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- Genre: Academic theses
Description
Though it is a widespread adaptation in humans and many other animals, parental care comes in a variety of forms and its subtle physiological costs, benefits, and tradeoffs related to offspring are often unknown. Thus, I studied the hydric, respiratory, thermal, and fitness dynamics of maternal egg-brooding behavior in Children's pythons (Antaresia childreni). I demonstrated that tight coiling detrimentally creates a hypoxic developmental environment that is alleviated by periodic postural adjustments. Alternatively, maternal postural adjustments detrimentally elevate rates of egg water loss relative to tight coiling. Despite ventilating postural adjustments, the developmental environment becomes increasingly hypoxic near the end of incubation, which reduces embryonic metabolism. I further demonstrated that brooding-induced hypoxia detrimentally affects offspring size, performance, locomotion, and behavior. Thus, parental care in A. childreni comes at a cost to offspring due to intra-offspring tradeoffs (i.e., those that reflect competing offspring needs, such as water balance and respiration). Next, I showed that, despite being unable to intrinsically produce body heat, A. childreni adjust egg-brooding behavior in response to shifts in nest temperature, which enhances egg temperature (e.g., reduced tight coiling during nest warming facilitated beneficial heat transfer to eggs). Last, I demonstrated that A. childreni adaptively adjust their egg-brooding behaviors due to an interaction between nest temperature and humidity. Specifically, females' behavioral response to nest warming was eliminated during low nest humidity. In combination with other studies, these results show that female pythons sense environmental temperature and humidity and utilize this information at multiple time points (i.e., during gravidity [egg bearing], at oviposition [egg laying], and during egg brooding) to enhance the developmental environment of their offspring. This research demonstrates that maternal behaviors that are simple and subtle, yet easily quantifiable, can balance several critical developmental variables (i.e., thermoregulation, water balance, and respiration).
ContributorsStahlschmidt, Zachary R (Author) / DeNardo, Dale F (Thesis advisor) / Harrison, Jon (Committee member) / McGraw, Kevin (Committee member) / Rutowski, Ronald (Committee member) / Walsberg, Glenn (Committee member) / Arizona State University (Publisher)
Created2011
Description
Human-induced rapid environmental change (HIREC) influences nearly all of Earth's ecosystems through processes such as urbanization. Previous studies have found that urbanization influences biodiversity patterns, often yielding an increase in the abundance of a few urban-adapted taxa at the expense of native species diversity. The western black widow spider, Latrodectus hesperus, is a medically-important pest species that often forms dense urban subpopulations (i.e., infestations) relative to the low-density subpopulations found throughout undisturbed, desert habitat. Here, I employ field and laboratory studies to examine the population ecology and stoichiometry of this urban pest to increase our understanding of the mechanisms underlying its success. The population ecology of ten black widow subpopulations spread across metropolitan Phoenix, AZ was examined during the peak breeding season (June-August). This study revealed that arthropod prey abundance, female mass and population density of females showed significant spatial variation across the ten subpopulations. Additionally, prey abundance and foraging success, measured as the number of carcasses found in webs, were a strong determinant of female mass and population density within each subpopulation. To test the mechanisms that drive black widow infestations, I used ecological stoichiometry to examine the nutrient (nitrogen and phosphorus) composition of spiders and arthropod prey from urban habitat, desert habitat and a laboratory diet regime. These studies revealed that (1) spiders are more nutrient rich than cricket prey in the field, (2) spider subpopulations exhibit significant spatial variation in their nitrogen composition, (3) nutrient composition of urban spider subpopulations does not differ significantly from Sonoran desert subpopulations, (4) laboratory-reared spiders fed a diet of only laboratory-reared crickets are more nitrogen and phosphorus limited than field-captured spiders, and (5) cannibalism by laboratory-reared spiders alleviated phosphorus limitation, but not nitrogen limitation, when compared to field-captured spiders. This work highlights the need to examine the population ecology of species relationships, such as predator-prey dynamics, to fully understand the fecundity and population growth of urban pest species. Moreover, the integration of population ecology and stoichiometry illustrates the need to address mechanisms like nutrient limitation that may explain why urban pest populations thrive and native species diversity suffers following HIREC.
