It was formerly considered an isolated population of the common western toad (A. boreas) until physical and genetic analyses found it to be a separate species, and described it as such in 2017. It is descended from an ancestor that inhabited the large lakes and wetlands that covered the Great Basin in the Pleistocene until the receding water isolated the different populations, leading to speciation.

Description: It can be physically distinguished from the western toad by the scattered gold-colored flecks that cover its olive body, and is also the smallest member of the A. boreas species complex in the region.

Habitat: They are a nocturnal species, living under rocks or burrowed in the dirt during the day. The Dixie Valley toad is only found in a small complex of vegetated spring-fed marshlands in Dixie Valley, one of the hottest and geothermally active systems in the region. The surrounding areas are largely arid land with little aquatic resources, isolating A. williamsi from the rest of the world.

Range: The sole population of Dixie Valley toad lives in a hot spring-fed wetland in the Dixie Valley, northwest of Fallon, Nevada.

Found in these States: NV

Diet: Invertivore

Reproduction: Reproduction is external. The males will call to attract females. Once the female selects a male, the male will grsap her from behind. The female will then lay her eggs and the male will fertilize them. No parental care has bee shown.

Status: Critically Imperiled in Nevada. NOTE: Just listed as temporariy Endangered on 4/7/2022 See Temporay Rule

Taxonomy: