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Seed plant phylogeny: demise of the anthophyte hypothesis?
Davis,M. C., N. Shubin, and E. B. Daeschler. 2004. A new specimen of (Sarcopterygii, Osteichthyes) from the Fammenian Catskill Formationof North America. Journal of Vertebrate Paleontology. 24:26-40.
New World species of do not contain significant amounts of ephedrine alkaloids. However, several nitrogenous secondary compound known to stimulate neuroactivity, like nonprotein amino acids with cyclopropyl ring structures and tryptophan derivatives, have been found in the stems of American , which might explain why the plant has been used so extensively in New and Old World traditional medicine. In at least one study, was found to contain traces of pseudoephedrine (Cavaney, 2001).
demise of the anthophyte hypothesis
Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.
Davis,M. C., N. Shubin, and E. B. Daeschler. 2001. Immature rhizodontids from theDevonian of North America. Bull. Mus. Comp. Zool. 156(1): 171-187.
and Demise of the Anthophyte Hypothesis.
DeLong,E. F. 1992. Archaea in coastal marine environments. Proceedings of The National Academy of Sciences.U.S.A. 89: 5685-5689. [L]
The gnepine hypothesis is a modification of the gnetifer hypothesis, and suggests that the gnetophytes belong within the conifers as a sister group to the . According to this hypothesis, the conifers as currently defined are not a monophyletic group, in contrast with molecular findings that support its monophyly.. All existing evidence for this hypothesis comes from molecular studies within the last decade. However, the morphological evidence remains difficult to reconcile with the gnepine hypothesis. If the gnetophytes are nested within conifers, they must have lost several shared derived characters of the conifers (or these characters must have evolved in parallel in the other conifer lineages): narrowly triangular leaves (gnetophytes have diverse leaf shapes), canals, a tiered , and flat woody ovuliferous scales..
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demise of the anthophyte hypothesis?".
Carmichael JS and Friedman WE (1996) Double fertilization in Gnetum gnemon (Gnetaceae): its bearing on the evolution of sexual reproduction within the Gnetales and the anthophyte clade. American Journal of Botany 83: 767–780.
demise of the anthophyte hypothesis…
Other studies examining ribosomal DNA support the conifers as a monophylitic clade (without Gnetales nested within), with the Gnetales being more genetically similar to the angiosperms (Rydin, 2002). The conflict is still not definitively resolved, and it could be possible that Gnetales are not very closely related to either angiosperms or conifers. Some believe that molecular data may not be able to completely resolve the question and that fossils need to be taken into account more to fill in the gaps in the hypotheses (Donoghue and Doyle 2000; Frohlich and Parker 2000). The following trees in Figure A show the two possible placements of Gnetales in evolutionary history.
“Demise of the anthophyte hypothesis?” Curr
Chaw SM, Parkinson CL, Cheng Y, Vincent TM and Palmer JD (2000) Seed plant phylogeny inferred from all three plant genomes: monophyly of extant gymnosperms and origin of Gnetales from conifers. Proceedings of the National Academy of Sciences of the USA 97: 4086–4091.
demise of the anthophyte hypothesis?
Mathews S (2009) Phylogenetic relationships among seed plants: persistent questions and the limits of molecular data. American Journal of Botany 96: 228–236.
Demise of the anthophyte hypothesis?
Rydin C, Pedersen KR and Friis EM (2004) On the evolutionary history of Ephedra: cretaceous fossils and extant molecules. Proceedings of the National Academy of Sciences 101: 16571–16576.
A., Seed plant phylogeny: Demise of the Anthophyte hypothesis
Burleigh JG and Mathews S (2004) Phylogenetic signal in nucleotide data from seed plants: implications for resolving the seed plant tree of life. American Journal of Botany 91: 1599–1613.
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