ContributorsTrubl, Patricia (Author) / Johnson, James C. (Thesis advisor) / Rutowski, Ronald (Thesis advisor) / McGraw, Kevin (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
Understanding why animals form social groups is a fundamental aim of sociobiology. To date, the field has been dominated by studies of kin groups, which have emphasized indirect fitness benefits as key drivers of grouping among relatives. Nevertheless, many animal groups are comprised of unrelated individuals. These cases provide unique opportunities to illuminate drivers of social evolution beyond indirect fitness, especially ecological factors. This dissertation combines behavioral, physiological, and ecological approaches to explore the conditions that favor group formation among non-kin, using as a model the facultatively social carpenter bee, Xylocopa sonorina. Using behavioral and genetic techniques, I found that nestmates in this species are often unrelated, and that non-kin groups form following extensive inter-nest migration.Group living may arise as a strategy to mitigate constraints on available breeding space. To test the hypothesis that nest construction is prohibitively costly for carpenter bees, I measured metabolic rates of excavating bees and used imaging techniques to quantify nest volumes. From these measurements, I found that nest construction is highly energetically costly, and that bees who inherit nests through social queuing experience substantial energetic savings. These costs are exacerbated by limitations on the reuse of existing nests. Using repeated CT scans of nesting logs, I examined changes in nest architecture over time and found that repeatedly inherited tunnels become indefensible to intruders, and are subsequently abandoned. Together, these factors underlie intense competition over available breeding space. The imaging analysis of nesting logs additionally revealed strong seasonal effects on social strategy, with social nesting dominating during winter. To test the hypothesis that winter social nesting arises from intrinsic physiological advantages of grouping, I experimentally manipulated social strategy in overwintering bees. I found that social bees conserve heat and body mass better than solitary bees, suggesting fitness benefits to grouping in cold, resource-scarce conditions. Together, these results suggest that grouping in X. sonorina arises from dynamic strategies to maximize direct fitness in response to harsh and/or competitive conditions. These studies provide empirical insights into the ecological conditions that favor non-kin grouping, and emphasize the importance of ecology in shaping sociality at its evolutionary origins.
ContributorsOstwald, Madeleine (Author) / Fewell, Jennifer H (Thesis advisor) / Amdam, Gro (Committee member) / Harrison, Jon (Committee member) / Pratt, Stephen (Committee member) / Kapheim, Karen (Committee member) / Arizona State University (Publisher)
Created2022
Description
Speciation, or the process by which one population diverges into multiple populations that can no longer interbreed with each other, has brought about the incredible diversity of life. Mechanisms underlying this process can be more visible in the early stages of the speciation process. The mechanisms that restrict gene flow in highly mobile species with no absolute barriers to dispersal, especially marine species, are understudied. Similarly, human impacts are reshaping ecosystems globally, and we are only just beginning to understand the implications of these rapid changes on evolutionary processes. In this dissertation, I investigate patterns of speciation and evolution in two avian clades: a genus of widespread tropical seabirds (boobies, genus Sula), and two congeneric passerine species in an urban environment (cardinals, genus Cardinalis). First, I explore the prevalence of gene flow across land barriers within species and between sympatric species in boobies. I found widespread evidence of gene flow over all land barriers and between 3 species pairs. Next, I compared the effects of urbanization on the spatial distributions of two cardinal species, pyrrhuloxia (Cardinalis sinuatus) and northern cardinals (Cardinalis cardinalis), in Tucson, Arizona. I found that urbanization has different effects on the spatial distributions of two closely related species that share a similar environmental niche, and I identified environmental variables that might be driving this difference. Then I tested for effects of urbanization on color and size traits of these two cardinal species. In both of these species, urbanization has altered traits involved in signaling, heat tolerance, foraging, and maneuverability. Finally, I tested for evidence of selection on the urban populations of both cardinal species and found evidence of both parallel selection and introgression between the species, as well as selection on different genes in each species. The functions of the genes that experienced positive selection suggest that light at night, energetics, and air pollution may have acted as strong selective pressures on these species in the past. Overall, my dissertation emphasizes the role of introgression in the speciation process, identifies environmental stressors faced by wildlife in urban environments, and characterizes their evolutionary responses to those stressors.
