Rothwell, Gar W. , Nixon, Kevin .
The overall pattern of fern phylogeny: a review and reevaluation.
Two recent approaches to broad-scale phylogenetic analyses of ferns have resulted in discordant hypotheses that imply radically different patterns of phylogeny for vascular plants. One hypothesis is based on the analysis of morphological characters for both living and extinct species, and resolves ferns as a polyphyletic assemblage of three clades. Living species form a clade that includes the eusporangiate Ophioglossales and Marattiales plus leptosporangiate ferns. Leptosporangiate ferns are recognized as having undergone three major radiations. The first radiation occurred in Carboniferous and comprises families that are all extinct. The second radiation extended from the Permian through the Early Cretaceous, resulting in the basal living families of Filicales plus the Hydropteridales. The third radiation extends from Cretaceous to the Recent, and has resulted in the most highly derived families of Filicales. The competing hypothesis utilizes both gene sequence and morphological characters, is based exclusively on living species, and resolves seed plants as the sister group to a clade that includes ferns, equisetophytes and psilotophytes (i.e., moniloforms of Kenrick and Crane). Several tests of these competing hypotheses were performed to assess the strength of each, including inclusion/exclusion of extinct species experiments, and separate analysis of individual genes and morphological characters to assess levels of character conflict. Results of these tests reveal that neither hypothesis is robust, and that it is premature to conclude that equisetophytes and psilotophytes are nested within a clade that includes all ferns.
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1 - Ohio University, Department of Environmental & Plant Biology, Porter Hall, Richland Avenue, Athens, Ohio, 45701-2979, USA
2 - Cornell University, LH Bailey Hortorium, 462 Mann Library, Ithaca, New York, 14853-4301, USA
Presentation Type: Oral Paper
Date: Monday, August 15th, 2005
Time: 8:45 AM