Abstract
The lichen Lecanora somervellii Paulson,
first described from the northern slopes of Mt Everest in Tibet, has been
collected at four other localities in the High Himalayas, at altitudes
between 3750 and 5540 m. As the type material appears to be missing, a
neotype is designated here. The species has an unusual lemon yellow colour
due to the pigment calycin; this compound is in addition to usnic acid,
which is widespread in Lecanora.
Lecanora somervellii is otherwise very
similar in essential characters to the complex including
Lecanora concolor Ram. and L.
orbicularis (Schaerer) Vainio, high alpine species
well-known, for example, from the Alps. It is supposed, that L.
somervellii is derived from this aggregate by the
production of calycin (in addition to usnic acid), which acts as an
additional protective pigment at these very high altitudes.
