ASCOMYCOTA | LECANOROMYCETES > LECANORALES > Parmeliaceae

Genus Punctelia, meaning 'dotted' from the shape and positioning of the pseudocyphellae

Common name:            Borrerianj (Speckled shield) Lichen

Synonym:                    Parmelia borreri

Habitat:                          Wayside trees

Substrata:                     Bark, moss-covered rocks

Growth forms:              Corticolous, muscicolous

Thallus:                   Foliose

Apothecia:                    Lecanorine, absent or rare

BLS identity rating:        Graded 2/5 (visual identification possible, although TLC recommended)

Foliose thallus usually rosette-forming, growing to around 5-8cm dia., occasionally a fair bit larger; closely adpressed to the substratum, although the outer lobes more loosely at the tips where they're usually slightly raised and wavy, 5-10mm broad, often uneven and pitted, with rounded margins and small indentations, contiguous or overlapping.

Upper surface varies from pale grey to blue grey when dry, turning grey-green to greenish when wet, sometimes brownish at the apices; the underside of the marginal lobes can vary from pale to dark brown but, importantly, the whole of the thallus becomes darker towards the centre with the specimen having to be peeled off the substrate to confirm; rhizines dense, simple or clumped, but not extending to the lobe margins; when young, whitish, irregular-shaped and variably sized, punctiform pseudocyphellae is scattered across the top of the lobes, usually developing into rounded, dot-like soralia; coarse soredia present in the central area of the thallus only, occasionally becoming blackened or semi-corticate.

Apothecia rare but, when present, very shortly stalked, discs to 6mm dia., and red-brown in colour.

Punctelia borreri is primarily a localised southern species, occurring on well-lit nutrient-rich bark of broadleaved trees in relatively open sunny locations; usually on the south side often mixed in with mosses; also, but far less frequently, found on moss-covered rocks or rocks in coastal regions.

It is very similar in appearance to Punctelia subrudecta except for its mainly black (away from the lobe margins) underside, coupled with less numerous and less rounded pseudocyphellae, coarser soredia and, if spot-tested, a C+ pinkish rather than carmine-red reaction. Also note that the lobes do not have the brownish or dark coloured edges found in either Punctelia jeckeri or Punctelia subrudecta.

The first couple of photos featured below were looked at by an experienced lichenologist who was quite sure they were Punctelia borreri despite being a little damp and, therefore, greener than they would be if dry; the large rounded lobes, covered with a mix of both large and small pseudocyphellae, together with the tiny pseudocyphellae near the lobe tips, were the key features. The two examples growing amongst mosses were checked in situ; spot-tested C+ pale pinkish-red, and a lobe removed to check the underside, which was black towards the centre grading to pale brown around the margins.