Arctostaphylos is a genus of plants in the family Ericaceae. This group of 109 shrubs and small trees has a center of biological diversity in the California Floristic Province, although a few of the bearberries are circumboreal and widespread. There are significant conservation issues for the genus, since many species have highly restricted distribution,and many are classified as rare or endangered species; over half of the taxa are classified as rare or endangered species by the California Native Plant Society. The evolution and taxonomy of the Arctostaphylos genus are complex issues, the subjects of which have recently been explored with genome sequencing analysis. The taxa in the genus generally have reddish or orange bark and mealy berry-like fruits.
The genus evolution was likely centered in the far western part of North America, where fossil ancestors dating to the Middle Miocene are apparent. The genus was likely even more diversified as it evolved into the Early Tertiary. Evolution of genus Arctostaphylos likely shares a similar timeline with that of Ceanothus, which is another western North America genus that exhibits fire regenerative properties. Extensive use of the fruit and leaves were made by prehistoric peoples for culinary, medicinal and ceremonial purposes.
While 96 of Arctostaphylos taxa are found in California, there are several species that are circumboreal in distribution. The most widespread species are Red, Alpine and Common bearberry; in fact Common bearberry, A.uva-ursi, is found in arctic and subarctic circumboreal regions, and their range extends south to higher altitude habitats in the Rocky Mountains in North America; and to the Grampians, Carpathians, Alps and Caucasus in Eurasia.
Within the California Floristic Province, the centroid of Arctostaphylos is the narrow coastal region between San Luis Obispo and Mendocino Counties where at least 30 of the genus taxa are found. Many of the California endemics are specialists to unusual soils which have extreme values of pH, serpentine soils, mineral composition or sand content. A classic example of such specialization is A.densiflora which occurs in a highly restricted locale known as the Sonoma Barrens, where soils are very high in sand content and exhibit low pH levels and an unusually hard surface compaction. 
Most of the species within the Arctostaphylos genus are evergreen, with Red bearberry and Alpine bearberry being exceptions. Plant height within this group varies between 30 centimeters and 600 centimeters, with architecture varying between erect to prostrate form; moreover, many of the taxa are characterized by a fire-resistant basal burl. The bark color is generally reddish to orange, and while typically very smooth, some species have a distinctive shredding or peeling character. The simple, alternating leaves are spreading to ascending, and are sometimes convex. Leaf margins are flat to rolled. Although upper and lower leaf surfaces are sometimes similar, some species manifest differences in color or stomatal density in upper versus lower leaf surface. For example, coastal California taxa have stomata restricted to the lower leaf surface.
The terminal inflorescences are panicle or raceme in form; moreover, flowers have bracts that may be either scale-like or leaf-like. The radially symmetric flowers typically have a five lobed corolla and five free and persistent sepals. Corollae are spheric to bowl shaped, and are most often white to pink. Most often there are ten stamens and two recurved awns. The ovary is superior, with base circumscribed by a nectar disk. Orange to red fruits are berry-like and approximately spheric, with generally thick, mealy pulp and two to ten stones. Fruits usually appear in the summer or autumn, following flowering seasons in winter and spring.
Evolution and taxonomy
The genus is situated in a monphyletic 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, especially in non-crown sprouting taxa; 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. Sands has 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.
Earlier taxonomic treatments were governed by morphological methodology, most notably by Wells; however, more recent genome sequencing work by Boykin et al. has demonstrated the incongruence of purely morphological treatment with closely related species as determined by Internal Transcription Sequencing (ITS) methodology.
