Ant Colony Optimization (ACO) uses behaviour observed in real-life ant colonies in order to solve shortest path problems. Short paths are found with the use of pheromones, which allow ants to communicate indirectly. There are numerous pheromone distribution techniques for virtual ant systems and this thesis studies two of the most well known, Elitist and Max-Min. Implementations of Elitist and Max-Min ACO algorithms were tested using instances of the Traveling Salesman Problem (TSP). The performance of the different techniques are compared with respect to runtime, iterations and approximation quality when the optimal solution could not be found. It was found that the Elitist strategy performs better on small TSP instances where the number of possible paths are reduced. However, Max-Min proved to be more reliable and better performing when more paths could be chosen or size of the instances increased. When approximating solutions for large instances, Elitist was able to achieve high quality approximations faster than Max-Min. On the other hand, the overall quality of the approximations were better when Max-Min was studied after a slightly longer runtime, compared to Elitist. / Ant Colony Optimization (ACO) drar lärdom av beteende observerat hos riktiga myror för att lösa kortaste vägen problem. Korta vägar hittas med hjälp av feromoner, som tillåter myror att kommunicera indirekt. Det finns flera tekniker för att distribuera feromoner i virtuella myr-system och denna rapport kommer studera två av de mest kända, Elitist och Max-Min. Implementationer av Elitist och Max-Min ACO algoritmer testades med instanser av Handelsresandeproblemet (TSP). Prestandan hos de olika teknikerna jämförs med avseende på körtid, iterationer och approximeringskvalité när den optimala lösningen inte kunde hittas. Det konstaterades att Elitist strategin fungerar bättre på små TSP instanser där antalet möjliga stigar är begränsade. Däremot visade det sig Max-Min vara bättre och mer pålitlig när instansernas storlek ökades eller när fler stigar kunde väljas. När lösningar approximerades för stora instanser kunde Elitist uppnå approximationer med god kvalité snabbare än Max-Min. Däremot var den generella kvalitén hos approximationerna bättre när Max-Min studerades efter en lite längre körtid, jämfört med Elitist.

Traffic signal control is an effective way to improve the efficiency of traffic networks and reduce users’ delays. Ant Colony Optimization (ACO) is a metaheuristic based on the behavior of ant colonies searching for food. ACO has successfully been used to solve many NP-hard combinatorial optimization problems and its stochastic and decentralized nature fits well with traffic flow networks. This thesis investigates the application of ACO to minimize user delay at traffic intersections. Computer simulation results show that this new approach outperforms conventional fully actuated control under the condition of high traffic demand.

The Gravettian is the second chrono-cultural complex of the Upper Paleolithic after the Aurignacian. The Gravettian diffusion, throughout Europe, took place in a short span of time between 30.000 and 20.000 years BP. During this period, the climate instability due to the LGM approach created different environments. Particularly, Italy was split in two regions separated by the Apennine mountains: the cold and arid Adriatic coast on the first hand and the more temperate Tyrrhenian coast on the other hand. The latter region is the main object of this research. With the aim to understand the development and the mobility strategies used by the Gravettian groups in this area, several lithic assemblages have been analyzed. Specifically, the Gravettian sequence of Riparo Mochi (Balzi Rossi, Liguria - Italy), providing one of the most important stratigraphy of the Italian Upper Paleolithic, has been entirely studied. Inside the Balzi Rossi archaeological complex a direct comparison has been provided by the Gravettian collection of Grotta dei Faniculli. Moreover, some other smaller collections coming from the Provence area have been studied, allowing a comparison with the Balzi Rossi area. Finally, the site of Bilancino located in Tuscany let to contextualize the Gravettian between the liguro-provençal arc and Italy. The relation between techno-typological aspects and the raw materials provenance gives important advances in our comprehension of the behavior of the hunter-gatherer groups who inhabited the sites, discussing the timing and territorial mobility of the Tyrrhenian Gravettian.

