Abstract Detail

Systematics Section / ASPT

Timme, Ruth [1], Linder, Randal [1], Simpson, Beryl [1].

Better resolution in Helianthus (Asteraceae) using the rDNA external transcribed spacer (ETS).

Despite the agronomic and research importance of Helianthus (Asteraceae), its phylogeny is still largely unresolved. Non-resolution has not been for lack of effort, as many botanists have attempted to resolve the relationships in Helianthus with both morphological and molecular data. The rDNA external transcribed spacer of (ETS), which is a more rapidly evolving marker than others have tried before, has provided us much better resolution within the sunflowers.
Our results show that Helianthus section Helianthus (or the annual sunflowers) is well resolved and monophyletic. Helianthus annuus and H. petiolaris (the subjects of Rieseberg's hybridization studies) are distantly related within this section. Interestingly, the placements of their hybrid offspring, H. deserticola and H. anomolus, have weak support in this clade. The large Helianthus section Divaricati is paraphyletic with two other smaller sections (H. section Agrestis and part of H. section Ciliares) nesting within it. The polyphyly of H. section Ciliares is consistent with previous studies indicating that the species in this series do not share a common ancestor. The fourth and smallest recognized section, H. section Agrestis, is nested in a small clade that is sister to the rest of the sunflowers. Included in this clade are H. heterophyllus, H. carnosus, and H. porteri. This finding is also consistent with previous studies, although the relationships are better supported in this ETS phylogeny.

1 - University of Texas at Austin, Section of Integrative Biology, 1 Universiy Station, #A6700, Austin, Texas, 78712, USA

Keywords:
Asteraceae
hybridization
molecular systematics
nrDNAETS
polyploidy
sunflower
Helianthus.

Presentation Type: Poster
Session: 32-120
Location: Special Event Center (Cliff Lodge)
Date: Tuesday, August 3rd, 2004
Time: 12:30 PM
Abstract ID:362