ContributorsJackson, Daniel Nelson (Author) / McGraw, Kevin J (Thesis advisor) / Amdam, Gro (Committee member) / Sweazea, Karen (Committee member) / Taylor, Scott (Committee member) / Arizona State University (Publisher)
Created2023
Description
Reproduction is energetically costly and seasonal breeding has evolved to capitalize on predictable increases in food availability. The synchronization of breeding with periods of peak food availability is especially important for small birds, most of which do not store an extensive amount of energy. The annual change in photoperiod is the primary environmental cue regulating reproductive development, but must be integrated with supplementary cues relating to local energetic conditions. Photoperiodic regulation of the reproductive neuroendocrine system is well described in seasonally breeding birds, but the mechanisms that these animals use to integrate supplementary cues remain unclear. I hypothesized that (a) environmental cues that negatively affect energy balance inhibit reproductive development by acting at multiple levels along the reproductive endocrine axis including the hypothalamus (b) that the availability of metabolic fuels conveys alterations in energy balance to the reproductive system. I investigated these hypotheses in male house finches, Haemorhous mexicanus, caught in the wild and brought into captivity. I first experimentally reduced body condition through food restriction and found that gonadal development and function are inhibited and these changes are associated with changes in hypothalamic gonadotropin-releasing hormone (GnRH). I then investigated this neuroendocrine integration and found that finches maintain reproductive flexibility through modifying the release of accumulated GnRH stores in response to energetic conditions. Lastly, I investigated the role of metabolic fuels in coordinating reproductive responses under two different models of negative energy balance, decreased energy intake (food restriction) and increased energy expenditure (high temperatures). Exposure to high temperatures lowered body condition and reduced food intake. Reproductive development was inhibited under both energy challenges, and occurred with decreased gonadal gene expression of enzymes involved in steroid synthesis. Minor changes in fuel utilization occurred under food restriction but not high temperatures. My results support the hypothesis that negative energy balance inhibits reproductive development through multilevel effects on the hypothalamus and gonads. These studies are among the first to demonstrate a negative effect of high temperatures on reproductive development in a wild bird. Overall, the above findings provide important foundations for investigations into adaptive responses of breeding in energetically variable environments.
ContributorsValle, Shelley (Author) / Deviche, Pierre (Thesis advisor) / McGraw, Kevin (Committee member) / Orchinik, Miles (Committee member) / Propper, Catherine (Committee member) / Sweazea, Karen (Committee member) / Arizona State University (Publisher)
Created2018
Description
Why do many animals possess multiple classes of photoreceptors that vary in the wavelengths of light to which they are sensitive? Multiple spectral photoreceptor classes are a requirement for true color vision. However, animals may have unconventional vision, in which multiple spectral channels broaden the range of wavelengths that can be detected, or in which they use only a subset of receptors for specific behaviors. Branchiopod crustaceans are of interest for the study of unconventional color vision because they express multiple visual pigments in their compound eyes, have a simple repertoire of visually guided behavior, inhabit unique and highly variable light environments, and possess secondary neural simplifications. I first tested the behavioral responses of two representative species of branchiopods from separate orders, Streptocephalus mackini Anostracans (fairy shrimp), and Triops longicaudatus Notostracans (tadpole shrimp). I found that they maintain vertical position in the water column over a broad range of intensities and wavelengths, and respond behaviorally even at intensities below those of starlight. Accordingly, light intensities of their habitats at shallow depths tend to be dimmer than terrestrial habitats under starlight. Using models of how their compound eyes and the first neuropil of their optic lobe process visual cues, I infer that both orders of branchiopods use spatial summation from multiple compound eye ommatidia to respond at low intensities. Then, to understand if branchiopods use unconventional vision to guide these behaviors, I took electroretinographic recordings (ERGs) from their compound eyes and used models of spectral absorptance for a multimodel selection approach to make inferences about the number of photoreceptor classes in their eyes. I infer that both species have four spectral classes of photoreceptors that contribute to their ERGs, suggesting unconventional vision guides the described behavior. I extended the same modeling approach to other organisms, finding that the model inferences align with the empirically determined number of photoreceptor classes for this diverse set of organisms. This dissertation expands the conceptual framework of color vision research, indicating unconventional vision is more widespread than previously considered, and explains why some organisms have more spectral classes than would be expected from their behavioral repertoire.
