The promiscuity of honey bee queens generates lots of interesting questions about social insect society, many of which relate to the many different ‘sub-families’ that co-exist within a colony. For example, do individuals within a colony overcome their self-interest to rear the ‘best’ replacement queen in an emergency or do they try to pick their closest relative? Just how far does social co-operation extend? Emerging recent research is starting to suggest that, apart from picking well-fed larvae of the optimum age, workers tend to select larvae from particular ‘royal’ sub-families. If that turns out to be true, we may well have some of our ideas about honey bee queens wrong.
Most of our contemporary ideas about the ‘families’ in a honey bee colony stem from studying the genetics of individuals in the colony. The workers in the hive are all sisters, daughters of one queen ‘mother’, but they have many fathers, depending on which particular sperm fertilised the egg they hatched from. Usefully, the lengths of inherited genetic material we call genes contain non-functioning stretches of repetitive elements that we can look at easily. These are known as ‘microsatellite’ markers, and because they don’t code (for proteins) chance changes in these areas don’t affect protein coding and can accumulate, providing a record of change and relationship we can read. Typically researchers amplify the sections of DNA they are interested in using PCR, at the same time tagging the microsatellites with fluorescent markers. As the repeated sequences have different lengths and masses these can then be seen using (for example) chromatography. Researchers will choose a number of microsatellite markers that are relevant to whatever they are studying, say 3 – 8 different ones, and then group individuals that share common sets of markers.
People looking at this sort of thing will collect lots of workers, analyse the microsatellite markers, and work out the number of different drones there must have been in order to produce the number of different families of worker they have. They have shown that, for a considerable period (many months), the composition of the families remains much the same, suggesting that drone semen is pretty well mixed after mating and used randomly. Over the long term however (up to 4 years) the make-up of the sub-families do change, possibly a consequence of the filling sequence and changing sperm density in the spermatheca, and maybe evidence of ‘cryptic female choice’ or sperm competition in honey bee queens.
Lately, some studies have begun to include queens in the microsatellite analysis, and discovered sets of families that are unique to queens and do not appear if you just examine worker offspring. These ‘extra’ families suggest that queens actually mate with more drones that we thought, rather than 10 – 20 being a ‘normal’ number, 20 – 40 might be more accurate, and actually more in line with that reported for other honey bee species. These ‘royal’ sub-families appear to be quite rare, and stay that way, despite the apparent advantage natural selection would give them if they are more attractive to queen-rearing nurses. That’s likely to be because emergency queen rearing is a relatively rare event so workers seldom get a chance to exercise any preference, and because there are other factors that determine the result in any case. Nevertheless several studies suggest that, in the case of queens raised in an emergency, the choice of which larvae to pick is biased towards particular ‘royal’ subfamilies rather than towards the workers’ own subfamilies.
Withrow JM, Tarpy DR (2018) Cryptic "royal" subfamilies in honey bee (Apis mellifera) colonies. PLoS ONE 13(7): e0199124. https://doi.org/10.1371/journal.pone.0199124
Moritz RFA, Lattorff HMG, Neumann P, Kraus FB, Radloff SE, Hepburn HR. (2005) Rare royal families in honeybees, Apis mellifera. Naturwissenschaften. 2005; 92:488±91. https://doi.org/10.1007/s00114-005-0025-6 PMID: 16151795
Brodschneider, R., Arnold, G., Hrassnigg, N., and Crailsheim, K. (2012) Does Patriline Composition Change over a Honey Bee Queen's Lifetime? Insects 2012, 3, 857-869; doi:10.3390/insects3030857 ISSN 2075-4450