Origins of flower morphology
Version of Record online: 23 JUL 2001
Copyright © 2001 Wiley-Liss, Inc.
Journal of Experimental Zoology
Volume 291, Issue 2, pages 105–115, 15 August 2001
How to Cite
Endress, P. K. (2001), Origins of flower morphology. J. Exp. Zool., 291: 105–115. doi: 10.1002/jez.1063
- Issue online: 26 DEC 2002
- Version of Record online: 23 JUL 2001
- Manuscript Accepted: 6 NOV 2000
- Manuscript Received: 18 MAY 2000
- Swiss National Foundation. Grant Number: 3100-040327.94
Flowers evolved in many steps, probably starting long before flowering plants (angiophytes) originated. Certain parts of flowers are conservative and have not changed much during evolution; others are evolutionarily highly plastic. Here conservative features are discussed and an attempt is made to trace them back through their evolutionary history. Microsporangia and ovules (which develop into seeds) are preangiophyte floral elements. Angiospermy, combined with postgenital fusion, was the most prominent key innovation in angiophytes. Angiospermy and thecal organization of stamens originated earlier than all clades of extant angiosperms (the crown group of angiophytes). Differentiation of a perianth into calyx and corolla and syncarpy appeared after the first branching of the basalmost clades of extant angiosperms. Sympetaly and floral tubes as well as tenuinucellar, unitegmic ovules originated as major innovations in the clade that led to asterids. An obvious trend in flower evolution is increased synorganisation of parts, which led to new structures. Fixation of floral organ number and position was a precondition for synorganization. Concomitantly, plasticity changed from number and position of organs to shape of the new structures. Character distribution mapped onto cladograms indicates that key innovations do not appear suddenly, but start with trials and only later become deeply rooted genetically in the organization. This is implied from the common occurrence of reversals in the early history of an innovation. J. Exp. Zool. (Mol. Dev. Evol.) 291:105–115, 2001. © 2001 Wiley-Liss, Inc.