Notes: This observation together with observation 165505 and observation 165506 are devoted to a group of crustose lichens growing on a branch of a shrub. This is my first attempt to consider a set of lichens growing together for the purpose of classification. I attached several photos of this group and include one with numbers to distinguish between them (4th photo). They have all different features and at first sight one can immediately say that:
I – Is a Graphidaceae, probably a Graphis or Phaeographis, the latter being more probable, due to the form of apothecia with open discs;
II – Resembles very clearly an Arthonia sp.. Which one? Only microscopy can help.
III – Is somewhat related in appearance to the genus Buellia, if one can confirm that the fruitbodies are apothecia, which is not clear due to their reduced dimensions.
Here the lichen marked as III is under considerartion, the last one of the group and the most difficult to identify, fact that was already apparent from the begining. It was really hard for me to find the genus of the specimen, but at the end I think that that step was successefuly accopmplished. Here are some details:
- The fruitbodies are indeed apothecia;
- Starting the microscopic anlaysis several apparently contradictory data appeared:
1- A photobiont that is a green alga, really green in colour, and not Trentepohlia ;
2- Asci with the form of those in Arthonia, maybe a bit more elongated;
3- Ascospores 1-septate, hialine when young and brown coloured at maturity, resembling those of Buellia spp..
As I “discover” after some time there is a genus that includes specimens with the above characteristics: Melaspilea. See Ref. 3 for an example of a species with Trebouxia as photobiont.
According to the other references this genus was traditionally employed for crustose lichens with lirelliform apothecia and brown 1-septate, but is very heterogeneous and includes species with rounded (as in this case) or angular apothecia, not slit-like.
This genus is completely unknown for me and lacking a good key for it didn´t permit to go to the species. But maybe this time the species under consideration is not only new for my country as for the world. This is what I conclude when I measured the spores, obtaining the following average values:
Me = 33.1 × 8.4 um ; Qe = 4 (N=20).
In fact, these values correspond to narrow-ellipsoid spores, whereas those in the description of the genus are referred as ellipsoid to sole-shaped. I saw the dimensions of the spores for as many species as I could find in the internet and nothing similar appeared.
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Thanks, Jason, for your opinion. I was really convinced about my proposal, but it could be wrong by something that I didn´t saw or consider.
I arrive at the same conclusions as you — Melaspilea and that this could well be an undescribed species. One point mentioned in British Flora: “asci elongate-clavate, generally thickened at the apex and with an internal apical beak” — this describes your asci perfectly, right down to the long narrow conical “beak” visible in the apical thickening in your photos. This is distinctive enough in my opinion to really lend confidence to the genus Melaspilea (notwithstanding the reservations most lichenologists seem to have concerning its polyphylly). Interesting observation!
Created: 2014-05-12 03:50:41 IST (+0530)
Last modified: 2014-05-29 20:20:06 IST (+0530)
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