Mark Fishbein (Postdoc; PhD, University of Arizona): Mark is collaborating with Doug Soltis and Larry Hufford on an investigation of gynoecial evolution in the Saxifragales. We seek to explain both from a phylogenetic and developmental perspective the diverse ovary positions that are found in this clade. Ovary positions range from superior (e.g., in Cercidiphyllum and Tetracarpaea) to inferior (e.g., Saxifragaceae s.s.). Our research to date has shown that most members of the clade are epigynous, although they have a wide range of ovary positions. This range is due to differences in the rate of elongation in that part of the ovary below the insertion of the perianth and androecium relative to that part above their insertion among the taxa. Truly superior ovaries occur in Cercidiphyllum in association with the loss of a perianth and the origin of unisexuality and in Tetracarpaea in association with the origin of an elongate floral receptacle (which is reminiscent of that found among many magnoliids or some ranunculids). This research is emphasizing a diverse range of DNA regions, including the chloroplast genes matK, atpB, and rbcL and nuclear genes 18S and 26S, for phylogeny reconstruction. In addition to his work on the Saxifragales project, Mark also continues to pursue research on Asclepias, which was the topic of his dissertation at the University of Arizona.

Shelley McMahon (PhD student; MS, University of Arizona): Phylogeny and Floral Diversity of Amorpheae (Fabaceae).
Shelley is interested in phylogenetic systematics and morphological and developmental evolution. Her dissertation research focuses on the evolution of floral form in the tribe Amorpheae, a group of 8 genera (ca. 240 species) in the subfamily Papilionoideae (Fabaceae). Amorpheae flowers demonstrate remarkable variation, particularly in the context of the well-conserved floral form found among most of the 12,000 or so species of papilionoids. Within Amorpheae, only the small genus Psorothamnus has flowers that are typically papilionoid, having 5 petals, strong bilateral symmetry, and androecium enclosed by the post-genitally fused keel petals. Other genera in Amorpheae have flowers that are open, nearly radially symmetric (most Errazurizia, Eysenhardtia, and Apoplanesia), and still others have flowers with one petal (Amorpha) or no petals (Parryella and Errazurizia in part). The most intriguing floral form modification is found in the genera Dalea and Marina. In these, the petals appear to be perched on a column formed by fusion of the stamen filaments.
Key questions that her research addresses include (1) what is the correct morphological interpretation of the epistemonous petals in Dalea and Marina, (2) how do changes in floral development explain the diverse mature floral forms, (3) what are the relationships among lineages in Amorpheae, and (4) what can be inferred about the evolution of Amorpheae floral diversity from comparative data on floral development and morphology, when analyzed in the context of a well-corroborated phylogeny. To answer these questions she is constructing a phylogeny using DNA sequence data from the chloroplast gene matK and studying floral morphology and development using histology and scanning electron microscopy.

Robin O'Quinn (PhD student): Phylogeny, Biogeography, and Shoot System Evolution in Drosera (Droseraceae).
Robin's project focuses on two aspects of the evolution of the sundews. The first is the origin of large, fleshy tubers formed underground by some Australian, Asian and African members of the genus. A primary goal of the project is to elucidate how shoot systems have been transformed in the evolution of the tubers. The second aspect of Robin's project focuses on the biogeography of this widespread genus. We will apply phylogeny reconstructions to enlighten our understanding of the distribution of the genus and to test hypotheses on common migration tracks proposed for Drosera by Croizat.

Emily Wynne (Undergraduate): Anther Evolution in Eucnide (Loasaceae)
Emily is investigating the evolutionary transformations in the anthers of Eucnide (Loasaceae). Most Eucnide have the typical angiosperm condition of having anthers with two thecae and four pollen sacs; however, the section Sympetaleia clade of Eucnide, which consists of the species E. aurea, E. rupestris, and E. tenella, is unusual in having only two pollen sacs. This project aims to understand whether the anthers of section Sympetaleia evolved via the loss of one entire theca or one pollen sac from each of two thecae.

Lab alumni:

Michael Moody (M.S. 1999): Phylogeny and Floral Diversity of Loasaceae Subfamily Gronovioideae.
The Loasaceae subfamily Gronovioideae consists of four genera (Cevallia, Gronovia, Fuertesia, and Petalonyx) that are unique in the family because of their uniovulate gynoecia and haplostemonous androecia. The distinctive floral features of the four genera led to their circumscription as a subfamily in the 1900 monograph of Loasaceae by Urban and Gilg. Since that time some authors have suggested that subfamily Gronovioideae is polyphyletic and their simple floral features (relative to other Loasaceae) are homoplasies. Michael's research tested the monophyly of Gronovioideae and explored the origins of their floral features. Sequences of the chloroplast gene matK were used to reconstruct evolutionary relationships among Loasaceae, which provided robust support for the monophyly of Gronovioideae as circumscribed by Urban and Gilg. Sequences of the ITS region of nrDNA were combined with matK data to reconstruct evolutionary relationships among Gronovioideae. These results showed that Gronovia and Fuertesia form a clade that is the sister of Cevallia. Those three genera form the sister clade of Petalonyx. – Michael is currently working on a Ph.D. in the Department of Ecology and Evolutionary Biology at the University of Connecticut.

Bob Kuzoff (Ph.D. 1998): The Diversification of Ovary Architecture in the Heuchera Group of Genera (Saxifragaceae).
Ovary position evolution has been very labile in Heuchera and related genera of Saxifragaceae. In particular some members of the group, especially species of Lithophragma, had been described previously as having superior ovaries, whereas others had inferior ovaries. This research demonstrated that no truly superior ovaries are present in Lithophragma or other members of the Heuchera group–all members of this clade are actually epigynous. Developmental studies showed how allometric shifts in the evolution of the clade have led to diverse ovary positions among the taxa. In particular, the rate of elongation in that part of the ovary below the insertion of the perianth and androecium relative to that part above their insertion differs among the taxa of the Heuchera group. Repeated shifts in the extent and relative rates of elongation growth in these two regions have been central to the diversification of ovary positions in the investigated clade. This research emphasized mapping allometric data on phylogenetic hypotheses that were constructed using ITS and 26S rDNA sequences. Part of this research pioneered the application of 26S expansion domain sequences in plant phylogenetic systematics. – Bob currently holds a Katherine Esau Postdoctoral Fellowship at the University of California at Davis.