ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
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- All Subjects: Biology
- Creators: Hölldobler, Bert
- Creators: Cease, Arianne
Description
At the heart of every eusocial insect colony is a reproductive division of labor. This division can emerge through dominance interactions at the adult stage or through the production of distinct queen and worker castes at the larval stage. In both cases, this division depends on plasticity within an individual to develop reproductive characteristics or serve as a worker. In order to gain insight into the evolution of reproductive plasticity in the social insects, I investigated caste determination and dominance in the ant Harpegnathos saltator, a species that retains a number of ancestral characteristics. Treatment of worker larvae with a juvenile hormone (JH) analog induced late-instar larvae to develop as queens. At the colony level, workers must have a mechanism to regulate larval development to prevent queens from developing out of season. I identified a new behavior in H. saltator where workers bite larvae to inhibit queen determination. Workers could identify larval caste based on a chemical signal specific to queen-destined larvae, and the production of this signal was directly linked to increased JH levels. This association provides a connection between the physiological factors that induce queen development and the production of a caste-specific larval signal. In addition to caste determination at the larval stage, adult workers of H. saltator compete to establish a reproductive hierarchy. Unlike other social insects, dominance in H. saltator was not related to differences in JH or ecdysteroid levels. Instead, changes in brain levels of biogenic amines, particularly dopamine, were correlated with dominance and reproductive status. Receptor genes for dopamine were expressed in both the brain and ovaries of H. saltator, and this suggests that dopamine may coordinate changes in behavior at the neurological level with ovarian status. Together, these studies build on our understanding of reproductive plasticity in social insects and provide insight into the evolution of a reproductive division of labor.
ContributorsPenick, Clint A (Author) / Liebig, Jürgen (Thesis advisor) / Brent, Colin (Committee member) / Gadau, Jürgen (Committee member) / Hölldobler, Bert (Committee member) / Rutowski, Ron (Committee member) / Arizona State University (Publisher)
Created2012
Description
The coordination of group behavior in the social insects is representative of a broader phenomenon in nature, emergent biological complexity. In such systems, it is believed that large-scale patterns result from the interaction of relatively simple subunits. This dissertation involved the study of one such system: the social foraging of the ant Temnothorax rugatulus. Physically tiny with small population sizes, these cavity-dwelling ants provide a good model system to explore the mechanisms and ultimate origins of collective behavior in insect societies. My studies showed that colonies robustly exploit sugar water. Given a choice between feeders unequal in quality, colonies allocate more foragers to the better feeder. If the feeders change in quality, colonies are able to reallocate their foragers to the new location of the better feeder. These qualities of flexibility and allocation could be explained by the nature of positive feedback (tandem run recruitment) that these ants use. By observing foraging colonies with paint-marked ants, I was able to determine the `rules' that individuals follow: foragers recruit more and give up less when they find a better food source. By altering the nutritional condition of colonies, I found that these rules are flexible - attuned to the colony state. In starved colonies, individual ants are more likely to explore and recruit to food sources than in well-fed colonies. Similar to honeybees, Temmnothorax foragers appear to modulate their exploitation and recruitment behavior in response to environmental and social cues. Finally, I explored the influence of ecology (resource distribution) on the foraging success of colonies. Larger colonies showed increased consistency and a greater rate of harvest than smaller colonies, but this advantage was mediated by the distribution of resources. While patchy or rare food sources exaggerated the relative success of large colonies, regularly (or easily found) distributions leveled the playing field for smaller colonies. Social foraging in ant societies can best be understood when we view the colony as a single organism and the phenotype - group size, communication, and individual behavior - as integrated components of a homeostatic unit.
