Theses and Dissertations
This collection includes both ASU Theses and Dissertations, submitted by graduate students, and the Barrett, Honors College theses submitted by undergraduate students.
Displaying 1 - 5 of 5
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- All Subjects: Ecology
- Creators: DeNardo, Dale F
- Creators: Ferry, Lara
Description
The bull shark, Carcharhinus leucas, is a large species that it is commonly distributed worldwide in tropical and subtropical waters. Despite the bull sharks global distribution, little is known about its life history. In particular, the limited reproductive information suggests the bull shark is placental viviparous, assumed to have a biennial cycle, and that newborn pup nurseries are near the coast. In order to conserve and protect any species, an understanding of the habitats where reproductive events occur is needed. In order to better understand the habitat use in Biscayne bay, Fla, and whether certain areas are critical during the reproductive cycle of bull sharks, I will evaluate circulating levels of the hormones progesterone, estradiol, and testosterone using radioimmunoassay. These samples were collected by the University of Miami opportunistically between 2012-2020 shipped to Arizona State University, where they were analyzed. For my study a total of 73 mature samples, 27 females and 46 males, were collected over the sampling period. The results indicated that Biscayne bay is an important gestation area for bull sharks. The hormonal trends for males and females demonstrated an interesting reproductive cycle, which were further supported through other placental viviparous reproductive patterns. Females had a low level of estradiol throughout most of the year, besides in the summer where there were no sharks in the bay due to movement to estuaries. During their return to the bay, there was a peak in progesterone indicating early pregnancy. Male testosterone levels indicated that there was a production in sperm right before females speculated peak in estradiol.
ContributorsJara-Aguirre, Nisi G (Author) / Sulikowski, James (Thesis director) / Ferry, Lara (Committee member) / School of Life Sciences (Contributor) / Department of Psychology (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
Environmental variation impacts physiological performance in animals. As a result, many animals thermoregulate to buffer unfavorable thermal variation in their environments. Animals are only expected to thermoregulate when the benefits outweigh the costs, although both are difficult to quantify. I examined how habitats and organismal factors shape thermoregulation and physiological performance in lizards. I found that habitat structure shapes opportunities for thermoregulation in two species of Anolis lizards. In dense tropical rainforests where there is low habitat heterogeneity, the range of available microclimates is narrow. Consequently, lizards in the tropics tend to be thermal specialists – performing best over a narrow range of temperatures. This phenotype should lead to decreased performance under climate warming. I then investigated the relationship between body condition, feeding, and thermoregulation in Yarrow’s spiny lizards (Sceloporus jarrovii) using lab- and field-based experiments. In the lab experiment, when lizards were observed in an artificial thermal gradient, neither body condition nor feeding status influenced the mean body temperature. When simulated costs of thermoregulation were higher, all lizards reduced thermoregulation similarly. However, when lizards were observed in an outdoor thermal arena, individuals with lower body condition decreased thermoregulatory performance, resulting in a lower mean body temperature. Animals with poor body condition may face greater risk of predation when thermoregulating. Finally, I conducted a comparative analysis to quantify relationships between the potential for thermoregulatory performance and empirical measures of productivity (i.e., growth rates and reproductive output) in lizard populations. A model that assumes lizards are active whenever preferred temperatures were available overestimated the duration that a lizard could maintain a preferred body temperature. As such, studies equating predicted thermoregulatory performance with fitness in the context of climate change should be interpreted cautiously. Overall, environmental factors and organismal traits shape the thermoregulatory behavior of animals, ultimately affecting their physiological performance and fitness. Biologists should consider these relationships when modeling the impacts of climate change on future performance.
ContributorsNeel, Lauren (Author) / Angilletta, Michael J (Thesis advisor) / Bateman, Heather L (Committee member) / DeNardo, Dale F (Committee member) / Sears, Michael W (Committee member) / Arizona State University (Publisher)
Created2023
Description
The Northwest (NW) Atlantic porbeagle Lamna nasus is overfished and captured as bycatch in fisheries within the region. A comprehensive understanding of the population’s life history (e.g., reproduction) and habitat use, and the impact of capture with different gear types (e.g., post-release mortality) is needed to ensure effective fisheries management plans, develop bycatch mitigation strategies, and support stock recovery. This research used satellite tagging technologies to address gaps in knowledge needed to support management and conservation decisions for the NW Atlantic porbeagle. I provided the first estimate of post-release survival and recovery periods for immature porbeagles captured with rod-and-reel. Although survival was high (100%), juvenile porbeagles exhibited a recovery period in surface waters that may make them vulnerable to further fishing interactions. Next, I described the vertical habitat use of young porbeagles to recommend possible fishing modifications to reduce risk of capture. Young porbeagles spent more time in surface waters during summer compared to fall and during the night compared to day, suggesting that risk of capture may be reduced by setting gear deeper during summer and at night when this life stage’s behavior is reduced to the upper water column. Then, I provided an analysis of the seasonal and life stage-based habitat use of porbeagles. Space use was concentrated in continental shelf waters around Cape Cod, Massachusetts regardless of season and life stage. Given the relatively small and static high occupancy area overlaps with a high concentration of fishing activity, this region could be considered for spatial management of the NW Atlantic porbeagle. Finally, I used ultrasonography and satellite tagging to describe the three-dimensional habitat use of gravid porbeagles for the first time. Gravid porbeagles demonstrated seasonal differences in horizontal and vertical habitat use but spent most of the pupping season in waters southeast of Cape Cod or on Georges Bank, suggesting this region may be serving as a pupping ground for at least a portion of this population. Conservation efforts should focus on these important habitats to protect the next generation of porbeagles.
