Regularity: Regularly occurring
Global Range: Only on 1-2 quads in San Luis Obispo County, California.
Catalog Number: US 1898530
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Verification Degree: Card file verified by examination of original publication
Preparation: Pressed specimen
Collector(s): B. Schreiber
Year Collected: 1938
Locality: Morro Bay, Hazard Canyon; alt. 200 ft., San Luis Obispo, California, United States, North America
Elevation (m): 61 to 61
- Syntype: Wieslander, A. E. & Schreiber, B. O. 1939. Madrono. 5: 42.
Comments: Soils derived from ancient sand dunes. Found in nearly pure stands on steep slopes, especially on north exposures. On low-moderate slopes, found in association with coastal dune scrub, maritime chaparral, and coast live oak woodland communities. < 200 m elevation.
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 6 - 20
Comments: Eighteen occurrences.
Evolution and Systematics
The entire genus is situated in a monophyletic clade or sub-family known as the Arbutoideae, which is populated by taxa having bright fleshy berries with fibrous or bony endocarp.. Evolution of the genus is relatively recent, with hybridization playing an important role; however, convergent evolution patterns appear to complicate cladistic constructions for certain portions of the genus cladogram. In any case, fossil ancestors of the Arctostaphylos genus have been suggested to have occurred in the Middle Miocene, with modern species beginning to take shape in the Late Tertiary. It has been further posited that in the earlier Tertiary a greater species diversity was present, influenced by influence of floristic influence of southwestern North America ancestors. This hypothesis also suggests that the present palette of California Arctostaphylos species became more depauperate upon arrival of a cooler drier climate in the Late Tertiary.These evolutionary views are coincident with other research that points to fire-dependent plant associations developing in the Late Miocene in California.
Present species distribution of Arctostaphylos morroensis is restricted to a very small coastal extent in San Luis Obispo County, California. Total land area of population occurrence is less than 900 acres in sandy coastal soils, originating as Pleistocene unstabilized or semi-stabilized dunes. Specific occurrence includes Montana de Oro State Park.
National NatureServe Conservation Status
Rounded National Status Rank: N2 - Imperiled
NatureServe Conservation Status
Rounded Global Status Rank: G2 - Imperiled
Reasons: Known only from western San Luis Obispo County, California and restricted to a particular substrate. The species is very locally abundant but potential habitat has been reduced by development to about one-third of its estimated historic level. Half of the remaining habitat is in small patches in and around developed areas; half is more continuous and supports dense stands (over 50 percent cover) of this species.
Date Listed: 12/15/1994
Lead Region: California/Nevada Region (Region 8)
Listing status: T
For most current information and documents related to the conservation status and management of Arctostaphylos morroensis, see its USFWS Species Profile
Degree of Threat: Very high - medium
Comments: Alteration or destruction of habitat due to urbanization, alternate fire regimes and possibly by non-native plants (CNPS 2001). Development of homes and roads are by far the major threat (CNDDB 2003). In addition, ORV use is a threat (CNDDB 2003).
Arctostaphylos morroensis is a species of manzanita known by the common name Morro manzanita. This shrub is endemic to San Luis Obispo County, California, where it is known only from the vicinity of Morro Bay.
There are 18 occurrences of the Arctostaphylos morroensis plant, and it is abundant in some local areas. It is limited to a specific type of substrate known as "Baywood fine sands", a type of sandy soil which originated in the Pleistocene as windblown sand dunes. The plant is found on less than 900 acres of coastal sage scrub and chaparral habitat, sometimes forming monotypic stands on hillsides.
Two thirds of its habitat is privately owned, some of it is slated for development, and its habitat requirements are narrow; these and other problems led to the plant's being listed as a threatened species in 1994. Some of the plants are protected within Montaña de Oro State Park.
Arctostaphylos morroensis is a spreading shrub, reaching up to 4 meters in height but generally staying wider than tall. It has shreddy red-gray bark and whiskery bristles on the smaller branches and twigs. The leaves are oval-shaped and slightly convex, dark green on the upper surface and duller gray-green beneath. Plentiful flowers hang in dense clusters on short pedicels during the winter months. They are usually very light pink, urn-shaped, and hairy inside. The fruits are fuzzy red drupes each about a centimeter wide.
- The Nature Conservancy
- USFWS. Endangered or threatened status for five plants and the Morro Shoulderband Snail from western San Luis Obispo County, California. Federal Register December 15, 1994.
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