Distribution and habitat

Killarney fern is a Macaronesian-European endemic, although similar sub-fossil plants have been found in the Caucasus. Most frequent in the Azores, relatively common in the mountains of Madeira and very locally surviving in the laurel forests of the Canaries, the sporophyte is known to occur as far north as Scotland. It is found in continental Europe at scattered localities along the western seaboard:

  • from the hills just inland from Gibraltar
  • near Sintra and Oporto in Portugal
  • more frequently in north-western Spain, along the foothills of the Pyrenees into France
  • in Brittany
  • at scattered locations in Ireland

Its past abundance in the Killarney region in south-west Ireland account for its common name. Away from Europe's west coasts it was discovered in the Alpi Apuane in northern Italy for the first time in 1977.

It was first found, near Bingley in Yorkshire by Dr. Richard Richardson in 1724. His specimens still survive in several British herbaria, including here at the Museum, although changes to the habitat, to provide a source of drinking water to the growing town around 1785 led to the apparent loss of the plant. However, unbeknownst to the Victorian fern gatherers it still survived but only as the small felty gametophyte.

The finding of the gametophyte near Bingley and elsewhere in the British Isles in 1989 rapidly led to its discovery in the Northern Vosges and later the Massif central in France, the Suisse Luxembourgeoise in Luxembourg, where now over 100 sites are known, various sites in Germany, the neighbouring Czech Republic and most recently (2004) at its most eastward point, in Poland. Small sporophytes have been seen to be produced in some German sites.

In the British Isles the sporophyte is now known from at least 22 separate localities, in some of which are many small and perhaps recently formed plants, whereas others support single patches which have been known for nearly 150 years. The gametophyte in contrast is known from over 120 hectads (10km squares), with the potential for many more to be discovered.

Habitat

The habitat of the Killarney fern is both easy and at the same time rather difficult to characterise. 

The sporophyte requires 

  • a fairly constant and very high humidity
  • shelter from extremes of cold 
  • can withstand deep shade 

thus is found in very different looking range of habitats and landscapes but often within very precise and limited microsites which at the very local scale are essentially environmentally similar. 

Ratcliffe et al., (1993) reported it to occur in four main floristic groups based on these varied habitats.

In the British Isles it occurs on rocks, spreading sometimes into the terrestrial environment. In the southern parts of its range it may occur as a liane (climber) becoming epiphytic on tree trunks.

The fern is only found on fairly acidic rocks, although sometimes where influenced by base rich seepages from adjacent calcareous strata. 

The gametophyte is found on a range of rock types but avoids limestones. The rough porous sandstones of the millstone grit series and the Old-red sandstones are particularly suited to supporting extensive growths. Suitable faulting provides the necessary crevices and caverns within which stable sheltered environments can occur.

The species altitudinal range is from sea-level to over 1200m in the Azores; within the British Isles it is essentially lowland but occurs up to c. 520m in North Wales.

Glossary

Epiphytes 

plants which grow above the ground surface, using other plants or objects for support.

Liane

is any of various long-woody vines that are rooted in the soil at ground level and use trees, as well as other means of vertical support, to climb up to the canopy in order to get access to well-lit areas of the forest.