Pollination of Bactris guineensis (Arecaceae), a potential economically exploitable fruit palm from the Colombian Caribbean

Abstract

Regardless of the ecological and economical importance of palms, their pollination strategies and the identities of their true pollinators are still contentious subjects. Bactris guineensis grows in open areas in lowland Caribbean Colombia. Its fruits have long been an important component of local economy and are now targeted for broader scale production for the Colombian market. We explored details of the reproductive biology of B. guineensis in its natural environment to understand the various elements of pollen flow dynamics that ensure optimal fruit yield. During two consecutive years, we investigated the phenology, floral biology and pollination ecology of a wild population of B. guineensis in the department of Sucre, northern Colombia. Monthly production of buds, inflorescences and ripe infructescences were quantified. Pollen carrying capacity, efficiency and fidelity of anthophilous insect species associated with B. guineensis were calculated and used to define their role as effective pollinators. Bactris guineensis is protogynous and exhibits ephemeral nocturnal anthesis. In spite of strict xenogamy the average reproductive success was over 75%, attributed to high pollen vector efficiency. Twenty-seven insect species representing three orders were recorded as floral visitors, but the only effective pollinators were minute flower weevils and sap beetles. At the beginning of the female phase of anthesis, when pistillate flowers are receptive, inflorescences of B. guineensis warm up to over 12 °C above ambient air and emit a balsamic scent, attracting swarms of several hundred to thousands of beetles loaded with pollen. A second, shorter-lasting floral heating event takes place by dusk in the following day (or the male phase), which culminates with pollen shedding of staminate flowers and departure of the pollinators. Anthesis events that are highly synchronized with activity patterns of specialized scent-oriented pollinators ensure the high reproductive success of B. guineensis at our study site. Plans for large scale production should prioritize insect-friendly practices and investigation on the role of volatile floral kairomones for pollinator attraction.