Arethuseae

Abstract: Circumscriptions of Arethuseae have varied since the tribe was first described by John Lindley in 1840, containing over ninety genera among the different authors. The latest system of Arethuseae defined by Dressler, including around thirty genera, is the most commonly accepted today. The goals of this study are to assess whether Arethuseae sensu Dressler and component subtribes are monophyletic and evaluate the position(s) of Arethuseae within Orchidaceae. Sequences of two plastid genes, matK and rbcL, have been obtained for 24 representative genera of Arethuseae in Dressler's latest two taxonomic systems for the tribe, plus 46 other genera throughout Orchidaceae. Both separate and combined analyses of the matK and rbcL data indicate that the tribe may not be monophyletic, which is also true for most subtribes within Arethuseae. Furthermore, matK data suggest that this gene may be non-functional within Orchidaceae. Communicating Editor: Kathleen A. Kron

Abstract: Coelogyne victoria-reginae, a new species of section Proliferae, from Natma Taung (Mt.Victoria) National Park, Chin State, Myanmar, is described and illustrated. It is morphologically similar to C. prolifera, but the clustered pseudobulbs, pure brownish- red flowers and column wing with irregular notches at the apex of the new species differ from the other species. A preliminary risk-of-extinction assessment shows that the new species is regarded as EN C2a[i] according to the IUCN Red List Categories and Criteria.

Abstract: We studied the variation in the pollinarium and pistil of Epidendroideae and reconstructed the ancestral states of the characters (pollinia number, pollinium orientation, pollinium with suture, and pollinium texture). The pollinarium is complete (formed by pollinium, caudicle, stipe, and viscidium) in Vandeae, Epidendreae, and Cymbidieae, but the caudicle is absent in some Aeridinae and the viscidium in Laeliinae and Pleurothallidinae. Neottieae, Arethuseae, Sobralieae, Epidendreae, and Xerorchideae included some genera having sessile pollinia. The more frequent state in the family is to have two pollinia, followed by four, eight, and six pollinia. The pistil is unilocular, although it seems to have experienced reversals several times within Epidendroideae because intermediate states were observed (e.g. Vanda and Angraecum). In these cases, a prolongation of the placental tissue is developed that in Huntleya and Peristeria make contact but do not fuse. Most members of the subfamily have pistil composed of three carpels divided into six emerging valves, but only three are fertile. In Cattleya and Sophronitis the sterile valves are much reduced and the pistil seems to have only three valves. We have generated useful and valuable information to understand the evolution of the reproductive organs in Epidendroideae. Probably, these transformations in the pollinarium and pistil have co-evolved in tandem with pollinators to make the pollination more efficient. Our results suggest that the common ancestor of Epidendroideae had a complete pollinarium, formed probably of four juxtaposed granular pollinia without suture, bearing caudicle, tegular stipe and viscidium, but several early transformations occurred during the Epidendroideae diversification.