Floral Morphogenesis and Molecular Systematics of the Family Violaceae
The Violet family (Violaceae) is a medium-sized family of herbs, shrubs, lianas, treelets and trees in 22 genera and up to 930 species. The family is distributed worldwide but most genera are tropical and confined to single continents except for the three largest, Viola , Rinorea and Hybanthus . The family is diverse in growth form and vegetative morphology, floral structure, fruit and seed morphology, but few studies have comprehensively examined this diversity. Traditional higher-level groups and intergeneric relationships have remained unscrutinized until now. The present investigations had three objectives: (1) a comprehensive molecular phylogenetic framework for the Violaceae; (2) documentation of floral ontogeny in representative genera of the family; and (3) inference of evolutionary trends in floral developmental and other key characters within a molecular phylogenetic context. Seventy-one trn L-F intergenic spacer chloroplast sequences were produced for most genera and numerous species in the family. Some sequences of the rbc L gene were also produced and analyzed with a previously available data set with single-species exemplars of most genera. The data sets were analyzed independently and as combined data matrix. Mutually corroborative results rejected most concepts of intergeneric relationships and nearly all intrafamilial taxonomic categories previously recognized in the family, based on a simplistic actinomorphic- vs. zygomorphic-flowered subdivision. The genera Rinorea and Hybanthus were polyphyletic, the latter represented by seven disparate clades. An "Anchietioid alliance" was supported, consisting of several genera with dramatically divergent growth forms, vegetative morphology, floral architecture and fruit diversity. Three fascinating biogeographic disjunctions were highlighted: a Latin American-South Pacific disjunction involving Anchietea , Corynostylis and Agatea ; a Mesoamerican-Hawaiian disjunction between some members of Hybanthus and Isodendrion ; and an Amazonian-west African disjunction between Rinoreocarpus and Allexis . Complete floral developmental stages were examined using Scanning Electronic Microscopy in eight genera that embraced strictly actinomorphic, transitional and strongly zygomorphic forms: Agatea , Amphirrhox , Anchietea , Corynostylis , Gloeospermum , Hekkingia , Leonia and Paypayrola . Critical events in floral organ initiation and development were elucidated. Transformational series were developed for several key floral ontogenetic and other morphological traits. States were scored for genera and mapped onto the rbc L/ trn L-F phylogeny to infer trends in character evolution.
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:violaceae floral ontogeny molecular systematics phylogeny evolution
Date of Publication:01/01/2005