The mite (Arachnida: Acari) fauna inhabiting Irish machair: a European Union priority coastal habitat Julio Arroyo & Thomas Bolger Received: 21 August 2010 / Revised: 24 September 2010 / Accepted: 28 September 2010 / Published online: 15 October 2010 # Springer Science+Business Media B.V. 2010 Abstract Machair is a highly specialised and complex sand dune habitat confined globally to the west coasts of Ireland and Scotland. Irish machair is designated as a priority habitat under the EU Habitats Directive, with the habitat coverage restricted to the machair grassland. The main goals of the study were to describe the Acari fauna inhabiting the Irish machair and to determine the unique- ness of its mite communities in the context of habitat protection. Ten Irish machair sites were selected and samples were taken from the machair grassland and from two types of dunes within the wider machair system: shifting dunes (foredunes) occurring at the beach and stable (fixed) dunes located in the transition zone to the inland grassland flat areas. One hundred and eleven mite taxa were recovered. The most widespread was Scutovertex cf arenocolus Pfingstl et al. 2009, a halophilous species that has been found in the epilittoral zone of Baltic and European Atlantic coasts. The genus Autogneta Hull 1916 (Oribatida: Oppiidae) and the oribatid species Hermaniella granulata (Nicolet 1855) were recorded for the first time for Ireland. Peloptulus cf gibbus Mihelčič 1957, may also be a new record. Multivariate analysis showed that community composition varied between the areas sampled in the machair systems and that in the machair grassland, an Annex I priority habitat in Ireland, was especially different from both dune types sampled. The assemblages also varied significantly between the different sites sampled in the study. Keywords Coastal dunes . Machair . Priority habitats . Mites . Invertebrates . Ireland Introduction The invertebrate fauna of some habitat types in Ireland are still poorly known. In this project we studied the Acari communities inhabiting machair, an important habitat present in the west coast of Ireland. Machair is a highly specialised and complex sand dune habitat confined globally to the west coasts of Ireland and Scotland. It is designated as a priority habitat type for Ireland under the EU Habitats Directive. The identification of particularly vulnerable species, such as habitat special- ists, will offer scientific data to strengthen the case for preservation of these threatened ecosystems. The term Machair is an old Gaelic word for areas of level, stable, dune grassland over calcareous soils. It derived from the Gaelic mach, meaning ‘plain’ and has been used widely in place-names in both Ireland and Scotland, even in parts of both countries that have never supported machair habitat, e.g. Machair Aonghuis, the Angus Plain (E Scotland) (Angus 2004). In Ireland, machair vegetation is confined to the Aran Islands, and along the west coast from Co. Galway to Malin Head, Co. Donegal (Bassett and Curtis 1985; Ryle et al. 2007). The true machair grassland represents an area where wind erosion has eroded the original dune system down to a level just above the water table and where the wet consistency of the sand prevents further erosion. Typically the grassland plain of the machair lies behind a dune ridge J. Arroyo (*) : T. Bolger School of Biology and Environmental Science, Science West, University College Dublin, Belfield, Dublin 4, Ireland e-mail: juahcuatro@gmail.com T. Bolger e-mail: tom.bolger@ucd.ie J Coast Conserv (2011) 15:181–194 DOI 10.1007/s11852-010-0132-1