title: Androecial evolution in Caryophyllales in light of a paraphyletic Molluginaceae.
abstract: OBJECTIVE
  Caryophyllales are highly diverse in the structure of the perianth and androecium and show a mode of floral development unique in eudicots, reflecting the continuous interplay of gynoecium and perianth and their influence on position, number, and identity of the androecial whorls. The floral development of five species from four genera of a paraphyletic Molluginaceae (Limeum, Hypertelis, Glinus, Corbichonia), representing three distinct evolutionary lineages, was investigated to interpret the evolution of the androecium across Caryophyllales. •
  
  
  METHODS
  Floral buds were dissected, critical-point dried and imaged with SEM. The genera studied are good representatives of the diversity of development of stamens and staminodial petaloids in Caryophyllales. •
  
  
  RESULTS
  Sepals show evidence of petaloid differentiation via marginal hyaline expansion. Corbichonia, Glinus, and Limeum also show perianth differentiation via sterilization of outer stamen tiers. In all four genera, stamens initiate with the carpels and develop centrifugally, but subsequently variation is significant. With the exception of Limeum, the upper whorl is complete and alternisepalous, while a second antesepalous whorl arises more or less sequentially, starting opposite the inner sepals. Loss or sterilization of antesepalous stamens occurs in Glinus and Limeum and is caused by altered carpel merism and inhibition by sepal pressures. •
  
  
  CONCLUSIONS
  Outer stamens of Hypertelis correspond with petaloids of Caryophyllaceae and suggest that staminodial petaloids and outer alternisepalous stamens are interchangeable in the Caryophyllales. We emphasize a switch in the position of first formed stamens from antesepalous to alternisepalous following the divergence of Limeum; thus stamen position is an important synapomorphy for the globular inclusion clade.
authors.affiliation: Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK.
authors.forename: Samuel
authors.initials: S
authors.lastname: Brockington
authors.forename: Patricia
authors.initials: P
authors.lastname: Dos Santos
authors.forename: Beverley
authors.initials: B
authors.lastname: Glover
authors.forename: Louis Ronse
authors.initials: LR
authors.lastname: De Craene
mesh_terms: D005075:Biological Evolution; D029748:Caryophyllaceae / Q000033:anatomy & histology* / Q000235:genetics / Q000254:growth & development; D035264:Flowers / Q000033:anatomy & histology* / Q000235:genetics / Q000254:growth & development; D008855:Microscopy, Electron, Scanning; D035704:Molluginaceae / Q000033:anatomy & histology / Q000235:genetics / Q000254:growth & development; D010802:Phylogeny
keywords: Caryophyllales; carpels; centrifugal stamens; floral development; globular inclusion clade; raphide clade; sepals; stamen loss; staminodial petaloids