Term of Award

Summer 2019

Degree Name

Master of Science in Biology (M.S.)

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Committee Chair

Stephen Greiman

Committee Member 1

John Harrison

Committee Member 2

Joshua Gibson


The intestinal microbiome of mammals plays a significant role in host health and response to environmental stimuli and can include both beneficial native bacteria as well as parasitic worms. In this study, I examined the intestinal cestode and bacterial communities of two closely related species of shrew, Sorex monticola and Sorex cinereus, over a six month period in 2016. Specimens were collected approximately every three weeks from May to October from the Sangre de Cristo Mountains in Cowles, New Mexico. A total of 79 shrews were prepared with the gastrointestinal tracts removed and flash-frozen in liquid nitrogen. An additional 9 whole frozen samples were obtained from the Museum of Southwestern Biology, which were collected from the same area in September 2009. I extracted DNA from the whole GI tract, and amplified 3 loci (28S rRNA, 16S mtDNA, 16S rRNA) using one-step PCR amplification and sequencing on the Illumina MiSeq system 28S rRNA gene. On average, shrews were infected by 6 cestode genera and colonized by an average of 11 bacterial phyla, with Lineolepis and Epsilonbacteraeota being the most abundant, respectively. I tested both environmental and host-related metrics and found that the cestode infections of S. monticola and S. cinereus are most significantly affected by host species, host weight, and time of year, and bacterial community compositions were most significantly affected by time of year and host weight with some effect from host species and collection locality. Variation across weight and time likely reflects variations in the shrews’ arthropod diet. Cestode variation across host species reflects their high host specificity. Bacterial variation in locality reflects the high degree of individual variation of intestinal microbiomes. Variation with respect to host species may be due to a difference in inflammatory response or an artefact of uneven sample sizes.

Research Data and Supplementary Material