Scientists find genetically distinct Western toad population exclusive to Canada

Scientists find genetically distinct Western toad population exclusive to Canada

Researchers from the University of Ottawa have identified a genetically distinct population of Western toad (Anaxyrus boreas) found exclusively within Canada. While animals such as the moose and beaver are iconic symbols of Canadian wildlife, the research team noted that neither is uniquely Canadian from a genetic perspective until this discovery.

The study, published in the journal Diversity and Distributions, focused on the genetics of the Western toad, a species distributed across North America, with significant populations in the United States and the Canadian provinces of British Columbia and Alberta.

To reach these findings, lead author Jayna Bergman and her team collected samples from tadpoles and toads across lakes, wetlands, and ponds in British Columbia and Alberta. The team performed ancestry-type testing to compare DNA and determine the closeness of the relationships between different populations.

Genetic and behavioral divides

The research reveals that populations previously categorized as "Calling" and "Non-Calling" are genetically distinct. Toads located east of the Canadian Rockies are the "Calling" variety, possessing vocal sacs used to produce mating calls. Conversely, those west of the Rockies and in southern regions of the species' range lack vocal sacs and do not make these calls.

Assistant Professor Julie Lee-Yaw from the Department of Biology described the advertisement call as a notable difference in breeding strategies. Lee-Yaw stated that this may be the only instance of such an extreme difference in calls within what are currently considered the same species, especially when compared to non-calling types found from Alaska to California.

The genomic evidence suggests these are not merely behavioral traits. Because DNA accumulates small changes over long periods of separation, the researchers were able to identify separate genetic groups. The team believes the Canadian Rocky Mountains and the climate differences associated with them acted as barriers to gene flow, helping keep the two groups separate.

Bergman, a PhD student in the Faculty of Science and in Professor Lee-Yaw's lab, described the find of a genetically distinct group contained entirely to a Canadian province as very unusual.

Conservation and unexpected discoveries

The discovery has immediate implications for wildlife management. In Canada, decisions regarding protection rely on identifying distinct populations based on genetic and behavioral distinctions. Western toads are already listed under the Species at Risk Act and are designated as a Special Concern by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC).

Bergman argued that these results suggest a need for increased protection of the species, specifically the Alberta population, due to its unique complement of the species' total genetic diversity.

During the study, the team identified a third, previously unrecognized genetic group of Western toads. This group is located in southern Alberta and southeastern British Columbia, and the researchers believe it likely extends south into Montana in the USA. The team noted that many Canadian species were studied decades ago with limited tools; however, modern genomic techniques are now uncovering these hidden evolutionary lineages and biodiversity.

Future research

The next phase of research will involve comparing Western toads across their entire range. According to Bergman, this will help scientists understand how these distinct groups originally arose. A primary goal will be determining whether different genetic groups can successfully mate, which is a necessary step in testing if the populations are in the process of becoming entirely different species.