Theses and Dissertations

Issuing Body

Mississippi State University


Jordan, Heather

Committee Member

Brooks, Christopher P.

Committee Member

Barton, Brandon

Date of Degree


Document Type

Graduate Thesis - Open Access


Biological Sciences

Degree Name

Master of Science


College of Arts and Sciences


Department of Biological Sciences


The microorganisms that live in and on a host (the microbiome) influence host phenotype, health, and behavior in plants and animals. However, the effects of the host and environment on the composition of microbiome communities are unclear. This is especially true in arid and semi-arid environments such as deserts that filter many microorganisms. This study investigated variation in phyllosphere microbiotal bacterial assemblages of prickly pear cactus (Opuntia) across differing spatial scales, ecoregions, and taxa throughout Texas at two timepoints. I expected bacterial assemblages to differ significantly among Texas ecoregions and among species. Results support significant influences on bacterial assemblage composition including ecoregion, taxonomy, and potentially seasonal time of sampling. The dry season timepoint yielded high microbial diversity and abundance across species and ecoregions, with different species and ecoregions harboring unique microbial communities. The rainy season timepoint yielded significantly lower levels of microbial diversity and abundance across species and ecoregions.