Supplemental files: Q-Q plots and Shapiro-Wilk tests of normality

Symphyotrichum (Asteraceae) is a well-circumscribed genus on the basis of morphological and molecular data, but species boundaries remain poorly understood. Here, the species delimitation of the contentious Symphyotrichum subulatum group (Symphyotrichum subg. Astropolium) is illuminated using morphometric, phylogenomic, and geographical analyses. Symphyotrichum mexicanum sp. nov., a new species endemic to central Mexico, is described and distinguished from Symphyotrichum expansum based on its morphometric attributes, phylogenetic placement, geographic range, and ecological specialization.