Observation 202443: Physcia phaea (Tuck.) J.W. Thomson

Proposed Names

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Recognized by sight
Used references: ID confirmed by Jim Bennett

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Sounds like a printer calibration issue
By: Jason Hollinger (jason)
2015-04-08 20:15:40 CDT (-0400)

I’d stick with old-fashioned rulers from the hardware store!

Sure, I’ll take on Mr. Moberg, but later,
By: Andrew Khitsun (Andrew)
2015-04-08 19:36:47 CDT (-0400)

first, I have to settle with ruler-makers: couple printable rulers I found online came out smaller than two different plastic ones I have at home. Meaning, their units are smaller than the units on plastic rulers. I can’t figure out what’s going on.

Don’t shoot the mesenger!
By: Jason Hollinger (jason)
2015-04-08 19:15:16 CDT (-0400)

I’ve always wondered how one decides what the average thallus size is, because unlike people, they don’t just stop growing(!) I think the only thing I can take from those sizes, side-by-side, is that “growing in the same conditions on the same substrate, P. phaea will tend to be smaller”. But feel free to register a complaint with… R. Moberg — he’s the one responsible for the Physcia treatment in the Sonoran Flora! :)

By: Andrew Khitsun (Andrew)
2015-04-08 18:56:54 CDT (-0400)

I have a strong issue with sizes as stated in Sonoran Flora: did they confuse centimeters and inches? Never mind three or five centimeters. The critters here are 7-8 cm, and they are small ones compared with others I posted before (and the ones I didn’t too). I’d say 7-10 cm is the most common size of these circles in most places where they are thriving. I promise to prove this by carrying a ruler next time (just found one good ruler to use).

More notes
By: Jason Hollinger (jason)
2015-04-08 11:20:40 CDT (-0400)

Bruce McCune differs in opinion about lobe size (from Macrolichens of the Pacific Northwest):

Physcia aipolia Physcia phaea
lobes < 1(2)mm mostly about 2mm

Otherwise he suggests no way to distinguish saxicolous specimens… which could well mean that he was equally unaware that P. aipolia commonly grows on rock! :)

Looking more deeply into the crenulate young apothecia mentioned under P. phaea in the Sonoran Flora: All my photos of P. aipolia (all from bark), show distinctly smooth rims even on budding apothecia. Yet, your photos here show strongly crenulate apothecia toward the center. However Bruce Ryan (in his unpublished keys) claims that P. aipolia, too, “often becomes crenulate”. Perhaps there’s a difference in young apothecia only? P. phaea becomes crenulate earlier?

Bruce Ryan has an interesting note, comparing the two:

“[P. phaea is] sometimes difficult to distinguish from P. aipolia (spores averaging longer in that species, but overlapping), but that species is almost always corticolous.”

Looks like he came to the same conclusion we just did about spore size being the only real distinction.

Hard to find comparisons of the two
By: Jason Hollinger (jason)
2015-04-08 11:05:20 CDT (-0400)

This is taken from comparing full descriptions in the Sonoran Flora:

Physcia aipolia Physcia phaea
thallus to 5cm to 3cm
lobes to 2mm to 1.5mm (usually 1mm)
flat to convex flat to slightly convex at tips
surface whitish gray to dark gray gray to dark gray
usually distinctly maculate usually strongly maculate
smooth? ±rugose
sometimes weakly pruinose epruinose
apothecia to 2mm to 1.5mm (usually less)
often white pruinose sometimes white pruinose
margin always smooth? crenulate when young
spores physcia to pachysporaria physcia-type
(19)21-25(28)x9-11(13)µm (15)16.5-20(21.5)x(6.5)7-9.5(11)µm

It looks (to me) like the only “sure-fire” discriminant is spore size. :( P. phaea is otherwise somewhat smaller, darker and more rugose, that’s it!

By: Andrew Khitsun (Andrew)
2015-04-08 00:51:11 CDT (-0400)

Since Esslinger “invaded” our town last year and ruled that everything with pruina is Physcia aipolia, my world has been upended :-( These would normally be called P.phaea if not for pruina. Please help me find my way back to sanity.

Created: 2015-04-08 00:39:30 CDT (-0400)
Last modified: 2016-01-20 22:06:14 CST (-0500)
Viewed: 88 times, last viewed: 2017-10-24 01:16:20 CDT (-0400)
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