A proper phytogeographic affiliation of Antarctic
lichen species has become feasible using molecular
phylogeographic methods. Caloplaca citrina is a heterogeneous
taxon including several species which occurs in
polar regions and is common in Antarctica. Collections of
C. citrina from the Antarctic were revised using morphological,
anatomical and molecular characters (ITS). They
were found to belong to two species: Caloplaca darbishirei
(C.W. Dodge & G.E. Baker) Cretz. and C. soropelta (E.S.
Hansen, Poelt & Søchting) Søchting. The molecular phylogeny
showed them to be sister species, but well separated.
Morphological and chemical characters, ecology and
distribution of the species are discussed. C. darbishirei is
the most common species in the Antarctic, and it is so far
known only from Antarctica and Southern South America.
C. soropelta, reported here as new to South America, is a
bipolar species with all close relatives in the Southern
Hemisphere; it is therefore most likely that the species
colonized the Arctic from the south. C. citrina s. str. is not
confirmed to occur in Antarctica. The study emphasizes the
suitability of genotyping for understanding the taxonomy
and phylogeography of bipolar lichens.