ContributorsAnderson, Brooke Nicole (Author) / Ferry, Lara (Thesis advisor) / Bowlby, Heather (Committee member) / Hammerschlag, Neil (Committee member) / Kang, Yun (Committee member) / Saul, Steven (Committee member) / Sulikowski, James (Committee member) / Arizona State University (Publisher)
Created2024
Description
Sexual and social signals have long been thought to play an important role in speciation and diversity; hence, investigations of intraspecific communication may lead to important insights regarding key processes of evolution. Though we have learned much about the control, function, and evolution of animal communication by studying several very common signal types, investigating rare classes of signals may provide new information about how and why animals communicate. My dissertation research focused on rapid physiological color change, a rare signal-type used by relatively few taxa. To answer longstanding questions about this rare class of signals, I employed novel methods to measure rapid color change signals of male veiled chameleons Chamaeleo calyptratus in real-time as seen by the intended conspecific receivers, as well as the associated behaviors of signalers and receivers. In the context of agonistic male-male interactions, I found that the brightness achieved by individual males and the speed of color change were the best predictors of aggression and fighting ability. Conversely, I found that rapid skin darkening serves as a signal of submission for male chameleons, reducing aggression from winners when displayed by losers. Additionally, my research revealed that the timing of maximum skin brightness and speed of brightening were the best predictors of maximum bite force and circulating testosterone levels, respectively. Together, these results indicated that different aspects of color change can communicate information about contest strategy, physiology, and performance ability. Lastly, when I experimentally manipulated the external appearance of chameleons, I found that "dishonestly" signaling individuals (i.e. those whose behavior did not match their manipulated color) received higher aggression from unpainted opponents. The increased aggression received by dishonest signalers suggests that social costs play an important role in maintaining the honesty of rapid color change signals in veiled chameleons. Though the color change abilities of chameleons have interested humans since the time of Aristotle, little was previously known about the signal content of such changes. Documenting the behavioral contexts and information content of these signals has provided an important first step in understanding the current function, underlying control mechanisms, and evolutionary origins of this rare signal type.
ContributorsLigon, Russell (Author) / McGraw, Kevin J. (Committee member) / DeNardo, Dale F (Committee member) / Karsten, Kristopher B (Committee member) / Rutowski, Ronald L (Committee member) / Deviche, Pierre (Committee member) / Arizona State University (Publisher)
Created2015
Description
Though the connection between terrestrial riparian consumers and the adjacent aquatic food web has been well-studied in a variety of systems, gaps with respect to several habitats remain. The Colorado River Basin represents many of these untested habitat characteristics: it contains large, controlled rivers in an arid environment that are often canyon-bound. These characteristics, however, are not unique to the Colorado River Basin. Dams and arid lands are becoming increasingly common around the world, stressing the importance of understanding the function of riparian areas within the Colorado River Basin and basins like it. Stable isotopes, including the more recent application of deuterium, can be used to elucidate trophic linkages between rivers and their riparia. Though dams may harm aquatic insect populations, it is possible that they also make aquatic insects a stable, constant food source to the riparian biological community. This dissertation demonstrates that aquatic emergent insects are a reliable, and therefore important, food source for arid land riparian consumers along regulated rivers. However, the importance of aquatic emergent insects to riparian consumers may vary across sites, even within the same river basin. To explore this variation, the diet of a common riparian lizard species Urosaurus ornatus (Ornate Tree Lizard) can be used as an indicator of cross-ecosystem connectivity. This dissertation demonstrates linkages between two differing river segments and U. ornatus, showcasing its ability as an indicator of connectivity across a diversity of systems. Within the Colorado River Basin, the Grand Canyon provides an opportunity to study a variety of riparian consumers across a gradient of habitat parameters and dam effects. This dissertation demonstrates the manifold connections between large, regulated rivers and arid riparian consumers, ranging from lizards, to bats, to, for the first time, mice. Monsoons have differing effects on river-riparian communities in this basin, potentially related to intact tributary confluences. Lastly, this dissertation demonstrates that hydropeaking reduces river-riparia connectivity by reducing aquatic insect emergence. This dissertation seeks to improve understanding of the linkages between river and their riparia to aid in the management of arid riparian areas affected by dams worldwide.
ContributorsLupoli, Christina Alexandra (Author) / Sabo, John L (Thesis advisor) / DeNardo, Dale F (Committee member) / Kennedy, Theodore A (Committee member) / Muehlbauer, Jeffrey D (Committee member) / Yackulic, Charles B (Committee member) / Arizona State University (Publisher)
Created2021