The beaver and moose may be enduring symbols of Canadian wildlife, but neither is uniquely Canadian from a genetic perspective. But a team of researchers from the University of Ottawa have now discovered something rare, a genetically distinct and exclusively Canadian population of Western toad (Anaxyrus boreas). This discovery highlights our country’s unique biodiversity and has important implications for conservation and wildlife management.
Published in the journal Diversity and Distributions, the study dives into the genetics of the Western toad, which is widely found across North America, particularly in the United States and in the provinces of Alberta and British Colombia.
‘Calling’ and ‘Non-calling’ populations genetically distinct
Lead author Jayna Bergman and her team travelled through ponds, wetlands, and lakes across Alberta and BC collecting samples from toads and tadpoles for ancestry-type testing that compared the toads DNA to see how closely related they were.
They found that the previously designated Calling and Non-Calling Western toad populations are genetically distinct. Calling toads (east of the Canadian Rockies) have vocal sacs and make mating calls, whereas non-calling toads (west of the Canadian Rockies) lack vocal sacs and do not make mating calls.
The new genomic evidence shows these aren't just behavioral differences—they are also genetically different populations. Because DNA slowly changes over time, populations that have been separated for long periods accumulate small genetic differences. By measuring these differences, researchers could identify which animals belong to the same genetic group and which come from distinct groups.
“Our findings of a genetically distinct group entirely contained to a Canadian province is very unusual. These genetic results suggest we should be doing more to protect this species, especially the Alberta population of the Western Toad because of its unique complement of the species’ total genetic diversity,” says Bergman, a PhD student at the Faculty of Science and in Professor Julie Lee-Yaw’s lab.
“These genetic results suggest we should be doing more to protect this species, especially the Alberta population of the Western Toad because of its unique complement of the species’ total genetic diversity.”
Jayna Bergman
— PhD student at the Faculty of Science
Implications for conservation planning
Western toads, which are crucial to healthy ecosystems, are already designated as a Special Concern by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) and are listed under the Species at Risk Act.
Curiously, toads to the east of Canada’s Rocky Mountains have a vocal sac that produces a distinct mating call, whereas toads to the west of the Rockies and in southern parts of the species' range lack these traits.
“This ‘advertisement call’ provides a notable difference in breeding strategies and may be the only example of such an extreme difference in calls within what are considered the same species,” explains Assistant Professor Lee-Yaw, an Assistant Professor from the Department of Biology, highlighting the uniqueness in comparison to non-calling types which range from California to Alaska. There are also habitat differences between the toads that can play a part.
In Canada, wildlife protection decisions depend heavily on identifying distinct populations and look at genetic distinctions, behavioural distinctions and if they are barriers to gene flow. In this case, the mountains, and climate differences associated with them, appear to have helped keep the two groups of toads separate.
A second surprise discovery
The team made another intriguing discovery when they identified a third genetic group of western toads in the southern Canadian Rocky Mountains. This previously unrecognized genetic group of toads is found in southeastern BC and southern Alberta and likely extends south into Montana in the USA. Many species in Canada were studied decades ago using limited genetic tools, but modern genomic techniques are helping identify previously unrecognized populations and evolutionary lineages.
Bergman says the next phase of this research should look to compare western toads across the entirety of their range to better understand how these distinct groups arose and whether the different genetic groups can successfully mate with each other—an essential step to testing whether they may be on the way to becoming different species.
Pronounced Genetic Structure Associated with Differences in a Reproductive Trait and Climatic Barriers in Canadian Populations of the Western Toad (Anaxyrus boreas) by J. Bergman, J. Enciso-Romero, G. Pauly, R. Gamlen-Greene, M. Todd, J. Lee-Yaw. DOI: 10.1111/ddi.70219.
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