Niche differentiation in nectar-collecting stingless bees: the influence of morphology, floral choice and interference competition

1. Dozens of social bee species, most of them stingless bees, occur sympatrically in the tropics. The proximate mechanisms through which they partition their resources are, apart from aggressive interactions between Trigona species, not well studied. In the work reported here, niche differentiation...

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Bibliographic Details
Published in:Ecological entomology 1999-11, Vol.24 (4), p.380-388
Main Authors: Biesmeijer, J.C, Richter, J.A.P, Smeets, M.A.J.P, Sommeijer, M.J
Format: Article
Language:English
Subjects:
anatomy and morphology
Animal and plant ecology
Animal, plant and microbial ecology
Biological and medical sciences
color
concentration
Costa Rica
Curculionidae
feeding preferences
Flower choice
flowers
foraging
Fundamental and applied biological sciences. Psychology
interspecific competition
Melipona
melipona beecheii
melipona fasciata
nectar
nectar feeding
nectar foraging
niche differentiation
resource partitioning
shade
solar radiation
stingless bees
sugars
Synecology
Terrestrial ecosystems
Trigona
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Summary:1. Dozens of social bee species, most of them stingless bees, occur sympatrically in the tropics. The proximate mechanisms through which they partition their resources are, apart from aggressive interactions between Trigona species, not well studied. In the work reported here, niche differentiation at patch level was studied, using two species of Melipona that occur sympatrically in the Central Pacific part of Costa Rica. Foragers of Melipona beecheii are known to collect more concentrated nectar than do Melipona fasciata foragers, even from the same plant species. This observation raises the question of what mechanism leads to such partitioning of nectar resources? To address this question, the roles of bee morphology, floral preferences, and interference competition in partitioning of nectar sources were studied. 2. It was shown experimentally that the feeding rate of both species was highest at 60% nectar concentration. Melipona fasciata preferred 60-70% concentrations to less concentrated solutions, whereas M. beecheii ignored 20% solutions and visited the other solutions equally often. Both species preferred sucrose to glucose and fructose. Melipona beecheii, with a yellowish coloured body, preferred sunny patches, whereas M. fasciata, with a dark brown body, preferred shady patches. Interference competition between the species occurred when they visited the same sugar-water feeder: M. fasciata was dominant over M. beecheii. 3. The nectar foraging strategies of the two species can be summarised as follows: M. beecheii is able to visit sunlit patches, due to its lighter body colour, and is thus able to collect nectar of optimal or near optimal sugar concentration (40-65%). Individuals do not actively choose nectar with a high concentration of sugar, but the average sugar concentration in bee-collected nectar will typically be high in sunlit patches. Melipona fasciata, on the other hand, avoids sunlit patches, but actively chooses the richest nectar in shady patches and tries to dominate such patches. Thus, niche differentiation occurs according to the radiation regime at flower patches, and interference competition will occur rarely under natural conditions. The role of similar mechanisms in other closely related stingless bees is discussed.
ISSN:0307-6946
1365-2311
DOI:10.1046/j.1365-2311.1999.00220.x