Observation 66277: Porpidia crustulata (Ach.) Hertel & Knoph

When: 2011-04-25

Collection location: Westmoreland Co., Pennsylvania, USA [Click for map]

Who: Hamilton (ham)

No specimen available

On a rock. Sandstone I think, but maybe not.


Copyright © 2011 Hamilton

Proposed Names

31% (2)
Recognized by sight
64% (4)
Used references: Lichens of North America; CNALH locality records

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= Observer’s choice
= Current consensus


Add Comment
By: Erin Page Blanchard (CureCat)
2011-04-26 18:40:52 CDT (-0400)

I proposed the name Rhizocarpon concentricum so this observation will show up under either name just for ID reference.

By: Hamilton (ham)
2011-04-25 22:14:48 CDT (-0400)

Thanks a lot Chris.

locality records
By: Chris Parrish (kitparrish)
2011-04-25 21:27:36 CDT (-0400)

Here is a map from CNALH indicating the distribution of Porpidia crustulata in North America (385 records). There are a lot of records for Pennsylvania. And here is a list of specimen locality records known to CNALH for Rhizocarpon concentricum (19 records). Click on “Maps” and then “Google Maps” to see a map. Very few records … though there is one for Pennsylvania. That seems to indicate that your specimen is more likely to be Porpidia crustulata. In fact, the odds might be about 385 : 19, which is more than 20 : 1. That ought to be enough to file this photo with Porpidia crustulata!

By: Chris Parrish (kitparrish)
2011-04-25 21:04:15 CDT (-0400)

The Porpidia has one-celled spores, and the Rhizocarpon has muriform spores (looking like an oval piece of a brick wall), and as far as I know one would have to do the microscopy to be sure of an identification. Very happy to see the photo here on MO in any case!

By: Hamilton (ham)
2011-04-25 19:16:53 CDT (-0400)

Yeah I just thought they were pretty neat looking. I don’t know a darn thing about lichens but I figured I would post them here and see if the experts might know it. Guess these aren’t easy ones from what you’re telling me. Thanks for taking a look though.

concentric rings
By: Chris Parrish (kitparrish)
2011-04-25 19:01:40 CDT (-0400)

Striking specimens and photo! Sharnoff photos of Porpidia crustulata show this remarkable pattern of concentric rings of black lecideine apothecia set off against a whitish background, but these MO Observations of Rhizocarpon concentricum show a similar pattern, and the “Lichens of North America” mentions examples in a few other genera as well. You have to wonder what sort of biology is at work here producing such symmetry. They might be “growth rings” in some sense, but lichens grow so slowly that I have to imagine that they are not “annual” growth rings.

Created: 2011-04-25 16:11:26 CDT (-0400)
Last modified: 2011-04-27 02:07:26 CDT (-0400)
Viewed: 110 times, last viewed: 2019-02-12 08:46:43 CST (-0500)
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