Georgia, USA

Ph.D Candidate, U.M.-St. Louis

MS University of Georgia, 1999

BS Georgia Southern University, 1994

Research Interests:

Normally angiosperm flowers have a relatively simple and stable organization with floral organs arising in a sequential manner around the floral axis (i.e., sepals, petals, stamens, and then carpels). The great diversity of floral form in my study group, Garcinia L. (Clusiaceae) - a pantropical genus of ca. 350 species of dioecious trees, makes this organization, at times, difficult to discern. In some lineages, it can be difficult to ascertain the identity of structures in staminate and pistillate flowers both within and between species. In one case, it may be that androecial and gynoecial material occupy the same whorl - a potential case of homeosis. There are other variable features of Garcinia flowers. The stamens (and the corresponding parts in pistillate ones) vary in number, degree of fusion to each other and to the petals, and in whether these organs are clustered into groups (fascicles) or freely distributed in the flower. The anthers vary in shape, number of sporangia, and whether or not they are multi-chambered. Sterile reproductive organs (pistillodes, staminodes, and fasisclodes) can be present or absent. Indeed, the great diversity of floral forms in Garcinia and the closely related genus Clusia prompted some to propose the that there may be some developmental genetic factor(s) operating within the lineage containing Garcinia, Clusia, and relatives (the subfamily Clusioideae) that cause a relaxation in the organization of flowers within this group. Within Garcinia it is difficult to begin evaluating hypotheses of floral evolution because floral form within this group has not been well characterized and because no comprehensive phylogeny exists for the genus.

I am using two nuclear genes (the low-copy gene waxy and ITS) to provide a genus-wide phylogeny for Garcinia, and to identify particular lineages of Garcinia that exhibit intriguing evolutionary changes in floral morphology. I have also begun studies of floral development and anatomy that will allow me to better characterize floral form within this group and will permit preliminary evaluation of floral evolution in the genus.

Garcinia is in the same botanical family as St. John's wort (Clusiaceae) and occupies forests of tropical regions throughout the world. Plants are identified as Garcinia in part by their berry-like fruits with a single seed per chamber and sticky white to yellow latex that is released when the bark of a tree or twig is cut. Some notable species that belong to this genus include Mangosteen (G. mangostana, see image of flower on right), a sweet tasting fruit widely popular in southeast Asia and often referred to as the "Queen of Fruits," and G. hanburyi, the source of a dye used to to dye the robes of Buddhist monks.

To view a report from a field trip that I conducted in Southeast Asia during the early part of 2003 click here.

Publications:

Sweeney, P. W., J. C. Bradford, and P. P. Lowry II. 2004. Phylogenetic position of the New Caledonian endemic Hooglandia (Cunoniaceae) as determined by maximum parsimony analysis of chloroplast DNA. Annals of the Missouri Botanical Garden 91 (2), in press.

Sweeney, P. W. and R. A. Price. 2001. A multivariate morphological analysis of the Cardamine concatenata alliance (Brassicaceae). Brittonia 53(1): 82-95.

Sweeney, P. W. and R. A. Price. 2000. Polyphyly of the genus Dentaria (Brassicaceae): Evidence from trnL intron and ndhF sequence data. Systematic Botany 25(3): 468-478.

Email: patrick.sweeney@mobot.org