Increased response to sequential infections of honeybee, Apis mellifera scutellata, colonies by socially parasitic Cape honeybee, A. m. capensis, workers

Peter Neumann,Christian W W Pirk

doi:10.1038/s41598-019-43920-1

Abstract

Cape honeybee, Apis mellifera capensis, workers can be social parasites and host colonies can defend themselves by rejection of such workers. Using the pseudo-clonal obligate parasitic lineage of A. m. capensis and wild-type A. m. capensis workers, which are facultative parasites, we show that host colonies significantly increase their defence behaviour towards social parasites upon secondary exposure. Most obligate and facultative social parasites were rejected before they could even produce significant amounts of the queen-like mandibular gland pheromone secretion or activate their ovaries. This suggests that other signals, like cuticular hydrocarbons, could be used by host colonies to identify potential invaders. Honeybee colonies seem to be able to utilise these potential cues, learn from their initial exposure to hive intruders and enable them to improve their defensive behaviour during subsequent infestations, resulting in increased removal rates of parasites.

Highlights

Cape honeybee, Apis mellifera capensis Eschscholtz, workers can be social parasites in colonies of their own and other subspecies, such as the neighbouring one, Apis mellifera scutellata Lepeletier[1,2,3,4,5,6,7,8]
As there is high genetic variance for reproductive dominance in A. m. capensis[9,13] selection for the most dominant socially parasitic worker genotype is favoured within the A. m. scutellata host population
By comparing the increase in the average daily mortality from the first to the second round of infections it was revealed that the pseudo-clonal group increased from an average mortality of 19.7% to 39.4% (z = 4.31, p < 0.0001) during the second infestation, the A. m. scutellata control group increased from 13.8% average daily mortality to 21.3% (z = 1.66, n.s.) and the non-clonal parasitic group from 16.8% to 31.4% (z = 3.38, p < 0.001)

Summary

Introduction

Apis mellifera capensis Eschscholtz, workers can be social parasites in colonies of their own and other subspecies, such as the neighbouring one, Apis mellifera scutellata Lepeletier[1,2,3,4,5,6,7,8]. Scutellata bear the genetic signature of a clone founded by a single ancestral worker genotype[11,14,15]. Despite this “capensis calamity”[12], A. m. Previous studies on parasite infection have shown that honeybee colonies may eject small hive beetle invaders more quickly after a second exposure[16]. This might be the case for socially parasitic workers and could be adaptive given high chances of multiple infections. If honeybee colonies are able to recognize this lineage we would expect them to remove such parasites more quickly compared to other honeybee lineages and subspecies

Methods

Results

Conclusion