The paraphyly of Stellaria alsine (Caryophyllaceae) necessitates taxonomic readjustment

Stellaria alsine Grimm has long been considered a weedy species ranging natively across three continents, with introductions beyond. Phylogenetic evidence suggests that not all populations are closely related, however. Here, I review the evidence supporting the recognition of at least two separate ''alsine-like'' species. The name S. alsine was first used to describe European material in Linnaean times. The name Stellaria undulata was subsequently used to describe morphologically analogous material from the Asian Far East, but this material has long been considered synonymous with S. alsine. These lineages are not sister taxa and represent only distantly related subclades within Stellaria, and therefore they require independent taxonomic recognition. Material from North America is closely related to Asian material and may fit under a broader concept of S. undulata. Relevant taxonomic changes and a lectotypification are made.