bog and wet heath. The bogs in the park mostly have a characteristic flora that includes heather (Calluna vulgaris), bell heather (Erica cinerea) and western gorse (Ulex gallii), with occasional bilberry (Vaccinium myrtillus). Large-flowered butterwort (Pinguicula grandiflora) is common. The bogs also support a number of notable species, including mosses (Sphagnum pulchrum, S. fuscum, S. platyphyllum, S. strictum, S. contortum and Calliergon stramineum), liverworts (Cladopodiella francisci and Calypogeia azurea) and lichens (Cladonia mediterranea, C. macilenta, C. rangiferina, C. arbuscula and Cetraria islandica). The remoteness of some of the upland areas aids the survival of Ireland's only remaining wild herd of native red deer. The bogs are threatened by grazing, turbary, burning and afforestation. Flora A large number of plant and animal species of interest occur within the site, including most of the native Irish mammal species, several important fish species including Arctic char, and a range of rare or scarce plant species. Several of the animal and plant species in the park have a hiberno-lusitanean distribution, meaning that they only occur in southwest Ireland, northern Spain, and Portugal. The main reason for this is the effect of the Gulf Stream on southwest Ireland's climate. The park has been designated a biosphere reserve because of the presence of such rare species. Significant amounts of plant species found in the park have unusual geographic distributions and are of localised occurrence within Ireland. These plant species are grouped within four main categories: arctic-alpine plants, Atlantic species, North American species and very rare species. Atlantic species are species which are otherwise found mostly in southern and south-western Europe, for example arbutus, St Patrick's cabbage and greater butterwort. North American species include blue-eyed grass and pipewort. Bryophytes Bryophytes (mosses and liverworts) flourish in the park, due partly to the area's mild oceanic climate. The park is internationally significant for bryophytes. Many of the bryophytes found in the park are not found anywhere else in Ireland. Mosses, ferns such as filmy ferns, and liverworts grow luxuriantly. Many of them live as epiphytes, growing on the branches and trunks of trees. Other plant species The Killarney fern (Trichomanes speciosum) is probably the most rare plant species in the park. It is a filmy fern that grows in the splash zone of waterfalls and other damp places. Although it was once quite common, it was picked almost to extinction when pickers collected it to be sold to tourists.