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'.

Keywords: nectar chemistry; nectar microbe; plant-pollinator; pollinator health.

Figure 1.

Potential mechanisms by which nectar microbes could affect pollinator health. In this review, the following mechanisms are considered: (i) microbe–microbe interactions in the nectar environment, (ii) microbial impacts on nectar nutritional quality, and (iii) microbial impacts on cues important for pollinator foraging. Figure created with BioRender.com. (Online version in colour.)

Figure 2.

Floral visitor diversity and the nectar microbiome. (a) Common, effective pollinators typically include members of the insect orders Hymenoptera and Lepidoptera, as well as nectarivorous birds and bats. (b) Lesser-studied pollinators include non-flying mammals, reptiles and beetles. (c) Nectar thieves, including (d) thrips, can vector microbes that can then affect pollinator foraging. (e) Nectar robbers can have similar effects. Figure created with BioRender.com. (Online version in colour.)