Phylogenetic Relationships Among Native and Naturalized Hieracium (Asteraceae) in Canada and the United States Based on Plastid DNA Sequences

We used parsimony and maximum likelihood analyses of chloroplast DNA to examine the relationships of native North American Hieracium (hawkweeds; Asteraceae) with non-native Hieracium species being studied for classical biological control. Thirty-six taxa were included; these representing the three morphologically-based subgenera: Pilosella from Eurasia, the circumboreal Hieracium, and Chionoracium from North and South America. Results from the trnT-F and petN-psbM sequence data strongly support the morphologically based classifications. An exception is the placement of H. canadense within subgenus Chionoracium, rather than subgenus Hieracium, which may be due to chloroplast capture. Placement of the genus Andryala within Hieracium subgenus Pilosella is also supported. Additionally, species in subgenus Pilosella targeted for classical biological control are still supported as being in a separate subgenus from native North American taxa.