Towards a natural classification of Astrosphaeriella-like species; introducing Astrosphaeriellaceae and Pseudoastrosphaeriellaceae fam. nov. and Astrosphaeriellopsis, gen. nov.

Abstract

Astrosphaeriella sensu lato is a common genus occurring on bamboo, palms and stout grasses. Species of Astrosphaeriella have been collected from various countries in tropical, subtropical or temperate regions. In Asia, species have been collected in Brunei, China, Indonesia, Japan, Philippines and Vietnam. There have been several morphological studies on Astrosphaeriella, but molecular work and phylogenetic analyses are generally lacking. Taxa included in Astrosphaeriella were characterized in three main groups 1) typical Astrosphaeriella species (sensu stricto) having carbonaceous, erumpent, conical ascostromata 2) atypical Astrosphaeriella species (sensu lato) having immersed, coriaceous ascostromata with short to long papilla and 3) lophiostoma-like species having immersed ascostromata with slit-like openings. Some of the latter Astrosphaeriella species, having slit-like openings, have been transferred to Fissuroma and Rimora in Aigialaceae. In this study five type specimens of Astrosphaeriella were loaned from herbaria worldwide and re-examined and are re-described and illustrated. Collections of Astrosphaeriella were also made in Thailand and morphologically examined. Pure cultures were obtained from single spores and used in molecular studies. The asexual morph was induced on sterile bamboo pieces placed on water agar. Phylogenetic analyses of combined LSU, SSU and TEF1 sequence data of astrosphaeriella-like species using Bayesian, Maximum parsimony (MP) and Randomized Accelerated Maximum Likelihood (RAxML) analyses were carried out. Phylogenetic analyses show that species of Astrosphaeriella can be distinguished in at least three families. Species of Astrosphaeriella sensu stricto with erumpent, carbonaceous ascostromata, form a strongly supported clade with Pteridiospora species and a new family, Astrosphaeriellaceae, is introduced to accommodate these taxa. The genera are revised and Astrosphaeriella bambusae, A. neofusispora, A. neostellata, A. thailandica, A. thysanolaenae and Pteridiospora chiangraiensis are introduced as new species. Astrosphaeriella exorrhiza is reported on a dead stem of Thysanolaena maxima and is the first record for Thailand. Reference specimens for A. fusispora and A. tornata are designated to stabilize the taxonomy of Astrosphaeriella. The coelomycetous asexual morph of A. bambusae is reported and forms hyaline, globose to subglobose, aseptate conidia. Species of Astrosphaeriella sensu lato with immersed, coriaceous ascostromata, with short to long papilla and striate ascospores, form a sister clade with Tetraplosphaeriaceae. The genus Pseudoastrosphaeriella is introduced to accommodate some of these taxa with three new species and three new combinations, viz. P. aequatoriensis, P. africana, P. bambusae, P. longicolla, P. papillata and P. thailandensis. A new family Pseudoastrosphaeriellaceae is introduced to accommodate this presently monotypic lineage comprising Pseudoastrosphaeriella. The asexual morph of P. thailandensis is described. Astrosphaeriella bakeriana forms a distinct clade basal to Aigialaceae. Astrosphaeriella bakeriana is excluded from Astrosphaeriella and a new genus Astrosphaeriellopsis, placed in Dothideomycetes genera incertae sedis, is introduced to accommodate this taxon. Fissuroma aggregata (Aigialaceae) is re-visited and is shown to be a cryptic species. Three new species of Fissuroma and a new combination are introduced based on morphology and phylogeny viz. F. bambusae, F. fissuristoma, F. neoaggregata and F. thailandicum.