GRAHAM, SEAN W*, HARDEEP RAI, PATRICK REEVES, HEATH O'BRIEN, AND RICHARD OLMSTEAD. Dept. of Biological Sciences, University of Alberta, Edmonton AB, Canada T6G 2E9; Dept. of Botany, University of Washington, Seattle WA 98195. - Inference of seed plant phylogeny from multiple chloroplast genes.
The reconstruction of seed plant relationships is recognized as one of
the most difficult problems in plant systematics. A range of studies
using various lines of evidence from morphology and molecules have
given different and often strongly conflicting results. It is not
clear, for example, whether the Gnetales represent the extant sister
group of the flowering plants (the "anthophyte hypothesis").
Recent molecular studies suggest that they are instead closely
related to (or even nested within) the conifers. The root of the seed
plants, and the issue of gymnosperm monophyly, are likewise unclear.
Long-branch attraction appears to be a major problem in seed plant
phylogenetic inference, and may be partly responsible for the strongly
discordant results from different studies. We have sampled large
amounts of DNA sequence data from a variety of slowly evolving
chloroplast genes, across taxa that span the major lineages of the
seed plants, in order to try to explore these issues. The impact of
long-branch attraction and of different levels of gene and taxon
sampling on seed plant phylogenetic inference will be addressed.
Key words: angiosperms, chloroplast genes, Gnetales, long-branch attraction, phylogenetics, Seed plants