‘Beeing’ part of a group:

Group and individual decision-making in honeybees

Katie Wharton

Birds and bees…but mostly the bees

Group decision-making

Flock of Starlings

The honeybee colony’s investment in males (drones)

“The drone is a filthy, gluttonous creature. He is everything that the worker is not.

Like an imposing knight in medieval armor, with his silky antennae, and golden-colored hairs adorning his thorax, he looks more imposing than he is useful.”

- Louis Sutherland, The Life of the Queen Bee

By producing drones, a colony invests in reproduction

Overview

Background:Honeybee colonies regulate their production of drones

Question 1:Does the queen regulate her production of drone eggs?

Question 2:Do the workers regulatethe number of drone larvae they rear?

Conclusions & future directions

Colony size influences reproduction

Season influences reproduction

Spring Summer Fall

Swarming

Workers kick out drones

# d

ron

es in

col

ony

+ food

Seeley & Mikheyev, 2003

Food availability influences reproduction

+ drones - drones

Free & Williams, 1975

Current investment in reproduction influences future reproduction

Colony drone production is influenced by…Colony sizeSeasonFood availabilityDrones present in hive

Drone production is regulated adaptively

From the colony to the individuals Overview

Background:Honeybee colonies regulate their production of drones

Question 1:Does the queen regulate her production of drone eggs?

Question 2:Do the workers regulatethe number of drone larvae they rear?

Conclusions & future directions

Haplodiploidy

Fertilize egg?

yes no

How a bee colony produces a drone

15-20% drone

Does the queen regulate her production of drone eggs?

Predictions:

The queen’s production of drone eggs will depend on how many drone eggs she recently laid

The queen’s production of drone eggs will be NOT be determined only by the number of drone cells available

W

W D

D

Stage 1

Stage 2

Drone egg production decreasedwhen queens recently laid drone eggs

Queens did not recently lay drone eggsQueens recently laiddrone eggs

ns

p<0.05

W D

Overview

Background:Honeybee colonies regulate their production of drones

Question 1:Does the queen regulate her production of drone eggs?

- YES

Question 2:Do the workers regulatethe number of drone larvae they rear?

Conclusions & future directions

Observations: the case of the missing drone brood

When times are “bad,”the workers will destroy drone brood in the colony

Lots of anecdotal accounts…

No experiments!

Do the workers regulate the number of drone larvae they rear?

Predictions:

The workers’ tendency to rear drone larvae will depend on how many drones are already in the colony

The worker’s rearing of drone larvae will NOT be determined only by the presence of drone eggs laid by the queen

D W

D

W

W W

D

W

D D

D

W

Drone brood added

Worker brood added

Survival of immatures:= proportion of eggs that were reared

Calculated for workers and drones

W D

Drone survival was lowerwhen colonies were provided with drone brood

Drone brood removed

Drone brood added

W D

p<0.01ns

Overview

Background:Honeybee colonies regulate their production of drones

Question 1:Does the queen regulate her production of drone eggs?

- YES

Question 2:Do the workers regulatethe number of drone larvae they rear?

- YES

Conclusions & future directions

Conclusions

Honeybee colonies are exceptionally good at regulating drone production

This adaptive regulation arises through an interplay of decisions by individuals in the colony

Conclusions

If the colony already has plenty of drones:

The queen lays fewer drone eggs- She is not constrained by

the comb patterns built by the workers

The workers selectively eliminate immature drones- They are not constrained by

the egg-laying decisions of the queen

How might this be beneficial to the colony?

Multiple stages of flexibility

Additional lines of study

Colony drone production depends on…

Colony sizeSeasonFood availabilityDrone brood present in hive

??

?

Additional lines of study

Annually:200,000 workers2 virgin queens

each queen mates with ~18 males

20,000 drones!

Why do colonies produce so many drones?

The ups…

Thanks for “beeing” there to help!

CommitteeTom Getty, Fred Dyer, Kay Holekamp, Zach Huang

Getty lab membersLindsey Walters, Ben Janse, Eva Lewandowski, Jean Johnson

Dyer lab membersFrank Bartlett, Steph Kortering, Mercedes Ramirez,John Townsend-Mehler, Cindy Wei

Summer field assistantsLora Bramlett, Kim Davis, Mara Trudgen, Andy Taylor, Adam Bates, Liz Dean, Jared Ruddick, Kourtney Trudgen, Megan Wheeler, Michael Hillman, Jenn Lieb, Erin Walaszczyk, Sara Kaltz

MSU Department of ZoologyMSU College of Natural ScienceMSU EEBB programNSF IGERT program in sequential decision-making

Questions?