Abstract
Usnea aurantiaco-atra is the dominant flora around King George Island, Antarctica, whose specimens exhibited various phenotypes, even for those with the
same ITS sequences in both mycobiont and photobiont. A comprehensive analysis of morphological traits of U. aurantiaco-atra including the reproductive structures, growth
forms and ornamentation, cross section of the branches, and the substratum was carried out. Four arbitrary groups were identified based on their reproductive characters, but
these groups cannot be distinguished from molecular phylogenetic trees based on fungal
or algal ITS sequences. Further, the complicated morphological diversity of the thalli
with the same ITS haplotypes in both mycobiont and photobiont suggest that some other
factors in addition to the symbionts could influence the morphology of lichens. This
implies that lichen is indeed a complex-mini-ecosystem rather than a dual symbiotic
association of fungus and alga. Also, a lichenous fungi Phacopsis sp. was identified
based on its anatomical characters and ITS sequence, which was also responsible for
the black burls-like structures on U. aurantiaco-atra.
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