Heterodermia leucomela is a rather inconspicuous fruticose lichen which forms loose tufts up to 10cm across. The grey-white thallus is highly dichotomously branched, the branches being between 3-5mm in width. The margins of the branches are lined with many black cilia or "whiskers" up to 5mm long. The lower surface ihas a broad, white, slightly sunken channel along the centre, which appears slightly rough under a lens due to the lack of a cortex here. This is in contrast to the smooth raised margins on each side. Apothecia have not been observed in British material.
Photo: Alan Hale
H. leucomela can superficially appear similar to several of the shrubby Cladonia species, and to some species of Physcia that are similar in colour and have dark cilia. However, on closer inspection these are all quite distinct. It is hard to confuse this species with any other British taxon.
Amost exclusively found on exposed coastal cliffs in short turf on thin soil, or more rarely on low rock outcrops. It is usually associated with other lichens, and bryophytes, which it often uses to attach itself to. It has rarely in the past been found on trees (the Flora says wayside trees, Bryan Edwards says "trees in ancient woodland or parkland").
Heterodermia leucomela is widespread in tropics and sub-tropics, reaching it's northern limit in Britain. It has a southern-oceanic distribution in Britain and Ireland, being restricted to south-west England, West Wales and south-west Ireland.
H. leucomela is currently known from 5 sites in Wales, in 5 different hectads. Historically it was first recorded in Wales in 1895 by J.E. Griffiths who found it near Rhoscolyn on the west coast of Anglesey. In more recent times there are records from Bardsey and near Aberdaron on the Lleyn Peninsula. A survey in 2001 rediscovered the species on Anglesey and found healthy populations on the tip of the Lleyn Peninsula (Edwards, 2002). The Bardsey populations are part of a long term monitoring project. In 2004 the species was recorded for the first time in Pembrokeshire at St David’s Head, and in 2005 it was found in some quantity further south at Stackpole Head. It's Anglesey sites are the northenmost in Europe.
|Location||Grid Reference||Year Last Rec||Recorder||SSSI|
|Anglesey: Rhoscolyn Head||SH 2574 7552||2002||B. Edwards||Yes|
|Anglesey: Penrhosfeilw Common, Penrhyn Mawr||SH 2118 7959||2002||B. Edwards||Yes|
|Caernarfon: St Mary's Well, Lleyn||SH 1387 2521||2003||A.D. Hale & T. Dines||Yes|
|Caernarfon: Trwyn y Gwyddel||SH 1399 2506||2003||A.D. Hale & T. Dines||Yes|
|Caernarfon: Slopes of Mynydd y Gwyddel||SH 1413 2490||2003||A.D. Hale & T. Dines||Yes|
|Caernarfon: Ynys Enlli, above Pen Cristin||SH 1218 2122||1992||A. Fletcher||Yes|
|Caernarfon: Ynys Enlli, southern tip, western side||SH 110 204||2001||A. Fletcher||Yes|
|Caernarfon: Ynys Enlli, southern tip, eastern side||SH 114 207||2001||A. Fletcher||Yes|
|Caernarfon: Ynys Enlli, southern tip, western side||SH 12 21||2001||A. Fletcher||Yes|
|Pembroke: St. David's Head||SM 724 280||2005||A.D. Hale & R.G. Woods||Yes|
|Pembroke: Saddle Point, Broadhaven||SR 981 940||2005||R.G. Woods||
H. leucomela has always been a rare species in Britain. Numbers of populations in Wales have actually increase in recent years, probably due to increased awareness of the species and effort focused on looking for populations. It is listed on Scheduel 8 of the Wildlife and Countryside Act 1981 as being in need of special protection, and is on both the UKBap and Wales Section 42 lists.
|UKBAP Signposting Actions:|
|Monitor the habitat and species (along with Pseudocyphellaria aurata with which it grows*), at a sub-set of extant sites, at least every 6 years, to ensure that grazing and shrub control management maintains open nature of maritime heathland and grassland and modify accordingly.|
|2.||Encourage survey for this species and incorporate new sites into the monitoring and management framework.|
* Not in Wales.