Ecological studies by undergraduate students at Brackenridge Field Laboratory, University of Texas at Austin. RM Plowes, LE Gilbert Published online 31 March, 2021 This document contains summaries and abstracts from student independent studies conducted at BFL. The full reports and the analyses by the students have not been independently verified or reviewed. The data underlying the reports can be provided at the discretion of the Director. However, the reports were developed by students and are not generally available for sharing. The majority of these studies were conducted in BIO373L Field Ecology. This course is instructed by Dr L. E. Gilbert and assisted by TA’s: R. Plowes, C. Estrada, R. Bocsa, H. Gillespie, K. Pierce, E. Resetarits, K. Jiang, L. Dugan, R. Deans, L. Trotter, C. Rakowski, C. Petersen Acknowledgements: H. Januska, J. Lawson, A. Miller for compiling the data. Abstracts from Previous BIO373L Student’s Independent Projects 1999 Gall Distribution on the Leaves of Vitis cadicans Amanda Rives – S99 Galls are commonly found on various parts of many types of plants. Questions concerning the impact of abiotic factors and the presence of other gall forming organisms are commonly posed in ecological studies of gall distribution. Considering theories of niche partitioning and competition, one would conclude that organisms would utilize different parts of the plant or would not oviposit on leaves that already had signs of a different organism. One would also assume that abiotic factors such as leaf location in the plant would play a role in the distribution as well. Additionally, it is possible that as leaf size increases, so should the number of galls. These ideas were tested using two different types of galls found on Vitis cadicans. Leaf width and height were measured, and the number of galls was counted at two different heights within three sites. These three sites were located at Brackenridge Field Lab in Austin, Texas and were at varying distances from the Colorado River. The obtained data were analyzed using a chi- square test. These tests indicated that height and distance from the river influence gall distribution. There was also a small correlation between increasing leaf size and more galls per leaf. It was also evident that the different types of galls that were studied were less commonly found together than on separate leaves. The Last Stand of Solenopsis geminata in Fire Fly Meadow Julie Warr – S99 About fifty years ago the fire ant Solenopsis invicta began its colonization of the south- eastern United States beginning near Mobile, Alabama (Porter 1990). S. invicta has managed to competitively exclude the native fire ant, S. geminata, from its habitat (Porter et al. 1988). All of Brackenridge Field Lab has been invaded by S. invicta except for Fire Fly Meadow. This study attempts to determine why this meadow has escaped the wrath of S. invicta while the remainder of the property is overrun with the exotic fire ants. Intraspecific Competition and Self-Thinning in Radishes Sherry Jacobsen – S99 Self-thinning as a result of intraspecific competition occurs in many plant species. When average biomass is plotted against final density, a slope of -1.5 is often found. This result is so common, it is referred to as the -3/2 power law. We examined radishes to determine if intraspecific competition and resulting self-thinning occurred in the species. Though correlations were found, they were not as strong as the -3/2 power law, indicating that, though intraspecific competition and self-thinning are probably present, most radish mortality resulted by other means. A comparison of bird species diversity and foliage height diversity during spring migration Samuel Hanes – S99 Previous studies have shown that bird and foliage diversities are positively correlated for breeding birds. I wanted to see if this was true during spring migration along the Colorado River. I investigated whether or not migratory birds had the same general distribution, relative to vegetation diversity, as do breeding birds, or if they were more evenly distributed. Unfortunately, few migratory birds were spotted during the duration of this study so comparisons between species richness vs. time and the species diversity for all birds vs. foliage height diversity were made. Three sites in five different areas were chosen for study at Brackenridge Field Laboratory. At each plot, the foliage height diversity was measured by dividing the foliage into three layers (ground level-2m, 2m-10m, and 10m+). Then each site was sampled for birds from April 9th to May 3rd beginning around 8:00 am. Overall there did seem to be a positive correlation between bird species diversity and foliage height diversity. While the diversity of breeding birds is probably more closely tied to vegetation structure than migrant diversity, migrants also need structurally diverse vegetation. Organization of Soil Invertebrate Fauna as Determined by Forest Cover Bryan Wofford – S99 