Developmental and Structural Section
Marazzi, Brigitte , Conti, Elena , Endress, Peter K. .
Phylogeny and evolution of asymmetric flowers in Senna (Leguminosae, Cassiinae).
Senna (Leguminosae, Cassiinae) is a large and diverse genus with buzz-pollinated flowers and many species further characterized by enantiostylous flowers. Different kinds of enantiostyly are observed in the genus, with asymmetry patterns affecting either the gynoecium only or also the androecium and the corolla. The existing classification divides the genus into six sections, from the most “primitive” sect. Psilorhegma, through sections Chamaefistula, Astroites, Senna, and Paradictyon, to the most “advanced” sect. Peiranisia, characterized by prominent floral asymmetry. In contrast with the existing classification, we observed enantiostylous flowers also in some species of sections Chamaefistula and Senna. Therefore, one of the major goals of the phylogenetic analyses presented here is to evaluate whether floral asymmetry evolved once or multiple times within Senna. We will present results of maximum parsimony analyses based on at least three plastid regions (rps16 and rpl16 introns, and matK exon) aimed at testing current sectional boundaries and reconstructing the evolution of enantiostyly in Senna. Morphological and ontogenetic analyses will focus on floral asymmetry in a group supported as monophyletic in the cpDNA phylogeny. Our current taxon and gene sampling supports the monotypic sect. Paradictyon as sister to sect. Senna, in agreement with flower and leaf morphology, while a strongly supported clade includes representatives of sections Chamaefistula and Psilorhegma. Several morphologically well-defined groups are strongly supported, e.g. the clade formed by the leafless species of ser. Aphyllae, sect. Peiranisia, which occurs in the dry regions of NW-Argentina, and that formed by the 2-foliolate treelet species of ser. Bacillares, sect. Chamaefistula, with showy enantiostylous flowers and one or both lower petals strongly concave.
1 - University of Zürich, Institute of Systematic Botany, Zollikerstrasse 107, Zurich, Zurich, CH-8008, Switzerland
2 - University of Zurich, Institute of Systematic Botany, Zurich, CH-8008, Switzerland
Presentation Type: Poster
Location: Special Event Center (Cliff Lodge)
Date: Tuesday, August 3rd, 2004
Time: 12:30 PM