Castilleja parvula

As treated here (following Kartesz, 1994 checklist), this record excludes Castilleja revealii, sometimes treated as C. parvula var. revealii.

Castilleja parvula is a perennial forb occurring on Tertiary igneous gravels from 2,700 to 3,700 m in elevation in the alpine or krummholz zone of the Tushar Mountains, Utah, in Piute and Beaver counties, and as an outlier population in Garfield County. There are an estimated five occurrences of this species located primarily on U.S. Forest Service-administered lands in Dixie and Fishlake National Forests. Threats to Castilleja parvula include grazing-related impacts, particularly from non-native introduced mountain goats, climate change and drought, and recreation. This species requires close monitoring by land managers due to it being highly utilized and preferred by ungulates for forage. Mountain goat herbivory is pushing this species on a trajectory of local extinction in core-use areas, and targeted management of mountain goats is highly recommended, especially in the Mt. Holly region.

Castilleja parvula occurs in the western United States, where it is endemic to upper elevations of the Tushar Mountains, Utah, in Piute and Beaver counties, and as an outlier population in Garfield County (Welsh et al. 2015, Alexander 2016, FNA 2019). Range extent was calculated using data from the Utah Rare Plant Database (2024).

By applying a 2 km separation distance to population location data from the Utah Rare Plant Database, there are five estimated occurrences (2024).

Threats to Castilleja parvula include grazing-related impacts, climate change and drought, and recreation (UNHP 2024, UNPS 2025). Mountain goats were introduced to the Tushar Mountains in 1986 for the purpose of trophy hunting, and are now naturalized to the region (Taye 1995). Grazing impacts have been observed from mountain goats, trespass cows, and native ungulates like deer, rodents and other lagomorphs. In a study of mountain goat and deer foraging preferences in the Tushars (Shipp 2022), Castilleja parvula was foraged at a significantly higher rate than would be expected based on cover, indicating that it is preferentially grazed by both deer and mountain goats. In four long-term monitoring plots established for this species, 20 to 58 percent of tagged Castilleja parvula showed evidence of herbivory by ungulates. Mountain goat herbivory is particularly heavy on Mt. Holly, where 97.4% of the herbivore captures from game cameras were mountain goats (Allphin 2025). Based on an analyses of fecal DNA samples from cows, mountain goats, pika, marmots, elk, and deer, Allphin (2025) calls this plant an "ice cream species," meaning that everything eats it. While it may have evolved to withstand some level of grazing by native ungulates, it is doubtful that this species can withstand current levels of grazing pressure with the introduction of a non-native species.

Climate change is also a threat likely impacting this species throughout its range (Wrobleski 2023). Droughts and rapid snowmelt due to wind-blown sediments are melting snowpack earlier than normal in this region (UNPS 2025). Recreational use of habitat, such as foot traffic, dispersed camping, and off-road vehicles may pose a threat to some populations, and hiking and off-road vehicle use has been increasing in recent years (Allphin 2025). As the human population grows in areas within easy access to habitat, and as recreational use increases, the impacts may become more significant. Historically, mining claims and exploration have impacted the available habitat, which has potentially contributed to its imperiled status today (Rodriguez 2004).