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2. Taxonomic part 26
2. 5. 4. Chemistry
In the majority (approximately 70%) of the species secondary compounds are present,
whereas in Graphidaceae s. str., lichen substances occur less frequently (Staiger 2002). The
majority of compounds are β-orcinol depsidones; in addition, orcinol depsides (chiefly
occurring in Diploschistes), xanthones, anthraquinones (and other pigments) and several
unidentified substances are known.
The taxonomic relevance of secondary compounds in lichenized fungi was controversially
discussed in numerous publications (e.g., Brodo, 1978; Culberson, 1969, 1986; Culberson &
Culberson, 1976, 1994; Hawksworth, 1976; Elix, 1993; Elix & al., 1986; Esslinger, 1977,
1989; Feige & Lumbsch, 1995; Lumbsch, 1998a, b; Rogers, 1989). Particularly at the species
level, the taxonomic interpretation of chemical differences remains problematic and needs
further molecular studies. In the present treatment, morphologically indistinguishable
chemotypes were consistently regarded conspecific and designated to chemical strains.
In the following, a compilation of detected compounds is provided, grouped in compound
classes and chemosyndromes (where present). Newly identified substances (Elix, pers. com.)
or unknown substances are marked with an asterisk and specified in a separate table. For Rfvalues
and spot characteristics of the known substances see Elix & al. (1995, 2000c) and
Huneck & Yoshimura (1996).
β-Orcinol depsidones
Salazinic acid
Detected as singular, major compound in Thelotrema circumscriptum and ‘Leptotrema’
schizoloma (strain II).
Stictic acid chemosyndrome
Includes variable concentrations of α -acetylconstictic, α-acetylhypoconstictic,
consalazinic, constictic, cryptostictic, hypoconstictic, hyposalazinic, hypostictic and stictic
acids. Predominant major compounds are constictic, hypostictic and stictic acid. In
‘Thelotrema’ zebrinum substances of the protocetraric acid chemosydrome can co-occur. It is
the most common chemosyndrome in the non-ocellularioid taxa (in Ocellularia s. lat. it is
very rare), detected in 36 species of all genera except Fibrillithecis, Pseudoramonia and
Reimnitzia:
Chapsa lordhowensis, C. megalophthalma, C. megaphlyctidioides, C. minor, C.
phlyctidioides, C. platycarpa, Chroodiscus australiensis, C. parvisporus, Leucodecton
albidulum, L. compunctellum, L. glaucescens, L. subcompunctum, Melanotopelia rugosa,
Myriotrema desquamans (strain I), M. eminens, M. phaeosporum, M. trypaneoides,
Nadvornikia hawaiensis, Thelotrema alboolivaceum, T. bicinctulum, T. capetribulense, T.
crassisporum, T. cupulare, T. cyphelloides, T. leucophthalmum, T. myriocarpum, T.
porinoides, T. thesaurum, T. triseptatum, Topeliopsis azorica (strain I), T. darlingtonii, T.
elixii, T. kantvilasii, T. tasmanica, ‘Thelotrema’ guadeloupensis (strain I), ‘Thelotrema’
zebrinum.
Norstictic acid chemosyndrome
Includes variable concentrations of connorstictic, norstictic and subnorstictic acids, rarely
with co-occurring substances of the stictic acid chemosyndrome (α-acetylconstictic,
hyposalazinic and stictic acid). The predominant major compound is norstictic acid. Detected
in six species of the genera Leucodecton, Myriotrema and Thelotrema:
Leucodecton occultum, Myriotrema frustillatum, Thelotrema bicavatum, T. eungellaense,
T. gallowayanum, T. porinaceum.