According to the mtDNA data of Rodriguez-Robles et al. (1999), the population of Lampropeltis zonata inhabiting the Santa Monica Mountain (currently classified as L. z. pulchra) is most closely related to mountain kingsnakes from the nearby San Gabriel Mountains, which are currently classified as L. z. parvirubra. That means this particular population of L. z. "pulchra" probably migrated westward from the San Gabriels, but not norhward from the Santa Ana Mountains. It is thus a descendant of L. z. parvirubra. Morphologically, the Santa Monica populations also resemble parvirubra more than they do the pulchra populations to the south, according to the subspecies account below. Therefore it would appear that the Santa Monica Mountain populations are probably L. z. parvirubra, not L. z. pulchra.

Reference
Rodriguez-Robles, J. et al. 1999. Phylogeography of the California mountain kingsnake, Lampropeltis zonata (Colubridae). Molecular Ecology 8: 1923–1934
L. z. pulchra subspecies account