Intra-individual variation of flowers in Gunnera subgenus Panke (Gunneraceae) and proposed apomorphies for Gunnerales

A study of inflorescence and flower development in 12 species from four of the six subgenera of Gunnera (Gunneraceae) was carried out. In the species of subgenus Panke, initiation of floral apices along the partial inflorescences is acropetal but ends up in the late formation of a terminal flower, forming a cyme at maturity. The terminal flower is the largest and the most complete in terms of merosity and number of whorls and thus it is the most diagnostic in terms of species-level taxonomy. The lateral flowers undergo a basipetal gradient of organ reduction along the inflorescence, ranging from bisexual flowers (towards the distal region) to functionally (i.e. with staminodia) and structurally female flowers (towards the proximal region). Our results show that the terminal structure in Gunnera is a flower rather than a pseudanthium. The terminal flower is disymmetric, dimerous and bisexual, representing the common bauplan for Gunnera flowers. It has a differentiated perianth with two sepals and two alternate petals, the latter opposite the stamens and carpels. Comparisons with other members of the core eudicots with labile floral construction are addressed. We propose vegetative and floral putative synapomorphies for the sister-group relationship between Gunneraceae and Myrothamnaceae. (C) 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 160, 262-283.

Floral morphology and development in quillajaceae and surianaceae (Fabales), the species-poor relatives of leguminosae and polygalaceae

Background and Aims: Molecular phylogenies have suggested a new circumscription for Fabales to include Leguminosae, Quillajaceae, Surianaceae and Polygalaceae. However, recent attempts to reconstruct the interfamilial relationships of the order have resulted in several alternative hypotheses, including a sister relationship between Quillajaceae and Surianaceae, the two species-poor families of Fabales. Here, floral morphology and ontogeny of these two families are investigated to explore evidence of a potential relationship between them. Floral traits are discussed with respect to early radiation in the order. Methods: Floral buds of representatives of Quillajaceae and Surianaceae were dissected and observed using light microscopy and scanning electron microscopy. Key Results Quillajaceae and Surianaceae possess some common traits, such as inflorescence morphology and perianth initiation, but development and organization of their reproductive whorls differ. In Quillaja, initiation of the diplostemonous androecium is unidirectional, overlapping with the petal primordia. In contrast, Suriana is obdiplostemonous, and floral organ initiation is simultaneous. Independent initiation of five carpels is common to both Quillaja and Suriana, but subsequent development differs; the antesepalous carpels of Quillaja become fused proximally and exhibit two rows of ovules, and in Suriana the gynoecium is apocarpous, gynobasic, with antepetalous biovulate carpels. Conclusions: Differences in the reproductive development and organization of Quillajaceae and Surianaceae cast doubt on their potential sister relationship. Instead, Quillaja resembles Leguminosae in some floral traits, a hypothesis not suggested by molecular-based phylogenies. Despite implicit associations of zygomorphy with species-rich clades and actinomorphy with species-poor families in Fabales, this correlation sometimes fails due to high variation in floral symmetry. Studies considering specific derived clades and reproductive biology could address more precise hypotheses of key innovation and differential diversification in the order.

Floral ontogeny in Polygalaceae and its bearing on the homologies of keeled flowers in Fabales

Keeled flowers are characteristic of many species of Polygalaceae (tribe Polygaleae), in which there is often a distinctive crest located at the abaxial petal. This study of floral ontogeny across the entire family highlights potential suites of characters that relate to the evolution of keeled and crested flowers. One character suite encompasses interconnected transformations of the lateral perianth organs acting as an evolutionary module: bracteoles, lateral sepals (with delayed initiation and petaloid appearance), and lateral petals (suppressed or lost). The plastochron between initiation of the lateral sepals and that of the other sepals is relatively long in the tribe Polygaleae, in which the calyx is usually heteromorphic. By contrast, in the petal whorl, the difference between a zygomorphic and an actinomorphic corolla involves organ suppression rather than heterochrony. Four primary androecial patterns are identified in the family, and the gynoecium ranges between syncarpous‐bicarpellate and multicarpellate. Stigma diversity is based on two primary morphological types: one in which the papillate stigmatic surfaces lie close together, the other in which they are physically separated. The floral ontogeny of Polygalaceae is considered alongside comparative data available for other members of the order Fabales, and hypotheses to account for the similarities and differences between keeled flowers are discussed.