Artifact #1

Ant Population Dynamics in the Pine Barrens:

A Comprehensive Study

Tom Garcia, Randy Faiges, Derrick Hanke, Benjamin Pratt, Brian Santoleri

ABSTRACT: Ants in the Pine Barrens go largely unnoticed, much unlike more charismatic mega fauna found throughout the area (such as the white tailed deer) due to their minimal size and ability to go unnoticed. However, ant populations act as optimal indicator species regarding the quality of the ecosystem in which they live. Considering their ability to live in a variety of habitats, including disturbed habitats, samples have the potential to tell us how that ecosystem has been affected by variables such as development, environmental degradation, and weather. The goal of this study is to sample and analyze different types of habitat for ant species along the environmental gradient of the Southern New Jersey Pine Barrens. Sites included in this study range from the Upland Tower Oak Pine Forest, the Scrub-Oak Site, and the disturbed habitat of the Powerline Site juxtaposed to the Garden State Parkway. The populations were sampled by laying cookie bait, collecting, and then analyzing the samples by identifying the genus of each ant collected. Variables taken into consideration were average temperature, type of soil, and the severity of disturbance to their habitat.

Introduction:

The question

Do variables such as weather conditions, habitat disturbance, and soil condition affect overall ant populations? Do they affect species diversity of ants found in those areas?

Previous Studies

A study done in the Spring of 2011 indicates that the undisturbed woody area sampling sites housed much more biodiversity and numbers in population compared to the disturbed area of the power lines site. The overall spring 2011study found eight different species of ants within four sampling sites. The average temperature for April 2011 was 47˚F, and it rained during all days of their data sampling. They indicated that fewer ants were found compared to past years given the lower average temperature and the presence of much rain. A study conducted during the Spring of 2010 indicated that there was a greater amount of ants within the power lines site, but much less biodiversity; found to be more dry and 8˚F warmer than the Spring 2011 findings.

Hypothesis

Previous studies indicated that the conditions of soil, rainfall, and average temperature greatly affect the quantity of active ant populations. Therefore, we hypothesize that, given the relatively dry conditions and abnormally warm temperatures in South Jersey through the winter of 2012, ant populations will be more abundant and diverse than previous studies. We believe that the warmer conditions will have allotted for an abundance of food and quality habitat for ant populations. Hence, we suspect to find a wider variety of ant types as well as an overall increase of the number of ants in the areas studied as compared to previous studies.

Experimental Design

The first step we took in the study was to observe the different sites for baiting. Reasons for choosing these sites were because they were located at different spots along the environmental gradient and had significantly different soil types and plant species as well as varying levels of habitat disturbance. Next, we reviewed methodologies from previous studies in order to understand the most beneficial baiting and collection techniques. Following the methods of the previous studies, bait was laid out during morning hours and collected approximately 2-4 hours later. Samples were frozen overnight and then analyzed according to genus the following day.

Methods:

Site Locations:

Site 1- Upland Tower: N 39.493˚ W 74.524˚

Site 2- Scrub/Oak: N 39.804˚ W 74.831˚

Site 3- Powerlines: N 39.492˚ W 74.519˚

Baiting:

Baiting took place March 27th at 1000 HRS. The weather conditions were sunny and approximately 55˚F with low winds. Only one student researcher was needed to lay the bait. Baiting time was roughly one hour. Twenty-five index cards were placed in 25m² matrices. The bait was laid on the ground floor by brushing aside leaf-litter so that ants would find the bait more quickly. Cookie-bait was halved to expose the icing in order to attract the highest potential volume of ants. Each piece of bait was placed on an index card to ensure ease of collection. By placing the bait on the index cards it not only aided in locating the bait during collection but also made it exponentially easier to collect the bait without losing samples. Small flag markers were also placed by the samples so that they could be easily located.

Data Collection:

Samples were collected by a pair of researchers 2-4 hours after original bait was laid out. The grouping was essential; one would hold the plastic bag open while the other would pick up the index card and throw it in the bag quickly without losing ants. Time spent collecting at each site was approximately 15-20 minutes due to the density of the shrubs and low-lying plants. In total, it took about one hour to collect the specimens to bring back to the lab.

Preparation:

Collected specimens were left in plastic bags and placed in a freezer over-night. The following day the samples were removed from the freezer and placed in vials of 80% ethanol. They were then placed in petri dishes to be examined and identified under a microscope.

