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

<p><em>Symphyotrichum</em> (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 <em>Symphyotrichum</em> <em>subulatum</em> group (<em>Symphyotrichum</em> subg. <em>Astropolium</em>) is illuminated using morphometric, phylogenomic, and geographical analyses. <em>Symphyotrichum mexicanum</em> sp. nov., a new species endemic to central Mexico, is described and distinguished from <em>Symphyotrichum</em> <em>expansum</em> based on its morphometric attributes, phylogenetic placement, geographic range, and ecological specialization.</p>