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Description
ABSTRACT The elephant tree, Bursera microphylla, is at the northern limit of its range in central Arizona. This species is sensitive to frost damage thus limiting its occurrence in more northern areas of the southwest. Marginal populations of B. microphylla are found in mountain ranges of Central Arizona and are known to occur in the rugged mountain range system of the South Mountain Municipal Park (SMMP). Little is known of the distribution of this species within the park and details relevant to the health of both individual plants and the population such as diameter and number of trunks, height, and presence of damage have not been examined. This study was designed, in part, to test the hypothesis that favorable microhabitats at SMMP are created by particular combinations of abiotic features including aspect, slope, elevation and solar radiation. Data on abiotic factors, as well as specific individual plant locations and characteristics were obtained for 100 individuals. Temperature data was collected in vertical transects at different altitudinal levels. Some of these data were used in spatial analyses to generate a habitat suitability model using GIS software. Furthermore, collected data was analyzed using Matlab© software to identify potential trends in the variation of morphological traits. In addition, for comparative purposes similar information at one hundred computer-generated randomly chosen points throughout SMMP was obtained. The GIS spatial analyses indicated that aspect, slope, elevation, and relative solar radiance are strongly associated as major climatic components of the microhabitat of B. microphylla. Temperature data demonstrated that there are significant differences in ambient temperature among different altitudinal gradients with middle elevations being more favorable. Furthermore, analyses performed using Matlab© to explore trends of elevation as a factor indicated that multiple trunk plants are more commonly found at higher elevations than single trunk plants, there is a positive correlation of trunk diameter with elevation, and that canopy volume has a negative correlation with respect to elevation. It was concluded that microhabitats where B. microphylla occurs at the northern limit of its range require a particular combination of abiotic features that can be easily altered by climatic changes.
ContributorsCordova, Cesar, M.S (Author) / Steele, Kelly P. (Thesis advisor) / Tridane, Abdessaman (Committee member) / Miller, William (Committee member) / Brady, Ward (Committee member) / Arizona State University (Publisher)
Created2011
Description
As the planet is rapidly urbanizing, understanding the ecological effects of urbanization is a grand challenge for modern biology. For example, increased city temperatures known as the urban heat island effect, disproportionately impact nocturnal taxa and this consideration is widely overlooked. Slight shifts in the thermal microclimate have a cascade of ramifications that directly impact species density and distribution. Animal behavior is a trait that may explain why some species thrive after urbanization when others go locally extinct. In this study I followed 22 adult females of the western black widow, Latrodectus hesperus, from both urban and undisturbed Sonoran Desert habitats. First, I began looking for differences between urban and desert spiders under field conditions: boldness, voracity, web size and body condition. Both urban and desert spiders were then brought to the laboratory to see how their behavior changed. I found no behavioral differences between urban and desert spiders in the field or the laboratory. I did find that spider behavior differed between the field and the laboratory. Specifically, boldness in the laboratory was significantly lower compared to the field. Voracity was more repeatable in the laboratory versus the field, and boldness was strongly positively correlated with voracity in the laboratory, but not in the field. These behavioral shifts from the field to the laboratory favor the conclusion that black widow behavior is highly plastic and context dependent. Lastly, I monitored web temperature of black widow microhabitat continuously for an entire year using iButton data loggers. I found microhabitat temperatures differences between urban and desert sites were greatest at night and absent during the daytime. I uncovered a seasonal effect with the highest magnitude temperature difference occurring during the springtime. Additionally, behavior was significantly correlated with field temperatures; the boldest spiders come from the warmest webs. However, I found little evidence that temperature predicts spider body condition or voracity, and body condition does not predict its behavioral expression. My results highlight the importance of studying animal behavior to increase understanding of the factors that shape distribution and density in a lethal pest species.
ContributorsClark, Ryan Carter (Author) / Johnson, James C (Thesis advisor) / Bang, Christofer (Thesis advisor) / Sullivan, Brian (Committee member) / Arizona State University (Publisher)
Created2021