Systematics Section / ASPT
Andreasen, Katarina , Baldwin, Bruce G. .
Evolutionary and historical biogeographic perspectives on the genus Arnica (Asteraceae-Madiea): nuclear ribosomal DNA evidence.
Recent discovery of a sister-group relationship between the long-misplaced genus Arnica (ca. 30 species) and the mostly Californian subtribe Madiinae (the tarweeds) has allowed investigation of character evolution, historical biogeography, and relationships within Arnica. Maguire's hypothesis that the circumboreal and temperate montane genus originated in arctic or subarctic western North America, migrated eastward and westward in the arctic/subarctic and southward are in conflict with phylogenetic data from 18S-26S nuclear ribosomal transcribed spacer (ITS and ETS) sequences. Proposed subgenera and sections within Arnica are in most cases not supported as monophyletic. Molecular cloning revealed non-monophyletic ITS/ETS-sequences within some taxa; hybridization is a plausible explanation for such sequence polymorphism in Arnica, wherein polyploidy is common and has been associated with apomixis. Rapid morphological evolution in characters otherwise uniform across the genus has evidently occurred in the lineage represented by A. [Whitneya] dealbata, which was nested within A. nevadensis and differs from all other members of Arnica by having functionally staminate, rather than bisexual, disc florets and epappose, rather than pappose, cypselae.
1 - University of California, Berkeley, Integrative Biology, University and Jepson Herbaria, 1001 Valley Life Sciences Building, Berkeley, California, 94720-2465, USA
2 - Uppsala University, Systematic Botany, Department of Evolution, Genomics and Systematics, Norbyvägen 18D, Uppsala, SE-752 36, Sweden
nuclear ribosomal DNA
Presentation Type: Paper
Location: Cottonwood B (Snowbird Center)
Date: Monday, August 2nd, 2004
Time: 10:45 AM