The beaver and moose may be iconic Canadian wildlife, but neither is truly unique to Canada from a genetic standpoint. That distinction now belongs to a small population of western toads living in Alberta — the first known group of this species to exist exclusively within Canadian borders.
A team of researchers from the University of Ottawa made the discovery while studying toads across Alberta and British Columbia. Lead author Jayna Bergman, a PhD student, and her colleagues collected samples from toads and tadpoles living in ponds, wetlands, and lakes. By comparing the toads' DNA, they found that what scientists previously thought were just behavioral differences between two groups were actually genetic differences too.
Some western toads, those living east of the Rocky Mountains, have a vocal sac that lets them make a distinct mating call. Toads on the western side of the Rockies — and in southern parts of the species' range stretching from California to Alaska — lack this ability entirely. The research team discovered that these Calling and Non-Calling groups have been genetically separated for so long that they are now distinct populations.
"Our findings of a genetically distinct group entirely contained to a Canadian province is very unusual," Bergman said. "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."
The discovery came as a surprise because most species that span such a wide range — from California all the way to Alaska — tend to mix their genes where populations meet. The Rocky Mountains and the climate differences between their east and west sides appear to have kept these toad groups separate for a very long time.
The research, published in the journal Diversity and Distributions, turned up another surprise. The team also identified a third genetic group of western toads living in the southern Canadian Rockies, in southeastern British Columbia and southern Alberta. This group was previously unrecognized and may extend south into Montana.
Western toads already have some legal protection in Canada. They are listed as a Special Concern by COSEWIC, the committee that assesses wildlife risk in Canada, and fall under the federal Species at Risk Act. But Bergman argues these new genetic findings suggest the species needs even more attention.
The team plans next to study western toads across their entire range to better understand how these distinct groups developed and whether they can successfully breed with each other. That information will help determine if the toads might eventually become different species entirely.
For now, the Alberta toads stand apart — not just in their silence, but in their DNA.