Epidendroideae comprise approximately 80% of the species of Orchidaceae. The subfamily includes much of the variation that is found in anther characters, traditionally the most important in orchid classification. Simultaneous parsimony analysis of plastid rbcL, matK, trnL-F spacer and intron, nuclear 26S and ITS, and mitochondrial nad1b-c intron reveals support for many tribal and subtribal groups within the family. The terrestrial tribe Neottieae is strongly supported as sister to the remainder of the subfamily. The next resolved clades include soft-pollinia groups, including Triphoreae, Tropidieae, Nervilieae, and Sobraliinae, some of which have at times been associated with other subfamilies. The "upper" epidendroids form a monophyletic group that comprises largely epiphytic plants with more specialized modes of pollen delivery, the pollinia often being associated with stalks of various types. The non-vandoid groups include many traditionally recognized subtribes, such as Epidendreae, comprising Laeliinae + Pleurothallidinae, and a narrowly defined Arethuseae + Coelogyninae. The higher level associations of many of these groups are still unclear because of the large number of short branches at the base of this clade. The majority of vandoid orchids, those possessing an early-bending incumbent anther, superposed pollinia, and cellular pollinium stalk, form a well-supported clade that comprises Dressler's Maxillarieae (monophyletic) and Cymbidieae (paraphyletic). Other vandoids comprise the largely Old World Vandeae, sister to Polystachyinae, and Calypsoeae. Character transformations confirmed by these patterns include a progression from soft to hard pollinia, changes from four to either two or eight pollinia, and shifts from terminal to lateral inflorescences. In order to resolve the relationships of the major clades at the base of the subfamily, which are confounded by short branch lengths that may reflect rapid radiation, additional focused sampling is needed.

Key words: DNA, Epidendroideae, molecular analysis, Orchidaceae, phylogeny