San Diego Management & Monitoring Program


Wart-stemmed ceanothus
Ceanothus verrucosus


Kingdom Phylum Subphylum Class Order Suborder Family

Current distribution rangewide

Riverside County, San Diego County, and northern Baja California, Mexico [1].


Known Populations in San Diego County

Twenty-two occurrences on Conserved Lands in Mus 1 (Cabrillo National Monument, Tijuana River Valley Regional Park), 2 (Florida Canyon, 34th Street Canyon, Manzanita Canyon, Soledad Natural Park), 6 (Bernardo Mountain, Carmel Mountain Preserve, Del Dios Highland Open Space Preserve, Elfin Forest Recreational Preserve, Hodges Reservoir Open Space, Oakcrest Park, Rancho La Costa Habitat Conservation Area, Torrey Pines State Natural Reserve), and 7 (City of Encinitas Open Space, Crest Canyon Preserve, Torrey Pines State Natural Reserve).


List status

None [1].


Habitat affinities

Rocky slopes, chaparral [2], and coastal scrub [3]. Elevation range is 1-380 meters [1].


Taxonomy and genetics

Rhamnaceae family [1].


Life history demography

Perennial evergreen shrub [1]. Long-lived obligate seeder [3]. Killed by fire, but dependent on it for stand reestablishment.


Seasonal phenology

Bloom period December-May [1].


Pollination seed dispersal

Primarily an obligate seeder with rare vegetative establishment [4]. Seed production begins at 3-6 years [3, 4, 5]. Peak production is estimated at 300 seeds per plant [3]. Long-lived persistent seedbank [4]. Seeds initially dispersed about 1 meter from plant ballistically [6; cited in 3] and secondarily by animal vectors such as harvester ants, small mammals and birds [7, 8; both cited in 3].


Threats

Fire-dependent episodic reproduction increases vulnerability to climate change in two ways: 1) changes in timing and intensity of fires and 2) precipitation changes affecting post-fire reproduction [4]. Obligate seeders face 2 fire-related risks: 1) seed bank depletion occurring with very long fire intervals and 2) immaturity risk with fires occurring before seedbank is built. Habitat fragmentation due to coastal development. Shortened fire return interval due to human-caused ignitions.


Special considerations:

Herbivory and drought drive mortality in the first 2 years [8; cited in 3, 9, 10]. Habitat suitability under projected future climate scenarios was determined using Maxent in a 2011 study by Dawn Lawson [3]. Results from the Bonebrake et al. study determined that managed relocation of seeds is an effective management alternative to reduce population decline resulting from land-use and climate change [11]. SDMs from this study predicted future habitat patches only beyond the current known distribution, leaving managed relocation the only type of translocating available. These patches are not on conserved lands, and with the current legal conservation status of C. verrucosus, managed relocation would be challenging.


Wart-stemmed ceanothus sources