Abstract Detail



Reticulate evolution and biogeography in ferns and lycophytes - a colloquium honoring Dr. David Barrington

Barrington, David [1].

Fifty years of fern hybridization and historical biogeography: new perceptions and new tools, all addressing the same fundamental questions.

Fifty years ago, inquiries into the course of evolution in the ferns were carried out without a repeatable approach to hypothesis testing, with the most primitive understanding of the nuclear genome, and with a pencil and paper instead of a computer. Rapid changes have ensued. Cladistic analysis provided us with a consistent approach to testing evolutionary hypotheses.  The revelations from sea-floor data about continental drift, brought to bear on J.D. Hooker’s approach of comparing geographic patterns across unrelated lineages, brought vicariance biogeography into vogue. A slower progress towards unveiling the patterns of genetic diversity in the chloroplast and nuclear genomes has nevertheless provided new datasets to use in inferring evolutionary history. All of these changes improved our understanding of nature and gave us powerful new tools. However, the fundamental questions that inform our passion for these plants—an understanding of the pattern of divergent evolution in the ferns and the role of hybridization, so common in the ferns, in complicating these patterns—remain the same. Thanks to Manton, we early took advantage chromosome number and pairing to develop the first strong hypotheses for reticulate histories (those involving hybridization, polyploidy, and apomixis). Werth’s inauguration of isozyme electrophoresis for the ferns presaged an epoch of new revelations in patterns of hybridization and reticulate evolution in the ferns. With the inauguration of DNA-based approaches by Stein in the latter part of the 1970s, we began to see the power of these data for phylogenetic analysis. Restriction-fragment analysis of chloroplast DNA data followed. In the early 1990s we turned to the DNA-sequencing techniques that became available in the ferns thanks to Hasebe and his group—now we had a large number of characters largely unencumbered by confusion about homology with which to build fern phylogenies. Our current phylogeny, a consensus reached by the entire international community of pteridologists, is grounded in these chloroplast DNA data. Wolf’s introduction of nuclear DNA sequence data in the mid 1990s added substantially to the arsenal of tools for testing hypotheses for reticulate evolution. The patterns of evidence emerging from these modern datasets analyzed with modern protocols using modern tools have reinvented the biogeography of ferns with the aid of modern tools for biogeographic analysis. These past few years have seen the layering of biogeographic data onto dated phylogenies with the result that questions about dispersal and vicariance have been addressed more powerfully than ever before.


1 - University Of Vermont, Plant Biology, 111 Jeffords Hall, 63 Carrigan Drive, Burlington, VT, 05405, United States

Keywords:
evolution
hybridization
ferns
History of Science.

Presentation Type: Colloquium Presentations
Number: 0014
Abstract ID:845
Candidate for Awards:None


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