Castilleja salsuginosa

Flora of North America Editorial Committee (2019) notes that slightly smaller-flowered plants that occur around hot springs in Eureka County, Nevada may be a distinct taxon, separate from Castilleja salsuginosa.

Castilleja salsuginosa is a Nevada endemic with only one to two known occurrences in a unique, fragile hot springs habitat (apparently, it is restricted to the particular edaphic situation created by a few mineral spring drainages). Threats to this species include water diversion away from the hot springs, herbivory, and climate change. There is a taxonomic question about whether the Eureka County population represents a new taxon. Regardless, this is a restricted, rare, endemic that should be protected.

Castilleja salsuginosa is endemic to Nevada where it is limited to the harsh alkaline soils of travertine hot springs (Flora of North America Editorial Committee 2019). Plants are known from two areas, one in White Pine County and one in Eureka County. There is a question about whether the Eureka County plants should be split off as a separate taxon, which would make the range of Castilleja salsuginosa even smaller.

Currently, there are two populations of this species, one in White Pine County and another in Eureka County, about 134 km apart. Not all researchers agree that these two populations belong to Castilleja salsuginosa. Regardless of whether one believes both populations should be placed in C. salsuginosa, or treated in separate taxa, both populations represent critically imperiled taxa. Even when treating both populations as 'salsuginosa', the taxonomy followed here, the conservation rank is critically imperiled.

A number of threats impact this species including, herbivory, livestock, horses, pronghorn antelopes, off-road vehicles, changes in water levels from geothermal development, land conversion for an energy corridor and climate change (USFWS 2009; NatureServe Network Database as of April 2021). Changes in groundwater levels at the hot springs where this species occurs will cause negative responses, and geothermal energy development is the most likely source of groundwater disturbance (USFWS 2009). Also, water diversion from the spring heads for private use has also been a threat (NatureServe Network Database as of April 2021). Water diversion may cause either an immediate decline or a long term decline, or both. A immediate negative response to water diversion could occur if large quantities of water are diverted, and only long term declines may be detected if smaller quantities of water are drawn away over a period of time. All in all, changes to the hot spring hydrology will negatively affect the Monte Neva paintbrush. In 2007 surveys, heavy herbivory was evident, but the impacts were unclear. For example, it was evident that the plants had been eaten, including the flower spike, but in later visits in the same season the plants had branched and produced multiple inflorescences (pers. comm. S. Caicco). Camping and off-road vehicles have been cited as threats to this species at one site (NatureServe Network Database as of April 2021, USFWS 2009). Finally, climate change is also a potential threat to this paintbrush species (USFWS 2009). Climate change could affect this species in that the Great Basin valleys, including the Steptoe valley where this taxon occurs, will be faced with warming and drying conditions in the future.