Microbes make the meal: oligolectic bees require microbes within their host pollen to thrive. (12th August 2020)

• Record Type: Journal Article
• Authors: Dharampal, Prarthana S.; Hetherington, Matthew C.; Steffan, Shawn A.
• Is Part Of: Ecological entomology. Volume 45:Number 6(2020)
• Page Start: 1418
• Page End: 1427
• Publication Date: 2020-08-12
• Subjects: Bee fitness components -- exosymbionts -- microbes -- oligolectic solitary bees -- pollen specialization -- symbiosis; Insects -- Ecology -- Periodicals; Entomology -- Periodicals; 595.7
• DOI: 10.1111/een.12926
• Languages: English
• ISSNs: 0307-6946

Abstract

Abstract : 1. For solitary bees that specialise on select pollen types (oligoleges), larval development depends on the availability of forage pollen from appropriate host plants and the naturally occurring microbiota present therein. While access to host pollen may be critical for the development of oligolectic bees, the extent to which pollen microbiota contribute to their brood success is unknown. 2. To investigate, we used a diet manipulation experiment to rear larvae of the oligolege, Osmia ribifloris, under in‐vitro conditions. Larvae were reared either on host pollen provisioned by their mother or on non‐host pollen collected by honey bees, in the presence or absence of the respective pollen‐associated microbiota. We assessed impacts on components of larval fitness: developmental time, biomass, and survivorship. 3. Our results revealed a significant interaction between pollen type and pollen‐associated microbes. The relative effect of microbes on larval performance was substantially greater than that of pollen type. Host pollen substrate produced the fittest larvae but only when combined with its full complement of naturally occurring microbiota. In contrast, host pollen without microbes resulted in a marked decline in fitness components. Larvae consuming non‐host pollen showed intermediate fitness, regardless of whether microbes were present or not. 4. These findings imply that the microbiota associated with maternally provisioned host pollen perform critical functions in larval nutrition and survival. For oligoleges in particular, the ability to develop on poorer quality host pollen likely derives from this sustained symbiosis with their microbial exosymbionts, rather than the biochemical characteristics of pollen type alone. Abstract : Exosymbiotic microbes associated with the host pollen provisions of oligolectic bees are critical determinants of brood success, their importance far exceeding that of pollen type. When accompanied with its natural microbiota, host pollen supports quicker development, higher biomass, and greater survivorship among oligolectic larvae. Conversely, sterile host pollen causes dramatic declines in fitness components. For oligolectic bees, the ability to exploit low‐nutrient pollen substrates likely derives from a sustained partnership with their microbial exosymbionts, rather than the biochemical characteristics of pollen type alone.