Bracted twistflower (Streptanthus bracteatus): The ecology of a rare Texas endemic

dc.contributor.advisorVan Auken, Oscar W.
dc.contributor.authorLeonard, Wendy Jae
dc.contributor.committeeMemberBush, Janis K.
dc.contributor.committeeMemberSponsel, Valerie M.
dc.date.accessioned2024-02-12T14:53:45Z
dc.date.available2024-02-12T14:53:45Z
dc.date.issued2010
dc.descriptionThis item is available only to currently enrolled UTSA students, faculty or staff. To download, navigate to Log In in the top right-hand corner of this screen, then select Log in with my UTSA ID.
dc.description.abstractThe bracted twistflower (Streptanthus bracteatus), a member of the Brassicaceae (mustard) family, is a rare endemic of the Edward's Plateau ecoregion of Texas. There appear to be many factors affecting its distribution. This study examined plants in a controlled environment and in the field. Factors examined in this study included seed dormancy, light levels, soil nutrients, herbivory, soil water content, and soil depth. Plant response variables were shoot height (cm), number of leaves, basal diameter (mm), diameter of basal rosette (cm), above and belowground dry mass, and total dry mass (g). The light experiment demonstrated that plants responded positively to higher light levels for basal diameter. Plants responded better to higher levels of soil nutrients but the response was minimal. The herbivory experiments consisted of simulated and actual herbivory treatments. Plants showed no clear response to simulated herbivory. However, in the field, herbivory showed negative effects on bracted twistflower by a large herbivore, likely white tailed deer (Odocoileus virginianus). Plants in the full sun exclosures had higher dry mass than plants in the full sun without exclosures. Full sun plants in the exclosure had higher dry mass than shaded plants in exclosures. Populations at two field sites, Eisenhower Park and Rancho Diana Natural Area, both located in Bexar County, were monitored. Response of plants at Eisenhower Park to light levels, soil moisture, and soil depth were examined. No significant linear correlations were found for plant responses to light levels and soil water content. However, there was a positive relationship between soil depth and number of leaves, shoot height, basal diameter, and number of flowers. Plants at Rancho Diana showed a positive response in terms of shoot height and basal diameter to increasing soil water content.
dc.description.departmentIntegrative Biology
dc.format.extent102 pages
dc.format.mimetypeapplication/pdf
dc.identifier.isbn9781124385341
dc.identifier.urihttps://hdl.handle.net/20.500.12588/4383
dc.languageen
dc.subjectBracted twistflower
dc.subjectendemic
dc.subjectrare wildflower
dc.subjectStreptanthus
dc.subjectStreptanthus bracteatus
dc.subjectTexas endemic wildflower
dc.subject.classificationEcology
dc.subject.classificationBotany
dc.titleBracted twistflower (Streptanthus bracteatus): The ecology of a rare Texas endemic
dc.typeThesis
dc.type.dcmiText
dcterms.accessRightspq_closed
thesis.degree.departmentIntegrative Biology
thesis.degree.grantorUniversity of Texas at San Antonio
thesis.degree.levelMasters
thesis.degree.nameMaster of Science

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