Arctostaphylos densiflora is a species of plant in the family Ericaceae. This low growing evergreen shrub is endemic to Sonoma County, California, and is, in fact restricted to a very limited area within western Sonoma County known as the Sonoma Barrens. This shrub, with the common name Vine Hill Manzanita, has a total population in the wild of fewer than 30 individuals, and can be considered to have entered an extinction vortex; preservation of this species is dependent upon conservation efforts that are underway. These conservation efforts for the species include the previous state and federal listing as an endangered species, and the active establishment of a preserve for the principal population of the species, which is being managed by the California Native Plant Society. The evolution of the species is based upon genus differentiation that began in the Middle Miocene, which led to an eventual appearance of the subject species may have first appeared approximately 1.5 million years ago.A. densiflora's position on its genus cladogram has recently been established with genome sequencing analysis.
The Arctostaphylos 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.
The Vine Hill Manzanita is a spreading shrub with decumbent arching branches that are capable of setting down secondary roots when the low hanging branches intercept the sandy soil substrate. Height of mature plants varies between 40 to 100 centimeters (cm). Leaves are elliptic to narrowly lanceolate-elliptic in shape; each rect leaf is attached to the stem via a petiole of approximately four to five millimeters (mm) in length. Leaf blades are 1.0 to 2.4 cm in length and 0.5 to 1.4 cm in width. The base of each leaf is wedge-shaped to obtuse; leaf margins are entire, with upper and lower leaf surfaces being alike, bright green, shiny, smooth and sparsely puberulent.
The Deltate flower bracts are generally 1.5 to 3.0 mm long, scale-like, and sharply pointed, but the lowest bract five to ten mm, and leaf-like, linear to elliptic. Pedicels are smooth and four to five mm in length.
has mealy reddish or orange bark and mealy berry-like fruits.
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
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