ContributorsShaffer, Zachary (Author) / Pratt, Stephen C (Thesis advisor) / Hölldobler, Bert (Committee member) / Janssen, Marco (Committee member) / Fewell, Jennifer (Committee member) / Liebig, Juergen (Committee member) / Arizona State University (Publisher)
Created2014
Description
Social insect colonies exhibit striking diversity in social organization. Included in this overwhelming variation in structure are differences in colony queen number. The number of queens per colony varies both intra- and interspecifically and has major impacts on the social dynamics of a colony and the fitness of its members. To understand the evolutionary transition from single to multi-queen colonies, I examined a species which exhibits variation both in mode of colony founding and in the queen number of mature colonies. The California harvester ant Pogonomyrmex californicus exhibits both variation in the number of queens that begin a colony (metrosis) and in the number of queens in adult colonies (gyny). Throughout most of its range, colonies begin with one queen (haplometrosis) but in some populations multiple queens cooperate to initiate colonies (pleometrosis). I present results that confirm co-foundresses are unrelated. I also map the geographic occurrence of pleometrotic populations and show that the phenomenon appears to be localized in southern California and Northern Baja California. Additionally, I provide genetic evidence that pleometrosis leads to primary polygyny (polygyny developing from pleometrosis) a phenomenon which has received little attention and is poorly understood. Phylogenetic and haplotype analyses utilizing mitochondrial markers reveal that populations of both behavioral types in California are closely related and have low mitochondrial diversity. Nuclear markers however, indicate strong barriers to gene flow between focal populations. I also show that intrinsic differences in queen behavior lead to the two types of populations observed. Even though populations exhibit strong tendencies on average toward haplo- or pleometrosis, within population variation exists among queens for behaviors relevant to metrosis and gyny. These results are important in understanding the dynamics and evolutionary history of a distinct form of cooperation among unrelated social insects. They also help to understand the dynamics of intraspecific variation and the conflicting forces of local adaptation and gene flow.
ContributorsOverson, Rick P (Author) / Gadau, Jürgen (Thesis advisor) / Fewell, Jennifer H (Committee member) / Hölldobler, Bert (Committee member) / Johnson, Robert A. (Committee member) / Liebig, Jürgen (Committee member) / Arizona State University (Publisher)
Created2011
Description
Land management practices such as domestic animal grazing can alter plant communities via changes in soil structure and chemistry, species composition, and plant nutrient content. These changes can affect the abundance and quality of plants consumed by insect herbivores with consequent changes in population dynamics. These population changes can translate to massive crop damage and pest control costs. My dissertation focused on Oedaleus asiaticus, a dominant Asian locust, and had three main objectives. First, I identified morphological, physiological, and behavioral characteristics of the migratory ("brown") and non-migratory ("green") phenotypes. I found that brown morphs had longer wings, larger thoraxes and higher metabolic rates compared to green morphs, suggesting that developmental plasticity allows greater migratory capacity in the brown morph of this locust. Second, I tested the hypothesis of a causal link between livestock overgrazing and an increase in migratory swarms of O. asiaticus. Current paradigms generally assume that increased plant nitrogen (N) should enhance herbivore performance by relieving protein-limitation, increasing herbivorous insect populations. I showed, in contrast to this scenario, that host plant N-enrichment and high protein artificial diets decreased the size and viability of O. asiaticus. Plant N content was lowest and locust abundance highest in heavily livestock-grazed fields where soils were N-depleted, likely due to enhanced erosion and leaching. These results suggest that heavy livestock grazing promotes outbreaks of this locust by reducing plant protein content. Third, I tested for the influence of dietary imbalance, in conjunction with high population density, on migratory plasticity. While high population density has clearly been shown to induce the migratory morph in several locusts, the effect of diet has been unclear. I found that locusts reared at high population density and fed unfertilized plants (i.e. high quality plants for O. asiaticus) had the greatest migratory capacity, and maintained a high percent of brown locusts. These results did not support the hypothesis that poor-quality resources increased expression of migratory phenotypes. This highlights a need to develop new theoretical frameworks for predicting how environmental factors will regulate migratory plasticity in locusts and perhaps other insects.
ContributorsCease, Arianne (Author) / Harrison, Jon (Thesis advisor) / Elser, James (Thesis advisor) / DeNardo, Dale (Committee member) / Quinlan, Michael (Committee member) / Sabo, John (Committee member) / Arizona State University (Publisher)
Created2012
Description
Understanding how and why animals choose what to eat is one of the fundamental goals of nutritional and behavioral biology. This question can be scaled to animals that live in social groups, including eusocial insects. One of the factors that plays an important role in foraging decisions is the prevalence of specific nutrients and their relative balance. This dissertation explores the role of relative nutrient content in the food selection decisions of a species that is eusocial and also agricultural, the desert leafcutter ant Acromyrmex versicolor. A dietary choice assay, in which the relative amount of protein and carbohydrates in the available diets was varied, demonstrated that A. versicolor colonies regulate relative collection of protein and carbohydrates. Tracking the foraging behavior of individual workers revelaed that foragers vary in their relative collection of experimental diets and in their foraging frequency, but that there is no relationship between these key factors of foraging behavior. The high proportion of carbohydrates preferred by lab colonies suggests that they forage to nutritionally support the fungus rather than brood and workers. To test this, the relative amounts of 1) fungus, and 2) brood (larvae) was manipulated and foraging response was measured. Changing the amount of brood had no effect on foraging. Although decreasing the size of fungus gardens did not change relative P:C collection, it produced significant increases in caloric intake, supporting the assertion that the fungus is the main driver of colony nutrient regulation. The nutritional content of naturally harvested forage material collected from field colonies was measured, as was recruitment to experimental diets with varying relative macronutrient content. Field results confirmed a strong colony preference for high carbohydrate diets. They also indicated that this species may, at times, be limited in its ability to collect sufficiently high levels of carbohydrates to meet optimal intake. This dissertation provides important insights about fundamental aspects of leafcutter ant biology and extends our understanding of the role of relative nutrient content in foraging decisions to systems that span multiple trophic levels.
ContributorsSmith, Nathan Edward (Author) / Fewell, Jennifer H (Thesis advisor) / Harrison, Jon F (Committee member) / Pavlic, Ted (Committee member) / Cease, Arianne (Committee member) / Hoelldobler, Bert (Committee member) / Arizona State University (Publisher)
Created2023
Description
The migratory grasshopper (Melanoplus sanguinipes) is one of the most economically important grasshoppers in the western rangelands of the United States (US), capable of causing incredible amounts of damage to crops and rangelands. While M. sanguinipes has been the focus of many research studies, areas like field nutritional physiology and ecology, and interactions between nutritional physiology and biopesticide resistance have very little research. This dissertation presents a multifaceted approach through three research-driven chapters that examine the nutritional physiology of M. sanguinipes and how it interacts with an entomopathogenic fungus for grasshopper management, as well as the challenges of using biopesticides for grasshopper management. Using the Geometric Framework for Nutrition (GFN), I established baseline macronutrient intake for M. sanguinipes, both in laboratory and field populations. Through this work, I found that field and lab populations can exhibit different protein (p) to carbohydrate (c) ratios, or Intake Targets (ITs), but that the field populations had ITs that matched the nutrients available in their environment. I also used the GFN to show that infections with the fungal entomopathogen Metarhizium robertsii DWR2009 did not alter ITs in M. sanguinipes. Although, when confined to carbohydrate- or protein-biased diets, infected grasshoppers had a slightly extended lifespan relative to grasshoppers fed balanced protein:carbohydrate diets. Interestingly, in a postmortem for the grasshopper, the fungus was only able to effectively sporulate on grasshoppers fed the 1p:1c diets, suggesting that grasshopper diet can have substantial impacts on the spread of fungal biopesticides throughout a population, in the absence of any inhibitory abiotic factors. Lastly, I examined the major barriers to fungal and microsporidian biopesticide usage in the United States, including low efficacy, thermal and environmental sensitivity, non-target effects, unregistered or restricted use, and economic or accessibility barriers. I also explored potential solutions to these challenges. This dissertation's focus on Melanoplus sanguinipes and Metarhizium roberstii Strain DWR2009, generates new information about how nutritional physiology and immunology intersect to impact M. sanguinipes performance. The methodology in each of the experimental chapters provides a framework for examining other problematic grasshopper species, by determining baseline nutritional physiology, and coupling nutrition with immunology to maximize the effectiveness of biological pesticides.
ContributorsZembrzuski, Deanna (Author) / Cease, Arianne (Thesis advisor) / Harrison, Jon (Committee member) / Angilletta, Michael (Committee member) / Jaronski, Stefan (Committee member) / Arizona State University (Publisher)
Created2023
Description
Dominance behavior can regulate a division of labor in a group, such as that between reproductive and non-reproductive individuals. Manipulations of insect societies in a controlled environment can reveal how dominance behavior is regulated. Here, I examined how morphological caste, fecundity, group size, and age influence the expression of dominance behavior using the ponerine ant Harpegnathos saltator. All H. saltator females have the ability to reproduce. Only those with a queen morphology that enables dispersal, however, show putative sex pheromones. In contrast, those with a worker morphology normally express dominance behavior. To evaluate how worker-like dominance behavior and associated traits could be expressed in queens, I removed the wings from alate gynes, those with a queen morphology who had not yet mated or left the nest, making them dealate. Compared to gynes with attached wings, dealates frequently performed dominance behavior. In addition, only the dealates demonstrated worker-like ovarian activity in the presence of reproductive individuals, whereas gynes with wings produced sex pheromones exclusively. Therefore, the attachment of wings determines a gyne’s expression of worker-like dominance behavior and physiology. When the queen dies, workers establish a reproductive hierarchy among themselves by performing a combination of dominance behaviors. To understand how reproductive status depends on these interactions as well as a worker’s age, I measured the frequency of dominance behaviors in groups of different size composed of young and old workers. The number of workers who expressed dominance scaled with the size of the group, but younger ones were more likely to express dominance behavior and eventually become reproductive. Therefore, the predisposition of age integrates with a self-organized process to form this reproductive hierarchy. A social insect’s fecundity and fertility signal depends on social context because fecundity increases with colony size. To evaluate how a socially dependent signal regulates dominance behavior, I manipulated a reproductive worker’s social context. Reproductive workers with reduced fecundity and a less prominent fertility signal expressed more dominance behavior than those with a stronger fertility signal and higher fecundity. Therefore, dominance behavior reinforces rank to compensate for a weak signal, indicating how social context can feed back to influence the maintenance of dominance. Mechanisms that regulate H. saltator’s reproductive hierarchy can inform how the reproductive division of labor is regulated in other groups of animals.
ContributorsPyenson, Benjamin (Author) / Liebig, Jürgen (Thesis advisor) / Hölldobler, Bert (Committee member) / Fewell, Jennifer (Committee member) / Pratt, Stephen (Committee member) / Kang, Yun (Committee member) / Arizona State University (Publisher)
Created2022
Description
Vector control plays an important role in the prevention and control of mosquito-borne diseases (MBDs). As there are no (prophylactic) drugs and/or vaccines available for many arboviral diseases (such as zika, chikungunya, Saint Louis encephalitis, Ross River virus), the frontline approach to prevent or reduce disease morbidity and mortality is through the reduction of the mosquito vector population size and/or reducing vector-human contact using insecticides. Frontline tools in malaria (an MBD caused by a parasite) control and elimination have been drugs (targeting the malaria parasite) and insecticides (targeting the vectors) through indoor residual spraying (IRS) (spraying the internal walls and sometimes the roofs of dwellings with residual insecticides to kill adult mosquito vectors), and long-lasting insecticidal nets (LLINs), while arboviral vectors are frequently targeted using outdoor fogging and space spraying (indoor or outdoor spraying of insecticides to kill adult mosquito vectors). Integrative and novel vector control efforts are urgently needed since the aforementioned tools may not be as effective against those mosquito species that are resistant to insecticides and/or have a different (or changed) behavior allowing them to avoid existing tools. In Chapters 2 and 3, I investigate mosquito vector surveillance in Arizona by (i) discussing the species composition and public health implications of the State’s mosquito fauna, and (ii) comparing the effectiveness of 4 different carbon dioxide (CO2) sources in attracting different mosquito species on the Arizona State University Tempe Campus. In Chapters 4 and 5, I investigate a novel vector control tool by (i) completing a literature review on using electric fields (EFs) to control insects, and (ii) presenting novel data on using Insulated Conductor Wires (ICWs) to generate EFs that prevent host-seeking female Aedes aegypti from entering spaces. In Chapter 6, I discuss the non-target effects of chemical malaria control on other arthropods, including other biological and mechanical infectious disease vectors. Overall, this dissertation highlights the important role that the development of novel surveillance and vector control tools could play in improved mosquito control, which ultimately will reduce disease morbidity and mortality.
ContributorsJobe, Ndey Bassin (Author) / Paaijmans, Krijn (Thesis advisor) / Cease, Arianne (Committee member) / Hall, Sharon (Committee member) / Huijben, Silvie (Committee member) / Arizona State University (Publisher)
Created2024
Description
An insect society needs to share information about important resources in order to collectively exploit them. This task poses a dilemma if the colony must consider multiple resource types, such as food and nest sites. How does it allocate workers appropriately to each resource, and how does it adapt its recruitment communication to the specific needs of each resource type? In this dissertation, I investigate these questions in the ant Temnothorax rugatulus.
In Chapter 1, I summarize relevant past work on food and nest recruitment. Then I describe T. rugatulus and its recruitment behavior, tandem running, and I explain its suitability for these questions. In Chapter 2, I investigate whether food and nest recruiters behave differently. I report two novel behaviors used by recruiters during their interaction with nestmates. Food recruiters perform these behaviors more often than nest recruiters, suggesting that they convey information about target type. In Chapter 3, I investigate whether colonies respond to a tradeoff between foraging and emigration by allocating their workforce adaptively. I describe how colonies responded when I posed a tradeoff by manipulating colony need for food and shelter and presenting both resources simultaneously. Recruitment and visitation to each target partially matched the predictions of the tradeoff hypothesis. In Chapter 4, I address the tuned error hypothesis, which states that the error rate in recruitment is adaptively tuned to the patch area of the target. Food tandem leaders lost followers at a higher rate than nest tandem leaders. This supports the tuned error hypothesis, because food targets generally have larger patch areas than nest targets with small entrances.
This work shows that animal groups face tradeoffs as individual animals do. It also suggests that colonies spatially allocate their workforce according to resource type. Investigating recruitment for multiple resource types gives a better understanding of exploitation of each resource type, how colonies make collective decisions under conflicting goals, as well as how colonies manage the exploitation of multiple types of resources differently. This has implications for managing the health of economically important social insects such as honeybees or invasive fire ants.
In Chapter 1, I summarize relevant past work on food and nest recruitment. Then I describe T. rugatulus and its recruitment behavior, tandem running, and I explain its suitability for these questions. In Chapter 2, I investigate whether food and nest recruiters behave differently. I report two novel behaviors used by recruiters during their interaction with nestmates. Food recruiters perform these behaviors more often than nest recruiters, suggesting that they convey information about target type. In Chapter 3, I investigate whether colonies respond to a tradeoff between foraging and emigration by allocating their workforce adaptively. I describe how colonies responded when I posed a tradeoff by manipulating colony need for food and shelter and presenting both resources simultaneously. Recruitment and visitation to each target partially matched the predictions of the tradeoff hypothesis. In Chapter 4, I address the tuned error hypothesis, which states that the error rate in recruitment is adaptively tuned to the patch area of the target. Food tandem leaders lost followers at a higher rate than nest tandem leaders. This supports the tuned error hypothesis, because food targets generally have larger patch areas than nest targets with small entrances.
