Acrocalymmaceae (Pleosporales) from freshwater habitats in Thailand with the introduction of <i>Acrocalymma bilobatum</i> sp. nov.

An observation of lignicolous freshwater fungi in Thailand resulted in the discovery of a novel taxon and recollection of Acrocalymma aquaticum. Morphology coupled with phylogenetic analysis support the placement of the new species in Acrocalymma. Acrocalymma bilobatum sp. nov. resembles A. ampeli, A. bipolare, and A. medicaginis in conidial shape and the mucoid appendages at both ends but differs in the sizes of conidia and appearance of appendages. Phylogenetic analysis of SSU, LSU, ITS, and TEF1-α sequence data shows that A. bilobatum is closely related to A. bipolare, A. chuxiongense, A. medicaginis, and A. pterocarpi. Acrocalymma aquatica was recollected in Thailand and a detailed description and photographic documentation of its morphological characteristics is provided. The herbarium specimen of Acrocalymma fici, collected from freshwater habitats in Thailand, was reexamined to complete a review of Acrocalymmaceae species in the country.