Example species within the genus include:
- Arctostaphylos alpina, Alpine Bearberry
- Arctostaphylos andersonii, Santa Cruz Manzanita
- Arctostaphylos auriculata, Mount Diablo Manzanita
- Arctostaphylos bakeri, Baker's Manzanita
- Arctostaphylos canescens, Hoary Manzanita
- Arctostaphylos catalinae, Santa Catalina Island Manzanita
- Arctostaphylos columbiana, Hairy Manzanita
- Arctostaphylos confertiflora, Santa Rosa Island Manzanita
- Arctostaphylos cruzensis, La Cruz Manzanita
- Arctostaphylos densiflora, Sonoma Manzanita
- Arctostaphylos edmundsii, Little Sur Manzanita
- Arctostaphylos gabrielensis, San Gabriel Manzanita
- Arctostaphylos glandulosa, Eastwood Manzanita
- Arctostaphylos glauca, Bigberry Manzanita
- Arctostaphylos glutinosa. Schreiber's Manzanita
- Arctostaphylos hispidula, Gasquet Manzanita
- Arctostaphylos hookeri, Hooker's Manzanita
- Arctostaphylos hooveri, Hoover's Manzanita
- Arctostaphylos imbricata, San Bruno Mountain Manzanita
- Arctostaphylos insularis, Island Manzanita
- Arctostaphylos klamathensis, Klamath Manzanita
- Arctostaphylos luciana, Santa Lucia Manzanita
- Arctostaphylos malloryi, Mallory's Manzanita
- Arctostaphylos mendocinoensis, Pygmy Manzanita
- Arctostaphylos mewukka, Indian Manzanita
- Arctostaphylos montaraensis, Montara Manzanita
- Arctostaphylos montereyensis, Monterey Manzanita
- Arctostaphylos morroensis, Morro Manzanita
- Arctostaphylos myrtifolia, Ione Manzanita
- Arctostaphylos nevadensis, Pinemat Manzanita
- Arctostaphylos nissenana, Nissenan Manzanita
- Arctostaphylos nortensis. Del Norte Manzanita
- Arctostaphylos nummularia, Glossyleaf Manzanita
- Arctostaphylos obispoensis, Serpentine Manzanita
- Arctostaphylos osoensis, Oso Manzanita
- Arctostaphylos otayensis, Otay Manzanita
- Arctostaphylos pajaroensis, Pajaro Manzanita
- Arctostaphylos pallida, Pallid Manzanita
- Arctostaphylos parryana, Parry Manzanita
- Arctostaphylos patula, Greenleaf Manzanita
- Arctostaphylos pechoensis, Pecho Manzanita
- Arctostaphylos pilosula, La Panza Manzanita
- Arctostaphylos pringlei, Pringle Manzanita
- Arctostaphylos pumila, Sandmat Manzanita
- Arctostaphylos purissima, La Purissima Manzanita
- Arctostaphylos refugioensis, Regugio Manzanita
- Arctostaphylos regismontana, Kings Mountain Manzanita
- Arctostaphylos rudis, Shagbark Manzanita
- Arctostaphylos silvicola, Bonny Doon Manzanita
- Arctostaphylos stanfordiana, Stanford's Manzanita
- Arctostaphylos tomentosa,Woolyleaf Manzanita
- Arctostaphylos uva-ursi, Common Bearberry
- Arctostaphylos virgata, Bolinas Manzanita
- Arctostaphylos viridissima, Whitehair Manzanita
- Arctostaphylos viscida, Sticky Manzanita
- Arctostaphylos wellsii, Wells' Manzanita
Habitat and ecology
The chaparral biome is considered classic habitat of the Arctostaphylos genus in its center of diversity; however, there are many California occurrences in forest settings especially oak woodland and savanna. In many cases the taxa are found on highly distinctive soil substrates which are notable in extreme pH, mineral content (especially ultramafic soils), high sand content, extreme surface compaction or other notable abiotic factors. Common chaparral associates are Prunus ilicifolia, Cercocarpus betuloides, rhamnus crocea, Rhamnus california, chamise, Toxicodendron diversilobum, and a wide variety of Ceanothus species. Arctostaphylos species are also a key component of communities which are transitional between chaparral and coastal sage scrub types. Artemisia californica, Eriogonum fasciculatum, Lotus scoparius and a variety of sage taxa are understory associates within transitional communities.
Taxa in this genera which have become specialized to extreme soil mineralization or pH conditions are often rare and endangered species; an example is A. densiiflora, specialized to the low pH sandy soil substrate of the Sonoma Barrens. In turn this habitat is home to other rare species, such as Clarkia imbricata and Ceanothus foliosus var. vineatus, that have adapted to these extreme soil conditions. Many other Arctostaphylos species are adapted to coastal sand dunes. All three subspecies of A. hookeri are restricted to serpentine soils, while A. bakeri has a strong association with serpentine. Many Arctostaphylos taxa are specialized to combinations of soil and climate extremes; for example, certain taxa are adapted to the high desert.
All taxa within the genus are hermaphroditic and insect pollinated. Flowers characteristically appear in the spring, with many coastal species blooming as early as winter, due to the mild conditions of coastal microclimates. Fruits develop in summer and endure for a long time well into autumn.
Native Americans of the far western part of North America are known to have utilized Arctostaphylos species in a host of ways, including nutrition and medicinal functions. In terms of food preparation, the fruits were consumed either fresh or dried, even though the taste is quite bland and the texture is mealy; it is worth noting that all species are considered edible. The berries were also crushed and mixed with water to produce a drink; moreover, that liquid was commonly augmented with animal fat or fish eggs to concoct soup or porridge.
