title: Specialized bees fail to develop on non-host pollen: do plants chemically protect their pollen?
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.
authors.affiliation: ETH Zurich, Institute of Plant Sciences, Applied Entomology, Schmelzbergstrasse 9/LFO, 8092 Zurich, Switzerland.
authors.forename: Christophe J
authors.initials: CJ
authors.lastname: Praz
authors.forename: Andreas
authors.initials: A
authors.lastname: Müller
authors.forename: Silvia
authors.initials: S
authors.lastname: Dorn
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D019659:Asteraceae / Q000502:physiology; D001516:Bees / Q000254:growth & development / Q000502:physiology*; D019607:Brassicaceae / Q000502:physiology; D036661:Echium / Q000502:physiology; D017753:Ecosystem; D005247:Feeding Behavior / Q000502:physiology*; D035264:Flowers / Q000502:physiology*; D007814:Larva; D011058:Pollen; D011156:Population Density; D011157:Population Dynamics; D031947:Ranunculus / Q000502:physiology; D013045:Species Specificity