Electrophoretic and Morphological Confirmation of Interspecific Hybridization between Polystichum kruckebergii and P. munitum

The genus Polystichum (Dryopteridaceae) comprises from 160 (Tryon & Tryon, 1982) to 175 (Copeland, 1947) species and is nearly worldwide in distribution. Substantial morphological diversity exists within Polystichum (Barrington, 1985), and considerable taxonomic confusion has characterized Polystichum since its description in 1799. Systematic problems in Polystichum stem largely from extensive hybridization and allopolyploidy (Knobloch, 1976; Tryon & Tryon, 1982; Mickel in Barrington, 1985; D. Wagner in Barrington, 1985; W. Wagner in Barrington, 1985), which tend to obscure species boundaries and make morphological comparisons difficult. Furthermore, the production of interspecific sterile hybrids has created additional taxonomic confusion (Manton, 1950; Nakaike, 1973; W. Wagner, 1973; Daigobo, 1974; D. Wagner, 1979). A prime example of the reticulate evolution typical of the genus (D. Wagner, 1979, in Barrington, 1985; W. Wagner in Barrington, 1985) is found in the Polystichum complex from western North America. This group consists of five diploid species, three once-pinnate (P. imbricans, P. lonchitis, and P. munitum) and two highly dissected (P. dudleyi and P. lemmonii). There are five tetraploids, P. andersonii, P. braunii, P. californicum, P. kruckebergii, and P. scopulinum; all but P. braunii incorporate various combinations of the diploid genomes discussed above (W. Wagner, 1973; D. Wagner, 1979). All of these species are restricted to western North America except P. braunii and P. lonchitis, which are circumboreal in distribution, and P. scopulinum, which also occurs sporadically in eastern North America. [Following D. Wagner (1979), P. lemmonii is considered distinct from the South American P. mohrioides.] Polystichum setigerum, reported to be a sexual hexaploid derived from P. munitum and P. braunii (D. Wagner, 1979), is also a member of this complex. Several sterile hybrids among these species have been reported from North America, including P. californicum x munitum (Callan, 1972; W. Wagner, 1973), P. braunii x munitum (Alverson, unpubl.), P. andersonii x munitum, P. californicum x dudleyi, P. dudleyi x munitum, P. lemmonii x munitum, P. lemmonii x scopulinum, and P. munitum x scopulinum (W. Wagner, 1973), and P. braunii x lonchitis in Europe (Sleep & Reichstein, 1967). In addition, P. braunii has hybridized with the eastern North American P. acrostichoides (Thompson & Coffin, 1940; Barrington, 1986), and hybrids between P. lonchitis and P. ac-