title: Floral structure and development in the monoecious palm Gaussia attenuata (Arecaceae; Arecoideae).
abstract: OBJECTIVE
  Sexual dimorphism, at both the flower and plant level, is widespread in the palm family (Arecaceae), in contrast to the situation in angiosperms as a whole. The tribe Chamaedoreeae is of special interest for studies of the evolution of sexual expression since dioecy appears to have evolved independently twice in this group from a monoecious ancestor. In order to understand the underlying evolutionary pathways, it is important to obtain detailed information on flower structure and development in each of the main clades.
  
  
  METHODS
  Dissection and light and scanning electron microscopy were performed on developing flowers of Gaussia attenuata, a neotropical species belonging to one of the three monoecious genera of the tribe.
  
  
  RESULTS
  Like species of the other monoecious genera of the Chamaedoreeae (namely Hyophorbe and Synechanthus), G. attenuata produces a bisexual flower cluster known as an acervulus, consisting of a row of male flowers with a basal female flower. Whereas the sterile androecium of female flowers terminated its development at an early stage of floral ontogeny, the pistillode of male flowers was large in size but with no recognizable ovule, developing for a longer period of time. Conspicuous nectary differentiation in the pistillode suggested a possible role in pollinator attraction.
  
  
  CONCLUSIONS
  Gaussia attenuata displays a number of floral characters that are likely to be ancestral to the tribe, notably the acervulus flower cluster, which is conserved in the other monoecious genera and also (albeit in a unisexual male form) in the dioecious genera (Wendlandiella and a few species of Chamaedorea). Comparison with earlier data from other genera suggests that large nectariferous pistillodes and early arrest in staminode development might also be regarded as ancestral characters in this tribe.
authors.affiliation: UMR DIADE, Palm Developmental Biology Group, Centre IRD Montpellier, BP 64501, 911, avenue Agropolis, 34394 Montpellier Cedex 5, France.
authors.forename: Felipe
authors.initials: F
authors.lastname: Castaño
authors.affiliation: Conservatoire et Jardin Botaniques de la Ville de Genève, Université de Genève, laboratoire de systématique végétale et biodiversité, CP 60, CH-1292 Chambésy/GE, Switzerland.
authors.forename: Fred
authors.initials: F
authors.lastname: Stauffer
authors.affiliation: Departamento de Biología, Universidad Nacional de Colombia, sede Bogotá, Carrera 30 45-03, Edificio 421, Colombia.
authors.forename: Xavier
authors.initials: X
authors.lastname: Marquinez
authors.affiliation: Université de Genève, Faculté des Sciences, Département de Botanique et Biologie Végétale, quai Ernest Ansermet 30, 1211 Genève 4, Switzerland.
authors.forename: Michèle
authors.initials: M
authors.lastname: Crèvecoeur
authors.affiliation: UMR DIADE, Palm Developmental Biology Group, Centre IRD Montpellier, BP 64501, 911, avenue Agropolis, 34394 Montpellier Cedex 5, France.
authors.forename: Myriam
authors.initials: M
authors.lastname: Collin
authors.affiliation: Institut de Recherche pour le Développement (IRD), UMR DIADE/DYNADIV, BP 64501, 34394 Montpellier Cedex 5, France.
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Pintaud
authors.affiliation: UMR DIADE, Palm Developmental Biology Group, Centre IRD Montpellier, BP 64501, 911, avenue Agropolis, 34394 Montpellier Cedex 5, France james.tregear@ird.fr.
authors.forename: James
authors.initials: J
authors.lastname: Tregear
mesh_terms: D028023:Arecaceae / Q000033:anatomy & histology / Q000235:genetics / Q000254:growth & development*; D005075:Biological Evolution; D035264:Flowers / Q000033:anatomy & histology / Q000235:genetics / Q000254:growth & development*; D008855:Microscopy, Electron, Scanning; D056771:Ovule / Q000033:anatomy & histology / Q000235:genetics / Q000254:growth & development; D010802:Phylogeny; D012098:Reproduction; D013045:Species Specificity
keywords: Arecaceae; Arecoideae; Chamaedoreeae; Flower development; Gaussia attenuata; floral structure; monoecy; sexual expression