title: Floral cost vs. floral display: Insights from the megadiverse Myrtales suggest that energetically expensive floral parts are less phylogenetically constrained.
abstract: OBJECTIVE
  Floral display describes the effect of flower size combined with the number of flowers per inflorescence. There is strong evidence that a floral-display trade-off operates under energetic constraint, with few-flowered inflorescences likely to have larger flowers than many-flowered inflorescences. Flower size can be estimated by different variables; thus, we propose that the variable for flower size that is most highly (negatively) correlated with the number of flowers per inflorescence will also be the best estimate of floral cost. Ranking the correlation with the phylogenetic signal of the variable can provide additional insight into the evolution of floral display.
  
  
  METHODS
  The Myrtales were chosen as a model order based on age, worldwide distribution, and diversity of reproductive strategies. Ninety-nine species representing all families and one quarter of generic diversity across its geographic and ecological range were sampled to reconstruct a phylogeny based on rbcL and ndhF sequences. Correlation coefficients were calculated for flower size variables vs. the number of flowers per inflorescence. Phylogenetic signal was measured for all variables and for floral display.
  
  
  RESULTS
  Flowers per inflorescence showed significant negative correlation with the following flower size variables (weakest to strongest): filament length < anther size < flower depth < flower diameter. As the correlation of each character with number of flowers per inflorescence rose (suggesting increased cost), the values for phylogenetic signal diminished (suggesting less constraint).
  
  
  CONCLUSIONS
  We conclude that energetically costly floral characters appear to be less phylogenetically constrained, while low-cost floral characters maintain higher levels of phylogenetic inertia.
authors.affiliation: Departamento de Botânica, Instituto de Ciências Biológicas, Universidade de Brasília, Brasília, Distrito Federal, Brazil CEP 70919-970 Research Department of Genetics, Evolution and Environment, University College London, Gower Street, London, WC1E 6BT UK The Herbarium, Royal Botanic Gardens, Kew, Richmond, Surrey, Post code: TW9 3AE, UK.
authors.forename: Thaís N C
authors.initials: TN
authors.lastname: Vasconcelos
authors.affiliation: Departamento de Botânica, Instituto de Ciências Biológicas, Universidade de Brasília, Brasília, Distrito Federal, Brazil CEP 70919-970.
authors.forename: Carolyn E B
authors.initials: CE
authors.lastname: Proença
mesh_terms: D044822:Biodiversity; D018533:Biomass; D004734:Energy Metabolism; D035264:Flowers / Q000033:anatomy & histology*; D056626:Inflorescence; D016014:Linear Models; D027822:Myrtaceae / Q000033:anatomy & histology*; D010802:Phylogeny
keywords: Myrtales; evolution; floral display; flower diameter; phylogenetic signal; trade-off