KELCH, DEAN G.* AND RAYMOND CRANFILL. University and Jepson Herbaria, University of California, Berkeley, CA 94720. - Seed plant phylogeny: the yew-conifers and a farewell to the anthophyte hypothesis.
Recent discussions of relationships within seed plants have focussed
on the correct placement of the Gnetales. Some phylogenetic
conclusions based on DNA sequence data have placed this group as
sister to conifers or even within the conifers. Contrary to this,
phylogenetic analysis of sequence data from the chloroplast gene rps4
places Gnetales as sister to all other living seed plants. Bootstrap
support for this result is increased by adding rbcL and 18S rDNA
sequence data to the analysis. Angiosperms comprise a branch located
between Gnetales and other living seed plants. The paraphyly of living
anthophytes (Gnetales and angiosperms) contradicts the anthophyte
theory, but also modifies significantly the interpretation of
character evolution deduced from trees presenting Gnetales as
coniferophytes. Within conifers, there is robust support for Pinaceae
as sister to other conifers, followed by an Araucariaceae/
Podocarpaceae clade. The crown group includes Cupressaceae s.l.,
Cephalotaxus, Sciadopitys, Taxaceae, and Torreyaceae.
This group of “yew-conifers” is also found in trees based on rbcL and
18S rDNA. The rps4 gene proves useful at the level of seed plant
family relationships, but also includes more variable regions that
have utility between genera.
Key words: conifer, Gnetales, phylogeny, rps4, seed plant