Message - 7th IAL Symposium

The 7 th International Association for Lichenology Symposium 2012
(3A-O5) Submission ID: IAL0044-00001
DELIMITING PHYLOGENETIC SPECIES AMONG EUROPEAN TAXA OF THE GENUS USNEA
Tõrra T. 1 , Saag L. 2 , Randlane T. 1 , Del-Prado R. 3 , Saag A. 1
1 Department of Botany, University of Tartu, Tartu, Estonia
2 Molecular Evolution Workgroup, Estonian Biocentre, Tartu, Estonia
3 Departamento de Biología Vegetal II, Universidad Complutense, Madrid, Spain
The study focuses on European Usnea (Parmeliaceae) species with sorediate shrubby thalli, with the
aim to evaluate the validity of morphology and chemistry based separation of several widely recorded species
(U. diplotypus, U. fulvoreagens, U. glabrescens, U. lapponica, U. subfloridana, U. substerilis, U. wasmuthii). 22
Usnea species, identified according to morphological and chemical characters, were studied using maximum
parsimony and Bayesian analyses of ITS and beta-tubulin sequences. Pairwise maximum likelihood distances
(given as number of nucleotide substitutions per site) were calculated among the ITS sequences. The distances
between the haplotypes of different species (interspecific distances) and distances between haplotypes within
each species (intraspecific distances) were calculated, with the aim to estimate the thresholds between these
distance ranges. The analyses showed that: (a) most taxa that are morphologically well distinguished are also
distinct by means of molecular characters, (b) shrubby taxa in the section Usnea that are difficult to determine
by traditional characters, form a group of closely related but still genetically distinct species, except U. diplotypus
and U. substerilis which appear polyphyletic. The branch lengths differed largely between two parts (sections
Usnea and Ceratinae) of the ITS tree and thus genetic distances were calculated separately for them. In clade A
(section Usnea), the intra- and interspecific distance ranges were considerably smaller than in clade B (section
Ceratinae), however, the distances can be used for species delimitation in both clades. In clade A the threshold
for interspecific distances is close to 0.01 s/s; in clade B the threshold is around 0.02 s/s. The interspecific distance
threshold for clade A in our study is close to the according threshold established for parmelioid lichens.
Our estimate for clade B is higher than in parmelioid group and within the range reported by Lumbsch (2002) for
intrageneric distances in Parmeliaceae. Comparison of inter- and intraspecific genetic distances offers useful
criterion for delimiting species, however, more material should be analyzed to make reliable taxonomic decisions
in the genus Usnea. We also observed that the use of chemical characters for species determination was often
complicated as the variability of secondary metabolites was higher than previously known.
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