Tag Archives: ant assemblage

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:

Redundancy Analysis on Ant Assemblage Data

Here are the preliminary results of the first redundancy analysis (RDA) for all the sites sampled over the summer of 2012. I performed a PCA with only environmental variables and one with only species data to look for an underlying pattern — which was confirmed. Then I ran an RDA with the full set of environmental variables and species data to determine the most significant quantitative environmental variables. Here are the results of the final RDA for this set of data which includes samples from 21 sites sampled monthly over the summer.

The Summary Table:

Axes

1

2

3

4

Total variance

Eigenvalues

0.358

0.129

0.060

0.020

1.000

Species-environment correlations 

0.977

0.956

0.923

0.720

Cumulative percentage variance of species data               

35.8

48.8

54.7

56.8

Cumulative percentage variance of species-environment relation

61.8

84.1

94.4

97.9

Sum of all eigenvalues     

1.000

Sum of all canonical eigenvalues     

0.580

Marginal effects of environmental variables:

Marginal Effects

Variable Var. N Lambda1
LiC 2 0.32
BG 4 0.27
LA 6 0.21
ToC 3 0.17
SP 5 0.07

Conditional effects of environmental variables:

Conditional Effects

Variable

Var. N

Lambda A

P

F

LiC 2 0.32 0.002 25.00
LA 6 0.13 0.002 12.20
BG 4 0.07 0.002 7.90
ToC 3 0.04 0.002 4.68
SP 5 0.02 0.028 1.81
LiC 2 0.32 0.002 25.00

Ordination Plots:

Species and environmental variables:

Species and Sites:

Comanche de-alate Queens as foragers

I am collecting more ant samples using pitfall traps to increase the sample size and  the number of different habitats for my ant assemblage study (per the suggestion of one of my committee members). I added two areas from the Southwest Nature Preserve in Arlington, Texas. One site is a mixed soil prairie site where there is a population of the Comanche harvester ant of about 50 colonies. The other is the forested site immediately beside this prairie. I will also be adding two sites from the Tandy Hills in Fort Worth and several more from the Fort Worth Nature Center. Here is the beginning data from the Southwest Nature Preserve:

I set out the traps on September 5 and collected the sample on the 8th. Looks like I have a new Temnothorax species which I haven’t been able to identify yet. I also have a de-alate Comanche queen from the forest. She cannot have been starting a new colony since these ants mate in May and June. This collection confirms my earlier observation of de-alate Comanche queens remaining in their natal nests as foragers in another population.

So far in the prairie: Pogonomyrmex comanche Dorymyrmex (probably two species), Forelius, Pheidole, Nylanderia (two species, maybe three), Trachymyrmex, Temnothorax texanus, Solenopsis (fire ant), Solenopsis (thief ant), and Crematogaster.

In the woods: Aphaenogaster, Pheidole, Crematogaster, de-alate Pogonomyrmex comanche queen, and Temnothorax.

Still working on species identifications. Of course, now I get to redo all my ordination analyses.

 

 

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.

Here the Comanche harvester ant (Pogonomyrmex comanche) forages  Pecan Sandies at a bait station in the Fort Worth Nature Center, Fort Worth, Texas

A Consideration of Andersen’s Functional Groups for North American Ant Assemblages

(These thoughts came out of an email exchange with noted myrmecologists Dr. James Trager of the Missouri Botanical Garden and Dr. Terry McGlynn of California State University Dominguez Hill).

I understand the concern that we not naively appropriate Andersen’s functional groups and the taxons that go into them – I think I have been on the verge of doing that. I obviously need to be exposed to more ant species.

My understanding is that Andersen tested dominance of the ants with bait stations and looked for aggressive interactions. Terry McGlynn’s questioning of this — that bait stations are artificial situations and do not reflect real ant behaviors/interactions well —  I think is well placed. I had thought to show that Pogonomyrmex comanche was a dominant ant in her habitat based on several observations but Dr. Walter Tschinkel, who is now on my committee, raised questions about this: what does dominance mean? I think this is a stickier issue than some believe.

For instance, there appears to be a trade-off between foragers who come early to baits and then leave and those who come later but seem to “dominate” the baits once they arrive. Are these later arrivals really dominant? I question this interpretation because of observations I have
made such as the interaction between P. comanche and a foraging grasshopper over a dead grasshopper (I have a  video) in which Comanche dealt with the competition by cutting up the grasshopper and foraging faster only at the last, stinging the offending grasshopper. When I see
Comanche dominate bait stations (photo above), I do not see the ants directly interact.

Here’s a photo of fire ant (Solenopsis sp.) at a food resource (though this was a cookie dropped in a parking lot). The fire ants seem to get to food resources quickly and to “swarm” on them effectively dominating them. I have seen fire ants overwhelm bait stations in the Fort Worth Nature Center in a similar manner. It seems a typical ant behavioral response to a desirable food resource is to dominate it indirectly by quick removal of it to the nest rather than more direct aggressive interactions which are probably more costly.

Fire ants (Solenopsis invicta or xyloni) opportunistically foraging on an Oreo cookie. I have seen this kind of "swarming" behavior on bait stations in the field as well.

Fire ants (Solenopsis invicta or xyloni) opportunistically foraging on an Oreo cookie. I have seen this kind of “swarming” behavior on bait stations in the field as well.

In the nestmate discrimination trials I am currently completing, I do not see Comanche often acting aggressively. I do see some gaster wagging in these trials. Gaster wagging is interpreted as am aggressive behavior but I am not so sure that it is always aggressive. In some situations, one ant grabs another and the one grabbed does the gaster wagging which appears more submissive. Other times, it is obvious the ants are curling their abdomens to sting. But mostly, the gaster wagging gives the impression of wafting some pheromone for some kind of communication which I am not able to discern (I need ant antennae, I guess.). Perhaps it is like arm or finger wrestling.

