Evolution of Floral Form


I am interested to study the floral structural groundplans that characterize major angiosperm clades, namely by documenting their distribution in the angiosperm phylogeny, and determining the homologies of individual structural floral elements. In particular, I am interested in the evolution of a groundplan that represents the structural basis of floral diversity among the core eudicots. Its most distinctive elements are a bipartite perianth composed of well-differentiated calyx and corolla, and a compound meristic plan with pentamerous (or tetramerous) perianth and androecium, and dimerous (or trimerous) gynoecium. This floral groundplan is represented in all core eudicot lineages except in Gunnerales, the earliest-diverging branch within the clade. Eudicot lineages outside the core eudicots exhibit a variety of floral structural plans among which a dimerous, opposite decussate organization is frequent. The flowers of one of these early eudicot lineages, Sabiaceae, have a bipartite perianth and a compound pentamerous-dimerous merosity. The distribution of elements of the core eudicot floral groundplan outside and within core eudicots rise questions about its evolution: Did the core eudicot floral groundplan evolve once or several times, within or outside the core eudicots? Are the elements in Sabiaceae homologous to those in the core eudicots? Are the flowers of Gunnerales originally simple, or do they represent an instance of loss of the core eudicot groundplan? Did the elements of the core eudicot groundplan evolve simultaneously or sequentially?


The research that I have conducted on this topic consists of a documentation of the morphological and structural characteristics of flowers of the non-Ranunculid early diverging eudicot lineages, including their living and several fossil representatives. Information about floral form and structure was optimized onto a phylogenetic hypothesis derived from molecular data, to determine the variability in floral structure among early diverging eudicot lineages, and the structural attributes of flowers belonging to successive sister taxa to the core eudicots. I am currently investigating the morphology, anatomy and ontogeny of flowers of Meliosma (Sabiaceae) and Gunnera (Gunneraceae, Gunnerales), to obtain information that may allow to document the homology of the structural elements of Meliosma with those of the core eudicots, and to determine if the flowers of Gunnera are originally simple, or reduced from a more complex groundplan.

I intend to continue the research on the evolution of the core eudicot floral groundplan, and also to investigate from morphological, anatomical and ontogenetic standpoints the establishment of floral morphological or structural elements in different clades across angiosperms.

Main Dra. Magallón / Up