ContributorsLessios, Nicolas (Author) / Rutowski, Ronald L (Thesis advisor) / Cohen, Jonathan H (Thesis advisor) / Harrison, John (Committee member) / Neuer, Susanne (Committee member) / McGraw, Kevin (Committee member) / Arizona State University (Publisher)
Created2016
Description
Foraging has complex effects on whole-organism homeostasis, and there is considerable evidence that foraging behavior is influenced by both environmental factors (e.g., food availability, predation risk) and the physiological condition of an organism. The optimization of foraging behavior to balance costs and benefits is termed state-dependent foraging (SDF) while behavior that seeks to protect assets of fitness is termed the asset protection principle (APP). A majority of studies examining SDF have focused on the role that energy balance has on the foraging of organisms with high metabolism and high energy demands ("high-energy systems" such as endotherms). In contrast, limited work has examined whether species with low energy use ("low-energy systems" such as vertebrate ectotherms) use an SDF strategy. Additionally, there is a paucity of evidence demonstrating how physiological and environmental factors other than energy balance influence foraging behavior (e.g. hydration state and free-standing water availability). Given these gaps in our understanding of SDF behavior and the APP, I examined the state-dependency and consequences of foraging in a low-energy system occupying a resource-limited environment - the Gila monster (Heloderma suspectum, Cope 1869). In contrast to what has been observed in a wide variety of taxa, I found that Gila monsters do not use a SDF strategy to manage their energy reserves and that Gila monsters do not defend their energetic assets. However, hydration state and free-standing water availability do affect foraging behavior of Gila monsters. Additionally, as Gila monsters become increasingly dehydrated, they reduce activity to defend hydration state. The SDF behavior of Gila monsters appears to be largely driven by the fact that Gila monsters must separately satisfy energy and water demands with food and free-standing water, respectively, in conjunction with the timescale within which Gila monsters balance their energy and water budgets (supra-annually versus annually, respectively). Given these findings, the impact of anticipated changes in temperature and rainfall patterns in the Sonoran Desert are most likely going to pose their greatest risks to Gila monsters through the direct and indirect effects on water balance.
ContributorsWright, Christian (Author) / Denardo, Dale F. (Thesis advisor) / Harrison, Jon (Committee member) / McGraw, Kevin (Committee member) / Sullivan, Brian (Committee member) / Wolf, Blair (Committee member) / Arizona State University (Publisher)
Created2014
Description
Warning coloration deters predators from attacking prey that are defended, usually by being distasteful, toxic, or otherwise costly for predators to pursue and consume. Predators may have an innate response to warning colors or learn to associate them with a defense through trial and error. In general, predators should select for warning signals that are easy to learn and recognize. Previous research demonstrates long-wavelength colors (e.g. red and yellow) are effective because they are readily detected and learned. However, a number of defended animals display short-wavelength coloration (e.g. blue and violet), such as the pipevine swallowtail butterfly (Battus philenor). The role of blue coloration in warning signals had not previously been explicitly tested. My research showed in laboratory experiments that curve-billed thrashers (Toxostoma curvirostre) and Gambel's quail (Callipepla gambelii) can learn and recognize the iridescent blue of B. philenor as a warning signal and that it is innately avoided. I tested the attack rates of these colors in the field and blue was not as effective as orange. I concluded that blue colors may function as warning signals, but the effectiveness is likely dependent on the context and predator.
Blue colors are often iridescent in nature and the effect of iridescence on warning signal function was unknown. I reared B. philenor larvae under varied food deprivation treatments. Iridescent colors did not have more variation than pigment-based colors under these conditions; variation which could affect predator learning. Learning could also be affected by changes in appearance, as iridescent colors change in both hue and brightness as the angle of illuminating light and viewer change in relation to the color surface. Iridescent colors can also be much brighter than pigment-based colors and iridescent animals can statically display different hues. I tested these potential effects on warning signal learning by domestic chickens (Gallus gallus domesticus) and found that variation due to the directionality of iridescence and a brighter warning signal did not influence learning. However, blue-violet was learned more readily than blue-green. These experiments revealed that the directionality of iridescent coloration does not likely negatively affect its potential effectiveness as a warning signal.
Blue colors are often iridescent in nature and the effect of iridescence on warning signal function was unknown. I reared B. philenor larvae under varied food deprivation treatments. Iridescent colors did not have more variation than pigment-based colors under these conditions; variation which could affect predator learning. Learning could also be affected by changes in appearance, as iridescent colors change in both hue and brightness as the angle of illuminating light and viewer change in relation to the color surface. Iridescent colors can also be much brighter than pigment-based colors and iridescent animals can statically display different hues. I tested these potential effects on warning signal learning by domestic chickens (Gallus gallus domesticus) and found that variation due to the directionality of iridescence and a brighter warning signal did not influence learning. However, blue-violet was learned more readily than blue-green. These experiments revealed that the directionality of iridescent coloration does not likely negatively affect its potential effectiveness as a warning signal.
