Tag Archives: Texas

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:

Prairies in a Changing World: State of the Prairie Conference 2014

Conferene poster

The Native Prairies Association of Texas (and the Coastal Prairie Partnership) had their annual meeting in Fort Worth at the Fort Worth Botanical Garden from May 29 – May 31, 2014.  I was invited to present my research on ants in the prairies of the Fort Worth Nature Center in Fort Worth and the Southwest Nature Preserve in Arlington, Texas.

I also attended most of the meeting and gained a lot from the presentations I attended and especially from hobnobbing with other attendees.

**I want to pass on that Native American Seed is producing a seed mix especially to attract native bees which will be available this fall. Here’s the link to this Seed Source.

Here is the agenda for May 30 and May 31, following which I post my notes on the few talks I was able to attend with some comments and finally my presentation and extensive notes on the slides.

May 30 Agenda

State of the Prairie Agenda for May 30

May 31 Agenda

State of the Prairie Agenda for May 31

My Notes and Comments

State of the Prairie Conference Notes

Demonstration Prairie 5

The Demonstration Prairie at the Fort Worth Nature Center (photo above)

I presented my research on the ant species I have found in 17 sites at the Fort Worth Nature Center and what this means for 1) the possibility of using ants as bioindicators and 2) for the ecology of the Cross Timbers Ecoregion.

“Jills of All Trades: Ant Diversity and Flexibility in the Cross Timbers Ecoregion”

Here are my notes. In these notes I include quite a bit more than I was able to cover, in part, so that if you did not attend, you can follow the slides. If you have questions, message me.

Jills of all Trades_Presentation Notes

And finally, I mention a 10 minute digital recording I made of the Comanche harvester ant “remodeling” a ground bee nest that was too close to the ant nest. Here is a the video:

Ant Presence and Abundance in the Fort Worth Nature Center

I sampled ants using pitfall traps in 17 sites in the Fort Worth Nature Center monthly in June, July, and August 2012.

I used CANOCO to run redundancy analyses (RDA) on ant presence with abiotic and biotic environmental variables and on ant presence and abundance with soil type to look for ant preference for soil. I used forward selection of variables and Monte Carlo significance tests to select the variables for the final RDA models.

RESULTS

1) RDA for ant presence and environmental variables

RDA Summary Table

Axes

1

2

3

4

Total variance

 Eigenvalues                     

0.122

0.062

0.026

0.014

1.000

Species-environment correlations

0.820

0.872

0.672

0.582

Cumulative percentage variance of species data

12.2

18.4

21.0

22.4

Cumulative percentage variance of species-environment relation 

51.5

77.6

88.8

94.5

Sum of all eigenvalues     

1.000

Sum of all canonical eigenvalues     

0.237

Triplot

2) RDA for ant presence and soil type

RDA Summary Table

Axes                                    1      2      3      4 Total variance
Eigenvalues

0.076

0.023

0.011

0.007

1.000

Species-environment correlations 

0.788

0.603

0.424

0.417

Cumulative percentage variance    of species data

7.6

9.9

11.0

11.7

Cumulative percentage variance    of species-environment relation 65.2   84.9   93.8 100.0
Sum of all eigenvalues

1.000

Sum of all canonical eigenvalues

0.117

Triplot

3) RDA for ant abundance and soil type

RDA Summary Table

Axes                                    1      2      3      4 Total variance
Eigenvalues

0.070

0.031

0.016

0.003

1.000

Species-environment correlations 

0.777

0.655

0.456

0.265

Cumulative percentage variance    of species data

7.0

10.1

11.7

12.0

Cumulative percentage variance    of species-environment relation

58.4

84.6

97.9

100.0

Sum of all eigenvalues

1.000

Sum of all canonical eigenvalues

0.120

Triplot

24% of species presence is explained by the environmental variables with percent litter cover and drainage being the significant variables. Sampling sites by date clumped together indicating a lack of seasonality — which seems a bit unusual since late July and August become quite hot and ant activity seems reduced  at this time.

12% of species presence was explained by soil type with the Aquilla soil being the only significant soil. This soil is the only soil type where the Comanche harvester ant (Pogonomyrmex comanche) is found. All other species are more generalist with respect to soil type.

7.4% of species abundance was explained by soil type again with the Aquilla soil being the only significant soil. This result further supports the result with species presence: only the Comanche harvester ant has such narrow soil preference.

CONCLUSIONS

Though the eigenvalues are low this is not unusual for ecological data. The low level of explanatory value of these variables is likely due to the generalist nature of these species (and more temperate species in general) and the below-ground nesting of most ant species.

The Comanche harvester ant (Pogonomyrmex comanche) was the only species to show strict preference for soil type. Exactly what this species’ preference or requirement is remains unresolved.

