Pollination Ecology of a Forest-Dominant Palm (Orbignya phalerata Mart.) in Northern Brazil

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Abstract
Inflorescence morphology, phenology, and pollination of the ecologically dominant and economically important babassu palm (Orbignya phalerata) were studied in northern Brazil. The breeding system of this species is complex. Inflorescences are either morphologically staminate or androgynous. In a functional sense the former are invariably male and the latter generally female, although an intermediate, functionally hermaphroditic type occurs rarely. Individual trees vary from exclusively staminate to predominantly androgynous. In the populations studied, flowering peaked in the rainy season (January-May). Three lines of evidence led us to consider self-pollination extremely rare. First, functionally hermaphroditic inflorescences exhibited protogyny: pistillate flowers were receptive during the first 48 hr following anthesis, and staminate flowers released pollen only thereafter. Second, seed set did not occur in androgynous inflorescences that had been isolated from eternal pollen sources. Third, simultaneous flowering of staminate and androgynous inflorescences in individual palms was rare. Despite the high abundance and diversity of insects visiting inflorescences, detailed observations indicated that the only likely insect pollinator is the nitidulid beetle Mystrops mexicana. This species occurs in abundance on both flower types and was observed in babassu at sites up to ca 600 km distant, indicating that the association is widespread. Fruit set in inflorescences that had been bagged to exclude insects but not wind-borne pollen indicated that wind pollination also occurs. The latter appears to be more common in such relatively open sites at pastures. The combination of two pollination syndromes clearly enhances this species'' adaptability to a wide range of habitats. Evidence from other studies suggests that the combination of entomophily and anemophily may be a recurring phenomenon in palms.

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