ROBERTS, ROLAND P.* and LOWELL E. URBATSCH. Biological Sciences Department, Louisiana State University, Baton Rouge, Louisiana 70803. - Phylogenetic investigations of the Ericameria/Chrysothamnus complex (Astereae, Asteraceae) based on nuclear ribosomal ITS and ETS sequence data.
Systematic and evolutionary studies of Ericameria based largely
on morphological and cytological data have resulted in numerous,
dramatically different, concepts of relationship. Ericameria
has been treated as a section of Haplopappus and as a distinct
genus. At various times, species in the genus Chrysothamnus
have been transferred to Ericameria. Additional proposals
suggest that all species of Chrysothamnus, and species
previously residing in Haplopappus sections Asiris,
Macronema, and Stenotopsis be treated as
Ericameria. Furthermore, the genus Xylothamnia was
established to accommodate certain species that were once part of
Ericameria. Inferred relationships based on sequence data of
the internal transcribed spacer (ITS) and external transcribed spacer
(ETS) regions of nuclear ribosomal DNA are not entirely in keeping
with existing assumptions but provide the basis for additional
phylogenetic hypotheses. Species of Chrysothamnus sensu
Nesom form a clade that includes Solidago, Sericocarpus,
and certain species of Tonestus. Ericameria sensu
Nesom forms a clade distinct from that containing Chrysothamnus
and is sister to Tracyina, Ragiopappus, and
Pentachaeta. Xylothamia, as defined by Nesom, appears to
represent at least two different lineages and probably is
paraphyletic. Ericameria's subtribal affiliation with
Hinterhuberinae is not supported by sequence data.
Key words: Asteraceae, Astereae, Chrysothamnus, Ericameria