Gels and Genetics: The Historical Impact of Isozymes on Paradigm Shifts in Hypotheses About Fern Evolutionary Biology (2008 AFS Symposium Summary) (Report‪)‬

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. The history of genetics for homosporous ferns is an exemplar of how technical innovations and discoveries lead to significant modifications of our working models in biology. Homosporous ferns were originally placed in the mysterious group called the "cryptogams" because, unlike their "phanerogamic" cousins, their manner of breeding was hidden from obvious observation and investigation. Once botanists began culturing the gametophytes of ferns, their reproductive biology was revealed, and a method for conducting genetic experiments (crosses and progeny rearing) became available. The earliest studies of fern genetics were those of Lang (1923) and Anderson-Kotto (1931), who demonstrated that most ferns showed simple Mendelian inheritance of traits. In 1950, Irene Manton published her magnum opus, ushering in a new era of genetic and biosystematic research on seed-free plants. Manton's extensive survey demonstrated that most ferns had extraordinarily high chromosome numbers and that often what appeared to be polymorphic species were actually reticulate complexes of diploid species and their allopolyploid derivatives. This research helped to demonstrate the importance of including genetic aspects of species in understanding their origins and their population dynamics. In the 1970s, Edward Klekowski (1979) brought a renewed focus to fern genetics by developing logically consistent and compelling correlations and hypotheses about the evolutionary biology of homosporous vascular plants. Klekowski observed that because homosporous ferns had potentially bisexual gametophytes they should be highly inbred, and because these plants have high chromosome numbers, they should be polyploid. Klekowski further hypothesized that this polyploidy could represent an adaptive response that would buffer the homozygotizing effects of consistent inbreeding. Genetic variation stored among the several to many homoeologous genomes contained in polyploids could be released by non-homologous pairing mistakes during meiosis. Indeed, Hickok (e.g., 1978) provided evidence consistent with pairing between homoeologs. Klekowski's hypotheses were intriguing because if accurate they provided a different genetic system and different evolutionary trajectory for homosporous vascular plants.