The Sister Act

This blog post is brought to you by a special guest writer, Kristyn Ing, who’s currently studying Environmental Science at the University of Western Ontario. She recently became fascinated with bees while taking an Animal Behaviour course and marveled at their eusocial behaviour. 

While they may appear to be working together, these sisters could be doin’ it for themselves. 

In our last post, we discussed the epigenetics of bees and how they change roles in the hive, so we’re going to dive a little deeper this time into their genetics and how it affects their reproductive behaviour.

Honeybee societies are often used to explain a well-functioning operation or a network of co-operative components. Yet what most people do not realize is that the queen bee and her workers are in an ongoing evolutionary conflict that is unlikely to end. The conflict between the two parties stems from their reproductive interests being misaligned. Conflict is often seen as an undesired outcome, but if stability were realized, there would be no room for biological and behavioural change.

Just as human parents are equally related to both their offspring by 50%, the same goes for female queen bees, who are 50% related to both their daughters and sons. However, if one were to analyze the relatedness of a worker, who is biologically always female, to either one of their full sisters or brothers, you would notice that they are more related to a sister than a brother by 25%! Hence the name “super-sisters” that has been attributed to full sister honeybees.

How might this be? Queen bees are diploidy, only partially sharing their genome with their offspring. Female honeybees stem from fertilized eggs and require a male to be fertilized. Conversely, male honeybees come from unfertilized eggs and are thus solely related to their mother, the queen. While queen bees are diploidy, male bees are haploid and therefore share 100% of their genetic material with their offspring, creating a haplodiploid interaction for super-sisters. Super-sisters share half, and therefore have 50% of genes from their mutual father (100%/2 = 50%). They also have half of their genes in common from their mother, the queen (50%/2 = 25%), making super-sisters related to each other by a grand total of 75%, leaving their brothers to be only a mere 25% related. This shows that a female worker would be three times more related to her sister (75%) than to her brother (25%). Therefore, it is genetically more favourable to workers for the queen to rear more sisters than brothers.

This may sound absurd and only theoretical, yet it has been well-studied that sisters have manipulated the sex ratio in their favour as they are the workers who tend to the queen’s eggs. Due to the imbalance in relatedness of workers to their sisters versus their brothers, they would preferentially treat eggs destined to be female while destroying those who would be male. Though this would be advantageous to the workers, it would be very detrimental to the queen’s evolutionary fitness, as her future sons are being terminated even though she is equally related to both her sons and daughters. At that moment in evolutionary history, honeybee workers were “winning” this evolutionary battle.

As time passed, queen bees slowly evolved to (unintentionally) realize a solution to this conundrum by mating with multiple males and not remaining monogamous, which had no impact on her relatedness, nor to her personal indirect fitness. This in turn had a tremendous negative effect on her daughters/workers. As workers no longer shared a common father, their relatedness was slowly driven down to a point where they were equally related to their sisters and brothers (25%). Therefore, the worker’s incentive to preferentially rear sisters has been stripped away and has now placed the queen in a “winning” position in this evolutionary conflict she had been having with her daughters.

From eggs to pupae, the bee brood will soon emerge as future workers and drones.

To combat this issue, worker bees are sometimes inclined to try their luck and lay some of their own unfertilized eggs within the group to rear sons of their own, which would result in having their own offspring that are 50% related to themselves, compared to only being 25% related to their siblings. As a result, it is genetically more favourable for workers to have offspring of their own and not solely help raise their siblings. However, this is not beneficial to her sisters and the rest of the worker community as a whole because workers are less related to the offspring of their partial siblings rather than their other siblings. Lone reproduction by a worker is not commonly practiced because due to this imbalance in relatedness*, the individuals who perform this act often get their eggs destroyed by their siblings as it is not genetically favourable for workers to care for those eggs.

Honey bees are often compared to being a well-oiled machine, working together as one, yet in reality, their evolutionary interests remain unresolved and therefore they continue to be in conflict, much like fighting to win the Iron Throne. This goes to show that not only do humans have family feuds, but so do bees!

*One exception to the norm is seen in Cape honeybee workers, which possess a unique reproductive system where they can lay unfertilized eggs to become a queen or a worker bee, thus creating a clone that is genetically identical to them!

Work Hard or Die Trying, Girl

In the age old question “What do you want to be when you grow up?” most people first think of the typical career options, such as doctor, lawyer, principal…or caterpillar. Or perhaps you followed your passion to become a top executive by going to night school and ended up assuming your boss’s identity after you discover they’re trying to steal your idea for a major business deal. 

When it comes to managing a hive, bees don’t have to wear shoulder pads and sport 80’s hairdos to be some of the hardest working girls out there, but they also don’t get to decide that role they take on next and what sort of career they want, despite the number of different jobs available. Before we dive into the different types of bee jobs, let’s talk a bit about the science behind it and how their roles in the hive shift as they age, also referred to as temporal polyethism.

