Dissertation Research: Patterning of Morphological Diversification: Evolution of Floral Form in Tribe Amorpheae (Fabaceae)

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9902206Hufford and McMahon Understanding patterns of morphological diversity among groups of organismsis a key aspect of systematics. Among the 12,000 species of the legume subfamily Papilionoideae, pea-like flowers are highly conserved; but in the New World tribe Amorpheae (including "prairie clovers" of the genus Dalea) flower forms are highly modified, and often not pea-like in shape or development. To understand the historical origins of this floral diversity in Amorpheae, graduate student Michelle McMahon, under the direction of adviser Dr. Larry Hufford at Washington State University, will be analyzing the historical relationships (the genealogy or phylogeny of representative taxa) among species in the tribe with emphasis on DNA sequencing of the chloroplast matK gene as main source of evidence. In addition, a thorough morphometric study will be made of floral forms to assess accurately structural similarities in petals and stamens and to establish the full range and distribution of variation among taxa. Two approaches will be taken to synthesize phylogeny and diversity of floral form. First, developmental data for structurally similar (homologous) flower parts, analyzed in the context of the molecular-phylogenetic framework, can provide insights about the evolutionary transformations involved in the origin of disparate adult forms. Second, detailed measurement data of key floral organs mapped onto a phylogeny can be compared with null models of evolutionary change in floral characters, in order to determine unique as well as recurring patterns of character combinations or trends. A synthesis of phylogenetic and developmental data should help to explain patterns of floral form in Amorpheae, patterns that may be due to correlations between adult and early-stage characters, to accelerated rates of evolution, or to evolution through new combinations of recurring features. The proposed work will provide techniques for the thorough analysis of floral form evolution and an understanding of how patterning of diversity among lineages has occurred in Amorpheae.