Yeasts in nectar of an early‐blooming herb: sought by bumble bees, detrimental to plant fecundity

Abstract

Through their effects on physicochemical features of floral nectar, nectar‐dwelling yeasts can alter pollinator behavior, but the effect of such changes on pollination success and plant reproduction is unknown. We present results of experiments testing the effects of nectar yeasts on foraging patterns of captive and free‐ranging bumble bees, and also on pollination success and fecundity of the early‐blooming, bumble bee‐pollinated Helleborus foetidus (Ranunculaceae). Under controlled experimental conditions, inexperienced Bombus terrestris workers responded positively to the presence of yeasts in artificial sugar solutions mimicking floral nectar by visiting proportionally more yeast‐containing artificial flowers. Free‐ranging bumble bees also preferred yeast‐containing nectar in the field. Experiments conducted in two different years consistently showed that natural and artificial nectars containing yeasts were more thoroughly removed than nectars without yeasts. Experimental yeast inoculation of the nectar of H. foetidus flowers was significantly associated with reductions in number of pollen tubes in the style, fruit set, seed set, and mass of individual seeds produced. These results provide the first direct evidence to date that nectar yeasts can modify pollinator foraging patterns, pollination success, and the quantity and quality of seeds produced by insect‐pollinated plants.

New perspectives in nectar evolution and ecology: simple alimentary reward or a complex multiorganism interaction?

“…The extent to which this may alter the behavior of foraging animals, and in turn plant reproduction and fitness, has not yet been assessed. Herrera et al [70] demonstrated that bumblebees can detect yeasts in artificial nectar and respond positively by preferentially visiting yeast-containing flowers and spending more time for each visit. This preference is harmful for the reproduction of Helleborus foetidus, probably because longer visits to yeast-containing flowers promote autogamy and therefore have a negative effect on seed production.…”

Nectar thieves influence reproductive fitness by altering behaviour of nectar robbers and legitimate pollinators in Corydalis ambigua (Fumariaceae)

“…A change in nectarrobbing behaviour of an individual bumblebee can be perceived quite quickly by the other bumblebees (Leadbeater & Chittka 2008). It is also possible that differences in bacterial or yeast communities that develop from visits by robbers and thieves could influence each other's patterns of visitation (Herrera, Pozo & Medrano 2013;Vannette, Gauthier & Fukami 2013). Further research on insect behavioural ecology may provide more insights into this phenomenon.…”

The presence of aggressive ants is associated with fewer insect visits to and altered microbe communities in coffee flowers

“…Microbial growth can depend on nectar sugar concentration and composition-which determines water activity-and the concentration of secondary compounds , including caffeine, which is found in coffee nectar. In addition to the utility of microbial communities for testing ecological theory (Srivastava et al 2004), nectar-inhabiting microbial communities can also differentially influence plant-pollinator interactions (Herrera, Pozo, & Medrano 2013;Vannette, Gauthier, Fukami 2013;Schaeffer & Irwin 2014), depending on their composition. As a result, characterizing taxonomic contribution and species interactions that contribute to variation in composition may be ecologically important in some cases.…”