HOST-SPECIFICITY AND LOW REPRODUCTIVE SUCCESS IN THE RARE ENDEMIC PUERTO-RICAN ORCHID LEPANTHES CARITENSIS

Tree host specificity is unusual in orchids. Here we show host specifi city in a rare orchid and describe other potential causes of host spec ificity. Lepanthes caritensis occurs only in Carite State Forest, Puer to Rico. We found L. caritensis only on the largest individuals of one species of tree, Micropholis guyanensis, limiting the orchid to only 7% of the potential tree community >5 cm dbh. Orchid occurrence was as sociated with high moss cover on M. guyanensis. The abundance of undes cribed fungi cultured from tree bark was negatively associated with or chid presence. Low fruit production in orchids is not uncommon, but re productive success in L, caritensis appeared to be unusually low; no f ruits were produced by 68 adults during 16 months of observation. If t his trend of low reproductive success is borne out over time, it would suggest an obvious explanation for the rarity of L. caritensis. Our r esults suggest ways to manage populations of L. caritensis, but also r eveal aspects of tropical orchid biology (e.g. the importance of fungi and mosses for orchid establishment) which require more thorough inve stigation. (C) 1998 Elsevier Science Ltd. All rights reserved.