Bees eavesdrop upon informative and persistent signal compounds in alarm pheromones.

Zhengwei Wang,James C Nieh,Yufeng Qu,Shihao Dong,Ping Wen,Jianjun Li,Ken Tan

doi:10.1038/srep25693

Abstract

Pollinators such as bees provide a critical ecosystem service that can be impaired by information about predation. We provide the first evidence for olfactory eavesdropping and avoidance of heterospecific alarm signals, alarm pheromones, at food sources in bees. We predicted that foragers could eavesdrop upon heterospecific alarm pheromones, and would detect and avoid conspicuous individual pheromone compounds, defined by abundance and their ability to persist. We show that Apis cerana foragers avoid the distinctive alarm pheromones of A. dorsata and A. mellifera, species that share the same floral resources and predators. We next examined responses to individual alarm pheromone compounds. Apis cerana foragers avoided isopentyl acetate (IPA), which is found in all three species and is the most abundant and volatile of the tested compounds. Interestingly, A. cerana also avoided an odor component, gamma-octanoic lactone (GOL), which is >150-fold less volatile than IPA. Chemical analyses confirmed that GOL is only present in A. dorsata, not in A. cerana. Electroantennogram (EAG) recordings revealed that A. cerana antennae are 10-fold more sensitive to GOL than to other tested compounds. Thus, the eavesdropping strategy is shaped by signal conspicuousness (abundance and commonality) and signal persistence (volatility).

Highlights

The ability of pollinators to detect information about predation has cascading ecosystem effects[21]
Our solid phase microextraction (SPME)-GC-MS analysis provided the first evidence that MB and decen-1-yl acetate (DA) are present in the sting alarm pheromone of A. cerana (Fig. 1B)
Apis cerana should benefit from avoiding its own alarm pheromone and eavesdropping upon heterospecific alarm pheromones to reduce foraging predation risks

Summary

Introduction

The ability of pollinators to detect information about predation has cascading ecosystem effects[21]. The ability of prey to detect and avoid predators plays a major role in structuring ecosystems, in part by altering the spatio-temporal distribution of prey within a landscape[22] It is not known if pollinators can eavesdrop upon alarm signals to avoid predators. Li et al.[23] showed that A. dorsata can eavesdrop upon predator signals by detecting and avoiding the odor trail pheromone of weaver ants. Eavesdroppers could pay attention to odor abundance and to odor components that provide lasting warning information: the least volatile yet conspicuous elements of an alarm pheromone. We predicted that A. cerana foragers would exhibit eavesdropping to A. dorsata and A. mellifera alarm pheromones, and would detect and avoid conspicuous individual compounds, defined both by abundance and by decreased volatility

Methods

Results

Conclusion