Images of British Lichens
Hypotrachyna afrorevoluta (Krog & Swinscow) Krog & Swinscow
(= Parmelia afrorevoluta Krog & Swinscow)
Thallus foliose, light grey, lobes smooth and often slightly lustrous above, to matt with surface very minutely rugulose, edges turned down and tinged tan-brown, soredia initially pustulate, marginal and laminal, with rather coarse, grey-green to dark grey soredia (green when wet), undersurface black, brown at margins, rhizines unbranched or some bifurcate, occasionally projecting horizontally as cilia from lobe margins; apothecia rare. Widespread and evidently frequent but under-recorded, on trunks and main branches of deciduous trees; only recently distinguished from H. revoluta.
Refs: Nordic Lichen Flora (2011) 4: 62, 157 (photo, printed too dark); Smith et al. (2009), 441 (briefly, under H. revoluta); Purvis et al. (1992), 430 (as Parmelia, briefly, under P. revoluta); Dobson (2011), 198 (photo); van Haluwyn et al. (2009), 96-7 (photo); Wirth, Hauck & Schulz (2013), 1: 536 (photo), 2: 808; Frahm et al. (2010), 110-11 (photo); Hinds & Valcárcel et al. (2003), 276-7 (photo, as Parmelia revoluta); Hinds (2007), 277.
H. revoluta differs in its green soralia on the tips of terminal lobes, with finer soredia, and pale to darkish brown undersurface. Hinds & Hinds (2007) and Elix & Thell in Nordic Lichen Flora (2011) give useful descriptions of both species, and van Haluwyn et al. (2009) provide a valuable photographic comparison. Correct placement of some specimens is difficult, but they seem distinct when growing in proximity, H. afrorevoluta on trunks and main branches, H. revoluta favouring smaller branches.
I first encountered this species in 2009 (photographs below), at a time when the BLS website considered British records to be erroneous, but it was immediately apparent that this was not H. revoluta as I knew it. Instead it matched continental internet pictures of H. afrorevoluta. The species is now generally accepted. Elix & Thell consider it more coastal than H. revoluta in Scandinavia.
|On trunk of hybrid Sallow (Salix x multinervis), Gleniffer Braes, Renfrewshire, April 2011 |
|On trunk of Crack Willow (Salix fragilis) in damp woodland, Shewalton Sand Pits, Ayrshire, May 2009 (with the orange alga, Trentepohlia)|
|On trunk of Norway Maple (Acer plananoides) in town centre, Paisley, Renfrewshire, November 2011|
|On trunk of Oak (Quercus robur), lobes and soredia green, as wet from melted snow, Wicken Fen, Cambridgeshire, February 2010|
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© A.J. Silverside
Uploaded December 2011, updated January 2016