Subtribe Solidagininae O. Hoffm. is a generally accepted name referring to a portion of the tribe Astereae, but concepts of its morphological circumscription and constituent genera have varied widely. Sequences from the internal transcribed spacer (ITS) of nuclear rDNA were examined in an attempt to define Solidagininae and to test hypotheses regarding major lineages within this group. Parsimony analyses indicate that a monophyletic group can be identified that largely corresponds with Solidagininae as previously delimited by Nesom (1994)-characterized by glandular-punctate leaves, a corymboid capitulescence, yellow rays, disc style branches with papillate collecting appendages, and terete, multinerved achenes with a 1-seriate pappus, although exceptions abound. The group itself is less strongly supported than each of three constituent lineages. A "Gutierrezia lineage" composed of genera producing small, turbinate achenes and basally indurate phyllaries occupies the basal position within the subtribe. An "Ericameria lineage"-an anomalous cluster of perennial shrubs (Ericameria) and annual herbs (Pentachaeta, Rigiopappus, Tracyina) is explicitly placed in the subtribe for the first time. The largest of the subgroups is the "Solidago lineage"-composed of a primarily herbaceous group (Solidago and close relatives) and a primarily woody one (Chrysothamnus and close relatives). The Solidago lineage exhibits low levels of sequence divergence within and between member genera, indicating a recent radiation, and the data are insufficient to draw conclusions regarding its internal phylogenetic structure. Solidagininae is almost an entirely North American group and apparently arose from near the very base of the "North American clade" of Astereae, although several of the genera have secondary radiations in South America.

Key words: Astereae, ITS, Solidagininae, Solidago