Observation 203954: Xanthoparmelia plittii (Gyeln.) Hale

When: 2015-05-05

Collection location: Atascadero, California, USA [Click for map]

35.4505° -120.6459° 282m

Who: J-Dar

No specimen available

Location is a rural setting in dry grassland/scrub with scattered oaks and pine.
Habitat is a crumbling outcrop of Monterey shale.

Thallus isidiate, soredia absent, apothecia occasional, upper surface greyish, lower surface pale to brown, probably greater than 5cm overall, rhizines sparse. Medulla white with continuous algal layer, K+Y turning orange, not red (which excludes Xanthoparmelia mexicana with salazinic acid, in favor of norstictic or stictic acids). But then how to tell between those two acids? Norstictic takes it to either Xanthoparmelia dierythra or Xanthoparmelia maricopensis, both of which are out of range. So going with stictic acid (Nash V2 couplet 22), it comes down to isidia either cylindrical (Xanthoparmalia plittii) or (sub)globose often with erumpent tips (Xanthoparmelia subplittii). Check out photos, these appear to be closer to globose than cylindrical, but not sure if I see any bursting out of the cortex (erumpent), although they break easily when handled.

This isidiate species co-occurs with a non-isidiate species tentatively identified as Xanthoparmelia novomexicana (observation 203958), which is more abundant at this location.


Shale outcrop
Microscope photo of isidia and lobes
Medulla K+Y turning orange

Proposed Names

28% (1)
Used references: Nash V.2
Based on microscopic features: Isidiate
Based on chemical features: Medulla K+Y turning orange, C-, KC-
56% (1)
Eye3 Eyes3
Based on microscopic features: Some branching isidia present.

Please login to propose your own names and vote on existing names.

Eye3 = Observer’s choice
Eyes3 = Current consensus


Add Comment
You and me both!
By: Jason Hollinger (jason)
2015-05-09 10:58:07 PDT (-0700)

Xanthoparmelia kicks my b*** regularly! :)

By: J-Dar
2015-05-09 10:28:42 PDT (-0700)

I like your decision to weight the ID based on the isidia branching. I also like “Lumpy” as an official lichen morphology term! Since these isidia are pale, can we assume they are younger and moving toward darker color and branching? I see a few in the photos that look like they are splitting into two branches. And with X. plittii supposed to be more common at intermediate forested elevations, and X. subplittii supposed to be more common in desert areas, i’ll change this observation to the former, recognizing that I need to do some more work with these specimens!

I have such problems with this genus
By: Jason Hollinger (jason)
2015-05-06 19:45:53 PDT (-0700)

In particular whether or not specimens are “lobulate” (in the Xanthoparmelia sense). And whether isidia are “globose” or “cylindrical”. Read the descriptions of plittii carefully: note that they start globose and become cylindrical and irregularly branched. By contrast subplittii is “usually” globose, becoming “subcylindrical”, “mostly” unbranched. Ugh. Really? I find irregularly-branched lumpy isidia all the time all over the place… either “cylindrical” is to be taken with a big grain of salt, or plittii is really rare and subplittii is everywhere. But it’s exactly the opposite supposedly. So what are we to do? I’ve been giving most weight to branching. At least that way I end up with X. plittii being much more common, like it should be. Beats me. :(

Created: 2015-05-05 20:49:14 PDT (-0700)
Last modified: 2015-05-09 10:32:26 PDT (-0700)
Viewed: 56 times, last viewed: 2017-06-20 00:35:48 PDT (-0700)
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