Results:

Our results from the spring of 2012 differ greatly from previous data. Comparatively, the spring of 2012 has been much dryer and warmer than 2011. We collected 301 specimens; in 2011 only 166 total specimens were collected. Our analysis shows significant differences from last spring. Entirely new species of ants were found from our samples as compared to the previous year. However, there were also ants found in the previous year that we did not see in our collections. This year, we found ants that belong to the genus Myrimica and Pheidole in the upland tower site. These two species were not collected from the spring of 2011. Tetramorium specimens found within the power lines site displayed an exponential increase over the year. We recovered 288 Tetramorium in the spring of 2012 at the power lines site alone, and only 31 were found in the spring of 2011. Twenty-six Lasius and forty-two Prenolepis were recovered in the spring of 2011; we did not identify Lasius, but we found half as many Prenolepis. The power line site is the most disturbed area, yet this site housed the majority of our specimens collected and ranked second in terms of ant diversity in the spring of 2012. Last year this collection site was the least diverse. When comparing the summer samples collected by Jamie Cromartie from the Upland Tower site, there is a considerable decrease in total ants collected from 2010 to 2011. Although the most abundant species (Cremogaster, Formica, Tetramorium) remained in proportion to the total collection compared to 2010, the Aphaenogaster totals dropped considerably in the upland tower site from 60 to 4. Also, different ant species were found in 2011 that escaped cookie traps from 2010. In 2010, a group of nine Themnothorax along with a foursome of Campanutos were captured. Last year, species of Myrmica (9) and Pheidole (8) were collected in the area.

Discussion Conclusion:

We hypothesized that warm climates are a characteristic to a thriving ant society. The relatively dry conditions and abnormally warm temperatures in 2012, ant populations were more abundant and diverse than previous studies. Studying last year’s results, spring 2011 was considerably colder and wet than this year and captured almost half of what we collected. Due to the fact that this year was considerable dryer and warmer than last year, more ants were recorded in our data. Although our group was not present during these summer collections, we can assume from our research that changes in temperature, weather, and humidity played a role in the substantial decrease in total species captured. The Pine Barren ecosystems provide a larger abundance of resources for ant populations due to the warmer climate. These resources include things such as viable habitat and various foods. Thus the warm weather had a direct effect on the availability of those essential goods, hence the greater number of ants collected.

Recommendations for Further Research:

When conducting further research on Southern New Jersey Pine Barrens it is recommended that cookie bait have cream spread evenly on both sides of cookie when bait is halved. Additionally, alternative baits should be tested for viability as well. In previous studies tuna was used in addition to cookie bait. The messiness of the bait made it too difficult for us. However, native fruit from the area or honey could be tested. Finally, a simplified ant analysis guide is highly recommended. While it is realized that the guide is essential for building identification skills, the use of the guide consumed a large portion of time that could have been used for additional collections. The common types of ants found throughout the studies should be written down with a list of key identifying factors for easy analysis. Species that are not identified from the simplified guide could then be identified with the full guide.

Literature Cited:

Wilson, Edward, and Bert Holldobler. "How to Study Ants." Ants. (1990): pp.630-633. Print.

Agosti, Donat, Jonathan Majer, et al. "Biodiversity Studies, Monitoring, and Ants: An Overview."Ants Standard Methods for Measuring and Monitoring Biodiversity. (2000): pp. 280. Print.

D'Amico, Michelle, William Smith, and Derek Macaulay, comp. The Ants Go Marching In. Print. <http://loki.stockton.edu/~cromartj/ecology/Stocktonia/Stocktonia14 1 2011.pdf>.

Acknowledgements:

Time Table:

March 10th- Entire group meets in library to review previous studies and discuss experimental design.

March 27th 1000 HRS- Randy lays cookie bait at all three sites.

March 27th 1230 HRS- Tom and Ben go out to collect bait and freeze for analysis.

March 28th- Tom, Ben, Brian, and Randy meet in lab to analyze samples.

March 29th 1000 HRS- Randy lays second cookie bait at all three sites.

March 29th 1300 HRS- Tom and Ben collect samples and freeze.

March 30th- Ben, Tom, and Randy meet in lab to analyze samples

April 25th 730 HRS- Brian starts identifying summer samples in lab.

April 30th 1230 HRS Brian continues analyzing samples in lab.

- Multiple days were spent in the lab reviewing samples from our collections as well as samples from Professor Cromartie’s summer 2011 collection. An approximate 40-50 hours was spent in the lab analyzing samples.