Preliminary Systematic Studies of the Oak Ferns: Chromatography and Electrophoresis

Abstract

The Oak Ferns, represented in the United States by Gymnocarpium dryopteris, G. robertianum, and their putative hybrid, have been placed in many different genera. Some authors have placed them in the genus Dryopteris, primarily on the basis of similarities in rachis characters and rhizome scaliness. Others have included them with the Beech Ferns (Phegopteris). The Beech Ferns and the Oak Ferns have in common an elongate creeping rhizome and exindusiate sori (Morton, 1950). Slosson placed them both in the cosmopolitan genus Thelypteris, along with the Marsh Ferns (Wherry, 1961, p. 64). Ching (1933) proposed that the Oak Ferns be regarded as a genus distinct from Phegopteris, and he redefined Gymnocarpium. Currently most workers appear to favor this interpretation; however, other combinations are frequently used, particularly in local and regional floras. Cytological studies have shown a similarity in chromosome size between the Oak Ferns and the Beech Ferns; however, the number differs. The base number of 40 is found in the Oak Ferns (Wagner, 1966). The Broad Beech Fern and the Long Beech Fern have numbers of 30 and 90, respectively (Britton, 1965; Manton, 1950, p. 184). True Dryopteris has a base number of 41 chromosomes (Walker, 1961; 1962). These chromosomes tend to be somewhat larger than those of either the Beech or the Oak Ferns. Chromosome numbers vary within the genus Thelypteris; however, none reported correspond with that of the Oak Ferns. In recent years paper chromatography has gained acceptance as a taxonomic method. Most of the studies have involved taxa at or below the species level. The works of Smith and Levin (1963), Alston and Turner (1963), and others have indicated chromatography to be of particular value in the confirmation of interspecific hybridization. Works with higher taxa have concerned primarily the distribution and occurrence of specific compounds (Kupchan et al. 1961; Mabry et al. 1963). Cellulose acetate electrophoresis has been used in animal taxonomy (Leviton et al. 1964). No reports were located of comparable comparative studies in plants, though immunoelectrophoresis studies have been done with various plant taxa (Gell et al. 1956). This study was undertaken to add further information concerning the status of the Oak Ferns by the consideration of biochemical characteristics, and to explore the value of paper chromatography and cellulose acetate electrophoresis in generic problems. Chromatographs and electrophoretographs of extracts from the Oak Ferns were compared with those of representatives of the Beech Ferns, the Marsh Ferns (Thelypteris), and the Wood Ferns (Dryopteris).