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Solenopsis invicta is an invasive ant that has caused detrimental impacts to ecosystems and economies in the Southeastern United States, recently including Virginia. In this study, we explored the invasion ecology of S. invicta through two main objectives. First, we established a comprehensive distribution map of S. invicta in Virginia through multiple survey techniques. We then compared our findings with published models quantifying the potential spread of S. invicta and created our own species distribution model. In 2020-2021, S. invicta occurrences were found in 7 counties beyond the current Quarantine and our data show that S. invicta has spread further than predicted. Our own species distribution model suggests that the distribution area for S. invicta is likely to increase under the projected climate change. This study provides insights into the range expansion of S. invicta at the border of its suitable habitat and allow for improvements to models of its spread under these conditions. Additionally, it provides useful information to inform county extension agents to know where they are to expect new infestations of S. invicta. Second, we investigated the impacts of pesticide residue on the behavior of S. invicta through neonicotinoid exposure. We found detectable levels of neonicotinoids in the soil of the ant mounds as well as in the ants themselves. In addition, we investigated the effects of dietary exposure to imidacloprid on foraging behavior in a laboratory setting. We found that unexposed colonies were able to locate the food source more quickly during the second trial while exposed ants were unable to improve their performance. We also found that more exposed ant workers were unable to successfully navigate the maze as compared to unexposed workers. Our results suggest impaired learning of maze tasks and impaired navigational skills in neonicotinoid-exposed ants. / Master of Science in Life Sciences / The red imported fire ant (RIFA) is an invasive ant species found throughout the Southeastern United States that has negatively impacted ecosystems and economies. In the past few decades, RIFA has invaded the Coastal Plain of Virginia, resulting in legislation that restricts the movements of soil, plant products, and some equipment in and out of several southeastern counties and independent cities. To develop better management practices, there is a critical need to understand the spread, establishment, and impacts of RIFA in greater detail. We aimed to do this by surveying the current distribution of RIFA in Virginia and investigate the impact of insecticide use on their spread and behavior. In 2020-2021, we found RIFA occurrences in 7 counties beyond the current Quarantine, which is further than previously predicted. We then built a model using climatic variables that predicts the distribution of RIFA and found their habitable range is likely to increase under the projected climate change. Additionally, we investigated the impacts of common agricultural pesticides on the behavior of RIFA. We found these chemicals present in both the soil of the ant mounds and in the ants themselves. We also found that dietary exposure to imidacloprid, a neonicotinoid pesticide, altered the foraging behavior of RIFA. This study provides useful information to advise county extension agents to know where they are to expect new infestations of RIFA. Our results also suggest that human activity alters the invasion ecology of recent arrivals such as the red imported fire ant.

Foraging activity and food preferences of odorous house ants (Tapinoma sessile (SAY)) were investigated in both the field and laboratory. Foraging activity was examined in the field from April to September 2001 by attracting T. sessile to feeding stations containing a 20% sucrose solution. Ant foraging activity was recorded over a twenty-four hour period along with ambient temperature to examine possible correlations with ant activity patterns. Results indicate that foraging activity may be influenced by both time and temperature. In April and May when temperatures dropped below approximately 10 C, little or no foraging activity was observed. However, in the summer when temperatures were generally higher, foraging activity was greater during relatively cooler times of the day and night. Under laboratory conditions, T. sessile was attracted to feeding stations and foraged throughout the day and night at a constant temperature of approximately 25 C. Evaluations of seasonal food preferences using carbohydrate, protein and lipid samples were also conducted throughout the spring and summer. Results indicated no seasonal shifts in food preference in foraging ants; T sessile consistently preferred sugar and protein rewards over lipids. Macronutrient choice assays were preformed on T. sessile to evaluate specific food preferences. Several different carbohydrates, proteins, lipids and salts were tested in both liquid and gel formulation. Results indicated significantly greater consumption of sucrose solution at a concentration of approximately 20% compared with other sugars tested (fructose, glucose, trehalose and maltose). In addition, strong feeding responses were observed to both casein hydrolysate and lactalbumin hydrolysate at a 5% concentration. The addition of NaCl to 15% sucrose gel samples also enhanced feeding responses. Lipids were generally ignored by T. sessile and in most cases decreased consumption of the sample. Various amino acids did not enhance feeding responses and were similar to water. / Master of Science

