Dwarf woolly-heads, specific populations, COSEWIC assessment status report: chapter 4
Distribution
Global range
The main range of Psilocarphus brevissimus extends from central and eastern Oregon south along both sides of the Sierra Nevada Mountains to Baja California (Figure 2). The species also occurs in Chile and Argentina (Hitchcock et al. 1955, Morefield 1993).
Figure 2. North American distribution of Psilocarphus brevissimus(Based on maps from Cronquist 1950; Douglaset al. 2000, 2003; Kartesz 2003).
There are numerous outliers north and east of the main range - in northern Utah, Wyoming, Montana, southern Idaho, east-central Washington and north to western Canada just north of the 49th parallel (Kartesz 2003). The outlier populations appear to be discontinuous and there is no evidence of regular gene transfer among them. It appears likely that populations of many vernal pool plants are established as the result of seeds transferred by migrating waterfowl and shorebirds (Silveira 1998). Curiously, Psilocarphus brevissimus has been reported from southern Idaho where it is relatively common, but not from northern Idaho. A similar but smaller species, P. tenellus, has been reported from northern Idaho where it is very rare (Mancuso pers. comm. 2005). In contrast, P. tenellus has not been reported from Montana and all material in that state (including populations in the northern tier of counties) has been identified as P. brevissimus.
Canadian range
The Prairie Population (Figure 3) consists of numerous sites that have a 23,760 km² extent of occurrence. The area of occupancy of several sites of the Prairie Population has not been recorded but their aggregate area of occupancy is estimated, from habitat descriptions and preferences, as under 40 ha.
Figure 3. Distribution of the Prairie Population of Psilocarphus brevissimus.
The Southern Mountain Population (Figure 4) consists of three sites with a 1.5-2.0 km² extent of occurrence. It occupies an area of about 0.1 ha.
Figure 4. Distribution of the Southern Mountain Population of Psilocarphus brevissimus. (The two southern locations are only about 700 m apart and about 2.5 km from the northern location.)
Page details
- Date modified: