To be on the safe site - Ungroomed spots on the bee's body and their importance for pollination.

Laura Koch,Petra Wester,Klaus Lunau,Renee M Borges

doi:10.1371/journal.pone.0182522

Abstract

Flower-visiting bees collect large quantities of pollen to feed their offspring. Pollen deposited in the bees’ transport organs is lost for the flowers’ pollination. It has been hypothesised that specific body areas, bees cannot groom, serve as ‘safe sites’ for pollen transfer between flowers. For the first time, we experimentally demonstrated the position, area and pollen amount of safe sites at the examples of Apis mellifera and Bombus terrestris by combining artificial contamination of the bees’ body with pine or sunflower pollen and the subsequent bees’ incomplete grooming. We found safe sites on the forehead, the dorsal thorax and waist, and on the dorsal and ventral abdomen of the bees. These areas were less groomed by the bees’ legs. The largest amount of pollen was found on the waist, followed by the dorsal areas of thorax and abdomen. At the example of Salvia pratensis, S. officinalis and Borago officinalis, we experimentally demonstrated with fluorescent dye that the flowers’ pollen-sacs and stigma contact identical safe sites. These results confirm that pollen deposition on the bees’ safe sites improves pollen transfer to stigmas of conspecific flowers sti. Future research will demonstrate the importance of safe sites for plant pollination under field conditions.

Highlights

To enable sexual reproduction, plants normally use animals as pollen vectors, with their flowers mostly offering nectar [1]
At the example of Salvia pratensis, S. officinalis and Borago officinalis, we experimentally demonstrated with fluorescent dye that the flowers’ pollen-sacs and stigma contact identical safe sites
Other safe sites were similar to B. terrestris between the thorax and abdomen, mainly the middle area of dorsal abdomen, and only few pollen grains were found on the legs and the ventral side (Fig 1I–1N, S2 Video)

Summary

Introduction

Plants normally use animals as pollen vectors, with their flowers mostly offering nectar [1]. The most important group of pollinators [2,3], visit flowers for nectar, and collect large amounts of pollen mainly to feed their offspring [4,5,6]. As soon as pollen is collected and groomed into the bees’ transport organs, it is mostly lost for the flowers’ pollination [7]. Bees use specific structures (brushes, combs, scrapers) of their legs to groom and collect pollen. Pollen grains are transferred to transport organs which are the crop, the scopae (dense mass of elongated, often branched, birstles)

Methods

Results

Conclusion