The role of beetles in the pollination of the mangrove palm Nypa fruticans

Abstract

The flowers of the mangrove palm Nypa fruticans attracts a diverse array of potential pollinators. However, little is known about the pollination mechanism and which functional groups are the key pollinators. Inflorescences of nine nipa palms of different flowering stages were observed three times a day between sunrise and sunset in Thailand. The apparent entomofauna activity was recorded and all inflorescences were collected for extraction and identification of the beetle fauna. Beetles extracted from female inflorescences were measured for pollen load. In addition, thermogenesis was recorded over two days on two separate inflorescences. The most frequent visitors were species of nitidulid (genus Epuraea and the subfamily Cillaeinae) and curculionid beetles. Although they only carried small amounts of pollen grains, these groups of beetles were omnipresent. Thermogenesis peaked around 6.30 am with temperature elevations reaching 6° above ambient. The result obtained in this study are compared with those of previous studies conducted elsewhere in Thailand and in the Philippinies. The combined evidence strongly suggests a pivotal role in pollination of beetle visitors to the inflorescences of Nypa fruticans.