Taxonomy and phylogeny of Lichen-Like fungi in Ascomycota

Abstract

Lichens are one of the most successful lifestyle among Ascomycota showing symbiotic association between fungal and algal/cyanobacterial partners. This mutualistic group harbours many unrelated organisms also show lichen-like associations. The lichen definition has been controversial for long time due to the range of doubtful associations between photobiont and mycobiont. Borderline lichens are a poorly studied group that forms loose association between photobiont and mycobiont and are often associated with lichenized group. The taxa morphologically vary from lichens in that they lack true thallus (upper and lower cortex, medulla and photobiont) and often form inconspicuous crustose thallus-like structure; the photobionts are sometimes scantly present or apparently absent. Borderline lichens are mostly overlooked in the field due to their inconspicuous thalli. The phylogenetic placement of many taxa remains uncertain due to absence of molecular data, whilst the species with molecular data add enormous phylogenetic diversity by clustering with largely lichenized and non-lichenized group. The nutritional transitions of borderline lichens have not yet been clearly accounted for and are often referred to as non-lichenized saprotrophic which are chiefly recorded from young twigs and barks. Borderline lichens are also generally referred to as doubtfully lichenized, facultatively lichenized or non-lichenized fungi.

Borderline lichens are evolutionarily derived through delichenization and relichenization. However, their origin is largely unknown as many species are yet to be described and are an important element in reconstructing the evolutionary history of lichenized lineages. Another important group is non-lichenized saprotrophs which are derived from lichenized ancestors. They mostly occur on wood and phylogenetically closely associated with lichenized lineages and are often found in Stictidaceae in the largest lichenized class Lecanaromycetes. This study provides a historic perspective of borderline lichen and non-lichenized saprotrophs with notes on their morphology, ecology, lifestyle in Ascomycota. The novel and existing borderline lichens and nonlichenized saprotrophs were investigated based on morphological and molecular approaches in the classes Arthoniomycetes, Dothideomycetes, Eurotiomycetes and Lecanaromycetes. Mitochondrial, nuclear ribosomal and protein coding genes are used in the phylogenetic analyses. Ancestral character analyses were conducted to check the possible gains and losses in the investigated groups.

Non-lichenized genus Naevia belongs to Arthoniaceae is resurrected for three non-lichenized taxa. Phylogenetically closely related lineage to Naevia also comprises several non-lichenized species which resemble Mycoporum also discussed. A new genus Ostropomyces is introduced to accommodate for two new species namely O. pruinosellus and O. thailandicus as well as a new species Sphaeropezia shangrilaensis within Stictidaceae. The type species of Arthopyrenia, A. cerasi sequenced for the first time in this study, and thus Arthopyreniaceae is synonymized under Trypetheliaceae based on morpho-molecular assessments. Phylogenetically and morphologically closely related taxon Julella fallaciosa also synonymized under Arthopyrenia. character analysis. A new saprotrophic species Mendogia diffusa is described within Dothideomycetes. The taxon was facultatively associated with algae and collected from dead leaves of Fagales in Thailand. The new taxon is investigated based on morphological and molecular analyses and the key for known species of Mendogia is also provided. The mazaediate, saprotrophic and monotypic genus Pyrgidium was assigned within Mycocaliciales yet the phylogenetic placement of the genus remains uncertain due to the absence of molecular data. Pyrgidium is investigated based on morpho-molecular approaches from the fresh collection from Brazil and Thailand. The ascospores diversity of the members is investigated with the aid of SEM and compound microscopic photographs. This study is further investigated new and existing species belong to lichenized, lichenicolous and saprotrophic fungi collected from China and Russia based on morpho- molecular approaches. In addition, we also provided the latest checklist for freshwater lichens and lichen-like fungi and discussion about their biology