Developmental and Structural Section
Matthews, Merran L. , Endress, Peter K. .
Malpighiales: comparative floral structure of Chrysobalanaceae s.l. and other supported clades.
AS the largest angiosperm order (with respect to number of families), Malpighiales (rosids) represent a diverse, and for many families, structurally largely unknown component of the flowering plants. The phylogenetic topology of the 38 families is still mainly unresolved, although a few suprafamilial clades appear to be potentially well supported. Among these are (1) Balanopaceae+Chrysobalanaceae s. l. (Chrysobalanaceae+Euphroniaceae, Dichapetalaceae+Trigoniaceae), (2) Ochnaceae s.l. (Ochnaceae+Medusagynaceae, Quiinaceae), (3) Achariaceae, Goupiaceae, Violaceae, Lacistemaceae+Salicaceae, Passifloraceae s.l. (Malesherbiaceae, Passifloraceae+Turneraceae) and (4) Clusiaceae, Bonnetiaceae, Hypericaceae+Podostemaceae (only clades with > two families mentioned). As part of a larger project on the comparative floral structure of Malpighiales, we have begun to make fresh structural studies and to determine shared structural patterns within such suprafamilial clades. An initial survey of Chrysobalanaceae s.l. suggests that features of the androecium especially support this clade, including stamens united into a strap-like structure on one side of the flower and/or an androecial tube of stamens (and nectary lobes) in monosymmetric flowers, with staggered heights of paired stamens, extremely introrse anthers with a dorsally extensive connective and a continuous endothecium over the dorsal side. Ovary locules filled with hairs are shared by Chrysobalanaceae and Trigoniaceae. The sister pair Dichapetalaceae and Trigoniaceae share a completely synascidiate ovary and lower style, and pollen tube transmitting tissue that is restricted to the innermost part of the ventral slit (instead of lining the entire slit). Other features common in Chrysobalanaceae s.l. but present elsewhere in the order (and within rosids) are quincuncial sepals congenitally united, trimerous gynoecium, entirely united carpels, two pendant epitropous collateral ovules with an obturator, and special mucilage cells in sepals. Clades (1) (but Euphroniaceae unknown) and (4) share incompletely tenuinucellar ovules with an endothelium, a feature unusual in rosids and +/- restricted to some Malpighiales and Celastrales.
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1 - Universität Zürich, Institut für Systematische Botanik, Zollikerstrasse 107, Zürich, CH-8008, Schweiz
comparative floral morphology
Presentation Type: Oral Paper:Papers for Sections
Location: 303/Bell Memorial Union
Date: Wednesday, August 2nd, 2006
Time: 11:30 AM