Lately I have been involved in the observation of lichens with lirellas, more specifically of Graphidaceae family.
This is an old passion renewed a few months ago where I was confronted several times in the field with specimens that did not fit in the existing descriptions. Later (May 1st, 2014) came to observe a mythical species in that family of lichens: Glyphis cicatricosa. Along with it and in the trees nearby other lirellate lichens developed with distinct lirellas from those of known species. It was the tip of the iceberg, that did rekindle my fondness for these lichens and led me to make specific field trips to observe them. As an example I mention that only in two field trips observed over 50 specimens of the genus Graphis. Of course, not all are of different species and it is also clear most of them should belong to the species mentioned as existing here, but ….
Following this interest, I had access to the reference work of the genus Graphis (see Ref. 1) dedicated to a world key for Graphis and an article where the main features relevant for classification are described and analysed (see Ref. 2). Reading these references completely changed my way of seeing this kind of lichens and started to do a review of previous observations (that I will make here at MO in the near future).
I make use of this observation as a model to examplify the use of the key applied to a species that “everyone” refers to exist here: Graphis elegans.
Following Ref. 2: “In the sense of Staiger (2002), Graphis is defined as having lirellate ascomata with well-developed, usually convergent labia and mostly closed disc, partly to fully carbonized excipulum, mostly non-inspersed hymenium, hyaline, transversely septate to muriform amyloid ascospores that react I+ violet-blue, and a usually corticate, mostly white-grey thallus”.
The key in Ref. 1 is organized in 20 groups, which depend on the following features: 1) Pigmentation (of the ascomata or of the hymenium), 2) Striation or not of lirellas, 3) Level of exciple carnonization, 4) Inspersion or not of hymenium, 5) Ascospores transversaly septate or muriform. Before the key the so-called “morphs” are introduced, corresponding to some special arrangement of the morphological features, and that are transversal to the organization of groups. At the group level other features are needed : like chemistry, size of the ascospores and their septation, and others.
For the case of this specimens, they belongs to Group 15 characterized as follows:
Group 15: Labia striate, excipulum laterally carbonized, hymenium clear, ascospores transversely septate
Attached you can find a photo (labelled “Group 15:…”) with all the details necessary to reach this conclusion. The evolution in the key for this group is the following:
1 Norstictic or stictic acid or lichexanthone (K+ yellow or K+ yellow forming red crystals or UV+ yellow) . . . . . . 2
2 Norstictic or stictic acid (K+ yellow or K+ yellow forming red crystals, UV–); lirellae variable. . . . . . . . . . 4
4 Norstictic acid (K+ yellow forming red crystals); ascospores (small to) medium-sized to large (35–150 μm long). . . 5
5 Ascospores (small to) medium-sized (35–60 μm long), 7–13-septate, conspicuously thick-walled and often somewhat greyish; lirellae erumpent to prominent, lacking thalline margin, short and sparsely branched (striatula-morph); subcosmopolitan . . . . . . . . . . . . . Graphis elegans (Sm.) Ach.
In addition note that G. elegans is only of the very few species of Graphis with conspicuous thick-walled ascospores.
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Created: 2015-02-24 17:34:45 CST (-0600)
Last modified: 2015-02-24 17:34:54 CST (-0600)
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