Matching Items (14)
Filtering by
- Genre: Academic theses
- Member of: Theses and Dissertations
Description
Conditions during development can shape the expression of traits at adulthood, a phenomenon called developmental plasticity. In this context, factors such as nutrition or health state during development can affect current and subsequent physiology, body size, brain structure, ornamentation, and behavior. However, many of the links between developmental and adult phenotype are poorly understood. I performed a series of experiments using a common molecular currency - carotenoid pigments - to track somatic and reproductive investments through development and into adulthood. Carotenoids are red, orange, or yellow pigments that: (a) animals must acquire from their diets, (b) can be physiologically beneficial, acting as antioxidants or immunostimulants, and (c) color the sexually attractive features (e.g., feathers, scales) of many animals. I studied how carotenoid nutrition and immune challenges during ontogeny impacted ornamental coloration and immune function of adult male mallard ducks (Anas platyrhynchos). Male mallards use carotenoids to pigment their yellow beak, and males with more beaks that are more yellow are preferred as mates, have increased immune function, and have higher quality sperm. In my dissertation work, I established a natural context for the role that carotenoids and body condition play in the formation of the adult phenotype and examined how early-life experiences, including immune challenges and dietary access to carotenoids, affect adult immune function and ornamental coloration. Evidence from mallard ducklings in the field showed that variation in circulating carotenoid levels at hatch are likely driven by maternal allocation of carotenoids, but that carotenoid physiology shifts during the subsequent few weeks to reflect individual foraging habits. In the lab, adult beak color expression and immune function were more tightly correlated with body condition during growth than body condition during subsequent stages of development or adulthood. Immune challenges during development affected adult immune function and interacted with carotenoid physiology during adulthood, but did not affect adult beak coloration. Dietary access to carotenoids during development, but not adulthood, also affected adult immune function. Taken together, these results highlight the importance of the developmental stage in shaping certain survival-related traits (i.e., immune function), and lead to further questions regarding the development of ornamental traits.
ContributorsButler, Michael (Author) / McGraw, Kevin J. (Thesis advisor) / Chang, Yung (Committee member) / Deviche, Pierre (Committee member) / DeNardo, Dale (Committee member) / Rutowski, Ronald (Committee member) / Arizona State University (Publisher)
Created2012
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
Parental care provides many benefits to offspring. One widely realized benefit is enhanced regulation of offspring's thermal environment. The developmental thermal environment during development can be optimized behaviorally through nest site selection and brooding, and it can be further enhanced by physiological heat production. In fact, enhancement of the developmental thermal environment has been proposed as the initial driving force for the evolution of endothermy in bird and mammals. I used pythons (Squamata: Pythonidae) to expand existing knowledge of behavioral and physiological parental tactics used to regulate offspring thermal environment. I first demonstrated that brooding behavior in the Children's python (Antaresia childreni) is largely driven by internal mechanisms, similar to solitary birds, suggesting that the early evolution of the parent-offspring association was probably hormonally driven. Two species of python are known to be facultatively thermogenic (i.e., are endothermic during reproduction). I expand current knowledge of thermogenesis in Burmese pythons (Python molurus) by demonstrating that females use their own body temperature to modulate thermogenesis. Although pythons are commonly cited as thermogenic, the actual extent of thermogenesis within the family Pythonidae is unknown. Thus, I assessed the thermogenic capability of five previously unstudied species of python to aid in understanding phylogenetic, morphological, and distributional influences on thermogenesis in pythons. Results suggest that facultative thermogenesis is likely rare among pythons. To understand why it is rare, I used an artificial model to demonstrate that energetic costs to the female likely outweigh thermal benefits to the clutch in species that do not inhabit cooler latitudes or lack large energy reserves. In combination with other studies, these results show that facultative thermogenesis during brooding in pythons likely requires particular ecological and physiological factors for its evolution.
ContributorsBrashears, Jake (Author) / DeNardo, Dale (Thesis advisor) / Harrison, Jon (Committee member) / Deviche, Pierre (Committee member) / McGraw, Kevin (Committee member) / Smith, Andrew (Committee member) / Arizona State University (Publisher)
Created2012
Description
A global warming of two degrees Celsius is predicted to drive almost half the world's lizard populations to extinction. Currently, the Phoenix metropolitan region in Arizona, USA, is an average of 3 oC warmer than the surrounding desert. Using a bare lot as a control, I placed copper lizard models with data loggers in several vegetation and irrigation treatments that represent the dominant backyard landscaping styles in Phoenix (grassy mesic with mist irrigation, drip irrigated xeric, unirrigated native, and a hybrid style known as oasis). Lizard activity time in summer is currently restricted to a few hours in un-irrigated native desert landscaping, while heavily irrigated grass and shade trees allow for continual activity during even the hottest days. Maintaining the existing diversity of landscaping styles (as part of an ongoing mitigation strategy targeted at humans) will be beneficial for lizards.
Fourteen native lizard species inhabit the desert surrounding Phoenix, AZ, USA, but only two species persist within heavily developed areas. This pattern is best explained by a combination of socioeconomic status, land cover, and location. Lizard diversity is highest in affluent areas and lizard abundance is greatest near large patches of open desert. The percentage of building cover has a strong negative impact on both diversity and abundance. Despite Phoenix's intense urban heat island effect, which strongly constrains the potential activity and microhabitat use of lizards in summer, thermal patterns have not yet impacted their distribution and relative abundance at larger scales.
Fourteen native lizard species inhabit the desert surrounding Phoenix, AZ, USA, but only two species persist within heavily developed areas. This pattern is best explained by a combination of socioeconomic status, land cover, and location. Lizard diversity is highest in affluent areas and lizard abundance is greatest near large patches of open desert. The percentage of building cover has a strong negative impact on both diversity and abundance. Despite Phoenix's intense urban heat island effect, which strongly constrains the potential activity and microhabitat use of lizards in summer, thermal patterns have not yet impacted their distribution and relative abundance at larger scales.
ContributorsAckley, Jeffrey (Author) / Wu, Jianguo (Thesis advisor) / Sullivan, Brian (Thesis advisor) / Myint, Soe (Committee member) / DeNardo, Dale (Committee member) / Angilletta Jr., Michael (Committee member) / Arizona State University (Publisher)
Created2015
Description
There is considerable recent interest in the dynamic nature of immune function in the context of an animal’s internal and external environment. An important focus within this field of ecoimmunology is on how availability of resources such as energy can alter immune function. Water is an additional resource that drives animal development, physiology, and behavior, yet the influence hydration has on immunity has received limited attention. In particular, hydration state may have the greatest potential to drive fluctuations in immunity and other physiological functions in species that live in water-limited environments where they may experience periods of dehydration. To shed light on the sensitivity of immune function to hydration state, I first tested the effect of hydration states (hydrated, dehydrated, and rehydrated) and digestive states on innate immunity in the Gila monster, a desert-dwelling lizard. Though dehydration is often thought to be stressful and, if experienced chronically, likely to decrease immune function, dehydration elicited an increase in immune response in this species, while digestive state had no effect. Next, I tested whether dehydration was indeed stressful, and tested a broader range of immune measures. My findings validated the enhanced innate immunity across additional measures and revealed that Gila monsters lacked a significant stress hormone response during dehydration (though results were suggestive). I next sought to test if life history (in terms of environmental stability) drives these differences in dehydration responses using a comparative approach. I compared four confamilial pairs of squamate species that varied in habitat type within each pair—four species that are adapted to xeric environments and four that are adapted to more mesic environments. No effect of life history was detected between groups, but hydration was a driver of some measures of innate immunity and of stress hormone concentrations in multiple species. Additionally, species that exhibited a stress response to dehydration did not have decreased innate immunity, suggesting these physiological responses may often be decoupled. My dissertation work provides new insight into the relationship between hydration, stress, and immunity, and it may inform future work exploring disease transmission or organismal responses to climate change.
ContributorsMoeller, Karla T (Author) / DeNardo, Dale (Thesis advisor) / Angilletta, Michael (Committee member) / French, Susannah (Committee member) / Rutowski, Ronald (Committee member) / Sabo, John (Committee member) / Arizona State University (Publisher)
Created2016
Description
In species with highly heteromorphic sex chromosomes, the degradation of one of the sex chromosomes can result in unequal gene expression between the sexes (e.g., between XX females and XY males) and between the sex chromosomes and the autosomes. Dosage compensation is a process whereby genes on the sex chromosomes achieve equal gene expression which prevents deleterious side effects from having too much or too little expression of genes on sex chromsomes. The green anole is part of a group of species that recently underwent an adaptive radiation. The green anole has XX/XY sex determination, but the content of the X chromosome and its evolution have not been described. Given its status as a model species, better understanding the green anole genome could reveal insights into other species. Genomic analyses are crucial for a comprehensive picture of sex chromosome differentiation and dosage compensation, in addition to understanding speciation.
In order to address this, multiple comparative genomics and bioinformatics analyses were conducted to elucidate patterns of evolution in the green anole and across multiple anole species. Comparative genomics analyses were used to infer additional X-linked loci in the green anole, RNAseq data from male and female samples were anayzed to quantify patterns of sex-biased gene expression across the genome, and the extent of dosage compensation on the anole X chromosome was characterized, providing evidence that the sex chromosomes in the green anole are dosage compensated.
In addition, X-linked genes have a lower ratio of nonsynonymous to synonymous substitution rates than the autosomes when compared to other Anolis species, and pairwise rates of evolution in genes across the anole genome were analyzed. To conduct this analysis a new pipeline was created for filtering alignments and performing batch calculations for whole genome coding sequences. This pipeline has been made publicly available.
In order to address this, multiple comparative genomics and bioinformatics analyses were conducted to elucidate patterns of evolution in the green anole and across multiple anole species. Comparative genomics analyses were used to infer additional X-linked loci in the green anole, RNAseq data from male and female samples were anayzed to quantify patterns of sex-biased gene expression across the genome, and the extent of dosage compensation on the anole X chromosome was characterized, providing evidence that the sex chromosomes in the green anole are dosage compensated.
In addition, X-linked genes have a lower ratio of nonsynonymous to synonymous substitution rates than the autosomes when compared to other Anolis species, and pairwise rates of evolution in genes across the anole genome were analyzed. To conduct this analysis a new pipeline was created for filtering alignments and performing batch calculations for whole genome coding sequences. This pipeline has been made publicly available.
ContributorsRupp, Shawn Michael (Author) / Wilson Sayres, Melissa A (Thesis advisor) / Kusumi, Kenro (Committee member) / DeNardo, Dale (Committee member) / Arizona State University (Publisher)
Created2016
Description
In wild birds, the stress response can inhibit the activity of the innate immune system, which serves as the first line of defense against pathogens. By elucidating the mechanisms which regulate the interaction between stress and innate immunity, researchers may be able to predict when birds experience increased susceptibility to infections and can target specific mediators to mitigate stress-induced suppression of innate immune activity. Such elucidation is especially important for urban birds, such as the House Sparrow (Passer domesticus), because these birds experience higher pathogen prevalence and transmission when compared to birds in rural regions. I investigated the role of corticosterone (CORT) in stress-induced suppression of two measures of innate immune activity (complement- and natural antibody-mediated activity) in male House Sparrows. Corticosterone, the primary avian glucocorticoid, is elevated during the stress response and high levels of this hormone induce effects through the activation of cytosolic and membrane-bound glucocorticoid receptors (GR). My results demonstrate that CORT is necessary and sufficient for stress-induced suppression of complement-mediated activity, and that this relationship is consistent between years. Corticosterone, however, does not inhibit complement-mediated activity through cytosolic GR, and additional research is needed to confirm the involvement of membrane-bound GR. The role of CORT in stress-induced inhibition of natural antibody-mediated activity, however, remains puzzling. Stress-induced elevation of CORT can suppress natural antibody-mediated activity through the activation of cytosolic GR, but the necessity of this mechanism varies inter-annually. In other words, both CORT-dependent and CORT-independent mechanisms may inhibit natural antibody-mediated activity during stress in certain years, but the causes of this inter-annual variation are not known. Previous studies have indicated that changes in the pathogen environment or food availability can alter regulation of innate immunity, but further research is needed to test these hypotheses. Overall, my dissertation demonstrates that stress inhibits innate immunity through several mechanisms, but environmental pressures may influence this inhibitory relationship.
ContributorsGao, Sisi (Author) / Deviche, Pierre (Thesis advisor) / DeNardo, Dale (Committee member) / McGraw, Kevin (Committee member) / Orchinik, Miles (Committee member) / Moore, Michael C. (Committee member) / Arizona State University (Publisher)
Created2017
Description
Many animals thermoregulate to maximize performance. However, interactions with other animals, such as competitors or predators, limit access to preferred microclimates. For instance, an animal may thermoregulate poorly when fighting rivals or avoiding predators. However, the distribution of thermal resources should influence how animals perceive and respond to risk. When thermal resources are concentrated in space, individuals compete for access, which presumably reduces the thermoregulatory performance while making their location more predictable to predators. Conversely, when thermal resources are dispersed, several individuals can thermoregulate effectively without occupying the same area. Nevertheless, interactions with competitors or predators impose a potent stress, often resulting in both behavioral and physiological changes that influence thermoregulation. To assess the costs of intraspecific competition and predation risk during thermoregulation, I measured thermoregulation, movement, and hormones of male lizards (Sceloporus jarrovi) in experiment landscapes, with clumped to patchy distributions of microclimates. I found lizards aggressively competed for access to microclimates, with larger males gaining priority access when thermal resources were aggregated. Competition reduced thermoregulatory performance, increased movements, and elevated plasma corticosterone in large and small males. However, the magnitude of these responses decreased as the patchiness of the thermal environment increased. Similarly, under simulated predation risk, lizards reduced thermoregulatory performance, decreased movements, and elevated plasma corticosterone. Again, with the magnitude of these responses decreased with increasing thermal patchiness. Interestingly, even without competitors or predators, lizards in clumped arenas moved greater distances and circulated more corticosterone than did lizards in patchy arenas, indicating the thermal quality of the thermal landscape affected the energetic demands on lizards. Thus, biologists should consider species interactions and spatial structure when modeling impacts of climate change on thermoregulation.
ContributorsRusch, Travis W (Author) / Angilletta, Michael (Thesis advisor) / Sears, Mike (Committee member) / DeNardo, Dale (Committee member) / Deviche, Pierre (Committee member) / McGraw, Kevin (Committee member) / Arizona State University (Publisher)
Created2017
Description
Desert environments provide considerable challenges to organisms because of high temperatures and limited food and water resources. Accordingly, desert species have behavioral and physiological traits that enable them to cope with these constraints. However, continuing human activity as well as anticipated further changes to the climate and the vegetative community pose a great challenge to such balance between an organism and its environment. This is especially true in the Arabian Desert, where climate conditions are extreme and environmental disturbances substantial. This study combined laboratory and field components to enhance our understanding of dhub (Uromastyx aegyptius) ecophysiology and determine whether habitat protection influences dhub behavior and physiology.
Results of this study showed that while body mass and body condition consistently diminished as the active season progressed, they were both greater in protected habitats compared to non-protected habitats, regardless of season. Dhubs surface activity and total body water decreased while evaporative water loss and body temperature increased as the active season progressed and ambient temperature got hotter. Total body water was also significantly affected by habitat protection.
Overall, this study revealed that, while habitat protection provided more vegetation, it had little effect on seasonal changes in surface activity. While resource availability in protected areas might allow for larger dhub populations, unprotected areas showed similar body morphometrics, activity, and body temperatures. By developing an understanding of how different coping strategies are linked to particular ecological, morphological, and phylogenetic traits, we will be able to make more accurate predictions regarding the vulnerability of species. By combining previous studies pertaining to conservation of protected species with the results of my study, a number of steps in ecosystem management are recommended to help in the preservation of dhubs in the Kuwaiti desert.
Results of this study showed that while body mass and body condition consistently diminished as the active season progressed, they were both greater in protected habitats compared to non-protected habitats, regardless of season. Dhubs surface activity and total body water decreased while evaporative water loss and body temperature increased as the active season progressed and ambient temperature got hotter. Total body water was also significantly affected by habitat protection.
Overall, this study revealed that, while habitat protection provided more vegetation, it had little effect on seasonal changes in surface activity. While resource availability in protected areas might allow for larger dhub populations, unprotected areas showed similar body morphometrics, activity, and body temperatures. By developing an understanding of how different coping strategies are linked to particular ecological, morphological, and phylogenetic traits, we will be able to make more accurate predictions regarding the vulnerability of species. By combining previous studies pertaining to conservation of protected species with the results of my study, a number of steps in ecosystem management are recommended to help in the preservation of dhubs in the Kuwaiti desert.
ContributorsAl-Sayegh, Mohammed (Author) / DeNardo, Dale (Thesis advisor) / Angilletta, Michael (Committee member) / Smith, Andrew (Committee member) / Sabo, John (Committee member) / Majeed, Qais (Committee member) / Arizona State University (Publisher)
Created2017
Description
Deserts are natural laboratories in which to study the acute effects of extreme heat and aridity on animal physiology, as well as the physiological adaptations that these animals develop to survive. For small, endothermic fliers in the desert, heat balance and water balance are challenging due to high surface area to volume ratios and the additional heat load imposed as a result of endothermy. Much of the previous fifty years of thermo- and hydroregulation research has focused on larger, charismatic megafauna; extremophiles; or only part of the heat or water balance story. Here, I calculate the first heat budget for an important desert bee, Centris caesalpiniae. As is common in many mammals, avians, and other flying insects, I find that C. caesalpiniae males use an appendage – in this case the abdomen – as a convective radiator to dispel excess heat produced by the thoracic flight muscles at high air temperatures. The few heat budgets measured for flying endotherms are conducted in the shade so as to eliminate the effects of solar radiation. To further refine the accuracy of my heat budget model, I consider how heat gain from solar radiation affects the thermal balance of flying desert endotherms. To this effect, I find that solar radiation contributes 43 to 54% of the total heat gain of a desert Centris pallida bee. I additionally show that large morph male, small morph male, and female C. pallida, use different thermoregulatory tactics while flying in shaded versus sunny conditions; large males and females rely on the abdominal convector in the sun while small morph males increase convective conductance in the sun, but do not use an abdominal convector. Given that evaporative cooling was not a significant part of the heat budget for neither C. caesalpiniae nor C. pallida, I investigated the effects of water loss rates and critical thermal maxima during flight on duration of activity period. I found that male C. caesalpiniae limited their activity period due to high water loss rates rather than overheating, and that Centris critical water contents ranged from 48 to 54%, limiting flight activity to about 3 hours.
ContributorsJohnson, Meredith Grace (Author) / Harrison, Jon F. (Thesis advisor) / Buchmann, Stephen (Committee member) / DeNardo, Dale (Committee member) / Dillon, Michael (Committee member) / Arizona State University (Publisher)
Created2023