Peter Oxley

PhD student

Peter.Oxley@usyd.edu.au

The genetics of behaviour in honeybees.

My PhD is focussing on behavioural genetics in honeybees, looking at how variations in specific genes influence hygienic and anarchistic behaviour.

Hygienic behaviour is the genetically-determined tendency of some worker honeybees to detect and remove dead brood. Hygienic bees remove virtually all dead brood in 24 hours, whereas non-hygienic bees tend to recap dead brood. Beekeepers are motivated to select for hygienic behaviour as it confers disease and parasite resistance, but only 20% of Australian bee stocks show hygienic behaviour.

During the 1990s Oldroyd’s lab created a backcross between a hygienic line and a non-hygienic line to produce ca. 68 colonies that showed varying (and repeatable) degrees of hygiene. Based on the fathers of the colonies a high-density linkage map was created using RAPD markers. QTLs were then identified using interval mapping to find markers potentially associated with the hygienic trait. Seven such markers were identified. Oldroyd then scored the two markers that were most likely to be linked to a QTL in unrelated colonies on two continents. This study confirmed that these two markers are statistically associated with hygienic behaviour. Recent reanalysis of the QTL data using more up-to-date models shows that the other markers reported by Lapidge et al. are probably false positives, while simultaneously revealing two further potential loci.

In order to identify candidate genes for hygienic behaviour, I have set up a backcross experiment. A hybrid queen was artificially inseminated with semen from a hygienic drone, so all her daughters vary as to the number of hygienic alleles, and therefore to the degree of hygienic behaviour displayed. One thousand of these daughters were individually tagged and placed in an observation hive, where freeze killed brood was inserted to elicit the appropriate behaviour. After a week of recording their behaviour, all the bees were collected and are being prepared for genotyping. Analysis of 500 microsatellite markers across the honeybee genome will allow me to see which genetic loci correspond to the recorded behaviour, and the degree to which each QTL influences the trait.

Anarchistic behaviour is the genetic tendency of usually sterile workers to activate their ovaries and start laying eggs in a queenright colony. Although a usually rare trait, Oldroyd has successfully bred a line of bees in which most of the workers in the colony have activated ovaries and engage in egg-laying behaviour. Anarchy therefore has given us an unprecedented opportunity to deconstruct the genetics behind social cohesiveness, allowing the possibility of identifying a ‘gene for altruism’.

I will attempt to identify this gene using the same techniques employed for hygienic behaviour. Using the anarchistic line of bees, a backcross line was established, and 200 workers scored for their degree of ovary activation. These workers were also genotyped using 500 microsatellite markers, and are currently being analysed to identify the QTL.