Botrychium hesperium

Wagner and Wagner (1990) reported that Botrychium hesperium had been discovered in the northern Great Lakes region, but in 1996 considered that to be false and rather proposed a new species "B. michiganense" (Farrar 2011; Gilman et al. 2015). B. michiganense was described by Gilman et al. (2015) with a range across northern North America. Recent research has found that Botrychium hesperium only occurs in western North America (Farrar 2011; Gilman et al. 2015; Williams et al. 2016).

Known from over 90 occurrences thus far and more are expected. Range includes much of the Rocky Mountains, from the San Francisco Peaks in Arizona north to Yukon. Occurrences are very often small and isolated, with counts of aboveground sporophytes rarely exceeding 100; however, additional gametophytes and juvenile sporophytes belowground may add to the size of many occurrences and provide some buffer from environmental stochasticity. Appears to strongly favor open habitats within a forested matrix; threats include succession on the one hand (and suppression of natural disturbances such as fire) and human activities associated with anthropogenically-disturbed habitats on the other (e.g. potential herbicide treatment of roadside populations).

Botrychium hesperium ranges from Yukon south through the Rocky Mountains to northern Arizona (Farrar 2011; Gilman et al. 2015). It may also occur in Alaska (Farrar 2011), Saskatchewan (VASCAN 2018), and New Mexico (BONAP 2014). Reports from Michigan, Ontario, and Minnesota, are now identified as Botrychium michiganense (Gilman et al. 2015). Botrychium hesperium may be confused with similar species, especially B. michiganense (in the north) and B. echo (in the south) (Farrar 2011).

Over 90 extant occurrences are known, but this is thought to be an underestimate and additional occurrences are likely. Number of extant occurrences is in British Columbia 17, Alberta 13, Washington 17, Oregon 6, Wyoming 8, and Colorado 33 (NatureServe Network Database as of November 2017; Heidel and Handley 2015). There are 47 observations in Montana (Montana Natural Heritage Program 2018). There are also 6 occurrences reported in Saskatchewan and an unknown number of occurrences in Yukon, Idaho, and Utah (NatureServe Network Database as of November 2017).

Threats to B. hesperium are not well understood. Because this species occurs in both naturally and artificially disturbed sites, threats include natural plant succession as well as the same human activities (recreation, road and trail maintenance activities, selection of grazing areas) that have also apparently resulted in suitable habitat (especially when populations are small). Anderson and Cariveau (2004) point out that habitat created by anthropogenic disturbance has not yet been proven to support viable populations in the long-term; it is possible that human-created habitats may become inhospitable later due to processes such as microbial or fungal succession. Agriculture and forestry activities may also threaten this species in some areas. In Colorado, in rough order of decreasing priority, threats are listed as habitat loss, recreation, succession, overgrazing, effects of small population size, sedimentation, timber harvest, exotic species invasion, global climate change, and pollution (Anderson and Cariveau 2004). These authors suggest that minimizing soil disturbance may be important to the species; they note that off-road vehicle use (both motorized and non-motorized) represents a significant threat, and that the use of livestock grazing to enhance habitat is risky. Threats in the Wallowa Mountains of Oregon include fire suppression, pack animal grazing, wood-cutting, and recreation-associated activities (Anderson and Cariveau 2004). In Montana, many populations occur on roadsides or other similarly open or disturbed habitats, leaving them vulnerable to invasive species, weed spraying, road maintenance, and timber management (Montana Natural Heritage Program 2018).