some info on pollen attractiveness
Foraging bees do not consume the pollen that they return to the hive. ... The presence of compounds identified as attractants to foraging bees in pollens (Hopkins et al. 1969) does not necessarily mean that the same compounds function as phagostimulants for consumption within the hive. There are documented examples of foraged pollens being poorly consumed once returned to the hive and, of certain pollens, being consumed despite exhibiting some level of toxicity towards bees (Schmidt et al. 1995).
The removal of pollen by flower-visiting insects is costly to plants, not only in terms of production, but also via lost reproductive potential. Modern angiosperms have evolved various reward strategies to limit these costs, yet many plant species still offer pollen as a sole or major reward for pollinating insects.
Pollen is a multimodal stimulus
Considering their diverse sensory capabilities, from a bees’
perspective pollen represents a multimodal stimulus, at
once providing foragers with gustatory, olfactory, visual
and mechanosensory cues, all of which could be used to
guide their foraging choices. Different pollen species are
likely to provide a widely varying array of sensory signals,
making it difficult to address the functions and interactions
of sensory modalities, or to determine which cues are most
salient for bees. Nonetheless, what is clearly established is that
pollen-foraging bees individually prefer some flowers over others
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comment: I think it's pretty clear from the research that bees don't bias their pollen collection based on nutritional value. Also, bee bread is not more attractive, nor more nutritious than fresh pollen. It also seems clear that some pollens are more attractive than others to bees, and we can probably understand this best when thinking of the presentation of human food. Food that is presented in an attractive way, that has seasonings, bright colors, pleasant aromas, will be consumed more readily than food that is plain, bland, or otherwise off-putting. Evolution has produced a variety of forms that are attractive to pollinators, so it should not surprise us if some flowers have included phytochemicals in their kitbag to entice bees to move pollen around. Clearly they don't produce pollen as food, but they produce enough of it so that pollinators can harvest the bulk of it and still effectively pollinate flowers.
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Schmidt, J. O., & Hanna, A. (2006). Chemical nature of phagostimulants in pollen attractive to honeybees. Journal of insect behavior, 19(4), 521-532.
Bridgett, R. J., Kirk, W. D. J., & Drijfhout, F. P. (2015). The use of a within-hive replication bioassay method to investigate the phagostimulatory effects of pollen, bee bread and pollen extracts, on free-flying honey bee colonies. Apidologie, 46(3), 315-325.
Nicholls, E., & Hempel de Ibarra, N. (2017). Assessment of pollen rewards by foraging bees. Functional Ecology, 31(1), 76-87.
PLB
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