Reid, Mary L.Peralta Vázquez, Guadalupe Haydeé2018-05-082018-05-082018-05-04http://hdl.handle.net/1880/106622Phoresy, a commensal interaction where smaller organisms utilize dispersive hosts for transmission to new habitats, is expected to produce positive effects for symbionts and no effects for hosts, yet negative and positive effects have been documented. This poses the question of whether phoresy is indeed a commensal interaction and demands clarification. In bark beetles (Scolytinae), both effects are documented during reproduction and effects on hosts during the actual dispersal are largely unknown. In the present research, I investigated the ecological mechanisms that determine the net effects of the phoresy observed in mites and mountain pine beetles (MPB), Dendroctonus ponderosae Hopkins. Using flight mills, I found that MPB flight increased with beetle size and body condition but was not modified by mite abundance. Mites were initially more abundant on larger beetles in better condition, but their dispersal success was similar among all hosts. Host dispersal was costly for both host and mites. Beetles lost mass whereas mites exhibited mortality. In the second study, I determined the number and survivorship of all juvenile stages of MPB development and found neutral effects of mites. Although I found a negative effect of mite abundance despite a positive effect of mite presence during host larval stage, there were no further effects during subsequent stages of beetle development. Moreover, I did not find effects of mites on the number or quality of adult beetle offspring. When observing the distribution of phoretic mites and beetle hosts in the field, I found that the range-expanding behavior of MPB might determine symbiont loss at the leading front of beetle expansion. Three mites were common: Tarsonemus ips, Proctolaelaps subcorticalis, and Trichouropoda australis. Of these species, only T. ips was prevalent among all sites. However, both total mite abundance, considering all three species together, and T. ips abundance alone were comparatively lower in the new area of MPB expansion. In addition, beetle body condition was similar in both historical and new areas of MPB distribution. Given the results, MPB and its phoretic mites sustain a commensalism and the lower distribution of mites may be a consequence of MPB outbreak dynamics.engUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.Mountain pine beetlePhoretic mitesFlight millCommensalismWestern CanadaForest pestTarsonemus ipsDendroctonus ponderosaePhoresyBark beetlesPhoretic symbiontsOutbreak dynamicsForestry and WildlifeBiologyEcologyEntomologydoctoral thesis10.11575/PRISM/31904