An ecological study of Pedicularis dendrothauma, an arboreal hemiparasitic epiphyte from Nepal

Pedicularis dendrothauma is an arboreal epiphytic hemiparasite that was recently discovered in Nepal. We present results of preliminary studies on its habitat, demography, hemiparasitism, flower development, and pollination. While showing a strong preference for Abies spectabilis trunks and branches as a substrate, P. dendrothauma also grows on other species of trees and shrubs in the understorey as well as on dead wood on the forest floor, and only very rarely is rooted in soil or on rocks, rooted in a bryophyte layer. Demographic monitoring of the population in 1999 and 2001 allows us to begin to predict longevity, average size of flowering plants, and survivorship and flowering probability on different substrates. We demonstrate that individual plants of P. dendrothauma live at least four, and probably at least five years. Studies of haustoria show that the species has retained its hemiparasitic habit despite having moved from a terrestrial to an arboreal habitat. Flowering probability increases with plant size; an average flowering plant has five leaves and a longest leaf that measures 21.5 cm. Survivorship varies from substrate to substrate, with the greatest survivorship over a two year period occurring in plants growing on living trees. Flowering probability was the same for plants growing on living trees as it was for plants on dead wood. Studies of flower development suggest that plants growing high in the canopy proceeded through the stages of floral development more rapidly than plants nearer ground level. Despite many hours of field observation, the method of pollination remains a mystery; we suggest different possible pollination mechanisms.