Santa Monica Mountains Dudleya

Dudleya cymosa ssp. ovatifolia

Description

Like many Dudleya taxa, D. cymosa ssp. ovatifolia, Santa Monica Mountains dudleya, has rosette leaves that are evergreen rather than subject to summer withering. Rosette leaves are 0.8-2 in (2-5 cm) long and 0.6-1 in (1.5-2.5 cm) wide, floral stems are 1.6-6.0 in (4-15 cm) tall, and corollas are pale yellow.

Dudleya cymosa ssp. ovatifolia was first described as D. ovatifolia in 1903. The species was subsequently recognized as Cotyledon ovatifolia in 1904 and Echeveria ovatifolia in 1930, when broad generic concepts were applied to the family Crassulaceae. The new combination Dudleya cymosa ssp. ovatifolia was published in 1957. In 1983, plants found near Agoura in Los Angeles County were considered to be one of "two somewhat distinct races" of Dudleya cymosa ssp. ovatifolia.

The ovate leaves with a maroon underside distinguish the "Topanga" race of D. cymosa ssp. ovatifolia from other Dudleya, while the glaucous leaves and lemon-yellow flowers separate the "Agoura" race of D. cymosa ssp. ovatifolia from other local species. Four years later, however, the new combination D. cymosa ssp. agourensis was published to refer to "Agoura" material. He distinguished the new subspecies from D. cymosa ssp. ovatifolia by the number and shape of rosette leaves, pedicel length, and degree of spreading in petal apices. It was concluded in 1992 that these differentiations were insufficient to warrant taxonomic recognition as a subspecies of D. cymosa ; consequently, he lumped D. cymosa ssp. agourensis with D. cymosa ssp. ovatifolia in his 1993 revision of the genus for The Jepson Manual. The U.S. Fish and Wildlife Service considers Dudleya cymosa ssp. ovatifolia to include D. cymosa ssp. agourensis.

Habitat

Santa Monica Mountains dudleya is found on rock outcrops with forms specific to sedimentary conglomerate or volcanic breccia. It occurs on exposed, north-facing slopes.

Distribution

Santa Monica Mountains dudleya is found scattered along exposed north-facing slopes of the Santa Monica Mountains from near Westlake Village to Agoura, and in deep canyon bottoms along lower Malibu Creek and Topanga Creek. Less than ten occurrences have been reported, each consisting of no more than several hundred individuals. While future surveys may locate additional occurrences of the "Agoura" form along the northern slopes of the Santa Monica Mountains, the limited amount of habitat available makes it unlikely that the total number of individuals will exceed several thousand.

Material collected by David Verity in 1951 from Modjeska Canyon on the western flank of the Santa Ana Mountains in Orange County was included by Uhl and Moran in their 1953 cytotaxonomic article on Dudleya as D. ovatifolia. These populations, which are not threatened, represent a range disjunction of approximately 60 mi (96 km) to the southeast of the Santa Monica Mountains. Boyd reported in 1995 that the subspecies in the Santa Ana Mountains was locally common on north-facing cliffs in chaparral, central Santiago Canyon near Fleming Peak to near the summit of the west slope of Modjeska Peak, although co-author Fred Roberts, in a verbal comment, indicated that local and restricted, but common where found would better describe the distribution.

Threats

The primary threat to Santa Monica Mountains dudleya is habit alteration and destruction caused by encroaching urban development. Populations of this taxon in Malibu and Topanga Canyons occur largely on lands owned and managed by the DPR. One of these populations is relatively inaccessible; however, another occurrence is directly adjacent to private property that has been bulldozed for development access. Two occurrences are on lands designated as open space by COSCA, while the remaining occurrences in the Santa Monica Mountains are on several privately owned properties zoned for commercial and residential development along the north slope of Ladyface Mountain. A 1996 cumulative impacts analysis from an area project proposal shows at least 75 projects proposed or already under construction within 4 mi (6.5 km) of the Santa Monica Mountains populations. This density of development threatens the habitat of Santa Monica Mountains dudleya.

Portions of populations of this plant have been extirpated by development in the cities of Agoura Hills, Thousand Oaks, and Westlake Village. The majority of their distribution is on private lands located in a region with increasing development pressures.

Weed abatement operations along roadsides, which involve scraping with a skiploader, destroyed several hundred individuals of Santa Monica Mountains dudleya; this activity continues to degrade its habitat.

Conservation and Recovery

The Santa Monica Mountains dudleya occurs at fewer than ten sites along the northern slopes of the Santa Monica Mountains, totaling fewer than several thousand individuals. It occurs largely on lands owned and managed by the California Department of Parks and Recreation. Two other occurrences are on lands designated as open space by the Conejo Open Space Conservation Agency. The critical habitat on these public lands must be protected from urban development. The remaining occurrences of the Santa Monica Mountains dudleya are on privately owned properties zoned for commercial and residential development, and are at risk of destruction. These habitats should also be protected. This could be done by purchasing the land and designating ecological reserves, or by negotiating conservation easements with the landowners. The populations of the Santa Monica Mountains dudleya should be monitored, and research undertaken into its biology and habitat needs.

Contact

U.S. Fish and Wildlife Service
Ventura Fish and Wildlife Office
2493 Portola Road, Suite B
Ventura, California 93003-7726
Telephone: (805) 644-1766

Reference

U.S. Fish and Wildlife Service. 29 January 1997. "Endangered and Threatened Wildlife and Plants; Determination of Endangered Status for Two Plants and Threatened Status for Four Plants From Southern California." Federal Register 62 (19): 4172-4183.