Host and Parasite Interactions Among Three Symbionts: Pocket Gophers, Chewing Lice, and Endosymbiotic Bacteria.
Date of Award
Doctor of Philosophy (PhD)
Mark S. Hafner
This study investigates the patterns of cophylogeny documented between pocket gophers (Rodentia: Geomyidae) and their ectoparasitic chewing lice (Phthiraptera: Trichodectidae). The first two chapters investigate the mechanisms that reinforce cospeciation in this system. Chapter one examines whether mammalian hair diameter is a resource tracked by chewing lice, and thus reinforces the patterns of cospeciation. I found that hair diameter of pocket gophers is correlated with gopher body size and the body size of the ectoparasitic chewing lice. Hair diameter also is correlated with size of the rostral groove, which chewing lice use to grasp hair shafts of pocket gophers. In chapter two I examine whether hair diameter is the resource by which coexisting chewing louse species partition available habitat. Although the pattern of spatial partitioning was clearly evident, hair diameter does not seem to be the mechanism by which lice partition their habitat. Alternative resources could include temperature, humidity, or the distribution of sebaceous glands throughout the gopher pelage. Chapters three, four, and five investigate the bacteria associated with the pocket gopher-chewing louse system. I used the culture-independent method of amplifying DNA sequences to determine the identification of bacteria extracted from samples of chewing lice. This method yielded approximately 35 distinct lineages of bacteria associated with this system. I also amplified DNA sequences of bacteria from the eggs of chewing lice to determine whether any bacteria were transferred vertically in insects through the eggs. Several species of bacteria were repeatedly seen in these amplifications, which could be explained by the incorporation of bacteria in the insect eggs. Further study would be required to provide conclusive evidence of direct vertical transmission of bacteria in chewing louse eggs. The final chapter of this dissertation looks in detail at two groups of bacteria associated with chewing lice (gamma-Proteobacteria and Staphylococcus species). Complete sequencing of the 16S rRNA gene demonstrated that multiple species of both groups are associated with the pocket gopher-chewing louse system. Studies of cophylogeny between the species of Staphylococcus and their hosts were inconclusive and require more intensive taxon sampling.
Reed, David Lee, "Host and Parasite Interactions Among Three Symbionts: Pocket Gophers, Chewing Lice, and Endosymbiotic Bacteria." (2000). LSU Historical Dissertations and Theses. 7384.