The sweet jelly of Combretum lanceolatum flowers (Combretaceae): a cornucopia resource for bird pollinators in the Pantanal, western Brazil

The pollination biology of the neotropical scandent shrub Combretum lanceol atum was studied in the seasonally-flooded Pantanal region in western Brazi l. This plant bears horizontally oriented inflorescences, whose yellowish g reen flowers begin to expand at dusk and are fully open at dawn. Instead of fluid nectar the flowers produce sweet gelatinous secretion in form of pel lets. The glandular complex of the flower is composed of the inner wall of the receptacle and its tubular extension, being equivalent to the nectarife rous disk of the nectar-producing species within the genus. The jelly is pr oduced at night, contains mannan and is imbibed by free hexoses. It origina tes by swelling and disintegration of the inner wall, after contact with th e nectar generated concomitantly in the mesophyll. Combretum lanceolatum is unique within the genus in its production of jelly pellets instead of liqu id nectar. A new term, the jelly-flower, is proposed for flowers with this kind of reward. The pellet is not replaced once removed by a bird, and thus resembles a fruit in its availability to consumers, another unique feature that distinguishes this species within the genus. The jelly pellets offere d by the many flowered branches attract a great diversity of bird visitors (28 species from eight families), which feed on this copious food resource and pollinate the flowers. The most effective pollinators probably are thru shes, tanagers, and orioles. Flocking parakeets and macaws sometimes feed o n the petals, thus acting as flower plunderers. Combretum lanceolatum prese nts a high fruit set under natural conditions, which likely favours its spr eading and becoming a weed species.