Evidence of natural hybridization between
Arctostaphylos viscida and
A. canescens in southwestern Oregon was obtained from morphological studies of field populations. Hybridization occurs where populations
of
A. viscida and
A. canescens meet in areas where serpentine and nonserpentine soils abut. At these contacts,
A. viscida forms large populations only on serpentine and
A. canescens only on nonserpentine. Most of the indentifiable hybrids survive on either transitional or nonserpentine soils. The small
proportion that are found on serpentine are considered to be backcrosses to
A. viscida. The hybrid plants are similar to several putative species maintained in the standard floras, and it is suggested that these
no longer be given taxonomic recognition.
Based on a thesis submitted to Oregon State University in partial fulfillment of the requirements for the M.S. degree.
This work was done in the Department of Botany, Oregon State University, Corvallis.