Abstract
This study introduces six new Amphisphaeria species, discovered on dead twigs belonging to Calophyllaceae, Fabaceae, Sapotaceae, and Theaceae in northern Thailand, based on a morpho-phylogenetic approach. Our newly introduced Amphisphaeria species share morphological traits with other members of the genus, featuring ascomata with a two-layered peridium and unitunicate asci with either J+ or J- apical ring. The newly identified species Amphisphaeria mesuae, A. mimusopis, A. paraserianthis, A. pseudomicheliae, A. pterocarpi, and A. schimae differ from previously known Amphisphaeria species in Amphisphaeriaceae. This distinction is supported by combined analyses using maximum likelihood and Bayesian inference of nuclear ribosomal large subunit rDNA (LSU) and the internal transcribed spacer (ITS) sequence matrix. Amphisphaeria mesuae can be distinguished from A. ailaoshanensis by the presence of larger ascomata, smaller asci, ellipsoidal ascospores, and the absence of a sheath surrounding the ascospores. Amphisphaeria mimusopis differs from its phylogenetically related sister taxon by possessing smaller asci, larger ascospores, and narrower paraphyses. Amphisphaeria paraserianthis differs from closely related taxa in its ostiolate ascomata and 3-septate ascospores. Amphisphaeria pterocarpi can be distinguished from the taxon with which it clusters by having smaller ascomata and ascospores. Amphisphaeria pseudomicheliae has larger ascomata and asci, but smaller ascospores, compared to its sister taxon, A. micheliae. Amphisphaeria schimae differs from closely related taxa in its larger ascomata, asci, and ascospores. Amphisphaeria micheliae was also collected here and is reported as a new record on Senna siamea. This study contributes to the expansion of the taxonomic framework of Amphisphaeria.