Systematics Section / ASPT
Cordes, Jenny M. , Downie, Stephen R. .
Ascertaining the phylogenetic position and infrageneric relationships of Conium (Apiaceae), the odd man out.
The genus Conium (poison hemlock), one of the most toxic members of the plant kingdom, has had a varied and complex taxonomic history. It has been described as “the odd man out” in the family because it is one of only a few umbellifers that produces alkaloids. It also lacks well-developed vittae in its mature fruits. As such, the genus has been variously treated in traditional taxonomic studies. Moreover, the relationships among its constituent species, especially between the widespread weed C. maculatum and its southern African congeners, are obscure. Molecular systematic studies to date have revealed that C. maculatum comprises an isolated lineage within the apioid superclade, a large and variable group of umbellifers containing tribes and other major clades of uncertain relationship. To ascertain the phylogenetic placement of the genus within the apioid superclade and to assess infrageneric relationships, we are analyzing nrDNA ITS and cpDNA sequences. Preliminary results using ITS sequences indicate a sister group relationship between Conium and an expanded tribe Tordylieae, an intriguing find since some of these plants share a similar phytochemistry and insect associates. Further sampling of tribe Tordylieae and its allies is in progress. The three species of Conium endemic to southern Africa (C. chaerophylloides, C. fontanum, and C. sphaerocarpum) constitute a monophyletic group (with the first two species allying as sister taxa), but the relationship between this clade and a wide geographic sampling of C. maculatum is unresolved. It has been suggested that these southern African plants are simple forms of the widespread and highly variable C. maculatum. Additional data are forthcoming that will test this hypothesis.
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1 - University of Illinois Urbana, Department of Plant Biology, 265 Morrill Hall, 505 South Goodwin Avenue, Urbana, Illinois, 61801-3707, USA
nrDNA ITS sequences.
Presentation Type: Poster:Posters for Sections
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM