Arctostaphylos rainbowensis, a new burl-forming manzanita from northern San Diego County, California

Arctostaphylos rainbowensis Keeley & Massihi is a new burl-forming manzanita restricted to northwestern San Diego County and adjacent Riverside County. Previously it had been treated as a disjunct population of the largely Baja Californian A. peninsularis P; Wells or a hybrid between A. glandulosa Eastw. and A. glauca Lindley. Principal components analysis on 48 characters shows that A. rainbowensis is distinct from all three of these species. It differs from A. peninsularis in its larger leaves with almost twice as many stomata on the abaxial as on the adaxial surface, sparsely glandular puberulent branchlets and rachises, more widely spaced floral bracts, shorter arid thicker pedicels, larger fruits that are darker and purple tinged, mealy mesocarp and smooth endocarp. Arctostaphylos rainbowensis differs further from A. peninsularis in its ecological distribution; A. peninsularis is a species of the interior, distributed at elevations above 1200 m whereas A. rainbowensis is a low elevation coastal range species. Arctostaphylos rainbowensis is distinct from A. glandulosa in its diploid chromosome number, non-scabrous leaves, reduced floral bracts, and larger fruits that are round with a solid stone. It differs from A. glauca in having a burl, non-reflexd floral bracts, and smaller, non-viscid fruits. Arctostaphylos rainbowensis is restricted to approximately 275 km² in a region that is undergoing rapid development. In the last 20 years many of the populations have been extirpated, and the species needs legal protection. Arctostaphylos rainbowensis Keeley & Massihi, es una especie nueva de "manzanita" que desarrolla nudos, y que está distribu­­­ída desde el noroeste del Condado de San Diego hasta los límites del Condado de Riverside, en California. Esta especie ha sido referida como una población disjunta de A. peninsularis que ocurre en Baja California, o como un híbrido entre A. glandulosa y A. glauca. Un análisis componentes principio de 48 carácteres, revelaron que Arctostaphylos rainbowensis es distinta a los tres taxa anteriores. Lo se diferencia de A. peninsularis porque sus hojas son más grandes, el número de estomas en la superficie abaxial es casi el doble que en la adaxial, raquis y ramificaciones pulverulento-glanduloso, brácteas florales más cortas y separadas, con frutos más grandes y de color púrpura oscuro. Además, Arctostaphylos rainbowensis se distingue de A. peninsularis en su distribución ecológica, ya que A. peninsularis es una especie