Potential effects of nectar microbes on pollinator health

Abstract

Floral nectar is prone to colonization by nectar-adapted yeasts and bacteria via air-, rain-, and animal-mediated dispersal. Upon colonization, microbes can modify nectar chemical constituents that are plant-provisioned or impart their own through secretion of metabolic by-products or antibiotics into the nectar environment. Such modifications can have consequences for pollinator perception of nectar quality, as microbial metabolism can leave a distinct imprint on olfactory and gustatory cues that inform foraging decisions. Furthermore, direct interactions between pollinators and nectar microbes, as well as consumption of modified nectar, have the potential to affect pollinator health both positively and negatively. Here, we discuss and integrate recent findings from research on plant–microbe–pollinator interactions and their consequences for pollinator health. We then explore future avenues of research that could shed light on the myriad ways in which nectar microbes can affect pollinator health, including the taxonomic diversity of vertebrate and invertebrate pollinators that rely on this reward. This article is part of the theme issue ‘Natural processes influencing pollinator health: from chemistry to landscapes’.

Sweet solutions: nectar chemistry and quality

“…Microbes also use amino acids as a nitrogen source in nectar and change its pH [ 80 , 81 ]. In addition to reducing its nutritional value, microbial metabolism may add new compounds to nectar [ 82 ]. An extreme example is the high ethanol content in fermented yeast-containing nectar consumed by treeshrews in Malaysian rainforests [ 83 ].…”

Natural processes influencing pollinator health

“…Water, usually ignored in the composition of nectar, is also a nutrient, and the water component of nectar is a major factor in its variability but also important for consumers. Phenotypic variation in nectar chemistry is common [ 50 ], and there is increasing evidence for effects of microbial contamination on nectar chemistry [ 51 ].…”

“…Martin et al . [ 51 ] looked beyond the endogenous gut microorganisms of pollinators, and review the potential effects of nectar microbes on pollinator health. Bacteria and yeasts in nectar alter its chemical composition, with negative (e.g.…”

“…This may facilitate the detection of nectar sources for pollinators and may affect pollination services on a landscape scale. Martin et al [51] also argue for more research into the effects of nectar microbes on disease dynamics in pollinators, as these microorganisms could affect floral transmission of pollinator pathogens, or infections within pollinators, for example through the production of antibiotic compounds by floral yeasts.…”

The Floral Microbiome and Its Management in Agroecosystems: A Perspective

“…Flowers harbor a diversity of microbes including archaea, bacteria, fungi, protists, and viruses (Table ). Collectively, the floral microbiome has potential to be an important mediator of plant reproduction. , As such, there is growing interest in taking an expanded, community-level perspective in studying the floral microbiome, not only for the potential to improve disease management but also our understanding of the extended floral phenotype, the role these communities play in pre- and postpollination processes, and the health of beneficial insects that rely on floral rewards. ,, In this perspective, we briefly review the current state of research on floral microbiome assembly and function in agroecosystems, as well as future avenues for research that could advance microbiome management and resulting outcomes for both disease control and insect-mediated ecosystem services. In particular, we strive to note both advances and gaps with respect to major research priorities identified for the management of plant-associated microbiomes in agroecosystems …”