The distribution of ascus types and photobiontal selection in Lecanoromycetes (Ascomycota) against the background of a revised SSU nrDNA phylogeny

Abstract

Within the last decade, molecular methods have revealed the relationships in many groups of lichenized Ascomycetes. However, the published phylogenies were often contradictory with respect to higher taxonomic levels. To achieve a more convincing overall picture of phylogenetic relationships of and within the Lecanoromycetes, we set up an alignment of all publicly available SSU nrDNA sequences of the Pezizomycotina, discarded those of insufficient quality, and added 21 newly obtained sequences representing groups that were not or under-represented so far. The alignment of 635 taxa and a subset of 166 Lecanoromycetes were analysed with different phylogenetic algorithms. The best phylogenetic trees, with respect to length, resolution, and support, were obtained with the Parsimony Ratchet method and DNAPARS (Phylip). According to these results, the Lecanoromycetes were subdivided into eight monophyletic clades representing the following orders: Acarosporales ad. int., Agyriales, Baeomycetales, Gyalectales, Icmadophilales ad. int., Lecanorales, Ostropales, and Pertusariales. These clades are distributed in two monophyletic groups corresponding to the two different types of ascomatal ontogeny. The taxa of the Lecanorales-clade differ from the other orders by the absence of a primary cyanobiont and of phycobionts of the genera Coccomyxa and Trentepohlia, in combination with the presence of an amyloid reaction of the ascus tips (lacking amyloid flanks). The Lecanorales-clade is subdivided into nine groups which are treated here at the level of suborders: Lecideineae, Teloschistineae, Physciineae, Bacidiineae ad int., Sphaerophorineae ad int., Rhizocarpineae ad int., Psorineae ad int., Cladoniineae, and Lecanorineae. The amyloid reaction pattern of the ascus apex correlates with this grouping at suborder rank. Peltigerales were excluded from the Lecanorales but included in the Lecanoromycetes based on morpho-anatomical features. The Lichinales were excluded from the Lecanoromycetes, while the position of the Umbilicariaceae remains unclear.