Is the serpentine aster, Symphyotrichum depauperatum (Fern.) Nesom, a valid species and actually endemic to eastern serpentine barrens?

Serpentine aster, Symphyotrichum depauperatum (Fern.) Nesom, is the ‘flagship’ species of the eastern serpentine barrens, inhabiting 20 of the 26 remaining occurrences of significant size of this globally rare community type and long recognized as its only known endemic species. Previous studies have called into question both the validity of the taxon and its status as a true endemic of the serpentine barrens. We used amplified fragment length polymorphism (AFLP) analysis to compare seven serpentine barrens populations, one alleged diabase glade population, and two populations each of the two species with which S. depauperatum is lumped by some authors. Our analysis supports the validity of S. depauperatum as a distinct species, which grows almost entirely on shallow soils overlying serpentinite bedrock in Pennsylvania and Maryland, but it confirms an earlier hypothesis that S. depauperatum also includes small, disjunct populations on diabase glades in North Carolina.