Observation 66578: Pertusaria lactea (L.) Arnold
When: 2011-04-25
Who: zaca
No herbarium specimen

Proposed Names

45% (2)
Recognized by sight
58% (1)
Eye3 Eyes3
Based on chemical features: See attached photos.

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Eye3 = Observer’s choice
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2015-04-04: Revisited.
By: zaca
2015-04-07 13:49:04 PDT (-0700)

Almost four years later this specimen seems unchanged, maybe a litle bit larger.

I’m also completely convinced
By: zaca
2011-05-02 13:24:16 PDT (-0700)

that Chris is right and thus that this beautiful specimen is a Pertusaria lactea. In addition to his comments and those by Jason, I reproduce here the point of the BGBM:Pertusaria key Europe & Mediterranean for this species:
“94a Thallus rimose-areolated, almost smooth, rather thick, at border radiate-rugulose, the areoles about 0.3-0.8 mm wide; lecanoric, variolaric acids; soralia rounded, coarse-grained; fertile warts usually with single, brownish disc, initially white-pruinose; ascospores 1/ascus, about 180-240 × 60-100 µm; on non-calcareous or weakly calcareous rock, scattered throughout Europe, locally frequent; syn.: Ochrolechia lactea (L.) Hafellner & Matzer - 1/2/4/5/Pertusaria lactea (L.) Arnold”.
A point that was strange to me is that, accordingly, this species can be fertile with brownish discs, although no apothecia are visible in the photographs presented by Stridvall and in those by Silverside it is hard to say if some of the dots can be apothecia. I looked again to my photographs and, yes, I found some brown discs, one of them larger than the others. I already uploaded a photograph where this disc is put in evidence and is position on thallus marked.
My acknowledgements to Chris and Jason, for their help in this identification.

I’m convinced… for whatever that’s worth!
By: Jason Hollinger (jason)
2011-05-01 22:08:14 PDT (-0700)

I’d say the photos make an entirely plausible match. Note the range of variation between Stridvall and Silverside — zaca’s falls someplace comfortably between, I’d say, with nicely separated discrete soralia (versus the clustered mess in Stridvall’s) but well-developed thallus (unlike the thin thing in Silverside’s).

Amazing how speciose this genus is in Europe. How, errr… “fortunate” you are. :)

(And yes, doing spot tests “correctly” on Pertusaria and Ochrolechia is a whole art in itself.)

By: Chris Parrish (kitparrish)
2011-05-01 17:42:07 PDT (-0700)

The keys for Pertusaria in two British lichen books, Smith et al. (2009) and Dobson (2005), lead pretty smoothly to Pertusaria lactea, assuming that we are dealing with a sorediate Pertusaria with white to pale gray or ivory thallus, growing on rock (no mention of old houses), with soralia white to pale cream and C+ red (Dobson, 2005, p.321). Dobson gives the chemistry as thallus: C+r, KC+r, UV+ faintly blue-white; soralia: C+ pink-red. The key in Smith makes it pretty clear that a specialist would test the thallus and soredia separately (now they tell us!). The spores are huge: 180-240µm x 60-100µm, 1 per ascus. There are photos available by the Strivall’s and by Alan Silverside … perhaps somewhat close, but not an exact match. But we should remember that some of these Pertusaria can be quite variable (especially on the walls of old houses?), there are already almost 40 species in this genus in Britain, and I don’t have a Portuguese book to work with. Nevertheless, that’s pretty nice!

Update – Chemical reactions.
By: zaca
2011-05-01 15:29:18 PDT (-0700)
Chris, is good to know
By: zaca
2011-05-01 02:16:38 PDT (-0700)

that you also considered Pertusaria sp.. At the end, looking for possible genera, that was also my guess and I have looked into the BGBM:Pertusaria key Europe & Mediterranean, but the possibilities that I found there are species for which I couldn’t find any other information in the web.
My specimen lives in the exterior wall of an abondoned and very deteriorate old house.

By: Chris Parrish (kitparrish)
2011-04-30 18:25:17 PDT (-0700)

curious borders to the soralia, as if there were somehow more structure involved, and for Pertusaria Smith et al. (2009, p.673) say “disk sometimes occluded with granular soredia and appearing soralia-like or pruinose,” so I looked at a number of Pertusaria photos, especially the quite variable Pertusaria albescens, but this observation seems to stand apart

Too bad
By: Jason Hollinger (jason)
2011-04-30 15:00:38 PDT (-0700)

Such a nice well-developed thallus and pretty little soralia. Probably immediately identifiable to some with experience. But impossible to key out without chemistry. Go figure.

Unfortunately not!
By: zaca
2011-04-30 14:40:43 PDT (-0700)
Very nice specimen!
By: Jason Hollinger (jason)
2011-04-30 13:48:35 PDT (-0700)

Did you do any spot tests on it?

Created: 2011-04-29 17:40:53 PDT (-0700)
Last modified: 2015-04-07 13:46:49 PDT (-0700)
Viewed: 153 times, last viewed: 2016-10-26 20:27:46 PDT (-0700)
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