Pryer, Kathleen M. , Butler, Emily Y. , Farrar, Donald , Moran, Robbin , Schneller, Jakob J. , Schuettpelz, Eric , Watkins, Jr., James E. (Eddie) , Windham, Michael .
On the importance of portraying the plant life cycle accurately: ferns as a case study.
In 1967, eleven students enrolled in the first course on tropical ferns offered by a fledgling Organization for Tropical Studies (OTS). Forty-one years later, in January 2008, OTS offered a second course on tropical ferns, bringing 23 students from five countries together with six faculty members. For 15 days, this enthusiastic group reviewed various important aspects of tropical fern biology, including phylogenetics, identification, ecology, physiology, gametophyte form and diversity, hybridization, polyploidy, cytogenetics, and antheridiogen systems of fern gametophytes. One tenet of fern biology that immediately surfaced as being largely misleading was how the fern life cycle is portrayed. Almost universally, textbooks imply that homosporous ferns produce hermaphroditic, haploid gametophytes, which engage in self-fertilization—a scenario that would lead to completely homozygous sporophytes in sexual diploid species. This flawed interpretation of the fern life cycle has led to gross underestimates of genetic load and a host of unsupported hypotheses regarding polyploidy, homoeologous chromosome pairing, and “subsexual” genetic variability. This view of ferns as “intragametophytic selfers” (the most extreme form of inbreeding) has also contributed to the common belief that ferns are consummate long distance dispersers with almost no opportunity for genetic isolation by distance. Neither the textbook life cycle nor the genetic scenarios inferred from it are supported by empirical studies of ferns (or their 400 million year evolutionary history). To this end, we advance here a more accurate life cycle illustration for ferns—one reflecting their unique position in the green tree of life and hopefully one dispelling the notion that “telling it like it is” is somehow more difficult to teach or comprehend.
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1 - Duke University, Department of Biology, Durham, NC, 27708, USA
2 - University of Wisconsin-Madison, Department of Botany, 430 Lincoln Drive, Birge Hall, Madison, WI, 53706, USA
3 - Iowa State University, Department of Botany, Ames, Iowa, 50011, USA
4 - New York Botanical Garden, Institute of Systematic Botany, 200Th Street & Southern Boulevard, Bronx, New York, 10458-5126, USA
5 - University of Zurich, Institute of Systematic Botany, Zollikerstrasse 107, CH-8008 Zurich, Switzerland
6 - Harvard University, Arnold Arboretum, 16 Divinity Ave, Cambridge, MA, 02138, USA
fern life cycle
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 28th, 2008
Time: 2:00 PM