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Spontaneous Production of a Morphologically Distinct, Fertile Allopolyploid by a Sterile Diploid of Asplenium ebenoides
W. H. Wagner, Jr. and Robert S. Whitmire
Bulletin of the Torrey Botanical Club
Vol. 84, No. 2 (Mar. - Apr., 1957), pp. 79-89
Published by: Torrey Botanical Society
Stable URL: http://www.jstor.org/stable/2482783
Page Count: 11
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1. The hybrid fern, Asplenium ebenoides (A. platyneuron x A. rhizophyllum) occurs in nature as a sterile diploid over a wide range, and also as a fertile allopolyploid limited narrowly to Hale Co., Alabama. Asplenium ebenoides has been synthesized in culture, and has been backcrossed with A. platyneuron, but no new fertile allopolyploids have been heretofore produced under experimental conditions. 2. A new and distinctive allopolyploid form of A. ebenoides arose spontaneously in cultures produced by sowing large numbers of spores and sporangia from a sterile diploid form collected in Montgomery Co., Maryland. A total of about twenty-five gametophytes, appearing as clustered groups or as solitary individuals, was produced among thousands of spores. Fertilization among these gametophytes yielded a uniform type of sporophyte, resembling the sterile diploid progenitor. 3. The new allopolyploid differs from the wild Alabama type in a number of characters, including the blade texture, blade color, outline of leaf, breadth of leaf-segments, number of dwarfed segments, form of the segment margins, and the outline of the gametophytic wings. The new allopolyploid reproduces as readily from spores as does the wild type. 4. The rarity of allopolyploid populations of ferns in nature is briefly discussed, and a series of factors is suggested to account for it: (1) the small number of polyploid spores produced by the sterile diploid; (2) the necessity for the polyploid spores to fall in narrowly defined microhabitats; (3) competition with the gametophytes of normal species in the same habitat; and (4) a tendency for gametophytes to require cross-fertilization. 5. Because of the close resemblance of the allopolyploid to its sterile diploid progenitor and because of its morphological distinctness from the previously known allopolyploid from Alabama, the suggestion is made that varying forms of species of this evolutionary origin may be due to genetic differences between parental races in different localities.
Bulletin of the Torrey Botanical Club © 1957 Torrey Botanical Society