Category Archives: Colony Spatial Pattern

This category contains the research conducted on the local distribution and spatial pattern of the Comanche harvester ant (Pogonomyrmex comanche), including some landscape factors which may affect this pattern.

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:

Comanche harvester ant colony location maps

The following are maps of colony locations and abundance/density in my study sites in the Fort Worth Nature Center and Southwest Nature Preserve. You can get an idea of the abundance, density, and location changes.

 

Locations in EP:

 

Colony location in EP, 2009 - 2013

Colony location in EP, 2009 – 2013

Locations in GL:

 

Pogonomyrmex comanche colony locations in the GL of the FWNC, 2010 - 2013

Pogonomyrmex comanche colony locations in the GL of the FWNC, 2010 – 2013

Locations in T1P;

T2P_composite

Locations in T2P:

 

Comanche Harvester Ant Colony Locations in T1P

Comanche Harvester Ant Colony Locations in T1P

Locations in SP

Colony locations in SP from 2011 - 2013

Colony locations in SP from 2011 – 2013

Prelimary Work on the Comanche Harvester Ant Colony Distribution

Here are two posters which summarize preliminary work on the distribution of nests of the Comanche harvester ant  (Pogonomyrmex comanche) in the Fort Worth Nature Center, Fort Worth Texas. The nests were located visually by walking through the habitat and locating nests and following foragers back to nests. Nests were then flagged and GIS coordinates recorded. Environmental variables, geospatial data, and co-occurring ant species (Forelius and Trachymyrmex turrifex) were also evaluated.

I am currently working through 5 years of this kind of data for my final dissertation project. In the  final project, I also have nest locations for a population in the Southwest Nature Preserve in Arlington, Texas.

From 2010: Nest Distribution of the Comanche Harvester Ant

 

From 2012: Tracking the Comanche Harvester Ant

 

Canopy used in shading experiment

Shading Ant Nests Experiment

Background: Several species of Pogonomyrmex ants will alter the exterior nest area (nest yard) or move their nests if the area becomes shaded. Shading may alter the internal nest temperature and thereby effect both the metabolism of workers (how quickly they can become active) and the development of the young (eggs, larvae, and pupae).

The Comanche harvester ant (Pogonomyrmex comanche) nests in prairie characterized by oak motts of various sizes and surrounding oak forest. Comanche colonies do not nest within the oak motts nor the forest and are rarely within 5 meters of the oak forest border. I have observed these ants moving to new nest sites several meters from the original nest site. Carlson and Gentry (1973) found that Pogonomyrmex badius moved their nests in response to shading. I wondered if shading might be a factor determining nest movement for the Comanche harvester ant as well. And thereby, impacting the spatial pattern of colonies within the prairie.

Methods: This experiment was carried out in two areas of Todd Island at the Fort Worth Nature Center and Wildlife Refuge in Fort Worth, Texas, from June through November 2012.

I made canopies of canvas using PVC tubing as a framework and placed these over nests chosen to be shaded. I chose 8 nests to be shaded and 8 nests to be controls, unshaded. I monitored the nests for temperature, movement of the entire colony to a new nesting site, and movement of the entrance.

I measured temperatures 3 times a day at the beginning of each month using a Magellan 600 Explorer GPS unit and a soil thermometer probe. The temperatures measured were: air, surface, 10 cm depth, 20 cm depth, and 30 cm depth. Activity level of the colonies was also observed when the temperature measurements were made.

The canopies measured 40 cm X 40 cm and were placed 20 cm above and centered over the nest entrance. The canvas was attached to the framework using twine. To secure the canopy in place over the nests, wooden rods were placed in the soil and the legs of the framework were placed over these. Canopies were left out for the duration of the experiment.

The data were analyzed with Fisher’s Exact Probability Test and Chi Square Test.

Results: There was no significant effect of the canopies on the frequency of colony nor entrance movement.

Chi Square Results
Phi Yates Pearson
+0.04 0.06 0.23
p values 0.81 0.63
Fisher’s Exact Probability Results   p values
  One-tailed Test 0.41
  Two-tailed Test 0.82

However, there was an impact on colony activity due to the shading during midday and later. The canopies kept the surface temperature low enough for nest maintenance activities to continue through the hotter part of the day. Colonies that were shaded remained active during the hot midday when other colonies were inactive (with no ants on the exterior nest yard). The shaded colonies continued with nest maintenance activities only — mostly bringing soil to the surface. No foraging was taking place for any colony from midday on.

Conclusion: The impact of shading on the internal nest temperatures does not appear to be a significant factor for Pogonomyrmex comanche colony movement. Despite what has been observed for other species in this genus, this is not entirely surprising since 1) Texas is hot and in summer, the soil surface is too hot for the ants to walk on much of the day and 2) these ants nest in prairie associated with oak forests, so most nests are shaded at least part of the day. Field observations indicate that colonies are likely to have different activity periods based on when that colony is shaded.

Literature: Carlson, D. M. and Gentry, J. B. 1973. Effect of shading on the migratory behavior of the Florida harvester ant, Pogonomyrmex badius. Ecology 54: 452-453.

 

 

Comanche Harvester Ant Colonies in the Southwest Nature Preserve, Arlington, Texas

As part of my study of the spatial ecology of the Comanche harvester ant, I have been mapping colony or nest locations over a number of years. Here is the most recent mapping of a population of this ant in the Southwest Nature Preserve, in Arlington, Texas. I have also mapped this population in 2011 and 2012. There has been no significant change in the population size nor in the colony locations.

Comanche harvester ant colonies in the Southwest Nature Preserve, Arlington, Texas.

Comanche harvester ant colonies in the Southwest Nature Preserve, Arlington, Texas.

A Comanche nest at the Fort Worth Nature Center.

Colony Spatial Pattern

(The photo above shows a side view of the crater external nest form of the Comanche harvester ant. — “domed” structure in the center.)

Since 2009. I have mapped the nest locations of the Comanche harvester ant  (Pogonomyrmex comanche)  in four prairies of the Fort Worth  Nature Center, Fort Worth, Texas and one prairie in the Southwest Nature Preserve, Arlington, Texas.

Here are the colony locations for June 2013 including established nests (in green) and the locations of new queens digging nests (in pink).

TI-2_Jn_with legendTI-1 MapEP-1_JN2013_map