Ants on Baits at the Fort Worth Nature Center

This is the demonstration prairie located in front of the Hardwicke Interpretative Center of the Fort Worth Nature Center in Fort Worth, Texas. The students set up some bait stations in this area.

This is the demonstration prairie located in front of the Hardwicke Interpretative Center of the Fort Worth Nature Center in Fort Worth, Texas. The students set up some bait stations in this area.

On April 29, 2014, sixth graders from Trinity Valley School (Ms. Julie Frey) in Fort Worth, Texas came to the Fort Worth Nature Center to learn about horned lizards and the ants they eat, mostly Pogonomyrmex ants, commonly called harvester ants because they mostly eat seeds. As part of their time with me, we set up tuna and pecan sandies cookie baits and made observations. At the conclusion, the students collected the ants for identification. I also recorded some video of the ants.

Although we attempted to set this up as a controlled study, it was a good preliminary investigation. The students explored their areas — limestone ridge, woods, or open prairie — and tried alternative ways of placing and using the baits. They did a good job of investigating.

I set them up with a data sheet to record location, weather, type of bait (tuna, cookie, or both), time of first arrival to the bait (and what this was), time for first ant arrival, observations (numbers of ants; rate of foraging, interactions, etc.), and how many ants on the baits after 5 minutes. (I did not get the data sheets so I cannot share that part.)

I recommend this kind of exercise for teaching about science method, forming hypotheses, investigating insects and foraging. It is easy to do and can be done anywhere. You can develop all kinds of ideas and possible experiments from this kind of work — myrmecologists do so all the time.

Here is a summary of the ants the students collected and some short clips from the video.

METHODS for Identification:

The students collected the ants from the baits and put the ants and bait into jars. In the Formanowicz lab at the University of Texas-Arlington, I separated the ants from the baits, rinsed them and placed them in 95% ethanol. They were identified to species using various on-line and published identification keys.

The lab bench: using a Nikon dissecting microscope with 40X magnification.

Lab bench for ant identification

Lab bench for ant identification

Sorting the ants from the baits

Sorting ants collected on tuna bait

Sorting ants collected on tuna bait

Some photos of the ants: Photos were taken using a dissecting microscope at 40X with a cell phone.

Camponotus americanus: This is a carpenter ant that nests in wood and is mostly found in woodland though they may wander into prairie. These ants are large, 1.5 cm.

Camponotus americanus collected from baits at the Fort Worth Nature Center.

Camponotus americanus collected from baits at the Fort Worth Nature Center.

Crematogaster sp.: Crematogaster is called an acrobatic ant because their gaster (part of the abdomen) is attached such that the ants can carry it above their heads — in a rather acrobatic posture.

Crematogaster

Dorymyrmex flavus: Ants in the genus Dorymyrmex are easily recognized by a cone shaped structure on the their dorsal surface (just before the gaster). Their common name is cone or pyramid ants. The cones differ in size and shape. These differences are used to identify species.

Forelius mccooki (above) and Dorymyrmex flavus (below)

Forelius mccooki (above) and Dorymyrmex flavus (below)

The red arrow indicates the cone or pyramid on Dorymyrmex. This structure is diagnostic for the genus.

The red arrow indicates the cone or pyramid on Dorymyrmex. This structure is diagnostic for the genus.

Forelius mccooki

Forelius

Solenopsis invicta: This is the invasive, red imported fire ant. Note the antennae have a two-part club at the end and altogether there are 10 segments on each antennae. These features are diagnostic for the genus.

Solenopsis invicta collected from baits in the Fort Worth Nature Center.

Solenopsis invicta collected from baits in the Fort Worth Nature Center.

RESULTS:

Sample # Species Count
1 Solenopsis invicta  3
2 Crematogaster cerasi 2
3 Crematogaster cerasi 2
Dorymyrmex flavus  1
Forelius mccooki 18
4 Forelius mccooki 18
5 Crematogaster lineolata 6
Forelius mccooki 16
6 Camponotus americanus 1
Solenopsis invicta 1
Unknown 1
7 Forelius mccooki 3
Solenopsis invicta 1
8 Forelius mccooki 47
9 Solenopsis xyloni 3
10 Forelius mccooki 89
11 Crematogaster lineolata 4
Forelius mccooki 1
12 Solenopsis invicta 1
13 Forelius mccooki 2

Video clip #1: “Bug and Ants”

This clip shows many Forelius ants on a tuna bait. An insect, perhaps a bug, lands on the bait and interacts with these ants, then leaves. It looks like the ants may be performing a cleaning service which has been suggested for Forelius ants in some situations.

Video clip #2: “Crematogaster Waggle”

This clip shows many Forelius ants on tuna bait. A Crematogaster forager is in the lower right hand side. As this forager leaves the bait, she waggles her gaster indicating that she is dispensing a pheromone.
Here are the two short clips from tuna baits that the Trinity Valley School of Fort Worth, Texas set out at the Fort Worth Nature Center.

