PART 1

XANTHOPYRENIACEAE Zahlbr.
It has been suggested that this family should be synonymized with the Arthopyreniaceae. I prefer to keep
it separate on the basis of physes which are more intricately and densely branched and interconnected,
differently shaped asci, differently shaped ascospores and elliptical (not rod-shaped) microconidia. The
differences do not seem major but I think that the relationships of the Xanthopyreniaceae probably lie
elsewhere in some "non-lichenized" family. Also since I have invested considerable energy in making the
Arthopyreniaceae homogeneous, I am reluctant to "mess it up". The inclusion of Zwackhiomyces is basically
arbitrary. There are few useful characters avaiable to place these simple/highly reduced taxa. Essentially
there are no characters which would exclude Zwackhiomyces from the Xanthopyreniaceae but equally there
are no unique shared characters to support inclusion. Collemopsidium Nyl. and Didymellopsis (Saccardo)
Clements & Shear are also homeless and if the positioning of Zwackhiomyces in the Xanthopyreniaceae
works out, perhaps, they too could be dumped here.
1. Associated with cyanobacteria; pigment in ascomatal wall amorphous, located
in the hyphal cell wall; ascospores thin-walled, readily collapsing, not becoming
brownish and granular-roughened .....................................................................................Pyrenocollema
1. Parasitic or parasymbiontic on lichens with green algal photobiont; pigment in
ascomatal wall fine granular, located between hyphae; ascospores with thicker
wall, not readily collapsing (until overmature), becoming brownish and granular
ornamented ..................................................................................................................... [Zwackhiomyces]
PYRENOCOLLEMA Reinke
In my thesis I pointed out the problems involved in defining species in Pyrenocollema. They have not
been resolved and even seem to have worsened. The major unresolved questions are: does the
host/photobiont matter (and therefore does the rock substrate matter, i.e., preference of the cyanobacteria) or
should the taxonomy be based entirely on fungal characters?
1. Fresh water aquatics, semi-aquatics or on rock in moist places...............................................................2
2. Photobiont blue-green in color; on calcareous rock .............................................................................. 3
3. Ascomata sessile to semi-immersed, ascospores 17-23 × 8-11 µm;
eastern United States ..................................................[P. prospersellum (Nyl.) R. C. Harris]
3. Ascomata immersed, with a broad clypeus; ascospores 18-23 × 8-9.5 µm;
Bermuda............................................................................................ [P. farlowii (Riddle) R. C. Harris
2. Photobiont yellow brown to brown due to colored sheath (Gleocapsa-like)
or thallus dark brown ............................................................................................................................ 4
4. Growing on limestone; ascspores 16-18(-20) × 5-7 µm; Monroe County
(Key West), Puerto Rico.............................................................P. atlanticum (Vainio) R. C. Harris
4. Growing on a variety of rock, usually ± aquatic; ascospores
(18-)20-27 × 8-11 µm; temperate North America, Europe ..................................................................
.....................................................................................[P. tichothecioides (Arnold) R. C. Harris s. lat.]
1. Marine, in tidal zone ....................................................................... [P. halodytes (Nyl.) R. C. Harris s. lat.]
[In my thesis I took a very broad view of this species. It is divided in Purvis et al. (1992) as follows.
I am not sure at this time how this view applies in North America.
A. On calcareous rocks or shells; clypeus absent or not spreading;
ascomata not cracked around ostiole ................................................................................................B
67