In this thesis, we propose to use relevant potential invariants in a simulation-based swarmintelligence-based test generation technique to generate relevant test vectors for design validation at the Register Transfer Level (RTL). Providing useful guidance to the test generator for such techniques is critical. In our approach, we provide guidance by exploiting potential invariants in the design. These potential invariants are obtained using random stimuli such that they are true under these stimuli. Since these potential invariants are only likely to be true, we try to generate stimuli that can falsify them. Any such vectors would help reach some corners of the design. However, the space of potential invariants can be extremely large. To reduce execution time, we also implement a two-layer filter to remove the irrelevant potential invariants that may not contribute in reaching difficult states. With the filter, the vectors generated thus help to reduce the overall test length while still reach the same coverage as considering all unfiltered potential invariants. Experimental results show that with only the filtered potential invariants, we were able to reach equal or better branch coverage than that reported by BEACON in the ITC99 benchmarks, with considerable reduction in vector lengths, at reduced execution time. / Master of Science / Over the recent years, size and complexity of hardware designs are increasing at an enormous rate. Due to this, verification of these designs is of utmost importance and demands much more resources and time than designing of these hardware. To project the information of the designs, developers use Hardware Descriptive Languages (HDL), that includes the important decision points of the system, also called branches of the circuit. There are several methodologies proposed to check how many branches of the design can be traversed by set of inputs. This practice is important to confirm correct functionality of the design as we can catch all the faults in the design at these decision points. Some of these methodologies include checking with random inputs, exhaustively checking for every possible input, investing many hours of labor to verify with appropriate inputs, or simply automating the process of generating inputs. In this thesis, we focus on one such automated process called BEACON or Branch-oriented Evolutionary Ant Colony OptimizatioN. We propose a modification to improve this method by using standard properties of the design. These properties, also known as invariants, help to cover those branches that require extra effort in terms of both inputs and time, and are thus, hard to cover. When we add these significant invariants to the design, modified BEACON is able to cover almost all accessible branches in the system with significantly less amount of time and lesser number of vectors than original BEACON itself, which helps save a lot of resources.

Seed dispersal mutualisms, including seed dispersal by ants, are critical to the assembly of communities and the function of ecosystems. However, the consequences of human-caused global change factors, such as habitat fragmentation and climate change, for the future of these mutualisms are not fully understood. My dissertation consists of five chapters that investigated the effects of habitat fragmentation and climate change on ants and their seed dispersal mutualisms. Chapter 1 is an introduction that provides background information on habitat fragmentation and anthropogenic climate change and their impacts on biodiversity. In Chapter 1, I also introduce my study system of ant-mediated seed dispersal mutualisms, myrmecochory. My next two chapters (Chapters 2 and 3) explored the effects of reconnecting fragmented habitat patches with corridors in restored longleaf pine savanna systems in South Carolina. We used a landscape scale experiment to investigate how reducing isolation affects the assembly of ant communities over time (Chapter 2) and seed dispersal of the myrmecochorous forb, Piriqueta cistoides (Chapter 3). For Chapter 2, we found evidence that both habitat connectivity and edge effects underly the effects of corridors on ant communities over time. We found that connected patches accumulated ant species faster than isolated patches over time suggesting that corridors function by facilitating colonization. We also found evidence that edge effects play a role with greater ant functional group diversity in patches with higher edge than patches with lower edge amounts. For Chapter 3, we also found evidence of corridor and edge effects with ants dispersing seeds of P. cistoides longer distances in patches connected via corridors than isolated patches, but only in the center of patches. In Chapter 4, we investigated the effects of predicted climate change scenarios for seed dispersal mutualisms in eastern deciduous forests. For this chapter, we conducted a mesocosm experiment in which we crossed temperature with altered precipitation magnitude and frequency. Our mesocosms contained a common spring ephemeral wildflower, Sanguinaria canadensis, and whole colonies of their mutualist seed disperser, Aphaenogaster rudis. This design allowed us to collect high-resolution data on how ants interacted with seeds under different climate change scenarios that incorporated warming temperatures and altered precipitation. We found that warming effects depended on the precipitation