Submitted to: Systematic Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/12/2006
Publication Date: 4/1/2007
Citation: Gaskin, J.F., Wilson, L.M. 2007. Phylogenetic relationships among native and naturalized hieracium (asteraceae) in Canada and the United States based on plastid DNA sequences. Systematic Botany. 32(2):478-485. Interpretive Summary: The invasive plants called hawkweeds are being proposed as a target of classical biological control. There are also native hawkweed (genus Hieracium) species in North America. Plant species that are closely related to targets of biological control must be tested for host-specificity. The relationships of native and invasive hawkweeds are known only from morphology, so we tested relationships using molecular methods (DNA sequencing). We found that the groupings of hawkweeds based on morphology were supported with only a few exceptions. This information will be used by biological control researchers.
Technical Abstract: 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, infrageneric classifications: subgenus Pilosella from Eurasia, the circumboreal subgenus Hieracium, and subgenus Chionoracium from North and South America. Results from the trnT-F and petN-psbM sequence data strongly support the morphologically based classifications. Exceptions include 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.