Observation 163519: Pertusaria heterochroa (Müll. Arg.) Erichsen
When: 2014-03-23
Who: zaca
No herbarium specimen

Notes: “Better late, than never!”
This is a translation of a Portuguese dictate, that can be understood by anyone.
In recent years I made several observations of Pertusaria spp. . For many of those I complained about the result given by the Pertuasaria key available for the zone where I live: “Compiled identification key to the genus Pertusaria and some confusible taxa in Europe and the Mediterranean”, available at
whose first sentence is: “The genus Pertusaria is incompletely known, particularly in the Mediterranean, and this key does not intend to solve the problems, it only wants to bundle the available information.”
Due to the difficulty in applying this key to the specimens found, I was leading to tentatively apply another key, in principle aplicable to the whole world:
A Preliminary World-wide Key to the Lichen Genus Pertusaria, by A.W. Archer & J.A. Elix, available at
without success, as remarked in some of my observations.
Recently, by chance, a paper by published in
MYCOTAXON, Volume LXXXVIII, pp. 471-492, 2003 , by
came to my knowledge, with the impressive title
In this paper I found answers for some of my previous doubts, namely about corticolous species with light coloroured thallus – whitish to yellowgreen, greyish green or yellowish green – with some unusual chemistry, as is the case of the specimens of this observation, producing as results of spot tests:
C+ orange, K- or K+ light yellow, KC+ yellow/orange;
and having 2 spored asci, more or less striated.
As explained throughout the paper such characteristics are common to a complex of different taxa:
P. dispar, P. heterochroa, Pertusaria sp. 1 and Pertusaria sp. 2,
where for the latter two no names are giving, in one case by considering that the difference is not sufficient to be consider a different species from an existing one and, in the other case, by requiring further study. It must be remarked that the first of the above taxa, P. dispar, is only known from Portugal (where it happens that I was born) and from the Balearic Islands in Spain.
I must say that I encountered a problem with the application of the key given there, which as influence for this observation: Supposing that choice 12 is in force (i.e., Thallus K+ yellow or K- and ascospores < 150 um), where to consider specimens with K- reaction (which I think is the case of the specimen considered here)? The alternatives in 13 are: KC+ yellow or KC+ orange (go to 14) and Thallus K+ yellow (go to 15), It cannot be in the first since in 14
one has to choose between K+ yellow (plus something) and K+ pale yelow (plus something).
In the case of the specimen of this observation, considering the note above as a typo or misprint, the key in the above cited paper leads to P. heterochroa, since the (whole) hymenium has no reaction to the application of C or K. However, another problem appear in spores measurements. I had only photos of 6 spores, but none of them, with one exception, had lenght or widht below the maximum given in paper for P. heterochroa (120 um and 45 um, respectively). Here are the values obtained:
107.75 46.64
128.49 45.00
130.69 49.05
125.13 47.35
134.30 60.05
126.91 45.39
Maybe this is due to a non proper calibration of my scope or to the values given in the paper have been obtained with a limited number of specimens. Anyway, I’m now more convinced about the result than never was in the past.


Specimen growing on birch.
Chemical reactions;
Apothecial sections;
Hymenium without any reaction to the apllication of C (above) and K (below);

Proposed Names

86% (1)
Eye3 Eyes3
Used references: See the Notes.
Based on microscopic features: See the Notes and the photos attached.
Based on chemical features: See the Notes and the photos attached.

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Eye3 = Observer’s choice
Eyes3 = Current consensus


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Created: 2014-04-16 18:09:27 PDT (-0700)
Last modified: 2014-04-16 18:52:54 PDT (-0700)
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