ContributorsPegram, Kimberly Vann (Author) / Rutowski, Ronald L (Thesis advisor) / Hoelldobler, Berthold (Committee member) / Liebig, Juergen (Committee member) / McGraw, Kevin (Committee member) / Smith, Brian H. (Committee member) / Arizona State University (Publisher)
Created2015
Description
The Great Bustard (Otis tarda) is an iconic species of the temperate grasslands of Europe and Asia, a habitat that is among the least protected ecosystems in the world. A distinct subspecies, the Asian Great Bustard (O. t. dybowskii), is poorly understood due to its wary nature and remote range in Siberia, Mongolia, and northern China. This subspecies is now endangered by rapid development.
Using satellite telemetry and remote sensing, I investigated three aspects of the Asian Great Bustard’s ecology critical to its conservation: migratory routes, migratory cues, and habitat use patterns. I found that Asian Great Bustards spent one-third of the year on a 2000 km migratory pathway, a distance twice as far as has previously been recorded for the species. Tracked individuals moved nomadically over large winter territories and did not repeat migratory stopovers, complicating conservation planning. Migratory timing was variable and migratory movements were significantly correlated with weather cues. Specifically, bustards migrated on days when wind support was favorable and temperature presaged warmer temperatures on the breeding grounds (spring) or advancing winter weather (fall). On the breeding grounds, Asian Great Bustards used both steppe and wheat agriculture habitat. All recorded reproductive attempts failed, regardless of habitat in which the nest was placed. Agricultural practices are likely to intensify in the coming decade, which would present further challenges to reproduction. The distinct migratory behavior and habitat use patterns of the Asian Great Bustard are likely adaptations to the climate and ecology of Inner Asia and underscore the importance of conserving these unique populations.
My research indicates that conservation of the Asian Great Bustard will require a landscape-level approach. This approach should incorporate measures at the breeding grounds to raise reproductive success, alongside actions on the migratory pathway to ensure appropriate habitat and reduce adult mortality. To secure international cooperation, I proposed that an increased level of protection should be directed toward the Great Bustard under the Convention on Migratory Species (CMS). That proposal, accepted by the Eleventh Conference of Parties to CMS, provides recommendations for conservation action and illustrates the transdisciplinary approach I have taken in this research.
Using satellite telemetry and remote sensing, I investigated three aspects of the Asian Great Bustard’s ecology critical to its conservation: migratory routes, migratory cues, and habitat use patterns. I found that Asian Great Bustards spent one-third of the year on a 2000 km migratory pathway, a distance twice as far as has previously been recorded for the species. Tracked individuals moved nomadically over large winter territories and did not repeat migratory stopovers, complicating conservation planning. Migratory timing was variable and migratory movements were significantly correlated with weather cues. Specifically, bustards migrated on days when wind support was favorable and temperature presaged warmer temperatures on the breeding grounds (spring) or advancing winter weather (fall). On the breeding grounds, Asian Great Bustards used both steppe and wheat agriculture habitat. All recorded reproductive attempts failed, regardless of habitat in which the nest was placed. Agricultural practices are likely to intensify in the coming decade, which would present further challenges to reproduction. The distinct migratory behavior and habitat use patterns of the Asian Great Bustard are likely adaptations to the climate and ecology of Inner Asia and underscore the importance of conserving these unique populations.
My research indicates that conservation of the Asian Great Bustard will require a landscape-level approach. This approach should incorporate measures at the breeding grounds to raise reproductive success, alongside actions on the migratory pathway to ensure appropriate habitat and reduce adult mortality. To secure international cooperation, I proposed that an increased level of protection should be directed toward the Great Bustard under the Convention on Migratory Species (CMS). That proposal, accepted by the Eleventh Conference of Parties to CMS, provides recommendations for conservation action and illustrates the transdisciplinary approach I have taken in this research.
ContributorsKessler, Aimee (Author) / Smith, Andrew T. (Thesis advisor) / Brown, David (Committee member) / Franklin, Janet (Committee member) / McGraw, Kevin (Committee member) / Wu, Jianguo (Committee member) / Arizona State University (Publisher)
Created2015