<i>Requienella</i> <i>populi</i> <i>sp. nov.</i> (<i>Requienellaceae</i>, <i>Xylariales</i>) from the bark of living aspen trees in Western Norway

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