Abstract
The causes and consequences of species’ distributional change has long been of interest in ecology, but it is of ever-pressing importance given increasingly rapid changes to both climate and land. Escalation of established and novel parasite populations in space and time within northern ecosystems has led to growing concern for the health of potential wildlife hosts, but the initial detection, monitoring, and trajectory of wildlife parasites in remote subarctic and Arctic regions is challenging to study and difficult to predict. In this thesis I examine the distribution of the winter tick, Dermacentor albipictus, in the northern Canadian territory of the Yukon to 1) assess evidence of historic and current spread of this parasite and determine its apparent northern boundary, 2) identify locations where off-host life stages occur, 3) determine abiotic factors that may increase the likelihood of larval D. albipictus occurrence and abundance at local scales, and 4) estimate the current and future transmission potential of D. albipictus to keystone hosts (moose, Alces alces, and woodland caribou, Rangifer tarandus caribou) in the territory. Through the creation of a global, integrated dataset, I show that D. albipictus has long had a widespread distribution in North America, but most likely established in the Yukon and the north in the past 50 years. Focusing in on the Yukon, I obtain the first off-host larval detection of this species in the field and show that the occurrence locations and abundances are strongly dependent on mean iii spring temperatures, but with accumulated degree-days below previously hypothesised thresholds for D. albipictus persistence. By designing and implementing a regional community engagement scheme for local hunters, I significantly improve on-host surveillance of D. albipictus and show that populations of this parasite may be spatially segregated by host species, changing our perception of the current risk to moose and woodland caribou in the territory. As D. albipictus is likely the first of many future species to expand its distributional range into the Yukon and northern North America, this work demonstrates the need to improve methods for detection and ongoing monitoring of species of wildlife health concern in the future.