Using cpDNA to Assess Species Delimitation between Liatris helleri Porter (Asteraceae) and Liatris turgida Gaiser

Liatris helleri is a federally-threatened perennial species endemic to nine populations in Western North Carolina. Evidence suggests that L. helleri is morphologically indistinguishable from L. turgida, and thus should be subsumed into a single species. However, conservation agencies often test several species concepts before altering species delimitations. This has been the case with L. helleri, as ecological differences between L. helleri and L. turgida have raised questions about the validity of classifying L. helleri using morphology alone. We amplified regions of chloroplast DNA in order to test the Phylogenetic Species Concept. We hypothesized that L. helleri and L. turgida are distinct species, and thus should form two distinct monophyletic groups. Phylogenetic analyses recovered two clades, neither of which was monophyletic for L. helleri or L. turgida. TCS analysis revealed a central set of L. helleri populations which gave rise to three independent radiations of L. turgida. Our results do not support recognition of L. helleri and L. turgida as distinct species, and suggest that L. helleri and L. turgida are in some phase of a speciation event. We recommend continued protection of L. helleri pending further evidence of speciation, and that conservation efforts focus on this central cluster of populations.