Hi Richard

I did extensive research into pollen for an article in the ABJ. What I found is that all pollen is extremely nutritious by nature, as it contains essential amino acids. There are differences in the amount of protein and the balance of the amino acids. There are some pollens that are not adequate for the nutritional requirements of the colony just as there are many proteinaceous foods that do not contain all the essential amino acids for human nutrition. But honey bees tend to forage multiple sources and combine them so the overall diet is usually adequate, just as humans do. 

I also found that while honey bees can detect subtle differences in sugar content of nectar, they do not have the capacity to evaluate the nutritional content of pollen. Likewise, most people would have little idea about nutrition were it not for the fact that this is in the curricula of elementary school kids. It is certainly plausible that bees over time could evolve preferences for highly nutritious sources, but there is no evidence that they have. What they seem to have developed is the habit of exploiting multiple sources. 

It would be fairly rare for pollinators to be in a single source environment, prior to the advent of agriculture. Hence, there are not very many examples of single plant/single pollinator symbioses, while there are countless examples of generalist pollinators which can exploit a range of generalist flora, some of which is pollinated both by the wind and animals. Not to mention plants that are pollinated in water, or via liquid exudates on the plant itself. In the final analysis, nature has multiple solutions to the basic needs. 

PLB

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