BORSCH1, THOMAS*, KHIDIR W. HILU2, VOLKER WILDE3, CHRISTOPH NEINHUIS1, AND WILHELM BARTHLOTT1. 1Botanisches Institut und Botanischer Garten, Friedrich-Wilhelms-Universität Bonn, Meckenheimer Allee 170, 53115 Bonn, Germany; 2Department of Biology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061; 3Forschungsinstitut Senckenberg, Paläobotanik, Senckenberganlage 25, 60325 Frankfurt a.M., Germany. - Phylogenetic analysis of noncoding chloroplast DNA sequences reveals Amborella as basalmost angiosperm.
A highly resolved phylogeny of basal angiosperms was inferred from
sequences of the trnT-L- and trnL-F-spacers and the trnL-intron. A
robust alignment was obtained, although it was complicated by the
recognition of a large number of indels, mostly simple direct repeats
ranging from 3-10 bp. About 30% of the aligned positions had to be
excluded from analysis because of too high variability. Conifers and
Ginkgo were used as outgroups. Gnetum shows such a high
sequence divergence that no part of the trnT-F-region could be aligned
with conifers, Ginkgo, or angiosperms. The ingroup comprises
35 taxa to represent all major lineages of basal angiosperms. In
parsimony analysis, Amborella appears as sister to all other
angiosperms examined. A Nymphaeales-clade (Nymphaeaceae plus
Cabombaceae) and an
Austrobaileya-Illicium-Schisandra-clade diverge
next. These results are in agreement with recent phylogenies based on
multiple coding regions. Bootstrap and decay support for the majority
of nodes in the trees of the trnT-trnF-analysis was found to be high,
and phylogenies obtained from separate versus combined analyses of the
two spacers and the intron were largely congruent. Patterns of
molecular evolution in the trnT-F-region are analyzed in order to
elucidate these unexpected findings.
Key words: Amborella, basal angiosperms, noncoding chloroplast DNA, phylogeny, trnT-trnF