Low Bush Monkey Flower [Mimulus aridus (Abrams) Grant = Diplacus aridus Abrams]

Low Bush Monkey Flower [Mimulus aridus (Abrams) Grant = Diplacus aridus Abrams]

Listing CNPS List 4 R-E-D Code 1-1-2

State/Federal. Status -- /C3c SCROPHULARIACEAE Apr.-Jul.

Global Rank G2G3 State Rank S?

Distribution: San Diego County, Imperial County; Baja California, Mexico

Habitat: Desert Chaparral on the eastern slopes of the Peninsular Range is the primary habitat of this shrub. It seems particularly well adapted to rock outcrops. Soils are mapped as Acid Igneous rock lands for the population in Carrizo Gorge. Typically shrub cover is somewhat open due to the presence of very large granitic boulders interspersed throughout the terrain.

Known Sites: This conspicuous shrub grows in rocks near the Carrizo Gorge railroad spur by Dubber, and scattered among the boulder piles near the San Diego County line at Mountain Springs. The desert foothills are little explored and this species may be more common than available herbarium specimens would indicate. Reports are from Ranchita, the San Ysidro Mountains, Grapevine Canyon, Canebrake Canyon, Mortero Palms, between Shaw Canyon and Potrero Canyon, above the Dos Cabezas Campground; onto the southern high desert at Jacumba, Bankhead Springs, and Hipass. An old biological survey report notes a site near Bankhead Springs 1 mile west of Highway 80 and 0.25 mile north of the Mexican border.

Found in Baja California south to the Sierra San Borja at 28 47' where collected by Moran (SD 60653) north of Cerro el Sauco. Only 5 specimens from Baja California are found at the San Diego Natural History Museum's herbarium.

Status: Low Bush Monkey Flower populations are presumed stable, based on limited historical impacts to the rocky, desert slope habitat of this species. Substantial populations should be protected. This shrub is referred to Mimulus aurantiacus Curtis in the Jepson Manual as a local form of a highly complex and variable species. However, this shrub maintains a distinctive desert habitat separate from other forms, and is now apparently evolving along a separate lineage with some degree of geographic isolation. Plants growing in semi-desert chaparral near Aguanga near the Riverside/San Diego County line have a very hairy calyx but are otherwise quite similar in growth habit and flower morphology to Low Bush Monkey Flower; such plants do provide a geographical linkage to forms once designated as Mimulus longiflorus, but now considered part of the Mimulus aurantiacus complex.


Copyright May 1994 Craig H. Reiser.

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