Pollination Systems in Palms (Arecaceae)

male flowers of Caryota sympetala

By Andrew Henderson

The palm family (Arecaceae) is a family of flowering plants with 182 genera and about 2,460 species. Plants have woody, often large stems and occur predominantly in the tropics. Palms are different from many other plants because they have many, small flowers aggregated into large inflorescences. Pollination has been studied in only about 6% of the species. Nevertheless, this review shows that palms have a diverse array of pollinators. A few species have unusual pollination systems. For example, the Asian genus Eugeissona is pollinated by nocturnal mammals (mostly pentailed shrews), who are attracted to the inflorescences by the abundant, alcoholic nectar that is produced by the flowers. A Central American genus, Calyptrogyne, has flowers which open at night and are pollinated by bats who are attracted by the scent and sweet-tasting petals of the flowers. However, most palms seem to be pollinated either by beetles or by bees/flies. There are two main groups of beetle pollinators, weevils (Curculionidae) and sap beetles (Nitidulidae). These have extremely complicated relationships with the palms and their life cycle takes place entirely on palm inflorescences. Adult beetles are attracted to male-phase flowers by both scent and pollen. They are then attracted to the female-phase flowers, usually by deceit, because the female-phase flowers produce the same scent as the male-phase flowers. Beetles mate on the inflorescences, and the females lay eggs on different parts of the flowers or inflorescences. The larvae then develop on the inflorescences. Bees and flies have a less complicated relationship with palm inflorescences. They are attracted to flowers by sweet scent, pollen, and nectar. One interesting feature of palm inflorescences is that beetle-pollinated species attract bees/flies to their inflorescences, and bee/fly-pollinated species attract beetles. In some cases we can see a ‘switch’ from a beetle-pollinated species to a closely related species with bee/fly pollination. However, it is not clear what causes this switch. One general conclusion of this review is that the interaction between palms and their pollinators is very complicated and we still do not know much about it. 

Read the scientific publication in JPE