Looking for ants that define prairies

My analysis right now is focused on considerations of alpha and beta diversity. I have been held up by computer issues but here are the initial results of a form of discriminant analysis on ant species occurrence in 21 sites over 3 months in the Fort Worth/Arlington, Texas area.

I used both a biplot scaling (for short gradients — which I think is most appropriate) and a Hill’s scaling (which is meant for long gradients) and got the same results. So, I will continue these analyses with the biplot scaling.  This initial work was done using soil type as the clustering category. (I will continue DA using ecological group, habitat type (disturbance), and the presence of the Comanche harvester ant as clustering groups. So, several more analyses to do.)

This first summary table and plots are for species occurrence data from 21 sites. The analysis called a CCA in CANOCO, the program I am running (CCA is a general form of CVA, and otherwise called a discriminant analysis). I am using this as a clustering analysis: do the ants cluster by soil type basically. Turn it the other way round: Knowing the ants present, can I say what the soil is? Are the ants bioindicators?  This first analysis uses all the species presence data.

Here is the summary table:

**** Summary **** of CCA for Soil Clustering, biplot scaling, all species

Axes                                    1      2      3      4  Total inertia
Eigenvalues 1.000  0.970  0.770  0.706         6.000
Species-environment correlations  1.000 0.985 0.877 0.840 6.000
Cumulative percentage variance of species data                16.7   32.8   45.7   57.4
Cumulative percentage variance of species-environment relation   22.9   45.1   62.7   78.8
Sum of all eigenvalues      6.000
Sum of all canonical eigenvalues      4.370

And the biplot of data: messy, messy, messy. The red are the species, the triangles with the S followed by a number are the soils.

For the second analysis, I only included species that made up more than 1% of the total ants collected from that sample.

Here’s the summary table:

**** Summary Of CCA with Ecological Descriptors ****

Axes

1

2

3

4

Total inertia

 Eigenvalues                     

0.864

 0.776

 0.717

 0.608

        6.000

Species-environment correlations 

0.929

 0.881

 0.846

 0.780

Cumulative percentage variance of species data

14.4

  27.3

  39.3

  49.4

 Cumulative percentage variance of species-environment relation

24.7

  46.9

  67.4

  84.8

Sum of all  eigenvalues

 

 

 

 

  6.000

Sum of all canonical     eigenvalues     

 

 

 

 

  3.494

And the triplot — here with the addition of circles with numbers — these are the samples.

I haven’t reached interpretations or conclusions yet. This is still pretty raw data…

Prairie flowers at the Fort Worth Nature Center, Fort Worth, Texas

Ants in the Grassland: their importance and potential as indicators of ecosystem health

This is the presentation I made at the America’s Grassland Conference recently  in Manhattan, Kansas (August 2013).

I’ve posted the power point presentation below with a few additions and included the questions asked.

 

PRESENTATION SUMMARY

While we often think of ants as annoying pests, ants are important members of nearly every terrestrial ecosystem, except Antarctica. There are  perhaps 40,000 species worldwide and we have good species descriptions for about 14,000 of them – all of which are in the same family, the Formicidae.

Ants are incredibly diverse: they vary in their morphology, their behavior, their physiology, and their ecology. Ants may engineer ecosystems through their nesting and foraging habits – greatly shaping the physical landscape and thereby impacting a variety of other organisms including the plant community. Ants also have a diversity of relationships. They are important prey items as well as predators; they have important mutualistic relationships with plants, fungi, and other arthropods; they have their own parasites; they have commensals and parasites that live in their nests.

Because of all this ecological diversity, ants may be good indicators of habitats and ecosystem health. If there are changes in any of these relationships, for any of these organisms, this change may affect ant presence, activity, and abundance. Because ants are small and live on a small scale, they may detect such changes earlier than larger monitored species, such as vertebrates. Ants are also good candidates for indicators because they are easy to collect and do not have the problems of monitoring vertebrate populations which may be difficult to track, endangered or threatened species sensitive to handling, etc. The possibility for such utility has been shown in previous research.

I investigated the potential for grassland ant assemblages to be used as bio-indicators in prairies in the Fort Worth Nature Center and Wildlife Refuge in Fort Worth, Texas, including to discern habitat type and response to disturbance. I collected the ground active ants of 17 sites monthly from March – September 2012 using pitfall traps.  The 17 sites constituted a natural experiment: 3 were wooded sites and 14 were prairie sites. The sites were paired according to soil and ecological unit (from the Natural Resources Conservation Service) for wooded vs. non-wooded (3 replicates); mowed (and soil disturbance) vs. non-mowed (4 replicates); and low intensity burn vs. non-burned (2 replicates).