I think these situations are more nuanced than just dominance and perhaps many things are still ill defined.

Dr. Trager raised some important concerns about climate specialists and yet we know that climate contributes significantly to  ant occurrence at regional and continental levels. I think Andersen’s work my fit for these larger scales but not so well for more local scales at which I am working. (Scale is a significant concern and challenge in ecological studies. ) I think the scale issue is a part of the local spatial pattern of Comanche as well – it looks like regionally, they are found in sandy soiled prairies associated with oak forest, etc. but locally, Comanche spatial pattern and location may be a matter of queen dispersal. At first perhaps, new queens are attracted to locations with other colonies (conspecific attraction) but after landing, queens have to move farther away.  Later, negative interactions between colonies may come into play as well. Comanche colonies do move — and apparently, not in response to shading, like Pogonomyrmex badius or P. barbatus. But this is just my hunch based on observation and a few preliminary tests.

I also wonder about this: ant species appear to partition habitat seasonally, spatially, and temporarily in terms of activity patterns and so co-exist. These patterns add a level of
complexity which is a challenge.

*********************************************

Alan Andersen and his colleagues have conducted  many studies of ant assemblages with respect to disturbance (mining and deforestation in paricular) and functional groups especially in Australia. An important paper in consideration of these ideas in North America is:

Andersen, A. N. 1997. Functional groups and patterns of organization in North American ant communities: a comparison with Australia. Journal of Biogeography 24 (4): 433-460.

Ant Assemblage Data Analysis – beginning

Here is the Principal Components Analysis (PCA) summary for the 17 study sites and for ant species presence.

For Sites: There were 17 sites, 3 woodland sites and 14 prairie sites. Here are the site ID numbers used in the PCA.

Site Information

These are indicated with numbers on the biplot below.

PCA_Sites and EnVar

The colored rings indicate a loose grouping of the sites by the axes based on environmental variables measured.

Here is the summary of the analysis. The eigenvalues indicate the percentage of the data explained by the axes (which are a combination of the environmental variables measured). These are decent numbers for an ecological study 40% for the first axis and an additional 30% for the second axis.  These numbers indicate the variables measured are decent indicators of these sites/habitats.

Summary of EnVar PCA

 

Here is the PCA for the ant species collected in these sites.  This is presence/absence data.

PCA Biplot_Species

This is an incredible spread with no species tending to group together.

Here is the summary of the PCA.

PCA_Species and sites

These eigenvalues are abysmal — I believe they indicate that, with the exception of the Comanche harvester ant (Pogonomyrmex comanche), these ant species are generalists.

Follow-up analysis will include DCCA and RDA — forth coming.

 

Turret of a Trachymyrmex turrifex ant in the Fort Worth Nature Center, Fort Worth, Texas. Note the Ant leaving from the top of the turret.  The turret is about 4 cm high.

Prairie Ant Assemblages in the Fort Worth Nature Center, Fort Worth, Texas

Introduction:  Because ants have so many important ecological roles, the assessment of species present can give important insights into the ecosystem, including how nutrients are moved around and how the physical environment is structured. It has also been hypothesized that ant assemblages may be useful as bioindicators of ecosystem health, function, and change. This is a current area of interest and investigation for ecologists and myrmecologists. However, there has been a mixture of results with such assessments. For instance, Anderson has found ant assemblages to be quite useful in Australia (Andersen 1997 and Andersen and Majer 2004) but Franklin (2012) did not find the same utility in Mexico. The use of ant assemblages for ecosystem assessment is complicated by the niche of individual species and climate.  It may be expected that species in more temperate climates would be less restricted than in more tropical areas where niches are often very narrow.

I conducted an assessment of the ant assemblages in the Fort Worth Nature Center, Fort Worth, Texas as part of my study on the spatial ecology of the Comanche harvester ant (Pogonomyrmex comanche). I was interested in the role that the Comanche harvester ant might play as a dominant ant structuring the ant assemblage — does the presence or absence of the Comanche harvester ant affect which other ants are present? I was also interested in ants as bioindicators — can the ant assemblage be used to discern different habitats and the condition of these habitats? Because I was interested in what species might interact with the Comanche harvester ant, which is a ground nesting ant, I only sampled for ground active species.

Representative photos of most of my ant sampling sites in the Fort Worth Nature Center, Fort Worth, Texas

Representative photos of most of my ant sampling sites in the Fort Worth Nature Center, Fort Worth, Texas

Methods

Study Sites: I collected ants in 17 different sites in the Fort Worth Nature Center, Fort Worth, Texas in June, July, and August 2012. Three of these areas were wooded, post-oak forests associated with prairies where the Comanche harvester ant nests. The other 14 areas were prairies, three of which have Comanche harvester ants. Five of these prairies contain the same soil as the three prairies where the Comanche harvester ant nests and could have the Comanche harvester ant but do not.

 

Data Results:

Map of the Pitfall Trap Locations

Ant Presence Data

 

 

Literature Cited

Andersen, A. N. 1997. Functional groups and patterns of organization in North American ant communities in comparison with Australia. Journal of Biogeography 24: 433 – 460.

Andersen, A. N. and Majer, J. D. 2004. Ants show the way down under: invertebrates as bioindicators in land management. Frontiers in Ecology and the Environment 2: 291 – 298.

Franklin, K. 2012. The remarkable resilience of ant assemblages following major vegetation change in an arid ecosystem. Biological Conservation 148: 96 – 105.