ORCHID POLLINATION: RECENT DEVELOPMENTS FROM BRAZIL

In the last six years, a number of contributions on orchid pollination have been made by Brazilian or Brazilian-based researchers and a brief review of these papers is given to communicate some remarkable findings which are part of ongoing projects.

Abstract

Because of their remarkable flower morphology, orchids are particularly interesting objects of study. Most orchid species hold their pollen in discrete packs, so-called pollinia (singular; pollinium). These pollinia, together with other pollinium stalks, form more or less complex translatory units, so-called pollinaria (singular: pollinarium). During their visits to the flowers, orchid pollinators dislodge these pollinaria and deposit their pollen content during successive flower visits. Pollinators may be attracted to the flowers in many ways. Many orchids offer flower parts or secretions (nectar, trichomes, wax-like or resin-like compounds, aromatic compounds, oils, etc.) that can be gathered/foraged by their pollinators. Yet, many orchids “deceive” their pollinators and offer no flower reward. Many orchids are merely “food-frauds”, displaying a set of flower features (colors, fragrances) that apparently elicit the attraction of food-seeking animals. A much more sophisticated kind of deception involves the so-called “pseudocopulation”. In this kind of pollination strategy, flower features (mainly flower fragrance, but also coloration and ‐ when applicable - indument or pilosity) mimic these of some female insects (mostly Hymenoptera). Pollination is achieved when male insects attempt copulation with these “dummy females”. Since the times of Darwin, the pollination biology of the orchids has received the attention of both, lay persons and scientists. The combination of their remarkable flower structure plus their often bizarre pollination strategies has played a major role in the understanding of evolution, morphology and pollination biology as a whole. Orchid pollination studies in the Neotropics experienced a boost in the sixties (Van der Pijl & Dodson 1966, and literature therein) with the understanding of Euglossini behaviour. The males of these bees gather fragrances (aromatics, terpenes, sesquiterpenes, etc.) at specialized parts of the lip of many orchid species from different neotropical subtribes (specially Catasetinae, Stanhopeinae and some Zygopetalinae) and perform the pollination during successive flower visits. The reasons why Euglossini males collect these compounds are still a matter of speculation (see Singer & Koehler 2003 for a brief discussion of the theories). Yet, it is possible that these compounds are somehow used during courtship. In the last six years, a number of contributions on orchid pollination have been made by Brazilian or Brazilian-based researchers. The purpose of this contribution is to give a brief review of these papers and to communicate some ‐ in my opinion - remarkable findings which are part of ongoing projects. I have chosen to describe the findings by taxonomic groups.