Pollination biology and breeding system analysis of Ulmus wallichiana Planchon (Ulmaceae): a rare and threatened tree species of Central and Western Himalaya

Understanding the constraints on sexual reproduction of a plant species are important for predicting stability of the species in its natural habitat. In the absence of such data, any conservation efforts are arbitrary and remain ineffective. We investigated the reproductive ecology and breeding system of a rare and threatened tree species of central and western Himalaya, Ulmus wallichiana. The phenology, floral biology and pollination mechanism were observed in two populations for three consecutive years. In addition, breeding system and pollen limitation were examined using hand-pollination experiments. Flowering in U. wallichiana begins in early March during which trees are leafless and small, pinkish-white flowers cover the entire tree. Pollination is accomplished exclusively by wind with short average distances for pollen dispersal (~50 m). Pollination manipulation experiments showed high fruit set on outcrossing indicating U. wallichiana is xenogamous. However, a small percent of f...