We acknowledge grants from the Smithsonian Institution Scholarly Studies Program and the Walcott Botanical Endowment to DWR, and from the Exxon Fellowship program. We are indebted to Robert Schmalzel for field collection and preparation of herbarium material, as well as for descriptions; and T. M. Aide and A. Herre in Panama. For extensive collaboration in herbarium work and slide Preparation, in addition to providing slide material appreciatio n for the aid that the late G. Thanikaimo ni, French Institute, Pondichéry, provided in the form of reference material. W. D'Arcy and P. Raven, Missouri Botanical Garden, were instrument al inWe also thank M. Correa, University of Panama herbarium, S.
1. Spatial and temporal availability of pollen helps shape bee foraging behaviour and productivity, which has been studied in great detail at the landscape level, but never in a diverse tropical forest.2. To study the effect of spatio-temporal variation in resource distribution on pollen use and productivity, we identified pollen from spatially explicit nest collections of two generalist sweat bees, Megalopta genalis Meade-Waldo and M. centralis Friese, from Barro Colorado Island, Panama, a 50-ha forest dynamics plot during the 2007 dry and early wet seasons. Pollen from nests collected in 1998-1999 without spatial information was also identified.3. Bees used pollen of at least 64 species; many of these occurred in only one collection. The 2007 collections contained pollen of 35 different species, but were dominated by five species, especially Hura crepitans L. and Pseudobombax septenatum (Jacq.) Dugand. 4. Temporal availability, but not distance from nest, influenced flower use at a 50-ha scale.5. Body size was not associated with minimum flight distance as inferred from pollen collections.6. Nest productivity and pollen diversity decreased from the dry to wet seasons, mirroring community-level availability of floral resources.7. Results suggest that on a scale of 50 ha, bees are choosing certain host plant species regardless of distance from the nest, but adjusting foraging behaviour opportunistically based on the temporal availability of host flowers.
We found that the nest ofTrigona corvina(Apidae; Meliponini) consists mainly of pollen exines from bee excrement, forming a scutellum shield encasing the colony. A 20-year-old nest (1980–2000) from a lowland Panama forested habitat was sawed in half longitudinally, and a 95 cm transect was systematically sampled each 5 cm. Samples subjected to detailed pollen analysis held 72 botanical species belonging to 65 genera in 41 families. Over 90% of scutellum pollen volume was Cecropiaceae and Arecaceae, among grains. Potentially the oldest samples, in the middle of the nest, indicate that Mimosoideae, Euphorbiaceae, and Bombacaceae (now Malvaceae) were lost when Africanized honey bee competitors colonized Panama in 1984.Cecropiadeposited in the nest increased markedly after landscape-level vegetation disturbance. Pollen fromCavanillesiademonstrated that the foraging range encompassed 3 and perhaps 500 plant species.Trigona corvinaprimarily foraged on plants with large inflorescences, consistent with foraging theory considering their aggressive behavior.
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