Establishment of zygomorphy on an ontogenic spiral and evolution of perianth in the tribe Delphinieae (Ranunculaceae) |
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Authors: | Florian Jabbour Louis P Ronse De Craene Sophie Nadot and Catherine Damerval |
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Institution: | 1Université Paris-Sud, Laboratoire Ecologie, Systématique, Evolution, CNRS UMR 8079, AgroParisTech, Orsay, F-91405, France;2UMR de Génétique Végétale, INRA – Univ Paris-Sud – CNRS – AgroParisTech, Ferme du Moulon, 91190 Gif-sur-Yvette, France;3Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, UK |
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Abstract: | Background and AimsRanunculaceae presents both ancestral and derived floral traits for eudicots, and as such is of potential interest to understand key steps involved in the evolution of zygomorphy in eudicots. Zygomorphy evolved once in Ranunculaceae, in the speciose and derived tribe Delphinieae. This tribe consists of two genera (Aconitum and Delphinium s.l.) comprising more than one-quarter of the species of the family. In this paper, the establishment of zygomorphy during development was investigated to cast light on the origin and evolution of this morphological novelty.MethodsThe floral developmental sequence of six species of Ranunculaceae, three actinomorphic (Nigella damascena, Aquilegia alpina and Clematis recta) and three zygomorphic (Aconitum napellus, Delphinium staphisagria and D. grandiflorum), was compared. A developmental model was elaborated to break down the successive acquisitions of floral organ identities on the ontogenic spiral (all the species studied except Aquilegia have a spiral phyllotaxis), giving clues to understanding this complex morphogenesis from an evo-devo point of view. In addition, the evolution of symmetry in Ranunculaceae was examined in conjunction with other traits of flowers and with ecological factors.Key ResultsIn the species studied, zygomorphy is established after organogenesis is completed, and is late, compared with other zygomorphic eudicot species. Zygomorphy occurs in flowers characterized by a fixed merism and a partially reduced and transformed corolla.ConclusionsIt is suggested that shifts in expression of genes controlling the merism, as well as floral symmetry and organ identity, have played a critical role in the evolution of zygomorphy in Delphinieae, while the presence of pollinators able to exploit the peculiar morphology of the flower has been a key factor for the maintenance and diversification of this trait.Key words: Delphinieae, development, evolution, evo-devo, nectar spurs, ontogenic spiral, Ranunculaceae, zygomorphy |
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