Flora of North America species comparison

One of the most abundant ferns in the western flora (rivaled only by Pteridium), Polystichum munitum also is of significant economic importance. Enormous quantities of leaves are gathered for backgrounds in funeral wreaths and other floral displays; the evergreen leaves keep well in cold storage and are exported to Europe. It is extensively used in landscaping, the trade being mainly in wild-collected plants.

Polystichum munitum appears to be most closely related to P. imbricans based on morphologic (D. H. Wagner 1979) and electrophoretic (P. S. Soltis et al. 1990) analyses. The chloroplast DNA of P. imbricans, however, is divergent (G. Yatskievych et al. 1988), suggesting a chloroplast origin independent of the nuclear genome. That Polystichum munitum is related to P. acrostichoides is supported by data from chloroplast DNA analysis (G. Yatskievych et al. 1988) but contradicted by data from electrophoretic studies (P. S. Soltis et al. 1990).

Polystichum munitum can be distinguished from P. imbricans by its persistent, wide (the largest wider than 1 mm) distal petiolar scales; such scales of P. imbricans are less than 1 mm wide and fall off early.

From an evolutionary standpoint, Polystichum munitum is a diploid progenitor of P. andersonii, P. californicum, P. setigerum, and, perhaps, P. scopulinum. Hybrids with all except P. setigerum have been reported, all triploid, attesting to its parental role in the tetraploids (see discussion under each). Hybrids with P. braunii (A. Sleep and T. Reichstein 1967), P. kruckebergii (P. S. Soltis et al. 1987), P. dudleyi (W. H. Wagner Jr. 1973), and P. lemmonii (P. S. Soltis et al. 1989) also have been reported.

The population on Guadalupe Island has been called Polystichum solitarium Maxon.

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

Polystichum kruckebergii is widely but sporadically distributed in small numbers in both the Sierra-Cascade and Rocky Mountain systems. Populations sometimes consist of only two or three dwarfed plants that are difficult to distinguish from P. scopulinum, with which they may occur. The spreading teeth of equal size at the pinna apex will usually distinguish this species. Polystichum kruckebergii is a tetraploid presumed to be of hybrid origin, with P. lonchitis and P. lemmonii as its diploid progenitors (W. H. Wagner Jr. 1973), although this hypothesis has not been confirmed. The hybrid with P. munitum has been found in Washington (P. S. Soltis et al. 1987) with both parents, and it is distinguished by intermediate morphology and abortive sporangia.

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