Intraspecific variation of scent and its impact on pollinators’ preferences

Abstract Floral scents shape plant–pollinator interactions. Although populations of the same species can vary in their floral scent, little is known about how this variation affects pollinator visitation. In this study, we compare the scents emitted by buzz-pollinated Solanum rostratum (Solanaceae) in two areas of its distribution (Mexico and USA) and investigate how these differences in scent affect pollinator preferences and attraction. We determined the variation of floral volatile compounds using hexane extraction followed by gas chromatography coupled with spectrometry. We also performed a field cage multiple-choice bioassay and a Y-tube behavioural bioassay using Bombus impatiens. We recorded 13 volatile compounds in floral extracts for plants from both ranges that varied qualitative and semi-quantitatively among populations. We found that in the field cage experiment, bumble bees visited plants from the US populations more frequently than plants from Mexican populations. However, bees showed no difference in preference between extracts from Mexican or US flowers. We conclude that although bees show differential visitation to whole plants of different regions, variation in floral extract alone does not translate into differences in preference by B. impatiens. The potential effects of variation in floral scent on the other native bee pollinators remain to be assessed. Floral scents are key in plant-pollinator interactions. These scents can vary even among populations of the same species, which influences pollinator attraction. In this study, we determined the variation in floral scents in a buzz-pollinated Solanum rostratum in two areas of its distribution (Mexico and the USA). Moreover, we investigated how these differences affect pollinator preferences and attraction of Bombus impatiens. Our main finding is that floral scents emitted by S. rostratum plants from the Mexican range differ from the USA distribution range; although we found similar preferences of bumble bees for floral extracts, bumble bees preferred to visit plants from the US populations in a field cage bioassay. These contradictory results can probably be attributed to other signals not evaluated in this study or the extraction method of floral extracts. Future studies are necessary to evaluate the potential effects of variation in floral scent on other native bee pollinators.