Triterpene chemosyndromes and subtle morphological characters characterise lineages in the Physcia aipolia group in Australia (Ascomycota)

Abstract

Species delimitation in lichens of the Physcia aipolia group in Australia has been studied based on thalline morphology (lobe width, upper surface pruinosity) and medullary triterpene chemistry as main character complexes. Previous treatments have utilised the presence or absence of atranorin and zeorin in the medulla as useful discriminators, but have neglected utilising the diversity of medullary triterpenes for taxonomic purposes. We have now tested the phylogenetic patterns of distribution of subtle morphological characters and terpenoid chemistry by means of molecular phylogenetic analysis of nuclear ITS and mitochondrial SSU rDNA sequences. Our analysis supports triterpene chemosyndromes and subtle morphological characters for the distinction of distinct lineages. Three new species are described for Australia, P. austrostellaris Elix, P. littoralis Elix and P. tropica Elix. In addition, the detailed chemical variation of species within the group is documented and three major chemosyndromes of triterpenes have been identified.