From Gels to Genomics: The Evolving Landscape of Pteridology. A Celebration of Gerald Gastony's Contributions to Fern Evolutionary Biology
Haufler, Christopher H. .
Gels and Genetics: The historical impact of isozymes on paradigm shifts in hypotheses about fern evolutionary biology.
Although it is comforting when new discoveries confirm established hypotheses, it is positively exciting when novel techniques and observations demand rejection of reigning textbook concepts. In the 1970s, fern biologists were captivated by the logically consistent correlations drawn by Edward Klekowski that because homosporous ferns had potentially bisexual gametophytes and high chromosome numbers, they should be highly inbred and polyploid. Hypothesizing that polyploidy could adaptively buffer the homozygotizing effects of consistent inbreeding, Klekowski focused considerable new attention on fern genetics. Although some breeding experiments and chromosomal studies proved to be consistent with this hypothesis, central implications of it could not be addressed until enzyme electrophoresis provided a window on molecular genetics. Whereas the hypothesis predicted that ferns should have numerous duplicated genetic loci and be predominantly homozygous, isozymes demonstrated that species with generically basal chromosome numbers were genetically diploid and possessed numerous heterozygous loci. These discoveries required revised hypotheses and forced a revolution in modeling population-level phenomena for ferns. Mechanisms promoting outcrossing were explored and verified. Given a new starting point, fern polyploidy levels actually approximated those of other plant groups. No longer constrained by lethargic rates of change because of polygenic systems, it was reasonable to posit that diploid ferns could adapt and diversify along with their seed plant descendants. At the species level, migration via single spores became a specialized rather than a standard capacity for ferns. Fern biogeographers were required to consider a new variety of possible outcomes from dispersal and vicariance. Dismissing ferns as stagnant evolutionary dead-ends ceased to be an option, and with exciting new evidence from DNA and genomic studies, new vistas are opening all the time.
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1 - University of Kansas, Department of Ecology & Evolutionary Biology, Haworth Hall, 1200 Sunnyside Ave, Lawrence, Kansas, 66045-7534, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Room 5/Woodward
Date: Tuesday, July 29th, 2008
Time: 8:45 AM