Abstract
Ostropales sensu lato is a large group comprising both lichenized and non-lichenized fungi, with several lineages expressing optional lichenization where individuals of the same fungal species exhibit either saprotrophic or lichenized lifestyles depending on the substrate (bark or wood). Greatly variable phenotypic characteristics and large-scale phylogenies have led to frequent changes in the taxonomic circumscription of this order. Ostropales sensu lato is currently split into Graphidales, Gyalectales, Odontotrematales, Ostropales sensu stricto, and Thelenellales. Ostropales sensu stricto is now confined to the family Stictidaceae, which includes a large number of species that are poorly known, since they usually have small fruiting bodies that are rarely collected, and thus, their taxonomy remains partly unresolved. Here, we introduce a new genus Ostropomyces to accommodate a novel lineage related to Ostropa, which is composed of two new species, as well as a new species of Sphaeropezia, S. shangrilaensis. Maximum likelihood and Bayesian inference analyses of mitochondrial small subunit spacers (mtSSU), large subunit nuclear rDNA (LSU), and internal transcribed spacers (ITS) sequence data, together with phenotypic data documented by detailed morphological and anatomical analyses, support the taxonomic affinity of the new taxa in Stictidaceae. Ancestral character state analysis did not resolve the ancestral nutritional status of Stictidaceae with confidence using Bayes traits, but a saprotrophic ancestor was indicated as most likely in a Bayesian binary Markov Chain Monte Carlo sampling (MCMC) approach. Frequent switching in nutritional modes between lineages suggests that lifestyle transition played an important role in the evolution of this family.
Highlights
Lichenization is a successful lifestyle, forming a stable symbiotic association between fungi with cyanobacteria and/or algae
Ostropomyces differs from Ostropa in the presence of perithecial ascomata, presence of periphysoids, which are present in the inner face of the wall, in the lack of an apical cap in the ascus and four-spored asci
Sphaeropezia was placed in Stictidaceae based on molecular data and some Bryodiscus species, which had been recorded as parasites on mosses, were transferred to Sphaeropezia [18]
Summary
Lichenization is a successful lifestyle, forming a stable symbiotic association between fungi with cyanobacteria and/or algae. Lecanoromycetes is the largest lichenized lineage in Ascomycota, comprising more than 15,000 species [1,13,14,15]. It currently contains four subclasses: Acarosporomycetidae, Lecanoromycetidae, Ostropomycetidae, and Umbilicariomycetidae [1,16]. Within subclass Ostropomycetidae, Ostropales sensu lato exhibits a remarkable transition toward larger, non-lichenized, saprotrophic or biotrophic lineages, including a loss of lichenization within Stictidaceae, making this group the most striking example comprising secondarily delichenized lineages in Lecanoromycetes [1,3,13,17,18]. We provide updated multi-gene phylogenetic analyses for Ostropales and related orders focusing on Stictidaceae, thereby describing a newly discovered genus and three new species. Ancestral character state analysis was performed to assess the origin and transition of the various lifestyles occurring in the family
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