For each site, I measured environmental variables which are known or thought to be important to ants in choosing their nesting areas,  including depth of sand, soil penetration (compaction), depth to the restrictive layer, percent slope, drainage, percent bare ground, percent litter cover, percent standing plant cover, percent total cover, latitude, ecological units (from the NRCS), and soil type.

I used the program CANOCO to do ordination analyses: principle components analysis (PCA) on the environmental variables only and redundancy analysis (RDA) combining the environmental variables with species presence. Ant species were characterized by functional groups following Andersen (1997). The PCA confirmed that the variables chosen could be used to distinguish among sites. The RDA revealed that some of the ant species were aligned with habitats but disturbance did not matter. The sites grouped into three sets which aligned with soil types and ecological units. Some species did not align with their habitats but this may be explained by the foraging of those species into habitats other than where they nest. The RDA showed a strong relationship between the ants and the environmental variables with the interaction between percent litter cover and drainage, percent litter cover by itself and drainage by itself being significant factors. However, these factors combined did not explain more than 20% of the variation so either there are other significant factors or many factors account for the local presence of ants with none being particularly significant.

Andersen’s functional groups are problematic for these sites because some of the species placed in the groups do not have similar ecological roles as the Australian species upon which this work is based. Species richness by functional group did not vary significantly among the sites. And although the functional group designations are problematic, there is a  pattern in the composition of these assemblages with general myrmicines contributing most, followed by hot climate specialists, cryptic and opportunistic species, then tropical climate specialists and dominant species. This suggests a shape to the assemblages that may transcend individual species.

In conclusion, this project indicated weak support for these assemblages s as bioindicators and only two ants could be considered indicators of habitat: the carpenter ant species (Camponotus americanus and Camponotus pennsylvanicus) occurring in the woodlands and the Comanche harvester ant (Pogonomyrmex comanche) occurring in the Aquilla prairie.

Turret and nest of Trachymyrmex turrifex, Fort Worth Nature Center, Fort Worth, Texas.

Trachymyrmex ants

In my prairie sites where I study the Comanche harvester ant, I have found two species of Trachymyrmex: T. septentrionalis and T. turrifex. I have 14 prairie sites and of these 8 have both species, 5 have only T. turrifex and one has only T. septentrionalis. Finding both species is quite exciting for two reasons: first, these are funky looking ants with all kinds of spiny projections on their bodies. So, they were one of the first ant genera I learned to identify correctly. And they are very cute. But the more exciting thing has been the discovery of the nests of T. turrifex, which are turrets. They have a bit of a crater area in the middle of which is this turret, about 2 and ½ inches long. I was quite astonished when I happened upon some of these structures and more so when I saw ants coming in and out of them. I got some photos and some video as well.

Turret of Trachymyrmex turrifex, Fort Worth Nature Center, Fort Worth, Texas. This turret is about 2 inches tall.

Turret of Trachymyrmex turrifex, Fort Worth Nature Center, Fort Worth, Texas. This turret is about 2 inches tall.

The nest of T. septentrionalis is very different. The entrance is a few centimeters from a characteristic crescent shaped pile of soil which they make as they excavate their nest.

Trachymyrmex septentrionalis nest, Fort Worth Nature Center, Fort Worth, Texas

Trachymyrmex septentrionalis nest, Fort Worth Nature Center, Fort Worth, Texas

These differences in nest form, and ant nest architecture in general, are quite interesting to me. I have no idea what the differences in form between these two Trachymyrmex species are about — they are living in the same kinds of habitats and I believe have similar life patterns, etc. So, these nest differences are quite a mystery.

Earlier this summer, I found some Solenopsis xyloni easily coming and going in and out of a T. septentrionalis nest. The S. xyloni, a native fire ant species, and T. septentrionalis met each other at the entrance to the Trachymyrmex nest without out any sign of aggression and the S. xyloni preceded to enter the nest. Trachymyrmex expert Dr. Jon Seal (University of Texas-Tyler) has observed the same but does not know what is going on.

Trachymyrmex septentrionalis nest maintenance workers, Fort Worth Nature Center, Fort Worth, Texas

Trachymyrmex septentrionalis nest maintenance workers, Fort Worth Nature Center, Fort Worth, Texas

Solenopsis xyloni (smaller, shiny ant, lower) and Trachymyrmex septentrionalis (larger, rough looking ant at top) at the entrance to the T. septentrionalis nest.

Solenopsis xyloni (smaller, shiny ant, lower) and Trachymyrmex septentrionalis (larger, rough looking ant at top) at the entrance to the T. septentrionalis nest.

Trachymyrmex ants are related to the leaf cutter ants in the genera Atta and Acromyrmex. Though technically, not leaf cutter ants, Trachymyrmex ants may collect leaves to grow fungus like the true leaf cutter ants. But my understanding from Jon Seal is that Trachymyrmex ants are not obligate fungus eaters. They forage on other foods as well.