Tag Archives: nestmate discrimination

The Spatial Ecology of the Comanche Harvester Ant

I have successfully presented my dissertation work and am currently finishing up the revisions for the final submission to the University of Texas at Arlington for the PhD degree. I expect the final dissertation to be available from the university library by July 2015.

The title of the dissertation is: The Spatial Ecology of the Comanche Harvester Ant, Pogonomyrmex comanche (Hymenoptera, Formicidae)

Dr. Esther Betran was the chair of my committee (UTA).

Other committee members were:

Dr. Jonathan Campbell (UTA)

Dr. Paul Chippindale (UTA)

Dr. Sophia Passy (UTA)

and Dr. Walter Tschinkel (FSU)

Here is the slide presentation and the notes which are numbered to correspond to the slides. I have included some of the corrections that came out of the discussion with my committee and otherwise have noted where there are other problems which I am addressing in the revision.

The slides:

and the notes:

Half-way through the first round of nestmate discrimination tests

Out of 400 trials for this first experiment with nestmate discrimination, done out of context, there have been 12 aggressive interactions so far — 3%. There are 300 trials left for this experiment.

This low level of aggression may indicate a low level of aggression in this species (also meaning that aggression is not a significant factor structuring the population) or that context matters (either the context of the interaction or the task of the individual ants). Further experiments will address these issues.

I will do a full scoring of the behaviors when this experiment is complete and the videos are coded. Right now I am only recording the level of aggression I observe while making the recordings.

Here is a video of an aggressive encounter between two Comanche harvester ants.

Comanche harvester ants display some aggression.

Behavioral Model for Comanche harvester ant interactions

(I do not know what led to the situation in the photo of the Comanche harvester ant above but obviously there was an aggressive encounter between these two ants and since the one ant is missing her abdomen, I suspect other ants may have been involved. These ants were not near any nest when I took the photo.)

I am working on a behavioral model for interactions between Comanche harvester ants based on the observations I am making. This is part of my evaluation of nestmate discrimination — that is, the idea that ants discriminate nestmates from non-nestmates by being more aggressive towards non-nestmates. These aggressive behaviors in turn may differ in frequency, form, or some other character according to the association between the interacting colonies. This is often thought of in terms of distance between the two colonies- such that, colonies that are close neighbors my elicit less aggression and colonies farther away may elicit more. How to define/detect that distance threshold is a concern.

This is a first, crude model for stimulating thinking about the sensory (both internal and external) inputs and the decisions resulting in an observable behavioral response.

I am already aware that this model is inadequate and in error. For instance, this is not a linear process and gaster pumping or wagging may not always be aggressive. The intent is to stimulate thinking, the production of hypotheses, and a better model. As I begin to analyze the behavioral sequences, I will be developing further models.

Nestmate Discrimination Test/Neighborhood Definition Thoughts

Old Thoughts

Here are some notes on ideas that I had in May 2013 on colony distribution patterns and nestmate discrimination in the Comanche harvester ant (Pogonomyrmex comanche). I have been working on this for a while but am trying to formulate good hypothesis and tests of these hypotheses.

Here are the thoughts:

Nestmate Discrimination Test/Neighborhood Definition?

General Methods: a focal colony interacting with several other colonies which may make up a kind of neighborhood

Colony a (focal colony)

1) control with self (3 – 5 trials each)

field, at nest

container

2) with other colonies (3 -5 trials each), nearest 5 or 10 colonies

field, at nest

container

 

observation in the field and from video

video record and view, check for bias in original observation

identification # for colonies and colony interactions (trials)

identification #/code for each video

list to connect the colony interaction identification # with the video code for the interaction

possible covariates?

distance between colonies, GIS locations

surface temperature

colony activity level

1 – few ants on the nest yard: 1 – 5

2 – moderate: 5 – 20

3 – active: 20+

rate? – movement level: slow, moderate, fast?

area containing colonies

density of colonies

# of colonies

 

possible behavioral sequence

avoid or encounter

encounter – physical contact leads to detection which may end the encounter

or detection may lead to display of aggression

grab antennae, leg; mandible flare; gaster movement

which may lead to an attack/fight

 

Maybe use SWNP site as a comparison?

 

Create a model of behavioral decisions – possible inputs (sensory/information)

how communicated?

 

Effect of NMD on colony spatial pattern?

How might NMD affect colony distribution? Are new/younger colonies more aggressive?

What is the colony distribution pattern?

Can the ants tell near neighbors from far neighbors – do they behave differently, more aggression?

How are ant colonies and populations organized?

How do they respond to one another: individual ants; colonies?

 

Queen/Colony foundation

trying to track new colonies and their survival

Where are the colonies established with respect to other colonies?

Is there an “attraction” to areas with established colonies? (conspecific attraction)

or an avoidance – in other parts of the prairie without conspecifics?

Do these concerns operate at different spatial and decision making levels – queen choice?

perhaps depends on spatial scale?

1) conspecific attraction to general area (good habitat) – so tend to construct nest near other colonies, tend to stay close

2) very locally, away from other nests – space requirements, as colony grows, competition for forage?

If so, queens must discern something in flight or upon landing or both – Is there a way to figure this out? Besides tracking queens which only gives general information? > literature: how to discern  queen habitat preference?

1)  one orientation/preference in flight

2) another one on landing in contact with substrate?

behavioral response switch?

Big Picture: May help us understand how fragmentation affects the persistence of ant populations

So, fragmentation and habitat conversion to human use is known to be problem for many organisms – birds, mammals, plants > relationship to spatial scale?

it may be a problem for insects and ants – or do these smaller organisms operate on such a different spatial scale, that human use has a very different effect?

Why/how does it matter? because ants are nearly ubiquitous in terrestrial habitats and play many significant roles in ecosystems

including as predators and prey and in soil health – processing nutrients, “planting” seeds, turning over soil, facilitating gas and water penetration – better than earthworms since ants are not restricted by soil moisture as earthworms are

Nestmate Discrimination may provide information on how colonies interact

relates to how large are ant populations (how many colonies)

how much space might a population need or use (minimum population size for adequate reproduction)

ecosystem services