This work shows that animal groups face tradeoffs as individual animals do. It also suggests that colonies spatially allocate their workforce according to resource type. Investigating recruitment for multiple resource types gives a better understanding of exploitation of each resource type, how colonies make collective decisions under conflicting goals, as well as how colonies manage the exploitation of multiple types of resources differently. This has implications for managing the health of economically important social insects such as honeybees or invasive fire ants.
ContributorsCho, John Yohan (Author) / Pratt, Stephen C (Thesis advisor) / Hölldobler, Bert (Committee member) / Liebig, Jürgen R (Committee member) / Amazeen, Polemnia G (Committee member) / Rutowski, Ronald L (Committee member) / Arizona State University (Publisher)
Created2019
Description
Ant colonies provide numerous opportunities to study communication systems that maintain the cohesion of eusocial groups. In many ant species, workers have retained their ovaries and the ability to produce male offspring; however, they generally refrain from producing their own sons when a fertile queen is present in the colony. Although mechanisms that facilitate the communication of the presence of a fertile queen to all members of the colony have been highly studied, those studies have often overlooked the added challenge faced by polydomous species, which divide their nests across as many as one hundred satellite nests resulting in workers potentially having infrequent contact with the queen. In these polydomous contexts, regulatory phenotypes must extend beyond the immediate spatial influence of the queen.
This work investigates mechanisms that can extend the spatial reach of fertility signaling and reproductive regulation in three polydomous ant species. In Novomessor cockerelli, the presence of larvae but not eggs is shown to inhibit worker reproduction. Then, in Camponotus floridanus, 3-methylheptacosane found on the queen cuticle and queen-laid eggs is verified as a releaser pheromone sufficient to disrupt normally occurring aggressive behavior toward foreign workers. Finally, the volatile and cuticular hydrocarbon pheromones present on the cuticle of Oecophylla smaragdina queens are shown to release strong attraction response by workers; when coupled with previous work, this result suggests that these chemicals may underly both the formation of a worker retinue around the queen as well as egg-located mechanisms of reproductive regulation in distant satellite nests. Whereas most previous studies have focused on the short-range role of hydrocarbons on the cuticle of the queen, these studies demonstrate that eusocial insects may employ longer range regulatory mechanisms. Both queen volatiles and distributed brood can extend the range of queen fertility signaling, and the use of larvae for fertility signaling suggest that feeding itself may be a non-chemical mechanism for reproductive regulation. Although trail laying in mass-recruiting ants is often used as an example of complex communication, reproductive regulation in ants may be a similarly complex example of insect communication, especially in the case of large, polydomous ant colonies.
This work investigates mechanisms that can extend the spatial reach of fertility signaling and reproductive regulation in three polydomous ant species. In Novomessor cockerelli, the presence of larvae but not eggs is shown to inhibit worker reproduction. Then, in Camponotus floridanus, 3-methylheptacosane found on the queen cuticle and queen-laid eggs is verified as a releaser pheromone sufficient to disrupt normally occurring aggressive behavior toward foreign workers. Finally, the volatile and cuticular hydrocarbon pheromones present on the cuticle of Oecophylla smaragdina queens are shown to release strong attraction response by workers; when coupled with previous work, this result suggests that these chemicals may underly both the formation of a worker retinue around the queen as well as egg-located mechanisms of reproductive regulation in distant satellite nests. Whereas most previous studies have focused on the short-range role of hydrocarbons on the cuticle of the queen, these studies demonstrate that eusocial insects may employ longer range regulatory mechanisms. Both queen volatiles and distributed brood can extend the range of queen fertility signaling, and the use of larvae for fertility signaling suggest that feeding itself may be a non-chemical mechanism for reproductive regulation. Although trail laying in mass-recruiting ants is often used as an example of complex communication, reproductive regulation in ants may be a similarly complex example of insect communication, especially in the case of large, polydomous ant colonies.
ContributorsEbie, Jessica (Author) / Liebig, Jürgen (Thesis advisor) / Hölldobler, Bert (Thesis advisor) / Pratt, Stephen (Committee member) / Smith, Brian (Committee member) / Rutowski, Ronald (Committee member) / Arizona State University (Publisher)
Created2020