SMITH, JAMES F.1*, DAVID A. BAUM2, and LENA HILEMAN3. 1Dept. of Biology, Boise State University, 1910 University Drive, Boise, ID, 83725, USA.; 2Dept. of Botany, University of Wisconsin-Madison, 430 Lincoln Drive, Madison, WI, 53706, USA.; 3Harvard University Herbaria, 22 Divinity Ave., Cambridge, MA, 02138, USA.. - Floral evolution and phylogenetic analysis of tribes Gloxinieae and Gesnerieae (subfamily Gesnerioideae: Gesneriaceae) with an emphasis on GCYC (a Gesneriaceae CYCLOIDEA homolog).
Although the majority of genera in Gesneriaceae have bilaterally
symmetric flowers, three genera in tribes Gloxinieae and Gesnerieae
differ in their floral symmetry. Bellonia has a radially
symmetric flower. Phinaea and Niphaea have subradially
symmetric corollas. Although both Phinaea and Niphaea
have only four functional stamens, typical for most of the family,
Bellonia has five. The gene CYCLOIDEA (CYC) has
been shown to be required for bilateral floral symmetry in
Antirrhinum and Linaria. The role of CYC in the
control of floral symmetry in other genera and its potential for
phylogenetic reconstruction have not been widely explored. Recent work
on subfamily Cyrtandroideae of Gesneriaceae has revealed a CYC
homolog named GCYC. We developed primers to GCYC and
used it to amplify homologs from a number of species of Gloxinieae and
Gesnerieae. Sequences are readily alignable and show less variability
than found in subfamily Cyrtandroideae. There is no evidence for frame
shift or stop codon mutations, implying that gene function is
maintained across all taxa regardless of floral symmetry. Parsimony
and maximum likelihood analysis of GCYC are strongly
incongruent with previous analyses of relationships among genera of
these tribes. To see if the problem is with GCYC or with
previous analyses sequences for a matched set of taxa were obtained
for two chloroplast regions, the trnL-trnF spacer and
trnL intron, and two nuclear markers, the nuclear ribosomal ITS
region and the glutamine synthetase gene (GS). Two copies of GS were
recovered for these tribes resulting in five genes analyzed in
conjunction with the previously published ndhF sequences. These
six genes are congruent with one another but not with GCYC. The
six gene phylogeny presumably reflects the evolutionary history of the
species and provides a robust framework for understanding the
evolution of floral form and GCYC sequence evolution.
Key words: CYCLOIDEA, floral symmetry, GCYC, Gesneriaceae, Gesnerioideae