Abstract
The new species Requienella populi in the Requienellaceae is described from Western Norway. Multigene analysis of the four molecular markers ITS, LSU, RPB2 and TUB revealed it as a strongly supported sister clade within the genus. The new species appears to be restricted to old aspen Populus tremula trees and can be morphologically distinguished by submuriform and somewhat smaller ascospores compared to the other species of the genus. A table comparing species of Requienella is provided. The Requienellaceae received a moderate statistical support as a sister group to the Cainiaceae in our analysis and the circumscriptions of the two families need to be studied further using additional genetic markers. Citation: Andreasen M, Jordal JB, Nordén B (2025). Requienella populi sp. nov. (Requienellaceae, Xylariales) from the bark of living aspen trees in Western Norway. Fungal Systematics and Evolution 15: 225-234. doi: 10.3114/fuse.2025.15.10.