Oral Paper

         Systematics

Species delimitation in the Symphyotrichum subulatum group (Asteraceae) reveals a new species in central México

Presenting Author
Sushil Dahal
Description
Symphyotrichum is a well-circumscribed genus within Asteraceae based on morphological and molecular data, but species boundaries remain poorly understood. Several subgeneric classifications have been proposed for the North American taxa of Symphyotrichum. Symphyotrichum subgenus Astropolium (the annual and perennial salt marsh asters), among the most geographically widespread radiations in the genus, has proven to be among the most problematic, with two primary competing classification proposals. Sundberg (1986) divided into three North American species in the Flora of North America (FNA) treatment. Nesom (2005), while consistent with Sundberg in the number of taxa recognized, presents justifications for the recognition of these taxa at the species level. The primary justification of Brouillet et al. (2006) for treatment at the varietal rank appears to be evident morphological intermediates, yet they also note that these taxa are “nearly entirely allopatric” and “mostly reproductively isolated” based on data from Sundberg (1986) that were interpreted as evidence for species-level distinctions by Nesom (2005). No newer classification framework has been proposed for subgenus Astropolium since Nesom (2005) and Brouillet et al. (2006), yet the foregoing indicates that uncertainty remains and the group merits further study. Here, I illuminate the species delimitation of the contentious S. subulatum group (S. subg. Astropolium) 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.