Bees' intestines harbor a very extensive range of microorganisms. The microbial composition changes during the season. These changes have been identified quite reliably. The differences in microbial composition of bee colonies worldwide is not so great.
That varied pollen has a positive influence on the health of bee colonies can be linked to the fact these pollens contain a range of nutrients. Variety in the composition of the food also results in a variety of microorganisms in the bees' intestines. One-sided nutrition results in decreased microbial diversity.
It is not known how the diversity of pollen influences the bee system and the associated microorganisms. However, some data is available regarding which types of pollen are responsible for which changes in the behavior of the bees. From beekeeping practice and publications, we know that a range of plants/pollen types are known to have certain marked effects on bees and bee colonies. Foraging on heather, for example, results in a reduction in the size of bee colonies. We know that heather pollen contains significantly more of certain minerals than other species of pollen. Furthermore, there are clear indications that the non-occurrence of the Varroa mite in Australia is related to the higher iron content of the pollen from the commonly occurring in Australia Eucalyptus punctata. Click here for the table with pollen mineral contents. Such unambiguous effects have also been reported for amino acids, proteins and vitamins. We should note here that when administering pollen this always concerns a combination of nutrients. In these cases, the likelihood is great that the effect is caused by another component than that assumed.