Osmophore structure and phylogeny of Cirrhaea (Orchidaceae, Stanhopeinae)

Abstract

Phylogenetic relationships and osmophore evolution of six Cirrhaea spp. were studied. Floral morphology was analysed using fresh flowers, and osmophore anatomy was determined on the basis of fixed flowers. Phylogenetic relationships of Cirrhaea were inferred on the basis of internal transcribed spacer (ITS), matK and trnL-F regions using maximum parsimony and Bayesian analyses. Floral morphology and osmophore structure vary among species. All Cirrhaea osmophores have a secretory epidermis without papillae. Cirrhaea is monophyletic and includes three subclades: (1) C. dependens/C. nasuta, with a secretory cylindrical protuberance at the base of the labellar midlobe; (2) C. fuscolutea/C. longiracemosa, with a secretory tissue at the base of the shell-shaped midlobe; and (3) C. loddigesii/C. seidelii with secretory tissue on the inner surface of the lateral lobes. The features of the flowers and osmophores in Cirrhaea spp. extend our knowledge of the diversity of secretory structures in Stanhopeinae, and demonstrate that floral morphology reflects phylogenetic relationships in Cirrhaea