Arthonia atlantica

Description

Thallus effuse (spread out and flattened) or forming mosaics with other lichens. White to pale grey, matt, cracked-areolate (crazy-paving like). Apothecia more or less immersed in the thallus, irregulalry rounded (to 0.2mm dia) though more usually elongate or stellate, often joining to form an irregular reticulum (network).

Habitats

Hard acid rocks in dry underhangs and sheltered sides of old walls, usually near the coast.

Distribution

SW England, W Scotland, W Ireland and W Wales. Outside the British Isles known only from Brittany.

Records from Wales

Location	Grid Reference	Last Rec'd	Recorder	SSSI
Cardigan: Coedmor NNR	SN14, SN24	1996	A. Orange & P. Wolseley	Yes
Caernarfon: Nantgwynant	SH65	1973	A. Pentecost	Yes
Meirionydd: Porthmadog	SH58274107	2002	A. Orange
Pembroke: Skomer Island - North Castle	SM7305	1750-1996	Unknown	Yes
Radnor: Coed Aberedw	SO0747	1960	Unknown	Yes

Notes on Individual Locations in Wales

Skomer Island - surveyed by Natural History Museum lichenologists in the mid-1990s, but this species not recorded.

Coed Aberedw - the record in the Welsh Threatened Lichen database puts this site in Ceredigion. But there is no site of this name in this vc and the grid-ref places the record in the Radnor site. This inland site is anomalous however.

Coedmor - occasional on rock outcrops in NNR compartments 2,6,9,10 and 11.

Porthmadog - Pen y Garn, Prenteg. On rocks below overhang in Quercus petraea woodland.

Hectad Distribution in Wales/NBN Gateway Map

(Be aware that the data on the Gateway may be incomplete and the maps should not therefore be relied upon as a full representation of the distribution of this species. Note that the maps coverage includes some parts of England. Also, without a registered account on the Gateway your access to datasets may be limited)

Proposed Actions

	UKBAP Signposting Actions:
1.	Monitor the habitat and species at two extant sites, at least every 6 years, to ensure that management maintains or expands woodland continuity and modify accordingly. Pay special attention to threats from excessive shade cast by climbers, and evergreen trees and shrubs, particularly invasive non-native species, and inappropriate grazing levels and forestry operations.
2.	Promote agri-environment schemes capable of delivering appropriate site management.