Bumblebees can detect floral humidity.

Heather M Whitney,Sean A Rands,Natalie Hempel De Ibarra,Henry D Knowles,Michael J M Harrap

doi:10.1242/jeb.240861

Heather M Whitney, Sean A Rands + Show 3 more

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https://doi.org/10.1242/jeb.240861

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Abstract

ABSTRACTFloral humidity, a region of elevated humidity in the headspace of the flower, occurs in many plant species and may add to their multimodal floral displays. So far, the ability to detect and respond to floral humidity cues has been only established for hawkmoths when they locate and extract nectar while hovering in front of some moth-pollinated flowers. To test whether floral humidity can be used by other more widespread generalist pollinators, we designed artificial flowers that presented biologically relevant levels of humidity similar to those shown by flowering plants. Bumblebees showed a spontaneous preference for flowers that produced higher floral humidity. Furthermore, learning experiments showed that bumblebees are able to use differences in floral humidity to distinguish between rewarding and non-rewarding flowers. Our results indicate that bumblebees are sensitive to different levels of floral humidity. In this way floral humidity can add to the information provided by flowers and could impact pollinator behaviour more significantly than previously thought.

Highlights

Floral humidity, an area of elevated humidity within the headspace of the flower, has been demonstrated to occur in a number of flower species (Corbet et al, 1979; Nordström et al, 2017; von Arx et al, 2012)
We investigated the capacity of bumblebees Bombus terrestris to detect and respond to artificial flowers producing floral humidity at levels comparable to the floral humidity detected in real flowers
In an all-rewarding array with artificial flowers that offered low and high floral humidity cues, bumblebees showed an unlearned preference for flowers with elevated floral humidity (Fig. 5)

Summary

Introduction

An area of elevated humidity within the headspace of the flower, has been demonstrated to occur in a number of flower species (Corbet et al, 1979; Nordström et al, 2017; von Arx et al, 2012). Floral humidity occurs widely and varies between species (Harrap et al, 2020a) and does not appear to be limited to species visited by a particular group of pollinators (Harrap et al, 2020a): elevated floral humidity intensity has been observed in flowers pollinated primarily by moths (von Arx et al, 2012), flies (Nordström et al, 2017) and bees (Corbet et al, 1979)

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