Soil arthropods are key components in the recycling of nutrients. In wooded areas, arthropods are more abundant as there is more leaf litter to break down while in open areas, arthropods are less abundant as there is less organic matter to break down. In this study, I attempt to determine if soil invertebrate abundance and diversity is determined by climactic factors (temperature, moisture) or biological factors (nutrients from fauna) at Brackenridge Field Laboratory. Ten soil samples in total were taken from both open and wooded areas. The insects from each sample were then sorted and identified. Based on the results, species richness was higher in the covered areas rather than the open areas. Abundance was also reduced at the open sites when compared with the wooded areas. Overall, the factors affecting soil composition seem to be site specific and act in conjunction with one another rather than an either/or scenario. Pollinators of Lupinus texensis Gillian Saenz and Andrea Nunn – S99 The mutualism that occurs between plants and pollinators is crucial to ecosystems. In this study I aim to identify the major pollinators of the Texas Bluebonnet (Lupinus texensis) at Brackenridge Field Laboratory. Observations of bluebonnet patches began in mid-March and continued weekly for approximately four weeks. Any insects found visiting the flowers were captured and kept for identification. I also dissected a bluebonnet to collect any internal insects. A total of ten species were found on the flowers. Overwhelmingly, however, Apis mellifera was the most common insect found throughout the patches and was thus deemed the major pollinator of the bluebonnet. Interactions Between Different Ant Species Living in Close Proximity Jennifer Washburn – S99 In this study, I examined three situations of various ant species with nests in close proximity to one another. The nests were observed over the span of five weeks at Brackenridge Field Laboratory in Austin, Texas. Three ant species of the genus Pogonomyrmex (barbatus), Forelius, and Solenopsis (invicta) were the species being monitored living in close quarters to one another. Dominance between ant species was measured by setting out two ten minute and one hour bait traps with different baits at each site and seeing which species was predominantly found on the baits. I predicted that certain ant species would prefer different food baits which would allow them to live in such close proximity to one another. Overall, I found that Pogonomyrmex and Forelius ants were able to live in close quarters without much conflict due to different foraging preferences. In the presences of the Solenopsis fire ants, both the Pogonomyrmex and Forelius ants were out-competed, however, this may just be due to S. invicta’s raised aggression levels towards other species. The distribution of different ant species at BFL in bait traps and pitfall traps Michael Sorial – S99 Since the invasion of the important fire ant, Solenopsis invicta, native ant species have decreased in diversity and abundance at Brackenridge Field Laboratory. In this study, I aim to complete a survey of the relative abundance of ant species at BFL using baited and pitfall traps placed along the pre-existing transects at the field lab. When looking at all of the collected specimens from the traps, it is clear that S. invicta is the dominant species of ant present. S. invicta was also found in much higher numbers in the bait traps rather than the pitfall traps. A field study of two types of insect-induced galls and their distribution on Mustang Grape (Vitis mustangensis) at Brackenridge Field Laboratory, Austin Texas Jason Moss – S99 Galls form as a result from an attack from a parasite (bacterium, fungus, or insect) on a plant. Galls often provide food and protection to parasitic larvae living within its tissues. In this study, I collected samples of Mustang Grape (Vitis mustangensis) from three different sites at Brackenridge Field Laboratory and compared them for the presence of insect induced galls. I hoped to find a difference between the sample sites with regards to gall distribution and oviposition preference of the gall inducing insects. A higher number of galls were found on the Mustang Grape collected from the river area, suggesting that the insects prefer a moister environment. Because the gall insect has not been identified, this is merely a prediction and more data is needed to make conclusive statements. Red Imported Fire Ant Impacts on the Herpetological Community at BFL Paco Cardenas – S99 The invasion of the imported fire ant, Solenopsis invicta, has caused shifts in species diversity and abundance throughout trophic levels. Their high levels of aggression and their ability to live in a number of habitats has let them outcompete many native species. In this study, I conducted a survey of the reptiles and amphibians present at Brackenridge Field Laboratory to see how their numbers and territories have changed since the invasion of S.