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Abstract
The lichen genus Cetrelia represents a taxonomically interesting case where morphologically
almost uniform populations differ considerably from each other chemically. Similar
variation is not uncommon among lichenized fungi, but it is disputable whether such
populations should be considered entities at the species level. Species boundaries
in Cetrelia are traditionally delimited either as solely based on morphology or as
combinations of morpho- and chemotypes. A dataset of four nuclear markers (ITS, IGS,
Mcm7, RPB1) from 62 specimens, representing ten Cetrelia species, was analysed within
Bayesian and maximum likelihood frameworks. Analyses recovered a well-resolved phylogeny
where the traditional species generally were monophyletic, with the exception of Cetrelia
chicitae and Cetrelia pseudolivetorum. Species delimitation analyses supported the
distinction of 15 groups within the studied Cetrelia taxa, dividing three traditionally
identified species into some species candidates. Chemotypes, distinguished according
to the major medullary substance, clearly correlated with clades recovered within
Cetrelia, while samples with the same reproductive mode were dispersed throughout
the phylogenetic tree. Consequently, delimiting Cetrelia species based only on reproductive
morphology is not supported phylogenetically. Character analyses suggest that chemical
characters have been more consistent compared to reproductive mode and indicate that
metabolite evolution in Cetrelia towards more complex substances is probable.