Flora of North America species comparison

Polystichum californicum is restricted to the Coast Ranges and the Sierra-Cascade axis. It is most abundant in the Coast Range north of San Francisco.

Polystichum californicum is an allopolyploid, the evolutionary roots of which include P. dudleyi as the 2-pinnate ancestor. Morphologic and ecological data indicate P. imbricans is ancestor to the northern forms and P. munitum is ancestor to southern forms, suggesting P. californicum is an amalgam of interfertile tetraploids with polyphyletic origins (D. H. Wagner 1979). Cytological analysis corroborates this (A. D. Callan 1972; W. H. Wagner Jr. 1973), but chloroplast DNA studies have detected only the involvement of P. imbricans in the ancestry of P. californicum (P. S. Soltis et al. 1991).

The more xeric, rock-inhabiting members of the complex (showing the parental influence of P. imbricans) occupy the northern half of the range whereas plants of more mesic habitats are found to the south. Hybrids with both P. dudleyi and P. munitum are found frequently, because these three species are often sympatric (W. H. Wagner 1973). The hybrid with P. dudleyi (a triploid) will key to that species. The hybrid with P. munitum resembles a less-incised form of P. californicum with aborted sporangia. Polystichum californicum × imbricans has been found only once, in Oregon (A. D. Callan 1972). Another hybrid that will key here, based on its overall appearance, is P. munitum × scopulinum. It lacks filiform microscales and also has malformed sporangia. Such a specimen was the basis of the report of Polystichum californicum in eastern Washington (C. L. Hitchcock et al. 1955–1969, vol. 1). The sterile diploid hybrid between P. dudleyi and P. munitum is indistinguishable from P. californicum except for aborted sporangia and chromosome number (W. H. Wagner Jr. 1973).

(Discussion copyrighted by Flora of North America; reprinted with permission.)