treatment with negative effects of warming on the collection of seeds by ants under historical precipitation regimes and positive effects of warming under simulated precipitation conditions altered under predicted climate change. Finally, Chapter 5 describes my general conclusions from this body of work. Taken together, the research making up my dissertation provides valuable insights into how changing environmental conditions under habitat fragmentation and climate change may alter ant seed dispersal mutualisms. Importantly, we often found that the impacts of global change were context dependent and that our experiments were important tools in disentangling that context dependency. Further, this work demonstrates the value of understanding the basic ecology of the interactions among organisms. Understanding the natural history of organisms across changing environmental conditions will benefit the ways in which we conserve and restore ecosystems in a fragmented and warmer world. / Doctor of Philosophy / Most plants and animals engage in mutualisms, which are interactions between species in which both benefit from interacting with each other. The focus of this dissertation are the impacts of human-caused environmental change on the mutualism between ants and plants in which ants move a plant's seeds. The dispersal of ant-dispersed plants is considered a mutualism because the ants receive a food reward in the form of a fat- and protein-rich appendage that grows on the seed while the seeds of the plant get moved to a better location for germination. The mutualisms between ants and the plants they disperse are critical to how plants are distributed in many ecosystems, yet the consequences of human-caused environmental change, such as habitat loss and climate change, for these mutualisms are not fully understood. My dissertation consists of five chapters that investigated the effects of habitat fragmentation (the breaking apart of larger habitats into smaller, more isolated patches as a result of habitat loss) and climate change on ants and their seed dispersal mutualisms. My first chapter introduces background on the consequences of habitat fragmentation and climate change on organisms, ant seed dispersal mutualisms, and the potential effects of altered environmental conditions on seed dispersal by ants. My second two chapters (Chapters 2 and 3) explored the effects of reconnecting isolated habitat patches with habitat corridors (strips of habitat restored between the isolated habitat patches). In restored longleaf pine savanna systems in South Carolina, we used a long-term, landscape scale experiment to study how increasing connectivity and changing the shape of habitats via corridors affects ant community diversity over time (Chapter 2) and seed dispersal of the ant-dispersed plant, pitted stripeseed (Piriqueta cistoides) (Chapter 3). For Chapter 2, we found both habitat connectivity and patch shape effects underly the effects of corridors on ant community over time. We found that connected patches accumulated ant species faster than isolated patch types which suggests that corridors may function by facilitating colonization into the patches they connect. We also found evidence that patch shape plays a role in supporting greater ant functional group diversity in patches with greater perimeter (more edge habitat) than patches with less perimeter (less edge habitat). We found that ants in patches with more edge habitat represented a greater number of functional groups, which are categories that describe the roles ants play in ecosystems. For Chapter 3, we also found evidence of corridor and patch shape effects with ants dispersing seeds of pitted stripeseed longer distances in patches connected via corridors than isolated patches, but only in the center of patches. In Chapter 4, we investigated the effects of predicted climate change scenarios on seed dispersal mutualisms in eastern deciduous forests. For this chapter, we conducted an experiment in which we crossed temperature with altered precipitation in mesocosms, which are small, simulated ecosystems that allowed us to investigate the effects of warming and altered precipitation in a controlled setting. Our mesocosms contained a common spring ephemeral wildflower, bloodroot (Sanguinaria canadensis), and whole colonies of their mutualist seed disperser, winnow ants (Aphaenogaster rudis). We found that the effects of warming temperatures depended on the precipitation treatment. Warming had a negative effect on the number of seeds collected by ants under historical precipitation regimes, but a positive effect under simulated precipitation conditions under predicted climate change (higher in magnitude and lower in frequency). Finally, Chapter 5 describes my general conclusions from this body of work. Taken together, the research making up my dissertation provides valuable insights into how changing environmental conditions under habitat fragmentation and climate change may alter ant seed dispersal mutualisms. Importantly, we often found that the impacts of global change were context dependent. Our experiments were important tools in disentangling that context dependency. Further, this work demonstrates the value of understanding the basic ecology of the interactions among organisms. Understanding the natural history of organisms, especially their responses to changing environmental conditions, will ultimately benefit the ways in which we conserve and restore ecosystems in a fragmented and warmer world.