Leafless members of tribe Vandeae (Orchidaceae) have undergone extreme reduction in habit and represent a novel adaptation to the canopy environment. In these leafless orchids, photosynthetic leaves are absent or reduced and deciduous. Instead, green roots have assumed the role of food-assimilation. Many also possess an extremely condensed stem, making the plant appear "shootless." Vandeae form a large, pantropical group of orchids traditionally divided into three subtribes: Aeridinae, Aerangidinae, and Angraecinae. Leafless taxa occur throughout Vandeae and are geographically distributed in Africa, Asia, and tropical America. While the most widely accepted classification system is based solely on floral morphology, our study was based upon sequence data primarily from ITS nrDNA. Preliminary results from this nuclear data set indicate the African Aerangidinae form a paraphyletic grade from which the African and Madagascan Angraecinae are derived. The Asian Aeridinae, however, do form a well-supported clade. Phylogenetic relationships of leafless neotropical Angraecinae (Dendrophylax, Harrisella, Polyradicion, and Campylocentrum) were estimated using combined nuclear (ITS) and plastid (trnL-F) data sets, with African Angraecum species as outgroups. Our molecular analyses support only two monophyletic genera, Campylocentrum and a broad Dendrophylax, which seem to indicate that traditional approaches of classification, based primarily on floral morphology, are not predictive of phylogenetic relationships.

Key words: Aerangidinae, Aeridinae, Angraecinae, ITS, Orchidaceae, Vandeae