Additions to the Xylariomycetidae (Sordariomycetes) fungal flora from northern Thailand: four novel Amphisphaeria species

In a continuing survey of xylarialean taxa with inconspicuous stromata, seven collections were obtained from twigs and branches at the late stage of senescence or the early stage of decomposition while attached to the host. These materials harbored xylarialean-like fungal structures and were collected during the wet seasons of 2022 and 2023 from forest and agroforestry fields in northern Thailand. Based on morphological examination and multigene phylogenetic analyses using maximum likelihood, maximum parsimony, and Bayesian inference of the internal transcribed spacer, partial 28 S large subunit rDNA, partial RNA polymerase II second largest subunit, and partial β-tubulin genes, four new species, Amphisphaeria longiostiolata, A. planibasalis, A. sanpakiaensis, and A. sribuabanensis, are introduced.

In addition, A. hydei on Casearia sp. and A. oleae on Prunus sp. are reported as new host records, and A. pterocarpi is documented as an additional collection from the region. All taxa are described and illustrated, with detailed morphological comparisons to phylogenetically related species, including taxa with and without available molecular data. In northern Thailand, Amphisphaeria species are predominantly recorded during the wet season, suggesting that seasonal conditions may influence sexual morph development.

The recurrent occurrence of Amphisphaeria on woody substrates during this period suggests a potential endophytic phase and a shift in lifestyle within the genus. Further studies integrating endophytic surveys with ecological and nutritional data are needed to clarify the life history and ecological roles of Amphisphaeria species.