Whether you’re waiting for your admittance letter from Hogwarts or just a tough detective trying to single-handedly save hostages from terrorists during a Christmas party, honeybees on the other hand, are driven by their epigenetics—essentially, the chemical modifications that affect how genes are expressed by being turned on or off. Worker, or house bee, roles are allocated amongst the colony according to their age, increasing their exposure to risk with each task. From the moment the emerge from their cells, bees are put to work by cleaning the cells and live out the last of their days foraging for nectar and pollen. Honeybees are eusocial creatures, meaning that they take part in cooperative care of young, divide labour into reproductive groups and consist of overlapping generations, which results in plenty of open jobs all around for emerging and up-and-coming bees. Although bees only live for about 42 days, they have pretty fruitful and diverse careers. Here’s an overview of their tasks and stages of development.

Housekeeping Bees (Days 1-3)

Just like making your bed after getting up, bees start cleaning and polishing their cell right away after emerging from it. No resource goes to waste in the hive and the cell is prepared to receive a new egg or store nectar and pollen. The newly emerged bee goes on to clean the other cells to be inspected by the queen, and if they are deemed inadequate, the cell will need to be cleaned again.

Undertakers (Days 3-16)

What better way to get valuable career experience than by becoming an undertaker? Bees are little neat freaks and pride themselves on having a clean hive, which is why they spend the second stage of their life cleaning out corpses or any diseased brood, taking them as far away from the hive as possible. This also reduces any potential health threats that can bring disease to the colony. 

bee undertaker
No dead end jobs here for these undertakers.

Nurse Bees (Days 4-12)

No Nurse Nightingales here, but nurse bees tend to the rest of the brood at their various stages of development and check on each individual larva of future worker bees, queens and drones over a thousand times a day for inspection and feeding. In addition to caring for their young, the nurse bees will eat honey with high antibiotic activity, such as sunflower honey, and distribute the “medicine” amongst the colony in the event that a hive is infected with a parasite.  

Queen’s Attendants (Days 7-12)

Since the queen is busy producing up to 2,000 eggs a day, the queen has an entourage of attendants to care for her, feeding and grooming her as she moves around the hive. These ladies-in-waiting also have the important role of spreading the Queen Mandibular Pheromone (QMP) throughout the hive to signal to the rest of the colony that the queen is alive and well.

Pollen Packers and Nectar Collectors (Days 12-18)

These young ladies work closely with the returning forager field bees and help relieve them of the pollen from their heavy baskets. The pollen is placed inside a honeycomb and mixed with a bit of honey to make bee bread, which is fed to the brood. Nectar is also collected from the field bees and deposited into the marked cells in the form of diluted honey.

Builders (Days 12-35)

Once mature enough to secrete and produce beeswax, the house bees put on their figurative hardhats and take up masonry to build new wax comb and capping of ripened honey and pupae cells.

Fun Bee Fact: Thanks to mathematician Thomas Hales, it has been proven that the honeycombs use the least amount of wax compared to rectangles, square or triangles and are therefore the most efficient and practical structures in nature! Isn’t math fun?

Bee Fans and Watergirls (Days 12-18)

When they’re not packing pollen or collecting nectar from the returning field bees, bees rotate through their HVAC duties by ensuring the stability of the humidity and temperature within the hive. The water carriers gather water from a nearby source and bring it back to the hive to be spread on the backs of the fanning bees, thus cooling the hive and increasing the airflow.

Guard Bees (Days 18-21)

Second to foraging in the fields, being on guard duty is perhaps the most risky job for a bee. Like security guards in a building, they verify the identity of every bee entering the hive and occasionally turn a blind eye when they are bribed with nectar from other bees. Armed with only their stingers for one-time use, these brave ladies will die protecting their honey and colony from thieving bees and other intruder insects, such as wasps.

Field Bees (Days 22-42)

It’s the career they’ve all been working towards and admiring from the sidelines until it’s finally orientation day and the bees take their first flight outside the hive to imprint the location of their home. Provided that there are no blockages in front of the hive entrance, bees will buzz around in circles around the hive, progressively increasing the diameter of their orbit to become familiar with the surrounding landmarks that will help guide them back. Field bees will travel within a 4-5 km radius to collect resources, such as water, nectar and pollen, for the hive and live out the rest of their days foraging until their last breath.

forager bees
Field bees returning to the hive laden with pollen.

So what does this mean for humans and how adaptable we are in the types of careers we pursue? There’s something to be said for the level of collaboration and well-orchestrated self-organization that goes on inside a hive. Bees seamlessly transition from one position to another, even reverting back into other roles when needed, showing that no bee is too high up on the totem pole to help out. The contribution of one bee may seem insignificant in the grand scheme of things when you realize a worker bee only makes 0.8 grams of honey in her lifetime, but the efforts of over 550 bees combined can make a pound of honey. No matter what passion you pursue in your career, think about the greater contribution you’re making as a whole to your organization or your community.