To be on the safe site – Ungroomed spots on the bee’s body and their importance for pollination

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.

访花蜜蜂会采集大量花粉以饲喂幼虫。存留在蜜蜂转运器官中的花粉将无法参与植物的授粉过程。有假说提出，蜜蜂无法自行清理的特定身体区域，可作为花粉在花朵间传递的安全位点（safe sites）。本研究首次结合“用松树或向日葵花粉人工沾染蜜蜂躯体，随后观察蜜蜂不完全理毛行为”的实验方法，以西方蜜蜂（Apis mellifera）和地熊蜂（Bombus terrestris）为研究对象，明确了安全位点的位置、分布面积与承载花粉量。研究发现，蜜蜂的额头、背部胸部、腰部以及腹部的背侧与腹侧均存在安全位点。这些区域极少被蜜蜂的足进行清理。其中腰部承载的花粉量最多，其次为胸部与腹部的背侧区域。本研究以草地鼠尾草（Salvia pratensis）、药用鼠尾草（Salvia officinalis）以及琉璃苣（Borago officinalis）为实验对象，通过荧光染色实验证实，这些植物花朵的花粉囊与柱头均可接触到相同的安全位点。上述结果证实，将花粉沉积于蜜蜂的安全位点，可提升花粉向同种植物柱头的传递效率。未来将通过野外实验进一步明确安全位点对植物授粉的重要性。