Dissertation Information for Tammy Elaine TintjerNAME:
DEGREE:
DISCIPLINE:
SCHOOL: ADVISORS: COMMITTEE MEMBERS: MPACT Status: Incomplete - Not_Inspected Title: Horizontal and vertical transmission in the host-parasite interaction Elymus hystrix infected with Epichloe elymi Abstract: Why some parasites harm their hosts while others evolve to become less harmful or even beneficial may be determined by the parasite's mode of transmission to new hosts. Models predicting the effects of horizontal transmission on virulence, a parasite-induced reduction in host fitness, typically assume the traits are positively correlated. On the other hand, vertical transmission to host's offspring is generally assumed to lead to a reduction in virulence compared to horizontal transmission because both partners benefit from an increase in host reproduction. My research addresses the potential for evolution of the host--parasite interaction and the effects of vertical and horizontal transmission of a plant parasite, the fungal endophyte Epichloƫ elymi , on its host grass, Elymus hystrix . I documented that this fungal endophyte spans a continuum from primarily vertical to primarily horizontal transmission in both natural and experimental populations. In addition, when I controlled the genetic background of the host plant and the fungal endophyte, I found that both partners contributed to the expression of the endophyte's mode of transmission. Given this genetic variation, there is potential for this association to coevolve. I also found that when the fungal endophyte transmits horizontally it is more harmful to its host than when it transmits vertically to offspring. While horizontal transmission directly reduces host reproduction, it also indirectly reduces host growth, reproduction and survival, as well as resistance to host enemies. Epichloƫ elymi endophytes with little horizontal transmission have beneficial effects on their hosts by increasing plant size and reproduction compared to uninfected plants. These results demonstrate a genetic correlation between parasite transmission mode and host harm, indicating that these traits will evolve in concert. |
MPACT Scores for Tammy Elaine TintjerA = 0 Advisors and Advisees Graph |