. D. (1988) The taxonomy and distribution of the Kerry slug Geomalacus maculosus Allman, 1843 (Mollusca: Arionidae) with a discussion of its status as a threatened species. Ir. Nat. J. 22: 417-460.