Medicinally, leaves and berries were admixed into either as a liquid infusion or as a powdered formulation to serve as a cold remedy, a kidney tonic, an analgesic, miscarriage preventative or treatment for skin wounds. On other occasions the dried leaves were smoked by certain tribes to produce a narcotic effect. In terms of specific tribal use of discrete taxa:
- Pomo Kashaya tribes used A. columbiana and A. glandulosa as an anti-diarrheal made from bark decoction.
- Cahuilla tribes used A. glauca leaf infusion for poison oak rash.
- Ojibwa tribes used A. alpina to prepare an infusion from crushed plants as an external anti-rheumatic wash; Ojibwa used the same species ingested tor internal blood disease, and also smoked leaves to produce intoxication.
- Concowtribes used A. manzanita for veterinary treatment of sore backs in their horses.
- Miwok tribes chewed leaves of A. Manzanita to cure stomach cramps.
- Capella and Pomo tribes made a leaf decoction from A. Manzanita to produce a wash for headache pain.
- Karok tribes used A. nevadensis as antidote for acute poison oak affliction.
- Atsugewi tribes made a poultice from A. patula as a burn dressing.
- Shoshoni tribes used a decoction from A. patula leaves taken orally for venereal disease.
- Crow tribes used pulverized leaves of A. uva-ursi for oral canker sores.
- Sanpoil tribes used an infusion of A. uva-ursi as a shampoo and for scalp diseases.
There are many significant conservation issues associated with the genus, due to the large fraction of rare, threatened and restricted distribution species. Specific conservation activities associated with these taxa include analysis for endangerment listing, the listing process itself and numerous species and habitat conservation plans as well as species and habitat recovery plans. Numerous governmental agencies are participating in these functions including the U.S. Environmental Protection Agency, United States Fish and Wildlife Service, California Department of Fish and Game, and numerous county governments.
An example of species and habitat recovery plans ensued in Alameda County, California subsequent to the Caldecott Tunnel explosion and fire of 1991. In this case one of the primary foci was protection and recovery of the endangered Alameda whipsnake, but also addressed the endangered Pallid Manzanita and a number of other federally listed flora. A second example of habitat conservation planning exists with San Bruno Mountain in San Mateo County, California where the San Bruno Mountain Manzanita is protected along with numerous other threatened species; the San Bruno Mountain population of this Arctostaphylos species is one of only five extant colonies of this taxon. A third example addresses one of the rarest of all Arctostaphylos taxa, the Vine Hill Manzanita. In this case there is a single primary population of the species, which is in a protected preserve under active management by the California Native Plant Society; threats to this taxon and other endangered species in the preserve include invasion by Holcus lanatus grass and competition from other native species.
- ^ Laura M.Boykin, Michael C.Vasey, V.Thomas Parker and Robert Patterson. 2005. Two Lineages of Arctostaphylos (Ericaceae)Identified using the Internal Transcribed Spacer (ITS) Region of the Nuclear Genome. Madrono, vol. 52, no. 3, pp 139-147
- ^ William Skinner Cooper. 1922. The broad-sclerophyll vegetation of California: an ecological study of the chaparral and its related communities. The Carnegie Institute of Washington. 124 pages
- ^ James Roof. 1972. Detective Story: Our Lost Sonoma Barren. The Four Seasnons, vol.4, no.2, Berkeley, California
- ^ Jepson Manual. 1993. Arctostaphylos. University of California, Berkeley
- ^ Arbutoideae (Meisn.) Nied., Bot. Jahrb. Syst. 11: 135. 1889. Type genus: Arbutus L. Arbuteae Meisn., Pl. Vasc. Gen.: Tab. Diagn. 243, Comm. 154. 1839.
- ^ Peter H. Raven and Daniel I. Axelrod. 1978. Origin and relationships of the California flora. University of California Press. 134 pag.es
- ^ Anne Sands. 1980. Riparian forests in California: their ecology and conservation: a symposium., University of California, Davis. 124 pages
- ^ Michael G.Barbour, Todd Keeler-Wolf and Allan A.Schoenherr. 2007. Terrestrial vegetation of California. University of California Press. 712 pages
- ^ C.Michael Hogan. 2008. Toyon: Heteromeles Arbutifolia GlobalTwitcher, ed. N. Stromberg
- ^ Linda H. Beidleman and Eugene N. Kozloff. 2003. Plants of the San Francisco Bay region: Mendocino to Monterey. University of California Press. 504 pages
- ^ Jules Janick and Robert E. Paull. 2007. The encyclopedia of fruit & nuts. CABI. 954 pages
- ^ Daniel E. Moerman. 2009. Native American medicinal plants: an ethnobotanical dictionary. Timber Press. 799 pages
- ^ Neil G. Sugihara. 2006. Fire in California's ecosystems. University of California Press. 596 pages