Revealing large-scale parasite ranges: An integrated spatiotemporal database and multisource analysis of the winter tick

Concerns that climate warming may drive the spread of ectoparasites into previously uninhabited areas have increased the need for baseline knowledge of their distributional history. For species of wildlife health concern, presence data are often lacking or outdated, thus limiting our ability to assess range changes and subsequent host impacts. We reconstructed the past and present distribution of the winter tick, Dermacentor albipictus, through the compilation of a spatiotemporal database to create the first full baseline map of its occurrence throughout its North American range. The ongoing impacts of winter tick epizootics in moose (Alces alces) and recent mortality events in elk (Cervus canadensis) and white-tailed deer (Odocoileus virginianus) have led to a resurgence in interest in the future of this parasite in a warming climate. Over 3400 unique records of winter tick occurrence were compiled from multiple data sources, dating from 1869 to 2020 and spanning from 16.5 to 66.2 degrees N latitude. Both conventional published sources and natural history records were included along with new records from previously unpublished datasets and citizen science observations, to make this a comprehensive occurrence dataset for this species. Along with standardized location information and year of observation, the dataset includes associated host species and descriptive categorization of the type and source of each record, providing new opportunities to examine host-parasite interactions in the winter tick system over time and space. In presenting these data, we discuss the potential sampling biases and lacunas in our integrated database records, particularly at the winter tick's northernmost range. We also document changes in the types and sources of winter tick information from past to present, highlighting potential issues that should be considered before using these data in further analyses and when collecting ongoing records. Our database demonstrates that the collation and synthesis of records beyond conventional sources can shed light on the distributional history of tick species and serve as a useful baseline for prioritizing future research and management decisions.