Natasha J' Mehdiabadi

1
Ants as a Model System for the Study of
Behavioral Ecology

• Natasha J. Mehdiabadi
• Section of Integrative Biology Brackenridge
  Field Lab
• University of Texas at Austin

2

• ANTS
• make up gt75 of total insect biomass (along with
  bees, wasps, termites)
• In Amazonian rainforest, 1 hectare of soil
  contains gt8 million ants!
• make up 10-15 of the entire animal biomass in
  most terrestrial environments

3
Ant Colony Members
Reproductive caste - queen(s)
Non-reproductuve caste - workers
Short-lived males
4
Tasks
Foraging Brood Care Nest Construction

• Task allocation - process that adjusts the
  numbers of workers engaged in each task.

5
What cues contribute to an individuals decision
about what task to perform?

• Internal cues
• physiology of individual
• External cues
• state of the environment
• Interaction with others (encounters)

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Encounters
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Task Allocation Conclusions

• Probability that a harvester ant performed a
  certain task was related to encounters.
• Encounter rates may enable ants to respond to
  changes in worker numbers even though ants cannot
  count or assess total numbers of ants engaged in
  a task.

8
Fire Ants
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Phorid fly parasitoid attacking red imported fire
ant workers
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National Distribution Map
Source USDA
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Red imported fire ant(Solenopsis invicta)

• Photo by Kenneth Ross

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Phorid Fly Parasitoids
Pseudacteon tricuspis
Pseudacteon curvatus
Pseudacteon obtusus
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Native fire ant (Solenopsis geminata ) response
to native phorid fly (Pseudacteon browni)
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Blue cheese ant(Forelius mccooki)
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Questions

• 1) Does parasitism by Pseudacteon tricuspis
  affect colony fitness of S. invicta?
• 2) Does P. tricuspis influence worker caste
  ratios of red imported fire ant colonies?
• 3) Does the presence of P. tricuspis alter task
  allocation of S. invicta?

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Colony Fitness

• DIRECTLY measured by biomass of reproductives and
  brood
• INDIRECTLY measured by biomass of workers

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Colony Fitness Methods

• 12 field colonies 48 lab sub-colonies
• 4 treatments
• 1. control
• 2. w/ phorids
• 3. w/ competition
• 4. w/ phorids, w/ competition

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Experimental Set-up
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• Colony Fitness
• Conclusions
• Phorid flies have the potential to control
  imported fire ant populations.

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Fungus-growing Ants
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4 Players of Ancient Symbiosis

• Ants
• Fungus
• Garden pathogen, Escovopsis
• Antibiotic-producing bacteria

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Proposed Questions

• 1.) Is cultivar preference inborn or learned in
  fungus-growing ants?
• 2.) Do these ants suffer fitness consequences by
  cultivating a new fungus rather than their
  original host fungus?
• 3.) Is there a quantitative difference in the
  actinomycete bacterium present on workers,
  depending on the fungus cultivated?

23
Science Fair/Classroom Experiments

• Food preference
• Food quality (25 vs. 50 vs. 75 sugar water)
• Recruitment to food source - food coloring
• Queen Pheromone
• Coverslip with queen smell vs. Coverslip with
  worker smell vs. control
• Forelius mccooki ideal species
• http//www.utexas.edu/research/bfl/antworkshops/

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Photos provided by

• Sharon Bramblett
• Cameron Currie
• Gwen Gage
• Larry Gilbert
• Ulrich Mueller