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Sat, 7 Nov 2009 10:35:52 -0500 |
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Recent work questions the nutritional quality of many types of pollen
sources that bees commonly use for food
SPECIALIZED BEES FAIL TO DEVELOP ON NON-HOST POLLEN: DO PLANTS
CHEMICALLY PROTECT THEIR POLLEN?
CHRISTOPHE J. PRAZ, ANDREAS MULLER AND SILVIA DORN
Ecology, 89(3), 2008, pp. 795–804
Abstract. Bees require large amounts of pollen for their own
reproduction. While several morphological flower traits are known to
have evolved to protect plants against excessive pollen harvesting by
bees, little is known on how selection to minimize pollen loss acts on
the chemical composition of pollen. In this study, we traced the
larval development of four solitary bee species, each specialized on a
different pollen source, when reared on non-host pollen by
transferring unhatched eggs of one species onto the pollen provisions
of another species. Pollen diets of Asteraceae and Ranunculus
(Ranunculaceae) proved to be inadequate for all bee species tested
except those specialized on these plants. Further, pollen of Sinapis
(Brassicaceae) and Echium (Boraginaceae) failed to support larval
development in one bee species specialized on Campanula
(Campanulaceae). Our results strongly suggest that pollen of these
four taxonomic groups possess protective properties that hamper
digestion and thus challenge the general view of pollen as an easy-to-
use protein source for flower visitors.
* * *
Pollen of Asteraceae was shown to be of poor quality for the honey
bee, for bumblebees as well as for two solitary bee species. Many
members of Asteraceae are copious nectar producers. Centaurea
(knapweed), Helianthus annuus (domestic sunflower), and some species
of Solidago (goldenrod) are major "honey plants". Some members of the
Asteraceae are economically important as weeds. Notably in the United
States are the ragwort (Senecio jacobaea), groundsel (Senecio
vulgaris), and Taraxacum (dandelion).
Peter Loring Borst
Ithaca, NY USA
+42.347999, -76.495239
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