American Journal of Botany
Members of at least two unrelated genera of plants, Dalechampia (Euphorbiaceae) and Clusia (Guttiferae), attract pollinators by secreting resins from floral structures. Bees that pollinate these flowers collect and use the resin in nest construction; these include Euglossa, E ulaema. Eufriesea, Trigona and Hypanthidium in the neotropics, and Heriades in Africa. Floral resins are slow in hardening as compared with many other plant resins; this facilitates collection and storage by bees, hence probably enhancing the attractiveness of the flowers. Floral resins are probably of great utility and dependability and may be an especially important resource to certain bees, which in turn are major pollinators of many species of tropical plants. Bees appear to forage floral resin using a "strategy" of energy efficiency; large bees collect resin only from copious sources, smaller bees collect resin from sources with small amounts as well as from sources with large amounts of resin. Resin secretion in flowers may have originated as defense against herbivores and secondarily assumed the role of pollinator reward.
Armbruster, W. Scott, "The Role of Resin in Angiosperm Pollination: Ecological and Chemical Considerations" (1984). An. Paper 103.
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