Abstract
Neoastrosphaeriella aquatica (Aigialaceae, Dothideomycetes) is a new species isolated from submerged wood in freshwater habitats in southern Thailand. The species is characterized by black, carbonaceous, semi-immersed ascomata, bitunicate, fissitunicate, cylindric-clavate or obclavate, short pedicellate asci and fusiform, hyaline to grayish brown, ascospores tapering to pointed apices, and surrounded by thin, distinct sheaths. Neoastrosphaeriella aquatica can be distinguished from other species of Neoastrosphaeriella by its large, hyaline to grayish brown, guttulate ascospores. Phylogenetic analysis of a combined sequence dataset of the ITS, LSU, SSU and TEF1-α indicates that it is closely related to N. krabiensis and N. sribooniensis, but N. aquatica has sufficient nucleotide differences to be recognized as a new species.