PHYLOGENY AND FLORAL DIVERSITY IN THE GENUS GARCINIA (CLUSIACEAE) AND RELATIVES Patrick W. Sweeney 1 University of Missouri–St. Louis, Department of Biology, One University Boulevard, St. Louis, Missouri 63121, U.S.A.; and Missouri Botanical Garden, P.O. Box 299, St. Louis, Missouri 63166, U.S.A. The pantropical genus Garcinia comprises more than 250 species of dioecious trees and shrubs that are a common component of lowland tropical forests. The genus exhibits as extreme a diversity of floral form as is found anywhere in angiosperms, and there are many unresolved taxonomic issues surrounding it. To evaluate morphology-based classification schemes involving Garcinia and its relatives and to examine floral diversity in the genus within a phylogenetic context, higher-level relationships among a broad sample of Garcinia and close relatives were inferred by conducting Bayesian, parsimony, and likelihood analyses of 70 species with sequence data from two nuclear genes, granule-bound starch synthase (GBSSI) and the internal transcribed spacer (ITS). These results support a broad circumscription of Garcinia and the monophyly of tribe Garcinieae. Within Garcinia, several clades are supported that share particular combinations of floral characters and generally correspond to sections recognized in the most recent treatment of the genus. The phylogenies suggest that all species of Garcinia fall into two major lineages, one characterized by the presence of nectariferous floral organs of uncertain derivation, such as central disks, antesepalous lobes, and intrastaminal ring-shaped disks, and the other by their absence. Keywords: Clusiaceae, floral evolution, Garcinia, GBSSI, ITS, phylogeny. Online enhancement: appendix table. Introduction Garcinia comprises more than 250 species of dioecious small shrubs to medium-sized trees that are a common component of lowland tropical forests. The genus exhibits several features that are of general interest to biologists. In many areas, particularly Madagascar and Southeast Asia, where it has centers of diver- sity, the genus is notable for its high levels of sympatric species diversity (Ashton 1988; Whitmore 1998; Lee et al. 2002; Thomas et al. 2003), and this diversity is especially notable in that spe- cies that are both dioecious and agamospermous may be wide- spread in the genus (Ashton 1988; Richards 1990; Thomas 1997; Allem 2004). From an economic standpoint, Garcinia is probably best known for the highly prized fruit of mango- steen (G. mangostana L.), a tree native to southeastern Asia; moreover, mangosteen and other species (e.g., G. gummi-gutta [L.] N. Robson or ‘‘G. cambogia’’) have become the focus of pharmacological studies (Heymsfield et al. 1998; Mackeen et al. 2000; Ho et al. 2002; Jung et al. 2006), and a large natural- supplement industry has formed around these species. Finally, Garcinia exhibits some of the most extreme diversity of floral form, particularly in the androecium, found in angiosperms. While many species of Garcinia have four free sepals and four free petals (fig. 1), others have two, three, or five or more perianth parts per whorl, and in some the sepals can be com- pletely fused to each other in bud. The stamens, or staminodes in pistillate flowers, vary in number, in whether these organs are clustered into groups (i.e., fasciculate) and fused together (i.e., phalangiate) or distributed evenly (i.e., nonfasciculate) and free, in degree of fusion to each other when clustered, and in de- gree of fusion to the petals. The anthers vary in the shape of the thecae, the number of loculi (thecae) per anther, and whether lo- celli are present or absent. Pistillodes may be present or absent. In pistillate flowers, style branches can be present or absent and the surface ornamentation of the stigma is very diverse. Some groups have additional disk-, lobe-, or ring-shaped structures in the flowers that are called ‘‘fasciclodes’’ (Robson 1972; Stevens 2006) and have been variously interpreted as sterile reproductive organs (Robson 1972; Jones 1980) or as of receptacular origin (Pierre 1883; Leins and Erbar 1991). Field observations sug- gest that these structures are nectariferous (P. W. Sweeney, per- sonal observation). The diversity of floral form in Garcinia led to a reliance on flo- ral characters by earlier workers delimiting the genus and con- structing infrageneric classifications. Based largely on floral morphology, circumscriptions of Garcinia have varied, with sev- eral segregate genera being recognized (Planchon and Triana 1860; Bentham 1862; Engler 1893, 1925; Vesque 1893; Perrier de la Ba ˆ thie 1948, 1951). These include Ochrocarpos Thouars (two sepals fused in bud vs. four or more free sepals in Garcinia; fig. 1H), Pentaphalangium Warb. (five-merous, staminal phalanges adnate to petals vs. four-merous, phalanges free; fig. 1F), Rheedia L. (two sepals, free stamens vs. four sepals, fascicled androecia; fig. 1N,1P), and Tripetalum Schumann (three- 1 Current address: Division of Botany, Yale University Herbarium, Peabody Museum of Natural History, Yale University, P.O. Box 208118, New Haven, Connecticut 06250, U.S.A.; e-mail: patrick.sweeney@yale .edu. Manuscript received February 2008; revised manuscript received April 2008. 1288 Int. J. Plant Sci. 169(9):1288–1303. 2008. Ó 2008 by The University of Chicago. All rights reserved. 1058-5893/2008/16909-0014$15.00 DOI: 10.1086/591990