Systematics Section / ASPT
Ickert-Bond, Stefanie, M. , Wojciechowski, Martin F. .
A phylogeny of Ephedra (Gnetales) based on nuclear ribosomal DNA ITS and plastid rps4 sequences.
Comprehensive sampling of the genus Ephedra included 51 species representing its biogeographic and taxonomic diversity and several outgroup taxa. Sequences of the nuclear ribosomal internal transcribed spacer region 1 (nrDNA ITS1) and the plastid rps4 gene were obtained in order to help resolve phylogenetic relationships, examine character evolution, and historical biogeography in the genus. Within Ephedra the length of the nrDNA ITS1 varied from 1,081 to 1,143 basepairs (bp), in contrast to dramatically shorter lengths in the outgroups (Gnetum, Welwitschia, and Pinus). The rps4 locus varied in length from 645 to 661 bp in the same set of taxa. Both parsimony and maximum likelihood analyses of these sequences resulted in a well-resolved phylogeny that supports the monophyly of Ephedra, but not its traditional subdivision into the sections Ephedra, Asarca, and Alatae based on bract morphology. The resulting phylogeny also indicates a single origin of the New World taxa from within Old World lineages. Among the Old World species three highly-supported monophyletic groups are recognized that are highly concordant with morphological evidence. The New World clade includes two main subclades of North and South American species that are strongly supported, while the position of two, mostly Mexican species E. pedunculata and E. compacta remains unresolved. Character reconstruction of ovulate strobilus types in Ephedra indicates that fleshy bracts are ancestral and shifts to dry, winged bracts have occurred multiple times. Low levels of sequence divergence within the core North American clade suggest either recent and rapid ecological radiation or highly conservative ribosomal DNA evolution within the clade. A lack of synapomorphies in this clade as compared to Old World lineages is equally intriguing.
1 - Arizona State University, School of Life Sciences, PO Box 874501, Tempe, Arizona, 85287-4501, USA
2 - Field Museum, Botany Department, 1400 S. Lake Shore Dr., Chicago, Illinois, 60605-2496, USA
low levels of sequence divergence.
Presentation Type: Paper
Location: Cottonwood C (Snowbird Center)
Date: Wednesday, August 4th, 2004
Time: 11:15 AM