Caloplaca herbidella
Distinguished by abundant white-grey isidia which cover and obscure much of the thin, similarly-coloured thallus. Apothecia are often not present, but when they are they can be abundant or otherwise occasional and scattered. 1-3 mm diam., rounded to flexuose, with a rust-red disc and the margin a similar colour to the thallus. Chemical tests: Thallus and isidia K- (isidia tips sometimes K+ faint purple); apothecia K+ purple.
Thallus with isidia but no apothecia. (Photo: K. van Herk)
Thallus with abundant apothecia. (Photo: Ray Woods)
The apothecia resemble those of Caloplaca ferruginea but are usually intermittent and short-lived. Thalli without apothecia can resemble forms of some Porina species. Caloplaca chlorina has a darker grey thallus with a blue tinge, and occurs on rock rather than trees. Pertusaria coronata is K+ yellow, Pd+ orange.
On old trees in wood pasture, especially well-lit Quercus trunks; rarely Castanea. In
Europe, Macronesia, Asia, Africa. S.&S.E. England, mid Wales. (Note the "Flora" mentions a Westmoreland UK population but this has since been re-determined as C. furfuracea - see Arup & Akelius, op cit.).
Records from Wales:
| Location | Grid Reference | Recorder | Year Last Rec | SSSI |
| Brecknock: S. of Comin-Coch | SN990541 | R.G. Woods | 1997 | No |
| Brecknock: Garth House | SN941499 | R.G. Woods | 1997 | No |
| Brecknock: Llanwrthwl - Field near Caegarw. | SN978624 | R.G. Woods | 2009 | No |
| Brecknock: Llanwrthwl - near Crynfryn | SN978626 | R.G. Woods | 2009 | No |
| Carmarthen: Glan Bran Deer Park | SN799378 | R.G. Woods | 1995 | No |
| Montgomery: Gregynog Great Wood | SO079976 | R.G. Woods | 1990 | Yes |
| Radnor: Stanage Park | SO3371 | Welsh Lichen Group | 2007 | No |
|
Radnor: nr. Newbridge-on-Wye |
SO020559 |
S.P.Chambers |
2009 |
No |
|
Radnor, Tyn Coed, Disserth |
SO02895541 |
RG Woods |
2010 | No |
Elsewhere in Britain this species is exceedingly scarce. Only in the New Forest does there appear to be a population approaching that of mid-Wales. Savernake once supported a number of trees with it on but no material has been seen recently and this site is now probably too densely wooded.
Notes by RGW South of Comin Coch - this population occurs on an ancient trackside oak. It has never been found fertile and by 2009 it was in decline.
Garth House - originally found in 1983.
Nr. Newbridge-on-Wye - Steve Chambers recorded a probable colony on oak beside the access track to the BSW sawmill near Newbridge on Wye, This has been wiped out by a Welsh Assembly Government road improvement scheme. A small colony was found low down on the SW side of a field boundary ancient oak near Tyn Coed, Disserth. It was not fertile.
Gregynog Great Wood - the population here occurred on an ancient ash tree at the western extremity of the Great Wood. When first discovered in c.1976 it was fertile. However, over subsequent years it soon ceased to be fertile and the thallus also began to retreat. By 2005 it could no longer be found on this tree. The Lobaria pulmonaria with which it was associated had also declined in lobe size and extent. There had been no obvious local land use changes.
At Stanage and Garth House the species was found on sycamore; at Glan Rhos, Pencaerhelm, Glan Bran, near Newbridge on Wye and Llanwrthwl, on oak.
Elsewhere in Britain this species is exceedingly scarce. Only in the New Forest does there appear to be a population approaching that of mid Wales though even here it has never been recorded from more than a handful of trees (Neil Sanderson pers comm.). Savernake once supported a number of trees with it on but no material has been seen recently and this site is now probably too densely wooded (Neil Sanderson pers comm.). Neil has also failed to relocate it at Hurstbourne Park in N. Hants. A recent taxonomic study (Arup,U. & Akelius, E. (2009) in the Lichenologist, 41 pgs 465-480) has shown that some European records of C. herbidella refer to a newly described species, C. coralliza. Most British collections appear to belong to C. herbidella in the strict sense, although a collection from Levens Park in Cumbria has been identified as C. coralliza.The latter species is rarely fertile and can have a very distinctive orange thallus covered in richly branched orange isidia. It does however occur as a grey form and could be mistaked then for C. herbidella. The thallus of C. coralliza is more densely covered in branched isidia. This crust of isidia frequently cracks into seperate islands or areoles. In C. hebidella such dense turves of isidia are rare and never crack. A critical re-appraisal of British herbarium material is required. Direct threats come from the loss of the host tree, shading by the growth of adjacent vegetation and ivy and gross eutrophication particularly by the injudicious spreading of farmyard manure and slurry that can coat trees. There are some site where its loss cannot be accounted for by any obvious change in adjacent land use.RGW
- Monitor the habitat and species at sites, at least every 6 years, to ensure that owners and occupiers continue to be aware of the presence of this lichen and of its requirements.
- Promote further survey of potentially suitable trees and bring any newly discovered populations into the monitoring/management programme.
- Promote sympathetic land management of areas adjacent to existing populations (particularly through targeted agri-environment schemes) and ensure that existing colonies are not threatened by the growth of overshading vegetation.Make use of any additional records to better refine our understanding of the management requirements of this species. If necessary through tree surgery seek to prolong the life of the host tree for as long as possible.
Arup, U. & Akelius, E. (2009). A taxonomic revision of Caloplaca herbidella and C. furfuracea. The Lichenologist 41(5): 465-480
Coppins, B.J & Fletcher,A. (2001). Caloplaca herbidella. Species account 260/2001 in the Caloplaca fascicle of the Lichen Atlas of the British Isles produced by the British Lichen Society, London