Ants in the Grassland Ann B. Mayo University of Texas–Arlington America’s Grassland Conference Manhattan, KS their importance and potential as indicators of ecosystem health

Why study ants? They bit and sting. They may be pest and invasive species. We do not invite them on picnics. Fire ants (Solenopsis sp.) on an Oreo Ants are quite fascinating and important.

Importance of Ants Ubiquitous Diversity Ecosystem engineers Important relationships Nest mound of the Western harvester ant Internal nest of the Florida harvester ant

Potential as Bioindicators Ecology and small scale Ease of monitoring Hypotheses – Ground active ant assemblage will vary (and therefore, indicate) – with habitat – with disturbance Comparison of ant assemblages in 17 sites – Fort Worth Nature Center, Fort Worth, Texas Tree trimming and mowing in an electrical power line right of way

17 Study Sites 3 wooded sites and 14 prairie sites Natural experiment: sites were paired – same ecological unit/soil type burned and unburned: 2 replicates mowed and unmowed: 3 replicates wooded and non-wooded: 3 replicates Details of a Comanche harvester ant nest

Study Sites burned site oak woodland mowed/disturbance site Aquilla prairie Aledo clay loam

Methods Environmental variables – soil characteristics – vegetation characteristics – ecological units Ant collection – pitfall traps in a 3 X 5 grid – 72 hour collection per month – March – September 2012 Ordination Analysis in CANOCO Functional Groups

Results: PCA Environmental variables *** Summary of PCA for Environmental Variables **** Axes1234Total variance Eigenvalues Cumulative percentage variance of site data Sum of all eigenvalues 1.000

PCA: Ecological Units Aquilla prairie Aquilla woodland other sites

Results: RDA Species occurrence and environmental variables **** Summary of Full RDA with interaction term **** Axes1234Total variance Eigenvalues Species-environment correlations Cumulative percentage variance of species data Cumulative percentage variance of species-environment relation Sum of all eigenvalues Sum of all canonical eigenvalues 0.715

Significance of Effects Summary Marginal Effects VariableLambda 1 LiC*DRN0.13 LiCov0.12 DRN0.12 Conditional Effects VariableLambda APF LiC*DRN DRN LiCov

RDA: Sites and Variables

RDA: Species Occurrence

RDA: Species and Sites

Functional Groups Dominant Forelius (2) Camponotini Camponotus (2) Hot Climate Specialists Pogonomyrmex (2) Solenopsis (2 fire ants) Cold Climate Specialists Prenolepis (1) Cryptic Species Brachymyrmex (2) Solenopsis (2 thief ants) Strumigenys (3) Opportunistic Species Aphaenogaster (2) Dorymyrmex (2) Nylanderia (2) Generalized Myrmicinae Crematogaster (2) Formica (pallidefulva group - 1) Monomorium (1) Pheidole (4) Temnothorax (2) Specialist Predators -- none Tropical Climate Specialists Labidus (1) Trachymyrmex (2) the Comanche harvester ant harassed by Forelius

Functional Groups: site evaluation

Conclusions Align with environmental, vegetation, and ecological characteristics. Potential as indicators of habitat types Potential as monitors of ecosystem health the Comanche harvester ant foraging on seeds

Acknowledgements Photo of Dr. Tschinkel (Florida State University) and nest cast used with permission Fort Worth Nature Center and Wildlife Refuge City of Fort Worth, Texas – Parks and Community Services Department

Questions Asked Are there implications for understanding/monitoring climate change? Yes, this is one reason for studying ants – they are thermophilic in general and some species are found only in arid grasslands and deserts. As climate changes, the ant species present are expected to change in their occurrence, distribution and range. In the past, ants present in packrat middens have been used to asses or confirm climate conditions.

Questions Asked How are nest casts made? Dr. Walter Tschinkel has especially developed techniques for making casts in wax, plaster, and aluminum. The chosen material is poured into a nest, allowed to harden, and then excavated. Visit his site at Florida State University for more information. He has several papers on nest casts and architecture.

Questions Asked What does low intensity fire mean? The prairies that were burned were controlled, low intensity burns meant to control scrubby woody growth and reduce litter. Intensity of a burn has to do with how hot and how long. These burns did not significantly effect the soil. For ants, this means that only the microclimate above ground was affected which can be a significant deterrent to ant activity and presence. I did not detect such an effect in this study.