Floral evolution in Magnoliidae: an integrated approach

Stefan A. Little, Julien Massoni, Anna Maria Louise von Balthazar-Schönenberger, Laetitia Carrive, Thomas L. P. Couvreur, Jürg Schönenberger, Yannick Städler, Hervé Sauquet

Although flowers are considered key to the success and diversification of angiosperms, there remain large gaps in our knowledge of floral evolution across angiosperm diversity. Magnoliidae are remarkably diverse in floral structure. As a large monophyletic group (ca. 10,000 spp.) comprised of four orders and 20 families, Magnoliidae represent a microcosm of the broad changes in floral evolution seen across the angiosperms. The MAGNIPHY project aims to study floral evolution in Magnoliidae, integrating molecular phylogenetics, morphology, paleobotany, and developmental genetics. In order to test hypotheses of floral evolution at the scale of the group as a whole, we generated a densely sampled, dated phylogeny (199 species; 75% of genera; all families), calibrated with 10 carefully reviewed fossil age constraints. Floral morphology for each sequenced species was compiled from literature and our own morpho-anatomical observations. Floral trait evolution was reconstructed under parsimony, maximum likelihood, and Bayesian approaches. Preliminary results suggest that the ancestral flower of Magnoliidae was probably trimerous, with a whorled and differentiated perianth. In addition, floral transcriptomes of one species from each of the 20 families are being sequenced to correlate floral gene expression patterns with floral morphology. So far, preliminary transcriptomic data from six families reveal several MADS-box genes as well as TCP transcription factors with elevated expression. The MADS-box genes show high sequence similarity with genes of B, C, and E function, central in floral organ differentiation (i.e., AGAMOUS, APETALA3, PISTILLATA, SEPALLATA). The integrative approach of the MAGNIPHY project should help us unravel the history and mechanisms of floral diversification in Magnoliidae, an enigmatic part of angiosperm evolution.

Department für Botanik und Biodiversitätsforschung
Externe Organisation(en)
Université Paris XI - Paris-Sud, University of Connecticut, Institut de recherche pour le développement
ÖFOS 2012
106042 Systematische Botanik, 106008 Botanik, 106012 Evolutionsforschung
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