Absence of geomalacus maculosus (Kerry slug) from parts of western Ireland suggests human mediated transport of species to its most northerly location

The Kerry Slug, Geomalacus maculosus (Arionidae), which is restricted globally to Ireland and the northern Iberian Peninsula, is protected under European law. The distribution of G. maculosus in Ireland was believed to be confined to the south-west of the country until 2010, when it was discovered in a conifer plantation nearly 200km north of its previously known distribution. A survey (using hand searching and live trapping) at 42 sites (forests and associated habitats) lying between the newly discovered population to the north and existing populations in the south-west of Ireland was undertaken during October and November 2011. While other slug species were found at the surveyed sites, G. maculosus was not discovered, suggesting that it is highly unlikely that this species arrived at its most northerly location without human intervention. This paper investigates possible routes of introduction for the species and implications of its discovery in commercial conifer plantations.