In the Social Insect Behavior Lab, we’re interested in how
individual interactions produce colony behavior. In nature, social insect colonies
are confronted with situations that require unequivocal colony-level action.
For example, in an earlier blog post I described the honeybee method of nest
relocation, which requires the coordinated action of all individual
members of a colony. Honeybees have
evolved a rather ingenious mechanism to evaluate multiple potential nest
sites simultaneously, and choose the best one. Interestingly, smart
group-level decisions can be made even when each individual bee only
views one of many options. Behavioral rules governing individual interactions
ensures recruitment rate to a nest site is a function of site value, and the critical quorum is reached at the best site first.
Single organisms behave based on information gathered by
sensory organs. Millions of bits of environmental information (gathered by
photoreceptors, chemoreceptors, and other sensory cells) must then be
interpreted to inform behavior. Animals aren’t consciously considering
individual photons or microscopic chemical gradients when they behave, but
their behavior is indeed reliant on these tiny fluctuations. Where’s the
disconnect? How is the information coded so that it's useable for the animal?
Similar to the conundrum above, social insects must
integrate the sensory experiences of hundreds or thousands of individual
workers to behave appropriately. Inspired by this idea, we are now developing
a project monitoring colony decision-making. This study will involve an entirely
new organism that was shipped overnight to the lab in an insulated styrofoam
cube: turtle ants!
This project is in collaboration with Dr. Scott Powell at George Washington University, who collected our colony in the Florida keys, and shipped it all the way from Washington, DC. He and his lab members study turtle ants and other ant species through community ecology and evolutionary biology, focusing on how species traits evolve and mediate community structure. Read more about his research from his lab page.
This project is in collaboration with Dr. Scott Powell at George Washington University, who collected our colony in the Florida keys, and shipped it all the way from Washington, DC. He and his lab members study turtle ants and other ant species through community ecology and evolutionary biology, focusing on how species traits evolve and mediate community structure. Read more about his research from his lab page.
Cephalotes varians is
a species of turtle ant found in Florida mangrove forests. At this stage in the project, the colony-level behavior we’re
primarily concerned with is nesting. In the wild, turtle ant colonies occupy
hollow cavities in trees, typically distributing members of a single colony amongst
multiple cavities.
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| A bamboo segment serves as a cozy nest cavity for our newest colony |
A key principle of turtle ant ecology is that they do not
create or build their nest chambers. Rather, they must explore their
environment to find suitable hollows. Similar to the problem faced by
honeybees, turtle ants in search of new nests may face multiple viable options. How do they decide amongst options? Do they always
choose the best nests?
In the lab, we can present candidate nests of varying
qualities to the ants. Our observations of their behavior can then yield a
suite of useful information: What nest qualities do the ants prefer? Can they
effectively choose between two or more candidate nests? How is the rate of
decision-making influenced by candidate nest quality?
Experiments will first focus on colony behavior but
eventually we’d like to dig down to see how individual ant
interactions actually catalyze the decision-making. From there, we can
distill the mechanical basis of the process: what local sensory information are
the individual workers gathering and how is this information used to produce
global colony behavior?
That’s the idea, and we’re excited about what this particular organism has to say about it. Stay tuned for updates on the project!
Further Reading:
Many labs across the country focus on the collective behavior of ants. Here I'll discuss a few who have influenced my own interest in the subject including work by Dr. Stephen Pratt at Arizona State University, Dr. Deborah Gordon at Stanford University and Dr. James Traniello at Boston University.
The Pratt Lab has published on the nesting behavior of Temnothorax ants which are similar to our turtle ants in that they occupy multiple acquired nests. Studying how individual interactions produce collective behavior, he and his graduate and postdoctoral researchers address how intelligent decisions arise even when individual behaviors vary to the point of 'irrationality', garnering write-ups in popular science articles.
The Traniello Lab at BU focuses on the role of caste and polymorphism in the collective behavior of ants, exploring topics like task specialization and how workers shift their behaviors predictably over time. Genera such as Atta, Acromyrmex, and Pheidole contain multiple poignant examples of the relationship between polymorphism and polyethism, where smaller 'minor' workers perform distinct tasks relative to the larger 'major' workers.
Alternatively, Deborah Gordon de-emphasizes 'division of labor' and instead focuses on the distributed qualities of colony behavior. Where Traniello focuses on specialization, Gordon focuses on generalization and pluripotentiality: that any worker can perform a great array of behaviors when placed in a given context. In the genus Pogonomyrmex, workers are effectively equally equipped, meaning polymorphism and task specialization isn't a satisfying explanation for their decision-making ability and their ecological success. A review by Gordon provides a useful description of collective behavior in ants and evaluates the different approaches biologists have taken to describe collective behavior.
That’s the idea, and we’re excited about what this particular organism has to say about it. Stay tuned for updates on the project!
Further Reading:
Many labs across the country focus on the collective behavior of ants. Here I'll discuss a few who have influenced my own interest in the subject including work by Dr. Stephen Pratt at Arizona State University, Dr. Deborah Gordon at Stanford University and Dr. James Traniello at Boston University.
The Pratt Lab has published on the nesting behavior of Temnothorax ants which are similar to our turtle ants in that they occupy multiple acquired nests. Studying how individual interactions produce collective behavior, he and his graduate and postdoctoral researchers address how intelligent decisions arise even when individual behaviors vary to the point of 'irrationality', garnering write-ups in popular science articles.
The Traniello Lab at BU focuses on the role of caste and polymorphism in the collective behavior of ants, exploring topics like task specialization and how workers shift their behaviors predictably over time. Genera such as Atta, Acromyrmex, and Pheidole contain multiple poignant examples of the relationship between polymorphism and polyethism, where smaller 'minor' workers perform distinct tasks relative to the larger 'major' workers.
Alternatively, Deborah Gordon de-emphasizes 'division of labor' and instead focuses on the distributed qualities of colony behavior. Where Traniello focuses on specialization, Gordon focuses on generalization and pluripotentiality: that any worker can perform a great array of behaviors when placed in a given context. In the genus Pogonomyrmex, workers are effectively equally equipped, meaning polymorphism and task specialization isn't a satisfying explanation for their decision-making ability and their ecological success. A review by Gordon provides a useful description of collective behavior in ants and evaluates the different approaches biologists have taken to describe collective behavior.
Powell, S., & Dornhaus, A. (2013). Soldier-based defences dynamically track resource availability and quality in ants. Animal Behaviour, 85(1), 157–164. http://doi.org/10.1016/j.anbehav.2012.10.020
Pratt, S. C., Sumpter, D. J. T., Mallon, E. B., & Franks, N. R. (2005). An agent-based model of collective nest choice by the ant Temnothorax albipennis. Animal Behaviour, 70(5), 1023–1036. http://doi.org/10.1016/j.anbehav.2005.01.022
Muscedere, M. L., Berglund, J. L., & Traniello, J. F. A. (2010). Polymorphism and Division of Labor During Foraging Cycles in the Leaf-cutting Ant Acromyrmex octospinosus (Formicidae; Attini). Journal of Insect Behavior, 24(2), 94–105. http://doi.org/10.1007/s10905-010-9239-3
Gordon, D. M. (2015). From division of labor to the collective behavior of social insects. Behavioral Ecology and Sociobiology, 1–8. http://doi.org/10.1007/s00265-015-2045-3