Flowering phenology and pollination of Hoya verticillata (Vahl) G. Don

Abstract

Hoya R. Brown is genus of climbing epiphytes or lithophytes with beautiful and fragrance flowers, belonging to the subfamily Asclepiadoideae, family Apocynaceae. There were a few studies of pollination of Hoya, while the number of the plants in natural populations are degrading in Thailand because of threats like habitat destruction and illegal trade. Hoya verticillata is the most common species occurring widely throughout the country. In this study, its pollination biology at Ban Phe Botanic Garden, Rayong was revealed. The results showed that H. verticillata is a nocturnal plant, with night-blooming flowers. The flowers took an average of 21.97 days to develop from floral bud to the end of anthesis, with blooming period lasted 1-4 days. During anthesis, a strong sweet fragrance was emitted from osmophore located on the adaxial surface of the corolla lobes. Copious nectar was secreted from the nectariferous tissue hidden behind the guide rails and collected at the base of gynostegium to reward the pollinators. The main visitors were insects in order Lepidoptera. Moths from the families Erebidae and Geometridae were likely to be the most effective potential pollinators for H. verticillata. They visited regularly the flowers and while probing for nectar, perched on and walked on the corona of different flowers. This contact of essential organs of flowers on the legs of moths would most likely lead to pollination. The range of pollen transfer efficiency (PTE) in this population was between 0.0% and 3.60%.